Spot welding refers to welding two or more thin overlapping metal sheets at small areas (spots) without using any filling material. Spot welds are extensively used in the automobile and similar industries. Spot welds are most practical for joining metal sheets that are up to 3 mm thick. If the thicknesses of the sheets are not equal, the thickness ratio should not exceed 3. The strength of a spot weld connector depends on the diameter of the weld and the thickness of the sheets.
The sheets are joined by applying local pressure and heat using shaped copper alloy electrodes. The electrodes apply adequate energy to cause the materials of the sheets to melt and mix together.
After removing the electrodes, the melted material solidifies forming a nugget as shown in the figure.
Spot welds work best for low carbon steels. Spot welds of alloy steels with high carbon content tend to be brittle and can crack easily. Aluminium sheets can be joined by spot welds due to their low melting point compared to copper.
You can define spot welds between two solid or two shell faces or between a solid and shell face. You should also define a No penetration contact condition between the two faces for proper modeling.
Spot welds are available for static, buckling,
and frequency studies only.
The following input is needed to define spot welds:
Spot weld first
face 
. Select a solid or a shell face.
Spot weld second
face . Select a shell face or a solid face from
a different component.
Spot weld locations. Select vertices or reference points. Reference points are projected on the faces to determine the locations of the spot welds.
Spot weld diameter. The diameter of a spot weld ranges from 3 mm to 12.5 mm.
To define a spot weld:
Create reference points if needed.
Right-click the Load/Restraint folder of a study and select Connectors.
The Connectors PropertyManager appears.
From the Type drop-down menu, select Spot welds.
In the Spot weld
first face , select a shell or solid face.
In the Spot weld
second face , select a shell or solid face.
In the Spot weld locations, select reference points and vertices. Reference points are projected on the faces to determine the centers of the spot welds.
The program gives a message
if the combined thickness of the model at the spot weld locations is not
practical for the spot welding machine.
In the Spot weld diameter box, select a unit and enter a diameter value.
Click 
.