محمد یزدانی خامنه

The effect of texturing the tool rake surface on the surface quality in hard turning of 1191/1 steel with a surface hardness of 45 HRC was studied in this research. The pattern parameters including, cavity diameter, pitch, and depth, as well as the pattern distance from the main cutting edge were changed in 3 levels, assuming the cutting tool with regular cavity texture. Nine tests were designed using the Taguchi DOE and conducted in dry and lubricated conditions with 2 repeats. Machining forces during the tests and surface roughness of the machined workpieces were measured in machining under lubricated and dry conditions. The results showed that in turning with a textured tool under lubrication, changing the parameters of the texture pitch and the distance from the cutting edge increased the surface roughness of the workpiece by 57.6% and 39.2%, respectively. This is while the increase in the diameter of the tissue cavity, due to the reduction of the contact area in the tool-chips interface and better lubrication near the cutting region, improved the surface roughness up to 40.7%. The cavities depth of also did not have a significant effect on improving lubrication and reducing the roughness of the final surface. In dry turning, increasing the cavities diameter in texture and decreasing the pattern pitch, reduced the surface roughness by 10.6% and 29%, respectively. Examining the SEM images also indicated the production of the workpiece surface with smoothed texture when turning using optimized textured tool.

In this article, the effect of creating a surface pattern on the expression of cutting has been studied. More precisely, the effect of the texture created by laser engraving on the values of machining forces was investigated in different states, and these tests were performed both in the presence of lubricant and in its absence. The parameters of depth, pitch, texture diameter and distance from Cutting edges were considered as tool texture parameters. A total of 9 experiments were conducted using the Taguchi test design method. Lubrication in both textured and non-textured tools reduced the machining force by 30-35%. In the end, the machining forces obtained from the test were compared with textured and non-textured tools in the presence of lubricant, and it was observed that due to texturing of the tool, the machining force decreased by about 28%.

In this study, variations in the residual stresses distribution were studied in different hole-making strategies including; conventional, multi-step drilling and helical milling. Residual stresses were measured for 12 perforated samples made of 4340AISI steel, using nanoindentation method. The results showed the highest near-surface compressive residual stress in the multi-step drilling (up to 373.5 MPa). Also, due to the phase transformation on the surface, the effect of plastic work was eliminated and tensile residual stresses up to a maximum of 114.7 MPa were measured in the drilling process. On the other hand, decreasing the cutting speed and increasing the feed rate raised the compressive stresses up. The trend exception was formation of the white layer in the drilling process. Comparison of the stresses measured on the reference sample also showed a difference of about 28.6% between the two methods of XRD and nanoindentation, which shows an acceptable repeatability of the measurement using nanoindentation method.

In this article, the improved Oxley model, which is actually a combination of the Oxley and Johnson-Cook models, was introduced. The Oxley model does not take into account the effects of strain rate, hardness and heat increase, so by linking the Johnson-Cook model with this model, the Oxley model was developed. In this article, a program was written with Matlab software, which performed the analytical solution of the drilling process with the improved Oxley model, and according to the classical torque formula, the amount of this parameter was calculated according to the tangential force output from the Matlab code. Then the value of torque was compared with the value of this parameter in numerical modeling using AdvantEdge software, The difference between the numerical and analytical solutions is 12.5%, which indicates that the approximation in the presented analytical model is acceptable.