講義說明分析cont

1、Lesson content:General ConsiderationsSurface-based ContactContact ExamplesIngredients of a Contact ModelLesson 1: Introduction30 minutesGeneral Considerations (1/2)What is contact? Physically, contact stress is transmitted between two solid bodies when they touch.In some cases only normal stress is

2、transmitted.If friction is present, a limited amount of shear stress can also be transmitted.Numerically, contact is a severely discontinuous form of nonlinearity.Either a constraint is applied or it is ignored. The general objective of a numerical analysis is to determine contacting areas and stres

3、s transmitted.General Considerations (2/2)Contact problems can generally be divided into two broad classes: Continuum vs. Structural ContactContinuum contact (bulky components)Typically, many nodes in contact at one timeContact causes local deformation and shear, but it causes little bendingStructur

4、al contact (slender components)Typically, few nodes in contact at one timeContact causes bendingOften more challengingSurface-based Contact (1/5)Abaqus/Standard offers both surface-based and element-based approaches to modeling contactSurface-based contact offers greater flexibility and ease-of-use

5、and will therefore be the focus of this course.Element-based contact is discussed in Appendix 2.Contact elements: Reinforced medical tubing*Surface-based contact: Expansion of a stent in an artery*The medical tubing problem can be modeled using both contact elements and surface-based contactSurface-

6、based Contact (2/5)Abaqus/Standard 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

7、disconnected regions of a model. Contact pairs describe contact between two surfaces.Requires more careful definition of contact.Every possible contact pair interaction must be defined.Has many restrictions on the types of surfaces involved.One contact domain in general contactMultiple contact pairs

8、 requiredSurface-based Contact (3/5)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 surfaceThe method is geared toward models with multiple components and complex topologyGrea

9、ter ease in defining contact modelSurface-based Contact (4/5)The contact pair algorithm Requires user-specified pairing of individual surfacesOften results in more efficient analyses since contact surfaces are limited in scopeSlave surfaces for contact pair analysisSurface-based Contact (5/5)The cho

10、ice between general contact and contact pairs is largely a trade-off between ease of defining contact and analysis performanceRobustness and accuracy of both methods are similarIn some cases, the contact pair approach is required in order to access specific features not currently available with gene

11、ral contact. These include:Analytical rigid surfacesNode-based surfacesSmall slidingRough frictionLagrange frictionSee the Abaqus Analysis Users Guide for a complete list of general contact limitationsThe two contact algorithms, however, can be used together in the same analysis.The general contact

12、algorithm automatically avoids processing interactions that are treated by the contact pair algorithm.Contact Examples (1/5)Types of contact Various factors influence a contact analysis, including:Deformable or rigid surfacesSlender or bulky componentsDegree of confinement and compressibility of com

13、ponentsTwo-surface contact or self contactFinite-sliding or small-sliding contact formulationInteraction properties (friction, thermal, etc.)The above factors include physical and numerical aspectsThe user is responsible for defining the physical aspects of a modelThe user and Abaqus control various

14、 numerical aspectsExamples representing different “classes” of contact problems followContact Examples (2/5)Contact between linear elastic bodies with small relative motion“Hertz” contactCommon design problem involving:Small displacementsContact over a distributed surface areaTypical examples:Bearin

15、g designHard gasketsInterference fitsFretting (surface wear) is often a concern, requiring accurate resolution of contact stresses and stick/slip zonesThis example is taken from “Coolant manifold cover gasketed joint,” Section 5.1.4 in the Abaqus Example Problems Guide.Contact Examples (3/5)Deformab

16、le to rigid body contactFinite sliding between the surfaces (large displacements).Finite strain of the deforming components.Typical examples: Rubber seals Tire on road Pipeline on seabed Forming simulations (rigid die/mold, deformable component).This example is taken from “Superplastic forming of a

17、rectangular box,” Section 1.3.2 in the Abaqus Example Problems Guide.Example: metal forming simulationContact Examples (4/5)Finite-sliding contact between deformable bodiesMost general category of contactExample: twisting blocksPress together and relative rotation of 90Contact Examples (5/5)Self-con

18、tact of a single bodyType of finite-sliding, deformable-to-deformable contactContact of a single body with itselfoften involves severe deformationSometimes adds CPU expense and numerical difficultyIf the surface spans multiple bodies, multi-body contact can be modeled with “self contact”This is the basis for general (or “automatic” ) contactContour of minimum principal stressSURF1 (rigid)SURF2Example: Compression of a rubber gasket (taken from “Self-contact in rubber/foam components: rubber gasket,” Example Problem 1.1.18 in the Abaqus Examp