Week - 9 Material modeling from raw data

objective

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 execl workbook with stress unit ksi and stain %.

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

3. the stress strain curve is plotted in an execl files after fitting the curve to avoid irregularities in curve.

4. from the equation obtained ,calculate stress for curve fit. calculate the stress and strain values.

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

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

effective plastic strain =total plastic strain =total true strain -(true stress/E) where E=144.1Gpa.

6. import the keyword file in the ls-prepost and define the material curve from exel 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 key part word.

9.assign BCs to both ends .prescribed displacement motion to right end and fixed spc inleft end.

10. select necessary data base keyword like ascii ectend binary and binary D3plot to run simulation in ls dyna manager.

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 and niddle of component .Max strain =3.759e-3 and maximum stress =5.424e-4.

2. validating the maqterial 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 curve is almost similar to the given curve and youngs 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 fo rthe MAT_24.

conclusion.

the given experimental value are modelled using material card in LS-dyna and validated using the dogbone specimen.all the objective in the challange are satisfied.