Question on Phase Field Fracture simulation results of the first time step #28858
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Lingfu-Liu
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Q&A Modules: Phase field
Replies: 1 comment 5 replies
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Hello The first result in the table (if the table comes from MOOSE console output) in not from the first time step, but rather the INITIAL step. Note that at t=0 (=strain = 0 here?), you expect to only see any damage? EDIT: my bad. I misread the last table as the output from MOOSE |
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I created a model coupled solid mechanics and phase field method to study 1D bar elongation with damage by gradually adding loads (specify strain). I notice a very strange phenomenon that the first time step can not creat any damage no matter how huge strain I specify.
My script is attached as below.
Postprocessor Values:
(Table 1)
+----------------+----------------+----------------+----------------+
| time | d_ave | sigma_xx_ave | u(end) |
+----------------+----------------+----------------+----------------+
| 0.000000e+00 | 0.000000e+00 | 0.000000e+00 | 0.000000e+00 |
| 1.000000e-06 | 0.000000e+00 | 1.000000e+05 | 1.000000e-06 |
| 2.000000e-06 | 9.082643e-04 | 1.996369e+05 | 2.000000e-06 |
| 3.000000e-06 | 4.445888e-03 | 2.973384e+05 | 3.000000e-06 |
| 4.000000e-06 | 1.212433e-02 | 3.903593e+05 | 4.000000e-06 |
| 5.000000e-06 | 2.520100e-02 | 4.751166e+05 | 5.000000e-06 |
| 6.000000e-06 | 4.462309e-02 | 5.476471e+05 | 6.000000e-06 |
| 7.000000e-06 | 7.097100e-02 | 6.041665e+05 | 7.000000e-06 |
| 8.000000e-06 | 1.044134e-01 | 6.416605e+05 | 8.000000e-06 |
| 9.000000e-06 | 1.446850e-01 | 6.584077e+05 | 9.000000e-06 |
| 1.000000e-05 | 1.910964e-01 | 6.543253e+05 | 1.000000e-05 |
+----------------+----------------+----------------+----------------+
In above table, "time" is equavalent to "strain" specified to the system. I manually calculate the analitical solution of "strain" versus "d"(phase filed of damage) with the belowing implicite process.
I have the following results.
(Table 2)
strain | d_analitical
0.00E+00 | 0
1.00E-06 | 0.000908265
2.00E-06 | 0.004445892
3.00E-06 | 0.012124339
4.00E-06 | 0.025201021
5.00E-06 | 0.04462313
6.00E-06 | 0.070971065
7.00E-06 | 0.104413459
8.00E-06 | 0.144685103
9.00E-06 | 0.191096615
1.00E-05 | 0.242580513
By comparing results in Tables 1 and 2, you may find that if I delete the data of "d" at the second row and second column in Table 1, the rest data of "time" vs "d_ave" in Table 1 matches well with "strain" vs "d_analitical" in Table 2.
In summary, my question is why there is a zero damage (d=0) results at first time step. Even I specify a very huge strain (e.g., 1), "d" is always equal to 0 at first time step.
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