Week - 9 Material Modeling from Raw Data

SInce we need effective stress and effective strain data to create the material curve in LS PrePost, we convert this true stress and true strain

 

Effective stress = True Stress

Effective Strain = True Strain - (True Stress/Young's Modulus)

 

Given Young's modulus is 20.9E+06 psi and converting it to given units we get E = 144.100 kg/mm. ms^2.

  

TRUE STRAIN	TRUE STRESS (gpa)
0	0
9.88471E-05	0.015735698
0.000308506	0.046490176
0.000456568	0.068662337
0.000567483	0.084396656
0.000727614	0.106567437
0.000838739	0.123733315
0.000949342	0.137320813
0.00108429	0.152336905
0.00129207	0.170208805
0.00145074	0.182360125
0.0016941	0.195933834
0.00187638	0.204504017
0.00200997	0.210215634
0.0022525	0.218063937
0.00250678	0.223763832
0.00274878	0.228033066
0.00301492	0.232300231
0.00329313	0.236566018
0.00363147	0.239394247
0.00394568	0.242225235
0.00427185	0.244339167
0.00461019	0.247167397
0.00492419	0.248566343
0.00502095	0.249988042
0.00538312	0.250667175
0.00566091	0.252070258
0.00596284	0.253470584
0.00611994	0.254886077
0.0064098	0.256287782
0.00662714	0.256981394
0.00701355	0.258372756

 

 

 

Here the true stress converted into GPA.

 

EFFECTIVE STRAIN=Total True strain-(True stress/young's modulus)	Effective stress= True stress
EFFECTIVE STRAIN	EFFECTIVE STRESS
0	0
-1.03527E-05	0.015735698
-1.41184E-05	0.046490176
-1.99229E-05	0.068662337
-1.81982E-05	0.084396656
-1.19241E-05	0.106567437
-1.99238E-05	0.123733315
-3.61298E-06	0.137320813
2.7129E-05	0.152336905
0.000110885	0.170208805
0.000185229	0.182360125
0.000334393	0.195933834
0.000457199	0.204504017
0.000551152	0.210215634
0.000739218	0.218063937
0.000953943	0.223763832
0.001166316	0.228033066
0.001402843	0.232300231
0.00165145	0.236566018
0.001970164	0.239394247
0.002264728	0.242225235
0.002576228	0.244339167
0.002894941	0.247167397
0.003199233	0.248566343
0.003286127	0.249988042
0.003643584	0.250667175
0.003911637	0.252070258
0.004203849	0.253470584
0.004351126	0.254886077
0.004631259	0.256287782
0.004843785	0.256981394
0.00522054	0.258372756

we use this curve as a material curve. 

PROCEDURE:

Open the  dogbone specimen in LS Dyna .

Necessary cards are generated for simulation.

SECTION:

 Material CURVE:

This effective stress vs effective strain saved in csv format is loaded with LoadXY data.

Plotting it we get,

 

MAT_24

Boundary Conditions:

Fixing the nodes

Displacement curve:

Giving displacement of max 1 mm gives close to the highest value strain in the curve.

Boundary prescibed motion:

Termination time is given 1 ms

Output Data:

D3plot:

Extent Binary:

In ASCII

ELOUT and GLSTAT is activated.

Result:

Simulation

 

Uniaxial X Stress is plotted for center elements form History

 

Similarly X strain for the same element

 

 

Using cross plot we get True Stress vs True Strain

 

This curve is validated with the given true stress strain curve

 

Conclusion:

The given Stress strain curve is converted to material data and is validated with given Dogbone specimen. From the results it can be concluded that the material model build is fairly accurate and acceptable, however more validation tests are recommended.