Calibration technique detects minute laminar-type discontinuities in thin metal strip stock. Patterns of plastic tape are preselected to include minutely calculated discontinuities and the tape is applied to the strip stock to intercept the incident sonic beam

Peterson, R. M.

English

NASA Technical Reports Server

June 1967
	 Brief 67-10127 
AEC-NASA TECH BRIEF 
.P TES
.................................... 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
-	 -	 . 
Calibrating Ultrasonic Test Equipment for Checking Thin Metal Strip Stock 
Defect Indicated by drop  
in cinnI 170°L Ir !esslI	 -	 ...	 I 
Transducer - 
Lens 
Sonic Beam- 
Plastic Tape—, 
Strip Stock 
.	 r
Scope 
1 
- 
ReflectorJ1L_JnB?! 	 _] Gate
Reflector Signal
Necoroer I 
Adapter 
I	 I I	 Recorder	 L -	 IL.
rect 
nal 
The problem: 
It was desired to detect minute laminar-type discon- 
tinuities in thin metal strip stock. To ensure valid data 
from conventional ultrasonic test devices, a positive 
calibration technique was required that would not 
damage or destroy the strip stock. 
The solution: 
Patterns of plastic tape are preselected to include 
minutely calculated discontinuities and the tape is 
applied to the strip stock to intercept the incident 
sonic beam. 
How it's done: 
A transducer, the tape-treated strip stock, and re- 
flector are immersed in a water bath (not shown) and 
a pulsed sonic beam is focused to strike the plastic 
tape atop the thin metal strip stock, pass through the 
tape and strip stock and impinge on the reflector. At 
each interface between water and solid material, 
energy is lost from the incident sonic beam by reflec- 
tion that is a function of acoustic impedance mis- 
match at that point. The signal output from the
reflector is of principal interest. The gate in the 
scope is set on the reflector signal and receiver gain 
is adjusted to provide a 100% amplitude response in 
the recorder. The recorder adapter is adjusted to pro- 
vide continuous current to the recorder unless signal 
amplitude drops below a preselected level. With no 
discontinuities in the test sample, a dark line appears 
on the readout. Discontinuities are shown as breaks 
in the readout lines. 
Notes: 
1. This technique permits calibration to a sensitivity 
that senses laminar defects down to 0.0022 square 
inch in 0.012-inch strip stock. 
2. Prior to this innovation, the only methods avail- 
able for creating simulated discontinuities involved 
the use of chemical or electrode induced erosion. 
Both methods were time consuming, difficult to 
apply, and resulted in destruction of the strip 
stock. 
-	
-	 (continued overleaf) 
This document was prepared under the sponsorship of the Atomic liability resulting from the use of the information contained in this 
Energy Commission and/or the National Aeronautics and Space document, or warrants that the use of any information, apparatus, 
Administration. Neither the United States Government nor any per- method, or process disclosed in this document may not infringe pri-
son acting on behalf of the United States Government assumes any vately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19670000127 2020-03-11T20:45:24+00:00Z
3. Inquiries concerning this innovation may be di- 	 Patent status: 
rected to:
	
No patent action is contemplated by AEC or 
Technology Utilization Officer 	 NASA. 
AEC—NASA Space Nuclear Propulsion 	 Source: R. M. Peterson 
Office	 of Aerojet-General Corporation 
U.S. Atomic Energy Commission	 under contract to 
Washington, D.C. 20545	 Space Nuclear Propulsion Office 
Reference: B67-10127	 (NUC-1 0009) 
Brief 67-10127	 Category 01


Calibrating ultrasonic test equipment for checking thin metal strip stock

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