Fig. 2From: Numerical investigation of dynamic brittle fracture via gradient damage modelsA particular virtual perturbation \(\varvec{\theta }_t=\theta _t\mathbf {e}_1\) parametrized by two radii \(r<R\). We have \(\theta _t=1\) inside the ball \(B_r(\mathbf {P}_t)\), \(\theta _t=0\) outside the ball \(B_R(\mathbf {P}_t)\), and a linear interpolation in betweenBack to article page