Unified Theory and Experimentation for Fatigue and Fracture of High Temperature Shape Memory Alloys
Abstract
Shape Memory Alloys (SMAs) are desirable for actuation, energy absorption, and vibration damping in the aerospace, oil&gas, and medical industries. Affordable nano-precipitation hardened High-Temperature SMA (HTSMA) solid-state actuators, in particular, are an attractive alternative to electromagnetic actuators as they display stable cyclic actuation response at temperatures up to 500C, power densities an order of magnitude higher than conventional actuator systems, with the preliminary fatigue life data on the order of tens of thousands of cycles under high stress levels. Lack of appropriate test methods, mechanics theories, and numerical approaches for the cyclic damage tolerance and life prediction of SMAs is a major obstacle for the wider acceptance of these materials in applications. Our preliminary results point to: 1) the deficiencies in the classical fracture and cyclic crack growth theories in describing the behavior of these materials showing global reversible martensitic transformation; 2) discrepancies between theory, testing standards,and experimental results in determining fatigue and fracture related material properties; and 3) the dominant influence of microstructure in the early stages of crack formation and growth, and its significant contribution to the statistical variability in actuation fatigue lives.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 11, 2018
- Source ID
- FA95501810276
Entities
People
- Ibrahim Karaman
Organizations
- Air Force Office of Scientific Research
- Texas Engineering Experiment Station
- United States Air Force