Computation of SIFs in StressCheck
There are three considerations when solving a 3D-elasticity problem for cracked bodies when the goal is the accurate computation of Stress Intensity Factors (SIFs):
- Approximability of the exact solution: The best rate of convergence is obtained by p-extension with a mesh graded in geometric progression towards the crack front with a grading factor of 0.15.
- Element mapping: Distorted elements decrease the quality of the computed stress field which is used in the extraction of SIFs by means of the Contour Integral Method (CIM).
- Path-independence: When computing SIFs by the CIM for corner and thru-thickness cracks in 3D, the SIFs are not independent of the radius of the integration path. It is necessary to use the stress field in the close vicinity of the crack front. This point is addressed in the following text and practical guidelines are provided.
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“Accurate and reliable stresses and Stress Intensity Factors are required for determination of static and residual strength and for crack growth analyses in analysis tools such as AFGROW. For some geometries, industry solutions are either insufficient or nonexistent. The geometry, applied forces, and crack shapes and dimensions must be modeled reasonably well to obtain useful engineering data. The p-version finite element software StressCheck® (ESRD, Inc., St. Louis, Missouri, USA) is used to demonstrate how accurate finite element solutions can lead to good quality engineering analysis.”