APPLICATION OF ULTRASONIC FREQUENCIES IN FATIGUE

Using ultrasonic frequencies offers a possibility to investigate the f atigue properties of materials in a very economic way. High cycle fati gue tests of the die-cast magnesium alloy AZ91 hp were performed. The endurance limit of this material is affected by the maximum size of ca st voids and may be predicted on the basis of LEFM-principles. Near th reshold constant amplitude and random amplitude fatigue crack growth m easurements of metastable austenitic-ferritic steel are presented and interpreted on the basis of crack closure effects.