Defining shell-to-solid coupling
shell_surface (edge) solid_surface (face) The shell surface must be edge based
*SURFACE, TYPE=ELEMENT, NAME=shell_surface shell_surface_E1, E1
*SHELL TO SOLID COUPLING, CONSTRAINT NAME=C1 shell_surface, solid_surface
an edge identifier
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Contact (1/12)
What is contact?
When two solid bodies touch, force is transmitted across their common surface.
In some cases only forces normal to the contact surfaces are transmitted.
If friction is present, a limited amount of force tangent to the contact surfaces also can be transmitted.
I. Frictional forces cause shear stresses along the contact surfaces.
General objective: Determine contacting areas and stress transmitted.
Contact is a severely discontinuous form of nonlinearity.
Either a constraint must be applied (that the surfaces cannot interpenetrate) or the constraint is ignored.
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Contact (2/12)
Contact examples Gap contact
Point contact is modeled as node-to-node contact.
This example is taken from “Detroit Edison pipe whip experiment,”
Example Problem 2.1.2 in the Abaqus Example Problems Manual.
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Contact (3/12)
Hertz contact
Small displacements of the contact surfaces relative to each other.
Contact over a distributed surface area.
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Contact (4/12)
Large-sliding contact between deformable bodies
This is the most general category of contact.
Example: threaded connector.
These problems typically involve an initial interference fit (because of the tapered thread), followed by finite sliding between bodies made of similar strength materials.
Contact pressure distribution due to interference resolution This example is loosely based on “Axisymmetric analysis of a threaded connection,” Example Problem 1.1.20 in the Abaqus Example Problems Manual.
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Contact (5/12)
Self-contact
Self-contact is contact of a single surface with itself. It is available in two- and three-dimensional models in Abaqus.
It is convenient when a surface will deform severely during the analysis and it is not possible, or it is very difficult, to determine individual contacting regions in advance.
Self-contact is defined by specifying a single contact surface as a contact pair instead of two different surfaces.
Contour of minimum principal stress
SURF1 (rigid)
SURF2
Example: Compression of a rubber gasket (taken from “Self-contact in rubber/foam components: rubber gasket,” Example Problem 1.1.18 in the Abaqus Example Problems Manual).
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Contact (6/12)
Deformable to rigid body contact
Finite sliding between the surfaces (large displacements).
Finite strain of the deforming components.
Typical examples:
I. Rubber seals II. Tire on road III. Pipeline on seabed IV. Forming simulations
(rigid die/mold,
deformable component).
This example is taken from “Superplastic forming of a rectangular box,” Section 1.3.2 in the Abaqus Example Problems Manual.
Example: metal forming simulation
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Contact (7/12)
Abaqus provides two approaches for modeling surface-based contact:
General contact allows you to define contact between many or all regions of a model with a single interaction.
The surfaces that can interact with one another comprise the contact domain and can span many disconnected regions of a model.
Contact pairs describe contact between two surfaces.
Requires more careful definition of contact.
I. Every possible contact pair One contact domain in general contact
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Contact (8/12)
The general contact algorithm
The contact domain spans multiple bodies (both rigid and deformable)
Default domain is defined automatically via an
all-inclusive element-based surface The method is geared toward models with multiple components and complex topology
Greater ease in defining contact model
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Contact (9/12)
The contact pair algorithm
Requires user-specified pairing of individual surfaces
Often results in more efficient analyses since contact surfaces are limited in scope
Slave surfaces for contact pair analysis
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Contact (10/12)
The choice between general contact and contact pairs is largely a trade-off between ease of defining contact and analysis performance
Robustness and accuracy of both methods are similar
In some cases, the contact pair approach is required in order to access specific features not available with general contact.
These include:
Analytical rigid surfaces (Abaqus/Standard) Two-dimensional models (Abaqus/Explicit) Node-based surfaces
Small sliding
Rough or Lagrange friction (Abaqus/Standard)
See the Abaqus Analysis User’s Manual for a complete list of general contact limitations
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Contact (11/12)
Some additional details Abaqus/Standard
Contact pairs: "Node-to-surface" contact discretization is used by default:
I. Nodes on one surface
(the slave surface) contact the discretized
segments on the other surface (the master surface).
II. Also known as a strict master/slave formulation General contact: “Surface-to-surface" contact discretization
I. Contact is enforced in an average sense.
II. This form of contact discretization may also be used with contact pairs Abaqus/Explicit
A balanced master/slave formulation is used in most cases.
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Contact (12/12)
Contact pairs in Abaqus/Standard
The default strict master/slave formulation used in Abaqus/Standard has certain implications.
Slave nodes cannot penetrate master surface segments.
Nodes on the master surface can penetrate slave surface segments.
The contact direction is always normal to the master surface.
I. The contact condition is checked along the normal to the master surface.
II. Normal contact forces are transmitted along the normal direction.
III. Frictional forces are transmitted tangent to the contacting surfaces.
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