Novel System for Miniature and Micro Specimen Fatigue and Fracture Testing

摘要

A microspecimen testing system has been developed to conduct real-time fatigueand fracture measurement on specimens less than 1 mm thick. Principal components include an interferometric-based crack opening displacement (COD) gage, a piezoelectric actuator, a resistive load cell, and an integrally machined testing cell and loading fixtures. Software has been developed to rapidly analyze interference signals and provide close-loop cyclic control. The principal system limitation is that the maximum real-time cyclic testing frequency is only 1/4 Hz for the relatively large specimens tested. System measurement resolution based on the load, COD, and load-line displacement is adequate for B = 1 mm SE(B) specimens, and illustrates the capability to test much smaller specimens. Initial system testing has indicated the following: the effects of planar rigid body motion have been simply discriminated from actual COD, compliance estimates based on these COD readings are accurate for a/W= 0.5, and system stability appears to be reasonable.