This calculator is used to calculate the resulting stresses acting in the weld.

A weld of approximately triangular cross section joining two surfaces, approximately at right angles to each other, as in a lap joint. 

Stress is a measure of the average amount of force exerted per unit area. It is a measure of the intensity of the total internal forces acting within a body across imaginary internal surfaces, as a reaction to external applied forces and body forces. 

Shear stress is a stress state where the stress is parallel or tangential to a face of the material, as opposed to normal stress when the stress is perpendicular to the face. 

Polar moment of inertia is a quantity used to predict an object’s ability to resist torsion, in objects (or segments of objects) with an invariant circular cross-section and no significant warping or out-of-plane deformation. It is used to calculate the angular displacement of an object subjected to a torque. It is analogous to the area moment of inertia, which characterizes an object’s ability to resist bending and is required to calculate displacement.

Click her: http://www.calculatoredge.com/calc/fillet.htm