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Elasto-Plastic Multilinear Materials

(Note) The elasto-plastic analysis is available in an optional package.

 

The relation of yield stress and strain of the elasto-plastic materials is approximated by a multilinear curve.

 

 

In the figures above, the relation of the yield stress and strain is shown with 3 linear curves.

The left figure shows the stress against the total strain. The right figure shows the stress against the plastic strain.

 

 

where

Total strain Elastic strain Plastic strain Stress Young's modulus

 

 

Therefore,

 

・Total strain = Elastic strain + Plastic strain (*)Initial strain and creep strain are nil.

・ Elastic strain = Stress / Young's modulus

 

If the total strain-stress relation is known, the plastic strain-stress relation can be obtained as follows:

 

 

Femtet can define the elasto-plastic multilinear materials by two input types.

 

(1) Plastic Strain-Stress

 

Define by Young's modulus, Poisson's ratio, and plastic strain-stress multilinear curve.

 

To define the plastic strain-stress multilinear curve, follow the rules below.

 

- The minimum value of the plastic strain must be zero. The stress for that is the yield stress.

- The polyline must be incremental.

- There is no limit on the number of line segments forming the polyline.

- If the material is temperature-dependent, define the strain-stress multilinear curve for all the temperatures used to define the temperature dependency of Young's modulus and Poisson's ratio.

Each temperature can have its own number of line segments.

 

(2) Total Strain-Stress

 

Define by Poisson's ratio and total strain-stress multilinear curve.

 

To define the total strain-stress multilinear curve, follow the rules below.

 

- The minimum value of the total strain (1st data) must be zero.

- The minimum value of the stress (1st data) must be zero. Set the initial yield stress for the 2nd data.

- The polyline must be incremental.

- There is no limit on the number of line segments forming the polyline.

- If the material is temperature-dependent, define the total strain-stress multilinear curve for all the temperatures used to define the temperature dependency of Poisson's ratio.

Each temperature can have its own number of line segments.