Advanced Topics in ABAQUS Simulation

1、Reinforced ConcreteCompositesCohesiveSpringsContact Modeling in ABAQUSWeidong WuDepartment of Civil EngineeringThe University of Mississippi1In order to use ABAQUSFEA backgroundKnow what you will model Create your model correctlyAlways refer to the manual whenever you are not sureSolve difficulties

2、through .dat .msg .sta files2How to model compositesTwo ways: -Composite shell sections when your model is simple -Composites layup Real-world application, may handle large number of plies3 Composites Modeling4Composite shell sectionsComposed of layers made of different materials in different orient

3、ations. 5Define composite shell in CAE6Composites layupPly orientation The orientation of each ply 7Define composite layup in CAE8In PreparationHow to model RC9Cohesive Modeling10ApplicationsModeling adhesives, bonded interfaces, and gaskets Constitutive response types Continuum based A traction-sep

4、aration description of the interface A uniaxial stress state-gasket /small adhesive patches 11Creating a cohesive layer You should define the geometric region that represents the cohesive layer as a SOLID, even if the thickness of the layer is close to zero 12Creating a cohesive layerIf thickness is

5、 less than104 , specify it13Cohesive ElementsCOH2D4 COH3D6 COH3D8 8-node three-dimensional cohesive element 14Define InteractionCohesive zone should have more refined meshIn most applications it is appropriate to have both faces of the cohesive elements tied to neighboring components 15If you want t

6、o model the cohesive layer using a mesh that is finer than the adjacent bulk material mesh, the cohesive layer should be generated as a separate mesh and tied to the bulk material using tie constraints 16Continuum-based modeling A glue-like material has a finite thickness Using conventional material

7、 models When used with conventional material models, cohesive elements use true stress and strain measures The cohesive layer is subjected to only through-thickness strain, and two transverse shear strain components All standard output variables in ABAQUS are available for cohesive elements that are

8、 used with conventional material models * COHESIVE SECTION, RESPONSE=CONTINUUM Modeling of damage with cohesive elements can be carried out only in Abaqus/Explicit 17Modeling of damage with cohesive elements Progressive damage and failure for -Ductile metals -Fiber-reinforced composites18Traction-se

9、paration-based modeling The intermediate glue material is very thin and may be considered to be of zero thickness Model the delamination at interfaces in composites Cohesive behavior defined directly in terms of a traction-separation law t-The nominal traction stress vector k-is the stiffness that r

10、elates the nominal stress S to the displacement When used with a material model that is based on a traction-separation description, cohesive elements use nominal stress and strain measures *COHESIVE SECTION, RESPONSE=TRACTION SEPARATION 19A uniaxial stress state-gasket modelingFully nonlinear (can b

11、e used with finite strains and rotations);Can have mass in a dynamic analysisAvailable in both ABAQUS/Standard and ABAQUS/Explicit20Contact Modeling In Preparation21IntroductionSurface based or contact element basedInteraction between surfaces -Normal -Tangential: sliding frictionContact Property: t

12、o define contact interaction models: -Normal hard -Tangential: finite or small sliding22Master and slave surfaceOnly the master surface can penetrate the slave surface the slave surface should be the more finely meshed surfaceif the mesh densities are similar, the slave surface should be the surface

13、 with the softer underlying materialElement selectionit is better, in general, to use first-order elements for those parts of a model that will form a slave surface 23If you choose the Finite sliding formulation and the Surface to surface discretization method, the contact interaction property that

14、you select cannot specify a “hard” contact pressure-overclosure relationship 24What You May Always Need to Know25Job Execution ControlAbaqus Job suspend, resume, and terminate abaqus suspend | resume | terminate job=job-name abaqus terminate job=input_file26Automatic stabilization of unstable static

15、 problems Nonlinear static problems can be unstable Causes: geometrical nature, such as buckling, material nature, such as material softening Rigid body motion Solution: automatic addition of volume-proportional damping to the model to obtain a smooth motion27How to decide the damping factorAutomati

16、c stabilization of static problems with a constant damping factor 1. Based on the dissipated energy fraction,default 2. Directly specifying the damping factor 3. Propagating the damping factors from the immediately preceding general step into the current step 28Common DifficultiesWarning message: Zero