مجله مهندسی ساخت و تولید ایران
سال دهم شماره 2 (اردیبهشت 1402)

Electrochemical deburring is a common method for removing small and micron scale turning additives. This study investigated the impact of ultrasonic waves on the parameters of the electrochemical deburring process. The parameter of material removal rate was investigated in two cases with and without the use of ultrasonic waves. Electric current, electrolyte temperature and ultrasonic power were input variables and other process parameters were considered constant. In the experiments, electrolyte of 6 liters of water and 20 grams of sodium nitrate, an ultrasonic transducer with a frequency of 28 kHz and a workpiece made of brass alloy C86300 were used. According to the results, the material removal rate increases with an increase in electric current in both cases without and with ultrasonic and remains constant after applying a specific current. where ultrasonic waves were applied, the material removal rate in the current of 2.7 and 2 amps increases from 20 to 100%, respectively, compared to the case without applying ultrasonic waves. The investigation examined the changes in the electric current as temperature increases from 25 °C to 40 °C in both in both mentioned cases. The results showed that the increase in temperature in both cases leads to an increase in electric current. Also, at any given temperature, the amount of increase in electric current in the state with the application of ultrasonic waves is greater than in the case without ultrasound, and the highest increase in the electric current has occurred by 40% for a temperature of 25 ℃.

The friction stirring process is one of the new processes in the production of metal matrix composites. Choosing the right parameters for the uniform distribution of particles in this process is vital. One of the important parameters in this process is the number of processes passes and the change in the direction of the tool rotation between the process passes. In this study, the effect of the number of passes and the change in the tool rotation direction on the distribution of SIC particles in aluminum 6061 has been investigated. Aluminum 6061 is one of the hard deposit able aluminum alloys, in which magnesium and silicon are the main elements. First, samples are produced using one, two, and four process passes, with and without changing the tool rotation direction between the process passes. Then, the distribution of particles in the base metal is studied using macro- and microscopic photographs. The results showed that the number of processes passes and the change in the tool rotation direction have a significant effect on the uniform distribution of particles.

Composites containing glass fiber reinforcement are used in important industries such as aerospace, automotive, and petrochemical due to their low weight, high abrasion resistance, and excellent resistance to ultraviolet light. Achieving a part in the desired shape and with a suitable quality surface is the main challenge for researchers and machining specialists. Due to the heterogeneous and anisotropic structure of composite materials reinforced with glass fibers, the machining of these materials often leads to failures such as matrix cracking, fiber pull-out, delamination, etc. on the surface of the workpiece. The failure behaviors are not caused by the heterogeneous and anisotropic structure of the composite but rather by the machining methods and the interaction between them. One of the most influential factors on the surface quality of fiber-reinforced composite parts is fiber orientation, which is studied in this research. Examining the orientation of glass fibers in 3 directions of 0 (zero), 45, and 90 degrees on the structure of the final surface of the epoxy-fiber composite in this research showed that the roughness of the surface increases with the increase of the fiber angle from zero to 90 degrees. Also, the obtained results showed that the delamination of the workpiece surface in the direction of 45 degrees is greater than in the two directions of 90 and zero degrees.

In many industries that are related to machining processes, the basic factor to reduce the overall cost of production is the selection of ideal machining conditions. The piece temperature is a very effective factor in machining processes, and in this study, the effect of this parameter on the behavior of the chip and the forces on the tool in the machining of CK45 steel has been investigated. Three preheating temperatures of 25, 70, and 100°C were used to preheat the part before turning, and the variables of chip formation were investigated. Also, by developing a finite element model (FEM) of the process, the machining of the part and the formation of chips in the material were simulated, which shows a good agreement with the experimental tests. After FEM validation, the amount of machining force, thermal stresses and wear in the process was evaluated with the help of FEM. Based on the obtained results, it was found that the maximum curvature of the chip occurs at the preheat temperature of 70 degrees Celsius. Also, the maximum deformed thickness of the chip was at a preheat temperature of 25 degrees and the lowest value was at a preheat temperature of 70 degrees Celsius. The forces applied on the tool in the Y and X directions increased with the decrease in temperature, but the heating rate of the tool tip increased up to the machining temperature of 70 degrees Celsius, and after that, due to the reduction of friction, it has been significantly reduced to about 60%.

Magnesium and its alloys have found a wide range of applications in medical industry and manufacturing of absorbable bio-implants because of having a modulus of elasticity similar to bone as well as having biocompatibility and biodegradability characteristics. Moreover, employing magnesium implants with a porous structure can lead to an increase in the rate of bone replacement instead of the initial absorbable implant. On the other hand, by adding hydroxyapatite reinforcing particles to magnesium and its alloy, their mechanical properties and corrosion resistance may be improved. In this paper, the effect of magnesium particle size on compressive strength of Mg/hydroxyapatite porous bio-composites has been studied. The magnesium and composite specimens with non-porous and porous (with a volume porosity of 24% and 58%) structures were produced using powder metallurgy method. For this purpose, two types of magnesium powder with particle sizes of 63 µm and 250 µm, hydroxyapatite particles as reinforcement, and ammonium bicarbonate particles as space holder, were used. The results of the uniaxial compressive tests revealed that the strength of all the pure and composite specimens fabricated by 63 µm powder has improved up to 103%, compared to those of the specimen fabricated by 250 µm powder. In addition, for both amounts of volume porosity, the composites offer a higher compressive strength than that of the pure specimens.

In this research, the effect of rubber layer characteristics such as hardness and thickness of the rubber layer on the thinning of metallic bipolar plate channels at a constant depth was investigated experimentally and through simulation. The accuracy of the simulation results was evaluated using experimental data. For the experimental stages, a die with parallel grooves and a 60-ton press were used to apply force to the forming die. According to the results obtained, reducing the hardness of the rubber layer will lead to a more uniform thickness distribution at the same depth. The minimum thickness of the formed sample using a Shore A 55 rubber layer was 0.703 mm, which represents a 1.3% improvement in thinning compared to Shore A 90 hardness. Furthermore, increasing the thickness of the rubber layer improves the shaping process, and based on the results at the same depth, a thicker rubber layer will result in the formation of microchannels with a more uniform thickness distribution in critical areas.