M. Vashista

Correlation between full width at half maximum (FWHM) of XRD peak with residual stress on ground surfaces

The full width at half maximum (FWHM) of XRD profiles is used to characterize different material properties and surface integrity features. However, there is no literature available that discusses the nature of the correlation between the FWHM of XRD peaks with induced surface residual stress upon grinding with simultaneous occurrence of plastic deformation, formation of white layer, grain elongation, change in microhardness, etc. AISI 1060 steel samples were ground under different grinding domains, i.e. conventional abusive grinding, conventional grinding, cBN grinding and high speed grinding with moderately deep cut. Induction of tensile and compressive residual stress, microstructural changes, white layer formation, grain refinement, plastic deformation, grain elongation and change in microhardness were observed upon grinding AISI 1060 steel. A correlation was established between the FWHM of XRD peaks and surface residual stress when simultaneous changes in microhardness and microstructure, grain elongation, plastic deformation and formation of white layer take place due to grinding. The correlation between FWHM of XRD peak and residual stress appears to be nonlinear due to simultaneous change in other aspects of surface integrity.

On the critical behaviour of Barkhausen noise parameters in surface grinding

An experimental study was undertaken to investigate the critical behaviour of Barkhausen noise (BN) parameters after surface grinding of medium carbon steel. The relations between residual stress and BN parameters were discussed in terms of degree of plastic deformation. The best parameter for residual stress evaluation is root mean square (rms) value of BN signal. In the present work, when the residual stress is more than the yield strength of the work material, the correlations between BN parameters, downfeed, residual stress, grain elongation and change in microhardness upon grinding have been investigated. X-ray diffraction (XRD), metallographic study and microhardness measurement of ground samples were studied. BN parameters were shown to increase with plastic deformation and then decrease with elevated level of plastic deformation. The results are explained in terms of mechanism that affects dislocation density as a function of grain elongation or plastic deformation and interaction of domain walls.

On the role of magnetising frequency and magnetic field intensity on hysteresis loop characteristics

The goal of present research work is to study the variation in the shape of hysteresis loop owing to change in the analysis parameter i.e., magnetising frequency and applied magnetic field strength upon pack carburised low carbon steel samples. Pack carburised heat treatment performed at three different temperatures to induce varying hardness into steel samples. Hysteresis loop characteristics such as coercivity, permeability, power loss and remanence were measured in a wide range of magnetising frequency and magnetic field intensity. Coercivity is observed to increase with increase in magnetising frequency and applied field strength. In low-frequency range ( 1 Hz) results into increase in remanence and power loss. However, with an increase in magnetic field strength both remanence and power loss were found to increase.

Effect of process parameters on convective heat transfer coefficient of fluid and heat partitioning in high efficiency deep grinding with water-based coolant

A statistical analysis was undertaken to study the role of process parameters on the convective heat transfer coefficient of fluid (hf) and heat partitioning ratios in HEDG. Heat partitioning ratios have been calculated by using experimental data and models developed by previous researchers. Regression models between grinding process parameters and partitioning ratios has been developed using DoE technique and RSM. Heat partitioning ratio to chip increases with MRR and takes around 20% of grinding heat. Very less amount of heat is carried away by workpiece and cubic boron nitride grinding wheel. The hf increases with wheel speed and reduction in contact length. This enables the grinding fluid to take most of heat and limits the rise in temperature up to 140°C despite of high MRR. Previous researchers considered constant value of hf, but in present study variation in hf with process parameters has been considered to calculate the heat portioning ratios.