Showing papers in "Journal of Materials Processing Technology in 2007"
TL;DR: A review of the magnetic properties, characteristics, processing and applications of soft magnetic composite materials is presented in this paper, where the authors describe soft magnetic composites (SMCs) as ferromagnetic powder particles surrounded by an electrical insulating film.
Abstract: Soft magnetic composites (SMCs), which are used in electromagnetic applications, can be described as ferromagnetic powder particles surrounded by an electrical insulating film. SMC components are normally manufactured by conventional PM compaction combined with new techniques, such as two step compaction, warm compaction, multi-step and magnetic annealing followed by a heat treatment at relatively low temperature. These composite materials offer several advantages over traditional laminated steel cores in most applications. The unique properties include three-dimensional (3D) isotropic ferromagnetic behavior, very low eddy current loss, relatively low total core loss at medium and high frequencies, possibilities for improved thermal characteristics, flexible machine design and assembly and a prospect for greatly reduced weight and production costs. With expanded applications of soft magnetic composite materials expected in the future, a review of the magnetic properties, characteristics, processing and applications of SMCs is presented in this article.
801 citations
TL;DR: In this article, the influence of the energy density on physical and mechanical properties of parts produced using polyamide was investigated. And the effect of part orientation during the build was examined, and the trendlines which link build settings to resulting part properties, and hence to fabricate customised parts with predetermined properties.
Abstract: Customised properties of parts manufactured using the selective laser sintering process are achievable by variation of build parameters. The energy density, controlled by laser power, distance between scan lines and speed of the laser beam across the powder bed, all have a very strong influence on the density and the mechanical behaviour of the parts. The present paper investigates the influence of the energy density on physical and mechanical properties of parts produced using polyamide. Additionally, the effect of part orientation during the build is examined. Knowledge of the influence of these parameters allows one to establish trendlines which link build settings to resulting part properties, and hence to fabricate customised parts with predetermined properties.
505 citations
TL;DR: In this paper, the authors present a literature survey on the machining of composite materials, more specifically on drilling of glass and carbon fiber reinforced plastics, and assess the quality of the holes produced.
Abstract: The use of polymeric composite materials has increased considerably over the last decade and, as a consequence, the number of papers focused on relevant aspects concerning the machinability of such materials has also increased. The principal aim of this work is to present a literature survey on the machining of composite materials, more specifically on drilling of glass and carbon fibre reinforced plastics. Aspects such as tool materials and geometry, machining parameters and their influence on the thrust force and torque are investigated. Additionally, the quality of the holes produced is also assessed, with special attention paid to the delamination damage. The results indicated that despite the fact that some aspects, such as the effect of cutting parameters and tool geometry on the quality of the hole have been extensively studied over the last years, the phenomena associated to shearing of polymeric composite materials require additional studies in order to allow a better understanding of the behaviour of this category of materials when subjected to cutting.
464 citations
TL;DR: In this article, the compressive properties of 3D printer, Fused Deposition Modeling (FDM) and Nanocomposite Deposition System (NCDS) were measured by measuring compressive strengths.
Abstract: Rapid prototyping (RP) technologies provide the ability to fabricate initial prototypes from various model materials. Fused deposition modeling (FDM) and 3D printer are commercial RP processes while nano composite deposition system (NCDS) is an RP testbed system that uses nano composites materials as the part material. To predict the mechanical behavior of parts made by RP, measurement of the material properties of the RP material is important. Each process was characterizes by process parameters such as raster orientation, air gap, bead width, color, and model temperature for FDM. 3D printer and NCDS had different process parameters. Specimens to measure compressive strengths of the three RP processes were fabricated, and most of them showed anisotropic compressive properties.
405 citations
TL;DR: In this paper, the authors presented a study of the Taguchi design application to optimize surface quality in a CNC face milling operation, which included feed rate, spindle speed and depth of cut as control factors, and the noise factors were the operating chamber temperature and the usage of different tool inserts in the same specification.
Abstract: This paper presents a study of the Taguchi design application to optimize surface quality in a CNC face milling operation. Maintaining good surface quality usually involves additional manufacturing cost or loss of productivity. The Taguchi design is an efficient and effective experimental method in which a response variable can be optimized, given various control and noise factors, using fewer resources than a factorial design. This study included feed rate, spindle speed and depth of cut as control factors, and the noise factors were the operating chamber temperature and the usage of different tool inserts in the same specification, which introduced tool condition and dimensional variability. An orthogonal array of L9(34) was used; ANOVA analyses were carried out to identify the significant factors affecting surface roughness, and the optimal cutting combination was determined by seeking the best surface roughness (response) and signal-to-noise ratio. Finally, confirmation tests verified that the Taguchi design was successful in optimizing milling parameters for surface roughness.
391 citations
TL;DR: In this paper, a combining artificial neural network and genetic algorithm (ANN/GA) method is proposed to optimize the injection molding process, where a BP neural network model is developed to map the complex nonlinear relationship between process conditions and quality indexes of the injection molded parts, and a GA is used in the process conditions optimization with the fitness function based on an ANN model.
Abstract: Injection molding is the most widely used process in manufacturing plastic products. Since the quality of injection molded plastic parts are mostly influenced by process conditions, how to determine the optimum process conditions becomes the key to improving the part quality. In this paper, a combining artificial neural network and genetic algorithm (ANN/GA) method is proposed to optimize the injection molding process. In this method, a BP neural network model is developed to map the complex non-linear relationship between process conditions and quality indexes of the injection molded parts, and a GA is used in the process conditions optimization with the fitness function based on an ANN model. The combining ANN/GA method is used in the process optimization for an industrial part in order to improve the quality index of the volumetric shrinkage variation in the part. The results show that the combining ANN/GA method is an effective tool for the process optimization of injection molding.
361 citations
TL;DR: In this article, aqueous solution with various pH and peptizing the resultant suspension has been applied for preparation of the TiO2 nanopowder with narrow size distribution, and the influence of pH on the particle size and morphology of prepared powder has been evaluated.
Abstract: Titanium dioxide nanoparticles have been prepared by hydrolysis of titanium isopropoxide. Aqueous solution with various pH and peptizing the resultant suspension has been applied for preparation of the TiO2 nanopowder with narrow size distribution. The influence of pH on the particle size and morphology of prepared powder has been evaluated. Synthesized powder is characterized by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Experimental results have shown that the as-prepared powders have entirely consisted with anatase crystalline phase. Only powder acquired from an acidic solution has fine particle size with spherical morphology. The anatase to rutile transformation occurred at temperatures lower than 600 °C.
340 citations
TL;DR: In this article, the effect of stacking sequence on tensile, flexural and interlaminar shear properties of untreated woven jute and glass fabric reinforced polyester hybrid composites has been investigated experimentally.
Abstract: Effect of stacking sequence on tensile, flexural and interlaminar shear properties of untreated woven jute and glass fabric reinforced polyester hybrid composites has been investigated experimentally. Laminates were fabricated by hand lay-up technique in a mold and cured under light pressure for 1 h, followed by curing at room temperature for 48 h. All the laminates were made with a total of 10 plies, by varying the number and position of glass layers so as to obtain six different stacking sequences. One group of all jute laminate was also fabricated for comparison purpose. Total fibre weight fraction was maintained at 42%. Specimen preparation and testing was carried out as per ASTM standards. Tests were conducted on MTS 810 Material Test System at room temperature using automatic data acquisition software Test Works-II. The results indicated that the properties of jute composites can be considerably improved by incorporation of glass fibre as extreme glass plies. The layer sequence has greater effect on flexural and interlaminar shear properties than tensile properties. An overall comparison between the properties of all the laminates revealed that the hybrid laminate with two extreme glass plies on either side is the optimum combination with a good balance between the properties and cost.
332 citations
TL;DR: In this article, minimal quantity lubrication (MQL) was applied to finish-turning of a nickel-base superalloy, Inconel 718, with three different types of coated carbide tools.
Abstract: Minimal quantity lubrication (MQL) was applied to finish-turning of a nickel-base superalloy, Inconel 718, with three different types of coated carbide tools. Three selected coatings were TiCN/Al2O3/TiN (CVD), TiN/AlN superlattice (PVD) and TiAlN (PVD). Cutting speeds were set at relatively higher values: 1 and 1.5 m/s. At a cutting speed of 1.0 m/s, TiCN/Al2O3/TiN coating in MQL cutting exhibited the best performance while TiN/AlN superlattice coating in MQL cutting exhibited the second best performance. The longest tool life was attained by TiCN/Al2O3/TiN coating in wet cutting, but the surface finish was not good. It was found that there is the optimum air pressure life in finish-turning of Inconel 718 with MQL. It was also found in an experiment using argon as a carrier gas of oil mist that the carrier gas of MQL plays an important role for cooling the cutting point. As the cutting speed was increased to 1.5 m/s, the tool lives were drastically shortened. In addition, the surface finish in MQL cutting increased because the worn tool flank surface became rough.
280 citations
TL;DR: This study attempts to model and optimize the complex electrical discharge machining process using soft computing techniques, and a pareto-optimal set has been predicted in this work.
Abstract: Present study attempts to model and optimize the complex electrical discharge machining (EDM) process using soft computing techniques. Artificial neural network (ANN) with back propagation algorithm is used to model the process. As the output parameters are conflicting in nature so there is no single combination of cutting parameters, which provides the best machining performance. A multi-objective optimization method, non-dominating sorting genetic algorithm-II is used to optimize the process. Experiments have been carried out over a wide range of machining conditions for training and verification of the model. Testing results demonstrate that the model is suitable for predicting the response parameters. A pareto-optimal set has been predicted in this work.
254 citations
TL;DR: In this paper, the as-synthesized magnetic iron oxides nanoparticles were characterized by XRD, TEM, TGA and AGM and the results showed that crystallize, physical and magnetic sizes of magnetic iron oxide nanoparticles are less than 10nm which were within the superparamagnetic size range.
Abstract: Water in oil microemulsion system was used to prepare magnetic iron oxide nanoparticles. Two different volumetric ratios of Fe2+ and OH− (1:1 and 2:1) were investigated. The as-synthesized magnetic iron oxide nanoparticles were characterized by XRD, TEM, TGA and AGM. The XRD, TEM and AGM results showed that crystallize, physical and magnetic sizes of magnetic iron oxide nanoparticles were less than 10 nm which were within the superparamagnetic size range. The magnetization curve also showed no hysterisis loop at room temperature which indicated superparamagnetic behavior. Magnetic iron oxides nanoparticles were also prepared by Massart's procedure. The saturation magnetization of magnetic iron oxides nanoparticles prepared by w/o microemulsion system was higher while the crystallize size was smaller. This showed that magnetic iron oxides nanoparticles could be tailored by different preparation procedures.
TL;DR: In this paper, the effects of sliding distance, Al 2 O 3 particle content and size, SiC abrasive grit size and wear load on the wear properties of the composites were systematically investigated.
Abstract: Sliding wear tests on 10, 20 and 30 wt.% Al 2 O 3 particles reinforced 2024 aluminium alloy composites fabricated by a vortex method were carried out by using a pin-on-disc abrasion test apparatus where the sample slid against SiC abrasive papers of 20 (600 grit), 46 (320 grit) and 60 μm (240 grit) under the loads of 2 and 5 N at the room conditions, and the effects of sliding distance, Al 2 O 3 particle content and size, SiC abrasive grit size and wear load on the wear properties of the composites were systematically investigated. For determination of the wear mechanisms of the composites, the worn surfaces were examined using scanning electron microscopy (SEM). It has been found that the wear resistance of the composites was significantly larger than that of the aluminium alloy, and increased with increasing Al 2 O 3 particles content and size, and decreased with increasing the sliding distance, the wear load and the abrasive grit size. The effect of Al 2 O 3 particle size on the wear resistance was more significant than that of the particle content.
TL;DR: In this paper, multiple linear regression models and neural network models are developed for predicting surface roughness and tool flank wear in finish turning of AISI D2 steels using ceramic wiper (multi-radii) design inserts.
Abstract: Tool nose design affects the surface finish and productivity in finish hard turning processes. Surface finishing and tool flank wear have been investigated in finish turning of AISI D2 steels (60 HRC) using ceramic wiper (multi-radii) design inserts. Multiple linear regression models and neural network models are developed for predicting surface roughness and tool flank wear. In neural network modelling, measured forces, power and specific forces are utilized in training algorithm. Experimental results indicate that surface roughness Ra values as low as 0.18–0.20m are attainable with wiper tools. Tool flank wear reaches to a tool life criterion value of VBC = 0.15 mm before or around 15 min of cutting time at high cutting speeds due to elevated temperatures. Neural network based predictions of surface roughness and tool flank wear are carried out and compared with a non-training experimental data. These results show that neural network models are suitable to predict tool wear and surface roughness patterns for a range of cutting conditions. © 2007 Elsevier B.V. All rights reserved.
TL;DR: In this paper, a modified Taguchi method was used for both detraining the optimum settings of machine parameters and combining multiple quality characteristics into one integrated numerical value called Grey relational grade or rank.
Abstract: This paper presents and demonstrates the effectiveness of optimizing multiple quality characteristics of Nd:YAG laser welded titanium alloy plates via Taguchi method-based Grey analysis. The modified algorithm adopted here was successfully used for both detraining the optimum settings of machine parameters and for combining multiple quality characteristics into one integrated numerical value called Grey relational grade or rank. The essential machining parameters were identified as (1) shielding gas, (2) laser energy, (3) traveling speed of the workpiece during welding, (4) focusing position, (5) frequency of the impulse laser, and (6) pulse shape of the primary laser beam. Furthermore, the multiple quality characteristics required herein included: (1) high ultimate tension stress, (2) small heat-affected zone, (3) large welding depth to width ratio, and (4) low surface roughness following laser welding. Titanium alloy plates were butt welded under controlled machine parameter settings, machined, and above quality characteristics were measured. The optimized machine parameter settings clearly improved the quality characteristics of welded plates compared to quality levels achieved for conventional machine parameter settings. The tensile stress increased (922 ± 53 to 965.5 ± 46.5 MPa) and the heat-affected zone decreased (0.27–0.22 mm) while the welding depth to width ratio remained the same at 0.76. The new approach increased the surface roughness from R max of 14.2 to 34.4 μm.
TL;DR: In this article, the effects of cryogenic treatment on the mechanical properties and microstructures of AISI 4340 steel were investigated, including rotating fatigue, impact and hardness.
Abstract: This experimental study investigated the effects of cryogenic treatment on the mechanical properties and microstructures of AISI 4340 steel. Mechanical tests, including rotating fatigue, impact and hardness were carried out, after various heat treating conditions and the results were compared. Fracture features of specimens were also compared. It was shown that in general, hardness and fatigue strength of the cryogenically treated specimens were a little higher whereas the toughness of the cryogenically treated specimens was lower when compared to that of the conventionally treated steel. Neutron diffraction showed that the transformation of retained austenite to martensite occurred which, along with possible carbide formation during tempering, is a key factor in improving hardness and fatigue resistance of the cryogenically treated specimens.
TL;DR: Powder mixed electric discharge machining (PMEDM) is one of the recent innovations for the enhancement of capabilities of EDM process as mentioned in this paper, which reduces the insulating strength of the dielectric fluid and increases the spark gap between the tool and workpiece.
Abstract: Powder mixed electric discharge machining (PMEDM) is one of the recent innovations for the enhancement of capabilities of EDM process. In PMEDM, the electrically conductive powder is mixed in the dielectric of EDM, which reduces the insulating strength of the dielectric fluid and increases the spark gap between the tool and workpiece. As a result, the process becomes more stable, thereby, improving the material removal rate (MRR) and surface finish. Moreover, the surface develops high resistance to corrosion and abrasion. This paper presents a tutorial introduction, comprehensive history and review of research work carried out in the area of PMEDM. The machining mechanism, current issues, applications and observations are also discussed.
TL;DR: In this article, a wide recognition of the research efforts in this field is presented, taking into account some general considerations on the difference sources of shape and dimensional errors, as well as the influence of the most relevant parameters.
Abstract: The paper is aimed to discuss some relevant issues concerning an innovative sheet metal forming technology, namely Single Point Incremental Forming. The advantages of this technology are addressed, including its capability to provide effective answers to some impellent industrial requirements: process flexibility, strong customer orientation, production of highly differentiated goods at low industrial costs. As well some relevant drawbacks are highlighted, mainly as concerns the level of accuracy permitted by the process. A wide recognition of the research efforts in this field is presented, taking into account some general considerations on the difference sources of shape and dimensional errors, as well as the influence of the most relevant parameters. Finally, some strategies for error minimisation are presented and discussed.
TL;DR: In this article, the effect of various process parameters on thermal histories, resulting microstructure and properties of commercial AZ31B-H24 magnesium alloy sheets is investigated and it is shown that FSP leads to finer and more homogenized grain structure.
Abstract: Recently friction stir processing (FSP) has emerged as an effective tool for enhancing sheet metal properties through microstructure modification. Significant grain refinement and homogenization can be achieved in a single FSP pass leading to improved formability, especially at elevated temperatures. FSP is a solid-state process where the material within the processed zone undergoes intense plastic deformation resulting in dynamically recrystallized grain structure. Most of the research conducted on FSP focuses on aluminum alloys. Despite the potential weight reduction that can be achieved using magnesium alloys, very little is reported on FSP of magnesium alloys. In this work, we examine the possibility of using FSP to modify the microstructure and properties of commercial AZ31B-H24 magnesium alloy sheets. The effect of various process parameters on thermal histories, resulting microstructure and properties are investigated. Preliminary results are promising and it is shown that FSP leads to finer and more homogenized grain structure.
TL;DR: In this paper, the precursors were adjusted to a basic (pH 10) and acidic medium before hydrothermal treatment at various durations of 6, 12, 18, and 24 hours at 250°C using a Teflon-lined hydrotherm bomb.
Abstract: Nano-crystalline particles of CeO2 have been synthesized via a low temperature hydrothermal synthesis process. Two types of precursors were studied—cerium hydroxide and ceria acetate. The precursors were adjusted to a basic (pH 10) and acidic (pH 4) medium before hydrothermal treatment at various durations of 6, 12, 18, and 24 h at 250 °C using a Teflon-lined hydrothermal bomb. The synthesized samples were characterized using DTA/TGA, XRD and TEM. Based on the characterization results, both precursor systems produced crystalline ceria nano-particles after 6 h of hydrothermal synthesis at 250 °C. The average crystallite sizes were 6 and 15 nm for the hydroxide and acetate system, respectively. The acetate precursor system appeared to produce better particles in terms of crystallinity and morphology. Based on the DTA/TGA analysis, hydrothermal synthesis had been effective in reducing the amount of intermediate products. With increasing hydrothermal treatment duration of up to 24 h, the samples did not exhibit a remarkable improvement in properties. The synthesized nano-particles were subsequently heat treated at 500 and 1000 °C for 2 h. After the heat treatment, enhanced crystallinity and growth in crystallite size was observed, but particles appeared more agglomerated.
TL;DR: In this paper, the effect of cutting speed, feed rate, depth of cut and tool cutting edge geometry on cutting forces, surface roughness and surface damage in high-speed turning of Inconel 718 using PCBN tools has been discussed.
Abstract: Knowing the stringent operating conditions to which superalloys are subjected to in automobile, aerospace and gas turbine industries, their efficient machining and generation of machined surfaces with high integrity assumes a lot of importance. Therefore, this paper presents an experimental investigation into the effect of various process and tool-dependent parameters on cutting forces, an indirect measure of machined surface integrity besides a detailed microstructural analysis of the machined surface damage, in high-speed machining of superalloy Inconel 718. Accordingly, the effect of cutting speed, feed rate, depth of cut and tool cutting edge geometry on cutting forces, surface roughness and surface damage in high-speed turning of Inconel 718 using PCBN tools has been discussed. The input parameters were varied as: V = 125–475 m min −1 , f = 0.05–0.15 mm rev −1 , d = 0.50–1.0 mm and edge geometry as: 30° chamfer, 20° chamfer and 30° chamfer plus honed. The results show that the radial and feed force components are almost equal and the main cutting force component is two to three times that of feed and radial force components. The honed plus chamfered cutting edge was influential in reducing cutting forces significantly. It was noted that specimens showing larger cutting forces generated poor surface finish as well as extensive surface damage.
TL;DR: In this article, a 3-D thermal elastic plastic finite element computational procedure is developed to precisely predict welding deformation by numerical method, and the simulated results are in a good agreement with the experimental measurements.
Abstract: Fillet weld is the most common weld type used in the fabrication of structural members in shipbuilding, automobile and other industries. Fillet-welded joints usually suffer from various welding deformation patterns, such as longitudinal shrinkage, transverse shrinkage, angular distortion and longitudinal bending. Welding deformation has negative effects on fabrication accuracy, external appearance and various strengths of the welded structures. In this study, experiments are performed to investigate the characteristics of welding deformation in the fillet-welded joint. In order to precisely predict welding deformation by numerical method, a 3-D thermal elastic plastic finite element computational procedure is developed. The simulated results are in a good agreement with the experimental measurements. The influence on welding deformation of the flange thickness is investigated by experiment and numerical simulation. In addition, the generation mechanism of angular distortion is clarified through numerical simulation.
TL;DR: In this article, the authors used the Taguchi method to test the warpage properties of a thin plate with dimension 120mm×50mm/1.5mm and showed that the most effective factor on the warpages is the melt temperature.
Abstract: Plastic injection moulding is one of the most important polymer processing operations in the plastic industry today. However, lack of skill in mould making and injection moulding machine control will lead to defective plastic product. Warpage is one type of defect that usually appears in products with thickness less than 1 mm. This project is going to fabricate a mould that produced a thin plate with dimension 120 mm × 50 mm × 1 mm. The thin plate will be used for warpage testing. In mould fabrication, the mould base that purchase will be machined and assembled. After that, the mould is fixed on the injection moulding machine. The machine setting should be made to produce the product. Then, the product will be used for testing on the effective factors in warpage problem by applying the experimental design of Taguchi method. From the results, it shows that the most effective factor on the warpage is melt temperature. The filling time only slightly influenced on the warpage. The optimum parameters that can minimize the warpage defect are melt temperature (240 °C), filling time (0.5 s), packing pressure (90%) and packing time (0.6 s).
TL;DR: In this paper, a signal-to-noise ratio is employed to analyze the influence of various parameters on peel up and push down delamination factor in drilling of glass fiber reinforced plastic (GFRP) composite laminates.
Abstract: Machining processes are generally used to cut; drill, or contour composite laminates for building products. In fact, drilling is one of the most commonly used manufacturing processes to install fasteners for assembly of laminate composites. The material anisotropy resulting from fiber reinforcement heavily influences the machinability during machining. Machining of fiber reinforced plastic (FRP) components is often needed in spite of the fact that most FRP structures can be made to near-net shape and drilling is the most frequently employed secondary machining process for fiber reinforced materials. Therefore, the precise machining needs to perform to ensure dimensional stability and to obtain a better productivity of the component. The drilling parameters and specimen parameters evaluated were speed, feed rate, drill size and specimen thickness. A series of experiments were conducted using TRIAC VMC CNC machining center to machine the composite laminate specimens at various cutting parameters and material parameters. The measured results of delamination at the entry and exit side of the specimen were measured and analyzed using commercial statistical software MINITAB14. The experimental results indicated that the specimen thickness, feed rate and cutting speed are reckoned to be the most significant factors contributing to the delamination. A signal-to-noise ratio is employed to analyze the influence of various parameters on peel up and push down delamination factor in drilling of glass fibre reinforced plastic (GFRP) composite laminates. The main objective of this study is to determine factors and combination of factors that influence the delamination using Taguchi and response surface methodology and to achieve the optimization machining conditions that would result in minimum delamination. From the analysis it is evident that among the all significant parameters, specimen thickness and cutting speed have significant influence on peel up delamination and the specimen thickness and feed have more significant influence on push down delamination. Confirmation experiments were conducted to verify the predicted optimal parameters with the experimental results, good agreement between the predicted and experimental results obtained to be of the order of 99%.
TL;DR: In this article, a study of the influences of EDM parameters on surface roughness for machining of 40CrMnNiMo864 tool steel (AISI P20) which is widely used in the production of plastic mold and die.
Abstract: Electrical discharge machining (EDM) is one of the important non-traditional machining processes and it is widely accepted as a standard machining process in the manufacture of forming tools to produce molds and dies. Since its introduction to manufacturing industry in late 1940s, EDM became a well-known machining method. The method is based on removing material from a workpiece by means of a series of repeated electrical discharges, produced by electric pulse generators at short intervals, between an electrode (tool) and a part being machined in dielectric fluid medium. This paper is devoted to a study of the influences of EDM parameters on surface roughness for machining of 40CrMnNiMo864 tool steel (AISI P20) which is widely used in the production of plastic mold and die. The selected EDM parameters were pulsed current (8, 16 and 24 A), pulse time (2, 3, 4, 6, 12, 24, 48 and 100 μs) and pulse pause time (2 and 3 μs). It was observed that surface roughness of workpiece and electrode were influenced by pulsed current and pulse time, higher values of these parameters increased surface roughness. Lower current, lower pulse time and relatively higher pulse pause time produced a better surface finish.
TL;DR: In this article, the effects of three processing and one geometric factor on the surface quality of micro-features in three different polymer materials were investigated, in particular, the following factors are considered: barrel temperature, mould temperature, injection speed and distance between micro features.
Abstract: Micro-injection moulding is one of the key technologies for micro-manufacture because of its mass-production capability and relatively low component cost. The surface quality in replicating micro-features is one of the most important process characteristics and constitutes a manufacturing constraint in applying injection moulding in a range of micro-engineering applications. This research investigates the effects of three processing and one geometric factor on the surface quality of micro-features in three different polymer materials. In particular, the following factors are considered: barrel temperature, mould temperature, injection speed and distance between micro-features. In this investigation, the mould temperature was set in the conventional range. The study revealed that in general, increasing the barrel temperature, mould temperature and the injection speed improves the polymer melt fill in micro-cavities. However, the effects of these factors on the process replication capabilities are not consistent for different polymer materials, and could be adverse in specific conditions. Varying the distance between micro-features does not affect the melt fills.
TL;DR: In this paper, the effects of superimposing ultrasonic vibrations on the lower platen in tension and compression tests of aluminium were investigated and it was shown that the experimentally derived stress-strain data from these tests does not satisfy the description of a simple oscillatory stress superposition model.
Abstract: This paper presents a study of the effects of superimposing ultrasonic vibrations on the lower platen in tension and compression tests of aluminium. By measuring the oscillating force response as well as the static force, it is shown that the experimentally derived stress–strain data from these tests does not satisfy the description of a simple oscillatory stress superposition model. Finite element models of tension and compression tests are created and a description of the contact friction condition is included for the compression test model. By incorporating ultrasonic vibration of the lower platen for an interval during plastic deformation, the finite element model predicts that the stress–strain relationship satisfies a simple oscillatory stress superposition model. The finite element models are then developed further to investigate the predicted stress–strain relationship if a softer material model is incorporated only during the interval of ultrasonic excitation. For the tension test model, this allows the predicted stress–strain data to match the experimentally derived data. For the compression test model, by combining a softer material model description with a change in the coefficient of friction at the contact surface, only during the interval of ultrasonic excitation, the finite element model predicted stress–strain data matched the experimentally derived stress–strain data. The study indicates that it is not sufficient to explain the effects of ultrasonic excitation in metal forming processes only in terms of oscillatory stress superposition and contact friction.
TL;DR: In this article, an experimental platform capable of measuring forces in process during an incremental forming procedure is described and some of the earliest measurements of forces in incremental forming with the changes induced on the measured load are reported.
Abstract: An experimental platform capable of measuring forces in process during an incremental forming procedure is described and some of the earliest measurements of forces in incremental forming with the changes induced on the measured load are reported. Using a table type force dynamometer with incremental forming fixture mounted on top, three components of force were measured throughout the forming process. They were found to vary as the parts were made. The reported experimental test program was mainly focused on the influence of four different process parameters on the forming forces: the vertical step size between consecutive contours, the diameter of the tool, the steepness of the parts’ wall and the thickness of the sheet metal being formed. The effect of lubrication and the geometry of the test part in the incremental forming process were investigated by a set of initial experiments. Part failure prediction based on the shape of the force curve is explained. For the tested materials, analytical results demonstrating the relationship between the respective process parameters and the induced forces are presented in this paper.
TL;DR: In this paper, the influence of interaction time in continuous drive friction welding on microstructure and tensile properties is studied and it is shown that increased interaction time led to decrease in strength in eutectoid forming and insoluble systems and improved strength in soluble systems.
Abstract: Joining of dissimilar metals is one of the most essential needs of industries. Dissimilar metal combinations Fe–Ti, Cu–Ti, Fe–Cu, Fe–Ni and Cu–Ni have been investigated in the present work as Fe, Cu, Ti and Ni are the most extensively used materials in engineering application in the alloyed form. Metals are taken in commercially pure form so as to understand the basic mechanism of joining, which can be then employed to complex alloy systems. Influence of interaction time in continuous drive friction welding on microstructure and tensile properties is studied. Increased interaction time led to decrease in strength in eutectoid forming and insoluble systems and improved strength in soluble systems. Mechanical transport of the material is predominant at the peripheral region of the weld.
TL;DR: In this article, the performance of uncoated-WC/Co and TiAlN-PVD coated-carbide twist drills were investigated when drilling titanium alloy, Ti-6Al4V.
Abstract: In this paper, the performance of uncoated-WC/Co and TiAlN–PVD coated-carbide twist drills were investigated when drilling titanium alloy, Ti–6Al4V. The effect of cutting speed on tool wear, tool life and surface finish of the hole when drilling using coolant were reported. Results showed that non-uniform flank wear, chipping and catastrophic failure were the dominant modes of tool failure for both coated- and uncoated-drills. It was found that at all cutting speeds tested, TiAlN-coated-drill significantly outperformed uncoated-drill in terms of tool life and surface finish. The highest tool life recorded for TiAlN-coated-drill was 7.8 min after drilling the 25th hole at the lowest cutting speed of 25 m/min and feed of 0.06 mm/rev. The effect of cutting speed on the performance of the uncoated-carbide drill was less significant at all cutting speed tested when all the drills failed prematurely with recorded tool lives of less than 1 min.
TL;DR: In this paper, the effectiveness of polycrystalline diamond inserts (PCD) has been compared to that of uncoated tungsten carbide-cobalt inserts in machining titanium alloy Ti-6Al-4V, with respect to the applicable cutting speed ranges, metal removal per tool life and tool wear rates, tool wear morphology, surface finish, chip segmentation and chatter phenomena.
Abstract: Titanium and its alloys have found wide application in the aerospace, biomedical and automotive industries owing to their good strength-to-weight ratio and high corrosion resistance. However, these alloys have very poor machinability, which is attributed to their inherent high strength maintained at elevated temperature and low thermal conductivity leading to high cutting temperatures. Chips formed are serrated in nature as a result of a cycle of compression and adiabatic plastic shear phases in the chip formation process, causing high fluctuations of cutting force acting over a small chip tool contact area (about one-third that in the case of steel). High chemical reactivity of titanium at high-elevated temperatures, especially with titanium-based tools or coatings limits their application during machining. So the strategy of titanium machining is to use tools which show less reactivity, has higher thermal conductivity to increase the chip–tool contact length and effectively take away the generated heat and to use tougher and harder tools grades which could withstand the dynamic action of the cutting force. The recommended tools for many years had been the uncoated tungsten carbide grade K. But these tools cannot be used at high cutting speed since they too fail due to dynamic normal component of cutting force that acts on the very small contact area of the tool and high cutting temperature, leading to intensive diffusion and superficial plastic deformation, causing catastrophic failure of the tool. In this work, the effectiveness of polycrystalline diamond inserts (PCD) has been compared to that of uncoated tungsten carbide–cobalt inserts in machining titanium alloy Ti–6Al–4V. The comparison has been made with respect to the applicable cutting speed ranges, metal removal per tool life and tool wear rates, tool wear morphology, surface finish, chip segmentation and chatter phenomena.