The manufacturing of metal bellows with high ratios of crown-to-root diameters is very sensitive to design parameters such as internal pressure inside the tube, axial force and movement, die-stroke length (distance of the dies) as well as the initial tube length. In this paper, hydroforming process of a metallic bellows is investigated experimentally. For this purpose, the effects of internal pressure and die stroke on the maximum achievable convolution height and thickness distribution of hydroformed bellows is studied. The experiments are performed with different internal pressures such as 90, 110 and 130 bars and also in different die strokes such as 10, 12 and 14 mm. The results show that by increasing the die stroke, the range of allowable internal pressure to produce a metallic bellows without wrinkling or bursting decreases and manufacturing of the bellows becomes more difficult. It is extracted from results that with holding the die stroke value, very low internal pressures leads to wrinkling in the hydroformed bellows while very high internal pressures cause the excessive thinning. Also, it is concluded that by increasing both internal pressure and die stroke the convolution height of manufactured bellows is increased. It is proved that the maximum thickness reduction is occurred at the crown point of hydroformed bellows. تفاصيل المقالة

In this work, laser bending of perforated sheets has been investigated numerically. Laser bending of perforated sheets is more complicated than non-perforated sheets due to their complex geometries. In this paper, laser bending of perforated sheets is studied numerically in the form of thermo-mechanical analysis with ABAQUS/IMPLICIT code. For this purpose, the effects of process and sheet parameters such as laser output power, laser scanning speed, laser beam diameter and the number of punches in the sheet are investigated on the bending angle of laser formed perforated sheet. The results show that the larger punch diameters lead to decrease in bending angle in the laser formed perforated sheets. Also, it is concluded that the bending angle of the perforated sheet is decreased with increasing laser scanning speed. In addition, bending angle is decreased with decreasing laser beam diameter. تفاصيل المقالة

Manufacturing of complicated industrial components is one of the main challenges for mechanical engineers in sheet metal forming processes. Incremental sheet metal forming (ISMF) is used widely for forming complicated shapes by a single rotating tool. This paper examines the experimental investigation of two-point incremental forming of a complicated specimen made of AA3105 aluminum alloy. The part shape consists of positive and negative cavities and the shape complexity limits the manufacturing process to two-point incremental forming process (TPIF). In addition, the effects of selected process parameters such as forming depth in each increment of process, tool rotational speed and various forming patterns on thickness distribution and thinning percentage of specimen are investigated. The forming pattern includes the sequence of forming the cavities (Internal/External pattern and External/Internal pattern). The main finding of the study can be expressed that the thinning ratio of manufactured specimen is increased with an increase in the forming depth in each increment of TPIF. Also, the higher rotational speed leads to a reduction in the thinning of the fabricated specimen. The results prove that the use of Internal/External forming pattern leads to reduction in the thinning of the manufactured specimen. تفاصيل المقالة

In this paper, dissimilar resistance spot welding of AISI 1075 eutectoid steel to AISI 201 stainless steel is investigated experimentally. For this purpose, the experiments are designed using response surface methodology and based on four-factor, five-level central composite design. The effects of process parameters such as welding current, welding time, cooling time and electrode force are investigated on the tensile-shear strength of resistance spot welds. The results show that tensile-shear strength of spot welds is increased with increase in the welding current and welding time. Also, it is concluded from results that with increasing the electrode force and cooling time, tensile-shear strength of welded joints is decreased. During tensile-shear tests, three failure modes are observed, namely interfacial, partial pullout and pullout modes. The analysis of variance for the tensile-shear strength indicates that the main effects of welding current, electrode force, welding time, cooling time, second- order effect of the welding current and cooling time, two level interactions of welding current with welding time, welding current with cooling time and electrode force with cooling time are significant model terms. The results of analysis of variance show that the presented model for tensile-shear strength of dissimilar resistance spot welds of AISI 1075 eutectoid steel to AISI 201 stainless steel can predict 95.00% of the experimental data and leave only 5.00% of the total variations as unexplained. تفاصيل المقالة