Applied Mechanics and Materials Vols. 592-594

Abstract: In this work, the influence of variation in machining parameters cutting speed, feed rate and depth of cut and geometrical parameters cutting insert shape (included angle), relief angle and nose radius is studied using DEFORM-3D, a finite element simulation software. The cutting tool inserts of various geometries are evaluated to study its performance for varying conditions considering contact temperature and mean stress. Effect of individual parameter is analyzed by varying its value by three different level values, while the other parameter values are set at the optimum condition, likewise for all input parameters. From the results obtained, it is observed that the performances of cutting inserts are good at the optimum level of parametric values than at the other level values.

Abstract: Welding input parameters play a very significant role in determining the quality of a weld joint. The joint quality can be defined in terms of weld-bead geometry. The 2³ replication with 4 center points experiments are performed on non-return valve material WCB by varying various MIG Welding process parameters. Here welding current, welding speed and gas flow rate are considered as input parameters with two levels. A fuzzy model is developed to predict the weld width in context of these input parameters. Fuzzy model uses fuzzy expert rules, triangular membership function and centroid area method for defuzzyfication process using MATLAB fuzzy logic tool box. The developed model is validated by performing experiments at center points. The result shows prediction may lie in the range of 95.18-100%.

Abstract: This study investigated the preparation of nanosized crystalline SiC powders from micro sized Silicon Carbide powder at room temperature through high energy ball milling. Silicon carbide was milled with hardened steel balls and ball milling media under identical conditions of ball mass to powder mass ratio 10:1 and target milling times of 60 h. The sample was taken out after every 20 hours of milling and it was characterized for its crystalline size, lattice strain, and percentage of crystalline by using X-Ray Diffractometer (XRD). It was found that for the 60 hours The size, shape and texture of the fresh as well as nanostructured Silicon carbide powder were studied using Scanning Electron Microscopy (SEM). The raw Silicon carbide powder particles were mostly angular in shape. The shape of the 60h milled particles is irregular and the surface morphology is rough.

Abstract: Milling is one of the most practical machining processes for removing excess material to produce high quality surfaces. However, milling of composite materials is a rather complex task, owing to its heterogeneity and poor surface finish, which includes fibre pullout, matrix delamination, sub-surface damage and matrix polymer interface failure. In this study, an attempt has been made to optimize milling parameters with multiple performance characteristics in the edge milling operation, based on the Grey Relational Analysis coupled with Taguchi method. Taguchi’s L18 orthogonal array was used for the milling experiment. Milling parameters such as milling strategy, spindle speed, feed rate and depth of cut are optimised along with multiple performance characteristics, such as machining forces and delamination. Response table of grey relational grade for four process parameters is used for the analysis to produce the best output; the optimal combination of the parameters. From the response table of the average GRG, it is found that the largest value of the GRG is for down milling, spindle speed of 1000 rpm, feed rate of 150 mm/min and depth of cut 0.4 mm.

Abstract: In this paper, rotary electrical discharge machining of RENE 80 nickel super alloy is carried out to study the effect of process parameters like peak current, pulse on time, pulse off time and rotational speed of electrode on surface integrity characteristics like white layer thickness and surface crack density. The number of experiments, optimum levels of the parameters and their effects are studied using Taguchi method. The significant process parameters are identified using analysis of variance. It is found that the responses are affected mainly by peak current and pulse on time. The experimental results reveal that white layer thickness increases with increase of peak current and pulse on time whereas the surface crack density decreases with increase of peak current and pulse on time.

Abstract: In general, aerostatic bearings are flat bearings and the stringent manufacturing tolerances in geometric dimensions and profile will make the bearing ideal for obtaining high stiffness during measurement. Aerostatic Spherical Bearing (ASB) on the contrary is a special bearing which provides a frictionless pivot and allows three degrees of rotational freedom. Methods involved in manufacturing and realizing a highly stiff ASB is discussed in this paper. ASB components viz. Stator and Rotor of hemi-spherical in geometry are the critical components to be machined, which are used in Mass properties and Dynamic Balancing Measurement machine (MaPDBM). MaPDBM is used to measure mass, center of gravity, moments of inertia and static & dynamic unbalance of spacecraft. An air film of 25-50 μm thickness separates the stator and rotor during measurement, thus forming an aerostatic bearing. Precise Machining, Thermal treatments to ensure crash-proof design, Special processes like lapping for profile correction, Geometrical and profile measurements during different stages in the sequence for controlling the bearing parameters using Coordinate Measurement Machine (CMM) are the challenges involved in the machining and realization of the ASB components and the same is discussed in this paper.

Abstract: This study investigates the role of thermal energy in deposition of thick layer of powder material by PTAW process. For analysis, stainless steel material powder of grade SS304L are laid on the substrate of grade SS316. The energy required for melting the powder and available for the substrate are calculated considering losses during deposition. The effects of input process parameters i.e. energy, scanning speed, powder feed rate are investigated on bead characteristics and dilution.

Abstract: The heat produced in metal cutting process is one of the most critical issue in machining of titanium alloys. High temperature in metal cutting degrades the tool life, surface integrity, size accuracy and machining efficiency dramatically. The temperature generated during end milling of titanium alloy, has been measured using Thermo camera. Surface roughness plays a vital role in evaluating and measuring the quality of the machined surface. During the experiments, cutting speed and feed rate have been changed to analyse the effect of temperature and surface roughness. It is observed that cutting speed has the greater effect on temperature and surface roughness during end milling of titanium alloy. The regression equations generated have better fit which can be used for optimization.

Abstract: Friction Stir Welding (FSW) as a joining technique with regard to low melting temperature materials such as aluminum alloys has already been established and implemented in the industry. But, with regard to high melting temperature metals and alloys the major issue still to get successfully addressed is a pertinent tool material for a class of work materials and to get their operating parameters optimized. This paper presents a detailed assessment on the FSW of high melting temperature (HMT) materials, giving emphasis on the tool materials, tool geometry and FSW equipment aspects based on the information gathered from experimental studies and research publications.