A Simple Test Method and Apparatus for Biaxial Fatigue and Crack Growth Studies

Abstract

A simple method and unique test apparatus are presented for conducting fatigue and fatigue crack growth studies using plate-type specimens under biaxial bending. The test method and apparatus design make use of the concept of anticlastic bending of a plate with a rhombic configuration. The simplicity and uniqueness of the test apparatus are that with one constant load amplitude, a wide variety of stress or strain biaxial ratios can be attained by varying only the lengths of the rhombic plate diagonals. The test apparatus and rhombic plate specimens have been used for low cycle fatigue, cumulative fatigue damage, and mixed-mode fatigue crack growth studies of engineering materials under biaxial bending. Some results from these previous research studies will be discussed in this present paper to illustrate the utility of the test method and apparatus.