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Abstract
To extend current ultrasonic additive manufacturing (UAM) to advanced materials, higher speeds and larger parts, it was essential to greatly increase the process ultrasonic power. EWI, with Solidica™, several industry, agency and academic partners, and support of Ohio's Wright Program, have developed a "Very High Power Ultrasonic Additive Manufacturing System" that greatly extends current technology. A key part was the design of a 9.0 kW "push-pull" ultrasonic system able to produce sound welds in materials such as Ti 6-4, 316SS, 1100 Cu and Al7075. The VHP system can fabricate parts of up to 1.5m × 1.5m × 0.6m, with process and software developments that enable forming contoured surfaces.
... VHP UAM was created to improve bonding by increasing the maximum processing amplitude (from 26μm to 52μm) and normal force (from 2.5kN to 33kN). These increases have allowed for successful initial joining studies of previously difficult to join materials [6]. ...
... Mechanistically UAM is no different from VHP UAM. VHP UAM was developed so that harder and stronger materials could be processed by increasing the maximum amplitude (from 26μm to 52μm) and normal force (from 2.5kN to 33kN) [6]. A diagram in Figure 2 The UAM process is mechanistically very similar to ultrasonic welding. ...
... These increases have allowed for successful initial joining studies of previously difficult to join materials [6]. ...
... The range of applications are broad, extending to the welding of dissimilar metals, welding of "hard" metals (such as Ti, Cu, Ni, and stainless steel) [54], parts with embedded sensing [50], and parts with motion, stiffness, or temperature control to name a few [26]. ...
... All embedding trials reported throughout this research were performed on a recently developed very-high-power UAM (VHP UAM) "test bed" as reported in [54]. ...
... Conversion of the model into program code is carried out with the help of slicer programs, which translate the resulting highly discrete, polygonal 3D model into G-code for a 3D printer. The most common slicers are Cura, Kisslicer, Slic3r, and many others, [21]. ...
The relevance of introducing additive technologies of 3D printing in construction is to decrease the technological cycle of construction, and minimize expenditure and material costs, while reducing the duration of the development planning process and execution, eliminating inaccuracies and defects, as well as optimizing and automate the process. The technological aspect of 3D printing lies in the optimal selection of parameters based on the created 3D model using effective software. The purpose of the study is to determine the quality indicators of bricks obtained by 3D printing from special concrete. The approach to investigating this matter is rooted in ascertaining the compressive strength of concrete through non-invasive testing techniques, gauging the density of concrete using measurement methods, and validating the efficacy of integrating 3D printing technologies in construction by the method of comparative analysis. The effectiveness of introducing additive technologies of 3D printing was proven drawing upon quality indicators of concrete obtained on a 3D printer which meets all the requirements necessary for its implementation in the construction field. The selected characteristics of concrete compressive strength are fundamental to the basics of selecting a brand of concrete to be utilized in construction. The selected software demonstrated the capacity to generate flawless 3D designs. The result of the study shows a significant reduction in the number of workers involved in the construction process by 38–45%, depending on the chosen method of using 3D printing; a decrease of construction time by 33–42% when printing individual elements, blocks used in production, and by 61–72% when using a printer directly on the construction site; reduction of raw materials costs by 14–28%; as well as reduction of construction downtime by 25%. The results obtained indicate the need to develop and enhance progressive additive technologies for 3D printing in construction.
... welding horn (also known as the "sonotrode") rolling in the x-direction, (b) to create a solid metal part by welding a series of tapes, first side by side, then one on top of the other (but staggered so that seams do not overlap), as illustrated. (Graff et al., 2010) ...
The process of additive manufacturing (AM), commonly known as 3D printing, is a method of constructing a component by progressively adding material in layers using digital 3D design information. As part of 'Industry 4.0,' many industrial technologies are rapidly increasing to thrive in the twenty-first century. This study goes over seven different types of additive manufacturing in great detail. These technologies make it possible to make complex, high-value parts quickly and in small quantities without using as much energy or material or making as many tools as subtractive manufacturing does. Besides, AM also possesses some particular challenges, like post-processing, material unavailability, software issues, etc. The application of AM is expanding rapidly from micro to macro-scale sectors. 3D printing technology will change industrial operations in the following years. Eventually, the elected technology will be closely related to the proposed function.
... Technologies using metals hardly suffer from these drawbacks (Fig. 2). Fig. 2. Layer-by-layer manufacturing of a metal product: 1 -laser; 2 -a system of mirrors;3 -laser beam; 4 -lens; 5 -construction zone; 6 -transport gas; 7 -metal powder;8 -building platform Manufacturing of metal products is possible due to melting powder, filler wire or sheet metal (Fig. 3) [5][6][7][8][9][10][11][12][13][14][15]. ...
The paper presents a state-of-the-art review of additive manufacturing and summarizes its development trends. It considers mainstreams of this technology and outlines its methods. The study highlights importance and prospects of the process based on electrode wire arc welding (GMAW and GTAW). It proposes a layered electric arc deposition by a consumable electrode in shielding gases. A peculiarity of this procedure is that a wire is preheated to a temperature of 400-600°С before fed into a zone where metal products are formed. Wire preheating is realized by an additional power supply placed at a distance of 250-400 mm from a wire end to conduct a preheating current. It is suggested this process is suitable for manufacturing metal products in principle. The study has revealed a gradient structure of product walls manufactured using this technology. It is an upper deposited layer only that has a dendrite structure. Layers below it are subject to repeated thermal treatment caused by heat liberation from the upper layer. As a result, a grain tends to the refinement up to 10 μm depth wise. The most important outcome to emerge from the study is that a 4 mm thick frame structure free of defects may be built given that deposition is carried out by a material with a diameter of 1.2 mm in the conditions: current force 120-140А, voltage 22-24 V, deposition rate 300 mm/min.
... This welding process is repeated either next to, or on top of, the preceding layer of foils to build up a component. Then, the subtractive stage is used to selectively remove material and machine the component to its final dimensions [1,2]. It can also be employed to make internal features such as channels for embedding reinforcement fibers [3] and thermally sensitive smart materials [4]. ...
Ultrasonic additive manufacturing (UAM) is a solid state manufacturing process capable of producing near-net-shape metal parts. Recent studies have shown the promise of UAM welding of high strength steels. However, the effect of weld parameters on the weld quality of UAM steel is unclear. A design of experiments study based on a Taguchi L16 design array was conducted to investigate the influence of parameters including baseplate temperature, amplitude, welding speed, and normal force on the interfacial temperature and shear strength of UAM welding of carbon steel 4130. Analysis of variance (ANOVA) and main effects analyses were performed to determine optimal weld parameters within the process window. A Pearson correlation test was conducted to find the relationship between interfacial temperature and shear strength. These analyses indicate that the highest shear strength of 392.8 MPa can be achieved by using a baseplate temperature of 400°F (204.4°C), amplitude of 31.5 μm, welding speed of 40 in/min (16.93 mm/s), and normal force of 6000 N. The Pearson correlation coefficient is calculated as 0.227, which indicates a weak positive correlation between interfacial temperature and shear strength over the range tested.
... There is barely any reported work on ultrasound NDT diagnostics on PBF and SLM products in the current literature. However, in other printing methods, such as wire arc additive manufacturing (WAAM) [81], very-high-power ultrasound AM [82], and friction stir AM (FSA) [83], ultrasound NDT testing and diagnostics could be suitable due to the larger products and size of discontinuities resulting from the techniques. A study reported that traditional A mode ultrasonic diagnostics in WAAM aluminum and steel products by 500 kHz transducer are successful [84]. ...
Additive manufacturing technologies based on metal are evolving into an essential advanced manufacturing tool for constructing prototypes and parts that can lead to complex structures, dissimilar metal-based structures that cannot be constructed using conventional metallurgical techniques. Unlike traditional manufacturing processes, the metal AM processes are unreliable due to variable process parameters and a lack of conventionally acceptable evaluation methods. A thorough understanding of various diagnostic techniques is essential to improve the quality of additively manufactured products and provide reliable feedback on the manufacturing processes for improving the quality of the products. This review summarizes and discusses various ex-situ inspections and in-situ monitoring methods, including electron-based methods, thermal methods, acoustic methods, laser breakdown, and mechanical methods, for metal additive manufacturing.
... At early stage of the development of ultrasonic consolidation (UC)/ultrasonic additive manufacturing (UAM), mainly aluminium alloys, such as Al 3003 and Al 6061, are used as the deposition material, because they are soft and easier to be bonded together by ultrasonic welding with a high linear weld density (LWD), which is defined by the ratio of the bonded interface length to the total interface length in a cross-section. However, with further development, mainly the introduction of very high power ultrasonic additive manufacturing (VHP UAM) machines [45], due to the increased maximum power, applied normal force and vibration amplitude, nowadays more harder materials can also be used for UAM, such as copper [13][14][15], nickel [16], steel [17] and titanium [19][20][21]. Two conditions are necessary for metallurgical bonding to occur: oxide removal and asperity collapse (plastic deformation) [46,47]. ...
Ultrasonic additive manufacturing (UAM) is a solid-state metal additive manufacturing process, with the combination of layer by layer ultrasonic seam welding and CNC machining. Due to the friction and deformation at the bonding interface, the ultrasonic softening effect and temperature generated, the microstructure of the substrate materials is evolving constantly. In this paper, in order to better understand the bonding mechanisms, the good practice and the capability of UAM, and the influence of different key process parameters on bonding quality, the microstructure evolution during UAM is reviewed in detail. Defects can be generated at the UAM bonding interface, but by choosing the right material combination and the right process parameters, defects can be reduced to minimum. Plastic deformation is very important for the bonding between layers during UAM, and plastic flow is important for redistribution of oxide layer, forming of mechanical interlocks, filling micro-valleys on the mating surface, and filling the gaps when embedding elements. UAM process can cause recrystallization and grain refinement at the welding interface and the intimate bulk materials around, and it will also gradually change the texture from rolling texture to shear texture. In the meantime, when further layers of materials are deposited on the top of the existing part, the microstructure will have some accumulative change. In order to reduce the defects number and increase the strength, sometimes, heat treatment needs to be carried out to the as-deposited parts, which will change the microstructure as well. Finally, the relevant research is summarised and the perspectives of further research are recommended.
... Ultrasonic additive manufacturing (UAM) is a solid-state additive manufacturing process that produces near net shape parts from metal foil feedstock [1]. Certain UAM systems integrate ultrasonic metal welding and computer numerical control (CNC) machining capabilities, which enable them to create parts with arbitrary internal features and unique geometries. ...
Ultrasonic additive manufacturing (UAM) is a solid-state 3D printing technology. Steels can be welded with UAM at reduced ultrasonic power, achieving half the shear strength of bulk material. A higher weld power is demonstrated by using a cobalt-based sonotrode coating, achieving shear strengths comparable to bulk 4130 material. In-situ temperature measurements and fracture surface analyses indicate that higher power input promotes metallurgical bonding through softening and increased plastic deformation. Carbides and ferrite are found at 1μm scale at key weld interfaces; no martensite is found due to an increase in critical transformation temperatures associated with high heating rates.
... The schematic diagram of USW is illustrated in Fig. 1. A typical USW system is comprised of the ultrasonic frequency generator with a power amplifier, transducer, booster, sonotrode with weldable tips, and anvil [8]. Initially, the 50 Hz frequency of standard alternating current (AC) supply is converted to high-frequency power with the help of an ultrasonic frequency generator. ...
Electrification of vehicles presently grabs attention as an essential factor in most of the automotive manufacturing industries due to continuous upsurge in environmental pollution, unstable fuel prices, and stringent government policies against gasoline fuels. In order to tackle these challenges, a conservative and energy-efficient technique is required. The high power ultrasonic metal welding (USMW) process has been effectively used in the automotive industries for assembling lithium-ion (Li-ion) battery packs and its modules due to its solid-state principle. Aluminum (Al) and copper (Cu) are the two most crucial and commonly employed conductive metals. The joining of these materials by conventional methods is extremely difficult due to its higher thermal, chemical and physical properties. However, USMW yields better quality welds under the influence of optimal parametric conditions. In the current study, the effect of various weld parameters such as weld time, weld pressure, vibration amplitude, and different surface conditions are investigated to study the weld strength and failure behaviour by mechanical and microstructural analyses. The tensile shear and T-peel failure loads of the weld are maximum at the highest vibration amplitude with a moderate amount of weld pressure and weld time. Meanwhile, these weld strengths are decreased with an increase of surface roughness due to the disappearance of relative motion between the Al-Cu sheets. Micro-hardness study reveals the material softening and hardening phenomena during the welding process. The various types of weld qualities are also classified as ‘under weld,’ ‘good weld’ and ‘over weld’ based upon the nature of bond formation and spreading of microbonds across the weld interface at various weld parametric conditions. The future prospects of this USMW field is that the process engineers can now adopt this technique to get best combinations of input parameters in USMW problems, and there is no need to depend on the manufacturer’s handbook.
... The ultrasonic welding process opens up the possibility of producing bulk metallic glasses by welding multiple overlapping amorphous ribbons [13]. The use of the additive production process in the ultrasonic field opens the possibility of complex obtaining some geometry made by this the of parts process, bu the temperature t distribution in the joined area is very difficult [14]. obtaining bulk metallic for method Welding of a amorphous viable ribbon packages can be glasses. ...
With the evolution of society new materials or classes of materials must be developed. The metallic alloys with amorphous structure have exceptional physical properties due to the spatial order of the atoms in structure and the absence of crystalline defects such as dislocations, grain boundaries, etc. Due to the metastable states in which these alloys are located, obtaining bulk materials from amorphous metal alloys is difficult, being limited to simple geometries and high production cost. This problem can be solved by using the ultrasonic welding of amorphous ribbons for the production of bulk metallic glasses.In this paper, we aimed to produce bulk metallic glasses materials by welding the ribbon packages in ultrasonic field. In order to prove the preservation of the amorphous structure of both the primary welding alloys as well as after the welding of the amorphous ribbons, Differential thermal analysis (DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM) analysis were carried out. Vickers micro-hardness test was also performed in order to reveal the mechanical properties in the welded joint.
... Ultrasonic additive manufacturing (UAM), also known as ultrasonic consolidation, is a solid-state manufacturing process that combines additive welding and subtractive machining [6]. During the welding process, a rolling sonotrode is used to apply a force normal to metal foil feedstock along with ultrasonic (20 kHz) transverse vibrations. ...
Ultrasonic additive manufacturing (UAM) is a solid-state manufacturing technology for producing near-net shape metallic parts combining additive ultrasonic metal welding and subtractive machining. Even though UAM has been demonstrated to produce robust metal builds in Al–Al, Al–Ti, Al-steel, Cu–Cu, Al–Cu, and other material systems, UAM welding of high strength steels has proven challenging. This study investigates process and post-processing methods to improve UAM steel weld quality and demonstrates the UAM fabrication of stainless steel 410 (SS 410) builds which possess, after post-processing, mechanical properties comparable with bulk material. Unlike UAM fabrication of softer metals, this study shows that increasing the baseplate temperature from 38∘C (100∘F) to 204∘C (400∘F) improves interfacial strength and structural homogeneity of the UAM steel samples. Further improvement in strength is achieved through post-processing. The hot isostatic pressing (HIP) post treatment improves the shear strength of UAM samples to 344 MPa from 154 MPa for as-welded samples. Microstructural analyses with SEM and EBSD show no evidence of body centered cubic (BCC) ferrite to face centered cubic (FCC) austenite transformation taking place during UAM welding of SS 410. The weld quality improvement of UAM steel at higher baseplate temperatures is believed to be caused by the reduction of the yield strength of SS 410 at elevated temperature. HIP treatment is shown to increase the overall hardness of UAM SS 410 from 204 ± 7 HV to 240 ± 16 HV due to the formation of local pockets of martensite. Nanohardness tests show that the top of layer n is harder than the bottom of layer n+1 due to grain boundary strengthening.
... Ultrasonic additive manufacturing (UAM) is a manufacturing method using thin metallic foils or tapes as feedstock to fabricate 3D parts [95][96][97][98]. In this method, an ultrasonic wave and mechanical pressure are applied on metallic tapes at room temperature to bond the interfaces of the stacked tapes by diffusion [99]. ...
Copper has been widely used in many applications due to its outstanding properties such as malleability, high corrosion resistance, and excellent electrical and thermal conductivities. While 3D printing can offer many advantages from layer-by-layer fabrication, the 3D printing of highly pure copper is still challenging due to the thermal issues caused by copper’s high conductivity. This paper presents a comprehensive review of recent work on 3D printing technology of highly pure copper over the past few years. The advantages and current issues of 3D printing methods are compared while different properties of copper parts printed by these methods are summarized. Finally, we provide several potential applications of the 3D printed copper parts and an overview of current developments that could lead to new improvements in this advanced manufacturing field.
... However, this amount of power is insufficient to produce a higher vibration amplitude and normal force necessary to achieve good metallic bonding in harder materials and thicker foils (Refs. 5,6). While UAM of harder materials has been performed, no mechanical testing was reported to assess the actual strength of the UAM joint (Refs. ...
Ultrasonic additive manufacturing (UAM) is a solid-state joining process used to build
up a solid part from thin metal foils. The major process parameters are vibration amplitude,
normal force, and weld speed. In this study, the upgraded version of UAM, called
very high power ultrasonic additive manufacturing (VHP-UAM), which has a higher
power capability to produce a larger vibration amplitude and larger normal force than
UAM, was used to fabricate samples from aluminum 300-3H18 (Al3003-H18) foils. A total
of six VHP-UAM samples were fabricated from a Test-Bed machine and SonicLayer-7200
commercial VHP-UAM systems. The effects of increasing vibration amplitude and normal
force on the change in the bulk hardness of Al3003-H18 foil were investigated. The
results revealed that vibration amplitude played a more significant role in decreasing
hardness or softening behavior in Al3003-H18 foil when a larger vibration amplitude was
applied. There was also a clear correlation between the bulk hardness of Al3003-H18 foil
and the average ultrasonic power used, where the hardness decreased with increasing
ultrasonic power in samples fabricated from both VHP-UAM machines.
... Other researchers have proposed the application of the CNC material removal processes in building functional prototypes [2] [3]. In addition, ultrasonic additive manufacturing, a process of fusing thin metallic foil using an ultrasonic system and subsequently machining the features in each layer, has provided more capabilities for producing functional metallic parts [4]. The use of the CNC machining-in both conventional and layered fashions-is usually accompanied by some limitations, such as the impossibility of making complex internal features due to the tool radius and machining cost. ...
The existing building metallic prototypes from metal sheets or foil slices methods suffer some limitations, such as difficulty in making complex features and long process cycle time. The Fully Dense Freeform Fabrication (FDFF) process is a new freeform fabrication method capable of building fully dense prototypes from practically any materials in a layer-by-layer basis, which overcomes the limitations of other methods. However, layer aligning and stacking are still very challenging because aligning and stacking all thin layers takes a lot of time and effort. Therefore, an automated layer aligning and stacking system is proposed and implemented in this paper. A vision system together with a robotics system are developed to automate the FDFF process. Experiments were performed and the results demonstrate that the automated FDFF process can fundamentally improve the concept of rapid prototyping by enabling producing fully dense parts with any complexity and any solid materials for the sizes from micro scale to several feet in a very fast and low cost approach.
Ultrasonic additive manufacturing (UAM) is a process used for the three-dimensional printing of metal foil stock that can produce near-net-shaped metallic parts. This work details the development of an energy-based tool to identify the relationships between input energy, energy stored in the interface microstructure, and the strength of the weld interface in UAM. The stored energy in the grain boundaries of the crystallized grains in the interface microstructure are estimated using the Read–Shockley relationship. The energy stored in the interface is found to be positively correlated with the resulting weld strength. An energy flow diagram is developed to map the flow of energy from the welder to the workpiece and quantify the key participating energies such as the energy of plastic deformation, energy stored in the interface microstructure, energy required for asperity collapse, and heat generation. A better understanding of the flow of energy in UAM can assist in optimizing the process to maximize the portion of energy input by the welder that is used for bond formation.
The history of Additive Manufacturing (AM) goes back to the nineteenth century in the form of photo-sculpture and three-dimensional (3D) cartography. The AM process chain is not limited to technological advancements and process mechanisms but also accelerated and supported through developments in Computer-Aided-Design (CAD), materials, testing, certification, and post-processing. This chapter provides a chronological account of AM processes (Vat Photopolymerization, Powder Bed Fusion, Directed Energy Deposition, Material Jetting, Material Extrusion, Sheet Lamination, and Binder Jetting) from late nineteenth century to present. Readers will have a clear understanding about the origins and development of different AM processes, thereby to gain foresight about possible trends in AM and its future applications.
Additive manufacturing (AM) is viewed as a critical enabling technology for achieving superior performance and improved economics across many sectors. Although the past decade has seen increased application of AM methods to nuclear reactor cladding and structural materials, exploration of AM as applied to the uranium-bearing nuclear fuel forms has been limited. The two major families of nuclear fuel forms (monolithic, particle/dispersion) are utilized with their own set of core objectives in mind, and their differences require distinct fabrication infrastructures. These reference fabrication methods impose many limitations on nuclear fuels. Both currently operating reactors and future concepts have the potential for improved performance if these accepted limitations are relaxed or removed entirely. The primary limitations of reference fabrication processes for the common nuclear fuel forms are outlined in this paper. This groundwork is then used to identify avenues of fuel performance specific to each of these fuel architectures that could be exploited if the restrictions of conventional fuel fabrication are removed. Moreover, multiple targets for AM studies are laid out for each of the major nuclear fuel variants. Finally, key strategic components to guide research activities in AM of nuclear fuels are outlined, with an emphasis on use of modeling and simulation to motivate research aims and embrace of an accelerated testing methodology to screen and quality new fuel forms.
Sheet based process uses machining but is generally dealt in the realm of additive manufacturing (AM). It brings a question whether sheet based process is an AM and if it is not an AM then whether it is hybrid AM. It could be easy to know whether it is AM, but it could not be so easy to know whether it is hybrid AM because there exists no criteria and definition for hybrid AM. This chapter applies the concept of hybrid manufacturing to sheet based process to check whether it is hybrid AM. Various sheet based processes such as ultrasonic consolidation, laminated object manufacturing and friction stir AM are briefly explained.
Additive manufacturing technology for ultrasonic consolidation (UC) makes use of the properties of piezoelectric transducers, which produce high-frequency vibrations. When applied to metal foil surfaces, these vibrations help form solid-phase bonding between metals under certain pressure. To obtain better consolidation process parameters, samples of 0.2-mm-thick Ti-6Al-4V titanium alloy, and 6061 aluminum alloy were consolidated with the UC method; and temperature modeling and experiments of consolidation joints were carried out. First, the temperature field model of UC for Al-Ti foil was established, based on the temperature field theory of the UC system, and the transient temperature field distribution was obtained by finite element analysis. The highest temperature of the consolidation system was mainly concentrated on the contact area between the sonotrode and the foil, as well as the foil and the substrate, and it gradually decreased along with the feed direction. Then, the temperature of Al-Ti foil was measured by thermocouple, and the maximum temperature was measured and compared with the simulated value. The experimental results show that the appropriate UC force for Al-Ti foil is 2.0–3.0 kN, the effect of the oscillator amplitude on the temperature of the consolidation interface is greater than that of the consolidation pressure, and the oscillator amplitude is greater than 40 μm. The above process parameters can facilitate the effective consolidation of Al-Ti foil.
The processes of ultrasonic spot welding and ultrasonic additive manufacturing are modelled by approximating the weld interface as rough metallic surfaces in sliding contact. It is assumed that bonding is due to athermal plastic deformation of surface asperities and the associated growth of metallic junctions along the weld interface. To link the process variables and the extent of junction growth, an expression for the real contact area at the weld interface is combined with process-specific frictional heating models developed here. The resulting framework is validated by comparing its predictions of the weld strength with data from the ultrasonic welding literature. The close agreement between the framework's predictions and the experimental data demonstrates that the surface asperities soften due to frictional heating, while acoustic softening effects are insignificant. The junction growth model is used to identify parameter sets for ultrasonic spot welding and ultrasonic additive manufacturing that maximize the weld strength while simultaneously minimizing the thermal excursion at the weld interface. It is found that in ultrasonic spot welding, certain processing conditions can cause interfacial melting, although melting is not required to form strong bonds. It is also shown that in ultrasonic additive manufacturing, the deposition rate is highest when the positions of the peak temperature and complete interfacial bonding coincide underneath the sonotrode. If the position of complete interfacial bonding leads the position of the peak temperature, there is excessive heating of the build, and the sonotrode velocity can be increased without degrading bond quality.
Ultrasonic additive manufacturing (UAM) is a solid-state additive manufacturing technology for joining similar and dissimilar metal foils together near room temperature by scrubbing them together with ultrasonic vibrations under pressure. Structural dynamics of the welding assembly and work piece influence how energy is transferred during the process and ultimately, part quality. To understand the impact of structural dynamics during UAM, a linear time-invariant model is used to relate the inputs of shear force and electric current to resultant welder velocity and voltage. Measured frequency response and operating performance of the welder under no load is used to identify model parameters. Using this model and in-situ measurements, shear force and welder efficiency are estimated to be near 2000 N and 80% when welding Al 6061-H18 weld foil, respectively. Shear force and welder efficiency has never been estimated before in UAM. The influence of processing conditions, i.e., welder amplitude, normal force, and weld speed, on shear force and welder efficiency are also investigated. Welder velocity was found to strongly influence the shear force magnitude and efficiency while normal force and weld speed showed little to no influence. The proposed model is also used to describe high frequency harmonic content in the velocity response of the welder during welding operations and coupling of the UAM build with the welder.
Very High Power Ultrasonic Additive Manufacturing (VHP-UAM) was used to fabricate 10 layers and up to 80 layers samples from aluminum alloy 3003-H18 foil (Al3003-H18) of 150 µm thickness with varying vibration amplitude and normal force. This research was aimed at studying the change in hardness, microstructure, and texture in Al3003-H18 foil both in as-processed conditions and in heat-treated (343°C-2hr) condition compared to original foil, and to utilize neutron diffraction method to characterize the bulk texture analysis of the bulk VHP-UAM samples. Results from Vicker microhardness measurement, optical microscopy, scanning electron microscopy, electron backscattered diffraction (EBSD), and neutron diffraction were used to describe the changes in hardness, microstructure, and texture. The difference in microstructure and texture evolution in VHP-UAM samples processed at different process parameters can be related to the energy input during VHP-UAM and the post-processing heat-treatment.
Ultrasonic additive manufacturing (UAM) is a recent 3D metal printing technology which utilizes ultrasonic vibrations from high power piezoelectric transducers to additively weld similar and dissimilar metal foils. CNC machining is used intermittent of welding to create internal channels, embed temperature sensitive components, sensors, and materials, and for net shaping parts. Structural dynamics of the welder and work piece influence the performance of the welder and part quality. To understand the impact of structural dynamics on UAM, a linear time-invariant model is used to relate system shear force and electric current inputs to the system outputs of welder velocity and voltage. Frequency response measurements are combined with in-situ operating measurements of the welder to identify model parameters and to verify model assumptions. The proposed LTI model can enhance process consistency, performance, and guide the development of improved quality monitoring and control strategies.
Additive manufacturing (AM), widely known as 3D printing, is a method of manufacturing that forms parts from powder, wire or sheets in a process that proceeds layer by layer. Many techniques (using many different names) have been developed to accomplish this via melting or solid-state joining. In this review, these techniques for producing metal parts are explored, with a focus on the science of metal AM: processing defects, heat transfer, solidification, solid-state precipitation, mechanical properties and post-processing metallurgy. The various metal AM techniques are compared, with analysis of the strengths and limitations of each. Only a few alloys have been developed for commercial production, but recent efforts are presented as a path for the ongoing development of new materials for AM processes.
Ultrasonic additive manufacturing (UAM) is a solid state joining technology that produces metal parts and components at low temperatures by utilizing principles of ultrasonic metal welding. The process can produce solid and gapless structures, however under certain processing conditions voids and poor mechanical properties may occur. Builds wider than the foil width require stacking of foils next to and on top of one another, leading to the potential for voids, while also requiring periodic machining to maintain flatness. This study proposes a methodology to improve the bonding and mechanical properties of Al 6061 UAM builds. Specifically, the stacking sequence of foil layers, the effects of surface roughness during welding and following machining, and post-process heat treatments are examined. An optimized stacking sequence for foils has been identified via mechanical strength testing, whereby tape to tape overlap should be greater than 0.0025 in. (0.0635 mm) using a randomized layer stacking sequence. Sonotrodes with a 14 μm Ra surface roughness are shown to provide improved bond quality compared to sonotrodes with 7 μm roughness. Welding onto surfaces roughened with the sonotrode after flattening passes has also shown to improve bond strength. Post-process heat treatments increase the bond strength over as-built conditions, providing strengths close to 90% of bulk material.
Ultrasonic additive manufacturing (UAM) is a process by which hybrid and near-netshaped products can be manufactured from thin metallic tapes. One of the main concerns of UAM is the development of anisotropic mechanical properties. In this work, the microstructures in the bond regions are characterized with optical and electron microscopy. Recrystallization and grain growth across the interface are proposed as a mechanism for the bond formation. The presence of voids or unbonded areas, which reduce the load-bearing cross section and create a stress intensity factor, is attributed to the transfer of the sonotrode texture to the new foil layer. This results in large peaks and valleys that are not filled in during processing. Tensile testing revealed the weld interface strength was 15% of the bulk foil. Shear tests of the weld interfaces showed almost 50% of the bulk shear strength of the material. Finally, optical microscopy of the fracture surfaces from the tensile tests revealed 34% of the interface area was unbonded.
This research presents microscopic evidence of dislocation propagation and sub-grain refinement in 3003-T0 aluminium undergoing high frequency fully reversed loading conditions during the Ultrasonic Consolidation process. Dual Beam Focused Ion Beam etching techniques and Transmission Electron Microscopy were used to characterize sub-grain morphology and dislocation structure in regions that were subjected to high levels of multi-axial ultrasonic micro-strain and resultant plastic deformation. This Deformation Affected Zone is characterized by regions of reduced sub-grain sizes that form a gradual transition into larger equiaxed, grains well below the interface.
While ultrasonic welding has been explored for some time, there has been little agreement on the specific softening mechanisms that allow an ultrasonic weld to occur. Usually, the unexplained effect is vaguely referred to as “acoustic softening,” or “ultrasonic softening” -- generic terms that do not identify a specific mechanism. This uncertainty has led to many disparate theories as to the specific nature of ultrasonic welding. The presented interface characterization discoveries challenge many of these ideas and prescribes a fundamental operative “ultrasonic softening” mechanism that is similar in character to the Bauschinger Effect.
Ultrasonic consolidation (UC) is a novel additive manufacturing process wherein three-dimensional metallic objects are fabricated layer by layer in an automated fashion from thin metal foils. The process has immense potential for fabrication of injection molding tooling with conformai cooling channels, fiber-reinforced composites, multi-material structures, smart structures, and others. The proportion of bonded area in relation to the total interface length, termed linear weld density (LWD), is perhaps the most important quality attribute of UC parts. A high level of LWD is desirable in parts intended for load-bearing structural applications. It is therefore necessary to understand what factors influence LWD and devise methods to enhance bond formation during ultrasonic consolidation. The current work elucidates the effects of process parameters on LWD in AI alloy 3003 UC parts. A set of optimum parameters for AI 3003 part fabrication using UC has been obtained, which may vary, however, for different foil materials and sonotrode/foil fric-tional conditions. The beneficial effects of using elevated substrate temperatures and its implications on overall manufacturing flexibility and the trade-offs between part quality and build time are discussed. The mechanism of ultrasonic welding is discussed based on oxide layer removal and plastic deformation at the weld interface. A preliminary understanding of defect formation during UC is presented, based on which a method (involving surface machining) for obtaining near-100% LWD is demonstrated. The findings of the current work encourage wider utilization of the UC process and could stimulate further research in the areas of UC process development and modeling.
During ultrasonic welding of sheet metal, normal and shear forces act on
the parts to be welded and the weld interface. These forces are a result
of the ultrasonic vibrations of the tool, pressed onto the parts to be
welded. Furthermore they determine the weld quality and the power that
is needed to produce the weld. The main goal in this study is to measure
and calculate the tangential forces during ultrasonic metal welding that
act on the parts and the weld interface and correlate them to weld
quality. In this study a mechanics based model was developed which
included a model for the temperature generation during welding and its
effect on the mechanical material properties. This model was then used
to calculate the interface forces during welding. The model results were
in good agreement with the experimental results, which included the
measured shear force during welding. With the knowledge of the forces
that act at the interface it might be possible to control weld quality
(strength) and avoid sonotrode welding (sticking of the sonotrode to the
parts). Without a solution to these two problems USMW will never be
applicable to large scale automated production use, despite its
advantages. In the experiments the influence of part dimensions,
friction coefficient, normal force and vibration amplitude on weld
quality and sonotrode adhesion were examined. The presented model is
capable of predicting and explaining unfavorable welding conditions,
therefore making it possible to predetermine weld locations on larger
parts or what surface preparation of the parts to be welded would lead
to an improved welding result. Furthermore shear force at the anvil
measured during welding could be correlated to changing welding
conditions. This is a new approach of explaining the process of USMW,
because it is based on mechanical considerations. The use of a shear
force measuring anvil has the potential to be implemented into welding
systems and the shear force would provide an additional means of process
control.
Welding of copper foils (150 μm thick) achieved at room temperature by very high power ultrasonic additive manufacturing was seen to involve appreciable softening and enhanced plastic flow. The initial coarse-grained structure (25 μm) in the material changed into fine dynamically recrystallized grains (0.3–10 μm) at the foil interface within the order of a few milliseconds of processing. This phenomenon led to metallurgical bonding through grain boundary migration and allowed for successive welding of tapes to form a three-dimensional part.
Development of a VHP UAM System
- M Short
- P H Zhang
- K Graff
Short, M., Zhang, P.H., Graff, K. (2008) Development of a VHP UAM System, The Ultrasonics
Industry Association.
Ultrasonic Additive Manufacturing
- M Short
Short, M. (2010) Ultrasonic Additive Manufacturing, American Welding Society Conference
on New Welding Technologies, Ft. Lauderdale, FL, June, 2010.
Object Consolidation Employing Friction Joining
- D R White
White, D.R. (2002) Object Consolidation Employing Friction Joining, U.S. Patent 6,4457,629,
October 1, 2002.