Select the Use weak constraints check box to get accurate distributed reactions. Extra variables that correspond to the reaction traction distribution are automatically added to the solution components.
With weak constraints activated, COMSOL Multiphysics adds the reaction forces to the solution components. The variables are denoted X_lm, where
X is the name of the constrained degree of freedom (as, for example,
u_lm and
v_lm). The extension
lm stands for
Lagrange multipliers. It is only possible to evaluate reaction forces on constrained boundaries in the directions of the constraints.