مجله مهندسی ساخت و تولید ایران
سال نهم شماره 8 (آبان 1401)

The widely used chemical properties, significant conductivity, and medicinal properties of gold have led to the use of this material in most manufacturing, electronic, aerospace, and medical industries. Therefore, understanding the structure of this metal, the ability to assemble it in atomic dimensions, and improving the properties of this precious metal have been considered in nanoscience. For this reason, today researchers have tried to identify gold nanoparticles during the manipulation process and use an atomic force microscope to make the studies practical. In this article, to investigate the gold nanoparticle in the second phase of manipulation, the surface is explored experimentally by an atomic force microscope. The simulations have been done in a 3D environment. Among the important parameters investigated in this research, different geometries of gold nanoparticles, including spherical, cylindrical, and crowned rollers geometries, as well as the results of simulation with contact models with different geometries in the second phase of manipulation have been investigated. Studies have been carried out in two directions, x and y. The displacement of the gold nanoparticle has been investigated by drawing force, acceleration, and velocity diagrams, and finally, by examining the resulting diagrams considering the Hertz contact model, the maximum displacement has been calculated for simulating the process of spherical geometry and the lowest value for the contact model with crowned rollers geometry. Also, the amount of displacement along the x-axis for the cylinder and crowned rollers was about 3.5 and 3.6 times the displacement along the y-axis, respectively.

The design of progressive dies is complicated and time-consuming and needs high knowledge and experience. The layout design is one of the most important and complicated steps of progressive dies design which accuracy and cost of the die highly depend on it. In this step number of stations and the way of assigning punches in stations are determined. In the present research, a new method for optimizing the layout design of punches in different stations of progressive dies is presented. In this work, by considering the two objectives of minimizing the number of workstations and the balance of the die torque, and considering the various constraints that can exist between punches and using integer linear programming, a mathematical model for optimal layout design is proposed. A software is coded to implement this method. This software is developed in the Solidworks environment and the Visual Basic language. The input of the software is the punches used to create the sheet metal workpiece and the various constraints that exist between them. The output of the software includes the optimal distribution of these punches in different workstations. To check the performance of the presented software, its layout design has been compared with the designs proposed by expert designers. The output results showed that the designs proposed by the software are more suitable or similar to the designs proposed by the expert designers from the view point of the workstations number and the balance of the die torque.

Graphene sheets are subjected to various loads and events during the manufacturing process and their functional life, such as collisions with different masses or loads, which cause deformation, displacement, and vibrations in carbon atoms and sometimes rupture of graphene sheets. Graphene sheets with different lengths and impactors in different forms of selection and data collection tools are Lamps and Molecular Dynamics software. Simulation by Lamps software, which is a very accurate method and close to laboratory conditions; Based on the time step and the deviation of the central point of the page; The effect of some parameters such as mass, number of layers of graphene sheet, different shapes including cube, sphere and cone as well as different lengths of graphene sheet on sheet tearing was investigated. Therefore, with the increase in the mass of the spherical impactor and the increase in the length of the graphene sheet, the number of broken bonds increased, while the speed of breaking the bonds decreased with the increase in the mass of the impactor, and with the increase in the length of the graphene sheet, the speed of breaking the bonds increased. Then, by examining the effect of different impactor geometries (spherical, cubic, and conical), it was observed that the surface during the spherical impactor has the most displacement of the middle atoms of the plane and the conical impactor has the highest number of broken bonds compared to the two impactors. also with the increase in the number of layers, the amount of displacement of the atoms in the middle of the plane is less and the speed required to break the bonds has increased.

In this study, the elastic buckling and static bending of a functionally graded porous plate based on shear deformation theory have been investigated. The effect of the type and degree of porosity on the mechanical behavior of the plate using the principle of potential energy is the main goal of this research. The modulus of elasticity and mass density of the porous sheet are graded in terms of thickness according to two different distribution patterns. The system of partial differential equations governing the buckling and bending behavior of the plate is derived from Hamilton's principle. The Ritz method is used to calculate the critical buckling loads and transverse bending curvature. In order to validate the method and the results presented in this research, a comparison was made with the results presented in authoritative references and articles. In addition, the finite element modeling results have been compared with the present analysis. Also, a parametric study has been performed to investigate the effects of porosity coefficient and length to thickness ratio of plate on buckling and flexural properties of porous sheets with simply support boundaries. The effect of different porosity distributions on plate performance is discussed. In this research, by applying different porosity coefficients and changes in length to thickness ratio, buckling load and flexural behavior of a graded porous plate with a specific porosity distribution pattern has been investigated. According to parametric study of porous plate, the buckling load and the maximum transverse displacement on bending increase with increasing the porosity coefficient and the ratio of length to thickness. The results of this study are used to design of porous plate in various designs such as implants.

Due to increased pressures towards Just In Time (JIT) production, most organizations tend to produce in make to order (MTO) environment, leading to competing with other manufacturers and responding quickly to customers. In this regard and according to the mentioned points, the purpose of this paper is sequencing in the Mixed-model assembly line (MMAL) in MTO environment by considering available to promise (ATP) approach. Mixed-model assembly line could be a form of line capable of manufacturing numerous models of a product on one line. In this paper, a particular parallel MMAL balancing problem is studied in a make-to-order production system. First, the orders are determined based on the connected profit and a decision support method to order acceptance/rejection with attention to ATP is considered. By developing this method and presenting a mathematical model, delivery value and due dates are calculated with attention to stock. Then, a mixed formulation is presented to determine the accepted customer orders properly according to orders due dates that warrants the customer orders are not released early or late. The model determines subsequent objectives optimizing the idle time and utility work of labors in the manufacturing line and optimizing the entirety earliness and tardiness costs with attention to the specified precedence of customer orders. To validate the performance of the proposed model, various test problems in small size are solved using the CPLEX solver, and compared with the Lagrangian relaxation method.

Thickness distribution is one of the important parameters in the sheet metal forming processes. This paper investigates the forming of flat cylindrical cups made of steel using the hydrodynamic deep drawing process via experiment and simulation. At first, the process was simulated using the ABAQUS finite element software. Afterward, the results of the finite element simulation are compared with results of the experiments. Comparing the results showed that the thickness distribution and punch force have an acceptable agreement in the experiment and numerical methods. Then, using the validated finite element model, the effect of the process parameters including the friction coefficient between the punch and the sheet, the friction coefficient between the blank holder and the sheet, the corner radius of the punch and the die, as well as the gap between the blank holder and the die on the maximum thinning of the steel cups have been investigated. Finally, the obtained results revealed that the corner radius zone of the punch is the critical forming zone since the maximum thinning occurs in this region. Also, by increasing the friction coefficient between the sheet and the punch, the maximum thinning decreases by 10% at the corner radius zone of the punch. In addition, by increasing the friction coefficient between the sheet and the blank holder, the maximum thinning increases by 20%. Likewise, by increasing the corner radius of the punch and the die, the maximum thinning decreases by 25%, and also, by increasing the gap between the die and the blank holder, the maximum thinning decreases by 10%.