Md Tareq Hassan You need calibration for the given data. The Young's modulus 𝐸 is as calculated here for being much more realistic. The results are attached in the .inp file. To determine the Young's modulus from your tensile test data, you should consider the initial linear portion of the stress-strain curve. This typically extends from the origin up to the proportional limit, where the curve starts to deviate from linearity. For your specimen, this region is approximately from 0 to 0.1 strain (mm/mm) as per the curve.

It seems that this material has no linear elastic behaviour. Does the stress-strain depend on the loading speed ?

The Young modulus may be measured by vibration measurements (frequency is function of stiffness and mass).

Bruno Barthelet yes, as this is a polymer it's stress-strain depends on the loading speed. I chose 5mm/min displacement control loading.