Gaussian specimens for VHCF tests: Analytical prediction of damping effects

Experimental tests investigating Very-High-Cycle Fatigue (VHCF) properties of materials are commonly performed with ultrasonic testing machines which allow for a significant reduction of testing time but induce a relevant temperature increment in specimens. In particular, due to the large volume of material (risk-volume) under test, Gaussian specimens, recently introduced for investigating size effects in VHCF, are extremely prone to heat dissipation and to the consequent temperature increment. They were originally designed by the Authors without considering the hysteretic damping and its effects on power dissipation: however, in order to evaluate the feasibility of ultrasonic fatigue tests with Gaussian specimens, hysteretic damping effects must be taken into account. The paper proposes an analytical model that permits to evaluate the effects of the hysteretic damping on the distribution of the power density and on the power dissipation in Gaussian specimens. The theoretical model is verified through Finite Element Models and experimentally validated.