Improved test method and analytical modelling for fatigue crack growth in coarse‐grain titanium alloy with rough fatigue surfaces

• DOI: 10.1111/ffe.12148
• Publication Date: 2014-02-20T07:17:18Z
• Authors: K. F. Walker; J. C. Newman
• Keywords: Paris' law; Titanium alloy

ABSTRACT Fatigue crack growth rate properties are typically determined by experimental methods in accordance with ASTM Standard E647. These traditional use standard notched specimens that precracked under cyclic tensile loads before the main test. The data produced using this approach have been demonstrated elsewhere to be potentially adversely affected test method, particularly threshold region where load reduction (LR) also required. Coarse‐grained materials exhibit rough and tortuous fatigue surfaces observed strongly precracking LR, part because anomalies caused closure roughness‐induced become more important. focus of work reported paper was further develop determine accurate from through fracture for coarse‐grained, β‐annealed, titanium alloy Ti‐6Al‐4V extra low interstitial thick plate material. A particular emphasis put upon near region, which is strong importance overall life components. New approaches differ included compression precracking, LR starting a lower level continuing beyond rates would otherwise considered below threshold. For regime, two were investigated: method reduced such mouth opening displacement held constant, an attempt avoid remote closure. Constant amplitude at variety stress ratios. Spike overload tests conducted then used improved analytical model predict spectrum loading predictions found correlate well results.