A Book says, " When a load is acting on a member, it undergoes deformation. An internal resistance is developed against deformation by the member and the intensity of this internal resistance is called stress." I also read, "When a member is in its elastic range, it offers resistance against deformation and when it goes beyond the elastic range, i.e. plastic range, there is no resistance offered by the member against deformation." But, in a stress-strain curve, the stress keeps increasing even after the elastic range until the ultimate tensile stress which is in the plastic range. How does stress ( RESISTANCE) increase in the plastic range when it is clearly stated that the member does not actually offer resistance after the elastic range??