## An outline of hypoplasticity.(English)Zbl 0734.73023

Summary: The so-called hypoelastic constitutive equations, defined by the equation $$\overset \circ T=h(T,D)$$, are limited by the requirement that h is linear in D. Dropping this requirement and relating positive homogeneity of the first degree in D leads to a broader class of equations which can be called hypoplastic. Such equations are appropriate to describe the anelastic behaviour of granular materials. Some properties of hypoplastic equations are discussed in this paper including the new notions of yield and bound surfaces which are given a completely different meaning than in classical elastoplasticity. Possibilities to enlarge hypoplasticity towards rate-dependence and more complex intrinsic memory of the material are pointed to.

### MSC:

 74C99 Plastic materials, materials of stress-rate and internal-variable type 74A20 Theory of constitutive functions in solid mechanics 74B20 Nonlinear elasticity 74C15 Large-strain, rate-independent theories of plasticity (including nonlinear plasticity) 74C20 Large-strain, rate-dependent theories of plasticity 74R20 Anelastic fracture and damage

### Keywords:

yield; bound surfaces