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Tetrahedral elements available in ABAQUS for structural analysis? When to use what?
For a 3D stress analysis, ABAQUS offers 4 different classifications of quadratic tetrahedral elements namely C3D10, C3D10M, C3D10H and C3D10I. Although it is very clear that C3D10H are hybrid elements and primarily intended for simulating incompressible materials (e.g. Hyperelastic behavior modeling with rubber, human muscle tissue etc.), many users often tend to confuse between using the remaining elements. Let us take a look at using these elements with respect to contact analysis in ABAQUS/Standard.
C3D10 are textbook formulation second-order tetrahedral elements. Upon applying a uniform pressure load to its face these elements generate zero nodal forces at corner node rendering them not suitable for contact simulations. This drawback could be negated with the usage of finite sliding surface to surface formulation for contact. ABAQUS recommends using this combination for any contact analysis with C3D10 tetrahedral elements. Here enforcement method also plays a crucial role. C3D10 elements are recommended for any contact involving finite sliding with node to surface or surface to surface formulation when used with penalty enforcement method. Please note that penalty enforcement method is the default method in ABAQUS/Standard for contact enforcement.
Now why do we have C3D10M elements then? C3D10 elements do not yield desirable results when used with finite sliding, node to surface formulation and direct enforcement method. With C3D10M elements, a significant improvement in contact results can be noted with above combination. Ideal usages include modeling edge to surface or point to surface contact with direct enforcement. However ABAQUS no longer recommends C3D10M elements for this type of contact as well. C3D10 elements with node to surface formulation and penalty enforcement method are ideally recommended. C3D10M elements come with certain disadvantages. They are ‘modified’ formulation elements using bilinear interpolation and hence, they are not a true second-order element. Basically, this means that C3D10M will be unable to capture curvature as smoothly as C3D10 elements. Hence, should not be used for master regions in a contact pair. They also do not capture bending well due to the formulation.
C3D10I are ‘improved’ formulation elements. They behave in much the same way as C3D10 elements. However, their integration points are at its nodes. Hence, results based on integration points (such as stresses and strains) do not suffer from extrapolation errors, as with C3D10 or C3D10M. It is for this reason that these elements are said to have ‘improved surface stress visualization’. In this sense, C3D10I is a good choice for fatigue problems where surface stresses are critical. Further, C3D10I automatically invokes internal constraints to handle incompressible (or nearly incompressible) materials, such as hyperelasticity or plasticity. As for contact, the guidelines are exactly the same as for C3D10. Be aware that C3D10I elements do not provide any additional advantage over C3D10 for contact analysis, although C3D10I elements are more costly computing wise in comparison to its counterparts.
In summary, the contact formulation influences which type of tetrahedral element should be used. We hope this gives you some general idea about using second-order tetrahedral elements for contact analysis in ABAQUS/Standard. Feel free to reach out to us if you need any further information on this topic.