Ali Reza Nikravan, Farhad kolahan,
Volume 15, Issue 9 (11-2015)
Abstract
The use of TI-6AL-4V alloy is increasing in various industries, due to its characteristics such as high strength to weight ratio and excellent creep and corrosion resistance. However, because of titanium alloys poor machinability, non-traditional machining is usually used in shaping them. In this research, the wire cut machining of Ti-6Al-4V alloy has been investigated. In this regard, the effects of 8 process parameters and their optimal values are determined, for two process characteristics, cutting rate and surface roughness. One of the innovative aspects of the current study is the consideration of cutting height as one of the main parameters affecting the process output quality. Therefore, for three different cutting heights (each with two replicates), the L18 Taguchi matrix is employed to gather the required experimental data. Then, using the 108 data, statistical analysis, including signal to noise and analysis of variance were carried out in order to determine optimal process parameters and their effects on the two process outputs. Optimal process parameters values for maximum cutting rate and minimum surface roughness were verified by validation experiments. The results illustrate that the cutting height would alter the effects of process parameters and their optimal values. Finally, multi-objective optimization was performed to determine optimal parameters settings based on relative importance of process outputs for cutting heights of 30, 60 and 90 mm, in the form of technology table. The contribution of uncontrolled parameters and errors were less than 10% in all cases, which indicate the accuracy of the proposed technique.
A. Torabi, F. kolahan,
Volume 19, Issue 8 (August 2019)
Abstract
Pulsed laser welding have a wide application in welding of thin sheet because of high intensity of its localized heat source. In the current study, 3 experimental tests with low, medium, and large level of energy and also, the 3D finite element simulation of Nd:YAG pulsed laser welding in thin sheet AISI316L have been done. Thermal analyzes were done with ABAQUS software in transient heat transfer. In order to increase the accuracy of thermal model, heat losses were considered as convection, radiation, and thermal conduction. 3 thermal models with different heat flux distribution as Gaussian surface, Gaussian volume, and conical volume were used. The main aim of this study is the selection of best thermal model between 3 mentioned thermal models to estimate the melt pool geometry with high accuracy. In addition, with defining and applying the shape factor in 3 thermal models, the finite element analyses were carried out in order to enhance the precision of estimated melt pool geometry. After thermal analysis, the melt pool geometry dimensions are extracted for each of the mentioned thermal models and compared with experimental results. Results show that thermal analysis with Gaussian surface model have the melt pool geometry accurately just in welding with low energy. Also, the conical model could estimate the melt pool geometry in all levels of energy with acceptable accuracy. Therefore, the pyramidal thermal model can be selected as the most suitable model for simulating pulsed laser welding in thin steel sheets.
Ali Reza Nikravan, Farhad kolahan, Mahmoud Shariati,
Volume 22, Issue 8 (August 2022)
Abstract
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.
