Rcurves
R-curves, short for resistance curves, are curves used in fracture mechanics to characterize how the fracture resistance of a material changes with crack extension. The curve presents either the stress intensity factor K or the energy release rate G (or the J-integral) required to propagate a crack by an incremental amount da. The abscissa is crack extension and the ordinate is the corresponding fracture resistance value (K_R, G_R, or J_R).
R-curves are particularly relevant for materials that undergo toughening mechanisms during crack growth, such as metals
Experimentally, R-curves are obtained using standard fracture tests, such as compact tension or three-point bending, where
They are used to assess structural integrity by comparing the maximum expected service driving force to the
Limitations include dependence on specimen size, mode mix, temperature, environment, and constraint; R-curves are not universal
See also: fracture mechanics, fracture toughness, J-integral, tearing resistance.