Note: Descriptions are shown in the official language in which they were submitted.
This invention rela-tes -to -the nondestructive -testing
of materials by means of ul-trasonic waves and is clirected to
a method Eor detecting and locating nonhomogeneous areas in
a solid part. A particularly advantageous although non-
limitative application of -the method consists in measuring
-the hardening depth of steel par-ts. The invention is also
concerned with a device of suitable desi~n for carrying out
said method.
In the techniques of nondestructive testing of
materials, known methods already utilize the phenomena of
scattering of ultrasonic waves in materials. Especially in
the case of steel parts, these methods make it possible to
detect and locate structural variations resulting from a
heat treatment.
One conventional method consists in directing an
incident beam of ultrasonic waves onto the surface of a part
to be tested, in displacing said beam progressively along the
part and in observing the ultrasonic waves or echos which are
back-scattered from the part in respect of different success-
ive positions of the beam during displacement of this latter.
Broadly speaking, known methods have the disadvantage
of supplying information whlch cannot readily be utilized
under time conditions which are compatible with industrial
testing operations. Difficulties arise in particular from
the fact that no solution has yet been found for reconciling
the contradictory but essential requirements of rapidity and
precision, the amount of ultrasonic energy which is back-
scattered being liable to ~ary as much as the grain distribu-
tion in the part under inspection.
The present invention serves to facilitate non-
destructive testing of materials by means of ultrasonic waves
.
-2-
-' - ' '
: - : ' ''
and to make the techni~ue readily accessible Eor :induskrial
utilization.
The invention is directed to a method of non-
destructive testing of materials which makes it possible in
particular to measure the depth of hardening of steel and
: essentially consists in directing an incident beam of ultra-
sonic waves onto the surface of a test piece, in carrying out
a uniform displacement of the beam over the test piece at a
constant angle of incidence, in detecting the ultrasonic
waves back-scattered by the test piece and in visualizing on
a single receiver the energies of the successive waves which
are back-scattered during at least a predetermined fraction
of said displacement.
Preferably, the beam of ultrasonic waves is directed
onto the test piece at a constant oblique angle of incidence
in order to prevent the back-scattered waves from being masked
by the high-energy echo caused by the reflection of the waves
from the surface of the test piece. The angle of incidence
is advantageously larger than that which corresponds to the
~0 critical reflection of the longitudinal waves in order to -
ensure that only one beam of transverse waves is refracted
within the test piece. Especially in the case in which the
transmission of waves to the test piece takes place in water,
the angle of incidence is preferably of the order of 15 to 25.
. 25 In accordance with the invention, it is an advantage
to combine a local periodic displacement of the beam in the
vicinity of a mean point with a continuous displacement of
the mean point on the test piece. It is thus possi~le in
particular to combine a longitudinal movement of translation
at constant speed with a transverse reciprocating movement
of translation or with a continuous movement of rotation which
_3_
~`- - '- :'-. - .......... . .
- - :
,
is centered on the mean point such as a movement of conical
revolution of a beam havin~ an oblique angle of incidence.
These movements are preferably carr.ied out at constant speed.
In conjunction with the longiludinal displacement
of the beam~ it is an advantage to have recourse to a
particular mode of visual display of the energies of the
back-scattered waves whereby the energies which exceed a
predetermined threshold value are visualized on a screen as
a function of the longitudinal displacement. It is possible
in particular to employ the screen of a storage cathode-ray
tube and to control the spot deflection plates respectively
by means of a volta~e which is proportional to the longitudinal
displacement of the incident beam and by means of the time
base of the incident waves by modulating the intensity of the
spot by means of the energy of the detected back-scattered
waves.
However, the invention does not exclude the use of
other modes of visualization entailing the need for observa-
tion in stages along the surface of the test piece. In
particular, the variations in energy of the back-scattered
waves during a local periodic displacement of the incident
beam can be recorded on a single visual display screen, for
example by photographing the screen of a cathode-ray tube.
In this case, said displacement is preferably obtained by
means of a conical movement of revolution of the beam at
constant speed.
The invention is also concerned with a device for
: nondestructive testing of materials in which said device
essentially comprises means for emitting an incident beam of
ultrasonic wave trains, means for orienting sa.id beam at an
oblique angle of incidence with respect to the surfac2 of a
.
' - ~ . '' ~ ' "' ' "
~ - '- ' ~ ', ' .
~L~7~
test piece, means for detec-ting waves wh:Lch are back-
scattered by said test piece and preferably a-t the same angle,
sa.id detection means being provided if necessary with the
same transducer as the emission means, and means for dis~
placing the beam with respect to -the -test piece and maintain-
ing constant the angle of incidence and the len~th of the
acoustic path between the emission means and the sur~ace of
said test piece.
: Preferably, an emi.tting and/or receiving ultrasonic
transducer is mounted within a leak-tight apparatus closed by
a window in contact with the test piece and Eilled with an
acoustic couplant liquid such as water at least over the
enti.re acoustic path between the transducer and the window.
The apparatus advantageously contains not only the .
transducer but also beam-orienting means constituted especially
by at least one reflecting mirror and/or means for local dis-
placement of the beam especially by tran~lational or rotational -:
motion of the reflecting mirror and/or the transducer.
In one of the preferred embodiments of the device,
the transducer is mounted within a slide tube which is
capable of translational motion within the apparatus in a
direction parallel to the window. The beam is emitted in
an oblique direction through the window by the transducer
which is oriented in this direction or by an acoustic mirror
: 25 which i5 also mounted on the slide tube if the transducer
cannot be oriented in this direction. The slide tube can be
displaced in a reciprocating movement of translation either
by hand or preferably by means of an electric motor and a cam
against which the extremity of the slide tube is maintained
applied by means of a spring.
In another preferred embodiment of the cLevice, the
- , . .
--5--
.. .
-
,
~7V~
apparatus comprises a movable -transducer mounted on a movable
member designed to carry out a conical movement of revolution
of the beam produced by the -transducer which is oriented at
an oblique angle towards a point of the surface of the test
piece through -the window of the apparatus, or a stationary
transducer having an axis at right angles to the test piece
and a rotating system of reflecting mirrors for carrying out
the conical movement of revolu-tion of the beam at an oblique
angle towards a point of the surface of the test piece through
the window of the apparatus.
A more complete understanding of the invention will
be gained from the following description and from a study of
the accompanying drawings in which a few Pmbodiments of the
method and the device according to the present invention are
illustrated solely by way of example, and in which :
- Fig. 1 shows diagrammatically a first alternative
emhodiment of a device in accordance with the invention ;
- Fi~. 2 shows diagrammatically a second alternative
embodiment of the device ;
~ Fig. 3 shows a mode of displacement and a type of
visual display obtained by means of the alternative embodiment
of Fig. 1 ;
- Fig. 4A shows a mode of displacement and a type
of visual aisplay obtained hy means of the alternative
embodiment of ~ig. 2 ;
Fig~ ~B ~hows a mode of composite displacement
obtained b~ means o~ t~e alternative embodiment of ~ig. 2
and a corresponding type of visual display ,
- Fig. 5 is a longitudinal sectional view showing
an apparatus according to the invention in which the beam is
displaced in translational motion ;
.
--6
.~ . . - - . -
" - ' ' ' ~ ' ' "' , . .
~7~
- Fig. 6 is a transverse sec-tional view showing the
apparatus of Fig. 5 ;
- Fig. 7 is a diagrammatic view showing an assembly
which is employed for adjusting the apparatus ;
- Fig. 8 is a partial longitudinal sectional view
showing an apparatus according to the invention in which the
beam is displaced in rotational motion ;
- Fig. 9 is a longitudinal sectional view showing
an apparatus according to the invention with translational
displacement and an integrated displacement pickup ;
- Fig. 10 is a longitudinal sectional view showing
another apparatus in accordance with the invention comprising
an integrated displacement pickup in the case of displacement
in rotational motion.
In its application to the measurement of hardness
penetration of steel parts, the method according to the
invention is based on the observation of ul-trasonic waves
scattered by the part and more precisely on the observation
of variations in energy of the ultrasonic waves which are
scattered backwards by the grains of the material after
attenuation by these latter within the thickness of the part.
In fact, it is already known that in the case of a given part
corresponding to a predetermined mean volume of initial
austenite grains of the steel (prior to heat treatment),
scattering of the ultrasonic waves is much w~aker in a
martensitic structure as obtained by rapid cooling of steel
than in a pearlitic structure as obtained by slow cooling.
The degree of scattering is of intermediate value in the case
of stru~tures obtained with an intermediate cool:ing rate~
~owevex, the difference in scattering is usually sufficiently
well defined between the hardened steel layer and the
- -
~ -
-7-
.
unhardened portion to permit determination of the depth oE
the hardene~ layer, especially in the case of substantial
hardness penetrations obtained or example by high-frequency
treatment.
The me-thod according to the invention makes it
possible to observe this difference by making use of
particularly convenient means for establishing a mean value
of back-scattered energies over a predetermined fraction of
surface of the test piece and to measure directly in a
receiver for the visuali~ation of said energies the distance
between the surface of the test piece and the depth limit of
the hardened layer.
In the practical application of the invention,
preference is given to the use of a single transducer or
ultrasonic probe for emitting ultrasonic wave trains constit-
uting the incident beam which is directed onto the test
piece and for detecting the ultrasonic waves back-scattered
by the piece, or echos. However, in other forms of applica-
tion, the emission and detection can be carried out by means
of different probes. ~ ~
The different examples of device which will be -
described hereinafter all entail the use of a single probe.
Moreover, said probe is inclined or combined with suitable -.
devices so as to direct the beam of ultrasonic waves at an
~5 oblique angle of incidence onto the test piece and this angle
of incidence remains constant during a ~isplacement to which
the beam is subjected with respect to the surface of the test
plece while also maintaining constant the length of the
; acoustic path between the probe and the test pieceO
By virtue of the means which will be described later,
the beam is subjected to a local periodic displacement at a
-8-
. . - , .
.. .
~7~
uniform speed which can b~ ei-ther a reciproca-tin~ movem~nt
of translation or a continuous movement of rotation. This
local displacement is combined in some cases with a disp]ace-
ment of the mean point of the local displacement, which can
be either non-con-tinuous or continuous at a constant, low
speed with respect -to the local displacement.
The inclination of the angle of incidence of the
beam offers a number of advantages. In the first place, the
high-amplitude echo produced by reflection from the surface of
the test piece can thus be removed from the detection. Said
inclination also makes it possible in the case of an an~le of
incidence which is greater than the an~le of incidence
corresponding to the critical reflection of the longitudinal
waves to ensure that the transverse waves which have the
advantage of much lower velocity than longitudinal waves are
alone refracted within the test piece. Moreover, the fact that
the refracted beam is inclined increases the length of the
wave path within the thickness of the part being tested.
The devices which are shown diagrammatically in the
general views of Figs. 1 and 2 differ from each other in the
mode of visualization of the energies of the back-scattered
waves.
The device of Fig. 1 essentially comprises a wave-
train generator 1 which controls the emission of the probe 7.
Said probe produces a beam to which is imparted a periodic
local movement a~ove a test-piece holder 9 by mechanical means
which will be described hereinafter. In the ca~e of treatment
of si~nals corresponding to the back-scattered waves detected
by the probe 7~ the device comprises in series an amplifier 2,
a filter 3 and a detection unit 4 A visual display of the
si~nals is produced on the screen of a cathode-ray tube 5. The
_g _
,
.
amplitude of the echos detected con-trols the vertical
deflection plates of the cathode-ray tuhe whilst a tirne base
6 controls the horizontal deflection plates. It is thus
possible to obtain aEter adjustment of the time base in
synchronism with the emission of the incident beam a repre-
sentation of the variations in energy E of the echos as a
function of the distance D travelled by the ultrasonic waves
within the material.
In the case in which a part of hardened steel is
thus subjected to testing, the image is of the type shown in
Fig. 3. The device is advantageously provided in addition
with a camera which serves to record the energy curves
visualized on the screen of the cathode-ray tube throughout
the duration of the local displacement of the probe and thus
to display the mean curve of the energ~ scattered over a
; narrow integration range which is dependent on the amplitude
of displacement of the probe. The thickness of the hardened
steel layer cor~esponds to the distance between the first two .
echos of high amplitude ~H in ~ig. 3).
The device of Fig. 1 has a disadvantage in that it ..
provides the information in deferred time since it entails the
superimposition of a plurality of successive images without
permitting a geographlcal representation, the observed result
being a mean value between a number o~ points of the test
~5 piece.
The device shown in Fig. 2 circumvents these dis-
advantages and makes it possible in particular to establish
in real time a geoyraphical representation of the thickness
o~ the hardened layer o~ a steel part. As in the previous
case, this device comprises an ultrasonic wave-train generator
1, the probe 7 which is capable of moving in a direction
~ -
' " '. . ; ,.,~ : ' ' ~
~o~
parallel to a test-piece holder 9, an amplifier 2, a fil~er 3,
a detection unit ~, a cathocle-ray tube 5 and a -time base G.
'~he device differs from the previous embodiment in that the
local displacement of -the probe or even the complete dis-
placement of the apparatus if necessary is measured at eachinstant by means of an electrical device 8 which can be a
linear or rotational displacement pickup.
The voltage delivered by the device is proportional
to the displacement of the probe and controls the horizontal
deflection plates of the cathode-ray tube 5. The time base 6
controls the vertical de~lection plates in synchronism with the
emission of the incident beam whilst the detected signals
whose amplitude is characteristic of the back-scattered energy
are employed for modulating the light intensity of the spot
of the cathode-ray tube. There is thus obtained direGtly on
the screen of the cathode-ray tube a yeographical representa-
tion o~ the origln of the echos within the thickness of the
test piece as a function of the measured displacement of the
probe as shown in Figs. 4A and 4B which show the variations
in depth H of the hardened layer.
There will now be described in a number of different
embodiments the constr~ction of the mechanical portion o~
the device according to the invention at the level of the
ultrasonic probe and means for displacing the beam.
In these different alternative embodiments, a
single txansducer carries out the emission of the incident
beam of ultrasonic wave trains and the reception of the
waves which are back-scattered by the test piece. Said
transducer is mounted with means for orienting and displacing
the beam within the interior of a leak-tight apparatus
filled ~ith a liquid which provides acoustic couplill~ between
~ '~ . - -
,, ~ - -- .
-. ~ ~ ' - 11 , :
- .
.. ..
,
the transducer and the test piece and consists ~spec:ially oE
water.
In each case, said leak-tight apparatus is closed
by a window which permits transmission of the ultrasonic
S waves between the transducer or ultrasonic probe and the
surface of the test piece, the liquid beinc~ retained by a
thin flexible diaphragm which is transparent to ultrasonic
waves and placed over the window. Supporting and/or fixing
members serve to place the apparatus in position with the
flexible diaphragm applied in contact with the surface of
the test piece.
The ultrasonic beam can be directed obliquely
towards the window in order to obtain an oblique angle of
incidence which can be adjusted if necessary either by
inclinin~ the probe itself or by making use of systems for
reflecting the beam.
Local displacement of the beam can be obtained by
imparting a suitable movement to the probe or to reflecting
systems within the apparatus ; this can be carried out either
by hand or by means of a motor. This local displacement can
consist especially of a periodic movement of translation or
of rotation, thus making it possible to adopt either a mode
of visualization in accordance with Fig. 3 or a mode of
visualization in accordance with Fig. 4A as requirements
dictate. In addition, however, the apparatus itself can be
j displaced if necessary over the surface of the test piece in
order to carry out a composite mode of displacement of the
beam, thus permitting a mode of visualization i~ accordance
with Fi~. 4B~
The apparatus shown in Figs. 5 and 6 permits
rectilinear displacement o the probe and of a re:Electin~
- .. '-., ' - `- ' - . ,
- '
,, . '
7~7
mirror which ensures orierltation of -the beam. The ~pparatus
may be employed exactly as shown in the arrangement of Fig. 1
with a mode of rectilinear translational displacemen-t and a
mode of visualization in accordance with Fig. 3. The apparatus
can also comprise an additional external displac~ment pickup
(of the wire type, for example) and can be employed in the
arrangement of Fig. 2 with a composi-te mode of displacemen-t
consisting of two perpendicular movements of translation and
a mode of visualization in accordance with Fig. 4B.
The probe 40 and the mirror 43 are mounted within
a hollow cylindrical slide tube 42 which is in turn mounted
so as to be capable of translational motion in the axis of the
; cylindrical shell 41 of the apparatus. This latter also
contains a reduction-gear motor 23, the output shaft of which
is mounted in the axis of the slide tube and carries a cam 49
against which is applied the extremity of the slide tube 42 by
means of an antifriction bearing 24. The probe 40 is locked
; within the slide tube 42 by means of a piIl 48 which is screwed
in position at the end of this latter ; said pin serves to
support the bearing 24. The reflecting mirror 43 is p]aced
opposite to the probe within the slide tube and fastened by
means of a transverse locking-pin 37 which permits removal
and replacement of said mirror. A third member 12 is screwed
into the end of the slide tube. Said member has a blind-end
bore for accommodating a spring 38 which is applied against
the end-wal] 13 of the apparatus and thus urges the moving
system against the cam 49. The end portion of the shell 41 is
closed by a member 46 which is fixed in position by means of
screws 34 and also has the design function of maintaining the
spring-supporting end-wall 13.
Fine guiding of the slide tube is carried out by
;
- ..
~ -13-
. -
.
7~
means of bronze bearing-bushes 17 which are rigidly Eixed to
the shell 41 and by means of anti~riction bearings 27 which
not only serve to guide the moving system but also to prevent
rotation of this latter about its axis. Said bearings are
accordingly supported within a longitud:inal groove 21 formed
within the bore of the shell 41. The cross-pins 22 which
support the bearings 27 are displaced off-center and the
positioning of these latter serves to adjust the clearance
between the moving system and the shell. Screws 37 serve to
lock the cross-pins 22 in position.
The apparatus is designed to be ~illed in the
central portion thereof with a liquid which ensures acoustic
coupling between the probe and the surface of the test piece.
; Leak-tightness of the chamber which contains the
liquid is achieved :
- opposite to the openlng of the shell by means of a thin
flexible diaphragm ll which is transparent to ultrasonic
waves, said diaphragm being held in position by means of
a retaining ring 45 which is clamped against a recessed
diaphragm support 44 which limits the window ;
- between the shell and the slide tube by means of lipped
seals 25 ;
- between the probe and the slide tube and between the bearing
member of the spring 38 and the slide tube by means of 0-
ring seals 26 fitted within grooves which are machined in
the slide tube.
Filling o~ the chamber is carried out through an
opening formed in the shell which is closed by means of a
threaded plug 33 fitted with a seal 32. The chamber can be
put under pressure by screwing the member 12 into the slide
tube, this being accomplished by employing the key 14 which is
- - -14-
;--.. ;-,- ~ - ., '
,
placed across -the slots Eormed in the end--wall 13.
The slide tube is pierced by an opening at the level
of the probe through which are passed the leads for supplying
current to this latter. The leads are soldered to a socket-
outlet connector which is fixed on the external wall of theshell. There is placed at the end of the shell ~1 a right-
angled member 47, one portion of which is cut out on one side
so as to form a fork which serves as a support for fixing the
apparatus on the parts to be tested. Said member ~7 is fixed
in position by passing a screw 39 through a slot which permits
of height adjustment.
The mirror 43 may be dispensed with if necessary
if, in an alternative form of the preceding embodiment, the
probe 40 is modified so as to ensure that the sensitive
piezoelectric element is inclined at a sharp angle to the axis
of the slide tube and placed opposite to the window of the
apparatus.
Moreover, the mirror 43 can be replaced by a system
30 of complementary mirrors which is illustrated in Fig. 7.
This system serves to adjust the orientation of the plane of
incidence of waves at right angles with respect to the surface
of the test piece or with respect to the surface which is
tangent to the surface of the test piece 31. The complementary
mirrors are oriented so as -to return a fraction o~ the energy
reflected from the surface of the test piece to the emitting~
receiving probe 40. The adjustment is carried out by determin-
ing the orientation in which the reflected enexgy received by
the probe is of maximum value. Since the distance travelled
by the reflected waves is greater than the distance travelled
30 by the scattered waves, the respective echos are per ectly
separated when they are received on the viewing screen.
- ~ -
- - - -
-15
.......
- : -
~1~37~
In the apparat7~s of Fig. 8, a local displacement ofthe incident beam of ultrasonic waves is carried out by means
of a conical movement of revolution oE the beam.
Said apparatus can be employed in par-ticular
exactly as shown in the arranyement of Fig. 1 with a mode of
displacement in rotation and a mode of visualization in
accordance with Fig. 3. The apparatus can also be associated
with an additional ex-ternal displacement pickup (oE the wire
type, for example) in order to be employed in the arrangement
of Fi~. 2 with a composite mode of displacement of the beam,
; in local rotational motion and in translational motion, in
conjunction with a mode of visualization in accordance with
Fig. 4B.
The probe 50 is placed in the axis of a leak-tight
; 15 cylindrical shell 51 which terminates in a frusto-conical
portion 53 (the bottom portion shown in Fig. 8) comprising a
window which is perpendicular to the axis.
A rotating system comprising two mirrors for
reflecting the beam emitted by the probe is mounted in front
of this latter. A first mirror which is oriented at 45 degrees
to the axis of the probe reflects the beam radially ; then a
second mirror reflects said beam at an oblique angle with
respect to the axis towards the window of the apparatus. These
two mirrors are machined respectively in two steel members 57
and 56, these latter being assembled so as to form a
circular component which is mounted in a bored cylindrical
support 520 The support 52 is fixed on the rotor of a motor ~`
65 having a hollow shaEt, the probe 50 being located in the
axis of sald motor. This moving system is centered in the
cylindrical shell 51 by means of an antifriction bearing 66
which ensures the necPssary mobility without play.
- 16-
~g7(~
The apparatus is deslgned to be filled with a
liquid which ensures acoustic coupling between -the probe and
the test piece ; leak-tightness is ensured :
- at the level of the window by a thin flexible diaphragm 55
which is transparent to ultrasonic waves and held in posi-
tion by a clamp 54 ;
- between the probe and the shell by an 0-ring seal 64 which
is compressed by means of a nut 58.
Pressurization of the liquid in order to cause
deformation of the diaphragm is carried out by downward
displacement of the probe within the apparatus, locking being
obtained by tightening the nut 58.
The apparatus shown in Fig. 9 permits rectilinear
translational displacement of the emitting-receiving probe.
This apparatus differs from that shown in Figs. 5 and 6 in
the fact that it comprises a device for measuring the dis-
placement of the integrated probe. Said apparatus is advan~-
ageously employed exactly as shown in the arranyement of
Fig. 2 with `a mode of translational displacement and a mode
of visualization in accordance with Fig. 4A.
The probe 67 which is designed so as to ensure that
the sensitive piezoelectric element is steeply inclined to the
axis of the apparatus so as to emit the acoustic waves at an
oblique angle is mounted within the interior of a hollow
cylindrical slide tube 68 which is capable of moving within a
cylindrical shell 69. The slide tube 68 is actuated manually
by means of a member 70 on which it is engaged and maintained
by means of a locking-pin 71. A hollow cross-pin 72 fixed in
the shell 69 passes through a double slot formed in the
op~rating member 70 and thus makes it possible to prevent the
assembly of members 67, 68 and 70 from rotating about the axis
-17- -
. -. -: . .. :
.
~1~)7q~ 37
of the apparatus.
The displacement o -the men~ers 67, 68 and 70 in
linear translational motion is measured by means of a displace-
ment pickup 73 which is keyed i.n the mell~er 70 by means of an
end-cap 74. The movable pin of the displacement plckup is
: rigidly fixed to the shell of the apparatus which serves as
a reference in the positioning of the members 67, 68 and 70
: by virtue of a locking-pin 75.
An opening formed in the slide tube 68 and the shell
69 provides a passageway for the acoustic beam produced by
the probe ; the orientation of this latter is fixed by means
of a pin 76.
The apparatus is designed to be filled in the
central portion thereof with a liquid whi.ch ensures acoustic
` 15 coupling between the probe and the surface of the test piece. ~ .
; Leak-tightness of the chamber which contains the liquid is
. ensured :
- opposite to the opening of the shell and of the slide tube
by a thin flexible diaphragm 77 which is transparent to
ultrasonic waves and held in position by a retaining ring 78
which is clamped against a recessed diaphragm support
limited by the window ;
- between the shell and the slide tube and between the probe
: and the slide tube by means of 0-ring seals 790
2S Filling of the chamber is carried out from the slide
tube extremity which is closed by means of a threaded plug 80 ;
the greater or lesser engagement of this latter makes it
. possible to adjust the pressure within thP.chamber and con-
sequently the deformation of the flexible diaphragm 77.
El2ctrica1 connection o the probe is ensured by a connector
: 81 from which leads 82 extend to a socket-outlet 83 which is
18- .
. . ... .
.. - -, - ' , - ' ' -. :
also provided with -terminals joined to the leads Erom the
displacement pickup.
Provision is made Eor bearing members 8~ which
permit suitable positioning of the apparatus on the surface
of the part to be tested.
In the apparatus of Fig. lOr a local displacement
of the incident beam of ultrasonic waves is carriecl out by
means of a conical movement of revolution of the beam. This
apparatus differs from that shown in Fig. 8 essentially in
the fact that it comprises a device for measurin~ the displace-
ment o~ the integrated probe. Said apparatus is advantageously
employed exactly as shown in the arrangement of Fig. 2 with
a mode of displacement in rotational motion and a mode of
visualization in accordance with Fig. 4A.
The probe 85 is maintained by means of screws 87
in an oblique position within an eccentric hole formed in a
probe-holder 86 consisting of a cylindrical member o~ revolu-
tion. The probe-holder is mounted within a hollow shell
constituted by two sections 88 and 89 which are assembled
together by means o~ screws 90. A ball-bearing 91 serves to
support the probe-holder an~ this latter can accordingly be
subjected within the apparatus to a movement of rotation about
its axis. In consequence, a conical movement of revolution
about the axis o~ the apparatus can be imparted to the
2~ acoustic beam produced by the probe.
The movement of the probe 85 and of the probe-
holder 86 is controlled by a knurled ~nob 92 located outside
~he shell and secured by means of a screw 93 to the shaft o~
a potentiometer 9~ which is ~i~ed on the cover of -the
apparatus.
The apparatus is designed to be partly filled wi-th a
- " ' ' ' ' "
-19- ~ ~
, - .
. ~ . . - . : . : :
liquid whi.ch provides acoustic coupling between the probe and
the test piece ; leak-tightness is ensu:red :
- at the level of the window by a thin diaphragm 96 which is
transparent to ultrasonic waves and held in position by
a retaining ring 97 and an 0-ring seal 98 ;
- at the level of the assembly of the two sections 88 and 89
which constitute the shell of the apparatus by means of a
seal 99 ;
~ at the level of the axis of the probe-holder ~6 and of the
top portion of the shell 89 by means of a lipped seal lO0. ..
In order to produce the deformation of the diaphragm,
the liquid is put under pressure by means of a piston constit-
uted by an assembly of components and seals 101 to 106, the
position of which is defined by rotating the member 104. -
The probe 85 and the potentiometer 94 are connected
electrically, respectively to socket-outlets 107 and 108
which are fixed on the shell of the apparatus.
Within the field of application to the measurement
of hardness penetration in steel parts/ the apparatuses
described are utilized to advantage by adopting ultrasonic-
wave frequencies within the range of 5 to 20 Mc/s with wave-
train repetition fre~uencies of 2 kc/s, for example. In order
to permit direct reading of the hardness penetration, calibra
tion of the visual display and more precisely of the time base
~5 of the cathode-ray tu~e can be carried out by seekin~ to
obtain multiple echos of longitudinal waves in a Shim of
known thickne~s. If the measurements are then performed with
: different angles of incidence of the beam,. it is only . ~.
n~cessary to apply a corrective coefficient to the result
determined in accordance with the preliminary calibration.
: By way of example, this coefficient is respectively 0.~ ;
' ~ , ' ' ' '
. -.20-
. . .
,:
0.35 ; 0.3 in the case of angles of incidence of 18.5 ; 21 ;
or 23 degrees when the couplant liquid is water.
It is readily apparent that the invention is not
limited in any sense to the embodiments which have been
described in the foregoin~ with reference to the accompanying
drawings. Depending on the applications which are contem-
plated, consideration can be given to many possible alter-
native forms which are accessible to any one versed in the
art witho~lt thereby departing either from the scope or the
spirit of the invention.
.
. - :
