Metal Fatigue and Fracture Testing and Analysis

Fatigue and fracture testing was performed on four engineering materials, utilizing compression pre-cracking techniques for large crack growth and a newly developed Single Edge Notched Bend specimen for small, naturally initiated cracks. Fatigue crack growth simulation results have shown that both low-cycle and high-cycle fatigue can be modeled accurately as fatigue crack growth. Testing has also shown that the starting fatigue crack growth rate of any load-shedding test has significant influence on load history effects, with lower starting rates yielding lower crack growth thresholds and faster rates. Through inspection of fatigue surfaces, it has been shown that beveling of pin-holes in the crack growth specimens may be necessary to ensure symmetric crack fronts and that the presence of debris along the fatigue surfaces can cause considerable crack growth retardation.