A Practical Two Surface Plasticity Theory

Abstract

A plasticity theory is presented using the usual concept of a loading surface which moves and isotropically grows, but in addition uses a “limit surface” which grows and moves independently and encloses the loading surface. The plastic stiffness is a function of the distance between the surfaces at the loading point. Characteristics of the theory are a smoother transition between elastic and plastic regions on loading, an inherent Bauschinger effect, and more latitude on the description of hardening characteristics than the traditional methods used in structural codes. The full capability of the theory requires a memory of three vectors and three scalars, while some of the foregoing characteristics can be retained with only two vectors, the same as a traditional kinematic hardening model. The multiaxial theory is presented, particularized, specialized to uniaxial stress and the equations solved. The theory is compared to uniaxial stress experimental results.