Crack closure effect of fatigue crack under cyclic tensile loading

Abstract

The objective of this study is to evaluate crack growth behavior under cyclic tensile loading considering crack closure effect. Crack growth behavior under cyclic tensile loading on a plate with surface crack is tested. Material is 2017 aluminum alloy. Crack growth process is studied by experiment and simulation. Crack growth behavior is analyzed by S-version FEM. In order to predict crack growth behavior in detail, crack closure effect is taken into account. Crack closure effect along surface crack tip under cyclic tensile loading is analyzed by ANSYS. In order to consider crack closure effect, an effective stress range ratio is introduced. An effective stress range ratio is defined by load range during crack opening over load amplitude. It is found that an effective stress range ratio is small near the surface of the specimen. This means crack growth rate is small near the surface of the specimen. Effective stress intensity factor range is calculated by effective stress range ratio. Using this effective stress intensity factor range, crack growth simulation with crack closure effect is performed by S-FEM. Crack shape and number of cycles of the simulation which considering crack closure effect comes close to experiment. And even if the thickness of the specimen is different, the influence of crack closure effect hardly varies.

Keywords

• tensile cyclic loading
• fatigue crack
• surface crack
• through crack
• s-fem
• crack closure effect