Week-6 Calculate the Stretch Ratio by comparing the ELFORM (-2,-1,1,2) with Ogden_Material Model.
Week-6 Calculate the Stretch Ratio by comparing the ELFORM (-2,-1,1,2) with Ogden_Material Model.
Aim: Simulate the given model with different elemental formulations by assigning the appropriate key cards and calculate strech ratios.
Explanation:
The given model has only the material data and this tensile.k file is imported into LS Dyna prepost from file -> open
For this simulation to run we need a certain keycards to be present which are mandatory and other keycards for getting ouput requests.
After importing the file into prepost,
1) Creating solid meshed model of 10mm x 10mm x 10mm
This is done by shape mesher from element and mesh
Then create
3) Defining Section card for solidl for the model from key word manager -> all -> section -> solid
Here this ELFORM is changed to simulate with different elemental formulations
4) Material card is given and the values for rho, mu are converted to suit the unit system chosen.
After the section id and materail id are created, they are then assigned to the parts in the model.
From key word manager -> model -> PART in SECID and MID for Box
4) Constraining the nodes
The model is to be constrained in x direction for all nodes on one face
So the vertical nodes are constrained in y axis direction
Similarly the horizontal center nodes on the same face are constrained in z axis direction
5) Prescribed imposed motion displacement on opposite face nodes
The motion is defined using curve
6) Control cards
After the contact, control cards are chosen fron keyword manager -> all -> control -> Termination
The end time is chosen to be 1 s since we are using Implicit method which is load step based.
Implicit Auto
Here IAUTO is taken 1 so the time step is adjusted automatically and ITEOPT is 50 so it takes 50 max iterations.
Implicit General
IMFLAG is 1 to activate implicit solver
Implicit Solver
The rest options are kept default.
7) Database card
After the control cards, the output requests are updated from Keyword manager -> all -> Database ->
Binary_d3plot for contours and animations
This is to get strain values for comparing the data
The energy values, forces on parts, nodes are updated in ASCII
ELOUT for elemental output
GLSTAT for energy values
MATSUM for materail energies.
with DT as 0.1 ms
8) After this keyword cards are created and updated, then this keyword file is saved.
Then opening LS RUN and run for all elemental formulations.
Results:
The d3plot is opened as binary file in LS prepost and following max stress contour is obtained at end for ELFORM 1.
The d3plot is opened as binary file in LS prepost and following max stress contour is obtained at end for ELFORM -1.
The d3plot is opened as binary file in LS prepost and following max stress contour is obtained at end for ELFORM 2.
The d3plot is opened as binary file in LS prepost and following max stress contour is obtained at end for ELFORM -2.
Energy plot for solid spotweld from glstat on ASCII
Energy plot for beam spotweld from glstat on ASCII
The stress and strain in Post processing of LS Dyna is of True Stress and True Strain
COnverting them to Engineering Stress and Strain
Eng Strain = `e^(epsilon_t)-1`
Eng Stress = `sigma_t/(1+epsilon)`
Stretch ratio `lambda = 1+epsilon`
Conversion from the data of LS Dyna True Stress and Strain to Eng Stress ans strain
ELFORM 1
| Time (sec) | True Stress | True Strain | Eng stress | Eng strain | Stretch |
| 0 | 0 | 0 | 0 | 0 | 1 |
| 0.01 | 5.94E-02 | 0.04878 | 0.056582 | 0.049989 | 1.049989 |
| 0.0258 | 1.50E-01 | 0.1215 | 0.133193 | 0.129189 | 1.129189 |
| 0.05 | 2.88E-01 | 0.2629 | 2.21E-01 | 0.300697 | 1.300697 |
| 0.09 | 4.95E-01 | 0.3739 | 0.340376 | 0.453392 | 1.453392 |
| 0.1538 | 8.04E-01 | 0.5698 | 0.454604 | 0.767913 | 1.767913 |
| 0.2538 | 1.27E+00 | 0.8175 | 0.560748 | 1.264831 | 2.264831 |
| 0.3538 | 1.73E+00 | 1.061 | 0.599462 | 1.889259 | 2.889259 |
| 0.4538 | 2.20E+00 | 1.181 | 0.676258 | 2.25763 | 3.25763 |
| 0.55 | 2.69E+00 | 1.323 | 0.716974 | 2.754669 | 3.754669 |
| 0.65 | 3.20E+00 | 1.448 | 0.752833 | 3.254597 | 4.254597 |
| 0.75 | 3.73E+00 | 1.558 | 0.784745 | 3.749313 | 4.749313 |
| 0.85 | 4.26E+00 | 1.658 | 0.811804 | 4.248803 | 5.248803 |
| 0.95 | 4.79E+00 | 1.749 | 0.832514 | 4.748851 | 5.748851 |
| 1 | 5.02E+00 | 1.788 | 0.84032 | 4.977486 | 5.977486 |
ELFORM -1
| Time (sec) | True Stress | True Strain | Eng Stress | Eng Strain | Stretch |
| 0 | 0 | 0 | 0 | 0 | 1 |
| 0.01 | 0.05941 | 0.04878 | 0.056582 | 0.049989 | 1.049989 |
| 0.0258 | 0.1504 | 0.1215 | 0.133193 | 0.129189 | 1.129189 |
| 0.05 | 0.2881 | 0.2269 | 0.229616 | 0.254704 | 1.254704 |
| 0.09 | 0.4947 | 0.3739 | 0.340376 | 0.453392 | 1.453392 |
| 0.1538 | 0.8036 | 0.5698 | 0.454547 | 0.767913 | 1.767913 |
| 0.2538 | 1.27 | 0.8173 | 0.56086 | 1.264378 | 2.264378 |
| 0.3538 | 1.731 | 1.016 | 0.626692 | 1.762124 | 2.762124 |
| 0.4538 | 2.203 | 1.182 | 0.675583 | 2.260889 | 3.260889 |
| 0.55 | 2.692 | 1.323 | 0.716974 | 2.754669 | 3.754669 |
| 0.65 | 3.202 | 1.448 | 0.752598 | 3.254597 | 4.254597 |
| 0.75 | 3.727 | 1.558 | 0.784745 | 3.749313 | 4.749313 |
| 0.85 | 4.26 | 1.658 | 0.811614 | 4.248803 | 5.248803 |
| 0.95 | 4.786 | 1.749 | 0.832514 | 4.748851 | 5.748851 |
| 1 | 5.023 | 1.788 | 0.84032 | 4.977486 | 5.977486 |
ELFORM 2
| 0 | 0 | 0 | 0 | 0 | 1 |
| 0.01 | 0.05941 | 0.04878 | 0.056582 | 0.049989 | 1.049989 |
| 0.0258 | 0.1504 | 0.1215 | 0.133193 | 0.129189 | 1.129189 |
| 0.05 | 0.2881 | 0.2269 | 0.229616 | 0.254704 | 1.254704 |
| 0.09 | 0.4947 | 0.3739 | 0.340376 | 0.453392 | 1.453392 |
| 0.1538 | 0.8086 | 0.5698 | 0.457375 | 0.767913 | 1.767913 |
| 0.2538 | 1.27 | 0.8173 | 0.56086 | 1.264378 | 2.264378 |
| 0.3538 | 1.731 | 1.016 | 0.626692 | 1.762124 | 2.762124 |
| 0.4538 | 2.203 | 1.182 | 0.675583 | 2.260889 | 3.260889 |
| 0.55 | 2.692 | 1.323 | 0.716974 | 2.754669 | 3.754669 |
| 0.65 | 3.202 | 1.448 | 0.752598 | 3.254597 | 4.254597 |
| 0.75 | 3.727 | 1.558 | 0.784745 | 3.749313 | 4.749313 |
| 0.85 | 4.265 | 1.659 | 0.811754 | 4.254054 | 5.254054 |
| 0.95 | 4.786 | 1.749 | 0.832514 | 4.748851 | 5.748851 |
| 1 | 5.025 | 1.778 | 0.849103 | 4.918009 | 5.918009 |
ELFOMR -2
| 0 | 0 | 0 | 0 | 0 | 1 |
| 0.01 | 0.05941 | 0.04878 | 0.056582 | 0.049989 | 1.049989 |
| 0.0258 | 0.1504 | 0.1215 | 0.133193 | 0.129189 | 1.129189 |
| 0.05 | 0.2881 | 0.2269 | 0.229616 | 0.254704 | 1.254704 |
| 0.09 | 0.4947 | 0.3739 | 0.340376 | 0.453392 | 1.453392 |
| 0.1538 | 0.8036 | 0.5698 | 0.454547 | 0.767913 | 1.767913 |
| 0.2538 | 1.27 | 0.8174 | 0.560804 | 1.264604 | 2.264604 |
| 0.3538 | 1.731 | 1.016 | 0.626692 | 1.762124 | 2.762124 |
| 0.4538 | 2.202 | 1.181 | 0.675951 | 2.25763 | 3.25763 |
| 0.55 | 2.692 | 1.324 | 0.716257 | 2.758425 | 3.758425 |
| 0.65 | 3.202 | 1.448 | 0.752598 | 3.254597 | 4.254597 |
| 0.75 | 3.728 | 1.558 | 0.784956 | 3.749313 | 4.749313 |
| 0.85 | 4.259 | 1.658 | 0.811423 | 4.248803 | 5.248803 |
| 0.95 | 4.787 | 1.749 | 0.832688 | 4.748851 | 5.748851 |
| 1 | 5.032 | 1.787 | 0.842668 | 4.971511 | 5.971511 |
Comparison graph for Eng stress and stretch for all the formulations
Conclusion:
The given models are successfully simulated in LS Dyna.