分析教案成果cont-l02workflow

1、Lesson content:Defining Contact PairsDefining Surfaces for Contact PairsDefining General ContactWorkshop PreliminariesWorkshop 1: Compression of a Rubber Seal (IA)Workshop 1: Compression of a Rubber Seal (KW)Lesson 2: Contact Workflow90 minutesBoth interactive (IA) and keywords (KW) versions of the

2、workshop are provided. Complete only one.Defining Contact Pairs (1/12)Features of contact pairs:Contact between pairs of surfaces is explicitly defined. The user definesWhat constitutes each surface.Which pairs of surfaces will interact.Which surface is the master, and which is the slave.Which surfa

3、ce interaction properties are relevant (e.g., friction)The contact pair algorithm has certain restrictions on the types of surfaces involved.Discussed later.The input requires more work on the part of the user than general contact.Must define surfacesInteractions are defined on a pair-wise basisDefi

4、ning Contact Pairs (2/12)Example: Analysis of a jounce bumperA jounce bumper is a highly compressible component that is used as part of the shock isolation system in a vehicle. The analysis consists of two steps:Step-1 Interference fit between the bumper and the shaft.Step-2 Move the bottom plate up

5、 to compress the bumper.The bumper is expected to fold as it is compressed, so self-contact must be defined.Consider first using contact pairs.shaftaxis of symmetrytop platebottom platebumperDefining Contact Pairs (3/12)Example (contd): Define surfaces (using keywords)Automatic free surface generati

6、on on bumper elements: *SURFACE,NAME=BUMPER-EXT BUMPER,Discrete rigid surfaces: *RIGID BODY, ELSET=BOTDIE, REF NODE=BOTRP*SURFACE,NAME=BOTPLATE BOTDIE, SPOS*RIGID BODY, ELSET=TOPDIE, REF NODE=TOPRP *SURFACE, NAME=TOPPLATE TOPDIE, SPOS *RIGID BODY, ELSET=SHAFTDIE, REF NODE=SHAFTRP *SURFACE, NAME=SHAF

7、T SHAFTDIE, SPOS 1Element set BUMPERSurface BUMPER-EXTSurface SHAFTSurface BOTPLATESurface TOPPLATEDefining Contact Pairs (4/12)Example (contd): Define surfaces (using Abaqus/CAE)Model TreeCreate discrete rigid partDouble-click Surfaces to create a new surface.1SHAFTTOPPLATEBUMPER-EXTBOTPLATEDefinin

8、g Contact Pairs (5/12)Example (contd): Define contact propertiesContact property definitions are the same for general contact and contact pairs.Contact properties may include:friction, contact damping, and pressure-overclosure relationships. In the jounce bumper example, all contact pairs use the sa

9、me interaction property: *SURFACE INTERACTION, NAME=Friction*FRICTION0.05, 2Defining Contact Pairs (6/12)Example (contd): Define contact pairsA contact pair definition is required for each pair of surfaces that can interact.Bumper self-contact:*CONTACT PAIR, INTERACTION=FRICTION BUMPER-EXT,3BUMPER-E

10、XTSHAFTBOTPLATETOPPLATEDefining Contact Pairs (7/12)Example (contd): Define contact pairsContact between the bumper and the rigid bodies:*CONTACT PAIR, INTERACTION=FRICTION BUMPER-EXT, TOPPLATE BUMPER-EXT, BOTPLATE BUMPER-EXT, SHAFT3BUMPER-EXTSHAFTBOTPLATETOPPLATEDefining Contact Pairs (8/12)Example

11、 (contd): SummarySteps to define contact pairs:Define surfaces based on the underlying elements or geometry.Define surface interaction properties: friction, softened layers, etc.Define pairs of surfaces that can interact.Results:123final deformed shapeundeformed shapeDefining Contact Pairs (9/12)3D

12、contact pairs: Automatic contact detectionAutomatic contact detection is a fast and easy way to define contact pairs and tie constraints in a three-dimensional model. Instead of individually selecting surfaces and defining the interactions between them, you can instruct Abaqus/CAE to automatically l

13、ocate all surfaces in a model that are likely to interact based on initial proximity.Can be used to define contact with shells, membranes and solidsIncluding shell offsetNative or orphan mesh partsDefining Contact Pairs (10/12)Example: Disk brakeA tabular display of possible contact pairs is provide

14、dShortcuts; e.g., manually add contact pairs to the groupDefining Contact Pairs (11/12)Table operations and rules editor Edit multiple cellsCustomize the tabular displayOther table operations Modify rules applied to new contact pairsDefining Contact Pairs (12/12)Non-overlapping surfacesCan include o

15、r filter outDistance is within search toleranceBut surface normals do not intersect the opposing surface (nonoverlapping)No contact pairs detectedTwo contact pairs detectedDefining Surfaces for Contact Pairs (1/10)Two approaches are available for surface definition:Specify the faces of each part ins

16、tance (or element/element set for orphan meshes) that may come in contact (as shown earlier).Allow Abaqus to determine the “free surfaces” that may come into contact automatically.Only available through the keywords interface (i.e., when editing an input file).Defining Surfaces for Contact Pairs (2/

17、10)User-specified contact faces: Abaqus/CAE interfaceSolid bodiesThe surface on a solid is defined by selecting the appropriate region of the exterior of the part.Regions may be selected individually or based on face angles.Defining Surfaces for Contact Pairs (3/10)User-specified contact faces: Abaq

18、us/CAE interface (contd) Shells and beamsThe surface on a shell/membrane or beam/truss is defined by choosing the appropriate side of the part.Double-sided shell/membrane surfaces are allowed for surface-to-surface formulation. See Lecture 3.Defining Surfaces for Contact Pairs (4/10)User-specified c

19、ontact faces: Keywords interfaceUse face identifiers to specify each element face forming the surface.Example: 4-node quad element (CPE4, CAX4, etc.).*SURFACE, NAME=EXAMPLE1, S41, S12, S12, S2.Either element set names or element numbers can be used to specify surfaces.Sequence of elements is not imp

20、ortantDefining Surfaces for Contact Pairs (5/10)User-specified contact faces: Keywords interface (contd)Structural element normals dictate the direction of expected contact:Node numbering dictates the positive normal direction (based on the right-hand rule).Positive normal direction = SPOS surface.N

21、egative normal direction = SNEG surface.Omit surface identifier to define a double-sided surface (shells and membranes only)Shells and membranes (S4R,S8R,M3D4,etc.)2-D trusses and beams (B21,T2D2,etc.)Defining Surfaces for Contact Pairs (6/10)Automatic or free surface generation (Keywords interface

22、only)Surfaces can be generated automatically for meshes containing solid, continuum shell, and cohesive elements.Automatic surface generation is only available through the keywords interface (i.e., when editing an input file).Syntax: Omit face identifiers from the surface definition.*SURFACE, NAME=E

23、XAMPLEELSET1,ELSET2,100,Defining Surfaces for Contact Pairs (7/10)General rules for surface definitionsAll elements underlying a surface must be compatible. They must be: Of the same dimension (two- or three-dimensional).For two-dimensional surfaces: all planar or all axisymmetric (but not both).Of

24、the same order of interpolation (first- or second-order).All deformable or all rigid (but not both).Defining Surfaces for Contact Pairs (8/10)Additional restrictionsSurface normals Surface normals must be consistentBeam, shell, and membrane surfaces can be flipped to create a valid surface definitio

25、n for contactMaster surface normals should point toward the slave surface.Otherwise, convergence difficulties will occur.Rigid surfaces All surfaces defined on rigid bodies must be specified as master surfaces.*SURFACE, NAME=SURFBOTTOM, SPOSTOP, SNEG*SURFACE, NAME=SURFBEAMS, SPOSDefining Surfaces fo

26、r Contact Pairs (9/10)Additional restrictions apply to contact surfaces depending on the type of contact formulation.These are summarized in the following table:T-intersectionSurface connected at one nodecontinuous surfacesContact formulationConnectivity characteristics(Yes=allowed, No=not allowed)D

27、iscontinuous(or 3D faces joined at only one node)T-intersectionFinite-sliding, node-to-surfaceMaster: NoSlave: YesMaster: NoSlave: YesSmall-sliding, node-to-surfaceMaster: YesSlave: YesMaster: NoSlave: YesFinite-sliding, surface-to-surfaceMaster: YesSlave: YesMaster: YesSlave: YesSmall-sliding, surf

28、ace-to-surfaceMaster: YesSlave: YesMaster: NoSlave: YesDefining Surfaces for Contact Pairs (10/10)Node-based surfacesAlternative way to define points for contact. Node-based surfaces:Contain only nodes. Are always considered slave surfaces.Preclude the use of the surface-to-surface discretization. S

29、trings: node-based surfaceBall: element-based surfacePrompt when choosing a slave surface in Abaqus/CAE; choose the nodes involved in contact (set or directly in viewport)*SURFACE, TYPE=NODE, NAME=STRINGSSTRINGS,*CONTACT PAIR, INTERACTION=SMOOTHSTRINGS, BALLpreviously defined surfaceDefining General

30、 Contact (1/13)The user interface allows for a concise contact definition reflecting the physical description of the problem.The contact definition can be expanded in complexity, as appropriate.Independent specification of the contact interaction domain, contact properties, and surface attributes is

31、 permitted.Minimal algorithmic controls are required.Defining General Contact (2/13)Master-slave roles are assigned automaticallyPrimarily based on mesh refinementInternal, component surfaces ranked by suitability as masterOverall general contact surfaceDefining General Contact (3/13)Example: Analys

32、is of a jounce bumperA jounce bumper is a highly compressible component that is used as part of the shock isolation system in a vehicle. The analysis consists of two steps:Step-1 Interference fit between the bumper and the shaft.Step-2 Move the bottom plate up to compress the bumper.We now consider

33、this problem using general contact.Discrete rigid bodies are used since analytical rigid surfaces are not currently supported by general contactshaftaxis of symmetrytop platebottom platebumperDefining General Contact (4/13)Example: Analysis of a jounce bumperThe contact interaction is defined as fol

34、lows:1) Begin the general contact definition. *Contact *Contact Inclusions, ALL EXTERIOR2) Accept the default contact domain.3) Assign global contact properties *Contact Property Assignment , , FRICTIONDefining General Contact (5/13)The contact definition can gradually e more detailed, as called for

35、 by the analysisGlobal/local friction coefficients and other contact properties can be defined.Pair-wise specification of contact domain (instead of ALL EXTERIOR) is allowed.Contact inclusions and exclusionsUser control of contact thickness (especially for shells) is provided.Surface propertiesConta

36、ct initialization (initial adjustments, interference fits, etc.)Defining General Contact (6/13)To enhance a general contact definition, you often need to define specific contact surfaces.Surfaces can span unattached bodies.Surfaces can include both deformable and rigid regions.Surfaces can have mixe

37、d parent element types.Adjacent shell and solid faces, etc.More than two faces can share a common edge.Allows direct modeling of T-intersections, etc.Element set BUMPERSurface BUMPER-EXTSurface SHAFTSurface BOTPLATESurface TOPPLATEDefining General Contact (7/13)In Abaqus/CAE surfaces can be created

38、at the part level or the assembly level.Surfaces defined on a part are available in the assembly for each instance of the part.Boolean operations can be performed on surfaces to generate other surfaces using the Model Tree.In the input file, surfaces are defined with the *SURFACE keyword option. Boo

39、lean operations can be performed on surfaces to generate other surfaces using the parameter:COMBINE=UNION | INTERSECTION | DIFFERENCE.*Surface, name=surf_contact, combine=DIFFERENCEelset_main, elset_no_contact Select surfaces in the Model Tree and click mouse button 3.Defining General Contact (8/13)

40、Example: Nondefault contact domainFor some models the default ALL EXTERIOR surface is not appropriate or not sufficient. The general contact domain can be modified by including and/or excluding predefined surfaces.In the jounce bumper model, a safeguard against contact between the rigid bodies can b

41、e introduced using contact exclusionsSurface BUMPER-EXTSurface SHAFTSurface BOTPLATESurface TOPPLATENote that in this example this step is not required since the normals between the shaft and the plates remain perpendicular (contact will not be detected).Defining General Contact (9/13)Example: Nonde

42、fault contact domainKeywords interface:*Contact*Contact Inclusions, ALL EXTERIOR*Contact ExclusionsTOPPLATE , SHAFTTOPPLATE , BOTPLATESHAFT , BOTPLATE*Contact Property Assignment , , FRICTIONSurface BUMPER-EXTSurface SHAFTSurface BOTPLATESurface TOPPLATEDefining General Contact (10/13)Example: Conta

43、ct initializationThe default behavior of general contact is to adjust small initial overclosures without strain. Can treat instead as interference fits.Surface BUMPER-EXTSurface SHAFTDefining General Contact (11/13)Example: Contact initializationKeywords interface:*Contact Initialization Data, name=

44、Fit-1, INTERFERENCE FIT*Contact*Contact Inclusions, ALL EXTERIOR*Contact Property Assignment , , FRICTION*Contact initialization Assignment BUMPER-EXT, SHAFT, Fit-1Surface BUMPER-EXTSurface SHAFTDefining General Contact (12/13)Nondefault contact properties may be used to enhance contact modeling.Con

45、tact properties may include:Contact pressure-overclosure relationshipFrictionContact dampingThe defaults are: A “hard” pressure-overclosure relationship no contact pressure until nodes are in contact unlimited contact pressure once contact has been establishedNo frictionNo contact dampingDefining Ge

46、neral Contact (13/13)Example: Multiple contact propertiesBolted flange assemblyCoefficient of friction m = 0.1 for all contact interactions except for those involving the gasket (m = 0.4).*Contact Property Assignment , , Friction-0p1 , gasketAll, Friction-0p4ObjectivesWhen you complete this exercise

47、 you will be able to extract all the files necessary to complete the demonstrations and workshops associated with this courseWorkshop file setup (option 1: installation via plug-in)From the main menu bar, select Plug-insTools Install Courses.In the Install Courses dialog box:Specify the directory to which the files will be written.Chooses the course(s) for which the files will be extracted.Click OK.Workshop Preliminaries (1/2)5 minutesWorkshop file setup (option 2: manual i