Engineering Mechanics

Proceedings Vol. 7 (2001)

INŽENÝRSKÁ MECHANIKA 2001

ENGINEERING MECHANICS 2001

Copyright © 2001 Institute of Thermomechanics, Academy of Sciences of the Czech Republic, Prague

 

Procházka P.
pages 225 - +8p, full text

Eigenstresses and eigenstrains act out a very important role in many branches of applied mechanics. The eigenparameters may represent plastic strains, or plastic stresses (or also prestresses, change of temperature, etc.), and may also serve as free parameters for improving numerical models to get the computed quantities that should be as close as possible to the real state. Special variational formulation can be stated, dealing with the minimum variance of differences between measured and computed values. When using a very useful treatment, transformation field analysis (TFA), having recently been proposed by Dvorak & Prochazka, the problem leads to a linear system of algebraic equations. In this case we start with (elastic material) and the nonlinear properties are involved in the eigenparameters. Desai proposed a similar approach, disturbed state concept (DSC). He uses a certain disturbance function and simulates various mechanical states in a body (damage, elastoplasticity, viscoplasticity, creep, cracking, etc.). Our goal is to generalize the TFA and to start with an estimation of physically nonlinear behavior of the body. Then the algorithm may be applied to the overall behavior of the body as well as to a local observation of the material properties. The disturbance function may be either estimated or determined more precisely from large amount of experiments. Much easier is to state the eigenparameters, which are also more reliable. The Unified Function Concept) (TFA & DSC concept) seems to be very prospective as it involves positive properties of both methods. In the suggested paper we concentrate our attention to the stability of tunnel face. Nonlinear mechanical behavior of this system will be involved in a numerical procedure and results from experiments will be used. The DSC & TFA concept will be applied.

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