FATIGUE TESTING OF MICROSPECIMENS FROM A WELDMENT

This paper describes a technique for measuring the strain-controlled c yclic stress-strain behavior of microspecimens taken from a steel weld ment. The specimens have a cross-section 0.3 by 0.3 mm with a gage sec tion approximately 1.4-mm long and are believed to be the smallest spe cimens that have ever been tested in fully-reversed axially-loaded fat igue tests. The microsample fatigue test system developed allows both strain and stress control. The key feature is the ability to measure s train directly using a laser-based strain gage that measures the relat ive displacement between two tiny reflective indentations in the speci men surface.