Scale Invariance of Fatigue Crack Growth Under Very‐High‐Cycle Fatigue in Ti‐6Al‐4V Alloy After Surface Treatment With Nanosecond Laser Pulses

In this paper, using the original laboratory software and hardware systems, we investigate the structurally determined patterns of fracture stages in titanium alloy Ti‐6Al‐4V under consecutively applied short laser pulses (shock wave) and fatigue loads with the aim to predict the lifetime of advanced aircraft engine materials. It is shown that laser surface treatment followed by the grinding operation providing the desired roughness quality is a promising tool for increasing the fatigue resources of aircraft engine materials. Spatial structural scales associated with different stages of damage‐failure transition are determined by analyzing the roughness correlation and evaluating the power (Hurst) exponent and the corresponding structural lengths of characteristic fracture surfaces. These lengths and power exponents are incorporated into the constitutive laws as structure‐sensitive parameters that characterize different stages of the damage‐failure transition, which involve the initiation and growth of small cracks as well as the Paris crack propagation.