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Residual stress could be induced by machining processes like milling which can greatly affect the fatigue life of fabricated parts, especially in dynamic loading conditions. In metal cutting operations, machining induced residual stresses can be explained in the terms of machining forces and temperatures of the cutting zones. This thermo mechanical loading along with the resulted metallurgical changes are the main sources of residual stresses generation at the surface of machined workpiece. Researchers have proved the superior properties of nanofluids over the conventional coolants to reduce the intensity of thermo mechanical loading in machining process which will affect the residual stresses caused by machining. Therefore, in this paper, silver nanoparticles in the water-soluble oil have been used for reducing the mechanical and thermal loads in the milling process. The cutting forces, temperature of the cutting zone, surface roughness and the residual stress of machined surface have been measured experimentally in milling of hardened steel AISI 4140 for various nanoparticle’s concentration, feeds and cutting speeds. Results show that increasing the concentration of Nano-particles in base fluid from 0.5 to 3.0% wt., will make machining surface residual stresses more compressive averagely by about 66.67% compared to conventional cutting fluid.

Engineering ceramics such as alumina have found special applications in aerospace, electronics, and automotive industries due to their superior mechanical and thermal properties. Among these properties, chemical stability at high temperatures, high strength to weight ratio, hardness, strength, wear, and corrosion resistance are of prime importance. Due to these superior properties, processing of these ceramics encounters some difficulties and requires special machining processes such as diamond grinding; in addition to high manufacturing costs, this technique suffers from noticeable challenges such as high grinding forces and temperatures which may lead to serious surface damages. To overcome these challenges, in recent years, laser-assisted grinding has been introduced; in this process, laser source is used to preheat or structuring the workpiece surface in order to reduce grinding forces and temperatures. In this research, first four different patterns were created on alumina using a pulsed laser. Then, these weakened structures were machined using creep feed grinding. In order to provide a better understanding from the effect of each pattern, the volume of the material that can be removed was kept constant in all four patterns. Finally, the effect of created patterns on grinding forces and surface roughness has been studied. Besides, scanning electron microscopy has been used to investigate possible surface damages. The results showed that the normal and tangential forces in the non-structured case were 2 and 2.7 times higher than the forces recorded in the best patterned samples. However, no significant effect of the created patterns on the surface roughness was observed. Furthermore, serious heat damage and cracks were not observed in the structured workpieces, but non-structured workpieces were crushed during operation. Among the created patterns, pattern with perpendicular grooves to the grinding direction was introduced as the best.

Nowadays, laser drilling has found extensive medical applications such as drilling of titanium implants. However, laser drilling of such implants has encountered several restrictions such as low penetration depth, high thickness of recast layer and heat affected zone (HAZ). Therefore, various approaches such as magnetic field and/or ultrasonic vibration aided laser drilling have been proposed to overcome these limitations; among them, few studies have been conducted considering the simultaneous effect of magnetic field and ultrasonic vibrations on microstructural characteristics. Therefore, in the present paper, the effects of magnetic field intensity and ultrasonic vibration amplitude (with a frequency of 28 kHz) have been investigated on the formed phases, thickness of recast layer and thickness of HAZ in laser drilling of Ti6Al4V. According to the obtained results, adding ultrasonic vibrations to the laser drilling process will lead to an average decrease of 29.40% and 28% respectively for the thickness of HAZ and recast layer. However, with the addition of a magnetic field (0.1 Tesla), the thicknesses of HAZ and recast layer were increased by 7% and 11%, respectively. Furthermore, increasing the ultrasonic vibration amplitude was associated with the increase in the acicular alpha phase (α′) as well as more dense, and fine-grained and uniform structure. This can be attributed to the strengthening of convective heat transfer mechanism and higher cooling rate. Additionally, by increasing the intensity of the magnetic field, the structure of the acicular alpha (α′) became finer and the density of lateral branches decreased.