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.

Fatigue crack growth in MAR-M200 single crystals

Abstract: The effects of crystallographic orientation on the fatigue crack growth behavior of MAR-M200* single crystals were examined. Using compact-tension specimens tested at 20 Hz, fatigue crack growth rates were determined at ambient temperature at minimum stress to maximum stress ratios,R, of 0.1 and 0.5. In most cases, subcritical crack growth occurred either along a single {111} slip plane or a combination of {111} planes. The mode of cracking was generally mixed and contained mode I, II, and III components. Considerable crack deflection and branching were also observed. Some fracture surfaces were found to contain a significant amount of asperities and, in some specimens, black debris. Based on Auger spectroscopic analyses and the fracture surface appearance, it appears that the black debris represented oxides formed due to rubbing of the fracture surfaces. Using stress intensity solutions obtained based on the Boundary-Integral-Equation technique, an effective ΔK was successfully used for correlating the crack growth rate data. The results indicate that the effect of crystallographic orientation on crack growth rate can be explained on the basis of crack deflection, branching, and roughness-induced crack closure.

Fatigue Crack Growth Database for Damage Tolerance Analysis

Abstract: The objective of this project was to begin the process of developing a fatigue crack growth database (FCGD) of metallic materials for use in damage tolerance analysis of aircraft structure. For this initial effort, crack growth rate data in the NASGRO (Registered trademark) database, the United States Air Force Damage Tolerant Design Handbook, and other publicly available sources were examined and used to develop a database that characterizes crack growth behavior for specific applications (materials). The focus of this effort was on materials for general commercial aircraft applications, including large transport airplanes, small transport commuter airplanes, general aviation airplanes, and rotorcraft. The end products of this project are the FCGD software and this report. The specific goal of this effort was to present fatigue crack growth data in three usable formats: (1) NASGRO equation parameters, (2) Walker equation parameters, and (3) tabular data points. The development of this FCGD will begin the process of developing a consistent set of standard fatigue crack growth material properties. It is envisioned that the end product of the process will be a general repository for credible and well-documented fracture properties that may be used as a default standard in damage tolerance analyses.

Prediction of fatigue crack growth rates: theory, mechanisms, and experimental results

Abstract: A range of continuum-based crack growth laws are reviewed and it is concluded that they may be divided into those based on instantaneous values of cyclic crack-opening displacement which have a ∆K exponent of 2 and those based on damage or strain accumulation which have a ∆K exponent of 4 and, in addition, predict the onset of rapid crack acceleration as K→ Ic. No laws showing how to introduce the effects of aggressive environments were found. A third type of law, based on energy-balance concepts within a crack tip process zone, can predict a gradient lying between 2 and 4 depending on the size of the reversed plastic zone. Comparison between theory and experiment suggests that the (∆K)4 type laws provide better agreement for data gathered in inert environments. It is thought that, when growth laws are being assessed by comparison with experimental observations, data gathered in inert environments should be used. In addition it is noted that when experimentally and theoretically determined exponen...