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  1. mrgoldthorpe

    Entering stress-strain diagram for compression and tension

    Have you tried combined/kinematic hardening (*PLASTIC, HARDENING=COMBINED.. and *CYCLIC HARDENING in ABAQUS old money)? Agreed, it's mainly for metal plasticity but perhaps worth a try. You could quickly use a single element model to attempt to fit its behaviour to your test results...
  2. mrgoldthorpe

    time increment error

    Points loads on a node and plasticity together are not a good idea. You'll probably find that you have excessive yielding around the load. That's perhaps why your displacement (at load point?) is larger than the test value. Try distributing the point load over a larger area, or make a small...
  3. mrgoldthorpe

    3 Point Bend Test Problem

    Robert, For the model you'll need at the very least the elastic modulus and Poisson's ratio of the epoxy. If the test shows significant non-linear behaviour prior to fracture you'll also need the plastic behaviour in terms of say (yield) stress versus equivalent plastic strain. Do you have such...
  4. mrgoldthorpe

    Stresses go beyond yield limit in perfecly-plastic model...

    You have plane strain elements with both ends fixed. Therefore, the individual components of stress can exceed the yield stress according to the yield criterion. The ENCASTRE boundary condition will certainly help to elevate the individual components of stress. Note, however, that the von mises...
  5. mrgoldthorpe

    Logrithmic Plastic Strain Formula confusion (Hardening Table) Urgent

    I don't know a lot about crushable foam, but I suggest you review the measured material data. I think you really need more measurement points. Also, if you take the first "leg" of the red strain-strain curve as elastic behaviour: that would suggest an elastic modulus E of about 11/0.12...
  6. mrgoldthorpe

    Basic Abaqus problem with shear on a plate

    You can't clamp the base. The way to get pure shear is to put symmetry boundary conditions on the base and left-hand edge. Apply a uniform tension to the top edge and a uniform compression of the same magnitude of the right-hand edge. That is: apply pure shear.
  7. mrgoldthorpe

    Material softening and convergence issues

    ... by the way: the reason for restricting the maximum size of an increment. If you let ABAQUS increase it by default, and then it's forced to cut-back because it's rather too large when (say) gross yield or softening cuts in, you can end up completely losing the advantage gained from the...
  8. mrgoldthorpe

    Material softening and convergence issues

    Try relaxing the displacement correction criterion using *CONTROLS .... Once the load/displacement increments are very small the "noise" in nodal displacement corrections during iterations of an increment can easily be the same size as the nodal displacement increments themselves. This leads to...
  9. mrgoldthorpe

    How to set fixed boundary conditions based on element status

    This could be involved, but you could try connecting your intended BC nodes to the boundary via (say) simple truss elements. You then vary the elastic stiffness of each of these truss elements via (User defined) field variables. Initially set the elastic modulus of any particular truss element...
  10. mrgoldthorpe

    Drop down calendar

    You can easily set up a list of 365 dates in the year in one column of the worksheet; perhaps hidden from the user. Then, in the cell you wish to choose the date, use Data...Validation. Here Allow...List and in the Source put the range of dates you established in the above paragraph. I still...
  11. mrgoldthorpe

    How to model necking (damage)

    If you run ABAQUS PRE you'll get a .pes (if memory serves me) file in which all the parameters are resolved. You can run that in CAE. I'm not sure what you are asking in the rest of your question, but you generally need to tune your model against experiments in order to obtain the appropriate...
  12. mrgoldthorpe

    Residual stresses from welding

    Aga, You could try using the UTEMP user subroutine in a model to provide a final temperature distribution and so impose a simulated welding residual stress field. Adjust the UTEMP in order to achieve a reasonable match to your measured profile. However, you'll never get a perfect match; but it...
  13. mrgoldthorpe

    How to model necking (damage)

    Hi, I think perhaps you need to read around the subject a little. In the meantime I attach an ABAQUS input file which does what you want and attempts to simulate the Round Robin cited in the file using *POROUS...
  14. mrgoldthorpe

    Problem with boundary layer model (SSY)

    Hi, My original example had an AMPLITUDE parameter on *BOUNDARY. You don't actually need this parameter; but if you have it you must ensure that the amplitude is unity during the time step that applies the displacements on the boundary of the model. Of course, if the amplitude is zero you'll get...
  15. mrgoldthorpe

    How to quantify brittle failure?

    Chen, The computer modelling cannot tell you that. You need tests on samples of your material.
  16. mrgoldthorpe

    Generating model from text

    Look at your online Abaqus Example Problems Manual. You'll find plenty of .inp files there as examples.
  17. mrgoldthorpe

    Simulation of Tensile test coupon for large plastic deformation and stress triaxility correction

    Perhaps you should incorporate *POROUS METAL PLASTICITY in order to simulate the softening due to micro-void development?
  18. mrgoldthorpe

    Abaqus Max Stress Annotation: Move in Viewport

    In Viewport, Viewport Annotation Options you can change positioning, colours, font size of the legend, titles etc. What you do in a session is written to the abaqus.rpy file. Edit this file and remove what you don't want (just keeping the commands to change the viewport) save the file as a .py...
  19. mrgoldthorpe

    Bolt design in a mine..........Roof bolt

    edit .... do an axiymmetric (2D) model
  20. mrgoldthorpe

    Bolt design in a mine..........Roof bolt

    Chen, Do a simpler 2D plane strain model first to sort out the issues and get some numbers for comparison. Then proceed to more complex 3D.
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