Maybe I have misunderstood the question, but if your crosshead speed is constant then your strain rate is constant too. It will be unaffected by temperature, (assuming the strain is uniform of course).

The strain rate during tensile testing may be calculated by dividing the crosshead speed by the instantaneous gauge length. In other words, d/dt (epsilon) = v/l where, epsilon is the true strain, v is the crosshead speed and l is the instantaneous gauge length. For given values of v and l obtained from your tensile test you can then calculate the corresponding strain rate. You can then plot the variation of strain rate with gauge length (since v is a constant in your case) for a sample tested at a given temperature. For aluminum alloys the gauge length will be higher, greater the testing temperature, and therefore the separate strain rate versus gauge length curves wikll have to be drawn for each sample. Hope this helps. 

Thank You professor. and its helpful..

Maybe I have misunderstood the question, but if your crosshead speed is constant then your strain rate is constant too. It will be unaffected by temperature, (assuming the strain is uniform of course).

Dear Prof.Robinson.,

    d/dt (epsilon) = v/l.., in which instantaneous gauge length will be differ with respect to temperatures for constant crosshead speed. Am I right professor..? 

My understanding is the strain rate is translated to cross-head speed in machine terms so if the strain rate is constant then the crosshead speed calculated should be the same i.e. the stroke and time relationship

Strain rate of some materials is dependent on  the temperature.  but constant cross head speed means that the strain rate is constant . In that case as Prof J S Robinson said stain rate is unaffected by the temperature.

I would like to add the following to Mr. Thangapandian's response to Prof. Robinson. The instantaneous gauge length will be different for specimens tested at different temperatures because of thermal expansion (or contraction). Regarding the issue related to the strain rate, if it is accepted that the strain rate is calculated as crosshead speed divided by length, i.e. v/l, the engineering strain rate will be constant for a constant crosshead speed, both the numerator and the denominator will be constant in this case. However, the true strain rate will have a constant value numerator but the denominator will be  a continuous variable (increasing in a tensile test) and therefore the true strain rate can not be a constant.  The general practice is to use engineering strain and strain rate only for relatively small deformations perhaps because of their simplicity but use of true strain and true strain rate will be useful for all deformations irrespective of the magnitude of the deformation. In cases such as rolling (large compressive strain) and superplasticity testing (large tensile strain) it is essential to use true strain and true strain rate.

Perhaps answering your question is closely linked to how the Zener Hollomon parameter relates strain rate and temperature with hot deformation. You may want to have a look at :

Zener, C., and J. H. Hollomon. "Effect of strain rate upon plastic flow of steel." Journal of Applied physics 15.1 (1944): 22-32.

You also can read more recent use of this parameters in the current literature. Many researchers have used the correlation to explain/characterize material's performance under high strain rates and high temperatures.

Also, one has to note carefully that both strain rate and temperature are typically non-uniformly distributed in the deforming bodies under industrial processes.

Hope this helps

I agree with Prof Robinson and Prof Khan - in your case the strain rate is unaffected by the temperature.

If you are interested in the mechanical behavior of aluminum alloys such as AA5182, see the attached paper dealing with Mechanical Properties at temperatures ranging from −120 to 150 ◦C and with strain rates from 10−6 to 10−1 s−1.

Eps=Eps(elast)+Eps(pl)+Eps(temp)

You only specify the full deformation ( displacement).

Сhange what strain you are interested in?

V.N.

Dear Adin...

   But what happen when the alloy processed after 200 ◦C, 300 ◦C and 400 ◦C..

if cross-head speed is constant then strain rate will also be same. I think higher temperature testing will not be affecting the cross-head and strain rate relation, but you can have increased value of cross-head speed means strain rate at higher temperature.