Development of a Microcircuit Grid Technique for Automated Crack Length Measurement for Fatigue Testing at Elevated Temperature

摘要

A microcircuit grid technique was investigated and used to measure crack lengths in fatigue crack growth test specimens of an aluminum alloy (7075-T6) at room temperature and a nickel-based superalloy (Inconel 718) at 650 C as part of a Phase I SBIR program supported by the Air Force. Crack lengths were determined from stepwise changes in the resistance of microcircuit grids deposited on compact tension specimens by a photolithography process. Crack lengths assessed from discrete voltage changes recorded for a grid on a bridge circuit agreed closely with direct optical measurements. The fatigue crack growth data obtained from both alloys were in agreement with the data in the literature. Keywords: Microcircuit grids, Automated fatigue testing, High temperature test capability, Spectrum loading. (jes)