In the present work, an experimental investigation on wire electrical discharge machining (WEDM) of Monel-400 has been presented. Monel-400 is a nickelcopper-based alloy, mostly employed in ships and corrosion-resisting applications. Four input WEDM parameters namely discharge current (Ip), pulse-on time (Ton), pulseoff time (Toff) and servo voltage (SV) have been investigated and modeled for two performance characteristics namely machining rate (MR) and surface roughness (SR). Effect of WEDM parameters has been discussed using response surface graphs. Using analysis of variance, quadratic model is found significant for MR while two factors interaction (2FI) model has been suggested for SR. To optimize multi-performance characteristics, desirability function has been employed. Corresponding to highest desirability, the optimal combination of discharge parameters is Ip: 103 A; Ton: 113 ls; Toff: 37 ls and SV: 50 V. The effect of discharge energy on surface morphology has also been examined. High discharge energy increases the extent of surface damage and results in large size and overlapped craters on machined surface. Low discharge energy and high value of Toff result in minimum defects on machined surface. Trim cutting operations were performed at low discharge energy using different wire offset values. Result shows that surface finish can be improved significantly after a single trim cut irrespective of high discharge energy in rough cut.
A numerical analysis procedure using the boundary-integral equation method is presented for the solution of problems of time-dependent inelastic deformation in planar metallic bodies. The formulation allows the use of both classical creep theories as well as newer theories of inelastic deformation using state variables. Numerical results are presented for plane stress problems using either the power law equations of creep or the state variable theory due to Hart. Comparison of BIE and analytical methods for simple problems shows good agreement. Other features of the numerical solutions of more complicated problems are discussed in the paper.
In the present work, elasto-plastic creep crack growth simulations are performed using continuum damage mechanics and extended finite element method. Liu–Murakami creep damage model and explicit time integration scheme are used to evaluate the creep strain and damage variable for various materials at different temperatures. Compact tension and C-shaped tension specimens are selected for the simulation of crack growth analysis. For damage evaluation, both local and nonlocal approaches are employed. The accuracy of the extended finite element method solutions is checked by comparing with experimental results and finite element solutions. These results show that the extended finite element method requires a much coarser mesh to effectively model crack propagation. It is also shown that mesh independent results can be achieved by using nonlocal implementation.
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