Abstract
The assessment of fatigue crack propagation of steel structures is essential and important especially to improve the application of high strength steel in construction. The load ratio R, reflecting mean stress effects, will be changed with crack extension in the steel structures with complicated geometry. In this paper, the Walker equation is employed to fit the fatigue crack propagation rate of steel grades S355 and S690 based on experimental data in the literature to incorporate the mean stress effects. The material fatigue crack propagation parameters with 95%, 97.7%, and 99% guarantee of Walker equation were obtained by a stochastic analysis using the Monte Carlo method. The fatigue life was firstly predicted by the analytical method and was used as a baseline for numerical fatigue crack propagation simulation. A user-defined fatigue crack propagation subroutine based on the Walker equation was developed using phantom nodes-based extended finite element method (PN-XFEM) and Virtual Crack Closure Technique (VCCT) to consider the mean stress effects. The proposed three-dimensional fatigue crack propagation simulation subroutine is successfully validated of both steel grades, S355 and S690.
Highlights
The application of high strength steel in construction is becoming increasingly attractive during the past two decades, especially in infra structure applications
The fatigue life was firstly predicted by the analytical method and was used as a baseline for numerical fatigue crack propagation simulation
The Walker equation is employed to fit the fatigue crack propagation rate of steel grades S355 and S690 based on experimental data in the literature to incorporate the load ratio effects
Summary
The application of high strength steel in construction is becoming increasingly attractive during the past two decades, especially in infra structure applications. The commercial software ABAQUS [57] includes the extended finite element method (XFEM) [28] to pre dict the fatigue crack growth using original Paris’ law based on Griffith energy rate (G) and the Virtual Crack Closure Techniques (VCCT). In this way, the load ratio effects on fatigue crack propagation properties of structural steels are not considered currently. The crack propagation model in the commercial software ABAQUS is ex pected to be extended, and the material parameters of steel grades S355 and S690 are suggested to be fitted to incorporate the stress R-ratio ef fects to tackle the shortcoming of original Paris’ equation. The proposed threedimensional fatigue crack propagation simulation method is success fully validated of both steel grades, S355 and S690
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