The Theory of Instability of the Tearing Mode of Elastic-Plastic Crack Growth

Abstract

This paper presents a new approach to the subject of crack instability based on the J-integral R-curve approach to characterizing a material's resistance to fracture. The results are presented in the chronological order of their development (including Appendices I and II). First, a new nondimensional material parameter, T, the “tearing modulus,” is defined. For fully plastic (nonhardening) conditions, instability relationships are developed for various configurations, including some common test piece configurations, the surface flaw, and microflaws. Appendix I generalizes these results for the fully plastic case and Appendix II treats confined yielding cases. The results are presented for plane-strain crack-tip and slip field conditions, but may be modified for plane-stress slip fields in most cases by merely adjusting constants. Moreover, an accounted-for compliance of loading system is included in the analysis. Finally, Appendix III is a compilation of tearing modulus, T, properties of materials from the literature for convenience in comparing the other results with experience.

Review of fracture toughness (G, K, J, CTOD, CTOA) testing and standardization

“…A material with a steep R curve is less likely to experience unstable crack propagation. To describe the onset of tearing instability of ductile crack growth, Paris et al [136] defined a dimensionless applied and a material tearing modulus:…”

A Computer-Controlled Automated Test System for Fatigue and Fracture Testing

“…The routine displays the results and the power-law fit on the CRT and prompts the operator to accept the fit; if the fit is rejected, any suspect test results may be excluded and the regression repeated. Once the fit Is accepted, the power-law fit plot (including ghosted symbols for any excluded results) is dumped to the printer, J Io is determined in accordance with ASTM E 813, and the tearing modulus 19 is calculated.…”

Effect of Strain Dependent Cohesive Zone Model on Predictions of Interface Crack Growth

“…To incorporate such effects, Tvergaard and Hutchinson [3] and Tvergaard [4] have used a modified traction-separation law so that plastic straining gives a reduction of the peak stress for separation (see also Tvergaard [5,6]). This modified model allows for a better representation of very tough materials with a high value of the tearing modulus defined in [7]. Since plastic straining near the tip is sensitive to the element size, this modified model displays some mesh dependence.…”