Fatigue Testing of Microspecimens from a Weldment

This paper describes a technique for measuring the strain-controlled cyclic stress-strain behavior of microspecimens taken from a steel weldment. The specimens have a cross-section 0.3 by 0.3 mm with a gage section approximately 1.4-mm long and are believed to be the smallest specimens that have ever been tested in fully-reversed axially-loaded fatigue tests. The microsample fatigue test system developed allows both strain and stress control. The key feature is the ability to measure strain directly using a laser-based strain gage that measures the relative displacement between two tiny reflective indentations in the specimen surface.