Simple visual assessment of self-piercing riveting is worthwhile because appearance can give a good indication of joint quality.
On the top sheet, a good joint will show the rivet head in firm contact with the material (and completely flush when using a countersunk rivet). There should be no cracks in the head of the rivet or in the surrounding material. The joint should not be loose, and there should be little or no distortion of the component.
On the die side, there should be a symmetrical button of the correct diameter and shape (determined by the die). Ideally, the tail of the rivet should not pierce the bottom sheet or be visible. This may not be significant for some applications but for components subjected to fatigue loading or corrosive environments in service it will be particularly important. It is also important that there are no cracks in or around the button. There may be cosmetic reasons why the button should be neatly formed and free of cracks and other imperfections.
More detailed inspection is likely to include examining a cross-sectioned joint. This will allow assessment of the joint's interior features.
Further information:
FAQ: What should be checked when making a detailed examination of a self-piercing riveted joint?