regression modeling

Due to the importance of the weld quality in pressurized equipment, this research investigates the application of Nd:YAG pulse laser in welding of thin-walled AISI316L steel pipes. The input parameters include current intensity, pulse width, frequency, rotational speed, and compressive force applied to the seam of the two tubes being welded. Depth of weld penetration and the weld depth-to-width ratio (aspect ratio) were selected as two output characteristics. The relationship between input and output parameters was obtained by fitting regration functions on the data of central composite design (CCD) of experiments. According to the analysis of variance, the influence of the ratio of compressive force applied to the weld seam to the aspect ratio is 2.5%, and total influence of pulse width and the current on each of the two outputs is 84%. Completion of the depth of penetration and increasing of the weld aspect ratio are two main findings of the optimization process. In the end, to improve the joint quality, based on the optimal level of the parameters, samples were laser-welded in a chamber filled with argon. With this regard, aspect ratio, tensile strength, and failure strain at the samples manufactured by optimum parameters in argon chamber, were improved by 14%, 7%, and 37% compared to samples in normal condition (protection of the molten pool with an argon nozzle), respectively.

Due to the importance of the joints in the pressurized instruments and the abilities of the laser welding in this study, the welding of AISI316L tubes have been studied and analyzed. In this regard a fixture has been drawn in order to positioning of the tubes and fixed on the welding desk. The welding input parameters includes the laser welding adjusting variables, includes (welding current, welding pulse width, and welding frequency). Moreover, the effect of the two other variables (rotating speed and the force applied to the welding seam) has also been studied. The welding output characteristics comprises the welding width, depth of penetration and welding strength. The experimental data has been collected using L27 Taguchi design. The relation between the process input variables and output characteristics has been established using different regression models. Based on the analysis of variance (ANOVA) results, pulse width and welding current with 70% contribution have an influential effect on all the three response characteristics. Moreover, the seam force has only the influential effect on the depth of penetration and strength. Next, in optimization step based on the importance of the process characteristics (strength, depth of penetration, welding width), the optimized levels have been determined. At the end, the optimized condition has been conducted using laser welding, in comparison of which the samples in the design matrix, the welding depth has a close relation with the thickness of the wall, the welding boundaries smother and the strength has a close value to the base metal.

Electrical discharge machining process، is one of the most widely used methods for machining، the electrically conductive parts. In this way the tool is not in contact with the workpiece and the hardness of workpiece does not affect the machining speed. In Electrical Discharge Machining process، selection of the correct machining parameters are effective in final cost and the quality of the products. The special application of this alloy in various industries including tooling industry is attributed to its high hardness and wear resistance. The DIN 1. 2080 steel at low temperature has a high wear resistance. Its hardness depth is high and it is suitable for machining at low temperature. In this paper، the effect of the type and setting parameters and determination of optimal levels in of electrical discharge machining of alloy DIN 1. 2080 using the Taguchi method and optimal determinant is examined The desired setting parameters including gap voltage، current intensity، on time and off time. The material removal rate and surface roughness of produced parts as the output characteristic of the study were investigated. Results showed that the spark current is more effective on the output parameter (more than 65% on material removal rate and more than 48% on a surface roughness)، Other effective parameters are pulse on time، pulse off time and voltage changes، respectively. Higher current and pulse on time values and lower voltage and pulse off time values result in high MRR and low SR.