Fatigue properties of wood at different load ratios tested at 50 Hz and 20 kHz

Abstract

AbstractFatigue properties of sycamore maple (Acer pseudoplatanus) under cyclic tension, cyclic compression and tension‐compression loading at 50 Hz are investigated. Furthermore, for the first time, fatigue test results of wood generated with the ultrasonic fatigue testing technique at 20 kHz under tension‐compression loading are presented. Cyclic properties are in line with the static properties – with the tensile strength being more than two times the compressive strength. Mean lifetimes of 106 cycles are found if the maximum tensile stress for cyclic tension is 69 %±8 % of the tensile strength and if the maximum compressive stresses for cyclic compression and tension‐compression are 75 %±7 % and 54 %±4 % of the compressive strength, respectively. Tension‐compression loading at 20 kHz delivers lifetimes comparable to servo‐hydraulic tests at 50 Hz, and no pronounced frequency effect on fatigue lifetime is found. Ultrasonic fatigue testing is therefore, in principle, appropriate for accelerated fatigue testing of wood up to the very high cycle fatigue regime. Tests up to 109 cycles show no evidence of a fatigue limit for sycamore maple.