  Response of initial elastic field to stiffness perturbation and its possible
application is investigated. Virtual thermal softening is used to produce the
stiffness reduction for demonstration. It is interpreted that the
redistribution of the initial strain will be developed by the non-uniform
temperature elevation, as which leads to the non-uniform reduction of the
material stiffness. Therefore, the initial filed is related to the stiffness
perturbation and incremental field in a matrix form after eliminating the
thermal expansion effect.
