Spot welds provide a mechanism to rigidly connect two discrete points in a model and can be used to represent welds, rivets, bolts, etc. The points usually belong to two different surfaces and are defined on the geometry (see DesignModeler or SpaceClaim help).

During the solver initialization process, the two points defining each spot weld will be connected by a rigid beam element. Additionally, rigid beam elements will be generated on each surface to enable transfer of rotations at the spot weld location (see figure below). If the point of the spot weld lies on a shell body, both translational and rotational degrees of freedom will be linked at the connecting point. If the point of the spot weld lies on a surface of a solid body, additional rigid beam elements will be generated to enable transfer of rotations at the spot weld location.

Spot welds can be released during a simulation using the Breakable Stress or Force option. If the stress criteria is selected the user will be asked to define an effective cross sectional area. This is used to convert the defined stress limits into equivalent force limits. A spot weld will break (release) if the following criteria is exceeded:

(3–1)

Where:

f_n and f_s are normal and shear interface forces

S_n and S_s are the maximum allowed normal and shear force limits

n and s are user defined exponential coefficients

Note that the normal interface force f_n is non-zero for tensile values only.

After failure of the spot weld the rigid body connecting the points is removed from the simulation.

Spot welds of zero length are permitted. However, if such spot welds are defined as breakable the above failure  criteria is modified since local normal and shear directions cannot be defined. A modified criteria is used with global forces:

(3–2)

Where, are the force differences across the spot weld in the global coordinate system.