m honarpisheh

Wire EDM is a modern machining process that uses electrical discharge to cut workpieces. High temperatures generated by wire EDM can cause surface cracking due to metallurgical changes. A new approach is to use the ultrasonic peening treatment to cause surface severe plastic deformation to improve the mechanical properties, especially the hardness. In this study, the focus was on exploring the impact of cutting types in wire EDM, feeding rate, and the number of peening passes as input parameters on Mo40 (1.7225) alloy steel. The experiments were designed using the multilevel factorial design method. The average hardness values were then analyzed based on the input parameters. The maximum hardness value was determined through optimization using the multilevel factorial design method. Analysis of variance was used to evaluate the impact of parameters on hardness. The highest hardness value of 952.7 (HV) was obtained with a feeding rate of 0.12 (mm/rev) and 3 peening passes in roughing mode, leading to a 48% increase in hardness. A mathematical model with 99.87% desirability was developed to study the correlation between input parameters and response variables. The hardness distribution in the peened workpieces continued up to 200 µm below the surface layers. The highest hardness was found at a feeding rate of 0.12 (mm/rev), which influences the time needed to alter dislocation density and form a new sublayer structure. Overall, increasing the feeding rate decreases hardness, while increasing peening passes increases it. According to a single-objective optimization, the cutting types, feeding rate, and number of peening passes respectively affect hardness value.

Non-equal-channel angular pressing (NECAP) is emerging as one of the most developed severe plastic deformations (SPD) methods that require more detailed investigations. Machining study is inevitable to form any material into required dimensions. The lack of NECAP processed materials machining data, as a fundamental stage for production development, motivated the present work, in which the machinability aspects of Al 3003 subjected to NECAP process, in terms of cutting force, surface roughness, and chip morphology have been investigated and compared to initial state of mentioned material. Experimental runs have been conducted using defined machining parameters under the name of spindle speed, feed rate, and depth of cut. The results show noticeable enhancements in which impact of NECAP process on the machinability of Al 3003 causes reducing the cutting force (10.24%), surface roughness (8.47%), and chip formation improvement. High spindle speed (1500 rev/min), low feed rate (98 mm/min), and depth of cut (0.5 mm) have been the best cutting parameters combination to achieve desired machinability aspects in both workpiece, before and after NECAP process. The paper's findings advocate the application of NECAP processed Al 3003 in manufacturing industries.

Cutting is one of the most important manufacturing processes in various industries. After the cutting process, residual stresses are created in the parts. So, calculation and prediction of residual stresses is important and ignoring them if combined with applied stresses can cause failure in parts. In this study, the effects of laser, plasma and wire-cut processes were investigated on the residual stress of st37 sheet using the contour method. For this purpose, an experiment with 8 operational steps including 3 sets of st37 sheets with thickness of 4, 6 and 8 mm in the dimensions of 100 × 100 mm are prepared and after the stress relief operation, they are cut by the mentioned cutting methods. After cutting processes and recording the temperature with a laser thermometer, the test specimens were prepared for contour method. According to the results, the highest residual stress is due to laser cutting in the sample with a thickness of 4 mm and its value is 142 MPa. The lowest residual stress obtained in wire-cut cutting and its value was 28 MPa. As the thickness increased, the amount of residual stress decreased in all methods. The slope of the temperature changes of the part from the moment of cutting to the ambient temperature is higher in laser cutting and the residual stress in this method is higher than the plasma and wire cut method.

Incremental forming is one of the new forming methods. Single-point incremental forming (SPIF) has shown significant potential for forming complex metal parts. In the single-point incremental forming, a spherical tool head moves along a pre-defined path to form the desired geometry. The aim of this study is to optimize the fracture depth and forming forces of the three-layer metal-polymer sheet by using the single-point incremental forming process. By using response surface methodology (RSM), a series of experiments were designed in which tool diameter, step down and spindle speed were considered as process input parameters. The influencing parameters in fracture depth and forming forces have been identified by using statistical tools (response table, main effect diagram and ANOVA). Analysis of variance was used to show potential differences between the means of variables by testing the population value in each sample, which enables it to show the effects of input variables on output variables. The results show that the forming forces increased and the formability decreased by increasing the step down and the tool diameter. The highest forming force is 1476 N and the lowest value is 1045 N. Similarly, the highest fracture depth is 8.8 mm and the lowest is 7.1 mm. The best conditions are achieved when spindle speed is 2340.9 rpm, tool diameter is 7.51978 mm, and vertical step is 0.329552 mm. In this condition, the fracture depth is 8.50552 mm and the forming force is 776.03 N.

Graphite has recently received a lot of attention due to its numerous applications as well as its unique structure. Machining and machining conditions optimization are very important in reducing machining forces among other benefits. In this study, the effect of machining parameters such as spindle speed, cutting depth and feed rate on the machining forces was investigated and the optimization of these conditions was done to minimize the forces. This research uses the design of experiments to optimize the initial parameters to minimize machining forces. These experiments are based on the response surface method and analysis of variances used to identify the most effective factors in machining forces. The values of the primary parameters that provide the experiments design software are considered to be the spindle speed between 1000 and 3000 rpm, the feed rate between 1000 and 3000 mm/min, and the cutting depth between 3 and 9 mm. The results show that the machining forces increase by increasing the cutting depth and feed rate and decrease by increasing the spindle speed. The results obtained from the optimization also indicate that the machining forces reduced to their minimum value at the feed rate of 318.2072 mm/min, the cutting depth of 0.9546 mm and the spindle speed of 2356.7439 rpm.

The many benefits of ultra-fine grained (UFG) tubes in the industry have led researchers to devise methods to increase the strength of tubes. Tubular channel angular pressing (TCAP) process is a new severe plastic deformation (SPD) technique to produce UFG tubes. In this research, at first, one pass of tubular channel angular pressing process with trapezoidal channel geometry is applied on Al-6061 samples. Then, mechanical properties such as yield strength, ultimate strength, hardness, and microstructure of the TCAPed samples are compared with the initial ones. In addition, effective strain and stress, processed load and deformation geometry during different stages of the tubular channel angular pressing process were investigated by finite element modeling. Finally, the results of the analytical model with finite element simulation were compared. It should be noted that the trapezoidal channel geometry has been used due to the high strain homogeneity and low force required for this channel geometry compared to other channel geometries. The microstructural results showed that the grain size of the initial samples was reduced from 92 µm to 785 nm in the TCAPed samples. The results of compression test showed that the yield strength and ultimate strength of the samples increased by 90% and 52%, respectively. The hardness of processed samples was also increased by 56% compared to the initial ones.

In this research, Constraint Groove Pressing (CGP) process, which is one of the most important and effective methods of severe plastic deformation processes has been studied. Ultrasonic assisted CGP (UCGP) process has been conducted to investigate and compare the effects of applying ultrasonic vibrations on the residual stress with the conventional method. Contour method was applied to measure the residual stresses distributions in the CGPed and UCGPed samples. Pure copper sheet samples were tested both with and without ultrasonic vibrations up to 2 passes. The measured values of the residual stresses indicated a relative reduction of stress in the presence ofultrasonic vibrations. By investigation of residual stress normal to the surface in thickness direction, it was observed that residual stresses are compressive on the edge and tensile in the middle of the thickness of the sheet. This reflects the self-balancing feature of residual stresses. In all conditions for both passes, residual stress reduced about 20MPa while using ultrasonic vibrations compared to traditional CGP method.

Single point incremental sheet forming (SPISF) has demonstrated significant potential to form complex sheet metal parts without using component-specific tools and is suitable for fabricating low-volume functional sheet metal parts economically. In the SPIF process, a ball nose tool moves along a predefined tool path to form the sheet. This work aims to optimize the formability and forming forces of Al/Cu bimetal sheet formed by the single-point incremental forming process. Two levels of tool diameter, step size, tool path and sheet arrangement were considered as the input process parameters. The process parameters influential in the formability and forming forces have been identified using the statistical tool (response table, main effect plot and ANOVA). Analysis of variance (ANOVA) was used to indicate potential differences among the means of variables by testing the amount of population within each sample, which enabled it to show the effects of input variables on output ones. A multi response optimization was conducted to find the optimum values for input parameters by response surface methodology (RSM), and the confirmatory experiment revealed the reliability of RSM for this approach.

In this study, the calibration constants of incremental step method have been determined by finite element analysis to calculate the residual stresses by the ring-core method. The calibration coefficients have been determined by simulation the uniaxial and biaxial loading. It is indicated that the loading approach has not effect on the calibration constants and they are unique. The uniaxial condition has been used to determine the calibration coefficients in the experimental method. To verify the determined constants, the calibration factors have been used to calculate the residual stresses in the case of uniform and non-uniform residual stresses. The axial and biaxial conditions have been studied and the results are in good accordance with applied stresses in simulations. In the uniaxial loading the measured residual stresses in finite element model completely accommodated by the applied stresses and presented formula and calibration constants determined the direction of the maximum principal stress by clearance less than 0.7%. Clearance of the measures stresses and applied stresses in the non-uniform case was about 1 %. An experimental test has been used to show the effectiveness of the obtained calibration coefficient by finite element analysis. Also, it is indicated that the results of the experimental test are satisfactory.

The measurement of residual stress in rail foot, according to manufacturing standards is mandatory. In this study, the ring-core method and the sectioning technique are used to measure the residual stresses. A calibration technique for the ring-core method has been explained and simulated by the finite element analysis. The calibration coefficient has been determined for certain parameters and various depths of the annular groove. The ring-core method has been simulated for the uniaxial residual stress field and it is observed that the maximum error in the maximum principal residual stress was about 13% which is about 5% of material yield stress. The residual stresses have been measured at the UIC 60 rail foot by the ring-core method and the sectioning technique, and the results are in a good agreement with earlier investigations in this field. Also, it has been indicated that maximum residual stresses on the rail foot are not in the longitudinal direction and in the subsurface of the rail foot, the maximum principal direction coincides with the longitudinal direction. Both methods indicated tensile residual stresses on the rail foot, but the ring-core method predicted 27% higher longitudinal residual stress on the rail foot in comparing with the sectioning technique.