Applied Mechanics and Materials Vols. 592-594

Abstract: Aluminium matrix composites (AMCs) having more than one reinforcement (hybrid AMCs) found enlarged use due to better strength, high thermal stability and wear resistance properties and can be a substitute for single reinforced AMCs .The effect of varying ball milled (BM) B₄C/Si₃N₄ particles on the microstructure of as cast AA6082 and mechanical properties of AA6082 alloy hybrid composites produced by combined ball milling and conventional stir casting method have been reported. The combined reinforcement of BM B₄C/Si₃N₄ particles were varied from 0-9 % in a step of 3. The wettability of B₄C/Si₃N₄ into the aluminium melt has been increased by ball milling the boron carbide with silicon nitride powder, so that combined reinforcement of B₄C/Si₃N₄ neither float nor sink in the aluminium melt. The investigated result showed that addition of combined reinforcement of BM B₄C/Si₃N₄ increased Hardness and Ultimate tensile strength at the cost of reduction in percentage elongation.

Abstract: Limitation in penetration depth is a concern in conventional TIG welding process. To improve penetration capability of TIG process, both Activated TIG (ATIG) and Flux Bounded TIG (FBTIG) are investigated in aluminum alloy AA 2219 T87. Undesirable arc wandering and cracking tendency are observed in ATIG welds. Microstructural investigation reveals ATIG welds are prone for liquation cracks. Morphology of the cracks along with the attributable factors are explained with optical and SEM (Scanning Electron Microscope) micrographs. Energy Dispersive Spectroscopy (EDS) results are also presented to explain the solute enrichment in the grain boundaries of the ATIG welds. FBTIG is found to produce good quality welds and is more suitable for welding aluminum alloys. Key words: Flux Assisted TIG; ATIG; FBTIG; Penetration Improvement; Microstructure; AA2219.

Abstract: In the present work, Al-TiB₂ in-situ metal matrix composites were processed via master alloy route at 800°C-30 min. with 5 and 7wt% of TiB₂ particles. Microstructural characterization of the prepared insitu composites were carried out using XRD, SEM/EDX studies. X ray diffraction studies have shown the presence of Al₃Ti and TiB₂ phases, however, the presence of AlB₂ particles is also highly likely. SEM/EDX characterization revealed fairly uniformly distributed TiB₂ particles having hexagonal morphology with size distribution in the ranges between 0.5-10μm. Further, presence of TiB₂ particles in Al matrix have resulted in improvement in hardness and tensile properties of the Al matrix while decrease in ductility was observed.

Abstract: Abstract. Conventional welding of copper and its alloys tends to degrade the mechanical strength at the welded area due to high thermal diffusivity and melting point. Friction stir welding (FSW) is an excellent alternative for joining of these materials against fusion joining. FSW is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The main objective of this investigation is to use FSW for joining of 3 mm thick copper sheet using taper cylindrical tool pin profile. The defect free welds were obtained at a tool rotational speed of 900rpm and 1120 rpm and traverse speeds of 25, 31.5, 40 and 50 mm/min respectively. Mechanical and microstructure analysis has been performed to evaluate the characteristics of friction stir welded copper. From the investigation it is found that the joints fabricated at a tool rotation speed of 900 rpm and traverse speed of 40mm/min resulted in better mechanical properties compared to other tool rotation and traverse speeds. The tensile properties of all the weld joints showed a relative correspondence to the variation of the hardness in the weld zone. The observed results were correlated with the microstructure and fracture features.

Abstract: Equal Channel Angular Pressing is a severe plastic deformation technique to produce Ultra Fine Grain (UFG) microstructure in bulk materials. The strain induced due to the severe plastic deformation depends mainly upon the channel angle and the processing route followed. Various dies with different channel angle are modeled and analyzed through DEFORM 3D. The strain imparted and the load required for different channel angles and different processing routes are determined from the analysis results. The results are compared and the optimum channel angle is determined.

Abstract: Wire Electric Discharge machine is non-conventional thermo-electric spark erosion machining process to cut conductive metal and alloys. The main mechanism of machining is spark erosion between the tool and work-piece. High carbon high chromium tool steel (D-2) is a hard alloy with high hardness and wear resisting property. The purpose of this study is to investigate the effect of process parameters on the machining of D-2 tool steel. D-2 tool steel used in tool and die industries. Response Surface Methodology (RSM) is used to formulate a mathematical model which correlates the independent process parameters with the desired dimensional deviation. The central composite rotatable design has been used to conduct the experiments. Genetic algorithm is used to predict the best individual parameters along with the predicted fitness values.

Abstract: Micro EDM milling process is accruing a lot of importance in micro fabrication of difficult to machine materials. Any complex shape can be generated with the help of the controlled cylindrical tool in the pre determined path. Due to the complex material removal mechanism on the tool and the work piece, a detailed parametric study is required. In this study, the influence of various process parameters on material removal mechanism is investigated. Experiments were planned as per Response Surface Methodology (RSM) – Box Behnken design and performed under different cutting conditions of gap voltage, capacitance, electrode rotation speed and feed rate. Analysis of variance (ANOVA) was employed to identify the level of importance of machining parameters on the material removal rate. Maximum material removal rate was obtained at Voltage (115V), Capacitance (0.4μF), Electrode rotational Speed (1000rpm), and Feed rate (18mm/min). In addition, a mathematical model is created to predict the material removal

Abstract: Electrical discharge alloying was performed on AISI D2 tool steel with addition of nickel powder. Taguchi method has been used to plan and analysis the experiment.The major parameters like Peak current, pulse on time, and pulse off are taken for this study for formation of alloyed layer. The influences of these process parameters have been identified by Signal to noise ratio (S/N) and analysis of variance (ANOVA) and their results are within the limits of predicted and experimental values. The experiments were conducted on a specially designed apparatus in laboratory itself. The layer thickness varies from 70 to 140 μm and the highest hardness value of 1788 HV0.3 with a lower specific wear rate.

Abstract: Electrochemical Discharge micro-machining process appears better utility with greater effectiveness in the modern micro-machining industrial field. Electrochemical discharge micro-machining process is involved to generate micro-channel as well as curve profile on glass for utilization as micro-fluidic device. This paper shows second order mathematical modeling of correlation between the machining criteria such as machining rate as a form of material removal rate (MRR), overcut (OC), machining depth (MD) with various process parameters like applied voltage (V), electrolyte concentration (wt %) and inter-electrode gap (IEG) (mm). The analysis of variance (ANOVA) has been performed to find out the adequacy of the developed models.This paper also shows the multi objective optimization to achieve the optimal parametric combination for maximum MRR, MD and minimum OC using response surface methodology (RSM). Keywords: μ-ECDM, MRR, OC, MD, RSM, ANOVA, Glass.

Abstract: Particle board serves numerous functions such as cabinetry, tabletops, shelving, wall & floor panels, etc. Though Particle boards are much cheaper compared to solid wood, machining the material by optimizing the process parameters is a big challenge. Drilling is the major operation during final assembly of particle board, where fasteners are used to join together to bring final shape to the product. In this paper, the operation parameters such as speed, feed, drill diameter has been considered during drilling operation performed on Particle board and the output responses-surface roughness of the drilled hole and the Thrust force acting on the board during drilling are measured. Good surface finish of the hole ensures reduction of localised stresses around the hole due to fastening. Reduced Thrust force contributes to lesser delamination in particle board. Hence minimisation of both surface roughness and delamination is desired and hence optimisation of both responses is done simultaneously using grey relational analysis.