Variable Amplitude Testing of 2024-T351 Aluminum Alloy Using Ultrasonic and Servo-hydraulic Fatigue Testing Equipment

Ultrasonic fatigue testing allows time saving investigations up to the very high cycle fatigue regime. The high frequency and adapted testing method may influence measured fatigue properties. Servo-hydraulic and ultrasonic test data of 2024-T351 aluminum alloy show comparable lifetimes for constant amplitude tests at load ratio R=0.1 and R=0.5. In ultrasonic variable amplitude (VA) tests, amplitude is varied over successive pulses (“block loading”) rather than cycles (“single-cycle loading”). Lifetimes agree for servo-hydraulic and ultrasonic VA block-loading tests at R=0.1. Considerably lower lifetimes measured in servo-hydraulic single-cycle tests suggest a pronounced influences of the loading sequence on VA fatigue damage.