Global response of the cyclic compression test carried out on the bolt head: evolution of penetration u(t)–u(t ₀) with respect to the number of cycles when F(t) varies from 0 to 360 N and back following a triangular signal for a maximum load F _max= 300 N (left) and F _max = 600 N (right). The upper (cyan) curve corresponds to the maximum penetration when the maximum load is applied, while the lower (red) curve corresponds to the residual permanent penetration δ_r when no more force is applied.