Inspection Methods and Acceptance Criteria It may surprise you to learnthat neither the Aluminum Specication nor the AWS D1.2 code it referencesrequires any inspection of production welds other than visual. Other than therequirements on procedure and welder qualication, workmanship, and visualinspection, no other mandatory quality assurance requirements for weldingare required by the Specication. If you want any other inspection by thefabricator or verication inspection by another party, you must specify soelsewhere, such as in contract documents.
Two types of inspection are available: nondestructive testing, sometimesreferred to by the acronym NDT, and destructive testing (also referred to asmechanical testing). Both refer to the condition of the inspected part aftertesting.Nondestructive testing includes:1) Visual inspection detects incorrect weld sizes and shapes, such as excessiveconcavity of llet welds, inadequate penetration on butt welds madefrom one side; undercutting; overlapping; and surface cracks in the weld orbase metal.2) Radiographic inspection (X-ray photographs) (RT) is limited to groovewelds in butt joints. This is because radiographic techniques are generallybest applied to a joint of fairly constant thickness.
Thus, llet welds tend tobe unsuitable for radiographic inspection. Radiography can detect defects assmall as 2% of the thickness of the weldment, including porosity, interna cracks, lack of fusion, inadequate penetration, and inclusions.3) Dye-penetrant inspection (PT) may be performed on all types of weldsand joints. The procedure is to apply a penetrating dye, wait 5 to 10 minutes,and then clean the surface. A developer is then applied, and the surface isinspected for evidence of discontinuities revealed by die that has penetratedthem. This method will show only discontinuities that have access to thesurface of the weld. Care should be taken to fully remove any dye or developerbefore repair welding.
4) Ultrasonic inspection (UT) uses high-frequency sound waves to detectsimilar aws, but it is expensive and requires trained personnel to interpretthe results. Its advantage over radiography is that it is better suited to detectingthin planar defects parallel to the X-ray beam. Ultrasonic inspection is limitedto groove welds, and D1.2 does not include ultrasonic inspection methods oracceptance criteria.
Therefore, when ultrasonic testing is required, the procedure,such as ASTM E164, Standard Recommended Practice for UltrasonicContact Examination of Weldments, and acceptance criteria must be specied.Destructive testing, such as bend tests, tension tests, and fracture tests, areusually reserved for qualifying welders or weld procedures. They can also beused on production weldments if you don't mind making a few extra.Welding aluminum members introduces a consideration that doesn't get muchthought for steel: the effect of welding on the strength of the base metal. (Inhindsight, after the cracking of welded steel frames in the Northridge earthquake,we realized we probably should have been giving this more thought.)
Sometimes it's just too easy to call for joints to be welded to the hilt to avoidthe need to design and detail bolted connections. But the ''less is more''maxim applies to aluminum welding. Not only does welding tend to causedistortions, it signi?cantly reduces the strength of the aluminum base metal.The prerequisite for this section is an understanding of the behavior ofaluminum that's not welded. Once you're comfortable with that, you're readyto see whatwelding changes. This section covers only the design of weldedaluminum members. Section 8.2 addresses the structural design of weldedaluminum connections.