Materials Science Forum Vols. 773-774

Abstract: In shot peening, bombarding the surface with steel shot propelled at high velocity causes plastic deformation of surface. The process with the characteristic deformation was applied to joining process. Our approach has been applied to the butt joining of the dissimilar metal sheets. In this method, however, the joint strength was lower than the flow stress of base metal. The modified joining processing was being carried out to improve the bondability. In the present study, the joining of dissimilar metal sheets using a shot peening process was investigated to improve the bondability. In the joined section, the edge of the joint area of the sheets were slit using a laser. In this method, the edges of the sheet are overlapped the other sheet. When the connection is peened, the material undergoes large plastic deformation near the surface due to the collision of shots. In this process, particularly noteworthy is the plastic flow near surface layer. The edges of the sheet are joined to the other sheet, thus two sheets can be joined each other. In the experiment, the shot peening treatment was performed by using an air-type peening machine. The shots used were made of high carbon cast steel. Air pressure was 0.6 MPa and peening time was in the range of 30-240s. The metal sheets were commercial low-carbon steel, stainless steel, pure aluminium, aluminium alloy, and pure copper. The effects of processing conditions on the bondability were mainly examined. It was found that the present method was effective for joining of dissimilar metal sheets.

Abstract: The rheological behavior of feedstock needs to be examined for manufacturing parts without defects by micro powder injection molding (μPIM). In this study, submicron tungsten carbide (WC) and cobalt (Co) were milled for several hours. The distribution and morphology of the powder mixture were analyzed by laser diffraction and scanning electron microscopy. After measurement of critical powder loading, cemented tungsten carbide (WCCo) powder was mixed with a thermoplastic/paraffin wax binder with a powder loading volume from 50% to 52% to obtain feedstock. The flow properties of the WCCo feedstock were evaluated using a capillary rheometer at different temperatures. It was found that feedstock exhibit a pseudoplastic flow behavior, which is one of the main requirements for μPIM. Feedstock is also shown to be highly sensitive to temperature at high powder loading. Low powder loading led to low viscosity at a high shear rate that cannot be used in μPIM because it results in powder and binder separation.

Abstract: The implementation of Rapid Prototyping technology in industrial and manufacturing processes has revolutionized new product development process. However, there are some restrictions of RP parts, primarily in the geometrical accuracy, shrinkage and distortion after the typical post processing method. This paper presents the experimental study using specially designed specimen to determine the effect of thermal parameter used on the RP part built using 3D printer ProJet SD 3000. The parameters of concern are geometrical dimension, shrinkage and flatness. The mechanical properties of the specimen have been determined using the tensile testing machine in order to indentify the effect of post processing temperature on the strength of the specimens. It is expected that the post processing temperature will play the major role in maintaining the geometrical accuracy of the RP products since heating used will lead to increase the shrinkage, warpage and reduce the accuracy. The effects of the heating used during post processing on the geometrical accuracy, shrinkage, strength and warpage on the specimens are discussed in this paper.

Abstract: A motorcycle frame system is a load bearing structure that always appears to suffer fatigue damage after running for a long time, indeed the fatigue life of the frame ultimately decides the service life of a motorcycle. In our work, we predicted the fatigue life of a motorcycle frame manufactured from two different materials by carrying out a road test in combination with computational simulation work based on the finite element analysis method. Firstly, signals from the strain and acceleration stemming from the key parts of the frame were collected by the road test, from which we have a preliminary understanding of the amount and distribution of stress. After this a finite element model and a multi-body dynamic model of the frame were built to obtain the results of the stress and information on the load based on the road test. According to the different material properties of Q235 and AZ91, we finally obtained the fatigue life and also discovered the weak parts of the frame. From the road test and results of the simulation we concluded that at 50km/h, most of the stresses inherent in the Q235 frame were well under the yield strength of the material. Indeed the high stress that results in a short fatigue life in some places was caused by concentrated stress and some unreasonable structural design. The stress of the AZ91 fame was the same as the Q235 in the experimental working conditions, while the weight of the frame can be reduced significantly. However the damage caused by fatigue that appeared earlier in the AZ91 frame than the Q235 frame can be attributed to its lower strength material.

Abstract: This study was undertaken to evaluate the likely effect on the wear rate of changing the pinion material in a rack and pinion steering box from carburised SAE-AISI grade 8617 H steel to induction hardened SAE-AISI grade 4140 steel of the same hardness. Accordingly, pin on disc wear tests were conducted using carburised 8617 H pins and through hardened 4140 pins. The surface hardness of the pins was approximately 60 HRC for both materials. The discs were made of SAE-AISI grade 1040 steel through hardened to a hardness of 45 HRC. The results showed that both the pins and the discs wore more rapidly when the tests were carried out with 4140 pins. The study indicates that the wear rate would be increased on both the rack and the pinion if the pinion material were changed from case hardened 8617 H to induction hardened 4140.

Abstract: The objective of this study is to investigate and evaluate the thermal desorption process to treat soil contaminated with high concentration of oil by applying microwave and high temperature heating element. It was found that TPH (Total Petroleum Hydrocarbon) was achieved below 2,000 mgkg^-1 of Korea criterion at 8kW of microwave powder and 700°C of processing temperature for 20 minutes. In addition, the rate of thermal desorption was also the highest value to be 0.09711 at 8kW of microwave powder and 700°C of processing temperature. Compared to other cases, the thermal desorption process applied by microwave had faster desorption rate of oil than conventional heat treatment process indicating that it would shorten processing time to treat oil-contaminated soil.

Abstract: In order to produce a defect-free component, the feedstock composition plays as a critical factor. The feedstock needs to meet the following criteria; high solid loading with excellent flowability. The flowability of the feedstock is greatly determined by the rheological response. Therefore, the aim of this paper is to investigate the rheological behaviour of MIM feedstock comprising of WC-Co powder, with a binder system of Palm Stearin (PS) and Polyethylene (PE), by means of a capillary rheometry. The viscosity and shear rate of various feedstocks at powder loading ranging from 59, 61 and 63% were measured at L/D = 10 die. The rheological properties such as flow behaviour index, activation energy and moldability parameter of each feedstock were calculated and from the analysis, it was concluded that they show a good pseudo-plastic behaviour within acceptable ranges in MIM.

Abstract: With an increasing pressure on automotive weight reduction, the demand on the lighter weight automotive components continues to increase. In recent years, squeeze casting processes have been used with different aluminium alloys to produce high integrity automotive parts. In this study, the indirect squeeze casting processes is adopted to cast a motorcycles component originally produced by a high pressure die casting process using aluminium alloy ADC12. To minimize amount of gas porosity inside squeeze casts, concepts of (1) minimization of ingate velocity along with (2) bottom filling pattern during the die filling, and (3) maximization of intensifications casting pressure are applied. Then parts are casted with both conventional high pressure die casting and indirect squeeze casting processes. Comparative evaluation of mechanical properties was made between HPDC casts and squeeze casts both in as-cast and heat treated conditions. Results from the experiment have shown that squeeze casts can pass the blister test at 490 °C for 2.5 hours. Then, squeeze casts are heat treated by solution treatment at 484 °C for 20 minutes and artificial age at 190 °C for 2.5 hours, respectively. This improves UTS of the heat treated squeeze cast to 254.14 MPa with 1.84% of elongation, while the UTS of as cast condition from both processes is not significantly different.

Abstract: Majority of the components of aerospace and automotive vehicles need different machining operations, mainly for the assembly requirements. The components have to present both high dimensional precision and surface quality. This present work is concerned with the effect of cutting parameters (cutting speed, feed rate and depth of cut) on the surface roughness and the chip formation in turning process. The machining results are compared with LM6 aluminium alloy and TiC reinforced metal matrix composite under the same cutting conditions and tool geometry. The cutting condition models designed based on the Design of Experiments Response Surface Methodology. The objective of this research is to obtaining the optimum cutting parameters to get a better surface quality and also the chip formation and furthermore does not hazardous to the worker and the machined products quality. Results shows that Surface roughness values of LM6-TiC composite are higher as compared LM6 alloy at similar cutting condition. With increasing in cutting speed improves the surface quality. The surface quality increases with decrease of the feed rate and the depth of cut. There are difference chip forms for LM6 aluminium alloy and Al-TiC composite for a similar of cutting condition. Generally, chip formations of both materials are acceptable and favourable for the worker as well as the products and the tools.