Applied Mechanics and Materials Vols. 592-594

Abstract: Bead on plate activated tungsten inert gas (A-TIG) welding of duplex stainless steel (DSS) 2205 was performed to determine the thermal history, temperature distribution and the weld bead geometry. Finite element (FE) simulations were carried out using the software, SYSWELD considering the temperature dependent thermal and mechanical properties of the base material. A 3D double ellipsoidal heat source was employed for the non-linear thermal analysis. The transient temperature distribution, weld bead profile, weld bead dimensions, depth of penetration and bead width were calculated by FE simulation. The simulated weld bead profile was compared with the experimentally measured profile and found to be in agreement.

Abstract: Natural fiber composites (NFC) and glass fiber composites (GFC) have been prepared by incorporating elephant grass fibers and glass fibers in to polyester matrix via hand layup technique. In this study, the fire properties of composites have been evaluated by cone calorimeter. The addition of elephant grass fiber has effectively reduced the average heat release rate (Av. HRR) and peak heat release rate (PHRR) of the matrix by 28 %, and 36 %, respectively. Maximum average heat rate emission and carbon monoxide yield of the bio composites decrease substantially compared with that of matrix. However, average carbon dioxide yield, and total smoke release values of matrix are slightly increased with the addition of the elephant grass fiber. The NFC ignites earlier, release greater levels of heat when compared with that of GFC. Average HRR, PHRR and THR values of NFC are about 39%, 71% and 38% greater than those of GFC, respectively. Further, theoretical models were used to predict time to flashover and FO classification of composites.

Abstract: The aim of the present investigation is to study the formation of electroless Ni-B-P alloy coatings and structural and morphological characterization of various coatings with different boron and phosphorous content. An alkaline plating bath with nickel chloride hexahydrate as the source of nickel ions and sodium borohydride and sodium hypophosphite as reducing agents were used for the formation of electroless Ni-B-P alloy coatings. The influence of changes in the concentrations of the reducing agents in the electroless plating bath on the chemical composition, structural and morphological characteristics of the coatings were studied. Scanning electron microscopic studies revealed that the surface morphology of Ni-B-P alloy coatings changed from corn cob-like structure to cauliflower-like structure with increasing borohydride concentration in electroless plating bath, whereas increase in hypophosphite concentration favoured sideway growth, thereby decreased the surface roughness of the Ni-B-P alloy coatings. The peak broadening in the X-Ray Diffraction profiles indicates the large reduction in the crystallite size of the electroless Ni-B-P alloy coatings with increasing boron content in the coating (i.e. for higher borohydride concentration in the plating bath).

Abstract: Micro turning is a scaled down version of conventional turning process, but operating on the micro scale of machining parameters to produce micro components. This paper deals with CNC Micro turning of Inconel 600 alloy with titanium carbide coated tool. Two conflicting objectives, surface roughness and tool flank wear, are simultaneously optimized. Full factorial experiments were taken with several combinations of cutting speed, feed and depth of cut. In this report, a new optimization algorithm based on the law of gravitation and mass interactions, namely Gravitational Search Algorithm (GSA) is aimed to predict the optimal parameter conditions for controlling tool flank wear and better surface finish.

Abstract: Gas Tungsten Arc Welding (GTAW) involves several process parameters. In Pulsed Current GTAW frequency of pulse and pulse to time ratio differentiates the characteristics of weld pool geometry of from GTAW. In the present work a simple heat transfer model for Pulsed Current GTA welding was developed and the weld pool dimensions were experimentally verified with AISI 1020 steel. Relationship between speed and pulsed current frequency on weld pool dimension was studied. Weld pool dimension of pulsed and non-pulsed GTAW is studied.

Abstract: Fused deposition modeling (FDM) is one of the thirty techniques of rapid prototyping methods that produce prototypes from polymer materials (natural or with different grades). Acrylonitrile butadiene styrene (ABS) is one of the good material among all polymer materials. It is used in the layer by layer manufacturing of the prototype which is in the semi-molten plastic filament form and built up on the platform from bottom to top. In FDM, one of the critical factor is to select the built up orientation of the model since it affects the different areas of the model like main material, support material, built up time, total cost per part and most important the mechanical properties of the part. In view of this, objective of the present study was to investigate the effect of the built-up orientation on the mechanical properties and total cost of the FDM parts. Experiments were carried out on STRATASYS FDM type rapid prototyping machine coupled with CATALYST software and ABS as main material. Tensile and Impact specimens were prepared as per the ASTM standard with different built-up orientation and in three geometrical axes. It can be concluded from the experimental analysis that built orientation has significant affect on the tensile, impact and total cost of the FDM parts. These conclusions will help the design engineers to decide on proper build orientation, so that FDM parts can be fabricated with good mechanical properties at minimum manufacturing cost.

Abstract: In-situ aluminum matrix composites have good bonding strength and homogeneous distribution of particles, which offer improved mechanical property and wear resistance. Electrical discharge machining is considered as a suitable process for making complicated shape of difficult to machine materials. In this experimental work AA6061-6% TiB₂/ZrB₂ in-situ metal matrix composite was fabricated using flex assisted synthesis. This experimental investigation is focused to study the influence of electrical discharge machining process parameter on surface roughness in machining of the AA6061-6% TiB₂ /ZrB₂ composite. Taguchi method and L₉ orthogonal lay out are applied to conduct the experimental work. Analysis of variance was performed to evaluate the percentage of contribution of each parameter. The analysis of the result indicates that discharge current has strongest influence on the surface roughness. This experimental study helps to select the optimal machining parameter to achieve good surface finish.

Abstract: Strengthening the engineering material through Severe Plastic Deformation and associated structural refinement is an established practice. Among the Severe Plastic Deformation process, Equal Channel Angular Pressing (ECAP) assumes a significant place. In this, it is possible to attain even ultra fine grain (UFG) structure through high deformation in bulk material working mode. However ECAPed material suffers lack of ductility, structural inhomogenity and even thermodynamically unstable structure, as evidenced in the published literature on ECAP of copper. The present study on ECAP of commercial purity copper aimed to attain a structure of higher hardness by shedding little ductility is deviated from the past work; in this, commercial quality copper is ECAPed at 300⁰ C with a die geometry channel angle of 110⁰ and corner angle of 20⁰ necessitating less local/working stress. During certain number of passes (six passes), the material experiences higher hardness with fair amount of ductility. The material does not exhibit any further strengthening beyond six passes, which is possibly due to dislocations annihilation/recovery. The increased strength and loss of ductility of the material results in degrading the material when it undergoes tenth pass.

Abstract: The present paper describes the influence of pulse-on-time on performance features such as Metal Removal Rate (MRR), Kerf width, Surface Roughness (SR) on cutting Titanium alloy (Ti-6Al-4V) in wire electrical discharge machining (WEDM) using zinc coated brass wire. The deionised water is used as dielectric fluid. The process parameters such as wire tension, wire speed, flushing pressure, discharge current, sparking voltage and pulse off time have kept constant at appropriate values throughout the experiment and the pulse on time is varied at nine different intervals. It was found that pulse-on-time is the most significant factor which greatly influences MRR, kerf width, and SR. It was also observed that taper at the end of cutting zone which is unavoidable occurrence for the machined part. This is due to the erosion of wire material. The surface roughness increases with increase in pulse on time also with higher rate of MRR.

Abstract: Silicon is an important alloying element in Al alloys because the presence of Si improves the hardening strength of Al alloy and improves the wetting between the matrix and the reinforcement. In the present study, Al/SiC bonded specimens were fabricated by means of different temperatures and holding times. The microstructure of the composite was examined by scanning electron microscope. The concentration of Si elements at the interface region was observed by EDS techniques and diffusion of the Si elements in the matrix region was calculated by the Arrhenius equation. The hardness test was performed at the interface region. The results revealed that processing temperatures and holding times influences the concentration of Si and the hardness values near the interface region. Keywords: Al/SiC Interface bonding; SEM; EDS analysis; Micro hardness