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Ensuring the integrity in clinching process
Abstract
Clinching is a mechanical joining method, especially for sheet metal parts. The process is perceived as being a simple method that is based on only the accurate movement of a punch into a die. During the process, sheet metals are deformed locally without the use of any additional elements. Precisely selected tools are a requirement for an acceptable joint. The two most frequently used geometries in clinching tools are round and square. When round tools are used, the joint has a uniform shear load capacity in all the horizontal directions. Many papers have been written on the clinching process itself, including the tool geometries, parameter optimisation, joint strengths, simulation and FE analysis of the process, but few articles discuss the significance of anticipatory maintenance or continuous follow-up while using clinching in a mass-production process. This paper points out several problems encountered in the long-term use of a clinching process. Both the lack of systematic maintenance and continuous follow-up are discussed. The significance of changes in the construction are also evaluated in this presentation that is based on a real case study. This paper also offers proposals for improvements.
... The main concern in clinching process is the quality of each single joint or continuous quality control as the clinching process is sensitive to all deviations, particularly in mass production. Varis [28] suggests that there are no unimportant observations and deviations, and that all changes to the clinching process affect the outcome. One of the important factors in the feasibility of joining sheet metals is the material. ...
... All of the clinching tool sets within the die must be set up to bottom simultaneously to produce consistent button dimensions for all of the joints. The maximum misalignment of a clinching tool was reported to be three degrees [28]. This process parameter has also never been investigated and the impact of misalignment on quality of joint is poorly understood, while it is argued by Abdul Ghafar, et al. [30] that the impact of misalignment on tool life is highly important. ...
... A significant force is required to complete the clinching process in sheet metals. Elastic deformation and deflection (which is typically restricted to a value of 0.6 mm.) occurs in the clinching machine structure due to the increased force [28]. As a result, the machine's deformed structure returns to its original position once the punch moves upward after the clinching process is complete. ...
NEED—The effect of dimensional variability of sheet thickness (tolerance) and tool misalignment is poorly understood for the clinching process. Finite element analysis (FEA) is valuable but requires a lot of and is difficult to verify in this situation due to the asymmetrical geometry and nonlinear plasticity. OBJECTIVE—The objective of this work was to determine the effect of thickness tolerance, tool misalignment and sheet placement (top vs. bottom) in the clinching process, by use of analogue modelling with plasticine. METHOD—Experiments used a scaled-up punch and die, with plasticine as the analogue. Thickness tolerances were represented by sheet thicknesses of 11 and 7 mm, 12 and 8 mm, 8 and 12 mm and 13 and 9 mm for upper and lower sheets, respectively. Two types of lubricant were tested between sheets: glycerine and silicone oil. Angular variability was also introduced. Measured parameters were interlock (also called undercut) and neck thickness. Analogue results for deformation were compared with microscopy of metal clinching. FINDINGS—The results reveal that the multiscale analogue model is an efficient tool for studying the effect of dimensional deviation on a clinch joint. Thickness tolerance showed a critical relationship with interlock, namely a reduction to about half that of the nominal, for both maximum and least material conditions. Increased angular misalignment also reduced the interlock. Compared with glycerine, silicone oil tests showed reduced interlock, possibly the result of a lower coefficient of friction. ORIGINALITY—This work demonstrates the usefulness of analogue modelling for exploring process variability in clinching. The results also show that significant effects for sheet placement are ductility, lubricant (friction), thickness of samples and tool misalignment.
... Furthermore, since the self-piercing riveting technology needs to penetrate the upper sheets, it is not suitable for joining thin sheets with low ductility and high hardness. The adhesive bonding technologies join the thin sheets with a special adhesive [10][11][12][13][14]. The adhesive bonding technologies can join the various sheet materials. ...
... Clinching technologies were used to join the sheets of Audi car bodies in 1985 [17]. Clinching technology can easily join similar and dissimilar sheet materials, which is pollution-free, energy-saving, and low-cost than other joining processes [3,[10][11][12]. There is no need for any auxiliary component in the clinching process because the clinching technology joining the sheet materials depends on its own plastic deformation. ...
... The protrusions on the clinched joint limit the application of clinching technology on certain functional surfaces. The formation of the joint depends on plastic deformation of the material, which makes the sheet materials with high hardness and low ductility unable to be clinched [11,12]. In order to improve the defects of clinched joints, some new clinching technologies have been developed. ...
Clinching technology has been widely applied in automobile assembly industries to join sheet materials of different thicknesses and properties. It does not require any auxiliary parts and only depends on the plastic deformation of materials themselves to form a joint. Furthermore, clinching tools that include the punch and the die are simpler than other thermal joining methods. However, the usability of the clinched joint is restricted by a low joining strength. In order to expand the application range of clinching technologies, researchers have conducted extensive researches on how to improve clinching technologies. In this article, the latest advances of clinching technologies are reviewed on the development of clinching tools and processes. The improved clinching processes including flat clinching, hole clinching, reshaping the clinched joint without a rivet, reshaped joint with a rivet, rivet clinching, rectangular clinching, dieless clinching, roller clinching, laser shock clinching, hydro-clinching, injection clinching, adhesive clinching, resistance spot clinching, friction-assisted clinching, and laser-assisted clinching are introduced. The advantages and disadvantages of different clinching technologies are proposed. In addition, some suggestions for the future development of clinching technology are given in this paper. The clinching technology is developing towards a hybrid joining technology with high strength, high stability, and high efficiency.
... Self-piercing riveting is a cold-forming process that uses a rivet to form a solid interlock between sheets under the action of a press. This is a method of joining sheets by mechanical interlock, which shares the same principle as mechanical clinching [7]. The joints produced by self-piercing riveting are very strong and can join various types of dissimilar mixed sheets [8]. ...
... A protrusion is present on the clinched joint. It is quite hard for the sheets with low ductility and high hardness to be clinched [7]. A crater is present on the clinched joint. ...
Clinching, which is a green joining process, has been widely used in the manufacturing industry as a method of joining lightweight sheets for automotive. The clinched joint is created by plastic deformation during the clinching process. It is suitable for joining the sheets of different properties and thicknesses. Simple tools, energy savings and low costs are the outstanding advantages of clinching technology. Recent research advances including tools and machines of hybrid clinching and modified clinching are reviewed in this paper from both tool and machine aspects. Novel methods of tool design and optimization are mentioned. The characteristics of clinching tools and machines are described. Some potential research areas for the clinching tools and machines are mentioned. In addition, it is suggested that future trends in clinching tools and machines are clinching tool simplification, and advanced clinching machines with faster forming speed, energy saving as well as more precise control.
... Further, no detailed reasoning was given to avoid counter piping or excessive stretching in the ideal clinching joint. 25 Clinching can further reduce the expenses involved in the die-making process by using a flat die. Low-cost advanced finite-element methods can be used to accurately analyze the joining process and predict the strength even for composite materials. ...
... The same was mentioned in the literature, however, without providing a detailed explanation. 23,25,52 By this relationship, for higher joint strength in lap-shear configuration, the FC and wrap angle between the sheets should be higher, which also implies that the joint interface should not contain any non-contacting gap. ...
Clinching is an economical sheet joining technique that does not require any consumables. Besides, after its usage, the joints can be recycled without much difficulty, making clinching one of the most sustainable and eco-friendly manufacturing processes and a topic of high research potential. In this work, the influence of surface roughness on the load-bearing capacity (strength) of joints made by the mechanical clinching method in cross-tensile and lap-shear configuration is explored. Additionally, a correlating mathematical model is established between the joint strength and its surface parameters, namely, friction coefficient and wrap angle, based on the belt friction phenomenon. This correlation also explains the generally observed higher strength in lap-shear configuration compared to cross-tensile in clinching joints. From the mathematical correlation, through friction by increasing the average surface roughness, it is possible to increase the strength of the joint. The quality of the thus produced joint is analyzed by cross-sectional examination and comparison with simulation results. Experimentally, it is shown that an increment of >50% in the joint strength is achieved in lap-shear configuration by modifying the surface roughness and increasing the friction coefficient at the joint interface. Further, the same surface modification does not significantly affect the strength in cross-tensile configuration.
... • Punch force-stroke deviation in the tolerance-band for automated process controls F Join < 0.5-2.0 kN at equal stroke position s punch (Self-pierce riveting and Clinching) [8,9]. • Acceptable joint material thickness deviation d thickness < 6.0% of nominal thickness t nominal (Clinching) and < 10.0% (Self-pierce riveting). ...
... An average deviation of 5.0 kN in the measured punch force curve all over the joining process results between these two steel grades. Reliable clinching process monitoring systems in automated productions require much smaller tolerance bands of 0.5 -2,0 kN to safely detect process faults [8,9]. Typical errors are false installed tools, broken or worn dies or punches, that have a major negative impact on the joining quality. ...
Mechanical joining processes, in particular joining by forming like self-pierce riveting or clinching, require homogenous material characteristics for reliable joint properties. Joining processes in production are called safe, when the estimated properties for each manufactured joint, e.g. strength, remain in predefined narrow boundaries. Thus, an automated process monitoring is possible. A key reliability factor in automated production are varying joining materials properties. In case of steel, the knowledge of mutually dependent manufacturing steps at the coil build-up are crucial: First, milling conditions, such as dressing grade, predetermine the mechanical strength and fracture strain of the later joint. Second, the structure of corrosion protection layer by electrolytic or hot-dip galvanizing combined with forming and corrosion protection lubricants define the gliding abilities at later joining processes. It was found that a high dependency exists between solidification behaviour as well as surface friction level of the joining material and the stability of the joining process and the load capacity of the joint. To achieve safe mechanical joining results, these mentioned material properties must be guaranteed precisely by production monitoring techniques at the coil manufacturing. These include among others, methods for the non-destructive testing of mechanical properties at different coil areas, as well as systems for monitoring surface conditions and layers. As the material properties are build up over several production steps, production data are digitally collected today, analysed under quality aspects and if necessary corrective measurements are set online in the production.
... 1 Introduction 2 The demands of lightweight laminated structures are emerging in shipping, maritime, and kitchenware industries because of their comprehensive performance in high relative strength, vibration absorption and corrosion resistance. In practical applications, steel to aluminum alloy laminate is receiving more attentions attributed to its wide applicability and cost-effectiveness. ...
... Traditionally, the aluminum alloy is bonded with steel by a few mechanical approaches, like self-piercing riveting and clinching processes [1,2]. Nevertheless, these mechanical methods [3] are often limited by the thickness of metallic sheet and the ductility. ...
The widely investigated Al/steel laminated structures are challenged with subsequent plastic deformation due to the existence of interfacial brittle intermetallic compound layer. To overcome this drawback, a newly proposed thermomechanical forming technology as friction stir assisted double-sided incremental plastic forming with synchronous solid-state interfacial bonding is utilized to fabricate laminated structures, which can meet requirement of plastic deformation of laminates. Typical interfacial bonding performances produced by a series of experiments classified as sound bonding, de-bonding, over-thinning, penetration and crack are assessed. Local working peak temperature and maximum forming force in loading area are recorded and evaluated during stable bonding-forming stage. Considering heat-force coupling effect, a pressure-strain-temperature based prediction model is modified to assess process quality, which is conformed to experimental results. This work can help obtain proper process window to fabricate Al/steel laminated parts and shall also inspire to build guidance of related thermomechanical joining-with-forming processes to achieve high interfacial performance.
... However, the investigation about predicting fracture of materials in actual mechanical clinching is still lacking. Lee et al. [60] have investigated the effect of [55]. The mechanical clinching can be divided into four steps: material positioning, drawing, upsetting and geometrical interlocking. ...
... It also has been used to join dissimilar materials [42,[48][49][50][51]. Mechanical clinching is known as an economical joining method for sheet parts due to its low cost in investment and operation [52]. The mechanical clinching facility consists of a simple pneumatic press system and insertable punch and die set [53,54], as shown in Figure 2. [55]. The mechanical clinching can be divided into four steps: material positioning, drawing, upsetting and geometrical interlocking. ...
Multi-materials of metal-polymer and metal-composite hybrid structures (MMHSs) are highly demanded in several fields including land, air and sea transportation, infrastructure construction, and healthcare. The adoption of MMHSs in transportation industries represents a pivotal opportunity to reduce the product’s weight without compromising structural performance. This enables a dramatic reduction in fuel consumption for vehicles driven by internal combustion engines as well as an increase in fuel efficiency for electric vehicles. The main challenge for manufacturing MMHSs lies in the lack of robust joining solutions. Conventional joining processes, e.g., mechanical fastening and adhesive bonding involve several issues. Several emerging technologies have been developed for MMHSs’ manufacturing. Different from recently published review articles where the focus is only on specific categories of joining processes, this review is aimed at providing a broader and systematic view of the emerging opportunities for hybrid thin-walled structure manufacturing. The present review paper discusses the main limitations of conventional joining processes and describes the joining mechanisms, the main differences, advantages, and limitations of new joining processes. Three reference clusters were identified: fast mechanical joining processes, thermomechanical interlocking processes, and thermomechanical joining processes. This new classification is aimed at providing a compass to better orient within the broad horizon of new joining processes for MMHSs with an outlook for future trends.
... Further, no detailed reasoning was given to avoid counter piping or excessive stretching in the ideal clinching joint. 25 Clinching can further reduce the expenses involved in the die-making process by using a flat die. Low-cost advanced finite-element methods can be used to accurately analyze the joining process and predict the strength even for composite materials. ...
... The same was mentioned in the literature, however, without providing a detailed explanation. 23,25,52 By this relationship, for higher joint strength in lap-shear configuration, the FC and wrap angle between the sheets should be higher, which also implies that the joint interface should not contain any non-contacting gap. ...
Clinching is a mechanical sheet metal joining method in which the sheets are geometrically interlocked using, punch and die, tools without any consumables. In this work, to improve the clinching joint strength in lap shear configuration, the base sheet material is heat-treated in a furnace over varying time durations and temperatures to improve the ductility. Ductility is the prime factor in deciding the amount of cold roll bonding (CRB). This CRB helps during the joining of heat-treated sample to eliminating the gap at the “S” interlock and increase in friction, otherwise the gap would be present in the untreated material. This elimination of gap and higher friction is necessary for the identified belt friction mechanism operating at the lap shear configuration to produce higher joint strength. These causes are confirmed by examining SEM images of the cross sections of the joint and fractography of the failed joint interface. The joints so formed are tested for its strength in monotonic lap-shear configuration loading. Experimentally it is observed that the heat-treatment of base sheets improves the strength in this configuration by more than 50% compared to the untreated material.
... Die relevante Kenngröße für die Kopf zugfestigkeit einer Clinchverbindung ist der Hinterschnitt[65]. Beide Verbindungsparameter, Hinterschnitt sowie Halsdicke, können ausschließlich zerstörend über das Anfertigen eines Schliffbildes vermessen werden[66]. Das zerstörungsfreie Prüfkriterium für Clinchverbin dungen ist die Restbodendicke[66].Anhand dieser Kenngröße kann der Stempelweg bzw. ...
... Beide Verbindungsparameter, Hinterschnitt sowie Halsdicke, können ausschließlich zerstörend über das Anfertigen eines Schliffbildes vermessen werden[66]. Das zerstörungsfreie Prüfkriterium für Clinchverbin dungen ist die Restbodendicke[66].Anhand dieser Kenngröße kann der Stempelweg bzw. die Fügekraft beim Clinchen sichergestellt werden. ...
Die mechanischen Fügetechnologien stoßen zunehmend an ihre Verfahrensgrenzen, wenn es um das Verbinden von Aluminiumblechlegierungen mit höchstfesten Stahlwerkstoffen geht. Im Rahmen dieser Arbeit wurde das Schneidclinchen zur Erweiterung der Verfahrensgrenzen mechanischer Fügetechnologien für das Verbinden höchstfester Stahlgüten in Mischbauweise entwickelt. In Abgrenzung zu den bisherigen Fügeverfahren kommt diese Technologie ohne Fügeelemente aus und es sind keine zusätzlichen Prozessschritte zur Bauteilvorbereitung, wie Vorlochoperationen, notwendig. Die numerischen und experimentellen Untersuchungen dieser Arbeit schaffen ein grundlegendes Prozessverständnis zum Funktionsprinzip und zum Einsatzpotential des Schneidclinchens.
... Numerical simulation gradually turns into main research method of clinch joining process. Varis [25] found that the mechanical strength of clinch joining joints relies on the interlock and the neck using FEA. Paula et al. [26] investigated the tool geometry effects on both the neck and interlock with respective qualitative analysis on certain geometrical feature by numerical simulation. ...
... h depth of bottom die resolves the shearing rate of upper sheet which eventually influences neck. Interlock has some affiliations with tensile force to a certain extent, which is the same with [25], because the dominated parameters such as X, h, L1, and L2 seem to have similar effects on these two responses. X bottom thickness is one of the most important process parameters, which decides the total compressibility of two sheets and influences the tensile force, which is similar to [3]. ...
Clinch joining is a complexed mechanical behavior influenced by both process parameters and geometry parameters. The present clinch joining optimizations are more dedicated on geometry parameters, and except some property objectives of optimization, the other design properties of clinching process are not considered as constrained conditions. Therefore, the multiobjective optimization in the paper takes clinching process parameters such as punch speed, bottom thickness, and blank holder force into consideration besides geometry parameters, and then sets two thinning rates as constrained conditions. In the paper, a sufficient and systemic procedure for high-quality clinched joint based on FEA (finite element analysis), PS (parameter study), RSM (response surface methodology), and NSGA-II (non-dominated sorting genetic algorithm-II) is developed. Parameter study is conducted to choose significant parameters from both process and geometric parameters for neck, interlock, and tensile force. Then, mathematical models of nine selected parameters with responses are built based on RSM, and the interactions on interlock and tensile force are clearly identified by the model. Finally, three objectives neck, interlock, and tensile force and two constraints thinning rates of side face of joint are applied on multiobjective optimization using NSGA-II, which could obtain comprehensive high-quality joint, and the Pareto sets reveal negative relations of both tensile force to neck and interlock to neck, as well as the positive relation between interlock and tensile force. The result shows that the presented procedure performs well in optimization of clinch joining process and the use of finite element simulation model is valuable for complex optimization design.
... This process produces a significant alteration on both sides of the connection (protrusions, defects, etc.). Mechanical clinching [23] and self-pierce riveting [24] can be included in this category of processing. (ii) Thermomechanical interlocking: the joining is mainly developed through micromechanical interlocking and high thermoplastic deformation of both parts. ...
A laser scanning strategy for fabricating deep surface grooves using a continuous-wave fiber laser was investigated in this study. Because the low productivity of short-pulsed-wave lasers limits their application to a small scale, a continuous-wave (CW) fiber laser that can provide a high power density was used for the rapid fabrication of deep grooves. An innovative tailored laser scanning strategy of fabricating patterned deep grooves was analytically designed based on the power density and interaction time. Considering the thermophysical properties of the material, controlled laser processing parameters were determined for fabricating surface grooves with rectangular and chevron cross-sectional patterns. To confirm the usefulness of the research results, the scanning strategy obtained in this study was applied for achieving high-quality joining between injection-molded metal–plastic hybrids (MPHs). A deep-surface-grooved A5052 aluminum alloy sheet was bonded to two plastics, polyamide and polypropylene, via injection molding. Lap shear tensile tests of the MPHs revealed their significantly enhanced joining strength owing to a better mechanical interlocking of the groove. The developed laser scanning strategy using a CW fiber laser can be widely applied in the fabrication of deep grooves of various cross-sections with high reliability.
... Clinching or micro-clinching is a mechanical interlocking mechanism of sheet metal parts typically from 0.2 mm to 4 mm thick that has been applied for Al-Cu joining applications [16]. The clinching-based mechanical interlock (i.e., local surface deformation without use of any additional joining elements) is created at ambient temperature by using a conventional tooling set (a punch and a die) [17]. While clinching is a simple technique for cold point joining of similar and dissimilar metal sheets, clinch joints are prone to becoming loose under vibration, elevated temperature, moisture infiltration, and so on, which results in force reduction in the joint, increase in clinched electrical contact resistance and eventual failure of the interconnect [18]. ...
Battery manufacturing involves a large number of individual cells arranged in modules configured within a battery pack and connected either in series and/or parallel to deliver the required power and driving range. Cells within a module are linked using a tab-to-busbar connection as the electrical interconnect. Therefore, a battery pack contains a plurality of tab-to-busbar joints, and each must provide low electrical resistivity connection to minimize losses that may reduce the effective performance of the battery. In this work, the Dual Flow Cold Spray (DFCS) process, a modification of low-pressure cold spraying, was used to form low resistivity Cu+10%Zn and Al+10% Zn tab-to-busbar interconnects. As test coupons, 0.8 mm thick copper (Cu) was used to represent the busbar while 0.3 mm thick aluminum and nickel coated copper foils represented the respective electrode tabs. Low resistivity joint interconnects (≈100 μΩ) with high adhesion strength (≈120 MPa) have been formed. The influence of busbar surface preprocessing on the resistivity of the tab-to-busbar joints has been studied.
... The destructive single lap shear test is the most common laboratory test to evaluate the mechanical behavior of clinched joints (Varis and Lepistö, 2003). The shear strength of a clinched joint is directly related to the neck thickness, punch radius, and ultimate shear stress of the upper sheet metal (Coppieters et al., 2011;Peng et al., 2022;Ren et al., 2022;Varis, 2006). Once failure has occurred, the failure mechanism of the clinched joint can be investigated from both micro and macro perspectives (Qin and Chen, 2022). ...
Clinching is a reliable, high-speed, cost-effective, and environmentally friendly mechanical joining process that enables sheet metals to be joined in large scale productions including whiteware, ventilation and air conditioning systems and automotive applications. Currently, the mechanical behavior and durability of clinch joints under different thermal conditions is poorly understood. This study evaluates the mechanical performance of clinched joints at room temperature, 100 °C and 250 °C experimentally using uniaxial shear tests. Results revealed that all clinched specimens had a similar shaped load displacement curve. Four stages were observed: an initial linear behavior with low sensitivity to temperature; a force plateau caused by necking (the force was only moderately reduced for higher temperatures); a phase where the neck began to crack, resulting in a letdown of the load which showed high thermal dependence, and a final phase of tearing completely through the neck, with joint separation. The ultimate tensile shear strength of the joints was relatively unchanged by increases in temperature. At higher temperatures the stiffness and energy absorbed by the joint decreases. This work shows the results of thermal shear testing for clinched joints, and describes the mechanisms whereby the joint progressively collapses under load.
... By means of the applied method, different user or production defects could be detected with relatively high certainty in the load-stroke curve. In [17], a very similar way describes potential sources of error in production as well as process monitoring for the clinching process. In [18], the effect of tool eccentricity on the joint strength in clinching process was experimental investigated by offsetting the center line between die and punch . ...
Mechanical joining techniques like clinching are standard joining techniques for processing aluminum and steel alloys in the automotive car body manufacturing. When using conventional methods, joints will have a high quality after a finally tool check on a specific joining press system. However, if the press system during manufacturing will changed, it can occur that joints get other quality values e.g. smaller interlock. The reason for that has multiple influences,this paper considers especially the press-sided ones. With optical measurements of press deformation and punch speed during real joining processes, new 3D-halfsymmetric simulation models were built up, which take into account of press-side behavior such as joining velocity and angular as well as lateral misalignment of the joining tools during clinching process. Sensitivity analyses identifies significant influencing variables. On the base of this, equations of quality changes can be determined. Finally, this allows better prediction of the modification about joint quality after a press change from system A to B or C during manufacturing.
... The joints with a good strength should have adequate interlock, neck, and bottom thicknesses [22]. Figures 10 and 11 show the cross-sectional profile of the joints with two sheet thicknesses at three die depths and five bottom thickness/sheet thickness ratios, and the definition of A-A and B-B is shown in Figure 6. ...
The clinching process is widely used in joining lightweight sheet metal. We proposed a novel rotated clinching process (RCP), which is characterized by a flat bottom die structure and twin rotating punches. The aim of this study was to evaluate the strength of RCP joints. Al1060 sheets with thicknesses of 1.5 mm and 2 mm were used as the experimental materials. Overlap and T-lap RCP joints with three die depths and five bottom thicknesses were fabricated, and shear and peel tests were performed on the joints. The joint strengths were evaluated based on the mechanical load, cross-sectional profile dimensions, and failure mode. The results showed that the mechanical load is a direct, reliable, and quantitative evaluation criterion, while the cross-sectional profile and failure mode are indirect and qualitative. These criteria confirmed that the strength of thick sheet joints is higher than that of thin sheet joints, the shear strength is superior to the peel strength, and the strengths of the joints are high with failure mainly occurring due to tearing or shear failure. Finally, the key parameters for determining the strength of a joint include the bottom thickness/sheet thickness ratio (Rt), and the die depth (h).
... In the case of unbuttoning, the size of the interlock determines the pull-out strength. [6] The influence of the forming history, work hardening and sheet thickness reduction on clinched joints is described in [3] and [7]. The investigations show that the pre-forming of the sheets before the joining operation changes the geometry and thus the pull-out and shear strength of the clinched joint. ...
The components of a body in white consist of many individual thin-walled sheet metal parts, which usually are manufactured in deep-drawing processes. In general, the conditions in a deep-drawing process change due to changing tribology conditions, varying degrees of spring back, or scattering material properties in the sheet blanks, which affects the resulting pre-strain. Mechanical joining processes, especially clinching, are influenced by these process-related pre-strains. The final geometric shape of a clinched joint is affected to a significant level by the prior material deformation when joining with constant process parameters. That leads to a change in the stiffness and force transmission in the clinched joint due to the different geometric dimensions, such as interlock, neck thickness and bottom thickness, which directly affect the load bearing capacity. Here, the influence of the pre-straining in the deep drawing process on the force distribution in clinch points in an automotive assembly is investigated by finite-element models numerically. In further studies, the results are implemented in an optimization tool for designing clinched components. The methodology starts with a pre-straining of metal sheets. This step is followed by 2D rotationally symmetric forming simulations of the joining process. The resulting mesh of each forming simulation is rotated and 3D models are obtained. The clinched joint solid model with pre-strains is used further to determine the joint stiffnesses. With the simulation of the same test set-up with an equivalent point-connector model, the equivalent stiffness for each pre-strain combination is determined. Simulations are performed on a clinched component to assess the influence of pre-strain and sheet thinning on the clinched joint loadings by using the equivalent stiffnesses. The investigations clearly show that for the selected component, the loadings at the clinch points are dependent on the sheet thinning and the stiffnesses due to pre-strain. The magnitude of the influence varies depending on the quantity considered. For example, the shear force is more sensitive to the joint stiffness than to the sheet thinning.
... The process has several advantages such as no requirement for surface preparation or pre-drilled holes, low process time, reduced weight, and lower cost per joint. This process has a limitation however on joining high-strength aluminum alloys, as localized stress zones are generated which affect the fatigue performance of the joint [8]. ...
Increasing awareness of the global warming effects of greenhouse gas emissions has caused governments to impose strict regulations requiring significant improvements in vehicles’ fuel economy. These regulations have required automotive manufacturers to revise traditional designs. An effective method of improving fuel economy is through lightweighting, which can be achieved by incorporating multi-material designs. However, this method presents difficulty in manufacturing since traditional joining methods, such as resistance spot welding, cannot in many cases be directly used.
Many advanced joining methods have recently been developed to enable multi-material joining. Friction element welding (FEW) is one such process which can join aluminum sheets to steel without any required pre-hole drilling. In this process, the fastener is rotated and driven into the aluminum sheet, producing frictional heat which causes the aluminum to flow around the fastener shaft. In a successful joint, this aluminum flow remains near the shaft of the element and is covered by the element’s head upon welding. However, when joining high-strength aluminum alloys, the flow is hindered and aluminum protrusions are formed which extend beyond the cover of the element’s head. These protrusions, termed chips, are known to increase corrosion and should be eliminated. A novel method of reducing this effect is explored which utilizes modified elements to increase friction between the element and the aluminum sheet, causing accelerated heating. Additionally, a modified tip design is tested which aims to cut through the aluminum sheet. These methods were found to reduce chipping; however, chipping could not be eliminated. It was concluded that this is not a viable method of addressing the chipping issue in FEW.
... The process offers several advantages including shorter process times, low cost per joint, no requirement of surface preparation or pre-drilled holes, and relatively high robustness. However, it develops localized stresses while joining high strength aluminum alloys [13]. ...
Within manufacturing, resistance spot welding (RSW) has been the traditional method of choice when joining steel-steel sheets. However, within the transportation industry, the use of lighter weight materials such as aluminum has become necessary in order to improve fuel economy. This has required the creation of new technologies and adaptations of traditional ones in order to successfully join these materials.
One such adaptation, useful in joining aluminum-aluminum sheets, is friction element riveting (FER). This process is similar to the friction element welding process; however, two or more aluminum sheets are secured together between the element head and a relatively small steel sheet, which is termed lower element. Since this is a novel technology, the influence of different sized lower elements is unknown. A study is conducted which varies the diameter and thickness of the lower elements. A simulation was also created to estimate the thermal effects of these various geometries. Strength testing was used to determine the success of each parameter. It was discovered that the maximum joint strength occurs when using a lower element diameter of 25 mm and a thickness of 1.6 mm.
... In practical applications, various steel to aluminum alloy laminated sheets are receiving more attentions attributed to their wide applicability and cost-effectiveness. Traditionally, the aluminum alloy is bonded to steel by a few mechanical approaches, like self-piercing riveting and clinching processes [1,2]. Nevertheless, these mechanical methods are often limited by the thickness of metallic sheets and the ductility [3]. ...
The widely investigated Al/steel laminated structures are challenged with subsequent plastic deformation due to the prone generation of interfacial brittle intermetallic compound layer. To overcome this drawback, a recently proposed thermomechanical forming technology as friction stir–assisted double-sided incremental plastic forming with synchronous solid-state interfacial bonding is utilized to fabricate Al/steel laminated structures. Typical interfacial bonding-forming performances produced by a series of experiments classified as sound bonding, de-bonding, over-thinning, penetration and crack are individually assessed. Local working peak temperature and maximum forming force in loading area are recorded and evaluated during stable bonding-forming stage. Considering the heat-force coupling effect, a pressure-strain-temperature–based prediction model is modified to assess interfacial quality, which is conformed to experimental results. This work can help obtain proper process window to successfully fabricate Al/steel laminated parts and shall also inspire to build guidance of related thermomechanical joining-with-forming processes to achieve high interfacial performance.
... The joint connection requires no finishing. Fig. 1 Single-step clinching without cutting [4]. ...
Clinching is one of the important new joining techniques, in which two plate metal parts are locally plastically deformed by mechanical interlock. Clinching is a mechanical joining method by using simple tools that consist of a punch, a die, and a blank-holder. The shapes of these tools are the most important parameters that control the final geometry of the clinch joints which in turn strongly affect the strength and quality of the final joint. In this study, finite element simulations are carried out to investigate some of the difficulties regarding the optimization of the process parameters, and major expected geometric parameters that will influence the strength, joinability, and the quality of the joint.
... This mode was observed when there was a little difference between the interlocking strength and the strength of the thinnest created neck. The aforesaid modes have been depicted in Figure 2. The maximum strength of the joints was reported when the hybrid mode, i.e. a combination of shear and tensile failure, was seen [23][24][25][26]. ...
The mechanical clinching as an alternative joining process for fabricating lightweight aluminum to steel assemblies may face the challenges when joining low-ductility aluminum alloy to high-strength steel. Several researches have been focused on applying the electrically-assisted processes in various fields due to energy efficiency as well as practical simplicity, in order to improve the formability. This paper concentrates on the electrically-assisted mechanical clinching (EAMC) of AA6061-T6 aluminum to galvanized DP590 steel. To this end, a combination of experimental and numerical clinching tests was performed using extensible die at different penetration depths, in which controlling the material flow was obtained by applying newly defined chamfer ratio R C in order to guarantee the strong mechanical interlock. The joint section parameters, failure loads, and failure modes were measured. The effects of the geometrical features on material flow and mechanical strength of clinched joints were analyzed using a FE model. The results showed that the defined parameter R C greatly increased the strength with the use of the EAMC process, which came with a reduction in forming load.
... Joining approaches can be divided into mechanical joining, chemical joining, fusion welding, and solid-state welding methods [17]. Mechanical joining methods include conventional rivets, threaded fasteners, bolted joints, flow drill screws [18], clinching [19], friction-stir blind riveting [20], self-piercing riveting [21], hemming [22], etc. Chemical joining approach generally refers to adhesive joining [23]. ...
We survey various state-of-the-art methods for welding magnesium alloys and steels using different joint configurations. Microstructural characterizations indicate that four microstructures may form at the Mg/steel interface after welding: unwelded gap, metal oxides, solid solutions, or intermetallic compounds. Reaction products at the Mg/steel interface vary with different welding methods, alloying elements in base materials, interlayers or coatings applied, and preparations of base material before welding. Mechanical property characterizations, (a) lap tensile shear testing for lap-welded and spot-welded joints, (b) tensile testing for butt-welded joints and (c) fatigue properties of lap-welded and spot-welded joints are summarized and compared, separately. Reaction products at the Mg/steel interface are correlated with mechanical properties. Finally, ways to enhance Mg/steel joint strength, such as introducing interlocking features during friction stir lap and butt welding, are discussed.
... Varis [10] identified and characterized three failure modes in clinched joints under mechanical loading, and indicated that the failure mode is mainly determined by the geometry. The first mode is fracture in the neck of the joint due to insufficient neck thickness H which is the result of large tool diameter or small die depth in clinching process. ...
The rate dependent mechanical response of a clinched joint was investigated experimentally and numerically in this paper. Two different types of metal sheets, steel DX51D + Z and aluminum alloy 5182-O, were used to fabricate the hybrid clinched joint samples. Both the quasi-static and the low-speed impact tests of the clinched joint were performed with coach-peel and lap-shear coupons, respectively. Influences of loading rate on the global force vs. displacement response and the failure mode of the joint were experimentally analyzed. A detailed finite element model of the joint was built and comparative simulations were carried out to identify the effect of joining process on the subsequent mechanical performance. Furthermore, the influence of strain-rate sensitivities from the base metals on the global rate-dependence of the joint response was evaluated based on observation of local stress and strain evolution. The results indicate that the strain hardening of base metals induced by the joining process is vital in numerically predicting both the static and the dynamic strength of the clinched joint. Compared to coach-peel, the local deformation mode in lap-shear better enhances the contribution of strain-rate effect from the steel side to the dynamic strength of the hybrid clinched joint.
... For example, Das, et al. [2] have identified the suitable joining methods for cylindrical cell based battery pack building of which laser welding, micro-TIG welding and ultrasonic wedge bonding are the preferred joining methods. As dissimilar thin material joining is one of the key requirements for battery joining applications, several joining techniques are adopted to make satisfactory dissimilar interconnects, including ultrasonic metal welding [4], [5], ultrasonic wedge bonding [6], resistance spot welding [7], [8], soldering [9], micro-TIG welding [7], [10], micro-clinching [11] or laser welding [12]. Among these joining methods, laser welding provides several advantages over other joining methods including easy automation, contactless one-sided joining, high throughput, less heat input etc. ...
An automotive battery pack used in electric vehicle (EV) comprises several hundred to a few thousand of individual Lithium-ion (Li-ion) cells when cylindrical cells are used to build the battery pack. These cells are connected in series and/or parallel to deliver the required power and capacity to achieve the designed vehicle driving range. This triggers the need for suitable joining methods capable of providing mechanical strength together with the required electrical and thermal performances. A range of joining techniques are currently employed to connect large numbers of cells, and of these, laser welding is estimated to be the one of most efficient methods. Typically, the cylindrical cell casing is made of electrical grade steel which is electrically connected to copper tabs representing the cylindrical cell terminal to tab interconnect within the battery pack assembly. This study focuses on identifying the effect of laser welding process parameters on the mechanical, electrical and thermal responses of the laser welded joints produced using a 150 W Quasi-CW IR laser. Mechanical strength is assessed by evaluating the lap shear strength of the joint whereas the electrical and thermal responses are captured using voltage sensors and a thermal imaging camera respectively. It was observed that mechanical strength of the joint is highly correlated with electrical resistance and corresponding temperature raise at the joint. Furthermore, the optical micrographs reveal the microstructural characteristics of the joint.
... Weight reduction is achieved by clinching, where interlocks are performed without the requirements of any external element to join the parts (He, 2017). Materials characterized by high ductility are more suitable for this type of connections (Varis, 2006). The feasibility of the clinching process to join aluminum and PMC thin sheets has been already proved (Lambiase and Ko, 2016). ...
The industrial production must be driven forward by a leading idea, which aspires to prevent pollution and to reduce the carbon emissions. A greener future is motivating the technological progresses. The key word is sustainability protecting the environment of the future by low impact solutions.
In manufacturing, this has been resulting in process optimization to guarantee the quality and safety standards of the parts exhibiting an as low as possible environmental impact. The introduction of new materials and their combination is one of the strategies that has been pursued. In this context, the joints between dissimilar parts are important affecting the weight, the mechanical properties and the production costs of the manufactured structures.
In the proposed research, the primary joining categories (i.e. mechanical, thermal and chemical processes) have been analysed assessing their environmental consequences in the engineering of hybrid structures. Specifically, components manufactured by the combination of polymer matrix composites (PMC) and metals (lightweight alloys) are the analysed hybrid solutions. These result in a weight saving without being forced to reduce the performances or to increase the production costs of the parts. Joining solutions that can connect PMC and lightweight alloys have been, therefore, considered in the performed comparison. The energy consumption and CO2 emissions of the investigated processes, being equal the bearing strength for each of them, have shown a better environmental impact of the mechanical fastening performed by bolts. Currently, this is the only solution, which allows part disassembling. However, the recycling of hybrid components is a new requirement and new dismantling strategies can be developed. For this reason, the study has been extended taking the components down for whatever investigated joining solution. Hence, adhesive bonding and ultrasonic spot welding become environmentally-friendly as well.
... One of the advantages of joining processes of these kinds does not accompany thermal or chemical manipulation of the joining materials, allowing the joining of dissimilar materials without causing incompatibility issue between the different material One-sided access, joint set with deformation due to friction generated while rotation of the screw; (c) Impact nails: One-sided access, with ridges on the nail shank, inserted by specific gun with high speed; (d) Clinching: Two-sided access, with stamping tool stamping to form an interlock without any fasteners inserted. [13,14,15,16] characteristics with high shear and tensile strength. However, there are limitations and challenges, such as the possibility of excessive material damage during the joining process and weight addition due to the fasteners themselves. ...
Multi-Material Joining Design Explorer is discussed in this paper, which is a knowledge-based advisory system to help structural designers at the early design phase to select the potential joining methods. Data mining on various joining methods was conducted from any available sources, such as experts from academia and industry, handbooks, and vendors. Collected data was organized in a concept map which is an informal way of representing the data structure. The data were arranged into several categories according to their characteristics which include joinable materials, mechanical and design requirements, geometry, and so on. Common parameters and unique parameters were extracted from deep investigation of the gathered data to create a formalized data structure. A database using a general tree structure was then created to be fed into the advisory system. Searching algorithm using SQL query was implemented to navigate through the database to find the joining methods that match the requirements defined by the user. Two test cases were generated to validate the function of the knowledge-based system.
... Clinching has rapidly developed into a new type of mechanical joining technique, used in the automotive and aerospace industries, over the last thirty years [7,8]. The failure mode of clinched joints determined by tensile-shear tests, and the influence of clinching-process parameters on joints, were studied by Varis [9,10]. Oudjene et al. [11,12] improved the strength of clinched joints by changing the geometrical shape, and also optimised die parameters by using the least square method and the response surface analysis. ...
Clinch-bonded hybrid joining technology has been applied increasingly in different manufacturing disciplines. In this study, specimens of both similar and dissimilar sheets of H62 copper alloy, aluminium alloy and galvanised steel sheets were prepared in single-lap and T-joints. Tensile-shear tests and peeling tests were carried out for studying the load-bearing capacity and energy absorption of different clinch-bonded hybrid joints. The failure fractures were studied by a scanning electron microscope to characterise the different failure modes. Results show that the shear strength of the specimens, which results mainly from the adhesive, is better than their peeling strength, which is closely related to clinched structures. The mixed neck fracture exhibited the highest shear strength, and a better ability to absorb energy could be obtained by decreasing the material strength of the lower sheets in the tensile-shear test. In the peeling test, it was found that the best energy absorption ability could be achieved by the failure mode of upper sheet tearing, and improving the strength of the lower sheets resulted in greater joint peeling strength.
... The metal sheets are locally deformed and connected without any additional materials such as glue or fasteners. The joints produced by mechanical clinching have a high static strength and fatigue life [7][8][9]. Moreover, mechanical clinching has many advantages over conventional technologies, including a low-noise output, fumeless emissions, the absence of surface pre-treatment, high efficiency and lowenergy consumption. ...
Mechanical clinching is a connection technology that is widely used in different industrial fields because it has several advantages, including easy preparation, an excellent fatigue property and environmental friendliness. In this study, tensile-shear tests and fatigue tests were conducted to characterize the mechanical properties of clinched joints using aluminium alloys. The experimental results showed that the fracture regions were concentrated in the indentations of the lower sheets. The failed surfaces were examined using a scanning electron microscope and an energy-dispersive X-ray machine to study the fretting fatigue failure mechanisms of the clinched joints. Two types of fretting wear modes were observed: the neck fretting wear mode and indentation-surrounding fretting wear mode. The results also showed that the proportions of these two fretting wear modes could be impacted by the applied load levels.
... Clinching is a joining process where a mechanical interlock (i.e. local deformation without use of any additional joining elements) is created by a tooling set (a punch and a die) [18], as shown in Figure 4(a). Clinching is a simple technique for point joining of metal sheets typically from 0.2 mm to 4 mm thick, to a total joint thickness of about 6mm. ...
An automotive battery pack for use in electric vehicles consists of a large number of individual battery cells that are structurally held and electrically connected. Making the required electrical and structural joints represents several challenges, including, joining of multiple and
thin highly conductive/reflective materials of varying thicknesses, potential damage (thermal, mechanical, or vibrational) during joining, a high joint durability requirement, and so on. This paper reviews the applicability of major and emerging joining techniques to support the wide range of joining requirements that exist during battery pack manufacturing. It identifies the advantages, disadvantages, limitations, and concerns of the joining technologies. The maturity and application potential of current joining technologies are mapped with respect to manufacturing readiness levels (MRLs). Further, a Pugh matrix is used to evaluate suitable joining candidates for cylindrical, pouch, and prismatic cells by addressing the aforementioned challenges. Combining Pugh matrix scores, MRLs, and application domains, this paper identifies the potential direction of automotive battery pack joining.
... Principles of the clinching methods[10] ...
... Among the different mechanical fastening techniques available in manufacturing, clinching is a common method of joining by forming in which two or more sheet metals are locally deformed using punch and die to form a geometrical interlock [6][7][8] as shown in Fig. 1. Clinching enables joining of two or more similar or dissimilar sheet materials where individual thickness can vary from 0.4 to 4 mm [9]. ...
AA7075 aluminum alloy sheets in different temper conditions (O, W and T6) were joined by die-less clinching.
The material flow behavior, neck thickness and interlock characteristics during clinching were investigated by
metallographic observations of clinched, cut and mounted samples. Blank holders of different shapes and dimensions
were used to control the material flow. The effects of blank holder geometric parameters as well as
forming forces on the shape of the formed interlock in clinching were studied. The highest strength temper state
(T6) was shown to possess poor clinch-ability as it failed to clinch under most clinching conditions. This was
attributed to its poor ductility and formability at room temperature compared to the other tempers. Lastly,
mechanical performance of the formed joints was characterized by conducting single shear lap as well as peel
tests. Various failure modes were observed for the different clinching conditions and material temper states.
... In translational clinching, the axes of punch and die always remain aligned to each other and perpendicular to the sheets. Deviations in these parameters lead to a non-symmetric joint formation [3]. The same is observed for roller clinching. ...
Clinching as a joining method for sheet metal components offers various advantages. Therefore, the process optimization using finite element simulations is continuously increasing. For translational clinching, the use of rigid tools results in a good prediction of process forces and joint properties. In case of roller clinching, the lateral forces acting on the punch lead to significant elastic tool deformation during the process. This paper focuses on the effects of the tool elasticity on the joining forces, the tool deformation and the joint formation during roller clinching. The results are obtained using the finite element tool Abaqus. To evaluate whether higher simulation costs in form of elastic tools are necessary, the obtained clinchpoints are compared to experimental data.
Demand and interest in electric vehicles are increasing rapidly due to environmental issues. Improving the
performance of electric vehicles requires the development of automotive batteries and battery joining technologies.
Aluminum alloys are the most widely used metals in the electric vehicle industry, and aluminum bonding is used in all
processes comprising automotive batteries. Therefore, in this paper, based on the characteristics of aluminum and
aluminum alloys and knowledge of various aluminum joining technologies, the main and the next generation bonding
technologies used in automotive battery are reviewed. It also explains the structure of automotive secondary battery cells
and the integration order of 'cell-module-pack' where joining is used in the process, also various environmental conditions
that must be considered when joining.
The increasing application of novel and high-performance metallic materials poses new challenges to the problem of joining sheets. Clinching technology has become the common means of green joining in the automotive industry. The application of conventional clinching to visible surfaces in automobiles is limited by the external protrusion of the clinched joint. It cannot be ignored the important role of the blank holder in controlling the material flow in the clinching process. In this study, the joint quality of Al5052 sheets for the flat clinch-rivet process was investigated by experimental methods. A flat bottom die and rivets were used to form joints under different blank holder structures. Geometric parameters, static strength, failure modes, and energy absorption were analyzed. The results indicate the flat clinch-riveted joints created by the conical stepped blank holder have the advantages of no indentation, high energy absorption, and high joint strength. The flat clinch-rivet process should preferably use a conical stepped blank holder.
Das Gewicht von Fahrzeugkarosserien kann durch den Einsatz von Leichtbauwerkstoffen reduziert werden, in der Massenproduktion ist die Kombination von Aluminium und Stahl besonders interessant. Unabhängig von ihren unterschiedlichen Schmelztemperaturen können Aluminium und Stahl durch das Metall-Ultraschallschweißen im festen Werkstoffzustand energieeffizient, schnell und ohne Zusatzwerkstoffe verbunden werden. Zur Herstellung eines großflächigen Werkstoffkontaktes auf mikroskopischer Skala wird eine Anpresskraft mit hochfrequenten Schwingungen überlagert, die sich in den Bauteilen ausbreiten und bereits vorhandene Schweißpunkte beeinflussen können. In dieser Arbeit wurde daher ein Prozess entwickelt, um die Aluminiumknetlegierung AA6005A-T4 mit dem feuerverzinkt-geglühten Dualphasenstahl HCT980X+ZF100 sowie dem feuerverzinkten, niedriglegierten Stahl HX380LAD+Z100 durch aufeinanderfolgend erzeugte Schweißpunkte zu verbinden. Die zentralen Prozessparameter wurden mithilfe einer statistischen Versuchsplanung ermittelt und auf hohe und gleichzeitig zuverlässige Zugscherkräfte optimiert. Zur Analyse der Fügeprozesse wurden Temperaturmessungen in der Schweißzone, die Zeitverläufe der Leistung des Ultraschallgenerators sowie die Schweißzeiten selbst herangezogen. Ferner wurden licht- und rasterelektronenmikroskopische Untersuchungen inklusive energiedispersiver Röntgenspektroskopie an Quer- und Längsschliffen sowie an Bruchflächen der Schweißverbindungen nach der Zugscherprüfung durchgeführt. Die Prozess- und Verbundeigenschaften wurden sowohl durch die spezifische Position und Reihenfolge der Schweißpunkte als auch durch die Zinkschichten der Stahlbleche beeinflusst. Den Abschluss der Arbeit bildet die Erarbeitung eines Bindungsmodells für das vorliegende Multi-Material-System. Die Erkenntnisse können zur Entwicklung zukünftiger Anwendungen des Metall-Ultraschallschweißens in Aluminium/Stahl-Strukturen mit mehreren Verbindungsstellen beitragen.
Mechanical clinching is used to create lightweight hybrid structures. In order to estimate the service life of clinched components, its fatigue properties need to be known under different mechanical loading conditions. In addition to fatigue, corrosion is another factor that affects the fatigue life of clinched joints. In the literature, many corrosion and high-cycle fatigue damage models exist. However, little is known about how both phenomena interact in clinched joints. In this article, the influence of galvanic corrosion on clinched EN AW-6014/HCT590X + Z sheets on the fatigue life is investigated by means of numerical simulations and experimental results. An accurate prediction of the Wöhler lines of non-corroded and pre-corroded clinched specimens is shown.
Clinching technology has been extensively applied as a green and clean joining method, which has the benefits of less energy consumption, no pollution and no noise. However, a single joint produced by round tools cannot withstand the torsion force. In order to solve this problem, a square clinching technology was proposed and investigated in this paper. The main geometric parameters, failure mode, static strength, and energy absorption of the square clinched joint were studied. The fracture characteristics of square clinched joints under different mechanical experiments were studied by a scanning electron microscope. The strength tests of Al5052 clinched joints under various forming forces were carried out. The results showed that the neck fracture mode was the only failure mode observed during the failure process. The microscopic morphology of the joint fracture shows typical ductile fracture characteristics. It turned out that the square clinching process can effectively join aluminum alloy sheets.
The clinching technology attracted increasing attention in recent years, but its application might be restricted due to the growing employment of materials that are difficult to join and hybrid structures involving different mechanical performance materials. Traditional clinching technology has limitations of strain rate sensitivity, ductility and damage fracture when applied to materials with high strength, low strain-to-failure and low plasticity. However, the ductility and formability of the material represent a limitation for the clinching process. The present study explored some concepts of clinching, such as hole, friction-assisted, laser-assisted, electro-hydraulic, electromagnetically assisted and hot assisted clinching, for the difficult-to-form sheets. The paper includes the description of the deformation mechanism of clinched joints and the analysis of clinched joint performance and applicability.
The aim of the investigations described in this article is to improve the clinching of aluminum die casting. The focus is on clinching an aluminum die casting alloy by local heat treatment and hence to join them in a process-safe manner. For this purpose, a heating strategy is used to warm up the die casting alloys to reduce temporarily and reversibly the elongation and the yield strength in the material. In preliminary investigations, three different heating strategies (heating plate, resistance heating and inductive heating) have been investigated. Induction heating has been selected as the most suitable method due to the short heating time and the production of crack-free clinch points. In this paper, two clinching tool systems (one with a flexible die, one with a rigid die) were used. For these tools, two inductors with different diameter were manufactured. The effects of each inductor and clinching tool on an aluminum die casting alloy, such as heating time and crack behavior, were investigated. Surface images of the clinch points in regard to the heat treatment temperature were analyzed. Furthermore, the characteristic parameters of the joints such as interlock, bottom thickness and neck thickness were examined. In addition, the strength of the joined parts was investigated by head tension tests. The results of the developed method showed that it is possible to produce crack-free clinching joints below 6 s. Furthermore, the local heating led to an increasing interlock resulting in a 26% increase of the head tensile strength.
An experimental investigation was carried out to probe into the effect of the thickness arrangement on the failure mechanism and mechanical behaviour of the square joint produced by square clinching tools. Failure mode, geometrical characteristics and absorbed energy of the square joint were investigated to evaluate the quality of the square joint. Full shear and button separation are two major failure types observed in failure tests. The micro morphology of different joint fractures was studied by SEM. Lap shear load and lap tensile load of the square joint were measured during failure process. From the results, the fracture of joints with various sheet thickness arrangements shows typical ductile fracture characteristics. Interlock and neck thickness of the square joints in various thickness arrangements enlarge along with the gain of the top sheet thickness. Greater mechanical load-carrying ability and absorbed energy of the square joint were observed when the thicker sheet is on the top layer. Square clinching process can achieve the joining of Al5052-H32 sheets with dissimilar thickness arrangements reliably. Thicker sheets are suitable for being placed on the top layer during the square clinching process.
The focus of this study is to improve the clinching ability of an aluminum die casting alloy with a sheet metal by local annealing in order to clinch them in a process-safe manner. For this purpose, the influence of three different heating strategies (heating plate, resistance heating and inductive heating) on the generation of clinching joints are investigated. Furthermore, the strategies are compared with regard to process time, joining point formation and bonding strength. Finally, the different heating strategies were evaluated and the most promising process parameters were identified.
Volume 14B on sheet forming is the second of two volumes on metalworking technology. This volume addresses all methods of sheet metal fabrication technologies, selection of equipment and die materials, specification of forming practices for specific alloys, and new techniques for process design and control. It provides practical reference information on the basic processes of press forming, drawing, bending, spinning, shearing, blanking, and piercing of sheet with additional coverage on forming with bar, tube, wire, shapes, or long parts. For information on the print version of Volume 14B, ISBN 978-0-87170-710-9, follow this link.
This study is based on the joint quality of zinc-coated EN 10346: 2015 DX52D + Z quality steel sheets with having different thicknesses, which are preferred in the automotive industry due to their formability. Joining problems in clinching applications with different positions and sheets of different thicknesses are discussed and experimental outcomes are discussed in terms of strength of joints. As a result of the tests carried out according to the standards, it has been found that the joining of the sheets with thickness close to each other is relatively good, as the thickness difference increases, the joint quality decreases and sometimes the joint does not form. It has been also found that if the thinner sheet is placed on the bottom die during clinching, a better joint strength is obtained.
A mechanical clinching process with preforming of a lower sheet was developed to join two ultra-high strength steel sheets having low ductility. The thickness reduction of the upper sheet around the punch corner becomes small because of the decrease in the pressure from the preformed lower sheet, and then the interlock is increased by the expansion in the radial direction in the final compression. The shapes of the die and preformed lower sheet were optimized to increase the interlock. Furthermore, the strength of the sheets joined by mechanical clinching with the preformed lower sheet was compared with that of the sheets joined by resistance spot welding. The fatigue limit of the sheets joined by clinching was greater than that of the welded sheets, while the static load of the mechanically clinched joint was smaller. It was found that the mechanical clinching process with preforming of the lower sheet was effective for joining ultra-high strength steel sheets having low ductility and high flow stress.
This study is focused on the wear of the die cavity of the mechanical clinching tool used for joining microalloyed hot-dip galvanized advanced high-strength steel sheets H220PD+Z. Steel sheets were joined using round, single stroke clinching with rigid die with no flexible elements. The joint forming process takes place within the specially formed cavity of the die. Dies and punches for the mechanical clinching were made of tool steel (1.3343 grade) and subsequently covered by three types of PVD coatings: ZrN, CrN, and TiCN ones. The individual die wear was evaluated during the operation period, which means that 300 joints were produced by each die covered with the corresponding coating. The experimental data obtained were compared with the results of FEA numerical simulation, which substantiated the fact that the dominant part of wear is localized in the radius area surrounding the die cavity.
This paper describes a study into the potential of a new connection technique for use in cold-formed steel structures. The technique, called press-joining, has many advantages over current methods. A series of small scale tests was carried out to investigate the performance in shear and bending. Comparative tests were also carried out with rivets and self tapping screws. Four full scale structural tests were carried out on pitched roof trusses using cold-formed steel channel sections. Copyright (C) 1996 Elsevier Science Ltd.
Cold-formed steel structures are used extensively in buildings. The use of structural frames and trusses fabricated from cold-formed steel sections is increasing. A key element in the manufacturing of such structures is the nature of the connection between sections. Many conventional connection techniques have some disadvantages. The paper describes and summarizes a major investigation into the application of a new technique, known as press-joining. An extensive program of small-scale shear and bending tests was carried out. A series of full-scale trusses was constructed and tested. It is shown that effective structures can be constructed using the technique. A theoretical method for predicting the strength of joints is presented.
This paper describes a relatively new joining technique for cold formed steel structures called press joining. Press joining is a technique whereby a joint is created from the sheets to be connected, requiring no additional fixing items. A series of shear test results are given.The effect of UTS, steel thickness and angle of inclination of the join on both strength and deformation characteristics of the press join are discussed.A theoretical expression based on the results is developed linking all of the influencing factors to the shear strength of the join.
Cold-formed steel structures
- As Nzs
AS/NZS 4600, Cold-formed steel structures, Australian/New Zealand Standard, Homebush, Australia/Wellington, New Zealand, 1996, pp. 111–115.
Analysen der Beanspruchungen durchsetzgefügter Strukturen
- Budde
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Kuumasinkityn lujan rakenneteräksen puristusliittäminen (Clinching of zinc-coated high strength structural steel
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Connecting sheet metal by press joining
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Verbinden von Blechteilen zwischen Stempel und Gravur
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A novel procedure for establishing clinching parame-ters for high strength steel sheet. Dissertation, in: Acta Universi-tatis Lappeenrantaensis
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Qualitä durch rech-nergestütztë Uberwachung des betrieblichen Druckfü
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Ohutlevyjen Puristusliittä (Clinching of Sheet Metals), Federation of Finnish Metal, Engineering and Electrotechnical Indus-tries, MET, Helsinki
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J. Varis, Ohutlevyjen Puristusliittä (Clinching of Sheet Metals), Federation of Finnish Metal, Engineering and Electrotechnical Indus-tries, MET, Helsinki, 1997, p. 55 (in Finnish).
Aufbau eines Expertensystems fü mechanische Fü
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TOX®-puristusliitoksen simulointi elementtimenetelmää käyttäen. Teräsrakenteiden tutkimus-ja kehityspäivät
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B. Nilsson, E. Sagströ, Handbok fö Stuknitning Nr 1, 1995. Fakta Rapport: Bearbetning och fogning av plå, Sveriges Verkstadsindustrier, Stockholm, 1995, p. 87 (in Swedish).
Analyse und systematische Einteilung umformtech-nischer Fü ohne Hilfsfü
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Connecting sheet metal by press joining
- Liebig
Numerische Simulation nichtschneidender Durchsetzfügevorgänge
- Klasfauseweh
Qualitätssicherung durch rechnergestützte Überwachung des betrieblichen Druckfügeprozesses
- Liebig
Prozessüberwachung in der Druckfügetechnik
- Liebig
Analyse und systematische Einteilung umformtechnischer Fügeverfahren ohne Hilfsfügeteil
- Hahn
Aufbau eines Expertensystems für mechanische Fügetechnik
- Budde
In den punkt geschaut
- Wössner
A novel procedure for establishing clinching parameters for high strength steel sheet. Dissertation
- Varis
Prozessanalyse beim druckfügen
- Bober
Verbinden von Blechteilen zwischen Stempel und Gravur
- Liebig
Durchsetzfüge- und Punktschweissverbindungen unter quasistatischer und dynasmischer Beanspruchung
- Hahn