Abstract
ABSTRACTNowadays cast iron components are widely used in highly stressed structures. Component lifetime is strongly influenced by inhomogeneities caused by the material's microstructure and the manufacturing process (graphite particles, (micro‐)shrinkage pores, inclusions). Inhomogeneities often act as a fatigue crack starter. Lifetime until failure may be divided into stages for crack initiation, short and long crack growth. Initiation of a crack of technical size (a ≈ 1mm) is often dominated by the growth of short cracks. The paper presents an approach to analyse the mechanically short fatigue crack growth based on elastic‐plastic fracture mechanics considering the closure behaviour of short cracks. The effective J‐integral range is used as a crack driving force. Finite element analysis results as well as analytical solutions to approximate the crack driving force are presented. The application of the approach is successfully demonstrated for cast iron material EN‐GJS‐400‐18‐LT using data from fatigue tests, microstructure and fracture surface analyses to assess the fatigue life.
Highlights
Nowadays cast iron components are produced with a very high casting quality due to constant enhancement of the casting processes
In stage 1 of the microstructurally short cracks, their growth is heavily influenced by the local microstructure and cannot be described using fracture mechanics approaches from the continuum mechanics point of view
The result is plasticity-dependent enhancement of the crack tip loading. It may be described from the continuum mechanics point of view, it cannot be described adequately on the basis of linear-elastic fracture mechanics
Summary
Nowadays cast iron components are produced with a very high casting quality due to constant enhancement of the casting processes. With the exception of the high strain amplitudes present in the LCF range, can be described using linear-elastic fracture mechanics approaches. Possible correlation of the fatigue crack growth of mechanically short cracks and long cracks using the effective J-integral range according to Eq (2) is presented in [11] for various steels and a wrought aluminium alloy.
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