Slow Crack Growth and Crack-Tip Strain Characteristics Under Constant Loading

Investigations have been conducted on crack growth and crack-tip strain characteristic of stable fibrous crack. Double edge-cracked tension specimens of mild steel have been prepared for both monotonic loading and constant loading tests. After unloading test, the measurements of crack-tip profile, COD at moving crack tip (CTOD) and crack-tip strain distribution of mid-cross section of specimens have been carried out.When COD at initial crack tip (δ) is determined, fibrous crack length, crack-tip profiles, CTOD, and crack-tip strain distribution are uniquely evaluated regardless of loading history. A. critical COD δiis a required displacement for initiation of slow crack growth regardless of loading history. CTOD abruptly decreases as fibrous crack length increases. Moreover, crack-tip strain increases as COD at initial crack tip or fibrous crack length increases. Crack-tip strain fields under both loadings have HRR-singularities.