introduction to contact chapter seven. training manual october 15, 2001 inventory # 001565 7-2 7....

Introduction to Contact

Chapter Seven

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Training Manual7. Introduction to contact

What is contact?

• When two separate surfaces touch each other such that they become mutually tangent, they are said to be in contact.

• In the common physical sense, surfaces that are in contact have these characteristics:– They do not interpenetrate.

– They can transmit compressive normal forces and tangential friction forces.

– They often do not transmit tensile normal forces.

• They are therefore free to separate and move away from each other.

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Training Manual… Introduction to contact

• In this chapter, we will present an introduction to nonlinear contact analysis via the following topics:

A. Basic concepts

B. Using the contact wizard

C. Obtaining the solution

D. Postprocessing

E. Workshop

F. Assembly contact

• The purpose is to introduce you to contact analysis procedures for “simple” (easily converged) models. Other, more advanced aspects of contact analysis that are used to handle more difficult models are discussed in the Advanced Contact and Bolt Pretension training manual.

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Introduction to contact

A. Basic Concepts

• Contact is a changing-status nonlinearity. That is, the stiffness of the system depends on the contact status:

Status = Open Status = Closed and Sticking

Status = Closed and Sliding

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... Basic Concepts

• Contact is a strong nonlinearity, because both the normal and tangential stiffness at contact surfaces change significantly with changing contact status.– Large, sudden changes in stiffness often cause severe

convergence difficulties.

u

F

Open contact

Closed contact

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... Basic Concepts

• Other factors that make contact analysis complicated include:– The region of contact is typically unknown at the start of the

analysis.

– Most contact problems include friction.

• Friction is a path-dependent (energy-dissipating) phenomenon that requires an accurate load history, with small time steps.

• Frictional response can be chaotic, making solution convergence difficult.

– Parts might be unconstrained except for contact with other parts.

• Prior to establishment of contact, such parts are initially unconstrained free bodies, with zero overall stiffness.

– In a static analysis, unconstrained free bodies are mathematically unstable. The solution “blows up.”

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... Basic Concepts

• Fortunately, current ANSYS contact technology enables you to analyze a broad class of contact models fairly easily.– Many models can be solved successfully with very little user

intervention.

• For those models that exhibit more difficult convergence behavior, a rich library of contact element options are available to help you overcome such difficulties.– These more advanced features are discussed in the Advanced

Contact and Bolt Pretension training manual.

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... Basic Concepts

Contact classification

• Contact problems fall into two general classes: rigid-to-flexible and flexible-to-flexible.

• Rigid-to-flexible– One or more contacting surfaces are treated as rigid. (One

surface has a significantly higher stiffness than the other.) Many metal forming problems fall into this category.

– Stresses within the rigid body are not calculated.

• Flexible-to-flexible– Both or all contacting bodies are deformable. (All surfaces

have similar stiffnesses.) A bolted flange connection would be an example of flexible-to-flexible contact.

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... Basic Concepts

Rigid-to-flexible contact

Rigid Surface

Deformable Body

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... Basic Concepts

Flexible-to-flexible contact

Splined shaft interference fit, both parts are flexible.

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... Basic Concepts

Contact compatibility

• Physical contacting bodies do not interpenetrate. Therefore, the program must establish a relationship between the two surfaces to prevent them from passing through each other in the finite-element analysis.– When the program prevents interpenetration, we say that it

enforces contact compatibility.

F

TargetContact

Penetration occurs when contact compatibility is not enforced.

F

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... Basic Concepts

Contact compatibility – penalty method

• The penalty method of enforcing contact compatibility uses a contact “spring” to establish a relationship between the two surfaces.

– The spring stiffness is called the penalty parameter or, more commonly, the contact stiffness.

– The spring is inactive when the surfaces are apart (open status), and becomes active when the surfaces begin to interpenetrate (closed).

The spring will deflect an amount , such that equilibrium is satisfied:

F = k where k is the contact stiffness.

F

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... Basic Concepts

… contact compatibility – penalty method

• Some finite amount of penetration, , is required mathematically to generate a contact force at the interface.

– This contact force is needed for equilibrium.

– Thus, must be greater than zero for equilibrium.

• However, physical contacting bodies do not interpenetrate.

• Therefore, for best accuracy, the goal is to minimize the amount of penetration that occurs at the contact interface.

– Minimum penetration gives maximum accuracy.

– This implies that, ideally, the contact stiffness should have a very great value.

– However, too high of a value can lead to convergence difficulties.

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... Basic Concepts• If the contact stiffness is too great, a slight penetration will generate an excessive contact force, potentially throwing the contacting surfaces apart in the next iteration.

• Using too great a contact stiffness usually leads to oscillating convergence, and often to outright divergence.

Iteration n Iteration n+1

F

F

FcontactF

Iteration n+2

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... Basic Concepts

Contact compatibility – Lagrange multiplier method

• An alternative method, the Lagrange Multiplier method, adds an extra degree of freedom (contact pressure), to satisfy the impenetrability condition.

F

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... Basic Concepts

Contact compatibility – augmented Lagrangian method

• Most ANSYS contact elements can combine both the penalty method and the Lagrange multiplier to enforce contact compatibility. This is called the augmented Lagrangian method.

• In the first series of iterations, contact compatibility is determined based on the penalty stiffness. Once equilibrium is achieved, the penetration tolerance is checked. At this point, if necessary, the contact pressure is augmented and the iterations continue.

F

Penetration Tolerance

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... Basic Concepts

… contact compatibility – augmented Lagrangian method

Penetration correctiondue to equilibrium.

Oscillation occursduring correctionstage.

Augmentingcontact stresses to reduce penetration.

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... Basic Concepts

Surface-to-surface elements

• The most commonly used contact elements in ANSYS are the surface-to-surface elements.– Targe169 and 170

• Rigid or deformable target surfaces

– Conta171 to 174

• Deformable contact surfaces

• These elements are well suited for surface-to-surface contact applications such as interference fit assembly contact, entry contact, forging, and deep drawing.

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... Basic Concepts

… surface-to-surface elements

• These contact elements use the concept of a contact pair, which is composed of a target surface and a contact surface.– The surface-to-surface contact elements overlie the underlying

finite element model like a skin.

– Separate element types define the target and contact surfaces.

– The contact pair is identified through a shared real constant set.

Contact elements (REAL = N ) on the contact surface

Target elements (REAL = N ) on the target surface

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... Basic Concepts


• ANSYS supports both rigid-to-flexible and flexible-to-flexible surface-to-surface contact models.

• Flexible-to-flexible models have a deformable target surface, which is created whenever target elements overlie deformable elements.

• Rigid-to-flexible models have a rigid target surface, which does not overlie any deformable elements.

Rigid target element

Contact elements

Underlying mesh

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... Basic Concepts


• The surface-to-surface contact elements use the augmented Lagrangian to enforce contact compatibility (default). – Augmented Lagrangian uses both a contact stiffness and a

penetration tolerance.

• For “simple” contact models, you will normally need to specify just three characteristics of the contact pair:– A value for the contact stiffness

– A value for the penetration tolerance.

– You will also need to determine which surface in the pair should be the target, and which should be the contact.

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... Basic Concepts

Contact stiffness

• The contact stiffness is the most important parameter affecting both accuracy and convergence behavior.– Recall that greater stiffness gives better accuracy, but more

difficult convergence.

• You must carefully determine an appropriate value for contact stiffness.– The “best” value is often problem-dependent.

• Program-supplied default value may not be appropriate.

– Some experimentation may be required to determine an appropriate value that generates a converged solution with an acceptable level of accuracy.

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... Basic Concepts

… contact stiffness

• For the surface-to-surface elements, you specify the contact stiffness as a factor (FKN). That is, the program determines the contact stiffness by multiplying the stiffness of the underlying element times a factor that you specify.

kcontact = FKN x f(kunderlying)

• For the surface-to-surface elements, the contact stiffness has units of stiffness per unit area, or (F/L)/(L2).

• A good value for contact stiffness is often obtained by making the contact stiffness equal to the stiffness of the underlying elements.– As a starting estimate, try:

• FKN = 1.0 for bulky solids in contact.

• FKN = 0.1 for more flexible (bending-dominated) parts.

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... Basic Concepts


• Sometimes, different regions of a model may need to have different contact stiffnesses.

Bulky contact; try FKN = 1.0

Flexible contact; try FKN = 0.1

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... Basic Concepts


• You need to determine whether your results are sensitive to the contact stiffness.

• Choosing a good stiffness value may require some experimentation. The following procedure may be used as a guideline for static, non-path-dependent analyses:

1. Change the contact element option to allow the contact stiffness to be modified during restarts, KEYOPT(10)=1.

2. Use a “soft” FKN to start to help overcome convergence difficulties.

3. Run the analysis to the final load.

4. Check the results for some item of significance to your analysis (SEQV, contact pressure, etc.)

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... Basic Concepts


5. Increase FKN and restart the solution.

6. Check the results again.

7. Repeat steps 5 and 6 until the desired convergence is achieved.

SEQV

FKN

Look for a value of FKN beyond which the results don’t change significantly.

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... Basic Concepts


• As an example, FKN was varied for an interference-fit analysis of a collar on a shaft. Maximum equivalent von Mises stress was monitored.

• In this particular case, a value of FKN = 1.0 proved to give adequate accuracy.

FKN Max. SEQV0.001 4,0000.01 20,0000.1 65,0001 91,000

10 92,900100 93,000

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A. Contact stiffness … Workshop

Please refer to your Workshop Supplement for instructions on:

• W14. Introduction to Contact - Contact Stiffness Study (FKN)

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... Basic Concepts

Penetration tolerance

• The penetration tolerance also affects convergence and accuracy, although to a lesser extent than the contact stiffness.

– As the penetration tolerance is tightened, the accuracy may improve, but at the expense of more difficult convergence.

• As with the stiffness, you specify the penetration tolerance by means of a factor (FTOLN).

– The program determines the penetration tolerance by multiplying the depth of the underlying element (h) times a factor that you specify.

Tolerance = FTOLN x h

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... Basic Concepts

… penetration tolerance

• Don’t use a soft FKN and a tight FTOLN.

– Best convergence behavior is usually obtained if the contact stiffness does most of the work of enforcing compatibility.

• Use a reasonably stiff value for FKN.

• “Fine-tune” the penetration with a reasonable value of FTOLN.

• Too small a value for FTOLN will lead to convergence difficulty. Never use too small of a tolerance! Increasing the penalty stiffness (FKN) will reduce the penetration.

• Although increasing FKN by 100 times will usually reduce the penetration accordingly, other items of significance, such as the contact pressure, might change by as little 5%.

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A. Penetration tolerance … Workshop


• W15. Introduction to Contact - Penetration Tolerance Study (FTOLN)

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... Basic Concepts

Designating contact and target surfaces

• The program defines the contact surface by a set of discrete contact points (the element Gauss points).

• The program defines the target surface as a continuous surface.

• The two surfaces can interpenetrate between the Gauss points, without contact being recognized. This causes inaccuracies.

Target Surface

Contact Surface

The target can penetrate the contact surface in between the Gauss points.

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... Basic Concepts

… designating contact and target surfaces

• You can reduce the amount of unrecognized interpenetration by careful designation of the target and contact surfaces.

• However, for rigid-to-flexible contact, the choice of target and contact is unchangeable. The rigid surface must always be the target.

Steel shaft (rigid) must be the target surface

Rubber boot (flexible) must be the contact surface

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• For flexible-to-flexible contact, best accuracy is achieved by maximizing the number of contact points. Follow these guidelines when designating flexible-to-flexible contact and target surfaces:

– If one surface has a coarse mesh and the other a fine mesh, the surface with the coarse mesh should be the target surface.

• Consider what would happen if the designations were reversed:


... Basic Concepts

xxxxIf the finer mesh were the target, it would “droop” across the Gauss points, and penetrate as shown.

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... Basic Concepts


• Other guidelines for designating contact and target surfaces:

– If a convex surface comes into contact with a flat or concave surface, the flat or concave surface should be the target surface.

– If one surface is stiffer than the other, the stiffer surface should be the target surface.

– If one surface is higher order and the other is lower order, the lower order surface should be the target surface.

– If one surface is larger than the other, the larger surface should be the target surface.

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... Basic Concepts


• When all contact elements are on one surface and all target elements are on another surface, the model is said to have asymmetric contact.

– Asymmetric contact is generally the most efficient way to model surface-to-surface contact.

– However, under some circumstances asymmetric contact will not perform satisfactorily.

• No clear distinction exists between target and contact surfaces.

• Both target and contact surface have coarse meshes.

Sometimes the target-contact distinction is not clear

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... Basic Concepts


• An alternative approach is to create a double set of contact pairs. This is known as symmetric contact.

• After creating one contact pair, simply create a second contact pair having a reversed target-contact designation, for the same surfaces.

Contact

Target

Target

Contact

Step 1 - Create 1st Contact Pair

Step 2 - Create 2nd (Symmetric) Contact Pair

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... Basic Concepts


• Although some models may require symmetric contact for accuracy, be aware that it is less efficient than asymmetric contact. – Therefore, don’t use symmetric contact unless it is required.

• Note also, that when using symmetric contact, postprocessing is more difficult. – The contact pressure is the average value from both sets of

contact elements.

– This average value is not automatically available as a standard results item. You will need to calculate it using APDL or ETABLE.

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A. Contact & target … Workshop


• W16. Introduction to Contact - Contact & Target Designation

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... Basic Concepts

Rigid target surfaces – pilot node

• By default, the program will automatically constrain a rigid target surface. That is, it will automatically ground the target with zero-value displacements and rotations.

• To model more complicated behavior of the rigid target, you can create a special one-node target element, called a pilot node. – This element is associated with the target surface by means of

having the same REAL attribute.

• The pilot node acts as a handle for the entire rigid surface. – You can specify nonzero displacements, rotations, forces,

and/or moments at the pilot node to model rigid-body motion of the target surface.

– Note that if a pilot node exists, the program will not auto-constrain the rigid surface.

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... Basic Concepts

… pilot node

• The pilot node can be specified at any location. This allows for general rotations of the rigid target surface.

• Only the pilot node can connect to other elements. For example, to account for the mass of a rigid body, define a mass element (MASS21) at the pilot node.

• Each target surface can have only one pilot node.

Rigid surface rotated

Pilot node (at center of rotation)

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B. Using the contact wizard

• Surface-to-surface contact elements can be created using standard element-generation procedures: establish element TYPE, REAL, and MAT data, set element attributes, designate target and contact surfaces, and then either mesh or use ESURF operations.

• This procedure forces you to carry a fairly heavy “mental overhead” as you create your contact pairs.

• Fortunately, there is a better way ...

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... Using the contact wizard

• The contact wizard provides a simple way to construct a contact pair for most contact problems. The contact wizard will guide you through the process of creating a contact pair.

Preprocessor > Create > Contact Pair > Contact Wizard

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• Benefits of the Contact Wizard:– Automatically defines element types and real constant sets

– Quickly accesses the contact options and parameters

– Contact pair viewing tools

– Quickly displays and reverses contact normals

• The Contact Wizard is not available until you have meshed some portion of your model. – Before launching the wizard to create a flexible-to-flexible model,

mesh all parts of the model that will be used as contact surfaces.

– To create a rigid-to-flexible model, mesh only the parts of the model that will be used as flexible contact surfaces.

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• Let’s see how we could add a contact pair to the connector model from the Chapter 6 workshops.

First, designate rigid or flexible target type (if a choice is applicable), and pick the target surface. You can pick nodes, node components, lines, or areas, depending on what entities are present in the model.

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Next, pick the contact surface. Again, you can pick nodes, node components, lines, or areas, depending on what entities are present in the model.

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• By clicking on the Optional settings button, specifications for general contact behavior, convergence tools, friction effects, target constraints, thermal interface parameters and other miscellaneous parameters can be accessed.

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• Last, click on Create to create the contact and target elements that comprise this contact pair.

The REAL constant set used for this pair is identified.

The elements in the pair are automatically plotted, with their ESYS symbols ON to indicate outward normal directions. If any normals are pointing in the wrong direction, you can flip them now.

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• At any time after a contact pair is created, you can use the wizard to view and list the elements.



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• You can also use the wizard to edit all real and material constants associated with contact pairs.



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• Alternatively, REAL and Material constants can still be edited

thru the traditional Preprocessor GUI or via the R,,, and MP,,,

commands. See the command manual for details.

Or R,,,

Or MP,,,

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• You can also use the wizard to delete a contact pair.

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• Surface to surface contact elements offer three DOF options:

– Structural only: UX, UY, and UZ

– Structural and Thermal: UX, UY, UZ, and TEMP

– Thermal only: TEMP (for a pure thermal contact problems)

• When contact pairs are created via the wizard, the contact element DOF option is automatically set based on the DOF of the underlying elements. No adjustment is necessary.

• Surface to surface contact element DOFs can also be set via: – Main Menu > Preprocessor > Element Type > Add/Edit/Delete …



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• Basic Tab

– Contains all general parameters related to contact behavior and convergence.

Specifies whether parameter is a scalar factor of the default value or a constant

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• Friction Tab

Contains all parameters related to static and dynamic friction at the contact interface; also allows for the definition of a maximum friction stress at the contact interface.

MU = MUK*(1+(FACT-1)exp(-dc*VREL)

Where:

MU = coefficient of frictionMUK = dynamic coefficient of frictionVREL = relative slipping rate between

the two contacting surfaces

FACT = ratio of static to dynamic COEFF.dc = exponential decay ratio

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Additional note about friction

• The surface-to-surface elements provide a basic Coulomb

friction model that defines the equivalent friction stress at

which sliding occurs: = x p

– is the coefficient of friction, defined as a material property, as shown in the contact wizard on the previous slide.

• If equals zero (default), no shear stress will be transmitted.

– p is the contact pressure.

• When the shear stress between the two surfaces exceeds

x p, the two surfaces will slide relative to each other.

• The more advanced friction options are also available. They are discussed in the Advanced Contact and Bolt Pretension training manual.

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Training ManualContact Wizard Enhancements

• Initial Adjustment TABContains advanced penetration and surface offset parameters

(Discussed in fuller detail in the Advanced Contact and Bolt Pretension Training Course)

• Initial Adjustment TABContains advanced penetration and surface offset parameters

(Discussed in fuller detail in the Advanced Contact and Bolt Pretension Training Course)

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• MISC TABFeatures for Spurious contact prevention,Beam/Shell Thickness effect and location of contact detection point, gauss or node (Discussed in fuller detail in the Advanced Contact and Bolt Pretension Training Course)

• MISC TABFeatures for Spurious contact prevention,Beam/Shell Thickness effect and location of contact detection point, gauss or node (Discussed in fuller detail in the Advanced Contact and Bolt Pretension Training Course)

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• Rigid target TABFor specifying constraints and higher order target element option (Discussed in fuller detail in the Advanced

Contact and Bolt Pretension Training Course)

• Rigid target TABFor specifying constraints and higher order target element option (Discussed in fuller detail in the Advanced

Contact and Bolt Pretension Training Course)

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• Thermal Tab All thermal contact parameters, including contact conductancenear field surface radiation, frictional heating factors (Discussed in fuller detail in the Advanced Contact and Bolt Pretension Training)

• Thermal Tab All thermal contact parameters, including contact conductancenear field surface radiation, frictional heating factors (Discussed in fuller detail in the Advanced Contact and Bolt Pretension Training)

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Pilot node

• Rigid target surfaces can be associated with a “pilot node” whose motion governs the motion of the target surface. Forces, displacements and/or rotations for the entire surface can be specified on the pilot node. You can think of the pilot node as a handle for the entire rigid surface.

• If you define a pilot node, ANSYS checks for boundary conditions only on the pilot node and ignores the constraints on the other nodes of the target surface.

• The pilot node can be generated either by meshing a keypoint, or by direct generation using the same element attributes as the target elements.

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Pilot node (cont’d)• The contact wizard does not enable you to create a pilot node

for a rigid target surface. To create a pilot node, you will have to use meshing or direct generation:– First, set the element attributes (MAT, REAL, TYPE) for the target

elements.• Remember to use the same REAL set as for the rest of the

contact pair.– Then mesh a keypoint that is located at the desired position for

the pilot node.• Recall that the pilot node can be at any location – it is not

required to be physically attached to the other target elements.

– Alternatively, for direct generation, set an additional attribute for the target-element shape (TSHAP,PILO) and then create the element at the desired node.

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C. Obtaining the solution

• Automatic solution control, along with the default option settings for surface-to-surface elements, generally leads to fairly robust solutions for a broad class of contact analyses.

• If convergence difficulties are encountered, they generally arise due to one or more of three causes: – Too great a value for contact stiffness.

– Too tight a value for penetration tolerance.

– Too large a value for minimum time step size.

• To improve convergence, try these modifications to your model, in the following order of implementation:– Use a smaller FKN.

– Use a larger FTOLN.

– Use a smaller minimum time step size (or larger maximum number of substeps).

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... Obtaining the solution

• If your model still won’t converge with modified FKN, FTOLN, and time step size, then the advanced contact options will probably be needed. – These are discussed in the Advanced Contact and Bolt

Pretension training manual.

• If your model includes friction, small time step sizes are required for accuracy, because friction is a path-dependent phenomenon.– Unlike plasticity, there is no cutback control that will trigger

bisection if a friction time step is too large.

• Note that in a contact solution, all equilibrium iterations are carried out before bisection for the first substep, to help establish initial contact conditions.

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D. Postprocessing

• Results from contact models will contain many additional items related to contact. Some of the more commonly used items include:STAT Contact Status

PENE Penetration

GAP Gap

PRES Contact Pressure

SFRI Friction Stress

• These items are associated with the contact element (not the target element), and can be readily accessed in the GUI.– Using the General Postprocessor, you can display them in Nodal

(averaged) or Element (unaveraged) contour plots.

• Animated plots are especially helpful for contact analyses.

– Using the Time-History Postprocessor, you can plot them as time-history variables.

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... Postprocessing

• The contact status is an integer number that designates the current status of the contact element:

– STAT = 0: Open and not near contact.

– STAT = 1: Open, but near contact.

– STAT = 2: Closed and sliding.

– STAT = 3: Closed and sticking.

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... Postprocessing

• Note that a Nodal (averaged) contour plot of status will exhibit non-integer contour values, due to the averaging. Element (unaveraged) contour plots are usually more appropriate for contour plots of element status.

• Similarly, anomalous Nodal contour plots can occur for other contact results items. If a Nodal (averaged) contour plot doesn’t seem to make sense, try an Element (unaveraged) plot instead.

Contact RegionStatus >1 in

nodal contour plot

Status = 1 in element

contour plot

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... Postprocessing

• The penetration or gap distance represents the actual amount of penetration (for STAT = 2 or 3) or open gap (for STAT = 1), in consistent units of length.– In listings, penetration distance is positive, and gap distance is

negative.

– Because contour plots display either penetration or gap (not both simultaneously), the contours always display as positive values for both items.

• The contact pressure (PRES) and friction stress values (SFRI) represent the current values for the contact element, copied from the Gauss points to the nodes.

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E. Workshop


• W17. Introduction to Contact - Snap-fit

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F. Assembly contact

• Many analysts now import solid models from CAD packages, and then mesh and analyze the imported models in ANSYS.

• For most CAD programs, a single volume, however complex, represents a single part. Multiple-volume models will have several parts associated together in an assembly.

Part B

Part A

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... Assembly contact

• The boundaries between parts within an assembly usually represent mathematical discontinuities within the CAD model.– When meshed in ANSYS, there will be a discontinuity in the

mesh at these part boundaries. Nodes on one side of the boundary will not “talk” with nodes on the other side of the boundary.

• Surface-to-surface contact elements can be used to connect the mesh across part boundaries, using a concept known as assembly contact.

Glue parts A & B together using assembly contact

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• Although assembly contact uses advanced contact features to glue parts together, the procedure is straightforward and very consistent for different models.– In fact, ANSYS Inc.’s designer-level product, DesignSpace,

includes automated assembly-contact procedures. It has been used successfully by designers who have no concept of nonlinear analysis procedures.

• Because assembly contact is widely applicable, and is usually “simple” (i.e., having robust convergence behavior), we will present the procedure here, with little explanation of the advanced features being used.

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• The CAD assembly must have these characteristics:

– The parts must “touch” each other along a boundary.

– The boundary surfaces need not match perfectly; some mathematical “noise” in the geometry is tolerable.

– The two adjacent parts must be meshed before an assembly contact pair can be generated.

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• As a tool for gluing interfacing boundaries together, assembly contact is more generally applicable than NUMMRG, EINTF, CPINTF, CEINTF, and other such tools that have been used in the past.– It is valid in large-displacement analyses (unlike coupling and

constraint equations).

– It can connect mismatched meshes (unlike NUMMRG and EINTF).

• Assembly contact takes advantage of the bonded contact feature of the surface-to-surface contact elements to glue disconnected parts together.

• To model a stronger bond, a very stiff value of FKN is often used.– It is not unusual to use FKN = 10.

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• The key to assembly contact is the creation of an initially “perfect” contacting surface having no initial forces acting across the contact interface.

– This is achieved by using the Bonded (always) contact surface behavior along with the Exclude everything initial-penetration option under the optional settings:

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• If the only nonlinearity in your model is assembly contact, you can sometimes turn nonlinear iterations off in your analysis.

Solution > Unabridged Menu > -Load Step Opts- Solution Ctrl…

Solution >Unabridged Menu >-Load Step Opts- Nonlinear >Equilibrium Iter

• However, realize that turning off nonlinear iterations could produce a model that is not in perfect equilibrium.

Turn automatic solution control OFF

Specify ONE equilibrium iteration

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• A model that has parts glued together with assembly contact can be used in many types of analyses, including: – Nonlinear static.

– Nonlinear transient dynamic.

– Linear modal.

– Linear eigenvalue buckling.

• The initial status of the contact elements is “frozen” in a linear analysis (such as modal or eigenvalue buckling analysis).

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F. Assembly contact … Workshop


• W18. Introduction to Contact - Assembly Contact

introduction to contact chapter seven. training manual october 15, 2001 inventory # 001565 7-2 7....

Documents

contact surfaces

advanced contact

region of contact

establishment of contact

contact wizardc

nonlinear contact analysis

changing contact status

broad class of contact