# Obtaining material parameters from a stress strain diagram (Ls-Dyna)

Member Posts: 7

Hi everyone,

I have a parameter list below to do analysis on Ls-Dyna. However, I am struggling with obtaining or calculating some of them. For example, definition of the tangent modulus is that:

it says " at any specified stress or strain", so how can I know which stress or strain will work for me to calculate tangent modulus? Because there are infinite points that I can calculate the slope.

So, my question is that how can I obtain or calculate the values below? The first four parameters are very simple, but I really need your help for the rest of them.

If there is a library for them (I need these values for 6005,6063 and 6082 aluminium alloys), it would be really beneficial to me.

## Best Answer

• Accepted Answer

Hi @goktug.yilmaz , The answer to your question is an quite an complex ( gettign the tangent modulo of different grades of the Aluminium) unless you have tensile test data, if youhave such data you can use the following forum for calcuating the Tangent modulo

E_tan_Calculated / E ratio may be closer to an Elastic-perfectly plastic case.

#### E_tan_Calculated = [(1+%EL/100)*S_ult - S_yield ]/ [(ln(1/(1-%RA/100)))- (S_yield/E)]

%EL= % Elongation

%RA= % Reduction in Area

E = Modulus

The strengths are self Explanatory.

If you don't know the %RA you can approximate as follows

%RA =200*%EL/(100+2*%EL)

If you have access to Granta Material library, you might get compleat Plasticity modelling Parameters.

Comment down your response for futher help.

Cheers, Ram

## Answers

• edited March 30

Thank you very much for your help dear @ramgopisetti . You have helped a lot. I am very grateful. However, what about other parameters? There is actually little information about the "hardening parameter(beta)" for example.

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