If no value is given for the material compressibility in the hyperelastic model, by default Abaqus/Explicit assumes 20, corresponding to Poisson's ratio of 0.475. Some judgment is, therefore, required to decide whether or not the solution is sufficiently accurate, or whether the problem can be modeled at all with Abaqus/Explicit because of this numerical limitation. Thus, except for plane stress and uniaxial cases, you must provide enough compressibility for the code to work, knowing that this makes the bulk behavior of the model softer than that of the actual material. The difficulty is that, in many cases, the actual material behavior provides too little compressibility for the algorithms to work efficiently. Instead, we must provide some compressibility.
This ratio can also be expressed in terms of Poisson's ratio,, sinceĮxcept for plane stress and uniaxial cases, it is not possible to assume that the material is fully incompressible in Abaqus/Explicit because the program has no mechanism for imposing such a constraint at each material calculation point. We can assess the relative compressibility of a material by the ratio of its initial bulk modulus,, to its initial shear modulus. Elastomeric foams are discussed in “Hyperelastic behavior in elastomeric foams, ” Section 19.5.2.
In applications where the material is not highly confined, the degree of compressibility is typically not crucial for example, it would be quite satisfactory in Abaqus/Standard to assume that the material is fully incompressible: the volume of the material cannot change except for thermal expansion.Īnother class of rubberlike materials is elastomeric foam, which is elastic but very compressible. In cases where the material is highly confined (such as an O-ring used as a seal), the compressibility must be modeled correctly to obtain accurate results. This behavior does not warrant special attention for plane stress, shell, membrane, beam, truss, or rebar elements, but the numerical solution can be quite sensitive to the degree of compressibility for three-dimensional solid, plane strain, and axisymmetric analysis elements.
Most elastomers (solid, rubberlike materials) have very little compressibility compared to their shear flexibility.
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