Papers by Author: E. Bazrafshan

Abstract: Welding-titanium and titanium alloys must be performed with special precautions because these materials are very reactive to contamination from atmosphere gases. One of the important technological considerations in welding titanium and its alloys is protection of the molten weld pool and HAZ from atmospheric gases such as nitrogen, oxygen, carbon dioxide and moisture and contamination. Absorption of the atmospheric gases affects the mechanical and metallurgical properties and may cause embrittlement, lake of fatigue strength and hydrogen cracking of titanium welds. In this paper, the effect of welding atmosphere moisture on hydrogen absorption and distribution in Ti-6Al-4V, pure titanium and TI-15V-3CR-3SN-3AL TIG welds has been studied. The experimental results indicated that hydrogen distribution which was symmetrical with respect to the weld axis had maximum and minimum points. It was also observed that heat treating the joints after welding resulted in reduction of the magnitude of the maximum and minimum points as well as redistributed the hydrogen in the welds in such a way that the distance of the maximum and minimum points got farther from the weld axis. This distribution is affected by type of titanium alloy and degree of annealing .in this investigation we used vacuum welding chamber with TIG welding apparatus and a special metal sampling and composition detecting systems for joining the samples and detecting the amount of hydrogen in the weld metal .the aim of this investigation was to increase the level of our knowledge about harmful effect of diffusion the hydrogen in the different titanium alloys. Introduction

Abstract: Underwater explosion is a complex discussion because it has two phase environment including shock waves, bubble effects, cavitation, high strain rate, geometric and material non linearity. Results of underwater explosion tests on the circular steel plates have been discussd. Test results compared with numerical analysis results which it is done by LS-DYNA code. LS-DYNA is the software which is used to analyze large dynamic deflections by use of explicit method. We found that this code has good accuracy to predict the maximum deflections. Strain rate effects included in the program by use of Cowper-Symonds relation.