Section 6: Selected Applications & Techniques

6.3.1: UT of Weldments (Welded Joints)
The most commonly occurring defects in welded joints are porosity, slag
inclusions, lack of side-wall fusion, lack of inter-run fusion, lack of root
penetration, undercutting, and longitudinal or transverse cracks.
With the exception of single gas pores all the defects listed are usually well
detectable by ultrasonics. Most applications are on low-alloy construction
quality steels, however, welds in aluminum can also be tested. Ultrasonic flaw
detection has long been the preferred method for nondestructive testing in
welding applications. This safe, accurate, and simple technique has pushed
ultrasonics to the forefront of inspection technology.
Ultrasonic weld inspections are typically performed using a straight beam
transducer in conjunction with an angle beam transducer and wedge. A
straight beam transducer, producing a longitudinal wave at normal incidence
into the test piece, is first used to locate any laminations in or near the heataffected
zone. This is important because an angle beam transducer may not
be able to provide a return signal from a laminar flaw.