Week - 9 Material Modeling from Raw Data

AIM:

     To extract the stress-strain data points from the image and input them into LS-DYNA and compare the results of the simulation with that obtained from the raw data.

PROCEDURE:
Extraction of data:

1.The data digitizer tool is used to extract the data from curve 2 of the given material curve image.

                         

2.The data points which obtained the ture stress-strain values are exported to an excel sheet and the values of true stress and strain are gets plotted.

Model Setup:
1.The given dogbone specimen model is imported.

2.The boundary condition are given.

3.The nodes on the left edge of the specimen and constrained in the x and z directions. They are not constrained in the Y direction since the specimen undergoes lateral elongation during the test.

4.The middle node on either edge are constrained in the Y directions.

Prescribed Motion:

1.A displacement is given to the nodes at the right edge of the specimen.

Section Definition:

1.The dog bone specimen is defined with shell elements of thickness 2mm and ELFORM16.

Material Definition:

1.The MAT24 piecewise card is defined with the following parameters. The unit system used is kg-mm-ms. The young's modulus is 20.9e+6 psi which is 144.100GPa.

2.The value of density and poisson's ratio are given.

3.The LCSS contains the load curve of effective plastic strain EPS VS effective stress ES.

4.The effective plastic strain is calculated in the excel sheet from the true stress value using the relation.

5.Effective plastic strain = True stain - (True stress / Young's Modulus)

6.The region of the curve after yield point is the plastic part of the curve. Therefore the values in the excel sheet after this stress ppoint and the corresponding EPS values are input into DYNA and the curve is generated.

Part Definiton:

1.The material and the section ID are then assigned to the dogbone specimen.

Database and Control cards:

1.The database card are defined.

2.The timestep for BINARY_D3PLOT and ELOUT are 0.1ms.

3.Database_Extent_Binarycard with STRFLG is used to compute the elastic strain in model.

4.Since, the tensile test of the specimen is a quasi-static analysis it carried out using an implict scheme. The dt0 value is given as 0.0025 ms.

OUTPUT:

1.Von-mises Stress:

     The maximum stress is 0.2709 GPa which is higher than the yield strength limit off 144 GPa. Which means that plastic deformation occurs in the material. The peak effective plastic strain is 0.00756.

     The plot of X-stress and effective plastic strain of a particular element in  the middle of the specimen.

1.X-Stress:

2.Effective plastic strain:

 Comparision:

1.The stress and strain values can be experted into excel sheet and compared with the plot form the raw data to validate the results.

% Strain Strain value Stress, (ksi) Stress, (GPa) EPS EPS True stress 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 7.75E-06 1.12E-03 6.06E-03 6.06E-05 1.14E+00 7.87E-03 6.00E-06 1.55E-05 2.23E-03 1.45E-02 1.45E-04 2.80E+00 1.93E-02 1.15E-05 2.32E-05 3.35E-03 2.43E-02 2.43E-04 4.88E+00 3.36E-02 9.24E-06 3.10E-05 4.47E-03 3.52E-02 3.52E-04 7.16E+00 4.93E-02 9.21E-06 3.87E-05 5.58E-03 4.73E-02 4.73E-04 1.01E+01 6.94E-02 -8.34E-06 4.65E-05 6.70E-03 6.19E-02 6.19E-04 1.30E+01 8.94E-02 -1.81E-06 5.42E-05 7.82E-03 7.28E-02 7.28E-04 1.51E+01 1.04E-01 3.08E-06 6.20E-05 8.93E-03 8.13E-02 8.13E-04 1.72E+01 1.19E-01 -1.12E-05 6.97E-05 1.00E-02 8.98E-02 8.98E-04 1.88E+01 1.29E-01 -7.94E-07 7.75E-05 1.12E-02 9.58E-02 9.58E-04 2.00E+01 1.38E-01 2.84E-07 8.52E-05 1.23E-02 1.02E-01 1.02E-03 2.10E+01 1.44E-01 1.61E-05 9.30E-05 1.34E-02 1.08E-01 1.08E-03 2.19E+01 1.51E-01 3.20E-05 1.01E-04 1.45E-02 1.13E-01 1.13E-03 2.26E+01 1.56E-01 4.57E-05 1.08E-04 1.56E-02 1.19E-01 1.19E-03 2.34E+01 1.62E-01 6.64E-05 1.16E-04 1.67E-02 1.26E-01 1.26E-03 2.44E+01 1.68E-01 9.43E-05 1.24E-04 1.79E-02 1.33E-01 1.33E-03 2.53E+01 1.74E-01 1.22E-04 1.32E-04 1.90E-02 1.42E-01 1.42E-03 2.61E+01 1.80E-01 1.67E-04 1.39E-04 2.01E-02 1.53E-01 1.53E-03 2.70E+01 1.86E-01 2.36E-04 1.47E-04 2.12E-02 1.62E-01 1.62E-03 2.79E+01 1.92E-01 2.88E-04 1.55E-04 2.23E-02 1.77E-01 1.77E-03 2.89E+01 2.00E-01 3.83E-04 1.63E-04 2.34E-02 1.92E-01 1.92E-03 3.00E+01 2.07E-01 4.90E-04 1.70E-04 2.46E-02 2.12E-01 2.12E-03 3.10E+01 2.14E-01 6.34E-04 1.78E-04 2.57E-02 2.29E-01 2.29E-03 3.17E+01 2.19E-01 7.68E-04 1.86E-04 2.68E-02 2.51E-01 2.51E-03 3.25E+01 2.24E-01 9.62E-04 1.94E-04 2.79E-02 2.77E-01 2.77E-03 3.32E+01 2.29E-01 1.18E-03 2.01E-04 2.90E-02 3.00E-01 3.00E-03 3.38E+01 2.33E-01 1.38E-03 2.09E-04 3.01E-02 3.31E-01 3.31E-03 3.43E+01 2.37E-01 1.67E-03 2.17E-04 3.13E-02 3.62E-01 3.62E-03 3.47E+01 2.39E-01 1.96E-03 2.25E-04 3.24E-02 3.89E-01 3.89E-03 3.51E+01 2.42E-01 2.21E-03 2.32E-04 3.35E-02 4.18E-01 4.18E-03 3.54E+01 2.44E-01 2.48E-03 2.40E-04 3.46E-02 4.50E-01 4.50E-03 3.57E+01 2.46E-01 2.79E-03 2.48E-04 3.57E-02 4.86E-01 4.86E-03 3.61E+01 2.49E-01 3.14E-03 2.56E-04 3.68E-02 5.10E-01 5.10E-03 3.63E+01 2.50E-01 3.37E-03 2.63E-04 3.80E-02 5.43E-01 5.43E-03 3.65E+01 2.51E-01 3.68E-03 2.71E-04 3.91E-02 5.69E-01 5.69E-03 3.67E+01 2.53E-01 3.94E-03 2.79E-04 4.02E-02 5.94E-01 5.94E-03 3.69E+01 2.54E-01 4.18E-03 2.87E-04 4.13E-02 6.25E-01 6.25E-03 3.71E+01 2.56E-01 4.47E-03 2.94E-04 4.24E-02 6.56E-01 6.56E-03 3.74E+01 2.58E-01 4.77E-03 3.02E-04 4.35E-02 6.77E-01 6.77E-03 3.75E+01 2.58E-01 4.98E-03 3.10E-04 4.47E-02 6.98E-01 6.98E-03 3.76E+01 2.59E-01 5.18E-03 3.18E-04 4.58E-02

Experimental data					Simulated values

     The curve is fits the experimental data. The given calues are validated using the MAT24 card. In this simulation the strain is higher than the experimental data since the defined displacement causes a higher strain.

RESULT:

     Thus the stress-strain data points from the image and input them into LS-DYNA and compare the results of the simulation with that obtained from the raw data is performed sucessfully.