Automatic Crack Length Measurements by the Electrical Potential Drop Method with Computer Control

摘要

A method for automatic crack length measurements in fatigue crack propagation tests is described. Using a constant electric current through the specimen, the electric potential drop near the crack and a reference potential drop on the same specimen away from this circle are measured. The ratio of the two potential drops is used for calculating the crack length. This is done by the same computer that controls the fatigue load, which allows fatigue load readjustments dictated by crack length. As a result of the automatic crack length measurements, tests can run overnight without attendance of personnel.