 Unlike crystalline materials whose linear elastic region follows Hooke's Law under uniaxial loading, many biomaterials exhibit a J-shaped stress-strain curve which is non-linear and concave up.The blood vessel can be under large strain, or the amount of stretch the blood vessel can undergo, for a range of low applied stress before fracture, as shown by the lower part of the curve.The area under the curve up to a given strain is much lower than that for the equivalent Hookean curve, which is correlated to toughness.