Use the Boundary Stress node to define the total surface (boundary) stress through a stress tensor, a traction force, or a pressure. Add this node from the Mechanical submenu. The stress condition reads

where is a symmetric stress tensor, the product defines a traction force. The traction condition reads

where Ftr is the surface traction force. The pressure condition reads

where pbnd is the pressure applied to the boundary (acting in the normal direction).

Select a Stress type — Stress tensor, Traction (the default), or Pressure. For Stress tensor enter the (symmetric) Stress tensor (SI unit: N/m2) components, for Traction enter the traction force Ftr (SI unit: N/m2) components, and for Pressure enter the boundary pressure pbnd (SI unit: Pa).