Element Strain Energy Density Factor Approach to Assess Fracture and Fatigue Crack Growth

Authors

  • ZHAO FANG School of Civil Engineering and Architecture, Nanjing Institute of Technology; Jiangsu Key Laboratory of Intelligent Construction and Smart Operation & Maintenance of Power Infrastructurenology;
  • Fan Yang School of Civil Engineering, Southeast University
  • Sheng Shen School of Civil Engineering, Southeast University
  • Aiqun Li School of Civil Engineering, Southeast University; Beijing Advanced Innovation Center for Future Urban Design, Beijing University of Civil Engineering and Architecture
  • Jingwen Yu School of Civil Engineering and Architecture, Nanjing Institute of Technology

Abstract

A new approach to calculate strain energy density factor (SEDF) at a crack tip named the “element strain energy density factor (ESEDF) approach” based on finite element (FE) analysis was proposed. Cases of mode I, mode II, mode III and mixed mode cracks both in 2D models and 3D models were all demonstrated to show the application of this approach. The effect of mesh sizes on accuracy of results was also discussed. A da/dN-ΔS-R equation with consideration of stress ratios was proposed and material constants were obtained by fitting of fatigue crack growth test data. The results show that the proposed ESEDF approach skips the assumption of a plane stress/strain state for 3D problems and the calculation of stress intensity factors, by direct computation of SEDF from FE analysis results. It achieves more accurate results in mode I and mode II crack problems but less accurate results in mode III and mixed mode crack problems compared with the SEDF approach, while both can obtain accurate SEDF results; It is recommended to use quadratic singular elements to create a row of sector or prism elements at the crack tip with an angle of 10° and a radius of 0.001mm, while mesh patterns are allowed to be sparser to an angle of 15° and a radius of 0.5mm for complex large-scale engineering structures. The fatigue test results of CT specimens show that the proposed da/dN-ΔS-R equation is well applied to correlation of fatigue crack growth rate with SEDF ranges considering stress ratios.

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Published

25-06-2026

Issue

Articles in Press

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Original Article

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