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Reinforced Concrete Composites Cohesive Springs Contact Modeling in ABAQUS

2. In order to use ABAQUS. FEA backgroundKnow what you will model Create your model correctlyAlways refer to the manual whenever you are not sureSolve difficulties through .dat .msg .sta files. 3. How to model composites. Two ways: -Composite shell sections when your

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Reinforced Concrete Composites Cohesive Springs Contact Modeling in ABAQUS

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    1. Reinforced Concrete Composites Cohesive Springs Contact Modeling in ABAQUS Weidong Wu Department of Civil Engineering The University of Mississippi

    2. 2 In order to use ABAQUS FEA background Know what you will model Create your model correctly Always refer to the manual whenever you are not sure Solve difficulties through .dat .msg .sta files

    3. 3 How to model composites Two ways: -Composite shell sections when your model is simple -Composites layup Real-world application, may handle large number of plies

    4. 4 Composites Modeling

    5. 5 Composite shell sections Composed of layers made of different materials in different orientations.

    6. 6 Define composite shell in CAE

    7. 7 Composites layup

    8. 8 Define composite layup in CAE

    9. 9 In Preparation… How to model RC

    10. 10 Cohesive Modeling

    11. 11 Applications Modeling adhesives, bonded interfaces, and gaskets Constitutive response types Continuum based A traction-separation description of the interface A uniaxial stress state-gasket /small adhesive patches

    12. 12 Creating a cohesive layer

    13. 13 Creating a cohesive layer

    14. 14 Cohesive Elements COH2D4 COH3D6 COH3D8 8-node three-dimensional cohesive element

    15. 15 Define Interaction Cohesive zone should have more refined mesh

    16. 16 If you want to 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

    17. 17 Continuum-based modeling A glue-like material has a finite thickness Using conventional material 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 used with conventional material models * COHESIVE SECTION, RESPONSE=CONTINUUM Modeling of damage with cohesive elements can be carried out only in Abaqus/Explicit

    18. 18 Modeling of damage with cohesive elements Progressive damage and failure for -Ductile metals -Fiber-reinforced composites

    19. 19 Traction-separation-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 relates 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

    20. 20 A uniaxial stress state-gasket modeling Fully nonlinear (can be used with finite strains and rotations); Can have mass in a dynamic analysis Available in both ABAQUS/Standard and ABAQUS/Explicit

    21. 21 Contact Modeling In Preparation…

    22. 22 Introduction Surface based or contact element based Interaction between surfaces -Normal -Tangential: sliding friction Contact Property: to define contact interaction models: -Normal hard -Tangential: finite or small sliding

    23. 23 Master and slave surface Only the master surface can penetrate the slave surface the slave surface should be the more finely meshed surface if the mesh densities are similar, the slave surface should be the surface with the softer underlying material Element selection it is better, in general, to use first-order elements for those parts of a model that will form a slave surface

    24. 24 If you choose the Finite sliding formulation and the Surface to surface discretization method, the contact interaction property that you select cannot specify a “hard” contact pressure-overclosure relationship

    25. 25 What You May Always Need to Know

    26. 26 Job Execution Control Abaqus Job suspend, resume, and terminate abaqus {suspend | resume | terminate} job=job-name abaqus terminate job=input_file 

    27. 27 Automatic stabilization of unstable static 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 motion

    28. 28 How to decide the damping factor Automatic stabilization of static problems with a constant damping factor 1. Based on the dissipated energy fraction,default=0.0002 2. Directly specifying the damping factor 3. Propagating the damping factors from the immediately preceding general step into the current step

    29. 29 Common Difficulties Warning message: Zero pivot and numerical singularity Causes: 1. Nodes may be overconstrained in a model 2. The model might be insufficiently constrained, rigid body motion occurs. TOO MANY ATTEMPTS MADE FOR THIS INCREMENT Causes: so many reasons 1.Cannot reach convergence

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