Page 230 - Welding of Aluminium and its Alloys

210 The welding of aluminium and its alloys

(a) Probe
Specimen

X Y
Flaw
Probe
(b)

X Z Y
Probe on specimen Cathode ray screen
11.12 Compression wave examination. Courtesy of TWI Ltd.

Piezoelectric crystal Electrical
connection

Centre line of
ultrasonic beam Perspex
Thin layer
of couplant

Probe angle, α Probe index mark
11.13 Angle probe examination of a weld. Courtesy of TWI Ltd.

method is to scan the probe on the surface of the parent metal adjacent to
the weld.To do this the surface must be free of scale, spatter and roughness
and the parent metal should ideally be free of laminations and excessive
inclusions.A couplant, generally water, oil, grease or glycerine, is applied to
form a film on the surface of the test piece. This aids the transmission of
the beam into the sample.