نشریه مهندسی مکانیک مدرس
سال بیست و سوم شماره 6 (خرداد 1402)

Single point incremental forming (SPIF) is a cost-effective process with high flexibility and as a result, it is a suitable choice for low-batch production compared to traditional metal forming methods. In the present experimental research, the warm SPIF with ball nose tool was used in the forming of aluminum tailor welded blanks (TWB) that were joined together by the argon welding process. Aluminum sheets of 6061 and 5083 with an equal thickness of 1.5 mm were used as base metals and joined together using the butt welding method. In this research, the effect of four parameters of temperature, lubricant, step down, and feedrate were investigated on the formability and appearance of aluminum. The temperature range is between room temperature and 290 degrees Celsius, and three types of lubricants are used in the experimental tests. The Taguchi method was used for the design of the experiment. The results of the tests indicated that an increase in the temperature as the most effective parameter led to an increase in the formability of TWB by 79%. The lubrication, step down, and the feedrate was in the next ranks of effectiveness in the formability of aluminum TWB.

In the production of industrial parts, machining is one of the most important operations in the field of manufacturing parts. The production of an industrial part takes place in three stages: design, process planning and manufacturing, and in all these stages, the computer is used as a powerful tool. In computer-aided process planning, the stage of identifying machining features is a prerequisite and an introduction to the next steps. Extracting information and identifying features from computer-aided design information has been continuously improved due to the increasing complexity of parts, but the research to find an optimal solution is endless. Over the past few decades, several methods have been introduced and applied by researchers to extract and identify machining features from design file information. In all the previous methods, the number and type of features are extracted as independent variables in the machining features identification pattern and from the part design file data. In this research, the charectrestics required to identify the machining features are extracted from the pixel values of the machining feature image by the artificial intelligence system automatically. The artificial intelligence system produced to identify the machining features in this research is able to identify all the information required for machining, including the name, the coordinates of the location of the feature relative to the part, and the dimensions required for the machining, by viewing the image of a part, and the information of the features present in the image the input to the system in a table.

Fossil fuel reserves are running out and its use for energy production also affects the environment. Therefore, sustainable and clean energy sources must be produced to meet the needs. In this research, mixed fuels of methyl esters of rapeseed oil, soybean oil and palm oil were produced with diesel fuel. To achieve the advantages of palm oil biodiesel (high calorific value) and soybean and rapeseed oil biodiesel (low kinematic viscosity), different biodiesel mixtures (BS10, BS20, BR10, BR20, BP10, BP20, BRSP10 and BRSP20) were used to evaluate their effect on engine performance and greenhouse gas emissions at speeds of 1800 to 2700 rpm with a step of 300 rpm under full load conditions. The physical and chemical properties of all fuel mixtures were measured according to the ASTM D6751 standard. An air-cooled, 4-stroke, naturally aspirated single-cylinder diesel engine was used for different mixture testing. The experimental results showed that in all the combined fuels, the values of power and specific fuel consumption increase with increasing engine speed, while the torque decreases. Also, the number of pollutants increases with the increment of engine speed. Based on the results, BP20 mixture fuel can be used as an alternative in diesel engines without any engine modification.

Surface quality and roughness are major effective parameters on the function of optic components. This study developed a new design of the Ball-End Magnetorheological finishing tool with the ability to mount on a three-axis CNC milling. In the new design, a new concept of the cooling system was used for cooling the internal and external surfaces of the electromagnetic coil, and optimizations on magnetic flux distribution were performed. With the aid of magnetostatic simulation in Ansys Maxwell software, the tool’s capability for producing magnetic flux density was tested. The capability of a new tool for polishing non-ferromagnetic BK7 glass was tested by selecting optimized process parameters like working gap and magnetizing current. An experimental magnetic flux density test with the gauss meter showed that the newly designed BEMRF tool can generate enough magnetic flux density for polishing BK7 glass. The finishing test showed the tool’s ability to create enough indentation force on the workpiece’s surface and reduce surface roughness.

Considering the increasing use of high-speed presses, such as high-speed servo presses, in the automotive industry, it seems necessary to investigate the formability of sheet metals in this range of forming speed. Therefore, this study has been conducted to investigate the effect of medium strain rate forming on the formability of the St14 steel sheet. Tensile tests were done at various strain rates, and formability tests were performed to create forming limit curves at the quasi-static and impact forming. Finite element simulation was used to extract the numerical forming limit curves. The material model was entered into the simulation by considering the strain rate effect using the VUHARD subroutine. The results of tensile tests showed that some influential strain-hardening indicators reduce with strain rate enhancement. Also, using the material model, the tensile behavior was predicted with good accuracy at each strain rate. In impact forming, fracture and strain concentration was transferred to the dome center, and the dome height in biaxial stretching was reduced by 17.1% compared to quasi-static forming due to the variation of frictional conditions. The forming limit curve of impact forming was shifted to the lower values and right side of the forming limit diagram compared to quasi-static forming. In impact forming, the forming limit in plane-strain condition was reduced by 8.1% compared to quasi-static forming. Also, the simulation results, including fracture position, forming limit curve, and dome height in both forming processes, were in good agreement with the experimental results.

The type and material of the core piece of sandwich panels are important parameters in the mechanical behavior of these sandwich samples. In this study, the mechanical behavior of sandwich panels with two types of aluminum alloy foam core was investigated. Also, the effect of the method used to stabilize aluminum foam investigates and compares during the bending and compressive tests, for this purpose, the properties of the core of sandwich panels made with LM13 alloy aluminum foam were fabricated with calcium stabilizer and silicon carbide powder separately. The results of the X-ray diffraction test showed the presence of Al4Ca intermetallic compounds in aluminum foams containing calcium metal, and silicon carbide particles for aluminum foams containing silicon carbide powder in the cell wall. The yield strength of sandwich panels with aluminum foam core and calcium metal stabilizer was higher than that of cores with silicon carbide particle stabilizer. Also, sandwich panels with aluminum foam cores containing silicon carbide powder showed more energy absorption. In contrast, foams with silicon carbide powder stabilizer absorbed more energy under the uniaxial pressure test. Also, the results of the macrostructure analysis of how the shape of the sandwich panel changed in the three-point bending test were indicative of a reduction in force due to the weakness in the connection between the sandwich panel shell and the aluminum foam core.