Q) New at 8.1 is the ability to input transverse shear stiffness (TSS) for gasket material (TB,GASKET,,,,TSS). Please explain what TSS is.
A) Gasket element/material is meant to provide a general 1D (throughthickness) representation of a more complicated multimaterial/complex geometry gasket. Consequently, 1D throughthickness behavior is characterized by complex compressive closure and linear/nonlinear unloading curves that may be temperature dependent.
Because of the fact that the gasket elements are used for 2D or 3D representation, the transverse behavior may be important. This is where TSS (transverse shear stiffness TBOPT for TB,GASKET) comes in.
TSS is in units of pressure/length and is just a linear constant (analogous to Young's modulus). It is really meant for stability purposes since the gasket behavior is supposed to be dominated in the throughthickness direction.
This value should be representative of the material being modeled, although it is a complex behavior being reduced to a single parameter, so, usually, TSS is taken to be a small value for stability purposes, anyway, since one wouldn't expect/want significant inplane deformation for gaskets.
KEYOPT(2)=1 needs to be set on INTER19x elements to activate transverse shear deformation calculations. If TSS is not defined, the "Stability stiffness" (C2) of TB,GASKET,,,,PARA will be used instead. Both have the same units of stress/length.
Q) New at 8.1 is the ability to input transverse shear stiffness (TSS) for gasket material (TB,GASKET,,,,TSS). Please explain what TSS is. A) Gasket element/material is meant to provide a general 1D (throughthickness) representation of a more complicated multimaterial/complex geometry gasket. Consequently, 1D throughthickness behavior is characterized by complex compressive closure and linear/nonlinear unloading curves that may be temperature dependent. Because of the fact that the gasket elements are used for 2D or 3D representation, the transverse behavior may be important. This is where TSS (transverse shear stiffness TBOPT for TB,GASKET) comes in. TSS is in units of pressure/length and is just a linear constant (analogous to Young`s modulus). It is really meant for stability purposes since the gasket behavior is supposed to be dominated in the throughthickness direction. This value should be representative of the material being modeled, although it is a complex behavior being reduced to a single parameter, so, usually, TSS is taken to be a small value for stability purposes, anyway, since one wouldn`t expect/want significant inplane deformation for gaskets. KEYOPT(2)=1 needs to be set on INTER19x elements to activate transverse shear deformation calculations. If TSS is not defined, the "Stability stiffness" (C2) of TB,GASKET,,,,PARA will be used instead. Both have the same units of stress/length. 

