Papers by Author: Mohammad Mastoori

Abstract: Flow forming is one of the cold forming process which is used for hollow symmetrical shapes. In this paper, the forward flow forming process is simulated using the finite element method and its results are compared with the experimental process. The variation of thickness of the sample is examined by the ultrasonic tests for the five locations of the tubes. To simulate the process, the ABAQUS explicit is used. The effects of flow forming variables such as the angle of rollers and rate of feeding of rollers, on the external variables such as internal diameter, thickness of tube and roller forces are considered. The study showed that the roller force and surface defects were reduced with low feeding rate and low rollers attack angles. Moreover, the sample internal diameter increased at low feeding rate and low rollers attack angles. The optimum variables for flow forming process were also obtained.

Abstract: Laser welding of AISI 304 stainless steel was carried out by pulsed Nd:YAG laser machine under different welding conditions. Geometrical shape of the joints was circular butt. Studies were focused on laser power, welding velocity, beam diameter and pulse duration. Microstructure of welded joints was investigated by optical microscopy (OM) and scanning electron microscopy (SEM). OM and SEM results show no evidence of grain growth in heat affected zone (HAZ). In addition, columnar and equiaxed grains are observed in the weld metal. Various defects such as lack of fusion, underfill, porosity, hot crack and mismatch are observed as a result of improper welding conditions. The best welding conditions to obtain minimum defects are presented.