مجله مهندسی ساخت و تولید ایران
سال هفتم شماره 12 (اسفند 1399)

Metal sandwiches are a new class of ultra-lightweight materials made from a porous metal core and two outer metal plates. High strength and high energy absorption capacity, resistance to heat, and also fast and inexpensive recyclability make these materials ideal for use in many industries including automotive, aerospace, oil, energy and construction industries. Considering the advantages of friction stir welding, the connection of these plates using this welding technology can be used industries for welding of bimetal sandwiches. In this research, feasibility of using frictional stir welding to prepare metal sandwiches with a core of aluminum foams and copper covers was investigated. The investigated parameters were tool rotational speed, in three levels of 2000, 2500 and 3000 rpm, and tilt angle in two levels of 5 and 7 degree. The cross-sections of the joints were investigated for weld quality which confirmed a successful joining. Tensile tests were carried out to evaluate the joint strength. It was concluded that the effect of tool rotational speed on the weld strength is much higher than the effect of tilt angle and has a reverse relation with tensile strength. The best strength which was 18.8 MPa was obtained with a tool rotational speed of 2000 rpm and a tilt angle of 5 degree.

In this paper, the effect of the die geometry on the joint strength of the clinching process is investigated. The AA3105 aluminum sheets are joined using different die geometries. After determining the suitable range of the joining load (25-32kN), the effect of the die geometry on the joint strength is considered, using shear and peel tests. The results indicate that the die geometry and punch penetration depth are the most important parameters affecting the joint mechanical interlock and neck thickness. In the range of proper mechanical joint, the die geometry has a great effect on the strength and geometry of the joint, while the effect of clinching load is negligible. The investigated punch diameters were 4, 4.5, and 5mm, where the optimum punch diameter was 5 mm. At the diameters higher than the optimum value, due to the low clearance between the punch and die, the neck thickness is reduced, leading to the joint failure. However, at the diameters lower than the optimum value, due to the higher clearance, the material flows easily from the bottom side, leading to a weakness in the mechanical interlock and joint strength. Although a negligible effect of clinching force on the joint strength, its effect on the joint energy absorption capacity is meaningful. As the joint energy absorption capacity will be the highest at an optimum clinching load. The highest joint strength was achieved at the punch diameter and clinching force of 5mm and 30kN, which resulted in the joint shear strength of 1355N.

Chatter vibration is one of the undesirable phenomena in machining processes. The chatter in metal cutting typically causes severe noise, reduced workpiece surface quality, reduced tool life, and a significant reduction in machining efficiency. Therefore, developing suitable methods that increase stability and improve cutting performance is necessary to control tool vibrations in machining processes. Magneto-Rheological (MR) fluid damper is among the equipment developed to dissipate vibration energy in various industries and has the potential to be used in machining processes. In this study, an MR fluid damper containing Fe2O3 nanoparticles is designed and fabricated to dampen the chatter vibrations during the cut-off turning process. The fabricated damper is then experimentally tested in the cut-off turning operation of steel work samples. In the empirical experiments of this research, the tool vibration in damped and non-damped modes is evaluated and compared through measuring the tool acceleration signals. The obtained results show that by using the MR fluid damper, the tool vibrations are significantly reduced, especially in the case of chatter occurrence.

The advancement of AM technologies has resulted in producing parts of high quality and reduced manufacturing time. The purpose of this study is to simultaneously optimize the values of two response variables, build time and surface roughness. In order to achieve the best values for build orientation and other process parameters including raster width, layer thickness, infill percentage, and raster angle, the effects of process parameters and response variables were adopted by the Design of Experiments approach to develop empirical models using Response Surface Methodology. The experimental parts of this research were conducted using an inexpensive and locally assembled FDM machine. Fifty runs for two different geometries, namely cylinder and 3DBenchy, were performed using the Rotatable Central Composite Design, and each process parameters was investigated in two levels in order to develop empirical models. Also, a novel optimization method, namely, the Posterior-Based method, was accomplished to find the best values for the response variables. The results demonstrated that not only build orientation and layer thickness have notable effects on both response variables but also build time is dependent on raster width and infill percentage. This study shows that through adopting the developed model by considering the process parameters, parts of high quality (improved surface finish) with reduced build time could be produced by FDM technology. Optimum process parameters found to be build direction of 0°, raster width of 0.61 mm, layer thickness of 0.22 mm, infill percentage of 20%, and raster angle of 0°.

In this study, capabilities, performance, and limits of a new design field named topology optimization were investigated. Case studies under different loads and boundary conditions were evaluated. The case studies were selected by the purpose of illustration of the capabilities of topology optimization. In order to analyze the case studies with more complexity such as cantilever beam, both end fixed beam, dome shape under static and thermal loading, Optimization algorithms were used in the ANSYS software. Results showed reduced volume in final models are 66.29%, 52.88%, 50.054%, respectively. The mean value of stress in the Cantilever beam,both end beam and dome shape was increased 88, 800 and 6 Mpa, respectively. Also, the displacement level was increased 0.0001, 0.006 and 0.002 mm, respectively. In order to reveal the unexpected challenges and evaluation of optimized models, due to the presence of cavities in the body, Dome Shape model was selected and produced by additive manufacturing (FDM method). Results indicated that the output product has good dimensional accuracy and surface smoothness. By creating support structures that manually selected numbers and locations, 3D cavities were formed with good accuracy, indicate that there is a high potential for manufacturability of complex design parts without classical methods.

The purpose of this article is to remove one of the limitations of manufacturing and production of industrial specimens, which is employing a thermoset polymer-based composite as an alternative material in the construction of a motorcycle part (air manifold). It should be noted that the existing parts are produced using polyamide materials reinforced along with glass fibers. The mentioned limitation means that there are not enough order circulations to start production, and therefore there is no financial ability to make steel molds for plastic injection, which is not the case in thermoset composites, and relatively complex parts can be molded with silicone molds. As a result, in this article the types of thermoset polymers were investigated and considering the mechanical and thermal properties required to production this part, Novolac Epoxy-based Vinyl Ester resin was selected and to strengthen the resin, various reinforcing additives suitable for properties of the manifold were investigated, which resulted in the selection of 3mm glass fibers needle in a weight ratio of 30%. By fabricating the test samples of the mentioned composite and extracting the desired properties in the laboratory, the 3D model of the part was employed in Abaqus software and the composite properties were defined for the model. Then the operating conditions and manifold tests in Abaqus simulation and its results were evaluated. Finally, the air manifold was fabricated by the composite material and then analyzed experimentally. The test results showed that the selected composite will pass all the conditions.