I have been developing the processing maps after hot deformation of a Mg-Rare Earth Alloy. The strain rate sensitivity, m, is becoming negative in some regions. Here, probably due to this, the power dissipation efficiency eta is also becoming negative.
What is the physical interpretation of this? Efficiency is a parameter that is generally defined between 0 and 1. So is its negative value wrong? What could be the reasons?
Dear Neethu,
welcome,
The energy conversion efficiency is a macroscopic parameter not an intensive parameter. So, when you assess it you have to assess it in a global rather than local basis. So, it is proposed to integrate the power dissipation over the whole work piece.
Best wishes
Answering my own question:
One extreme for power dissipation during hot working occurs in materials which are strain rate insensitive, i.e strain rate sensitivity parameter, m=0 or power co-content J=0. When J=0, power content G= total power, P and all the power would be dissipated by heat which leads to plastic instability by a continuum process such as adiabatic shearing.
Hence, J=0 and power dissipation efficiency,eta = 0.
Hence, by theoretical calculation, eta can become negative, but this processing region is unstable.
- Badges
- Science topic
- Similar topics
- Philosophy
- Philosophy Of Science
- Reasoning