Stabilize the response of certain element types.
Certain types of Abaqus/Standard elements (e.g., beam elements, shell elements, and reduced integration elements) require extraneous stiffness parameters in order to stabilize their response against deformation modes that are not governed directly by material constitutive relations. These extraneous stiffness parameters are defined as either options or data in the Section keyword statement that is referenced by the element in question. Depending upon the specific type of element being used, one or more of the following types of extraneous stiffness parameters may need to be specified as part of the Section definition.
- Section Poisson Ratio
- Section Thickness Modulus
- Section Transverse Shear Stiffnesses:
, 
, and 
- Membrane Hourglass Stiffness Control Parameter (Abaqus/Standard only)
- Bending Hourglass Stiffness Control Parameter (Abaqus/Standard only)
Helius PFA includes an auxiliary program (xStiff) that automatically calculates and inserts the required extraneous stiffness parameters into the Abaqus input file. The use of xStiff is highly recommended as it greatly accelerates the model building process, while at the same time minimizing the chance for errors to be introduced into the input file. With xStiff, you can postpone the task of defining the extraneous stiffness parameters until the model building process is completed and an Abaqus input file is saved. xStiff can then be run to automatically add any required extraneous stiffness parameters to the saved Abaqus input file. For more information on using xStiff to automatically calculate and insert the required extraneous stiffness parameters into the Abaqus input file, please refer to Use xStiff to Insert Extraneous Stiffness Parameters.