Temperature dependence of third order elastic constants
Second and third order elastic constants are needed to describe the influence of stress or strain states on the ultrasonic velocities. In order to apply ultrasonic techniques for the evaluation of stress states, the particular values and their changes with the temperature of the component under test has to be known. Second and third order elastic constants are also needed to describe the thermoplastic behavior of a solid. It has been found that the temperature dependence of ultrasonic velocities is influenced by the strain state of the material. Based on that effect, an additional technique for the ultrasonic evaluation of stress states can be developed. In both cases, the influence of temperature on the elastic constants must be known. Temperature dependences of the second order elastic constants lambda and my or Young's and shear modulus, respectively, are fairly well investigated. This study concentrates on the evaluation of the temperature dependence of the third order elastic cons tants of different aluminum and steel alloys. It has been found that the third order elastic constants increase in value with increasing temperature, and that the temperature dependence on one of the third order elastic constants is significantly smaller than on the other two third order elastic constants.