Abstract- Low frequencies vibration is known as a method for stress relieving of metals. This paper shows that the high frequency vibration (ultrasonic) is also a promising method for stress relieving. In this paper the effect of parameters including stress relieving time, vibration amplitude, grain size and pre-load on samples are investigated. In order to evaluate the residual stress before and after ultrasonic relieving process Almen test was used. The samples were made according to Almen standard and after heat treatment, were shot peened so that, the compressive and tensional residual stress induced into the samples, then the stress relieved by means of ultrasonic vibration. Results show that the residual stress has decreased about 46 percent for coarse grain samples and 27 percent for fine grain samples. Also it was found that the most effective factor on the stress relieving rate is the grain size and the pre-load has the least effect.

Keywords: Stress relieving, Ultrasonic, Grain size, ultrasonic amplitude

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