Geometric optimization of ultrasonic fatigue test specimens based on Thermo-elastic behavior

Nowday, due advancement of technology, the number of oscillations applied to some parts reaches range of 107 and higher. Recently, researchers have used ultrasonic fatigue test to study the fatigue behavior in these parts. This device is considered because of the high frequency of loading and as a result, achieving a higher number of oscillations in a shorter time. There is no universally accepted standard for this test, so one of the most commonly used geometries in this test is the hourglass. while examining this geometry in order to achieve optimal geometry or maximum stress, the effect of geometric parameters on temperature increase during high frequency vibration or the thermal elasticity effect which is known as one of the disadvantages of ultrasonic fatigue test. has been studied to minimize this effect. For this purpose, the dimensions of the hourglass geometry were defined as a parameter and its changes were investigated using simulations.The results show that by decreasing radius of curvature along with constant diameter of middle part and diameter of cylindrical part, the amount of stress increases and also the amount of temperature changes decreases increasing diameter of the cylindrical part while middle diameter and amount of curvature is constant increases the amount of stress and temperature. The above results were evaluated using experimental arrangement and good agreement was observed in them.