Fatigue and Fracture of Small Structures

Abstract

This thesis presents the results of experimental and theoretical studies of important failure modes in small metallic structures. These include failure due to monotonic and cyclic loading, and cohesive and adhesive failure of small structures. First, a novel micro-beam technique is used to study short crack growth in stainless steel. Micro-testing techniques and fracture mechanics models are then used to elucidate the mechanisms for fatigue crack initiation or "pop in" in LIGA Ni MEMS thin films. Finally, a new micro-scale push-out test technique is developed and applied to the measurement of the adhesive and cohesive strengths of drug eluting stent (DES) structures. The degradation of the DES is then investigated under conditions that simulate physiological environments. The implications of the results are discussed for the robust structures with micro-scale dimensions.