What are the experiments on the joints welded by the spot welding machine?

There are many interesting experiments when checking the welding quality of spot welders and butt welders. When spot welding, seam welding and butt welding joints bear alternating loads, the alternating stress can be less than the yield strength of the material, and the crystal can work for a long time. It will also cause the joint to break, which is called fatigue failure. Some weldments bear alternating loads and are required to carry out fatigue tests. Spot welding and seam welding joints usually carry out repeated bending fatigue, tensile-compression fatigue and thermal fatigue tests.

In addition to the above-mentioned types of experiments for butt welded joints, twisting fatigue and rotational bending fatigue tests can also be carried out according to the application conditions of the weldment. Different fatigue test specimens have different shapes and sizes. During spot welding fatigue tests, they usually show The source of microcracks forms at the edge of the nugget or the heat-affected zone, and then expands to the surface of the base material, causing it to break in an instant.

Bending test and flattening test: This test can measure the plastic deformation level of the butt welded joint subjected to bending and flattening. The bending specimen is determined according to relevant standards. The experimental results can be based on the bending measured when the first crack occurs in the tensile part of the specimen. To evaluate the angle size, you can also bend the sample to a specified angle and check whether there are cracks to evaluate the level of plastic deformation in the joint area. The key during the experiment is how to identify the effectiveness of the first crack. Usually the crack length does not exceed the sample The corresponding bending angle is reasonable when it is 15% of the width.