Life Prediction by Simulation of Crack Growth in Notched Components With Different Microstructures and Under Multiaxial Fatigue

Abstract

A modelling procedure was developed which is applicable to crack growth in notched components subjected to multiaxial fatigue for materials with different microstructures. An algorithm for crack growth, in a microstructure that was modelled as hexagons, was established as a competition between growth by crack linkages during the crack initiation and propagation stages and the propagation of a dominant crack as a single crack. Analytical results simulated by using the developed model were compared with experimental results from fatigue tests which had been conducted using notched specimens of pure copper, carbon steel and two kinds of titanium alloy. Cracking morphology, which was experimentally observed to depend on the microstructure and the loading mode, was well simulated using the present model. The fatigue failure life of a notched specimen was statistically estimated by a Monte Carlo procedure based on the model. The simulated life with a statistical scatter‐band almost coincided with the experimental data.

Fatigue Crack Initiation Simulation in Pure Iron Polycrystalline Aggregate

“…The CRSS was assumed based on a Taylor factor M = 3, τ c = 45 MPa and the surface fracture energy to apply the Tanaka-Mura model was taken from literature 13) , W c = 2 kJ/m 2 .…”

“…Hoshide and Kusuura 13) presented an analytical procedure to predict the crack pattern and fatigue life under multiaxial stresses using Voronoi polygons. The stress state inside each grain was assumed to be uniform and following a simple relation based on the applied stress.…”

Multi-challenge aspects in fatigue due to the combined occurrence of multiaxiality, variable amplitude loading, and size effects

“…It suggested itself to model the mechanisms by means of fracture mechanics [7][8][9][10][11][12][13][14][15][16][17][18][19]. Naturally initiating cracks require stress and strain amplitudes of a magnitude that usually prevents the application of linear elastic fracture mechanics.…”

Numerical Simulation of Fatigue Crack Initiation in Thin-walled High Strength Steel as Modeled by Voronoi-polygons

“…These values were reported by Hoshide et al for S35C grade carbon steel. 14) The grain that had the minimum Ni was manually cracked at the location of its potential crack path. Then, the stress distribution was recalculated considering the local stress concentration caused by the grain cracking.…”