Material modeling from raw data

OBJECTIVES :

To model a material using raw data and validate the same for a dog bone specimen.

Given material curve:

Procedure :

1. Using data digitizer, the stress and strain data is obtained in the form of an excel workbook with stress unit ksi and strain %.

2. The stress is converted to kg mm ms unit system.

3. The stress strain curve is plotted in an excel file after fitting the curve to avoid irregularities in curve.

4. From the equation obtained, calculate stress for curve fit. Calculate the true stress and strain values.

wkt, True strain = ln(1+engineering strain) True stress = (engineering stress)* exp(true strain)

5. Effective plastic strain and true strain are considered and plotted.

wkt, Effective plastic strain = total true strain - (true stress/E) where E = 144.1 GPa

6. Import the keyword file in LS-prepost and define the material curve from excel file x as true strain and y as Effective plastic strain.

7. Create the Mat 24-Linear elastic plasticity and assign the curve.

8. Create section as shell and assign thickness to the specimen part keyword.

9. Assign BCs to both ends. Prescribed displacement motion to right end and fixed spc in left end.

10. Select necessary Database keywords like ASCII, Extend binary and Binary D3plot to run simulation in LS-Dyna Manager.

Link for simulation and excel files : https://drive.google.com/drive/folders/1BLAukGa0yw8g3efgVebU0v-_uX7EuAnv?usp=sharing

Result and conclusion:

1. True stress and strain contours are plotted.

The maximum strain is induced at the start of component necking and the maximum stress is induced in the necking region and niddle of component. Max strain = 3.759e-3 and maximum stress = 5.424e-4.

2. Validating the material curve.

The material curve validated is 94% accurate and the same is result is plotted by obtaining data from LS-Dyna graph on the stress and strain acting on element 97.

Thus the validated material cure is almost similar to the given curve and young's modulus in kg mm ms unit system. There is no hourglass error and the simulation is uniform throughout the simulation. The stress-strain behaviour after yielding is considered by a hardening curve for the MAT_24.