In this study, multi-objective optimization of mechanical properties in friction-stir-welding of AH12 1050 aluminum alloy is performed using a combination of the response surface method and multi-objective particle swarm optimization algorithm. The process parameters are considered as tool pin diameter, shoulder diameter, rotational speed, feed speed, and tool tilt angle. The heat-affected zone’s yield strength, fracture strain, impact toughness, and hardness on the advancing and retreating sides are selected as the objective functions. Threaded and simple conical pins are utilized to evaluate the effect of the pin geometry on the specimen mechanical properties. Optimization model outputs are in agree with the obtained experimental results. The effects of process parameters on the mechanical properties of the friction-stir-welded sheets are studied. Results reveal that the lower rotational speed and higher feed speed improve the material strength and hardness. Moreover, the microstructural analysis demonstrates that the proposed methodology can achieve a fine-grained structure with the minimum defects. Improvement in the material flow is observed for the threaded cylindrical pin compared with the conical pin due to the geometric shape of the tool pin leading to more functional mechanical properties. It is found that the combination of the response surface methodology and the multi-objective particle swarm algorithm led to the modeling and optimization of the process with outstanding accuracy and low experimental cost.
Tube Hydroforming Process (THF) is heavily affected by the pressure-displacement diagram, and adjustment of the raw tube. Three common defects of the process are bursting, buckling and wrinkling. In this work, the leading conditions to wrinkling defect have been studied. Proper criteria are required to predict wrinkling condition, and to quantify wrinkling when subjected to various pressure-displacement diagrams. A variety of criteria have been presented by researchers, most of which are suitable to a specific geometry. In current work, two criteria are considered namely, the strain difference and the radius velocity. At first an accurate FEM (Finite Element Model) model of the process have been established and validated. Then based on a number of experiments with different diagram, the process have been simulated and analyzed. According to experiments imbalances between pressure and displacement, improper sitting of tube in the die, poor vacation of the tube and the existence of external tiny particle inside the die, are the reason of wrinkling criterion in the tube. The Response Surface Method (RSM) has been used to model the responses from the finite element analysis. The behavior of the process has been predicted using this model.
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