Experimental and theatrical evaluation of the Effect of Grain size of St52 on Acoustic Softening

The main purpose of this paper is to reveal the volume effect of ultrasonic vibrations on the plastic behavior of S355J2 steel specimens with different grain sizes and investigate the decrease in the Yield strength and ultimate strength of these steel specimens. For this study, samples of grain size of 10, 35 and 60 microns were created by performing various cycles of normalization and annealing heat treatments. An experimental setup was designed and developed for the tensile test with ultrasonic vibration. The tensile test was carried out at a room temperature and constant speed of 1 mm /min and it was found that by applying 390 watts of vibrations, the yield strength reduction of steel specimens with a grain size of 10, 35 and 60 microns was 8%, 18% and 27%, respectively. . The grain boundary length in fine-grain specimens is greater than the largest-grain specimens, therefore, the sound energy is distributed over the boundary. Therefore, the effect of applying ultrasonic vibrations on fine-grain specimens is less than that of largest grains and the yield strength and ultimate strength of fine-grain specimens showed a lower reduction