Dear jean-Paul Yes, we can use internal forces for all situations. I must correct my answer by replacing "residual vector" by "internal force vector". However, can we calculate internal force by integrating over boundary surfaces when material model is history dependent and has internal state variable such as plasticity? I think the answer is no, so I have suggested to use "internal force vector" in the first answer instead of integration over the boundary surfaces.
Thank you, Pasha On Sunday, February 26, 2017 at 5:06:18 PM UTC+3:30, Jean-Paul Pelteret wrote: > > Dear Amir, > > >> Why we must calculate reaction forces at a boundary which has external >> force? >> > > You certainly don't have to. In my example I used this as a demonstration > that the forces computed from the internal stresses matched the applied > (uniformly distributed) load. If you believe this then you could happily > apply the same procedure to any surface undergoing displacement control, > knowing that it will produce the desired result. > > >> But we usually calculate reaction forces at BCs with prescribed >> displacement which it is better to calculate them from residual vector >> (which equal to [-1.0 * internal forces] at these BCs). >> > As the body is in equilibrium, they are balanced by the stresses generated >> by the material = internal forces >> > > Ok, I see now where you're coming from. This might be true, but only for > constrained degrees-of-freedom for quasi-static problems. But in his > initial post Hamed wasn't specifically referring to reaction forces (unless > I misunderstood something), but rather the resultant force on an > unspecified boundary surface. Furthermore, for time-dependent problems you > may have additional contributions to these components of the residual due > to the imposition of constraints on the velocity and acceleration field (if > these constraints are non-homogeneous). > > >> Please, did you test the attached code for a plastic material model? >> > > No I haven't. Do you anticipate the result will be any different when > using a plasticity model? If so, how? > > Regards, > Jean-Paul > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
