 Toughness is defined as the amount of energy per unit volume a material can absorb before rupturing.Because the amount of energy release is proportional to the amount of crack propagation, the blood vessel wall can withstand pressure and is “tough.” Thus, healthy blood vessels with the mechanical properties of the J-shaped stress-strain curve have greater stability against aneurysms than materials with linear elasticity.Blood vessels with aneurysms, on the other hand, are under the influence of an S-shaped stress-strain curve.