Related Experiment Video
Updated: Nov 17, 2025

Full-field Strain Measurements for Microstructurally Small Fatigue Crack Propagation Using Digital Image Correlation Method
Published on: January 16, 2019
Effect of Specimen Thickness and Stress Intensity Factor Range on Plasticity-Induced Fatigue Crack Closure in
Kenichi Masuda1, Sotomi Ishihara1,2, Noriyasu Oguma1
1Department of Mechanical Engineering, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan.
Abstract:
Fatigue crack growth experiments are performed using A7075-T6 compact tension (CT) specimens with various thicknesses t (1-21 mm). The stress intensity factor at the crack opening level Kop is measured, and the effects of t and the stress intensity factor range ΔK on Kop are investigated. In addition, the change in Kop value due to specimen surface removal is investigated. Furthermore, we clarify that the radius of curvature of the leading edge of the fatigue crack decreases as t becomes thinner. Using the three-dimensional elastoplastic finite element method, the amount of plastic lateral contraction (depression depth d) at the crack tip after fatigue loading is calculated quantitatively. The following main experimental results are obtained: In the region where ΔK is 5 MPam1/2 or higher, the rate of fatigue crack growth da/dN at a constant ΔK value increases as t increases from 1 to 11 mm. The da/dN between t = 11 and 21 mm is the same. Meanwhile, in the region where ΔK is less than 5 MPam1/2, the effect of t on da/dN is not observed. The effects of t and ΔK on the da/dN-ΔK relationship are considered physically and quantitatively based on d.
Related Concept Videos
Fatigue
Plastic Behavior
Stress-Strain Diagram - Ductile Materials
Stress Concentrations
Stress Concentrations
The stress...
Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity

