| Summary: | Fatigue crack growth experiments are performed using A7075-T6 compact tension (CT) specimens with various thicknesses <i>t</i> (1-21 mm). The stress intensity factor at the crack opening level K<sub>op</sub> is measured, and the effects of <i>t</i> and the stress intensity factor range ΔK on K<sub>op</sub> are investigated. In addition, the change in K<sub>op</sub> 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 <i>t</i> becomes thinner. Using the three-dimensional elastoplastic finite element method, the amount of plastic lateral contraction (depression depth <i>d</i>) at the crack tip after fatigue loading is calculated quantitatively. The following main experimental results are obtained: In the region where ΔK is 5 MPam<sup>1/2</sup> or higher, the rate of fatigue crack growth da/dN at a constant ΔK value increases as <i>t</i> increases from 1 to 11 mm. The da/dN between <i>t</i> = 11 and 21 mm is the same. Meanwhile, in the region where ΔK is less than 5 MPam<sup>1/2</sup>, the effect of <i>t</i> on da/dN is not observed. The effects of <i>t</i> and ΔK on the da/dN–△K relationship are considered physically and quantitatively based on <i>d</i>.
|
|---|
