Iranian Journal of Materials Forming
Volume:10 Issue: 3, Summer 2023

The “Iranian Journal of Materials Forming (IJMF)” is an international open access journal in the fields of materials deformation and forming processes, which was established at Shiraz University in 2014. The journal is pleased to receive papers from scientists and engineers from academic and industrial areas related to all manufacturing processes. In addition, all deformations, including the elastic and plastic behaviors of materials and deformations due to failure, are part of this journal's field of interest. The quality and credibility of the journal have been ensured by appointing some of the most well-known professors in the world as members of its editorial board. In addition, the wide range of the selected referees in this issue is a sign of its scientific quality. It is a matter of pride that for the third year this journal has been successfully released quarterly and the third issue of the year was published in 2023.

In this study, we investigated the influence of process parameters on the mechanical properties of AZ91C magnesium alloy joints produced by friction stir welding (FSW). A Taguchi L9 orthogonal array was employed to design the experimental matrix, and the input variables were analyzed. Tensile strength and hardness values were measured for different input parameters, and their interactions were assessed through interaction plots for ultimate tensile strength (UTS) and Vickers hardness (HV). The signal-to-noise (S/N) ratios were calculated, and S/N ratio plots were generated to further understand the effects of the input parameters on the mechanical properties. Microstructural evaluations were carried out on the base metal and stir zone (SZ) of the specimens produced under various process conditions. Additionally, the appearances of the FSW samples with the minimum and maximum tensile strengths were compared. The results revealed complex relationships between the process parameters and mechanical properties, with both main effects and interactions playing significant roles in determining the performance of the FSW joints. Notably, an optimal combination of process parameters (tool rotation speed of 1250 rpm, welding speed of 40 mm/min, and plunge depth of 0.3 mm) resulted in the highest ultimate tensile strength (UTS) and hardness (HV) values. Microstructural analysis showed that FSW significantly refined the grain size, contributing to the improvement of mechanical properties.

In this study, the effects of changing die angle on drawing force during cold drawing of a 410 stainless steel tube is evaluated. For this purpose, simulation of the process by Abaqus software was performed and the results were compared with the experimental findings. By applying Johnson and Cook's equation the flow behavior of the steel was also assessed during cold drawing., Ring compression tests were performed to determine the coefficient of friction at die-tube and tube-plug interfaces. Furthermore, strain distribution during the process was considered to evaluate the mechanical behavior of the steel. An essential aspect of the work was to estimate the required drawing force, by lower and upper-bound theories. It is illustrated that the lowest drawing force is obtained at the half die angle of 16°. At this angle drawing force of 164.6 KN was estimated by simulation. Experimental results at half die angle of 16° indicated a drawing force of 175.1 KN which illustrates about 5% discrepancy with simulated results. Also, the radial strains at this die angle had the highest value in comparison with other half die angles of 12 and 14 degrees. The highest amount of strain was observed in axial direction of the drawing process at the half die angle of 16°. Lowest values of residual stresses were developed at this die angle.

Cyclic extrusion compression angular pressing (CECAP) is a novel severe plastic deformation (SPD) method applied for improvement of mechanical and metallurgical properties of materials. In this research, finite element analysis and response surface method were considered for CP-Ti in CECAP process. Temperature, input extrusion diameter, exit extrusion angle, shear factor and longitudinal distance of input extrusion to ECAP region were selected as input parameters to study strain distribution on the current process. The analysis of variance (ANOVA) was developed for current work, and the results showed that input parameters of input extrusion diameter and shear factor, and the interaction of the temperature and longitudinal distance of input extrusion to ECAP region, and the shear factor and longitudinal distance of input extrusion to ECAP region considerably affect the strain distribution. The hardness measurement in the section A at the points near to center and outer surfaces of sample showed the hardness of 21 and 24 HRC respectively, where, the maximum difference for hardness was achieved about 12% throughout the cross section which is in suitable agreement with the strain distribution model. Moreover, optical microscope (OM) both current CDECAP and conventional CECAP showed that the majority of deformed grains were enlarged. The average deformed grain size for current CECAP was reduced to 100 nm, which is considerably smaller than for conventional CECAP with average grain size of 300 nm. Furthermore, the load-stroke diagram was achieved by experimental test and compared by the results achieved from numerical model, and the results showed a good agreement between them.

Nonwoven structures consist of fibers with different orientations. Studying the mechanical behavior of nonwoven materials is very complicated and laborious in terms of the random nature of their constituent fibers. In this study, a suitable approach based on existing models is proposed to predict the stress-strain behavior of electrospun polyimide (PI) non-woven fabric as a function of the volume fraction, orientation distribution, and stress-strain behavior of its constituent fibers. 18 different discrete orientations from 0 to 180 degrees are considered to specify the fiber orientation distribution in the fabric. To avoid difficult and complex experiments on the fibers constituting the nonwoven fabric, the constants and characteristics of the stress- strain curve of a single fiber were determined by fitting the fabric stress- strain curve predicted by the model to the results of the fabric experimental tensile test. The comparison among the predicted stress- strain curves by the model and the experimental results for PI nonwoven fabric in two different loading directions of 0 and 45 degrees shows the validity of the method used in obtaining the stress- strain behavior of the fabric.

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.

The morphology of the α-phase in titanium alloys considerably affected their physical and mechanical properties. In this research, the effect of applied strain and inter-pass times on the morphology of the α-phase was studied in the two-step hot deformation process. Hot compression tests were performed at 900 ºC and 0.001 s-1 while the strains in the first and second passes were set as (first cycle: 0.6 and 0.3) and (second cycle: 0.3 and 0.6) respectively, with various inter-pass times. The work softening parameter obtained from the stress-strain curves showed that the proper time for globularization of α-layers for the first pass strain of 0.6 was 240 s and for the second strain of 0.3 it was 240 and 300 s. Microstructure results indicated that the first pass strain of 0.3 and the inter-pass time of 240 s were the optimum conditions for globularization of α layers.