Reliable and accurate Delta technique, a nondestructive ultrasonics method, uses redirection of energy to detect randomly oriented imperfections in fusion butt welds. Data on flaws can be read from either an oscilloscope or a printout

Cross, B. T.

Hanna, K. J.

Tooley, W. M.

English

NASA Technical Reports Server

September 1970 	 Brief 70-10514 
NASA TECH BRIEF H 
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Ultrasonic Detection of Flaws in Fusion Butt Welds 
vveuu 
J-L 
Sound-Beam Pattern 
in Parent Material
Weld Defect 
Delta Configuration; Diagrammatic 
The reliable and accurate Delta technique is a non-
destructive ultrasonics method that uses redirection 
of energy for detection of flaws in fusion butt welds; 
randomly oriented imperfections can be detected. 
Data on flaws can be read from either an oscilloscope 
or a printout. 
Ultrasonic sound energy is introduced into the 
material being investigated at an angle that produces
shear-wave energy in the material (see fig.); for welds 
it is introduced into the adjacent parent material. 
The sound propagates in the material until it strikes an 
interface, which is anything differing in acoutic im-
pedance from the parent material and interrupting 
the propagation pattern of the sound beam. The inter-
face may be an inclusion, crack, or absence of weld 
penetration or fusion. At the interface the sound ener-
gy may be (1) simply reflected (it remains shear energy 
as long as it is within the material); (2) converted in 
mode from shear to longitudinal (this does not imply 
that the shear energy is absorbed; the shear and 
longitudinal energies occur simultaneously in the 
material and merely propagate in manners character-
istic of their particular forms); or (3) reradiated (ex-
periments have shown the apparent occurrence of this 
phenomenon, but the manner of its occurrence is 
unclear; in concept the defect acts as a new source 
of the sound energy). 
Any energy redirected from the defect can provide 
information about the defect. The energy received at 
the receiving search ,
 unit (RSU) conveys information 
about the defect regardless of which of the several 
paths it followed to get there. The RSU is usually 
focused for increase in the angle of capture of the 
redirected energy. In thinner materials the lengths of 
the various paths are so short that they give the ap-
pearance of almost simultaneous occurrence; in thick-
er materials the various paths and modes can be 
separated and identified. The nature and operation of 
two Della configurations are explained; a Delta 
Wheel and a Manual Delta Probe. 
The defects of primary concern in weldments of 
aluminum alloys 2014 and 2219 have been detected at 
inspection rates of 50 ft/hr. An area lacking pene-
(continued o ennui) 
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tration and measuring 0.030 by 0.060 inch was reliably 
detected, as was an absence of fusion as narrow as 
0.025 inch Microfissuring, a laminar shrinkage-type 
defect found in 3/16-inch and 1/4-inch weld sections, 
was detected while radiographic techniques failed 
because of unfavorable orientation of defects. De-
structive analysis of 18 ft of weldment tested showed 
that 80% of total defects were detected by the Delta 
technique whereas only 36% were caught by radiog-
raphy. 
Note: 
The following documentation may be obtained 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65)
Reference: 
NASA-CR-6 1952 (N69-14207), Development 
of the Ultrasonic Delta Technique for Alumi-
num Welds and Materials 
Patent status: 
No patent action is contemplated by NASA. 
Source: B. T. Cross, K. J. Hanna and 
W. M. Tooley of 
Automation Industries, Inc. 
under contract to 
Marshall Space Flight Center 
(M FS-20824,-20843) 
Brief 70-10514 Category 08


Ultrasonic detection of flaws in fusion butt welds

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