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16 Jan
2019
16 Jan
'19

8:44 a.m.

Not sure if I should open a new thread, but I'm having a very similar problem where I can't figure out how to calculate the reaction forces and torques through a face of a 3D model. I have the model working to the point where I have the following commands execute successfully:

svar = FieldVariable('sigma', 'parameter', field, primary_var_name='sigma') stress = ev('ev_cauchy_stress.3.Omega(m.D, u)', mode='qp', copy_materials=False) svar.set_from_qp(stress, integral) supportstresses = ev('ev_surface_integrate.3.Gamma1(sigma)', var_dict={'sigma':svar}, mode='qp') geo, _ = field.get_mapping(region, integral, 'surface')

I now have what I believe are variables that represent: Cauchy Stress throughout the model (stress) Normal vectors/Jacobians for the face (geo) I am confused as to what supportstresses represents, if it is even a useful quantity, I thought it would be the reaction forces, but the results don't seem to correlate well with the forces I should be seeing

So I am now lost on how to pick out the stresses that correspond to the face where the support is located and then convert that information to a simple np array for use in this equation:

np.sum(np.dot(stress, geo.normal) * geo.det)

My goal once the reaction forces are working is to also calculate reaction torques if possible based on the distances of each force to some normal axis, but I don't know how I would go about getting the position information needed for this.

I can post my full code if that would be helpful. Does anyone have suggestions that could help determine the reaction forces and moments? Thanks!