مجله مهندسی ساخت و تولید ایران
سال نهم شماره 9 (آذر 1401)

Micro bending is a forming process to create bends with very small radius and it is used in the production of sensitive parts of the electronics industry. The key point of the micro bending process is the production of parts while maintaining high dimensional accuracy. One of the defects effecting the dimensional accuracy and tolerance of these parts is the spring-back phenomenon which is directly related to the parameters of the tool and the material. In the present study, the spring back behavior of C12200 copper sheet in a new W-shaped bending die has been studied. Also, the effects of process factors including punch radius, die radius and sheet thickness to grain size ratio it was analyzed using finite element simulation and experimental tests. The results showed that the highest spring back angle is obtained for the grain size of 33 µm and the lowest for the grain size of 133µm. The results showed that the best conditions in terms of reducing the spring back angle are obtained in the lowest ratio of sheet thickness to grain size.

The development of additive manufacturing processes in the last several decades has made the manufacture of parts made of various materials quite significant. Fused deposition modeling, being one of the most widely used additive manufacturing processes, enables the creation of complex composite parts. In this technique, the material comes out of the system's nozzle in the direction of the system's movement due to the melting of the filament in the nozzle and its momentary progress. Because of their numerous applications, micro-composite materials are considered one of these materials. However, the technique of manufacturing the composite has an influence on the behavior of the component; for this purpose, in this research, ABS-Ni micro composite filament was employed and printed with the FDM 3D printer developed by the researchers of this article, and it was compared to other polymers such as PLA, ABS, and TPU. The mechanical and microscopic behavior of the polymers made with this approach, have been investigated. Furthermore, similar parts manufactured using the DLP approach were compared to this method. According to the results, a 15% increase in nickel powder reduced tensile strength by 11.62%, which is equivalent to a 50% drop in the volume of infill in the non-composite ABS part. When comparing the FDM and DLP methods, the photopolymerization operation can diminish the strength of the products by 2 times despite the higher surface quality and more integrated structure. The elongation of TPU polymers was determined to be 26 times higher than that of other polymers.

Metal orthopedic plaques can cause problems such as osteoporosis in the area under the plaque, the release of unwanted corrosion products in the body due to the wear of metal plaque and as a result of infection, as well as surgery to remove the hard metal plaque. Therefore, polymer plaques and composite plaques can be a good substitute for metal plaques. In the current research, the effect of polymeric material type on the mechanical properties of two bone stabilizing plaques, one flat and the other curved, both with a row of holes and high clinical application, is investigated using the three-point bending test. For this purpose, samples were made of ABS, PLA and PETG using additive manufacturing method of 3D printing and FDM melt deposition method. The test results showed that the highest strength and flexural modulus for both models of orthopedic plaque samples is related to PLA material. For the flat plaque, the bending strength and bending modulus of PLA compared to PETG are 58% and 100% higher, respectively. For the curved plaque, the bending strength and bending modulus of PLA compared to PETG are 49% and 100% higher, respectively. It was also seen that although the strength and flexural modulus depend on the dimensions and geometry of the models, but the ratio of changes in these properties, especially the flexural modulus, is almost constant.

The upcoming article investigates the mechanical properties of FDM printed composite material with continuous glass fibers and ABS matrix. The printer designed to produce this composite uses ABS polymer filament and ABS/GF pre-impregnated composite filament. Pre-impregnated filament is designed and produced by a filament production line. In order to build a 3D printer with composite printing capability, a normal FDM printer was subjected to modifications in the structure and nozzle. Finally, after building a 3D printer with composite printing capability, tensile and bending samples were printed and the mechanical properties were tested according to standard instructions. The obtained properties were also compared with the printed pure ABS sample. The modulus of elasticity and tensile strength of the ABS/GF sample has increased by 540% and 260%, respectively, compared to the printed pure ABS sample. Based on the three-point bending test, the modulus and flexural strength of the printed composite have increased by 140% and 100%, respectively, compared to the pure polymer sample. The duration of making composite by FDM printer is not much different compared to polymer printing, but due to the presence of continuous glass fibers or other reinforcing fibers it greatly improves the mechanical properties of the manufactured sample, that's why the use of this method can be justified compared to FDM printing with pure polymer method.

One of the limitations of traditional roll forming is the production of parts with fixed cross-sections, so the flexible roll forming process was created to produce parts with variable cross-sections. The most important defects of this process, include warping, spring back, deviation from the desired position of the edge, wrinkling of the edge, and fracture in the corners. In this paper, the numerical and experimental investigation of the effect of heating the sheet during the flexible roll-forming process on the spring back defect was discussed. For this purpose, the simulation of the thermomechanical finite elements of the process was carried out in Abaqus software. Experimental tests were conducted using a flexible roller forming machine made in Shahid Rajaee University of Tehran along with additional local heating mechanisms in five temperatures 25, 100, 200, 300, and 400 to validate the simulation results. A laser thermometer was used to measure the sheet temperature. To prevent laser light reflection and error in temperature calculation, the sheet was matted by carbon coating. Results showed that with the increase in temperature, the spring back compared to forming at ambient temperature decreased in both types of aluminum, and with the increase of yield strength, the spring back increased. By increasing the temperature up to 400°C compared to the ambient temperature, the spring back in thickness 1mm and 1.5mm, decreased by 33.5 and 41.2%, respectively; also, the comparison of simulation and experimental results showed a good agreement.

Turbine engines mainly have non-homogeneous welded joints with various fusion-welding methods. In this research, the input energy was investigated as the main parameter with different in the voltage and beam current with welding speed of 6mm/s and focal radius of 1mm of the electron beam welding process. The connection quality of the samples after welding was determined with three characteristics of tension test and welding geometry along with examination of the fracture surface. It was observed that with the increase of input energy, the depth of penetration and the tensile strength of the connection increased. In this tensile test, three samples showed a tensile load of more than 80% of the base metal. It was also shown that failure in all the samples occurred from the interface area of 4140 steel with the fusion zone. With the increase of input energy, the heat affected zone increases. Comparing two samples with the same voltage and different beam current, and two samples with the same beam current and different voltage, shown that the influence of the beam current on the joint strength is significantly higher than the effects of beam voltage. Fractography shown that for the beam energy higher than 230 J / mm, the weld flexibility decreases. It can be explained by the high temperature and fast cooling rate in fusion zone for this sample. It was also shown that the acceptable tensile strength and suitable depth of penetration obtained in V40I40 sample with the beam energy of 267 J / mm.