Paris' law

About: Paris' law is a research topic. Over the lifetime, 13815 publications have been published within this topic receiving 224818 citations. The topic is also known as: Paris-Erdogan law.

The influence of load ratio on fatigue crack growth in 7090-t6 and in9021-t4 p/m aluminum alloys

Abstract: The rate of fatigue crack growth has been studied over a wide range of growth rates in two high strength P/M aluminum alloys as a function ofR, with particular attention given to crack closure and near-threshold behavior. A principal difference between the two alloys was grain size, being less than oneµm for the alloy IN9021* and greater than five µm for the alloy 7090. No closure was found in the fine-grained alloy nor was there any dependency of the threshold level onR. In contrast, closure was observed in the coarser grained alloy and there was also a dependency of the threshold level onR. The observations are discussed in terms of current models for threshold behavior. Consideration is also given to the overall fatigue crack growth behavior of these P/M in comparison to that of a conventional high strength I/M aluminum alloy.

Characterization and analysis of surface notches on Ti-alloy plates fabricated by additive manufacturing techniques

Abstract: Rectangular plates of Ti–6Al–4V with extra low interstitial (ELI) were fabricated by layer-by-layer deposition techniques that included electron beam melting (EBM) and laser beam melting (LBM). The surface conditions of these plates were characterized using x-ray micro-computed tomography. The depth and radius of surface notch-like features on the LBM and EBM plates were measured from sectional images of individual virtual slices of the rectangular plates. The stress concentration factors of individual surface notches were computed and analyzed statistically to determine the appropriate distributions for the notch depth, notch radius, and stress concentration factor. These results were correlated with the fatigue life of the Ti–6Al–4V ELI alloys from an earlier investigation. A surface notch analysis was performed to assess the debit in the fatigue strength due to the surface notches. The assessment revealed that the fatigue lives of the additively manufactured plates with rough surface topographies and notch-like features are dominated by the fatigue crack growth of large cracks for both the LBM and EBM materials. The fatigue strength reduction due to the surface notches can be as large as 60%–75%. It is concluded that for better fatigue performance, the surface notches on EBM and LBM materials need to be removed by machining and the surface roughness be improved to a surface finish of about 1 μm.