From phase field to sharp cracks: Convergence of quasi-static evolutions in a special setting

We consider the quasi-static evolution of a straight crack within the recently developed phase-field approach and the classical sharp crack approach, and we show a strong correlation between the outcomes from the two approaches: the corresponding energies, minimizers, energy release rates and quasi-static evolutions converge as the internal length parameter of the phase-field model tends to zero. A crucial point in the proof is a novel representation of the energy release rate, which allows one to pass to the limit under weak convergence of the strains.