مجله مهندسی ساخت و تولید ایران
سال نهم شماره 2 (اردیبهشت 1401)

In this research, numerical simulation of laser bending process of the metallic sheet with curved irradiating scheme is investigated. For this purpose, the commercial ABAQUS software is used for performing the finite element simulations. The used sheet metal is the low carbon mild steel with thickness of 1 mm. Using the stress field obtained by the numerical simulations and analyzing the residual stresses in different directions located on the laser irradiation path, the mechanics of deformation and the reason for sheet bending in the laser bending process with curved irradiating scheme are investigated. The results show that the curved irradiating scheme can properly bend the steel sheet. Also, the effects of laser power, laser scanning speed and laser beam diameter on the average value of displacements of the laser-bent sheet with curved irradiating scheme are investigated. The results show that with increasing the laser power, the average value of displacements of laser-bent sheet with curved irradiating scheme is increased. Also, it is concluded from numerical simulations that with increasing the laser scanning speed, the average value of displacements of laser-bent sheet is decreased. It is proved that with increasing the laser beam diameter, the average value of displacements of laser-bent sheet is decreased.

One of the major challenges in the selective laser melting process is the generation of residual stresses in the processed parts. The residual stress can have detrimental effects on the dimensional accuracy, mechanical properties and performance of the part. In most industrial components, such as turbine blades, the cross section of the part changes along its length which can affect the amount of residual stress. The most important parameters of selective laser melting process include laser power, scanning speed, layer thickness and hatch spacing. These parameters are effective on the thermal profile created during the manufacturing process. Therefore, they can play an essential role in the formation of residual stresses in parts. In this paper, the effect of hatch spacing parameter on the residual stress magnitude of Inconel 625 samples with different cross sections has been investigated experimentally; so that the energy density does not exceed the appropriate range for the density of the samples. Using the non-destructive X-ray diffraction method, the residual stresses measured in the center of the sample surface and the intersection of the two variable sections of the samples. The results showed that the use of a larger hatch space significantly reduces the amount of residual stress. Also, the comparison of the amount of residual stress in the center of the surface of the lower and upper parts of the samples shows that the amount of residual stress in the interface between the two cross sections is reduced by almost half.

The present study investigated the feasibility of producing strong and defect-free joints between 1050 aluminum and pure copper sheets by micro friction stir welding using ordinary and new tools. By analyzing the results of the tensile test and signal to noise analysis, the average maximum ultimate tensile strength of the joints is reported to be 88 MPa, when using the parameters of rotational speed, traverse speed, and offset of the tool with levels of 2400 rpm, 40 mm/min and 0.25 mm. The variance analysis also showed that the parameters of rotational speed and traverse speed had the most significant effect on the joints' tensile strength. The maximum and minimum values obtained from the microhardness test were recorded for the weld nugget zone and the heat-affected aluminum zone, respectively, equal to 192 HV and 21 HV. The X-ray diffraction test results on optimal samples showed intermetallic compounds such as CuAl2 and Cu9Al4 in the welding area. The tensile strength of the joints created is strongly dependent on the formation of these intermetallic compounds.

In the real conditions the composite structures set into the various environment conditions like thermal cycling. The aim of this work is to investigate the effect performing the thermal cycling on the absorbed energy capability of fibers metal laminates with aluminum skin and glass fibers/epoxy composites core with the various stacking sequence of glass fibers. For this reason, in the first step, the FMLs with two unidirectional configurations (0 /0 /0 /0 ، and 90 /90 /90 /90) and two bi-directional configurations (+45 /-45 /-45 /+45 and 0 /90 /90 /0) were fabricated. Then, the samples were aged by 0, 1, 10, 30, 50 and 90 thermal cycles. Each thermal cycle was heating the samples up to 100 C for 15 min, maintaining in this temperature for 5 min, and cooling them down to the ambient temperature for 15 min. After that, measuring the absorbed energy and characterizing the mechanisms were investigated by Charpy impact test, macrostructural method and microscopic analysis. The obtained results showed, up to 10 thermal cycles in the FMLs with unidirectional configurations, the absorbed energy capability has improved. After that, it had the reducing trend. The minimum and maximum sensitivity of absorbed energy capability in the thermal cycling were seen into the samples with the configurations of +45 /-45 /-45 /+45 and 0 /90 /90 /0 , respectively. The macrostructural investigation was showed, the delamination between fibers plies was the main failure mechanism in the FMLs, after performing 90 thermal cycles. By using the microscopic analysis was found that the thermal cycling caused to reduce the adhesion between glass fibers and epoxy matrix into the FML.

This paper presents a dynamic model of a robotic manipulator with a time-varying structure in a fluid medium. In addition, it provides more access for end-effectors via new manipulator structures design that used revolute-prismatic joints. While the new manipulator structure’s model is obtained commensurate with its application in the fluid environment. Thus, by considering the hydrostatic and hydrodynamic interaction forces that implemented between the fluid and the robot arm, the final motion equations of the robot are evaluated. However, the change in the robot’s structure and its fluid implemented action and reaction force, caused the obtained motion equations differ from similar systems with time-invariant structures. As a result, the final equations are time dependent. This is evidenced by comparing the results obtained from the robot's behavior in air and fluid medium. Thus, in addition to the rotational motion, in the linear motion of the prismatic joint, due to the incomprehensibility of the fluid, a resistive force is applied by the fluid to manipulator links. In this regard, the dynamic model is obtained using the recursive Gibbs-Apple formulation and then simulated in MATLAB software. The equations are simulated and discussed based on the different links cross-sectional areas, various environments, as well as the effect of each of the hydrostatic and hydrodynamic forces. As a result, the robot's motion in the water medium is reduced by 60% relative to the air environment. The robot's motion is more affected by the drag force than other resistive forces.

Al-Si alloys are commonly used in the manufacture of auto parts, including pistons. Although this alloy offers desirable properties for use in pistons, several microstructural properties, such as the presence of needle-like silicones or dendrites, interfere with the performance of the components produced. In this study, ZrO2 reinforcing particles were used to produce metal-based composites by friction stir process. First, the microstructural characteristics of the stir zone (SZ) of the samples produced were studied using a optical microscope. The results showed that the friction stir process improves the microstructural properties of the base metal, including the size of the silicon particles, and the distribution of these particles in the base metal. Then the particle distribution and bond quality between ZrO2 and aluminum reinforcing particles were investigated using SEM. Then, hardness and wear tests were performed to determine the wear and hardness of the composites. Pin-on-disk wear tests were performed at speeds of 1 m / s and 2 m / s and normal applied loads of 5 N, 10 N and 20 N. The wear test results showed that the wear resistance of the produced composite was improved by about 172% compared to the base alloy.