Design and development of an ultrasonic fatigue testing machine for very high cycle fatigue 2020-01-0183
There has been growing demand for increased fuel efficiency, reduced emissions and improved power performance while maintaining reliability and durability of mechanical and structural systems in many different industries. The structural components often experience long loading histories, typically ten million cycles or greater, i.e. high cycle fatigue (HCF) and very high cycle fatigue (VHCF) regimes. HCF in the range of 10^6-10^8 cycles and VHCF in the range of 10^8-10^10 cycles are key design criteria for aerospace, automotive, military, transportation and other industries. However, fatigue characterization of metal alloys in the HCF and VHCF regimes is hindered by traditional fatigue testing machines due to time and cost constraints. The development of high power piezoceramic actuators enables efficient and reliable fatigue tests in the HCF and VHCF regimes within a very short time frame on the basis of the ultrasonic fatigue testing approach.
A fully instrumented ultrasonic fatigue test machine operating at 20 kHz was designed and built to investigate HCF and VHCF behavior of four different aluminum alloys. The fatigue testing machine went through several stages of design and development. Finite element modeling was employed to design and optimize three versions of an acoustical horn, a single half wavelength booster and three different geometries of test samples. Test samples consisted of extruded Al2024-T351 and Al7075-T6 alloys as well as additive manufactured AlSi10Mg and AlSi7Mg produced by direct metal laser sintering. Fatigue tests in the VHCF regime were successfully conducted and fatigue data was found in very good agreement as compared with experimental data in the literature.
Paul Catalin Ilie, Xavier Lesperance, Ayhan Ince