Solutions of the Differential Equations for Flow-Processes

There are some characteristic cases with great importance in the field of engineering. As a first approximation we use one dimensional flow processes and consider lateral influences only to describe pressure effects. 

Visco-Ebstic Behavior, Relaxation of Deformation Caused by a Constant Stress o0 

Consequence Retarded deformation created by gradually occurring displacements favouring the direction of an external stress. 

Experimental Measuring the strain behavior (creep) at a given constant stress. At time t = 0 we subject our sample to an external stress a0, connected to an elastic potential A = o0rq/3 at every flow element. This elastic deformation is a disturbance of the thermodynamical equilibrium. At the same time this stress creates a purely elastic deformation y0 = o0/G0 of the whole body. 3 

Assuming T Tg for reversible flow processes (visco-elastic behaviour) Eq. (32) yields 

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Solutions of the Differential Equations for Flow Processes with Variable External Stress and Field... 

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