For materials like soil flow rule generally non-associated. Non-associated flow rule uses plastic potential function which is different from yield function. So i want to know is there any reference which clearly says about formulation of plastic potential function and parameters involved.
Just some suggestions about plastic potential function.
1. the reason why we need plastic potential function is to reduce the plastic volumetric strain(the plastic volumetric strain will be overestimated by associative plastic flow rule).
2. definition of plastic potential function: you can select a similar function as yield function. it is up to you.Just make sure the plastic potential function curve is small than yield function in stress space.
3. determination of parameters in potential function. very depend on the selection of potential function. for soil mechanics, the consolidation test results can be used to determine relevant parameters. if you use MC or DP yield function, try to use dilation angle to define paramters.
Indeed the determination of the plastic potential is a purely experimental task. Of course the description of the experimental data will be mathematical as a second step. Among many others, "Soil Behaviour and Critical State Soil Mechanics" by David Muir Wood is recommended by me for in depth reading.
You may also modify one of the existing plastic potential functions to fit your soil response.
measure the plastic defromations, including the volumetric and shear strain, the direction of strain, then curve fitting, figure out the fotmulation.
Just some suggestions about plastic potential function.
1. the reason why we need plastic potential function is to reduce the plastic volumetric strain(the plastic volumetric strain will be overestimated by associative plastic flow rule).
2. definition of plastic potential function: you can select a similar function as yield function. it is up to you.Just make sure the plastic potential function curve is small than yield function in stress space.
3. determination of parameters in potential function. very depend on the selection of potential function. for soil mechanics, the consolidation test results can be used to determine relevant parameters. if you use MC or DP yield function, try to use dilation angle to define paramters.
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