An improved, automated finite element analysis for fatigue life predictions of notched components

Abstract

Among the causes for the breaking down of mechanical components, fatigue damage under cyclic stresses is by far the most common. Since this kind of damage is located in areas subject to the maximum cyclic stress amplitude, geometrical notches appear to be the most important site for fatigue failure. Understanding of the stress concentrators (notches) is an important element in the prevention of component failure, and is commonly assessed by a finite element analysis (FEA). In this research, it is intended to develop a methodology to automate the strain-based fatigue analysis in the FEA where the stress gradient and local plasticity effects are taken into account. The stress gradient effect is included by an empirical model to correlate the relative stress gradient (RSG) due to a stress raiser K f , and the local notch plasticity with the fatigue notch factor is approximated by the modified Neuber rule. The FEA modelling guidelines to extract the RSG value are then proposed for improved accuracy. fatigue life estimation models, nonlinear finite element analysis, and vehicle handling analysis and design. Dr Lee's research includes multiaxial fatigue, stress and strain plasticity, durability testing for automotive components (such as driveline, powertrain, and chassis components), fatigue of spot welds, and probabilistic fatigue and fracture design.

Multiaxial Fatigue Life Prediction of GH4169 Alloy Based on the Critical Plane Method

“…For thin-walled tube specimens loaded with continuous functions, theoretical methods can be used to calculate the position of the critical plane. However, for those components which have stress concentration and discontinuous function loading mode, in order to determine the location of the critical plane, the stress-strain state on the arbitrary plane at the danger point should be identified first [38]. For cases with notched members and triangular wave (discontinuous function) loading mode, the critical plane can be determined by the finite element method.…”

The effects of notch size and material microstructure on the notch sensitivity factor for notched components

“…Attempts have been made by different researchers to succinctly define the fatigue damage process zone [51][52][53]. In general, the fatigue damage process zone is a volume comprising of pre-fracture zones in the vicinity of the notch, inclusion or any other stress raisers identified in the material.…”

Microstructure-dependent fatigue damage process zone and notch sensitivity index

“…Motivated by microscopic observations that fatigue failure occurs by damage accumulation in a finite notch root damage process zone, which can encompass several grains, numerous research studies have explored estimation of the fatigue notch factor as well as fatigue strength as a function of an average stress over the fatigue damage process zone (Neuber 1961;Beremin 1983;Weixing 1992;Qylafku et al 1998Qylafku et al , 1999Ren and Nicholas 2003;Ranganathan et al 2004;Delahay and Palin-Luc 2006;Doudard et al 2007;Adib-Ramezani and Jeong 2007).These methods consider the average stress value over a significant length scale at the notch root when analyzing fatigue potency of a notched component. One of these methods, called the the point method, uses a specific distance known as the critical distance from the notch-root which may correspond to a grain size (Neuber 1958) or plastic zone size (Peterson 1959) and its corresponding average stress level to predict K f and fatigue life of notched components.…”