Question

Interpret typical creep curve and use mathematical analysis to predict creep behaviour

Answer 1

1. Primary creep: starts at a rapid rate and slows with time.

2. Secondary creep: has a relatively uniform rate.

3. Tertiary creep: has an accelerated creep rate and terminates when the materials break or ruptured.

Mathematical analysis to predict creep behaviour can be done by the following models.

Larson Miller Parameter

This model is based on Arrhenius rate equation.

T= temperature.  

tr= time before failure

C= material specific constant

It predicts rupture lives given certain temperature and stress.

Creep general equation:

In material science creep is the tendency of a solid material to move slowly under the influence of persistent mechanical stresses or a timed dependent deformation at elevated temperatures and constant stresses.