جستجوی مقالات مرتبط با کلیدواژه « TIG Welding » در نشریات گروه « مکانیک »

the one-of-a-kind properties of series 7xxx aluminum alloys such as high strength, relatively low density, good formability, and good resistance to stress corrosion cracking have made this class of materials a good choice for aerospace, automobile, and marine industries. Watertight, low weight, and fast procedure are the reason why welding is used in many industries. The heat that welding produce causes many problems like softening in the heat-affected zone. In this research with the use of a 3-D finite element model, the heat transfer of the Al-7075-T6 is investigated and verified by comparing them with the experimental model and the reduction of hardness in the heat-affected zone of the aluminum was predicted with good precision. In the next step, the softening of HAZ due to welding was measured with microhardness. With the use of the FEM model kinetic of over-aging was measured. The results show hardness of the alloy has two sources i.e. age-hardening and work-hardening. It seems welding eliminates the effects of age-hardening but has no effect on the hardness that comes from work hardening. Also, the decrease in the hardness of the solution-annealed area can be recovered through proper heat treatment. However, it is unrecoverable in the over-aged area.

One of the fastest ways to repair a damaged airfield, is using the matting plates. These plates are manufactured with various size and materials. If there is no way to continuously manufacture the plates, one can produce two separately parts of them and weld to each other. In this paper, the strength of a matting plate namely AM-2 welded by TIG welding process has been analyzed. For determination of the landing loads, Hercules C-130 aircraft has been considered. Various values of subgrade CBR have been studied. The joining plan of plates has been considered in such a way that the strength in the weld region be greater than before. The results showed that by using the matting plate welded by TIG welding process, the value of the subgrade CBR should be at least 15. Simulating test with crane has been carried out in this paper and good agreement was found in the results obtained by experimental tests and that evaluated by numerical analyses.

In this research, metallurgical and mechanical properties of TIG welded parts were investigated. For this purpose, TIG welding operation with optimum input parameters was carried out on XH50 and Hastelloy x rolled sheets. For comparison these two materials and feasibility of material replacement, initially elemental analysis of the two materials was accomplished and then the properties such as microstructure, tensile strength and micro-hardness were examined for both initial and welded specimens. The results show that heat affected zone in Hastelloy x welded samples is wider than XH50 welded samples and Heat affected zone in Hastelloy x welded samples consists of three regions. Despite the same tensile properties of the two materials, micro-hardness of the initial material and also tensile strength and micro-hardness of the welded specimen for Hastelloy x were significantly higher than XH50. The average of tensile strength for Hastelloy x welded samples is approximately 31% higher than that for XH50 welded samples due to formation brittle phases in XH50 samples. Therefor Hastelloy x is more desirable than XH50 for TIG welded parts.

Residual stresses and distortion are of the main disadvantages of welding process which determining the amount and distribution of them have great importance in the design of structures, especially in the space industry. In this study, a finite element method is used to analyze the thermo- mechanical behavior of a spherical shell due to TIG welding. The spherical shell is made of titanium alloy (Ti-6Al-4V) with 2 mm thickness. The modeling of welding process is based on an uncoupled thermo- mechanical coupling. TIG welding is examined for six cases based on current intensity and welding progress speed setting the voltage on 12 V in all cases. Distribution of temperature and residual stresses caused by TIG welding of the titanium spherical shell have been extracted and compared among the six different cases. The effects of current intensity and welding progress speed on shell distortion and residual stress have been investigated. The results showed that increasing the current intensity and decreasing the welding progress speed have the most effects on longitudinal residual stresses which the amount of this increasing reached to %44 for decreasing the welding progress speed. Welding distortion increases to maximum %132 by increasing current and decreasing welding progress speed.

Hybrid laser-arc welding is a new welding process which received particular attention in various industries because of its technological and economic advantages. This process combines a laser beam and an electric arc to incorporate the advantages of both laser and arc welding processes. The main goal of this paper is to evaluate the performance and ability of hybrid Nd:YAG laser-TIG welding compared to lone laser welding process for welding of aluminum foam sandwich (AFS) panels of AA6082. For this aim, a set of experiments for both laser and hybrid laser-TIG welding were done to investigate the effects of welding parameters including laser power, arc current and welding speed on weld dimensions. Then, appropriate welding parameters for the laser and hybrid laser-TIG welding of AFS panels were calculated by statistical analysis. The results show that laser power threshold for creating the keyhole was less in hybrid laser-TIG welding than lone laser welding. Moreover, increasing the laser power and decreasing the welding speed result in increasing both the weld depth and width. But, with increasing the arc current, the weld depth remains almost unchanged and only the weld width increases. Comparing the laser and hybrid laser-TIG results show that adding a 100 A arc to a 2000 W laser source can increase the welding speed from 2 to 3 m/min which prove the high ability and efficiency of hybrid laser-TIG welding process.