What does (dW/dt) =0 ( where W is the external work) indicate.?

[soildynamics]

I am running ElastoPlastic analysis. With application of the load, the external work of the whole model at a specific time reaches a peack and starts to become a decreasing function of time, although the load is increasing. After that the external work becomes a decreasing function of time.
I do not understand the underlying physical cause for this outcome.
My energy equation
E(external force)= E(elastic)+ E (plastic dissipation)+E(artifical damping)
thanks for help

 

[btrueblood]

Is the dominant load tensile? Are the members thinning as they elongate?

 

[soildynamics]

No my material (soil) only takes compression

 

[40818]

Soil??
I wouldn't have said that it actually falls into a "material type" which exhibits elastic/inelastic properties.
I would almost certainly think your analysis concept is flawed. Describe your load/reaction system (i.e explain whats going on and how) and we might be able to give better guidance.

 

[soildynamics]

Please read my explaination and give me your physical opinion
I have total load applied on a mixture porous medium (Soil solid matrix and water), which is partially drained. Initially, when the dW/dt>0, the total load is being carried by both the solid matrix and water. However, most of that load is carried by solid matrix as the pore water pressure is being dissipated at this stage (water is leaving the sample).Later on when the sample porosity becomes small due to consolidation and with increasing the load, the water will be confined within the sample (undrained case will prodominate) and the total load will be mainly carried by water : the external work will be transfered to pore water pressure without generating any stress in the solid matrix

 

[40818]

Ok, so what is your analysis trying to show? Or what are you wanting out of it?

 

[xerf]

I think the integrated energy balance is Etotal=constant.

If the external work reaches a plateau (dW/dt=0) it means the supports of the external loads have zero displacements.

Maybe after a while, the structure becomes incompressible.

 

[soildynamics]

Thank you xerf

 

[instability10]

xerf ..why the structure becomes incompressible when dW/dt=0.

 

[xerf]

It was just a guess based on....

"...and with increasing the load, the water will be confined within the sample (undrained case will prodominate) and the total load will be mainly carried by water."