Ultrasonic flange radii inspection transducer device

A transducer device for an ultrasonic flaw detection system comprises a right angle rectangular block with one longitudinal edge being shaped to accurately conform to the curvature of the surface to be inspected. An ultrasonic sound wave beam in the block is reflected 90.degree. by a rotating mirror to cut a 360.degree. arc path through the surface to be inspected.

BACKGROUND OF THE INVENTION 
This invention relates to an improved ultrasonic flange radii transducer 
device, and more particularly to an improved transducer holder and 
mechanism particularly adapted for flange radii flaw detection or 
evaluation in radii non-metal composite, laminate materials. 
Non-metallic materials such as synthetic resins, ceramics, and composite 
materials containing resins and non-metallic filaments are finding wider 
applications in rotating machinery components such as hot gas turbine 
engine components. Many applications include important separate and 
individual parts manufactured from the noted materials. Composite 
materials components may be produced by combining layers of the material 
with a bonding medium and then curing the final product without any or 
minimal forming pressure or force. As a result the final product may 
include undesirable voids in the material as well as some delamination. In 
components having a 90.degree. flange or other corner angle, imposed 
stresses in the innermost corner of the angle become significantly more 
critical, particularly if material in the corner region contains flaws 
such as voids and delaminations. Ordinarily this innermost corner of an 
angle section includes a raised band or layer of the material with a small 
radius of curvature surface providing a smooth transition surface between 
the intersecting or joining surfaces defining the angle or corner. These 
small radii curve surfaces sometimes referred to as fillets or fillet 
regions are predetermined in size and shape to counter the high stress 
concentration usually found where surfaces sharply intersect. Consequently 
a flaw in the noted innermost corner material or fillet region becomes 
even more critical as a source or cause of premature failure. Because of 
the required high degree of precision and quality of hot gas turbine 
engines and associated components, the noted parts and components with 
angled surfaces are usually subjected to close and comprehensive 
inspection, with the result that various testing devices and systems have 
been developed for their flaw detection. Ultrasonic flaw detection systems 
have been found favorable for such inspections. In such a system an 
ultrasound wave is projected perpendicularly into, for example, the 
surface to be inspected. The sonic wave penetrates the surface and passes 
through the material of the part being inspected. As the sonic wave passes 
through the part material, all or part of the wave is reflected by flaws 
such as inclusions and discontinuities within the material. These 
reflections are sensed by a transducer and electronically processed to 
provide a visual and/or recorded interpretation of the flaws. 
Effectiveness of ultrasonic inspection systems as described is predicated 
on having a close coupling between the transducer and the inspecting 
surface, and having the projecting ultrasonic wave enter the surface in 
perpendicular relationship to maximize wave reflection and detection as 
well as the characteristics of a discovered flaw. In small radii surfaces 
such as the small radius interconnecting surface or fillet in the included 
angle between a pair of angled surfaces, a 90.degree. flange angle, for 
example, it has been difficult to provide means for continuously 
projecting an ultrasound beam radially and perpendicularly into the curved 
surface as well as incrementally and transversely along the curvature of 
the surface. It also has been a practice to provide sliding or rolling 
probes or transducers which move along the curved surface in contact 
relationship to closely follow the curve of as well as to provide close 
sound coupling with the surface. However, probes adapted to follow and 
couple with smaller radii curved surfaces represent a continuing problem 
of wave perpendicularity and close coupling. For this reason various 
ultrasonic devices and arrangements have been developed to obtain an 
optimum near perpendicular scan of small flange radii. In general these 
arrangements continue to include an ultrasound wave emitting transducer 
probe whether a rubbing probe, or a rotating ball or roller probe, 
together with appropriate mechanisms which attempt to couple, move, and 
guide the probe over the surface to be scanned while at the same time 
retaining a near perpendicular scan. Ultrasound coupling between the 
curved surface and the contacting probe, as well as obtaining a full and 
precise scan, together with real time display across the surface remain 
problem areas. 
OBJECTS OF THE INVENTION 
It is an object of this invention to provide an improved transducer holder 
for an ultrasonic defect detection system for small radii surfaces. 
It is another object of this invention to provide an improved rotating beam 
generating transducer holder for an ultrasonic defect detection system for 
small radii surfaces. 
It is a still further object of this invention to provide an improved 
rotating ultrasonic beam transducer holder for an ultrasonic defect 
detection system particularly adapted for flange radii inspection. 
SUMMARY OF THE INVENTION 
A transducer holder for an ultrasonic flaw detection system comprises a 
single ultrasonic transducer unit which generates and projects an 
ultrasonic beam into the device in a direction generally parallel to the 
surface to be inspected. Thereafter, a rotating mirror system in the 
device reflects the beam through 90.degree. for projection into the 
surface to be inspected, while rotating the beam through 360.degree. to 
cut a perpendicular slice through a flange radius. Improved coupling is 
achieved by having a curved surface of the holder which engages the curved 
surface to be inspected, be an accurate, corresponding and interfitting 
curved surface to the curved surface being inspected.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring now to FIG. 1, transducer holder 10 of this invention is 
illustrated in its operative position scanning a 90.degree. angle flange 
11. A cylindrical ultrasound transducer 12 is positioned concentrically at 
one end of a rectangular casing or block 13. Block 13 is an important 
feature of this invention serving two very important functions of (1) 
providing a tight sound coupling with the surface to be inspected, and (2) 
to incorporate components which generate and project a perpendicular sound 
wave into the surface to be inspected. The material of block 13 must be 
capable of a tight coupling with flange 11 to provide an uninterrupted and 
unaltered sound signal from transducer 12 into flange 11. To accomplish 
this purpose, block 13 must fully and closely match and engage the radius 
surface to be inspected as illustrated in FIG. 2. 
Referring now to FIG. 2, block 13 is illustrated in close nesting and 
interfitting relationship in angle 11. Block 13 fits in angle 11 with 
extensive planar surface to planar surface contact with arms 14 and 15 of 
angle 11, an arrangement which enhances ultrasound coupling between block 
13 and angle 11, as opposed to a ball or roller probe which may only have 
a very small spot or line contact with arms 14 and 15. A further important 
feature of rectangular block 13 is the curve of the rounded corner 16 
which is the corner fitting innermost in angle 11 and a twin to the small 
radius surface or fillet in angle 11. The matching curves and accompanying 
coupling provides increased accuracy of holder 10 as well as an improved 
pictorial display result of a test. Ordinarily, specifications for fillet 
regions are known and block 10 may be preformed for the part to be 
inspected. Block 13 is expeditiously produced from a synthetic resin 
material such as a polymethyl methacrylate, with commercially available 
derivations known by their trade names Lucite and Plexiglas. This material 
is easily shaped for an optimum curvature along the inspecting edge. 
Ultrasonic transducer 12 produces an ultrasonic sound wave which is 
Projected into block 13 and reflected to project into angle 11 as an arc 
traversing beam 17 in a specific manner as illustrated in FIG. 1. 
Referring again to FIG. 1, which is a schematic and longitudinal view of 
transducer holder 10 of FIG. 2, resin block 13 includes a hollow chamber 
or section 18 which contains a metal wedge reflector member 19. In one 
example wedge reflector member 19 is a cylindrical rod of stainless steel 
with a highly polished mirror surface 20 angled at 45.degree. with respect 
to the longitudinal axis of block 13 and sound beam 21 from transducer 12. 
Ultrasound transducer 12 and wedge member 19 are positioned and arranged 
so that ultrasound beam 21 is axially projected directly to mirror 20 and 
reflected through 90.degree. to penetrate angle 11 as beam 22. In order 
for beam 22 to scan the total radius to be inspected, beam 22 is provided 
with means for arc rotation. A small D.C. motor drive 23 is contained in 
an end section of block 13 opposite transducer 12, and wedge member 19 is 
mounted for coaxial rotation by shaft 24 of motor drive 23. Sound wave 22 
is thereby caused to traverse a full 360.degree. by rotation of wedge 
member 19 and the full 90.degree. angle of angle 11 is traversed in a 
close precise manner by the rotating beam 22 in a thin 360.degree. arc. 
The ultrasonic scanning beam provides a full 90.degree. scan of an angle 
as shown in FIG. 2 by the three inner position segments 17 of the beam 
penetrating perpendicularly into each surface being inspected while 
progressing across the 90.degree. arc. 
Ultrasound coupling is significantly enhanced by hollow chamber 18 being 
fluid filled with a good ultrasound transmitting fluid, for example, 
water. Water in chamber 18 may be referred to as an isolated water filled 
chamber, i.e. not connected to a water source or discharge for 
replenishment or flow. The capability of this invention to function with 
an isolated water filled chamber 18 contributes favorably to its 
manipulativeness and portability. The transmitted sound signal 22 enters 
the small radius surface in angle 11 accurately and perpendicularly along 
its radial arcuate path and is reflected by any anomaly between front and 
back surfaces. By monitoring those reflections, anomalies in the material 
are non-destructively detected. Monitoring usually includes sensing sonic 
wave reflections by the transducer and processing the reflections 
electronically for a visual display. In FIG. 1 electronic processing means 
are generally shown as box 25 appropriately electrically connected to 
transducer holder 10. Electronic systems for processing such reflected 
signals are noted in U.S. Pat. No. 4,807,476--Cook et al and may be 
included in processor 25 which also serves as a source of electrical power 
for holder 10 and its components. The foregoing procedure provides an 
extremely accurate but limited inspection of the small radius surface at 
one very limited position or cross-section. In order to obtain this kind 
of inspection transversely along the radius, transducer holder 10 is 
caused to move or index transversely while the 360.degree. scanning is 
occurring. Transverse movement is correlated with mirror 20 rotation so 
that, for example, one increment of transverse movement occurs for each 
360.degree. revolution of wedge member 19 and mirror 20. Further, a visual 
display in the usual manner on a CRT occurs for the cross-section 
inspected, and an optical encoder 26 (FIG. 1) is interconnected in the 
system to provide an operator or computer the positional feedback in 
degrees of angle, of wedge 19 and mirror 20 rotation. One example of an 
inspection of an angle 11 is illustrated in FIG. 3. 
Referring now to FIG. 3, visual plot 30 shows a pair of representative 
defects 31 and 32 in angle 11 of FIG. 1 as a C scan display. In order to 
obtain a faster scan of the small radius surface, a B-scan (brightness 
mode display) of the inspected surface is displayed for each cross-section 
inspected. To do this in real time, wedge member 19, and its mirror 20, is 
rotated at at least about 30 revolutions per second, 30 RPS, and 
transducer device 10 is caused to correspondingly slowly move 
transversely. This correlated movement together with a scanning display 
for each inspected cross-section (obtained by matched radii of the 
transducer holder 10 and the surface to be inspected) provides an improved 
ultrasound flaw inspection for various small radii surfaces in included 
angle regions, particularly enhanced by a 360.degree. perpendicular sweep 
of sound beam 22, and providing real time viewing of internal flaws. FIG. 
4 of this invention includes an example of a T.V. monitor or CRT display 
of a C scan display as well as a concurrent and faster B-scan a described. 
FIG. 4 is an operational view of a practice of this invention in 
combination with visual scan results. In an appropriate test procedure for 
FIG. 4, angle 11 was provided with certain programmed and predetermined 
hidden flaws or defects to be detected and visually displayed. For 
example, a series of flat bottom holes or apertures 33-35 were drilled 
angularly into the heel of angle 11 and in a row transversely along angle 
11 as illustrated in the 1--1 section of FIG. 4. Transducer assembly 10 of 
this invention is shown in its operative position in angle 11 and is moved 
transversely to scan along the small radius inner surface of the 
90.degree. angle 11. With appropriate electronic circuitry as described, a 
CRT C scan 36 is presented and shows that the programmed defects 33-35 
have been detected as well as angularly located. With coordinated mirror 
rotation (FIG. 1) and transverse movement of assembly 10, a B scan 37 is 
displayed. As illustrated in FIG. 4, B scan 37 provides an indication of 
the depth of defects 33-35. 
FIG. 4 is indicative of the essential difference between C scans and B 
scans. A C scan is a distance vs. distance or angle presentation while a B 
scan is a distance vs. depth or angle vs. depth presentation. A B scan can 
be compared to a scanned cross-section at a given plane along the angle 11 
which may be referred to in FIG. 4 as B scan X at an angle, for example, 
of 45.degree.. The cross-section for B scan O, presentation 38, of FIG. 4 
is a given position X along angle 11 and at 0.degree.-90.degree. angle. A 
C scan is a projection or plan view of the scanned area. 
This invention provides an improved transducer holder with a synthetic 
resin block or head having a curved surface which precisely fits 
coincident with the innermost part of an angle structure such as a 
90.degree. flange structure for a precise and accurate flaw inspection of 
the specific matched angle surface. The 360.degree. sonic wave sweep 
provides a wide range of inspection for angles less than and more than 
90.degree.. Accuracy of this invention requires a careful match between 
the contacting curvature of transducer and the curvature of the part to be 
inspected as well as an intervening material, i.e. block 13 as the holder 
contacting surface, which is effective to propagate a sound wave from an 
ultrasonic transducer into the surface to be inspected. 
By means of the improved single ultrasonic transducer of this invention, a 
more precise scan is obtainable on a known small radius of a flanged part 
or component. The improved transducer includes more precise coupling 
between the radius to be scanned and the transducer together with a larger 
angle faster scan with a real time visual display. 
While this invention has been described with respect to a preferred 
embodiment, it will be understood by those skilled in the art that various 
changes and modifications may be made without departing from the spirit 
and scope of the invention of the following claims.