Mechanical-Nonlin 13.0 App5Ba Gaskets

8/12/2019 Mechanical-Nonlin 13.0 App5Ba Gaskets

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Customer Training Material

Appendix 5B

Modeling Gaskets

Structural Nonlinearities

A5B-1 ANSYS, Inc. Proprietary 2010 ANSYS, Inc. All rights reserved.

Release 13.0December 2010


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ANSYS Mechanical Modeling Gaskets

Customer Training Material A. Background on Gaskets Gaskets serve two main purposes in many

structural assemblies: Provide tight and durable seal between parts Transfer mechanical forces between

components

Characteristics of Gaskets: Multi-layered, metal, elastomer Thin in one direction, but through-thickness

behavior is most important Usually negligible in-plane sti ness As a result, can exhibit highly nonlinear loading

and unloading behavior with permanent



Example of Gaskets used in Engines


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Customer Training Material Background on Gaskets

Because gaskets are often multilayered materials, the overallresponse is quite nonlinear.

Complete gasket behavior is characterized by a pressure vs.mechanical closure relationship

Unloading paths can be different, depending on the point at whichunloading occurs

Permanent deformations can exist in the material, as shown in thecurve below

r e

P r e s s



Closure


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Customer Training Material B. Gasket Bodies

A Solid Body can be treated as agasket by simply setting itsStiffness Behavior in the DetailsWindow to Gasket

With this designation, the Gasketbody will be meshed with special

next).

This option is only valid for 3DSolid Bodies for structuralanalysis.




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Customer Training Material ... Gasket Bodies

Gasket Bodies are meshed with special interface elements having thefollowing unique characteristics

Only one element thru gasket thickness. Allows for measurement of closure which is the relative deformation

between top and bottom faces of interface element The midplane of the gasket element serves as the location where

elements)

Closure



Integration point locations on midplane shown with x


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Customer Training Material ... Gasket Bodies Stiffness response of the gasket element is established by user

defined Pressure vs. closure data directly as a material property inEngineering Data.

A separate FE model with continuum elements may be used to derivethese curves analytically

Response follows the same compression curve in unloaded vance un oa ng opt ons are ava a e y way o comman s Response assumed to be rate-independent

Cannot combine with other nonlinear material models.




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Customer Training Material C. Mesh Control

Upon designating a solid body as aGasket, a Gasket Mesh Control object isadded beneath the Body object in thetree.

The meshing method for the control willbe set to sweep and allow user to indicate

.




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Customer Training Material ... Mesh Control

In the Details view of the Gasket Mesh Control object, the Mesh Methodis set to Sweep.

Src/Trg Selection is set to Manual Source:

Select a Source face. The selected facemust lie on the gasket body. The Target selection is Program

Controlled by default. If desired, you canset Src/Trg Selection to Manual Source

and Target. Then you can choose Target.

If desired, you can change the value ofthe Free Face Mesh Type control to AllQuad, Quad/Tri, or All Tri.




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Customer Training Material ... Mesh Control By design, Gasket Bodies must always be sweep meshed.

If possible, they can share nodes with adjacent solid bodies. Often, it is necessary for gaskets can be independently meshed and

connected to adjacent solid bodes by way of contact regions.

Contact Region

Gasket

Contact Region




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Customer Training Material D. Material Properties From the Toolbox, RMB on Gasket Material

and Include Property The Gasket material properties Pressure vs.

osure a a can en e en ere rec y n

a Tabular form and displayed graphically.




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Customer Training Material ... Material Properties

Assumptions related to gasket material: If response is outside of compression curve, slope of last segment is

used. For temperatures between defined temperature sets, linear interpolation is

used If outside of temperature range, closest temperature data of compression

curve will be used.

Linear or nonlinear unloading different from the pressure vs closurecan be introduced with MAPDL commands.

P r e s s u r e



Closure


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Customer Training Material ... Material Properties Define unloading behavior with MAPDL as follows:

Linear unloading TB, GASKET,,,2,LUNL TBPT ,,X1,Y1 TBPT ,,X2,Y2 Where: Xi = Closure value P

r e s s u r

e

Nonlinear unloading TB GASKET 2 NUNL

osure

TBPT ,,X1,Y1 TBPT ,,X2,Y2 Where: Xi = Closure value

e s s u r e

Yi = Pressure value

If unloadin occurs between defined curves linear inter olation is used

Closure

P r



If outside of closure range, closest closure values are used for unloading curve.

Reloading occurs along unloaded path


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Customer Training Material ... Material Properties

Other Advanced options that can effect accuracy and convergence ofgasket elements are available via MAPDL commands :

Treatment of tensile stiffness with TB, GASKET,,,,PARA TBDATA, 1,C1,C2,C3Where: C1 = initial gap (default = 0)

= a e s ness e au =C3 = Max tension stress in gasket (default = 0)

TB, GASKET,,,,TSS TBDATA, 1,TSSXY,TSSXZWhere: TSSXY is allowable shear stress alon XY lane

TSSXZ is allowable shear stress along XZ plane




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Customer Training Material E. Gasket Results

The following Gasket output is available as separate Solution items Normal Gasket Pressure Shear Gasket Pressure Normal Gasket Total Closure Shear Gasket Total Closure



Mechanical-Nonlin 13.0 App5Ba Gaskets

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