مجله مهندسی ساخت و تولید ایران
سال نهم شماره 4 (تیر 1401)

The aim of this study was to investigate the effect of laser power variation on joint connection characteristics in the additive manufacturing (AM) process by depositing Inconel 718 powder on an Inconel 738 substrate in order to reconstruct defective gas turbine blades with a circular economy approach. Laser metal deposition (LMD) is a layer-by-layer fabrication technique used to manufacture and reconstruct critical and strategic parts. For this purpose, deposition with different power of 150, 250 and 350 watts was performed on the substrate. Some features such as geometric dimensions, number of pulses per layer and microstructure of the samples were studied. Comparing the results, it was found that with increasing strength, integrity, joint connection thickness and substrate melting depth increase. In contrast, with increasing power, surface porosity, and size deviation from the design dimensions, and the number of pulses to complete each layer decrease. Each deposition layer with power of 150, 250 and 350 watts was completed with 17, 11 and 9 pulses, respectively. By increasing the power from 150 watts to 350 watts, the surface porosity decreased by about 90%.

Ultrasonic suspension can be used for a wider range of particles due to its independence from the material and its properties, For the possibility of suspension, and has a high potential for the transfer and movement of particles in a controlled manner. Suspension and separation of particles are due to acoustic force. Two parameters namely acoustic contrast factor and volume of particle are more effective in magnitude of this force. The first determines the direction of particle movement towards the node or antinode and increasing the volume of particles causes to increase acoustic force and thus increasing the velocity of particles in the fluid medium. In this paper, simulations were performed by solving the equations of wave and acoustic pressure in a fluid medium and tracking particles in the fluid flow from the inlet. Then, using the simulation results, a laboratory set-up was designed and fabricated. According to results, a good agreement was observed between the simulation and experiment data. Polystyrene and ABS particles were suspended in water and the velocity of larger particles increased.

Nowadays, the alignment of broken bones using unilateral external fixators has been popular. However, their adjustment to hold bone pieces from four areas and move them by loosening the screws for ossification is associated with errors and consequently various problems. The present study aims to assess the stability and strength of a unilateral external fixator equipped with four motors, which is able to accurately move the bone pieces from four areas using the motors without error. The device is designed in SolidWorks software. Then, its simulations and analyzes are performed using the finite element method in ANSYS software. The results of the simulations in dynamic mode in a period of 1 s, compressive forces of 150 N and 130 N, and eight-point bending force of 150 N confirm the stability of the device and by applying a twisting torque of 8 Nm, the device still maintains its stability. The results show that the designed device has the necessary stability, rigidity, and strength to keep the bone stable. Moreover, using the electronic control unit of the motors, this device can precisely move the bone pieces for ossification. Therefore, it is recommended to manufacture and use this device in orthopedic surgeries.

In this paper, the effect of current intensity on changes in the microstructure of the hot resistance spinning of commercially pure titanium alloy has been investigated. For this purpose, a set-up for applying resistance heating to the sheet was installed and the configuration of the machine was designed and built in such a way that during the spinning process, resistance heating can be applied simultaneously and titanium sheets can be made into cones. The incomplete part was subjected to the hot resistance spinning process. Then, by conducting experiments in different forming conditions with a change in the intensity of the passing current at a constant thickness and feedrate, different parts were obtained and the microstructure of the material and its granulation, in different forming states and in the part of its various aspects have been studied. The results from this research show that the force applied in spinning in resistance heating at all current intensities has caused the material to become fine. But from a certain current intensity, the material has more time after the completion of recrystallization to remain at higher temperatures, and because of this, there is a greater possibility for the growth of recrystallized grains. Also, the hardness changes in the Vickers scale in the intensity of different currents show that with the increase in the intensity of the current in all parts of the piece, its hardness has increased.

In this paper, the design, fabrication and testing of a single L-shaped adhesive bond between a composite sheet and an aluminum piece under tensile loading has been performed experimentally. In this experimental study, nanographene sheets with different weight percentages have been used to strengthen the composite and structural adhesive (compatible with the composite phase phase resin) to improve the mechanical properties of the joint. The effect of changing the base length of the aluminum L-shaped piece on the bond strength has also been investigated. 12 bonding modes with a combination of weight percentages of 1.0 and 0.3 for multilayer and weight percentages of 0.1, 0.3 and 0.5 for adhesive were made and examined by considering 5 repetitions of the test. has taken. By comparing and examining the tensile test results of the samples and photographs taken by scanning electron microscopy (SEM) of the separation of the multilayer and the L-shaped piece at the separation site, it was found that the bonding combined with zero weight percentage for multilayer and The weight percentage of 0.3 for the adhesive has the highest tensile strength. This means that the addition of nano-graphene without surface-modifying agent to the multilayer reduces the tensile strength and adding it to epoxy resin epr 1080 as a homogeneous adhesive with the composite improves the tensile strength of the joint. Finally, the effect of increasing the length of the overlap area of ​​the two adhesive pieces was investigated.

In the present study, the behavior of circular plate made of fiber-metal laminates with curvilinear fiber subjected to low velocity impact is investigated using an analytical method. The composite layers are made of glass-epoxy that placed between two layers of Aluminum 2024-T3. Differential equations of motion are formulated using the spring-mass model and appropriate initial conditions for loading and unloading stages. The deformation of aluminum were idealized as rigid-perfectly plastic and the composite layers as linear elastic. Using the principle of minimum total potential energy, applying the Von Karman strain and by neglecting the contribution of the in-plane displacements and bending strain energy, the nonlinear relationship between the contact force and deflection is derived. Also, a method for calculating the average stiffness of the plate is developed and employed to estimate the internal damage due to delamination. The effect of the layup and geometric parameters of the plate and the impactor on the plate response is investigated. Different functions are examined to describe the shape of the deformed plate under loading and the results are compared with the experimental data for validation purpose. Furthermore, an investigation of the possible performance improvements of a composite plate under impact loading through the use of the variable stiffness concept with curvilinear fiber is presented. The analytical results indicate the alteration in load paths and favorable stress distributions within the variable stiffness laminates. However, the maximum deflection and the contact force of variable stiffness laminates are similar to the conventional, constant stiffness ones.