Materials Science Forum Vol. 751

Abstract: Retreading has many potential applications in tyre manufacturing industry. There is a critical need for optimization of vulcanization processes used in tread manufacturing. Not much work hitherto has been reported for optimization of efficient sulphur vulcanization process of the tread manufacturing. The present experimentation work highlights approach to macro-model strength, elongation and hardness during vulcanization of rubber. Relationship between strength, elongation, hardness and other parameter has been deduced by using Taguchi L9 orthogonal array (OA). Results indicate that the hardness, elongation and strength of tread rubber while vulcanization depends significantly on the natural: synthetic rubber ratio (NR: SR), curing time and curing temperature of the rubber.

Abstract: The particle reinforced metal matrix composite have hard particles dispersed in matrix which make them difficult to machine with conventional machining methods. Electric discharge machining (EDM) is an effective tool for machining such materials. This experimental study was undertaken to identify the significant factors that affect the output responses while machining of 10 vol%Al2O3/Al composite material. The material removal rate (MRR) and tool wear rate (TWR) have a direct relationship with current and an inverse relationship with pulse on-time. Appropriate levels of current and pulse on time levels can be chosen while roughing and finishing operations. Normal polarity between terminals had higher MRR than with reverse polarity. The recast layer had a non-uniform and wave-like morphology and cracks penetrated into the matrix phase resulting in high residual stresses exceeding the ultimate tensile strength of the material. Pulse on-time has greater influence on recast layer thickness than current. The reinforced particles were all clustered under the machined surface with very few in the recast layer which results in a low strength of the machined surface. The presence of reinforced particles in recast layer is very rare, so it is desirable to remove it. Keywords: electro-discharge, machining, aluminum matrix composites, material, removal, tool, wear, roughness, recast, layer

Abstract: Metal matrix composites (MMC) have many potential engineering applications. Not much work hitherto has been reported for development of Al based MMC with vacuum moulding (VM) process. In this work; Aluminum (Al) based MMC has been developed with VM. An approach to macro-model the micro hardness and dimensional accuracy for development of Al-SiC, MMC has been proposed and applied during VM process. Relationship between micro hardness, dimensional accuracy and other input parameters of VM process has been deduced by using Taguchi technique. The comparison with experimental results will also serve as a future validation of the model.

Abstract: In this paper, the effect of different wire electrodes used in wire electrical discharge machining (WEDM) on the machining characteristics of AISI D3 die steel has been presented. Three process parameters, namely type of wire (brass wire, zinc coated wire and composite wire), pulse on time and peak current have been considered. The process performance is measured in terms of cutting speed and surface roughness. The research outcome will identify the important parameters and their effect on performance characteristics while machining AISI D3 material with different wire electrodes. The analysis of variance (ANOVA) of multilevel factorial design indicated that all the selected parameters have significant effect on the performance characteristics. The study indicated the improvement in surface roughness with brass wire over other wires. Maximum cutting speed was obtained with composite wire as compared to zinc coated and brass wire. Additionally, scanning electron microscope (SEM) examination highlighted important features of machined work piece surface.

Abstract: This paper aimed to investigate the effect of shape factor, slurry layers and pouring temperature in precision investment casting. Three controllable factors of the precision investment casting process (namely: shape factor, slurry layers (mold thickness) and pouring temperature) were studied at three levels each by Taguchis parametric approach and single-response optimization was conducted to identify the main factors controlling surface hardness, dimensional accuracy (Δd) and surface roughness (Ra). Castings were produced using aluminum (Al), mild steel (M.S.) and stainless steel (S.S) at recommended parameters through ceramic shell precision investment casting process. The micro structure analysis has been used to study the surface morphology. Analysis shows that for surface hardness, contribution of shape factor, slurry layers and pouring temperature is 0.07%, 0.70% and 99% respectively. As regards to surface roughness, contribution of shape factor, slurry layers and pouring temperature is 1.14%, 16.80% and 81.90% respectively. Further for Δd contribution of shape factor, slurry layers and pouring temperature is 1.53%, 22.47% and 72.88% respectively. Confirmation experiments were conducted at an optimal condition showed that the surface hardness, Δd and Ra of the precision investment casting were improved significantly.

Abstract: In the present study, the powder mixed EDM (PMEDM) process was simulated using FE approach to obtain simulated temperature profiles for estimating the crater dimensions and volume removed during formation of each crater. The craters formed in PMEDM process had higher diameter and shallow depth resulting in improved MRR and better surface finish. The addition of powder increased the amount of heat available at the workpiece between 20-25% as compared to conventional EDM process. The results were subsequently validated experimentally to compare the actual measurements with the simulation output. Predictor equations for crater radius and depth incorporating the significant factors were developed and also validated with the experimental results.

Abstract: In the present work, replication process for plastic components with silicon moulding (SM) has been investigated for statistically controlled rapid casting (RC) solution. Starting from the identification of component, prototype with three different types of plastic materials was prepared under different conditions of de-moulding time and mixing ratio. Relationship between dimensional accuracy in SM and other controllable parameters has been deduced by using Taguchi technique L9 orthogonal array. The study suggested the long-term performance level of the SM process after it has been brought under statistical control as RC solution for plastics. The provided data from the experimentation highlights the ability of the SM process to produce a product that will consistently meet the design requirements and the customer expectation. Keywords: Silicon moulding, dimensional accuracy, statistically controlled

Abstract: Erosion behavior of the high velocity oxy fuel (HVOF) deposited Cr₃C₂-NiCr and WC-Co coatings on boiler tube steels was evaluated. The solid particle erosion study was conducted, using an air jet erosion test rig at a velocity of 26 m/s and impingement angles of 30⁰ and 90⁰, on uncoated as well as HVOF spray coated boiler tube steels at 250°C. The coatings are significantly harder than the substrate steel and less porous. Scanning electron microscopy (SEM) technique was used to analyze the eroded surface. Mass loss of the coatings was found higher than the boiler tube steel.