What formula describes wire creep at high temperatures?

[silver-rose]

Wire "Creeping"

Thin wires tend to creep (extend longer over periods of time), particulary at high temperatures.

Is there a "formula" that explains this correlation of the amount of creeping with regards to temperature or other factors?

 

[brewnog]

Yes.

There are many models which attempt to approximate creep, most involve considerations of stress, time, and temperature. One of the simplest is a time hardening model, which addresses the strain in the primary and secondary phases of deformation, where creep rate decreases with increasing strain due to strain hardening of the material:

ε = a σ^b t^n

Here, ε is the strain, σ the stress, t the time, and b and n constants. Differentiate with respect to time to get a creep strain rate.

Anything more in depth you can probably get by hanging around for Astronuc, or alternatively by reading "Fundamentals of Creep in Metals and Alloys" by Michael Kassner, you probably need a good understanding of the phenomena involved in order to select an appropriate model to use.

 

[FredGarvin]

Or you can try to find a creep curve that is close to your loading situation and read it directly off a chart. Examples are usually something like these:

www.tech.plym.ac.uk/sme/mats340/cpdata.pdf