Machining, Joining and Modifications of Advanced Materials



This book presents the latest advances in mechanical and materials engineering applied to the machining, joining and modification of modern engineering materials. The contributions cover the classical fields of casting, forming and injection moulding as representative manufacturing methods, whereas additive manufacturing methods (rapid prototyping and laser sintering) are treated as more innovative and recent technologies that are paving the way for the manufacturing of shapes and features that traditional methods are unable to deliver. The book also explores water jet cutting as an innovative cutting technology that avoids the heat build-up typical of classical mechanical cutting. It introduces readers to laser cutting as an alternative technology for the separation of materials, and to classical bonding and friction stir welding approaches in the context of joining technologies. In many cases, forming and machining technologies require additional post-treatment to achieve the required level of surface quality or to furnish a protective layer. Accordingly, sections on laser treatment, shot peening and the production of protective layers round out the book’s coverage.

Chapters (19)

Sheet metal forming processes are deformation processes in which force is applied to a blank of sheet metal to modify its geometry rather than to remove any material. Bending is one of the most common die-forming methods. It can be defined as a forming operation in which the metal is deformed or bent along a straight axis, normally bending operations are made in U-die or V-die. Corner beads may often be used to impart rigidity bending which might otherwise be too flexible and weak. In a right-angle bent sheet, the bend is usually a weak point. By the use of stiffening ribs, the overall rigidity is increased. However, how many? This paper aims at the numerical and experimental investigation of increasing bending strength when stamping in right-angle bent sheet a rib or bead in different depth and separation between each and other. The cross-sectional of bead is V, in steel sheet of gage No. 16 (U.S. standard).
Boron nitride based tribological coatings promise hope in tribological applications thanks to their excellent lubrication and heat resistance properties. However, the applicability of these coatings on cutting tools in machining applications is not well known and it needs to be revealed. Therefore, in this study, a boron nitride (BN) coating was deposited on carbide milling tools. Inconel 718 was used as workpiece material in face milling tests to determine the wear behavior of the BN coated carbide tools. Surface roughness and tool wear was recorded in relation with cutting length. Wear mechanisms on the coated carbide tools were determined using scanning electron microscopy in combination with energy dispersive spectroscopy. Abrasive and adhesive wear was found as main failure mechanisms on the worn tools. Approximately two times longer tool life was obtained with the BN coated carbide tools.
This paper presents the development of a biocompatible polymer nano-composite material for the additive manufacturing (AM) process. The material was prepared by the mechanical of polycaprolactone (PCL), montmorillonite (MMT) and hydroxyapatite (HA) using a single screw extruder nanomixer. The amount of MMT material varied from 2 to 4 (wt%) and the HA was fixed at 10 (wt%). Then, the blended material was crushed and fed into a single a screw extruder to produce a filament of 1.8 mm in diameter. The material was characterized on mechanical properties, biocompatibility and manufacturability a fused deposition modeling machine. The results show an improvement in tensile and flexural properties by increasing the MMT. The SEM image shows the bulk formation of apatite layers on the composite surface which confirmed the bioactivity of the material. The material also was successfully produced on the Fused Deposition Modeling for rapid production such as implant components.
The processing of aluminum composites plays a significant factor in develop the usage of such composites. The analysis of microstructure of the deformed composites specimens gives a degree of understanding of the effect of deformation process conditions. In recent years, the advent of high-speed, general-purpose, digital computers and vision systems has made image analysis easier and more flexible. Computer vision technology has maintained tremendous vitality in many fields. One of the common techniques employed by computer vision is the texture features techniques. Texture is related to qualitative properties of surfaces, but due to its complexity and great variety, there exists neither a unique definition of texture nor an accepted computational representation of it. Image texture analysis is useful in a variety of applications and has been a subject of intense study by many researchers. In the present work, the effect of forming temperature on the forming behavior of aluminum and aluminum reinforced by 10 wt% SiC was studied by using image texture features after using the compression test which was done at an elevated temperature range of 300–550 °C and a constant strain rate of 0.024 s−1. The current study used a computer vision technique with Sum and Difference Histogram Matrices (GLSDM) to investigate the forming temperature of aluminum and aluminum/silicon carbide (Al and Al/Sic). The relationships between each GLSDM texture feature and the operation temperatures are discussed and the correlation coefficients are obtained. The results showed that some texture features have high correlation coefficients with high sensitivity to changes in temperature.
Mechanical failures in most cases originate from the exterior layers of the components. It is considerably effective to apply methods and treatments capable to improve the mechanical properties on component’s surface. Surface nanocrystallization produced by severe plastic deformation (SPD) processes such as severe shot peening (SSP) is increasingly considered in the recent years. However, artificial intelligence systems such as artificial neural network (ANN) as an efficient approach instead of costly and time consuming experiments is widely employed to predict and optimize the science and engineering problems in the last decade. In the present study the application of ANN in predicting of SSP effective parameters has been investigated and evaluated. The Back propagation (BP) error algorithm is used to network’s training. In order to train the ANN, experimental tests on AISI 1017 mild steel specimens were conducted and the data was gathered. Testing of the ANN is carried out using experimental data not used during training. Almen intensity, residual stress, crystallite size, full width at half maximum (FWHM) and hardness were modeled. Different networks with different inputs are developed for modeling of each mentioned parameters. The Almen intensity, hardness, crystallite size, FWHM and residual stress have least mean error respectively for the accomplished modeling. The comparison of obtained results of ANN’s response and experimental values indicates that the networks are tuned well and the ANN can be used to predict the SSP effective parameters and it can be an alternative way for calculating of parameters of this process.
The most widely used technologies for founding Al castings are sand casting and die casting (gravity casting; high pressure die casting; low pressure die casting; vacuum die casting; squeeze casting or squeeze forming). The lower cooling rate setting used for casting into a sand mould (sand casting) causes a coarse granular structure and lower values of mechanical properties. Higher cooling rate settings used for casting into a metallic mould (chill casting) causes fine-grained structures and higher values of mechanical properties. The present study provides information about the effect of casting into two different moulds on the fatigue properties of the heat treated AlSi9Cu3 cast alloy. Fatigue fracture surfaces were observed using a scanning electron microscope (SEM) after the fatigue test. The results show that the existence of casting defects and different morphologies of structural parameters (especially eutectic Si particles and Fe-rich intermetallic phases) has considerable influence on fatigue properties in both types of experimental materials. The results show that the fatigue lifetime is longer for samples casted into a metallic mould (chill casting) (average fatigue lifetime for 107 of cycles = 68 MPa) compared to casting the same materials into a sand mould (sand casting) (average fatigue lifetime for 107 cycles = 39 MPa).
The aim of this research is to study the effect of heat input on microstructure, impact and tensile strength properties of gas-metal-arc welded SKD 61 hot work tool steel by applying pulse current. Two steel plates with V groove at the connected edge, were welded under the condition of 150, 170 and 190 A of welding currents, 16–25 V of arc voltages and 1.5 mm/s of welding speed. A consumable copper-coated solid wire electrode was used in this welding process. The results showed that the martensite with retained austenite and dendrite structure of ferrite phases were found in the welded zones for all conditions. The hardness in the welded zone of three welding conditions were slightly increased with increasing heat input, and higher than that of the base metal, which resulted from martensite transformation. The absorbed energy of welded specimens during impact tests was increased with increasing heat input. The values of impact energies at the welding currents of 150, 170 and 190 A were 8.7, 10.0 and 14.0 J, respectively. Tensile strengths of all welded specimens were almost constant at 250 MPa. The tensile specimens were fractured at the heat affected zone.
Hydroxyapatite (HA) is one of the most significant calcium phosphate bio-ceramic which is used commercially in biomedical application due to its similar structure with natural bone, bioactivity, and stability in body fluid. HA has excellent biological properties, while plasma sprayed HA coatings have poor bond strength which makes it difficult to use HA coated implants under mechanical stress. Wollastonite (CS) is a calcium silicate based bioactive ceramic which is used in thermal spraying due to its higher bond strength than HA coatings, however it dissolves quicker than HA in simulated body fluid (SBF). The aim of this work is to produce HA-CS composite powder in order to increase bond strength of the coating. In this study, commercial CS and precipitated HA mixture suspension which involved wt.20% CS was prepared for spray drying (SD) application. HA-CS composite microspheres were granulated by spray drying to supply homogeneity of coating and carry powders to the plasma easily. Afterwards, HA and HA-CS composite microspheres were coated by plasma spraying on carbon steel. Results showed that HA-CS composite coatings have higher adhesion strength, while it decomposes easier to other calcium phosphates than pure HA coating. Additionally, HA-CS coating has higher rate of porosity and un-melted particles.
Friction stir welding (FSW) is a solid state joining process which utilizes the frictional heat of a high speed rotating tool to soften the adjoining sections and stirred/joined them together as one part without filler. In the FSW of pipe joining, a tool rotating at high speeds will start and stop at the same point in order to complete full weld cycle. The FSW of a small diameter pipe can cause secondary heating to occur at the start and stop point. Several pipe samples of 89 mm outside the diameter were prepared based on several specified welding parameters at a stationary position and completed the weld cycle. The Bridgeport 2216 CNC Milling Machine and a customised orbital clamping unit (OCU) were fully utilized for the sample’s preparation. This present study analysed the variation in hardness due to secondary heating for a small pipe diameter. The hardness varies between 18.7 HRB minimum to 33.6 HRB maximum, yielding to lower value due to this condition.
Aluminum alloys are used in many applications in which the advantages of high strength and low weight have a significant impact, industries such as; ship building, aviation, and transportation industry [1]. Friction stir welding (FSW) is a new non-flammable welding technique particularly well suited to aluminum alloys, though this technique is also used for other materials. Friction stir welding promises joints with low defects, fine microstructures, minimum phase transformation and low oxidation compared to conventional welding techniques [2]. Experiments for tensile and deflection tests were carried out and reported in this research paper. The base material used for friction stir welding was the similar AA 50833 Aluminum alloy. The material hardness has been tested to confirm the theory that the hardness increased with increase as the rotational speed of the tool increases, but decreases after attaining marginal speed. Deflections of friction stir welded specimens and base materials were compared and they exhibited almost similar trends at different spots in the welding nugget, heat affect zone and thermal material affected zone of all the specimens [3–5].
Swept friction stir spot welding, a derivative of friction stir welding is a solid-state process for joining materials by using frictional heat generated due to rotating tool along the weld line. The main objective of this study is to investigate the strength of the swept friction stir spot welded aluminum plate by changing the welding process parameters. In this paper, the joining was done on thin aluminum alloy plates using the Octaspot™ tool path with a radius of 10 mm. The samples were welded using a CNC milling machine. The study focuses on two process parameters which are the tool rotational speed and the welding traverse speed. The samples were analyzed on their shear strength and the results show that the higher the tool speed, the higher the shear strength is. However, when the rotational speed is increased, the shear strength shows a decreased pattern. The overall results are in good agreement with other published results.
The development and application of new materials brings, in connection with their technological machining, a number of new questions. Classical methods of machining are supplemented by new technologies. An abrasive water jet represents a universal flexible tool enabling the machining of all natural and artificial materials that are not damaged by direct contact with water. Great attention is paid to the study of the cut surface topography after abrasive water jet machining. The study of surface topography is important from the point of view of modelling and prediction of the topographic function of the abrasive water jet. On the basis of knowledge of the topographic function, we are able to optimise the technological parameters of the abrasive water jet machining process, which has an impact on the output, quality and price of the final product. The mechanism to remove material is an area which has not received much attention. In material disintegration, the mechanisms of cutting, plastic deformation, fatigue and fracture participate physically. By studying the surface topography we can better understand the process of abrasive water jet machining, specify the theory and correctly quantify the mechanism of material removal, which is the subject of this paper.
This paper is devoted to the comparison of the influence of injection moulding (IM) on heat transport phenomena and the mechanical properties of materials, with rapid prototyping (RP). The tested materials included ABS and polyurethane (PU). The results show decrease of both mechanical properties and thermal transport phenomena in the case of RP samples.
This work reports on the results of an experimental study examining the potential of the selective laser sintering process to produce a layer of specimen by using cobalt chromium molybdenum powder. A 300 W Neodymium-doped Yttrium Aluminium Garnet; Nd:Y3Al5O12 (Nd:YAG) laser machine was used in this laser sintering experiment in order to fabricate the cobalt chromium molybdenum specimen. The effects of the laser parameters such as laser power, scan speed, scan spacing, and pulse rate were investigated in this research, in which, the research started by evaluating sintered samples on a single track and continued with multiple tracks which created a single layer sintered sample. The evaluation of specimen characteristics focused on surface morphology, relative density and dimensional accuracy. There was a set power range and pulse rate applied in the single track test which was 30–75 W of laser power and 100, 150, 200, 250 Hz of pulse rate. The lasers applied in the single layer test were 55, 65, 75 W of laser power, 1, 3, 5 mm/s of scan speed and 0.5, 0.6, 0.7 mm of scan spacing. The result of the laser sintering experiment showed that laser power was inversely proportional to the porosity of the specimen, but directly proportional to the area percentage error of the specimen. While, the scan speed parameter was directly proportional to the porosity of the specimen, but inversely proportional to the area percentage error of the specimen. The purpose of this research was to find successful laser parameter conditions and create a process map for the laser sintering of cobalt chromium molybdenum powder material.
The effect of texturing Al2O3 and Al2O3/ZrO2 surfaces using femtosecond laser has been evaluated in terms of the roughness, wettability and microstructure of the substrate to increase growth efficiency and adhesion of hydroxyapatite. Femtosecond laser treatment of these materials causes phase transformation from alpha-alumina to gamma-alumina. Heat effects during femtosecond laser treatment causes the grains to be in the nanometer scale. Without heat effects, the grains are in the micrometer scale. The use of femtosecond laser permits control of the surface roughness of the alumina specimens. The higher the femtosecond laser energy, the higher is the wettability of the specimen and the total surface energy. Specimens with laser textured surfaces upon immersion in 1.5 SBF for 6 and 15 days revealed apatite layers well bonded to the substrate and without detachment. The adhesion of apatite to surfaces of specimens that were not textured with femtosecond laser was inadequate.
Powder-bed based additive manufacturing techniques, such as selective laser melting (SLM), are gaining in importance due to the opportunity to produce highly complex shapes. This offer new construction possibilities in the design. However, the surface of the produced SLM parts exhibit a high roughness which can affect the integrity and geometric tolerance. To reduce the surface roughness and to improve the mechanical properties of the outmost layer, laser polishing by re-melting the surface can be used. The present paper focus on the laser polishing of additive manufactured parts. This investigation contains measurement results of the initial and laser polished surfaces out of AlSi10Mg. The surfaces have been analyzed by roughness spectroscopy and white light interferometry. By utilizing a disk laser with a maximum power of 4 kW in combination with a 1-D scanner system, the initial surface roughness was reduced up to 92 %.
Laser beam machining (LBM) has proven its applications and advantages over almost all the range of engineering materials. It offers its competences from macro machining to micro and nano-machining of simple-to-complex shapes. The flipside of LBM is the existence of universal problems associated with its thermal ablation mechanism. In order to alleviate or reduce the inherent problems of LBM, a massive research has been done during the past decade and in turn build a relatively new route of laser-hybrid processes. The hybrid approaches in laser ablation have demonstrated much improved results in terms of material removal rate, surface integrity, geometrical tolerances, thermal damage, metallurgical alterations and many more. This chapter reviews the research work carried out so far in the area of LBM and its hybrid processes for different materials and shapes. The literature assessment is mainly classified into seven categories named as: (1) Introduction, (2) Laser Beam Machining (LBM), (3) Laser Assisted Machining (LAM), (4) Laser Chemical Machining/Etching (LCM/E), (5) Laser Assisted Electrochemical Machining (LAECM) and (6) Under-Water Laser Ablation (UWLA) and (7) Micro-channel Applications and Fabrication Techniques. The last part of this chapter discusses the research gaps and future research directions in the context of laser and laser-hybrid ablation.
This study examines the effect of functionalized multi‐walled carbon nanotube (CNTs) dispersion on mechanical properties of poly‐ether‐ether‐ketone–hydroxyapatite–carbon nanotubes (PEEK‐HAP‐CNTs) nanocomposite. The nanocomposites have been fabricated for biomedical applications using a melt processing at 400°C. The results showed that CNTs increase the effective contact area between PEEK and HAP in the nanocomposite. The addition of 0.1 wt% CNTs to the composite led to an elastic modulus and compressive strength improvement for 13% and 31% compared to PEEK‐HAP. The scanning electron microscopy images showed the microstructure of the composites. The results of cell attachment, alkaline phosphatase, spreading, proliferation, and alizarin red tests showed that adding CNT into the composite improved the function of MG‐63 cells. In conclusion, PEEK‐HA‐CNT is more suitable to be used as an implant material than PEEK and PEEK‐HA composites.
Full-text available
An effective technique, genetic-feedforward sliding mode-fractional PI controlled buck inverter used for super-precision machining of composite materials is proposed. The obstruction using sliding mode control (SMC) is due to the strong chattering that severely limits its practical applicability. The chattering yields high voltage distortion in buck inverter output, thus degrading stability and reliability of super-precision machining of composite materials. The modification structure to fractional PI has been established through the plant extending way so that the chattering is diminished and better flexibility in adjusting system response can be provided. The feedforward compensator improves the dynamics response further. The genetic algorithm (GA) can be adopted for determining optimal fractional proportional-integral (FPI) parametric values. With this control technique, the TI microprocessor-based buck inverter is implemented, and then experiments illustrate that the presented technique produces less steady-state inaccuracy, chattering attenuation, loading interference rejection and parametric variation removal.
Conference Paper
Based on progress in the field of additive manufacturing optical components can now be printed with rapid prototyping technologies. In this contribution the possibilities of rapid prototyping for optical metrology are exemplified by the fabrication of miniaturized reflectors and the construction of a miniaturized metrology system designed for an industrial metrology application. Focusing on the manufacturing and post processing steps the process chain to fabricate the miniaturized mirror is described. This includes an evaluation of the mirror based on roughness measurements. The reflectors are later utilized in a miniaturized sensor system to scan the interior of small pipes. The additively manufactured mirror is used in the metrology system to create a defined sampling signal within the cavity. Thereby the sensor system generates a point cloud of the internal surfaces using a 3D acquisition algorithm based on the laser triangulation principle. Part of this contribution will be the setup, the 3D acquisition and calibration principle as well as an evaluation of the metrology system. To optimize the point cloud acquisition three different hardware setups were designed using different cameras and calibration algorithms. These three approaches are evaluated and compared.
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