Weld quality may be determined by several methods. Visual inspection detects incorrect weld sizes and shapes (such as excessive concavity of fillet welds), inadequate penetration on butt welds made from one side, undercutting, overlapping, and surface cracks in the weld or base metal. Dye penetrant inspection uses a penetrating dye and a color developer and is useful in detecting defects with access to the surface. Radiography (making X-ray pictures of the weld) can detect defects as small as 2% of the thickness of the weldment, including porosity, internal cracks, lack of fusion, inadequate penetration, and inclusions. Ultrasonic inspection uses high-frequency sound waves to detect similar flaws, but is expensive and requires trained personnel to interpret the results. Its advantage over radiography is that it is better suited to detecting thin planar defects parallel to the X-ray beam. Destructive tests, such as bend tests, fracture (or nick break) tests, and tensile tests are usually reserved for qualifying a welder or a weld procedure. Acceptance criteria for the various methods of inspection and tests are given in AWS D1.2 [21] and other standards for specific welded aluminum components or structures.

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