Mechanical-Nonlin 13.0 App5Ba Gaskets
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Transcript of Mechanical-Nonlin 13.0 App5Ba Gaskets
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Customer Training Material
Appendix 5B
Modeling Gaskets
Structural Nonlinearities
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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
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Example of Gaskets used in Engines
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ANSYS Mechanical Modeling Gaskets
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
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Closure
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ANSYS Mechanical Modeling Gaskets
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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ANSYS Mechanical Modeling Gaskets
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
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Integration point locations on midplane shown with x
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ANSYS Mechanical Modeling Gaskets
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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ANSYS Mechanical Modeling Gaskets
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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ANSYS Mechanical Modeling Gaskets
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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ANSYS Mechanical Modeling Gaskets
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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ANSYS Mechanical Modeling Gaskets
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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ANSYS Mechanical Modeling Gaskets
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
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Closure
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ANSYS Mechanical Modeling Gaskets
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
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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
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