Elements tested
- GK2D2
- GK2D2N
- GK3D2
- GK3D2N
- GK3D4L
- GK3D4LN
- GK3D6
- GK3D6L
- GK3D6LN
- GK3D6N
- GK3D6T
- GK3D6TN
- GK3D8
- GK3D8N
- GK3D8T
- GK3D8TN
- GK3D12M
- GK3D12MN
- GK3D18
- GK3D18N
- GKAX4
- GKAX4N
- GKAX6
- GKAX6N
- GKPE4
- GKPE6
- GKPS4
- GKPS4N
- GKPS6
- GKPS6N
ProductsAbaqus/Standard Elements tested
Problem descriptionGasket elements are used to model sealing components between structural members. They are designed primarily to provide appropriate pressure-closure behavior in the thickness direction, which is uncoupled from the transverse shear and membrane behavior. This uncoupled pressure-closure behavior is specified with the suboptions of the gasket behavior definition. These gasket behavior models are separate from the models in the material library. For some gasket behaviors that are not addressed readily by these special behavior models, such as coupled compression-membrane behaviors or through-thickness tensile behavior, Abaqus provides an alternative way for the user to model such behavior by specifying either a built-in or user-defined material model. Gasket elements with all displacement degrees of freedom active at their nodes are used to model all three types of behavior (thickness-direction, membrane, and transverse shear). Elements that have only one displacement degree of freedom at their nodes consider the thickness-direction behavior only. Analyses are performed to verify that the generalized strains (displacements and strains) in the gaskets are obtained properly from the nodal displacements and that the generalized stresses (forces, forces per unit length, or stresses) are obtained properly from the generalized strains through the constitutive relations for the different types of behavior. BehaviorThe element tests included in this section cover three different types of model behavior in the thickness direction: elastic with damage, elastic-plastic with high initial stiffness so that yield occurs at the second data point given along the initial loading curve, and elastic-plastic with low initial stiffness so that initial yield occurs further along the initial loading curve. Rate-dependent (creep) effects through the thickness of the gasket may be added to the elastic-plastic model. These models are used with or without any initial gap. Thermal expansion is also considered along the thickness direction of the gasket with or without an initial void. The thickness-direction behavior is defined in terms of stress in most cases but is defined as force or force per unit length whenever it is appropriate for the element type. Membrane behavior and transverse shear behavior are modeled as linear elastic. Thermal expansion is also considered for the membrane response. Some tests involving viscoelastic effects (in the frequency domain) in conjunction with the elastic or elastic-damage models have also been included. These tests model the frequency-dependent stiffness and damping characteristics of gaskets for different levels (as measured by closure) of preload. Only thickness-direction viscoelastic behavior is modeled in these cases. Field expansion is also tested for a 2–node two-dimensional gasket. ModelEach model contains a set of 1 to 4 gasket elements of the same type. The initial geometry may or may not be aligned with the global axes. When gasket elements with thickness-direction-only behavior are used, the model may also contain a rigid element that is used to control the loading of the gasket. The tests for the gasket elements using suboptions of the material model are elastic-plastic creep analyses. Corresponding solid elements are included in the tests to facilitate the comparison of solutions. The material properties for the tests involving viscoelastic behavior include specification of storage and loss moduli as functions of excitation frequency and level of preload (closure). Loading historyThe different tests include compression along the thickness direction of the gasket, shearing of the top surface of the gasket with respect to its bottom surface (whenever possible), and uniform extension or compression of the gasket membrane. The tests are displacement- or load-controlled through direct control of the gasket element's nodes or through a contact pair that involves the gasket and a rigid component compressing the gasket. The tests also include thermal loading in the gasket membrane and/or gasket thickness direction. The tests performed along the thickness direction of the gasket involve, in most cases, a series of loading and unloading steps to verify that the user-prescribed loading and unloading curves are followed properly and that interpolation between user-specified unloading curves is done correctly. The tests involving the modeling of viscoelastic behavior consist of steady-state harmonic oscillations at different excitation frequencies about base states that involve different levels of closure. These tests are displacement controlled. Results and discussionThe results are obtained at the end of each step in terms of generalized stresses, generalized strains, reaction forces, and nodal displacements. The results obtained in each test match the results obtained by hand calculations. Input files
| |||||||