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Contact Technology Guide ANSYS, Inc Southpointe 275 Technology Drive Canonsburg, PA 15317 ansysinfo@ansys.com http://www.ansys.com (T) 724-746-3304 (F) 724-514-9494 Release 12.1 November 2009 ANSYS, Inc is certified to ISO 9001:2008 Copyright and Trademark Information © 2009 SAS IP, Inc All rights reserved Unauthorized use, distribution or duplication is prohibited ANSYS, ANSYS Workbench, Ansoft, AUTODYN, EKM, Engineering Knowledge Manager, CFX, FLUENT, HFSS and any and all ANSYS, Inc brand, product, service and feature names, logos and slogans are registered trademarks or trademarks of ANSYS, Inc or its subsidiaries in the United States or other countries ICEM CFD is a trademark used by ANSYS, Inc under license CFX is a trademark of Sony Corporation in Japan All other brand, product, service and feature names or trademarks are the property of their respective owners Disclaimer Notice THIS ANSYS SOFTWARE PRODUCT AND PROGRAM DOCUMENTATION INCLUDE TRADE SECRETS AND ARE CONFIDENTIAL AND PROPRIETARY PRODUCTS OF ANSYS, INC., ITS SUBSIDIARIES, OR LICENSORS The software products and documentation are furnished by ANSYS, Inc., its subsidiaries, or affiliates under a software license agreement that contains provisions concerning non-disclosure, copying, length and nature of use, compliance with exporting laws, warranties, disclaimers, limitations of liability, and remedies, and other provisions The software products and documentation may be used, disclosed, transferred, or copied only in accordance with the terms and conditions of that software license agreement ANSYS, Inc is certified to ISO 9001:2008 U.S Government Rights For U.S Government users, except as specifically granted by the ANSYS, Inc software license agreement, the use, duplication, or disclosure by the United States Government is subject to restrictions stated in the ANSYS, Inc software license agreement and FAR 12.212 (for non-DOD licenses) Third-Party Software See the legal information in the product help files for the complete Legal Notice for ANSYS proprietary software and third-party software If you are unable to access the Legal Notice, please contact ANSYS, Inc Published in the U.S.A Table of Contents Contact Overview 1.1 General Contact Classification 1.2 ANSYS Contact Capabilities 1.2.1 Surface-to-Surface Contact Elements 1.2.2 Node-to-Surface Contact Elements 1.2.3 3-D Line-to-Line Contact 1.2.4 Line-to-Surface Contact 1.2.5 Node-to-Node Contact Elements GUI Aids for Contact Analyses 2.1 The Contact Manager 2.2 The Contact Wizard 2.3 Managing Contact Pairs Surface-to-Surface Contact 11 3.1 Using Surface-to-Surface Contact Elements 11 3.2 Steps in a Contact Analysis 11 3.3 Creating the Model Geometry and Mesh 12 3.4 Identifying Contact Pairs 12 3.5 Designating Contact and Target Surfaces 13 3.5.1 Asymmetric Contact vs Symmetric Contact 14 3.5.1.1 Background 14 3.5.1.2 Using KEYOPT(8) 14 3.6 Defining the Target Surface 15 3.6.1 Pilot Nodes 15 3.6.2 Primitives 15 3.6.3 Element Types and Real Constants 15 3.6.3.1 Defining Target Element Geometry 15 3.6.4 Using Direct Generation to Create Rigid Target Elements 16 3.6.5 Using ANSYS Meshing Tools to Create Rigid Target Elements 17 3.6.5.1 Some Modeling and Meshing Tips 20 3.6.5.2 Verifying Nodal Number Ordering (Contact Direction) of Target Surface 20 3.7 Defining the Deformable Contact Surface 21 3.7.1 Element Type 22 3.7.2 Real Constants and Material Properties 23 3.7.3 Generating Contact Elements 23 3.8 Set the Real Constants and Element KEYOPTS 24 3.8.1 Real Constants 25 3.8.1.1 Positive and Negative Real Constant Values 27 3.8.2 Element KEYOPTS 28 3.8.3 Selecting a Contact Algorithm (KEYOPT(2)) 30 3.8.3.1 Background 30 3.8.4 Determining Contact Stiffness and Allowable Penetration 31 3.8.4.1 Background 31 3.8.4.2 Using FKN and FTOLN 32 3.8.4.3 Using FKT and SLTO 32 3.8.4.4 Using KEYOPT(10) 33 3.8.4.5 Using KEYOPT(6) 34 3.8.4.6 Chattering Control Parameters 34 3.8.5 Choosing a Friction Model 35 3.8.5.1 Background 35 3.8.5.2 Coefficient of Friction 36 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates iii Contact Technology Guide 3.8.5.3 Using TAUMAX, FACT, DC, and COHE 36 3.8.5.4 Static and Dynamic Friction Coefficients 37 3.8.5.5 Forced Frictional Sliding Using Velocity Input 38 3.8.5.6 User-defined Friction 39 3.8.6 Selecting Location of Contact Detection 39 3.8.6.1 Background 39 3.8.6.2 Using KEYOPT(4) and TOLS 39 3.8.7 Adjusting Initial Contact Conditions 41 3.8.7.1 Background 41 3.8.7.2 Using PMIN, PMAX, CNOF, ICONT, KEYOPT(5), and KEYOPT(9) 41 3.8.8 Physically Moving Contact Nodes Towards the Target Surface 47 3.8.9 Determining Contact Status and the Pinball Region 48 3.8.9.1 Background 48 3.8.9.2 Using PINB 49 3.8.10 Avoiding Spurious Contact in Self Contact Problems 49 3.8.11 Selecting Surface Interaction Models 50 3.8.11.1 Background 50 3.8.11.2 Using KEYOPT(12) 50 3.8.11.3 Using FKOP 51 3.8.11.4 Bonded Contact for Shell-Shell Assemblies 52 3.8.12 Modeling Contact with Superelements 53 3.8.12.1 Background 53 3.8.12.2 Using KEYOPT(3) 53 3.8.13 Accounting for Thickness Effect 54 3.8.13.1 Background 54 3.8.13.2 Using KEYOPT(11) 54 3.8.14 Using Time Step Control and Impact Constraints 54 3.8.14.1 Background 54 3.8.14.2 Using KEYOPT(7) 54 3.8.15 Using the Birth and Death Option 55 3.9 Controlling the Motion of the Rigid Target Surface 55 3.10 Applying Necessary Boundary Conditions to the Deformable Elements 56 3.11 Applying Fluid Pressure-Penetration Loads 56 3.11.1 Applying Fluid Penetration Pressure 57 3.11.2 Specifying Fluid Penetration Starting Points 58 3.11.3 Specifying a Pressure-Penetration Criterion 59 3.11.4 Specifying a Fluid Penetration Acting Time 60 3.11.5 Redefining or Modifying the Pressure-Penetration Loads 62 3.11.6 Postprocessing Fluid Pressure-Penetration Loads 62 3.12 Defining Solution and Load Step Options 63 3.13 Solving the Problem 64 3.14 Reviewing the Results 65 3.14.1 Points to Remember 65 3.14.2 Reviewing Results in POST1 65 3.14.3 Reviewing Results in POST26 67 Node-to-Surface Contact 69 4.1 The Node-to-Surface Contact Element 69 4.2 Performing a Node-to-Surface Contact Analysis 70 4.2.1 CONTA175 KEYOPTS 70 4.2.1.1 KEYOPT(3) 70 4.2.1.2 KEYOPT(4) 71 4.2.2 CONTA175 Real Constants 71 iv Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates Contact Technology Guide 4.3 Using CONTA175 for Multiphysics Contact 71 3-D Beam-to-Beam Contact 73 5.1 The 3-D Line-to-Line Contact Element 73 5.2 Modeling Beam-to-Beam Contact 74 5.3 Performing a 3-D Beam-to-Beam Contact Analysis 75 5.3.1 KEYOPTs and Real Constants 76 5.3.1.1 Real Constants R1, R2 76 5.3.1.2 KEYOPT(3) 77 5.3.1.3 Real Constants FKN and FKT 77 5.3.1.4 Real Constant TOLS 77 5.3.1.5 KEYOPT(4) 78 Line-to-Surface Contact 79 6.1 The 3-D Line-to-Surface Contact Element 79 6.2 Performing a 3-D Line-to-Surface Contact Analysis 80 6.2.1 KEYOPTs and Real Constants 80 6.2.1.1 Real Constants FKN and FKT 81 6.2.1.2 Accounting for Thickness Effect (CNOF and KEYOPT(11)) 81 6.2.1.3 Real Constant TOLS 81 6.2.1.4 KEYOPT(4) 81 Multiphysics Contact 83 7.1 Modeling Thermal Contact 83 7.1.1 Thermal Contact Behavior vs Contact Status 83 7.1.2 Free Thermal Surface 84 7.1.3 Temperature on Target Surface 84 7.1.4 Modeling Conduction 84 7.1.4.1 Using TCC 84 7.1.4.2 Using the Quasi Solver Option 85 7.1.5 Modeling Convection 85 7.1.6 Modeling Radiation 85 7.1.6.1 Background 85 7.1.6.2 Using SBCT and RDVF 86 7.1.7 Modeling Heat Generation Due to Friction 86 7.1.7.1 Background 86 7.1.7.2 Using FHTG and FWGT 87 7.1.8 Modeling External Heat Flux 87 7.2 Modeling Electric Contact 87 7.2.1 Modeling Surface Interaction 88 7.2.1.1 Background 88 7.2.1.2 Using ECC 88 7.2.2 Modeling Heat Generation Due to Electric Current 88 7.3 Modeling Magnetic Contact 89 7.3.1 Using MCC 90 7.3.2 Modeling Perfect Magnetic Contact 90 Node-to-Node Contact 91 8.1 Node-to-Node Contact Elements 91 8.2 Performing a Node-to-Node Contact Analysis 92 8.2.1 Creating Geometry and Meshing the Model 92 8.2.2 Generating Contact Elements 92 8.2.2.1 Generating Contact Elements Automatically at Coincident Nodes 92 8.2.2.2 Generating Contact Elements Automatically at Offset Nodes 93 8.2.2.3 Node Ordering 93 8.2.3 Defining the Contact Normal 93 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates v Contact Technology Guide 8.2.4 Defining the Initial Interference or Gap 95 8.2.5 Selecting the Contact Algorithm 95 8.2.6 Applying Necessary Boundary Conditions 95 8.2.7 Defining the Solution Options 96 8.2.8 Solving the Problem 97 8.2.9 Reviewing the Results 97 Multipoint Constraints and Assemblies 99 9.1 Modeling Solid-Solid and Shell-Shell Assemblies 100 9.2 Modeling a Shell-Solid Assembly 102 9.3 Surface-Based Constraints 106 9.3.1 Defining Surface-Based Constraints 108 9.3.2 Defining Influence Range (PINB) 109 9.3.3 Degrees of Freedom of Surface-Based Constraints 109 9.3.4 Specifying a Local Coordinate System 110 9.3.5 Additional Guidelines for a Force-Distributed Constraint 111 9.3.6 Additional Guidelines for A Rigid Surface Constraint 111 9.3.7 Modeling a Beam-Solid Assembly 111 9.4 Modeling Rigid Bodies 112 9.4.1 Modeling Contact between Rigid Bodies 113 9.5 Overconstraint Detection and Elimination 113 9.6 Restrictions and Recommendations for Internal MPC 114 10 Dynamic Contact and Impact Modeling 117 10.1 Energy and Momentum Conserving Contact 117 10.1.1 Energy Conservation 118 10.1.2 Automatic Time Stepping 118 10.1.3 Penetration and Relative Velocity 118 11 Spot Welds 119 11.1 Defining a Spot Weld Set 120 11.1.1 Creating a Basic Spot Weld Set with SWGEN 120 11.1.2 The Components of a Spot Weld 124 11.1.3 Adding Surfaces to a Basic Set 126 11.2 Listing and Deleting Spot Welds 129 12 Debonding 131 12.1 Including Debonding in a Contact Analysis 131 12.1.1 Cohesive Zone Materials Used for Debonding 132 12.1.1.1 Bilinear Material Behavior with Tractions and Separation Distances (TBOPT = CBDD) 132 12.1.1.2 Bilinear Material Behavior with Tractions and Critical Fracture Energies (TBOPT = CBDE) 132 12.1.2 Debonding Modes 133 12.1.3 Other Considerations for Debonding 133 12.1.4 Postprocessing 133 A Example 2-D Contact Analysis with Fluid Pressure-Penetration Loading 135 A.1 Problem Description 135 A.2 Input File 138 Index 143 List of Figures 2.1 Contact Manager Toolbar 2.2 Example of a Contact Wizard Dialog 3.1 Localized Contact Zones 13 vi Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates Contact Technology Guide 3.2 ANSYS Geometric Entities and Their Corresponding Rigid Target Elements 18 3.3 A Single Circular Target Segment Created From Arc Line Segments 18 3.4 Meshing Patterns for Arbitrary Target Surfaces 19 3.5 Smoothing Convex Corner 20 3.6 Correct Node Ordering 20 3.7 Contact Element Types 22 3.8 Specification of the Contact Surface's Outward Normal 24 3.9 Depth of the Underlying Element 28 3.10 Sliding Contact Resistance 36 3.11 Friction Decay 38 3.12 Contact Detection Located at Gauss Point 39 3.13 Contact Detection Point Location at Nodal Point 40 3.14 Node Slippage Using Nodal Integration KEYOPT(4) = or 40 3.15 Contact Surface Adjustment With ICONT 43 3.16 Contact Surface Adjustment (PMIN, PMAX) 44 3.17 A Scenario in Which Initial Adjustment Will Fail 44 3.18 Ignoring Initial Penetration, KEYOPT(9) = 46 3.19 Components of True Penetration 46 3.20 Ramping Initial Interference 47 3.21 Effect of Moving Contact Nodes 48 3.22 Auto Spurious Prevention 50 3.23 Penalty-Based Shell-Shell Assembly 52 3.24 Path Dependent Fluid Penetration Loading 57 3.25 Free End Points (2-D) and Free Open Edges (3-D) 59 3.26 Fluid Penetration Acting Time (FPAT) Greater Than Substep 61 3.27 Fluid Penetration Acting Time (FPAT) Less Than Substep 62 4.1 Node-to-Surface Contact Elements 69 5.1 Line-to-Line Contact Elements 73 5.2 Internal Contact (One Beam Sliding Inside Another) 74 5.3 External Contact (Two Beams Roughly Parallel) 74 5.4 External Contact (Two Beams Cross Each Other) 75 5.5 Continuous Line Segments 76 5.6 Equivalent Circular Cross Section 77 6.1 Line-to-Surface Contact Elements 79 6.2 Continuous Line Segments 80 7.1 Target Temperature 84 8.1 Node-to-Node Contact Elements 91 8.2 Contact Between Two Concentric Pipes 93 8.3.Two Concentric Pipes, Normals Rotated Properly 94 8.4 Example of Overconstrained Contact Problem 96 9.1 Example of Shell-Solid Assembly 102 9.2 Shell-Solid Assembly (Original Mesh) 103 9.3 Shell-Solid Assembly with Solid-Solid Constraint Option 104 9.4 Shell-Solid Assembly with Shell-Shell Constraint Option 104 9.5 Shell-Solid Assembly with Shell-Solid Constraint Option 105 9.6 Shell-Solid Constraint - No Intersection (use KEYOPT(5) = or 5) 106 9.7 Rigid Surface Constraint 107 9.8 Force-Distributed Constraint 108 9.9 Slider Link 110 9.10 Free Radial Expansion Under Torque Load 111 9.11 Beam-Solid Assembly Defined by Rigid Surface Constraint 112 9.12 Beam-Solid Assembly Defined by Force-distributed Constraint 112 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates vii Contact Technology Guide 11.1 Example Spot Weld Configuration 119 11.2 Default Projection Direction for Node 121 11.3 Default Projection Direction for Nodes and 122 11.4 User-specified Projection Direction, Node 122 11.5 User-specified Projection Direction, Nodes and 123 11.6 Search Radius for Spot Weld 124 11.7 Nodes Included in Constraint Equations 125 11.8 Beam Element Created for Spot Weld 125 11.9 Surfaces Added to Basic Spot Weld Set 127 11.10 Node Reordering for Beam Elements 128 A.1 Diagram of Planar Seal Model 135 A.2 Meshed Planar Seal Model 136 A.3 Fluid Pressure Loading on Planar Seal 136 A.4 Intermediate Fluid Pressure Distribution 137 A.5 Final Fluid Pressure Distribution 137 A.6 Time History of Fluid Pressure for Three Contact Elements 138 List of Tables 1.1 ANSYS Contact Capabilities 3.1 Summary of Real Constant Defaults in Different Environments 26 3.2 Summary of KEYOPT Defaults in Different Environments 29 viii Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates Chapter 1: Contact Overview Contact problems are highly nonlinear and require significant computer resources to solve It is important that you understand the physics of the problem and take the time to set up your model to run as efficiently as possible Contact problems present two significant difficulties First, you generally not know the regions of contact until you've run the problem Depending on the loads, material, boundary conditions, and other factors, surfaces can come into and go out of contact with each other in a largely unpredictable and abrupt manner Second, most contact problems need to account for friction There are several friction laws and models to choose from, and all are nonlinear Frictional response can be chaotic, making solution convergence difficult In addition to these two difficulties, many contact problems must also address multi-field effects, such as the conductance of heat, electrical currents, and magnetic flux in the areas of contact If you not need to account for friction in your model, and the interaction between the bodies is always bonded, you may be able to use the internal multipoint constraint (MPC) feature (available for certain contact elements) to model various types of contact assemblies and surface-based constraints (see Chapter 9, Multipoint Constraints and Assemblies (p 99) for more information) Another alternative is to use constraint equations or coupled degrees of freedom instead of contact to model these situations (see "Coupling and Constraint Equations" in the Modeling and Meshing Guide for more information) The external constraint equations or coupling equations are only suitable for small strain applications In addition to the implicit contact capabilities discussed in this guide, ANSYS also offers explicit contact capabilities with the ANSYS LS-DYNA explicit dynamics product Explicit capabilities are ideally suited for short-duration contact-impact problems For more information on the ANSYS LS-DYNA product and its contact capabilities, see the ANSYS LS-DYNA User's Guide 1.1 General Contact Classification Contact problems fall into two general classes: rigid-to-flexible and flexible-to-flexible In rigid-to-flexible contact problems, one or more of the contacting surfaces are treated as rigid (i.e., it has a much higher stiffness relative to the deformable body it contacts) In general, any time a soft material comes in contact with a hard material, the problem may be assumed to be rigid-to-flexible Many metal forming problems fall into this category The other class, flexible-to-flexible, is the more common type In this case, both (or all) contacting bodies are deformable (i.e., have similar stiffnesses) An example of a flexible-to-flexible contact is bolted flanges Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates Chapter 1: Contact Overview 1.2 ANSYS Contact Capabilities ANSYS supports five contact models: node-to-node, node-to-surface, surface-to-surface, line-to-line, and lineto-surface Each type of model uses a different set of ANSYS contact elements and is appropriate for specific types of problems as shown in the table below Table 1.1 ANSYS Contact Capabilities Node-to-Node Contact Element No Nodeto- Surface 52 LinetoLine Lineto- Surface 175 171, 172 173, 174 176 177 169, 170 169 170 170 170 Y Y Y Y 12 Surface-to-Surface Y Y Y Y Y small small large large large large large 178 Target Element No 2-D Y 3-D Sliding Cylindrical Gap small Y Y Pure Lagrange Multiplier Y Y Y Y Y Y Augmented Lagrange Multiplier Y Y Y Y Y Y Lagrange Multiplier on Normal and Penalty on Tangent Y Y Y Y Y Y Y Y Y Y Y semiauto semiauto semiauto semiauto semiauto Internal Multipoint Constraint (MPC) Contact Stiffness userusersemidefined defined auto Auto-meshing Tools EINTF EINTF EINTF ESURF ESURF ESURF ESURF ESURF Y Y Y Y Y Y Y Y Y (2-D only) Y Y Y Y Lower-Order Higher-Order Rigid-Flexible Y Y Y Y Y Y Y Y Flexible-Flexible Y Y Y Y Y Y Y Y Y Y Y Thermal Contact Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates 130 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates Chapter 12: Debonding The debonding capability in ANSYS refers specifically to separation of bonded contact It can be used to simulate interface delamination where the interface is modeled using bonded contact with the augmented Lagrangian method or the pure penalty method A cohesive zone material must be used to define the traction separation behavior of the interface The following contact elements support debonding: CONTA171, CONTA172, CONTA173, CONTA174, CONTA175, CONTA176, and CONTA177 An alternative method of modeling interface delamination is to use interface elements with a cohesive zone material (see "Interface Delamination and Failure Simulation") However, debonding with contact elements has the following advantages over delamination with the interface elements: • Parts forming the interface can be meshed independently • Existing models with contact definitions can be easily modified for debonding • Standard contact and debonding can be simulated with the same contact definitions • Debonding can be used for various applications; for example, delamination, spot weld failure, and stitch failure 12.1 Including Debonding in a Contact Analysis Debonding can be defined in any model that includes surface-to-surface (CONTA171 through CONTA174), node-to-surface (CONTA175), line-to-line (CONTA176), or line-to-surface (CONTA177) contact For a detailed discussion on how to set up a contact analysis, see Chapter 3, Surface-to-Surface Contact (p 11) To activate debonding for a contact pair, the following contact options must be defined for the contact element: • Augmented Lagrangian method or pure penalty method (KEYOPT(2) = or 1) • Bonded contact (KEYOPT(12) = 2, 3, 4, 5, or 6) In addition, you must specify a cohesive zone material model with bilinear behavior for the contact elements Two ways to specify the material data are available: • Bilinear material behavior with tractions and separation distances (TB,CZM command with TBOPT = CBDD) • Bilinear material behavior with tractions and critical fracture energies (TB,CZM command with TBOPT = CBDE) This material model is discussed in more detail in the following section Once you have defined the required input parameters, you can solve the analysis the same as you would for any nonlinear analysis (see Solving the Problem (p 64)) After debonding is completed, the surface interaction is governed by standard contact constraints for normal and tangential directions Frictional contact is used if friction is specified for contact elements Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates 131 Chapter 12: Debonding 12.1.1 Cohesive Zone Materials Used for Debonding A cohesive zone material model is needed to model debonding in a contact analysis This material is defined using the data table method (TB and TBDATA commands) Temperature dependent data is also allowed (TBTEMP command) On the TB command, use Lab = CZM to denote a cohesive zone material, and use TBOPT = CBDD or CBDE to indicate the specific material data you will provide The two data definitions are described below For more information on this material, see Cohesive Zone Material Model in the Theory Reference for the Mechanical APDL and Mechanical Applications 12.1.1.1 Bilinear Material Behavior with Tractions and Separation Distances (TBOPT = CBDD) This is a linear elastic material behavior with linear softening characterized by maximum traction and maximum separation To define this material, use the TB,CZM command with TBOPT = CBDD Specify the material constants as data items C1 through C6 on the TBDATA command: Constant Symbol Meaning C1 σmax C2 c un contact gap at the completion of debonding C3 τmax maximum equivalent tangential contact stress C4 uc t tangential slip at the completion of debonding C5 η artificial damping coefficient C6 β flag for tangential slip under compressive normal contact stress maximum normal contact stress Sample command input for this material is shown below TB,CZM,1,2,,CBDD TBDATA,1, max, c un , max, uc t , , 12.1.1.2 Bilinear Material Behavior with Tractions and Critical Fracture Energies (TBOPT = CBDE) This is a linear elastic material behavior with linear softening characterized by maximum traction and critical energy release rate To define this material, use the TB,CZM command with TBOPT = CBDE Specify the material constants as data items C1, through C6 on the TBDATA command: Constant Symbol C1 σmax maximum normal contact stress C2 Gcn critical fracture energy for normal separation C3 τmax maximum equivalent tangential contact stress C4 Gct C5 η artificial damping coefficient C6 β flag for tangential slip under compressive normal contact stress 132 Meaning critical fracture energy for tangential slip Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates 12.1.4 Postprocessing Sample command input for this material is shown below TB,CZM,1,2,,CBDE TBDATA,1, max,Gcn, max,Gct, , 12.1.2 Debonding Modes Debonding involves separation of surfaces forming an interface The direction of separation determines the debonding mode ANSYS detects the debonding mode based on material data that you input for normal and tangential directions: • Mode I debonding involves separation normal to the interface It is activated by inputting data items C1, C2, and C5 on the TBDATA command • Mode II debonding involves slip tangent to the interface It is activated by inputting data items C3, C4, and C5 on the TBDATA command • Mixed mode debonding involves both normal separation and tangential slip It is activated by inputting data items C1, C2, C3, C4, and C5, and C6 on the TBDATA command 12.1.3 Other Considerations for Debonding Artificial Damping Debonding is generally accompanied by convergence difficulties in the Newton-Raphson solution Artificial damping can be used to stabilize the numerical solution It is activated by specifying the damping coefficient η (input on TBDATA command as C5 using TB,CZM) The damping coefficient has units of time and should be smaller than the minimum time step size so that the maximum traction and maximum separation (or critical fracture energy) values are not exceeded in debonding calculations Tangential Slip under Normal Compression ANSYS provides an option to control tangential slip under compressive normal contact stress for mixed mode debonding By default, no tangential slip is allowed for this case, but it can be activated by setting the flag β to (input on TBDATA command as C6 using TB,CZM) Pinball Radius and Mesh Density When using a fine mesh for underlying elements of bonded surfaces, you may need to increase pinball radius (PINB) for contact elements so that it is greater than the maximum separation value in the normal direction (contact gap when normal contact stress goes to zero) The default value for PINB is based on the depth of the underlying element If PINB is smaller than the maximum separation value, debonding calculations will be bypassed when the contact gap exceeds PINB 12.1.4 Postprocessing All applicable output quantities for contact elements are also available for debonding: normal contact stress (PRES), tangential contact stress (TAUR, TAUS, SFRIC), contact gap (GAP), tangential slip (TASR, TASS, SLIDE), etc In addition, the following debonding specific output quantities are available as NMISC data: debonding time history (DTSTART), debonding parameter (DPARAM), and critical fracture energy (DENERI, DENERII) For more information on how to review results in a contact analysis, see Reviewing the Results (p 65) in Chapter 3, Surface-to-Surface Contact (p 11) Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates 133 134 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates Appendix A Example 2-D Contact Analysis with Fluid Pressure-Penetration Loading This example represents a planar seal compression with applied fluid pressure-penetration loading at the contact interface It demonstrates the application of the fluid pressure loads and the propagation of the fluid penetration path from one starting point into the contact interface A.1 Problem Description The model represents a half symmetry planar hyperelastic seal Figure A.1: Diagram of Planar Seal Model (p 135) shows a diagram of the model, and Figure A.2: Meshed Planar Seal Model (p 136) shows the meshed half symmetry model Figure A.1: Diagram of Planar Seal Model 0.865 inches applied displacement 1/2 symmetry Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates 135 Appendix A Example 2-D Contact Analysis with Fluid Pressure-Penetration Loading Figure A.2: Meshed Planar Seal Model The seal is compressed by a displacement-controlled load in the first load step Fluid pressure is applied to all contact elements in the second load step (see Figure A.3: Fluid Pressure Loading on Planar Seal (p 136)) so that the fluid opens and penetrates into the contact interface that was previously closed by compression The fluid pressure is applied using the SFE command with the load key set to (LKEY = on SFE) Using SFE with the load key set to (LKEY = on SFE), all default starting points are suppressed (STA1 = -1) and two elements are chosen as starting locations initially exposed to the fluid (STA1 = 1) (See Specifying Fluid Penetration Starting Points (p 58) for more information on the STA values.) From this location the fluid penetrates gradually by opening the bottom part of the contact surface, while the top part of the contact surface completely closes Figure A.3: Fluid Pressure Loading on Planar Seal At the end of the first load step (compression load step) most of the contact is closed as shown in the above figure Plots of contact fluid pressure at an intermediate substep of load step and at the end of load step are shown in Figure A.4: Intermediate Fluid Pressure Distribution (p 137) and Figure A.5: Final Fluid Pressure Distribution (p 137) 136 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates A.1 Problem Description Figure A.4: Intermediate Fluid Pressure Distribution Figure A.5: Final Fluid Pressure Distribution Three contact elements at the bottom of the seal are used for time history postprocessing, representing each region that undergoes fluid penetration Time history results for fluid contact pressure and gap are printed and plotted to show the path of fluid penetration along the bottom contact elements The fluid pressure history is shown in Figure A.6: Time History of Fluid Pressure for Three Contact Elements (p 138) Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates 137 Appendix A Example 2-D Contact Analysis with Fluid Pressure-Penetration Loading Figure A.6: Time History of Fluid Pressure for Three Contact Elements A.2 Input File /title,Seal compression with fluid pressure-penetration loading /com ===================================================================== /com OBJECTIVE: /com The objective of this test is to verify the path of fluid /com penetration pressure with rigid-flex contact /com and CONTA171 default keyoptions /com /com DESCRIPTION: /com The model represents a planar seal that is compressed Fluid /com pressure is applied to all contact elements so that the fluid /com penetrates and opens the contact that used to be closed by /com compression /com /com The fluid pressure is applied after the compression, and one /com starting point is chosen to be initially in fluid (STA=1 on SFE) /com From this location the fluid penetrates gradually at the bottom /com surface /com /com TEST SPECIFICATIONS: /com SOLID ELEMENTS: PLANE182 - PLANE STRESS /com TARGET ELEMENT: TARGE169 /com CONTACT ELEMENT: CONTA171, K(14)=0, K(2)=0, K(4)=0 /com MATERIAL MODEL: HYPERELASTIC /com /com /com RESULTS: /com At the end of load step there are regions where contact is /com closed at the bottom surface One element from each of these /com regions is chosen, and the time history results for fluid /com contact pressure and gap are printed and plotted to show the /com path of fluid penetration along the bottom contact elements /com Notice that at the time when the contact opens /com (gap is not zero), the FPRS is nonzero /com ===================================================================== /prep7 138 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates A.2 Input File et,1,182 ! PLANE182 with plane stress option tb,HYPER,1,1,2,MOON tbtemp,0 tbdata,,80,20,0,,, /com **** Build the model **** k,1 k,2,0.333,0 k,3,0.867,0.867 k,4,1.1,0.867 k,5,1.1,1 k,6,0.8,1 k,7,0.267,0.133 k,8,0,0.133 l,1,2 *repeat,7,1,1 l,8,1 lfillt,1,2,0.20 lfillt,2,3,0.15 lfillt,5,6,0.20 lfillt,6,7,0.15 lfillt,7,8,0.05 lfillt,8,1,0.05 al,all k,98,-1.0,0 k,99,1.1,0 lstr,99,98 k,100,-1.0,1.0 k,101,1.1,1.0 lstr,100,101 lcomb,8,13 lcomb,8,14 esize,0.02 type,1 mat,1 smrtsize,5 amesh,all allsel lsel,s,,,4 nsll,s,1 d,all,ux,0 allsel /com ! Set element attributes and meshing parameters ! Mesh the model ! BCs to model half symmetry **** Contact pair creation **** et,2,169 et,3,171 keyopt,3,10,2 mp,mu,2,0.2 ! Friction r,2 /com **** Top and bottom rigid targets **** type,2 real,2 mat,2 lesize,15,,,1 lesize,16,,,1 lmesh,15,16 /com **** Contact on the planar seal **** lsel,s,line,,1,12 lsel,u,line,,4 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates 139 Appendix A Example 2-D Contact Analysis with Fluid Pressure-Penetration Loading nsll,s,1 type,3 esurf allsel,all finish /solu allsel esel,s,ename,,169 nsle nsel,r,loc,y,1 d,all,uy,-0.865 ! Move top rigid target nlgeom,on time,1 nsubst,25,2000,5 outres,all,all allsel nropt,unsym ! Unsymmetric due to friction solve esel,s,ename,,171 ! Select only contact elements sfe,all,1,PRES, ,150 ! Apply fluid pressure of 150 to all contact elements sfe,all,2,pres,,-1 ! Suppress default starting points (STA1 = -1) nsel,s,loc,x ! Select a location for starting points esln esel,r,ename,,171 ! Reselect only the contact elements sfe,all,2,pres,,1 ! Specify the above location to be initially in fluid (STA1 = 1] allsel nsubst,100,1000,10 solve finish /com **** Post1 postprocessing **** /post1 /show set,2,last finish /com **** Post26 time history postprocessing **** /post26 timerange,1,2 esol,2,523,138 ,cont,fprs,CONTFPRS1 esol,3,523,138 ,cont,gap,CONTGAP1 /com ***************************************************************************** /com History of contact gap and fluid pressure for an element in the /com region that opens first /com ***************************************************************************** prvar,2,3 esol,4,578,53 ,cont,fprs,CONTFPRS2 esol,5,578,53 ,cont,gap,CONTGAP2 /com **************************************************************************** /com History of contact gap and fluid pressure for an element in the /com region that opens later /com ***************************************************************************** prvar,4,5 esol,6,517,6,cont,fprs,CONTFPRS3 esol,7,517,6,cont,gap,CONTGAP3 /com **************************************************************************** /com History of contact gap and fluid pressure for contact element /com that opens last /com ***************************************************************************** prvar,6,7 140 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates A.2 Input File /title,Time history of fluid pressure for three contact elements /axlab,y,Fluid pressure plvar,2,4,6 finish Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates 141 142 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates Index B beam-to-beam contact, 73 C contact analysis, asymmetric vs symmetric contact, 14 beam-to-beam, 2, 73 birth and death option, 55 boundary conditions for node-to-node contact, 95 boundary conditions for surface-to-surface contact, 56 chattering controls, 30 choosing surfaces, 13 conduction, 84 contact algorithm, 30, 95 contact direction, 20 contact location detection, 39 Contact Manager, 7, 11 contact pairs, 9, 12 contact status, 48, 83 contact stiffness, 30–31 contact surface elements, Contact Wizard, convection, 85 debonding, 131 deformable contact surface, 21 direct generation to create rigid target elements, 16 electric contact, 87 electrostatic elements, 87 emissivity, 85 explicit dynamics, flexible-to-flexible, 1, 11 fluid pressure-penetration loads for surface-to-surface contact, 56 free surface convection, 84 free surface radiation, 84 free thermal surface, 84 friction model, 35 gap, 95 Gauss integration points, 39 generating node-to-node contact elements, 92 generating surface-to-surface contact elements, 23 heat flux, 84, 87 heat generation due to electric current, 88 heat generation due to friction, 86 initial contact conditions, 41 initial interference, 95 internal MPC, 99 line-to-line, line-to-surface, 79 localized contact zone, 20 magnetic contact, 89 moving contact nodes, 47 node ordering in node-to-node analysis, 93 node-to-node, 2, 4, 91 node-to-surface, 2, 4, 69 node-to-surface KEYOPTS, 70 node-to-surface real constants, 71 normals, 7, 20, 23, 93 open far-field contact status, 48 open near-field contact status, 48 overall steps, 11 overconstrained contact problem, 95 penalty stiffness, 23 penetration, 30 piezoelectric elements, 87 pinball region, 48 point-to-point, point-to-surface, radiation, 85 results, 65 rigid-to-flexible, 1, 11, 55 self contact, 14, 49 shells, 54 sliding contact status, 48 slippage, 39 solution options for node-to-node contact, 96 solution options for surface-to-surface contact, 63 solving, 64 spurious contact, 49 Stefan-Boltzmann constant, 85 sticking contact status, 48 summary of contact capabilities, superelements, 53 surface interaction for electric contact, 88 surface interaction models, 50 surface-to-surface, 2–3, 11, 22 surface-to-surface KEYOPTS, 28 surface-to-surface material properties, 23 surface-to-surface real constants, 23–24 symmetric/unsymmetric solver, 35 target element shapes, 16 target surface definition, 15 target surface element types and real constants, 15 target surface modeling and meshing tips, 20 target surface nodal number ordering, 20 target surface pilot node, 15, 55 target surface primitives, 15 temperature required, 84 thermal contact, 83 thickness effect, 54 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates 143 Index time step control, 54 using meshing tools to create rigid target elements, 17 D debonding, 131 delamination in a contact analysis, 131 F fluid pressure-penetration loads, 56 I internal MPC, 99 L line-to-surface contact, 79 M magnetic analysis contact, 89 multipoint constraint, 99 P penalty stiffness in contact analysis, 23 pilot node in contact analysis, 15, 55 S spot welds, 119 144 Release 12.1 - © 2009 SAS IP, Inc All rights reserved - Contains proprietary and confidential information of ANSYS, Inc and its subsidiaries and affiliates ... available: 2.1.The Contact Manager 2.2.The Contact Wizard 2.3 Managing Contact Pairs 2.1 The Contact Manager You can access the Contact Manager via the Contact Manager icon in the ANSYS Standard... short-duration contact- impact problems For more information on the ANSYS LS-DYNA product and its contact capabilities, see the ANSYS LS-DYNA User''s Guide 1.1 General Contact Classification Contact problems... and confidential information of ANSYS, Inc and its subsidiaries and affiliates Chapter 1: Contact Overview 1.2 ANSYS Contact Capabilities ANSYS supports five contact models: node-to-node, node-to-surface,