CA1118882A - Ultrasonic probe - Google Patents
Ultrasonic probeInfo
- Publication number
- CA1118882A CA1118882A CA000327084A CA327084A CA1118882A CA 1118882 A CA1118882 A CA 1118882A CA 000327084 A CA000327084 A CA 000327084A CA 327084 A CA327084 A CA 327084A CA 1118882 A CA1118882 A CA 1118882A
- Authority
- CA
- Canada
- Prior art keywords
- transducer
- transducers
- probe
- anomaly
- length
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2487—Directing probes, e.g. angle probes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/221—Arrangements for directing or focusing the acoustical waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2437—Piezoelectric probes
- G01N29/245—Ceramic probes, e.g. lead zirconate titanate [PZT] probes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/02854—Length, thickness
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/10—Number of transducers
- G01N2291/101—Number of transducers one transducer
Landscapes
- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- General Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Acoustics & Sound (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An ultrasonic probe is described, for use in a system for measuring the length of a reflecting anomaly in a workpiece. The probe operates to yield an output signal having elements therein directly related to the length of that anomaly, typically, a crack. The probe comprises a first transducer having a face for transmitting an incident beam of ultrasonic irradiation. A second transducer is provided, acous-tically non-coupled to the first transducer, and having a face for receiv-ing a portion of the incident beam reflected from an extremity of the anomaly. Directing means are connected to at least one of the transducers, causing the transducers to be oriented in a manner such that orthogonal projections of the transducer faces intersect to define a depth of field in which the extremity of the anomaly is locatable. A probe housing supports the transucers and the directing means. The housing also includes signal conducting means connectible to an ultrasonic source to drive the transmitting transducer, and to signal processing and displaying apparatus for processing the output signal and providing a read-out of the length of the anomaly. In a preferred embodiment, the directing means comprises two similar prisms joined together physically but non-coupled acoustically, with each prism serving to mount a related one of the transducers thereon.
In a still more preferred form, the transmitting transducer is of lead zirconate titanate, find the receiving transducer is of lead meta niobate.
The two transducer heads are provided in the one ultrasonic probe and measures the length of the reflecting anomaly from a generally "end-on"
orientation.
An ultrasonic probe is described, for use in a system for measuring the length of a reflecting anomaly in a workpiece. The probe operates to yield an output signal having elements therein directly related to the length of that anomaly, typically, a crack. The probe comprises a first transducer having a face for transmitting an incident beam of ultrasonic irradiation. A second transducer is provided, acous-tically non-coupled to the first transducer, and having a face for receiv-ing a portion of the incident beam reflected from an extremity of the anomaly. Directing means are connected to at least one of the transducers, causing the transducers to be oriented in a manner such that orthogonal projections of the transducer faces intersect to define a depth of field in which the extremity of the anomaly is locatable. A probe housing supports the transucers and the directing means. The housing also includes signal conducting means connectible to an ultrasonic source to drive the transmitting transducer, and to signal processing and displaying apparatus for processing the output signal and providing a read-out of the length of the anomaly. In a preferred embodiment, the directing means comprises two similar prisms joined together physically but non-coupled acoustically, with each prism serving to mount a related one of the transducers thereon.
In a still more preferred form, the transmitting transducer is of lead zirconate titanate, find the receiving transducer is of lead meta niobate.
The two transducer heads are provided in the one ultrasonic probe and measures the length of the reflecting anomaly from a generally "end-on"
orientation.
Description
l~iB158~:
This iilvention relates to irnprov~ments in ultrasonic probes. More particularly, the invelltiorl relates to an improved ultrasonic probe adapted for use in a crack detection system that provides a read-out directly o the length of a crack in a workpiece under study.
BACKGROUND OF THE INVE~TION
The detection of anomalies such as cracks and occlusions in a work-piece by ultrasonic testing has been known and practiced for a long time.
Of much greater difficulty, however, has been the problem of actually mea-suring the length or si~e of such anomalies non-destructively and directly in thé situations where the cracks cannot be examined "sideways" but must be monitored "head-on", i.e., with the direction of propagation of the probing ultrasooic beam parallel to the crack plane. The problem of detec-tion is further complicated in the situations when the crack thickness is very small and cracks are very straight and smooth. In these situations, the amount of ultrasonic energy reflected by the crack tip in "head-on"
detection configuration is very small and consequently the signal to noise ratio of the detected signal is small. A particular aspect of such diffi-culties has been the desire to enhance signal-to-noise ratios, and the desire to minimize the need for interpretation of signals read out, by an operator/technician. A problem frequently encountered in the prior art has been the level of background noise arlsing from scattering of the signal or from extraneous sources, which have masked partially or completely the magnitude and location of the reflected signal in the situations where the projection o~ the anomaly dimensions to a plane perpendicular to the dlrectlon o~ the ultrasonic beam propagation ls very small, e.g., very thin, straighc and smooch crack.
The ultra80nic probe described in this patent application is solvirlg the problern o~ signal-to-noise enhancement by improving the probe itself and using conventional ultrasonic equipment for detection of the improved signal. The other approach of using conventional probes and enhancing the signal-to-noise ratio electronically by using special ultrasonic detection equipment was described by Messrs. N.M. Bilgutay, E.S. Furgason and V.~.
- 1 - : ~
~ MR/I -.
~ewnouxe in 1.11. ~`r-u~ o ~_on Sonics arld ~ltrasonics, Vol. SU-23, No. 5, of September, 1976. The system there described, however, requires additional circuitr~ and circui~ elements to achieve the desired objective.
Nevertheless, the system of random signal E~aw detection o~ those authors does constitute a significant improvement. The ultimate enhancement of the &ignal-to-noise ratio of the de~ection rnethod would be achieved by combining both methods.
SU~MARY OF TE~ INVENTION
Applicant has further improved the art of ultrasonic flaw detection by providing an ultrasonic probe that is simple in both construction and use.
The probe and detection system described herein enhances signal-to-noise rstio of the flaw detection and eliminates the need for interpretation of output signals by an operator or technician. In this respect, applicant's invention becomes a useful tool for the laboratory studies of the fracture toughness of materials, of the growth of cracks or grain size, and the ; like. The need to interpret output signals has been minimized to promote reliability and consistency of the same. Moreover, applicant's invention is readily adaptable for real-life use in examining thick-walled tubes or workpieces, for instance, tubes, gun-barrels, or plate& of, say, 1 to 3"
in thickness. The applicant's ultra onic probe as described herein is susceptible to immediate use wlth prior art detection systems.
Thus, there is envisaged within the scope of the present invention an ultrasonic probe for use in a system for measuring the length of a reflecting anomaly in a workpiece, the probe being operative to yield an output signal having elements thereln which are directly related to the length of the anomaly, the probe comprisin~" a first transducer having a face for transmitting an inciden~ beam, a second transducer acoustically non-coupled to the first transducer, and having a face for receiving a portion of the incident ~eam reflected from an extremity of the anomaly, directing means connected to at least one of the transducers so as to cause the transducers to be oriented in a manner such that orthogonal projections MR/
ol (In cr.lllsd~lctr fa(~-- .inL<:rsec~ to clefine a depLh of field in which the e:;tr-rllity Ot ~ e aoolllal.y ;.-; locatable, and a housing for supporting the trar,sducers and the directing means, and including signal conducting mealls connectible to an ultrasonic source to drive the transmitting trans-ducer and to signal processing and disp].aying apparatus that provides a read out of said length of the anomaly.
In one preferred form of applicant's invention, the directing means comprises two similar prisms joined physically together by coupling plates and acoustical attenuating material disposed between the plates and the prisms thereby rendering the prisms acoustically non-coupled, each prism serving to mount a related one of the transducers.
In a preferred embodiment of this invention, there is provided, an ultrasonic probe for use in a system for measuring the length of a crack in a workpiece, the probe being operative to yield an output signal having elements therein which are directly related to the length of the crack, the probe comprising, a first transducer having a face for trans-mitting an incident beam, a second transducer acoustically non-coupled to the first transducer, and having a face for receiving a portion of the incident beam reflected from an extremity of the crack, directing means in the form of a pair of similar prisms, one prism being connected to a re-lated one of the transducers, causing the transducer faces to be so oriented that orthogonal projections of each transducer face intersect a].ong a line defining a depth of field in which the crack extremity is locatable, ~nd a housing supporting the directing means and transducers, flnd including signal conducting means connectible to an ultrasonic source for driving the transmitting transducer and to signal processing and dis-playing apparatus adapt.ed to provide a read-out of the crack length.
In yet a further preferred embodiment of this invention, the .
directing means comprises a pair of identically similar prisms disposed in mirror image symmetry with respect to a plane perpendicular to a plane containing a face of each prism opposite to the faces thereof on which ~IR/~
~ tl~ ',dl!C~I''i .lr~: IIIOUr'lt~`d, ~he plarle, in nse, b~in~ paraLlel to a workpiece fi~rface on wllich the prol~e is to be used.
The described prol)e operates equally weLl with the active plane of the probe, i.e., the plane definecl by two normals to the receiving and transmitting faces of the transducers, either parallel or perpendicular to the crack plane. This feature is especial]y important for detection of the cracks in specimens with curved surfaces (e.g. gun barrels) where the preferred probe orientation is with active probe plane parallelto the crack plane.
These and other features and advantages of this invention will become apparent from the detailed description below. That description is to be read in conjunctiOIl with Lhe accompanying drawings whicil illustrate by way of example only a number of embodiments of an ultrasonic probe as envisaged herein.
BRIEF DESCRIPTION OF THE DRAWI~GS
In the drawin8s:
- FIGURE I illusFrates schematically an elemental form of an ultra-soniC probe embodied by the present inven~ion;
FIGURES 2 and 2a illustrate graphically the visual display de-rived from the output of the probe of Figure l;
FIGURE 3 is an elevation view illustrating a preferred form of an ultrasonic probe as embodied by this invention;
FIGURES 4 and 4a, respectively, are side and end elevation views of a preferred embodiment of this invention;
FIGURE 5 is an exploded view of the construction of a transducer heacl of the type used in the embodiment of Figures 4 and 4a;
FIGIJRES 6 and 6a are elevation views taken in section through transducer heads of the type which, for example, are used in the ultrasonic probe of Figures 4 and 4a; and FIGURES 7 and 7a are elevation views taken in section to ; 30 clarify the constr~lction of ultrasonic decouplers as shown herein, while Figuré 7b shows a typical hook-up ~o ultrasonic equipment.
~' , lR/-~)L'`(:I~rr"rl()l~ 01' THr, PREFERRED E~IB(:)DIMI~NTS
l`url-ling now to Figure 1, an elementary form of the present ul~rasonic probe wl~ll the active plane oi the probe perpendicular to the crack plane is shown overall at 10. The probe 10 comprises a housing 12 which contalrls two trallsducer heads 14 and 16. The transducer 14 in this instance, is mounted on directing means in the fonn of a prism 18, while the transducer 16 is supported directly on a selected surface 20 of a test specimen workpiece 22 under study. The transducers 14 and 16 have faces 24 and 26, respectively, whose orthogonaL projections interesect 10 along a line which defines a depth of field D~, shown at 28. It will be evident that the depth of field is at depth in the workpiece 22 so as to enable a suspected or known anomaly 30 to be locatable within it. The anomaly 30 is typically a crack, but could also represent an occlusion or even a grain of the ~orkpiece 22. In Figure 1, the crack 30 extends from a machined or cut slot 32 formed deliberately in the test specimen workpiece 22. In real-life conditions, of course, the slot 32 would probably not exist, or it wouId at best be a pit created by corrosion, .
spalling, or the like.
~igure 1 shows the orientation of face 24 of the transducer 14 20 as being at an angle ~ from the plane of workpiece surface 20, i.e., the plane also containing face 26 of transducer 16 and face 34 of the prism 18. The face 34 is opposite to a prism face 36 against which the trans-ducer 14 is in intimate contact. It will further be seen from Figure 1, that the siY.e, i.e., the length, of the depth of field ~ can be varied ':
by varyirlg parameters s~lch as tlle an~gle ~ or the diameter of the transducer faces 24 and 26. Spacing S is the o~f-set of the centre of transducer ....
face 24 from an axis extending orthogonally of the workpiece surface 20, t , and passing througll the tip of the crack 30, i.e" through an extremity of , that anomaly. Varylng S alteræ the dep~h at which the field Df is located.
30 The rffects of varying any one or combination of these parameters can also be seen from ~igure 3, to be described below.
_5_ .
MR/
111~ 32 Therc are rwo aspects of the arrangement shown in Figure I
which are important. First]y, the two transducer heads 14 and 16 are acoustically non coupled. Secondly, the tran~sducer heads 14 and 16 must be in intimate contact with the workpiece surface 20 with the face of the prism 18 on which transducer 14 is mounted, and prism face 34 must intimately contact workpiece surface 20. Such contact minimizes scattering of both incident and reflected beams crossing any of such interfaces. Also, prism 1~3 is of a material which is acoustically well matched to the material of the test specimen such that the ultrasonic transmission is maximized and beam reflection and conversion at the prism specimen interface is minimized.
~; As an example, if the measured workpiece is steel (e.g. gun ~arrel) the prism 18 is also of steel. Further yet, the transducer faces 24 and 26 usually have wear plates bonded to them. Such wear plates are best seen in Figs.
6,6a, 7, and 7a, and preferably are made of material with acoustical impedance ; whose magnitude is in between the magnitudes of the acoustical impedance of workpiece and the acoustical impedance of the transducer material. In a specific example when the workpiece is made of steel and transducer material is lead meta niobate or lead zirconate titanate, the suitable wear plate material is brass. As is well known in this art, a wear plate not only protects the transducer material physically, but also improves the acoustical mpedance matching between the transducer and the workpiece.
In operation, one of the transducers 14 or 16 is driven from an ultrasonic genera~or, or source. The driven transducer generates a beam of ultrasonic lrrfldiation which is transmitted into the workpiece 20~ The irradiflting beam incident upon a discontinuity in the form of an interface~
an anomaly or back ;Eace of the workpiece 20 is scattered and/or reflected, at least in part. In accordance with one aspect of this invention, trans-ducer 14 functions as the transmitting transducer, with the face 2~ thereof transmitting an incident beam 3~3. The transducer 16 functions as the receiving transducer~ The inverse configuration when transducer 16 acts as a transmitter and transducer 14 is a receiver is also acceptable.
MR/~
~l~tloug~l Llle l)cam 3~ is ill~l;trated as a collimated beam, it will in reality ~je somewhat divergcnt (38'~. In any evel-t, portions of the incident beam 38 are re~lected from parts o~ the anomaly 30 and slot 32, for example, the tlps or extremitles of each. A reflected beam 40 is formed and received by the face 26 of the receiving transducer 16. The latter generates an output signal carried by electrical circuit means in the probe 10 to signal processing and display apparatus, not shown. Such apparatus is conventionaL in this art and need not be described in detail here. For example, a conventional ultrasonic pulser/receiver is used to display an output trace of the signal generated in the receiving transducer 16 from echo pulses received by it. See Figures 2 and 2a. The output trace contains elements therein, shown as spikes or "blips" which are caused by echo pulses reflected from anomalies in the workpiece. Thus, one echo pulse may represent the signal reflected from the crack tip, while a subsequent spike (i.e., echo pulse) represents the reflection of another portion of the incident beam 38 from the tip of the cut 32 (or back surface of workpiece 22, as the case may be); The distance between such pulse echoes is the length of the crack 30, assuming the ultrasonic pulserlreceiver has ,.
been suitably calibrated. Any subsequent pulses occurring after the pulse from the tip of the cut 32 or back surface of workpiece 22 may be disregarded because they represent the reflections due to combinations of shear and t longitudinal waves or multiple reflections of longitudinal waves. All informarion about the crack length is contained in the first two u]trasonic ~ pulses.
; Figure 2 represents the actual trace seen on an ultrasonic pulser/receiver screen as an output signal frorn the ultrasonic probe 10 of Fi~ure l. Figure 2a illustrates schemAtically the identifiable contents of the trace of Figure 2, and indicates how the length of the anornally 30 is derived or extracted therefrolll. Clearly, once the ultrasonic pulser/receiver 30 i$ calibrated, the distance between various spikes or "blips" on the ultra-sonic pulser/receiver trace is a rneasure of the actual spacin~ between MRI
8~132 ii~f~re[~ oi~ ol anolllali(s in thc wor'cpiece that gave rise to the echo pulses rel)resell~ecl by those ~pikes.
As arl alternativt-~ to ~he ultrasonic pulser/receiver, not shown, the signal processillg and display apparatus could comprise a digital counter with circuitry which converts Lhe time delay between subsequent echo pulses to an output clispLay in digital forl~, indicative of the distance between the two anoTnalies or portions thereof which generated the t~o echo pulses.
Figure 3 represents an ultrasollic probe 50 which includes sorne variations to the probe 10 described above. The probe is shown in the con-figuration where the active plane of the probe is paral]el to the plane of the crack. ~As it wou]d be e.g. during the crack measurement in the gun barrels. The workpiece shown in Figure 3 represents the cross-section through gun barrel, cut being in the plane of the crack and parallel to the gun barrel axis). The probe 50, for example, uses directing means in the form of a pair of similar prisms 52 and 54 carried in a housing 53.
The prisms 52 and 54 are acoustically non-coupled by virtue of an air gap 56 between them. Prism 52 supports a transmitting transducer 58, while the prism 54 supports a receiving transducer 60. As in the previous embodi-ment, the prisms 52 and 54 of Figure 3 cause the transducers 58 and 60 to have orthogonal projections of faces 62 and 64 thereof~intersecting along a line defining a depth of field of the probe 50. One e~tremity 66 of a crac~ 68, i.e., an anomaly, ;s seen to be locatable in the depth of field of the probe 50, in fl curved workpiece 70.
Figure 3 shows that the angles of inclination ~ of each trans-ducer ~8 and 60 dif~er. The dcpth of field of the probe 50, thus, is variable by varyillg certain parameters above, elther singly or in combina-tion. Further yet, it has been found that because of differences in the characteristics of transducer materials functioning in the transmit, and receive modes, optimum results were obtained when the transmitting trans-ducer was of lead ~irconate titanate (PZT) while receiving transducer was of lead meta niobate (PMN).
Al ~l~o~ n(.)t: Ld~ ^!n ~ ~r,~ sd~lc~rs 58 ancl 50 each i~ave brass wear !~]a~ l)olldecl ~n~ Lh~ f;~c~ 62 and t;~:. The transducers are operated, for e~aml)le, a~ frccl~lenc:if s of 2 MHi:, 4 Mll% or 8M~Iz and typically have a face diameter in the range of 0.95 cm to 2.5 cm (0.375" to 0.75"). The wear plate thickness is abou~ one (luar~er of the wave length oi the ultrasonic irradiation, being about 0.027 c:m (.011") when a 4 M11z source is used.
Operation at 4 MHz proved to exhibit best signal-to-noise ratio.
In use, the probe 50 is connected to an ultrasonic generator whicll drives the transducer 58, and to an ultrasonic receiver, for example, ]0 to process and display as a read-out trace the output signal of the receiving transducer 60. That output signal inc]udes elemellts therein representing the echo pulses or reflections of an incident bearn from extremity 66 and the back face of the workpiece 76. The time of arrival of these echo pulses is a function of ~he velocity of sound through the materiaLs of the prisms 52 and 54 and workpiece 70, and the path length travelled by the beams.
Such output traces typically resemble those shown in Figures 2 and 2a.
Again, the spacing and amplitude of echo pulses or spikes is dependent upon the variables just noted, and on the homogeneity of the workpiece, and the intensity of the reflected signal. The latter is itself`dependent upon the reflecting properties of the anomaly. The split prism arrangement of probe 50 has been found to work in configurations where the plane of the crack or anomaly is either parallel,or perpendicular to the plane of the ultrasonic beams.
Figures 4 and 4a show at 80 a preferred embodiment Oe an ultra-sonic probe flccording to this inventiorl. The probe 80 comprises a housing 82 in which ~here is a pair Oe transducers 84 and 86. The transducers 84 and 86 are mounted in intimate contact wiLh directing means in the form of a pair of identically similar pri~sms 88 and 90. I`hese prisms 88 and 90 have faces 92 and 94, each inclineci at an angle ~ (here about 19-20) to the plane of a surface 96 oE a worlcpiece 98. Faces 100 and 102 of prisms 88 and 90 are opposite LO the inclined iaces 92 and 94 thereof. The faces MR/
.
3E~Z
i()() u~(l 10, ale co!]an~ !, th~ workl)i((e surfacc (3¢? ~'llld in intiillate COIl-act witll lh( s.~ e.
The hou~ill, 82 is typically rmade of aluminum, while prisms 88 and 90 Ire rnaclc of ST eel. The trar-lsducer heads 84 and 86 are constructed in a marlner to be describecl below, relative to Figures 5, 6 and 7 and conml(>nly aIe circular, and preferably in the range of 3/8"-1" in diameter.
As best seen in Figure 4a, the prisms o8 and 90 are joined phys;cally together by rnearls of a sandwiched arrangement of plastic attenu-ating plates 104 bonded to steel mounting plates 106 and fln alurninum mount-ing bracket 108. Thus, the prisms 88 and gO are acoustically non-coupled.
An optional steel spacer 110 is provided as required. The details of a particular construction of the attenuating plates are shown in Figure 7, where the top view of prisms, alternating plates and strengthening steel strips are shown. These items 104, 106, 108 and 110 are provided with aligned bore holes which accomodate threaded fastener screws 112 for secur-ing the prism assembly to the housing 82. The bracket 108 has an arm 114 also formed with a bore hole. That bore hole is internally threaded, and in one instance may secure the transducer probe 80 to a positioning bracket or arm, not shown, and used, for exami~le, in instances whère the workpiece 98 is movable relative to the probe 80. A]ternati:ely, the arm 114 may be equipped with a threaded stud 71 which i9 movable longitudinally tllereof, to accomodate use of the probe 80 with a curved sùrface specimen, i.e., to prevent rocking of the probe on the workpiece surface. Note that it is higilly desirable Eor the worlcpiece sur-Eace to be free of paint etc. in these regions where probe reaclings are taken.
In Figures 5 and 6, a transducer head 120 is seen to comprise fl tr.,311sclucer elemellL 122 in the form of a f]at ceramic wafer, enclosed by backing materi;31 124 within an inslllating collar 126. The collar 126 i9 i~self received within a tubular brass enclosure 128, whicil may or may not be threaded exteriorly. The back face of enclosure 128 is closed by a printed circuit board 132 which has circuit elements 134 and contacts 136 .
~R/
8~2 thereon as requircd. Sce l;igures 6 al-)d 6a. Electrical conducting means 138 connect Lhe transduc~r eLement 122 to the circuit board 132. A thin layer of gold is often evaporated onto the transducer's front face to pro-vide good electrical contact: between the probe enclosure 128 and the trans-ducer front face. A wear plate 142 is bonded to the gold layer 140. In the case of Figure 6a where a "wrap-around" transducer elernent 122 is used, that element is bonded to the brass enclosure 128 by an electrically con-ductive adhesive or bonding rnaterial. A layer of gold 140 need not be used in that form of transducer head 120.
Figure 7b shows a typical hook-up using an ultrasonic probe as described therein. The ultrasonic pulser/receiver is any one of the units available commercially, i.e., Krautcrarner Unit USIP II, Sonic UWA
Mark III, etc.
- The foregoing has described both generically and specifically a number of embodiments of this invention. Some alternative conligurations have been suggested. It is therefore envisaged by this invention to include all such changes and modifications as fall within the scope of the claims below.
MR/~l~
.
This iilvention relates to irnprov~ments in ultrasonic probes. More particularly, the invelltiorl relates to an improved ultrasonic probe adapted for use in a crack detection system that provides a read-out directly o the length of a crack in a workpiece under study.
BACKGROUND OF THE INVE~TION
The detection of anomalies such as cracks and occlusions in a work-piece by ultrasonic testing has been known and practiced for a long time.
Of much greater difficulty, however, has been the problem of actually mea-suring the length or si~e of such anomalies non-destructively and directly in thé situations where the cracks cannot be examined "sideways" but must be monitored "head-on", i.e., with the direction of propagation of the probing ultrasooic beam parallel to the crack plane. The problem of detec-tion is further complicated in the situations when the crack thickness is very small and cracks are very straight and smooth. In these situations, the amount of ultrasonic energy reflected by the crack tip in "head-on"
detection configuration is very small and consequently the signal to noise ratio of the detected signal is small. A particular aspect of such diffi-culties has been the desire to enhance signal-to-noise ratios, and the desire to minimize the need for interpretation of signals read out, by an operator/technician. A problem frequently encountered in the prior art has been the level of background noise arlsing from scattering of the signal or from extraneous sources, which have masked partially or completely the magnitude and location of the reflected signal in the situations where the projection o~ the anomaly dimensions to a plane perpendicular to the dlrectlon o~ the ultrasonic beam propagation ls very small, e.g., very thin, straighc and smooch crack.
The ultra80nic probe described in this patent application is solvirlg the problern o~ signal-to-noise enhancement by improving the probe itself and using conventional ultrasonic equipment for detection of the improved signal. The other approach of using conventional probes and enhancing the signal-to-noise ratio electronically by using special ultrasonic detection equipment was described by Messrs. N.M. Bilgutay, E.S. Furgason and V.~.
- 1 - : ~
~ MR/I -.
~ewnouxe in 1.11. ~`r-u~ o ~_on Sonics arld ~ltrasonics, Vol. SU-23, No. 5, of September, 1976. The system there described, however, requires additional circuitr~ and circui~ elements to achieve the desired objective.
Nevertheless, the system of random signal E~aw detection o~ those authors does constitute a significant improvement. The ultimate enhancement of the &ignal-to-noise ratio of the de~ection rnethod would be achieved by combining both methods.
SU~MARY OF TE~ INVENTION
Applicant has further improved the art of ultrasonic flaw detection by providing an ultrasonic probe that is simple in both construction and use.
The probe and detection system described herein enhances signal-to-noise rstio of the flaw detection and eliminates the need for interpretation of output signals by an operator or technician. In this respect, applicant's invention becomes a useful tool for the laboratory studies of the fracture toughness of materials, of the growth of cracks or grain size, and the ; like. The need to interpret output signals has been minimized to promote reliability and consistency of the same. Moreover, applicant's invention is readily adaptable for real-life use in examining thick-walled tubes or workpieces, for instance, tubes, gun-barrels, or plate& of, say, 1 to 3"
in thickness. The applicant's ultra onic probe as described herein is susceptible to immediate use wlth prior art detection systems.
Thus, there is envisaged within the scope of the present invention an ultrasonic probe for use in a system for measuring the length of a reflecting anomaly in a workpiece, the probe being operative to yield an output signal having elements thereln which are directly related to the length of the anomaly, the probe comprisin~" a first transducer having a face for transmitting an inciden~ beam, a second transducer acoustically non-coupled to the first transducer, and having a face for receiving a portion of the incident ~eam reflected from an extremity of the anomaly, directing means connected to at least one of the transducers so as to cause the transducers to be oriented in a manner such that orthogonal projections MR/
ol (In cr.lllsd~lctr fa(~-- .inL<:rsec~ to clefine a depLh of field in which the e:;tr-rllity Ot ~ e aoolllal.y ;.-; locatable, and a housing for supporting the trar,sducers and the directing means, and including signal conducting mealls connectible to an ultrasonic source to drive the transmitting trans-ducer and to signal processing and disp].aying apparatus that provides a read out of said length of the anomaly.
In one preferred form of applicant's invention, the directing means comprises two similar prisms joined physically together by coupling plates and acoustical attenuating material disposed between the plates and the prisms thereby rendering the prisms acoustically non-coupled, each prism serving to mount a related one of the transducers.
In a preferred embodiment of this invention, there is provided, an ultrasonic probe for use in a system for measuring the length of a crack in a workpiece, the probe being operative to yield an output signal having elements therein which are directly related to the length of the crack, the probe comprising, a first transducer having a face for trans-mitting an incident beam, a second transducer acoustically non-coupled to the first transducer, and having a face for receiving a portion of the incident beam reflected from an extremity of the crack, directing means in the form of a pair of similar prisms, one prism being connected to a re-lated one of the transducers, causing the transducer faces to be so oriented that orthogonal projections of each transducer face intersect a].ong a line defining a depth of field in which the crack extremity is locatable, ~nd a housing supporting the directing means and transducers, flnd including signal conducting means connectible to an ultrasonic source for driving the transmitting transducer and to signal processing and dis-playing apparatus adapt.ed to provide a read-out of the crack length.
In yet a further preferred embodiment of this invention, the .
directing means comprises a pair of identically similar prisms disposed in mirror image symmetry with respect to a plane perpendicular to a plane containing a face of each prism opposite to the faces thereof on which ~IR/~
~ tl~ ',dl!C~I''i .lr~: IIIOUr'lt~`d, ~he plarle, in nse, b~in~ paraLlel to a workpiece fi~rface on wllich the prol~e is to be used.
The described prol)e operates equally weLl with the active plane of the probe, i.e., the plane definecl by two normals to the receiving and transmitting faces of the transducers, either parallel or perpendicular to the crack plane. This feature is especial]y important for detection of the cracks in specimens with curved surfaces (e.g. gun barrels) where the preferred probe orientation is with active probe plane parallelto the crack plane.
These and other features and advantages of this invention will become apparent from the detailed description below. That description is to be read in conjunctiOIl with Lhe accompanying drawings whicil illustrate by way of example only a number of embodiments of an ultrasonic probe as envisaged herein.
BRIEF DESCRIPTION OF THE DRAWI~GS
In the drawin8s:
- FIGURE I illusFrates schematically an elemental form of an ultra-soniC probe embodied by the present inven~ion;
FIGURES 2 and 2a illustrate graphically the visual display de-rived from the output of the probe of Figure l;
FIGURE 3 is an elevation view illustrating a preferred form of an ultrasonic probe as embodied by this invention;
FIGURES 4 and 4a, respectively, are side and end elevation views of a preferred embodiment of this invention;
FIGURE 5 is an exploded view of the construction of a transducer heacl of the type used in the embodiment of Figures 4 and 4a;
FIGIJRES 6 and 6a are elevation views taken in section through transducer heads of the type which, for example, are used in the ultrasonic probe of Figures 4 and 4a; and FIGURES 7 and 7a are elevation views taken in section to ; 30 clarify the constr~lction of ultrasonic decouplers as shown herein, while Figuré 7b shows a typical hook-up ~o ultrasonic equipment.
~' , lR/-~)L'`(:I~rr"rl()l~ 01' THr, PREFERRED E~IB(:)DIMI~NTS
l`url-ling now to Figure 1, an elementary form of the present ul~rasonic probe wl~ll the active plane oi the probe perpendicular to the crack plane is shown overall at 10. The probe 10 comprises a housing 12 which contalrls two trallsducer heads 14 and 16. The transducer 14 in this instance, is mounted on directing means in the fonn of a prism 18, while the transducer 16 is supported directly on a selected surface 20 of a test specimen workpiece 22 under study. The transducers 14 and 16 have faces 24 and 26, respectively, whose orthogonaL projections interesect 10 along a line which defines a depth of field D~, shown at 28. It will be evident that the depth of field is at depth in the workpiece 22 so as to enable a suspected or known anomaly 30 to be locatable within it. The anomaly 30 is typically a crack, but could also represent an occlusion or even a grain of the ~orkpiece 22. In Figure 1, the crack 30 extends from a machined or cut slot 32 formed deliberately in the test specimen workpiece 22. In real-life conditions, of course, the slot 32 would probably not exist, or it wouId at best be a pit created by corrosion, .
spalling, or the like.
~igure 1 shows the orientation of face 24 of the transducer 14 20 as being at an angle ~ from the plane of workpiece surface 20, i.e., the plane also containing face 26 of transducer 16 and face 34 of the prism 18. The face 34 is opposite to a prism face 36 against which the trans-ducer 14 is in intimate contact. It will further be seen from Figure 1, that the siY.e, i.e., the length, of the depth of field ~ can be varied ':
by varyirlg parameters s~lch as tlle an~gle ~ or the diameter of the transducer faces 24 and 26. Spacing S is the o~f-set of the centre of transducer ....
face 24 from an axis extending orthogonally of the workpiece surface 20, t , and passing througll the tip of the crack 30, i.e" through an extremity of , that anomaly. Varylng S alteræ the dep~h at which the field Df is located.
30 The rffects of varying any one or combination of these parameters can also be seen from ~igure 3, to be described below.
_5_ .
MR/
111~ 32 Therc are rwo aspects of the arrangement shown in Figure I
which are important. First]y, the two transducer heads 14 and 16 are acoustically non coupled. Secondly, the tran~sducer heads 14 and 16 must be in intimate contact with the workpiece surface 20 with the face of the prism 18 on which transducer 14 is mounted, and prism face 34 must intimately contact workpiece surface 20. Such contact minimizes scattering of both incident and reflected beams crossing any of such interfaces. Also, prism 1~3 is of a material which is acoustically well matched to the material of the test specimen such that the ultrasonic transmission is maximized and beam reflection and conversion at the prism specimen interface is minimized.
~; As an example, if the measured workpiece is steel (e.g. gun ~arrel) the prism 18 is also of steel. Further yet, the transducer faces 24 and 26 usually have wear plates bonded to them. Such wear plates are best seen in Figs.
6,6a, 7, and 7a, and preferably are made of material with acoustical impedance ; whose magnitude is in between the magnitudes of the acoustical impedance of workpiece and the acoustical impedance of the transducer material. In a specific example when the workpiece is made of steel and transducer material is lead meta niobate or lead zirconate titanate, the suitable wear plate material is brass. As is well known in this art, a wear plate not only protects the transducer material physically, but also improves the acoustical mpedance matching between the transducer and the workpiece.
In operation, one of the transducers 14 or 16 is driven from an ultrasonic genera~or, or source. The driven transducer generates a beam of ultrasonic lrrfldiation which is transmitted into the workpiece 20~ The irradiflting beam incident upon a discontinuity in the form of an interface~
an anomaly or back ;Eace of the workpiece 20 is scattered and/or reflected, at least in part. In accordance with one aspect of this invention, trans-ducer 14 functions as the transmitting transducer, with the face 2~ thereof transmitting an incident beam 3~3. The transducer 16 functions as the receiving transducer~ The inverse configuration when transducer 16 acts as a transmitter and transducer 14 is a receiver is also acceptable.
MR/~
~l~tloug~l Llle l)cam 3~ is ill~l;trated as a collimated beam, it will in reality ~je somewhat divergcnt (38'~. In any evel-t, portions of the incident beam 38 are re~lected from parts o~ the anomaly 30 and slot 32, for example, the tlps or extremitles of each. A reflected beam 40 is formed and received by the face 26 of the receiving transducer 16. The latter generates an output signal carried by electrical circuit means in the probe 10 to signal processing and display apparatus, not shown. Such apparatus is conventionaL in this art and need not be described in detail here. For example, a conventional ultrasonic pulser/receiver is used to display an output trace of the signal generated in the receiving transducer 16 from echo pulses received by it. See Figures 2 and 2a. The output trace contains elements therein, shown as spikes or "blips" which are caused by echo pulses reflected from anomalies in the workpiece. Thus, one echo pulse may represent the signal reflected from the crack tip, while a subsequent spike (i.e., echo pulse) represents the reflection of another portion of the incident beam 38 from the tip of the cut 32 (or back surface of workpiece 22, as the case may be); The distance between such pulse echoes is the length of the crack 30, assuming the ultrasonic pulserlreceiver has ,.
been suitably calibrated. Any subsequent pulses occurring after the pulse from the tip of the cut 32 or back surface of workpiece 22 may be disregarded because they represent the reflections due to combinations of shear and t longitudinal waves or multiple reflections of longitudinal waves. All informarion about the crack length is contained in the first two u]trasonic ~ pulses.
; Figure 2 represents the actual trace seen on an ultrasonic pulser/receiver screen as an output signal frorn the ultrasonic probe 10 of Fi~ure l. Figure 2a illustrates schemAtically the identifiable contents of the trace of Figure 2, and indicates how the length of the anornally 30 is derived or extracted therefrolll. Clearly, once the ultrasonic pulser/receiver 30 i$ calibrated, the distance between various spikes or "blips" on the ultra-sonic pulser/receiver trace is a rneasure of the actual spacin~ between MRI
8~132 ii~f~re[~ oi~ ol anolllali(s in thc wor'cpiece that gave rise to the echo pulses rel)resell~ecl by those ~pikes.
As arl alternativt-~ to ~he ultrasonic pulser/receiver, not shown, the signal processillg and display apparatus could comprise a digital counter with circuitry which converts Lhe time delay between subsequent echo pulses to an output clispLay in digital forl~, indicative of the distance between the two anoTnalies or portions thereof which generated the t~o echo pulses.
Figure 3 represents an ultrasollic probe 50 which includes sorne variations to the probe 10 described above. The probe is shown in the con-figuration where the active plane of the probe is paral]el to the plane of the crack. ~As it wou]d be e.g. during the crack measurement in the gun barrels. The workpiece shown in Figure 3 represents the cross-section through gun barrel, cut being in the plane of the crack and parallel to the gun barrel axis). The probe 50, for example, uses directing means in the form of a pair of similar prisms 52 and 54 carried in a housing 53.
The prisms 52 and 54 are acoustically non-coupled by virtue of an air gap 56 between them. Prism 52 supports a transmitting transducer 58, while the prism 54 supports a receiving transducer 60. As in the previous embodi-ment, the prisms 52 and 54 of Figure 3 cause the transducers 58 and 60 to have orthogonal projections of faces 62 and 64 thereof~intersecting along a line defining a depth of field of the probe 50. One e~tremity 66 of a crac~ 68, i.e., an anomaly, ;s seen to be locatable in the depth of field of the probe 50, in fl curved workpiece 70.
Figure 3 shows that the angles of inclination ~ of each trans-ducer ~8 and 60 dif~er. The dcpth of field of the probe 50, thus, is variable by varyillg certain parameters above, elther singly or in combina-tion. Further yet, it has been found that because of differences in the characteristics of transducer materials functioning in the transmit, and receive modes, optimum results were obtained when the transmitting trans-ducer was of lead ~irconate titanate (PZT) while receiving transducer was of lead meta niobate (PMN).
Al ~l~o~ n(.)t: Ld~ ^!n ~ ~r,~ sd~lc~rs 58 ancl 50 each i~ave brass wear !~]a~ l)olldecl ~n~ Lh~ f;~c~ 62 and t;~:. The transducers are operated, for e~aml)le, a~ frccl~lenc:if s of 2 MHi:, 4 Mll% or 8M~Iz and typically have a face diameter in the range of 0.95 cm to 2.5 cm (0.375" to 0.75"). The wear plate thickness is abou~ one (luar~er of the wave length oi the ultrasonic irradiation, being about 0.027 c:m (.011") when a 4 M11z source is used.
Operation at 4 MHz proved to exhibit best signal-to-noise ratio.
In use, the probe 50 is connected to an ultrasonic generator whicll drives the transducer 58, and to an ultrasonic receiver, for example, ]0 to process and display as a read-out trace the output signal of the receiving transducer 60. That output signal inc]udes elemellts therein representing the echo pulses or reflections of an incident bearn from extremity 66 and the back face of the workpiece 76. The time of arrival of these echo pulses is a function of ~he velocity of sound through the materiaLs of the prisms 52 and 54 and workpiece 70, and the path length travelled by the beams.
Such output traces typically resemble those shown in Figures 2 and 2a.
Again, the spacing and amplitude of echo pulses or spikes is dependent upon the variables just noted, and on the homogeneity of the workpiece, and the intensity of the reflected signal. The latter is itself`dependent upon the reflecting properties of the anomaly. The split prism arrangement of probe 50 has been found to work in configurations where the plane of the crack or anomaly is either parallel,or perpendicular to the plane of the ultrasonic beams.
Figures 4 and 4a show at 80 a preferred embodiment Oe an ultra-sonic probe flccording to this inventiorl. The probe 80 comprises a housing 82 in which ~here is a pair Oe transducers 84 and 86. The transducers 84 and 86 are mounted in intimate contact wiLh directing means in the form of a pair of identically similar pri~sms 88 and 90. I`hese prisms 88 and 90 have faces 92 and 94, each inclineci at an angle ~ (here about 19-20) to the plane of a surface 96 oE a worlcpiece 98. Faces 100 and 102 of prisms 88 and 90 are opposite LO the inclined iaces 92 and 94 thereof. The faces MR/
.
3E~Z
i()() u~(l 10, ale co!]an~ !, th~ workl)i((e surfacc (3¢? ~'llld in intiillate COIl-act witll lh( s.~ e.
The hou~ill, 82 is typically rmade of aluminum, while prisms 88 and 90 Ire rnaclc of ST eel. The trar-lsducer heads 84 and 86 are constructed in a marlner to be describecl below, relative to Figures 5, 6 and 7 and conml(>nly aIe circular, and preferably in the range of 3/8"-1" in diameter.
As best seen in Figure 4a, the prisms o8 and 90 are joined phys;cally together by rnearls of a sandwiched arrangement of plastic attenu-ating plates 104 bonded to steel mounting plates 106 and fln alurninum mount-ing bracket 108. Thus, the prisms 88 and gO are acoustically non-coupled.
An optional steel spacer 110 is provided as required. The details of a particular construction of the attenuating plates are shown in Figure 7, where the top view of prisms, alternating plates and strengthening steel strips are shown. These items 104, 106, 108 and 110 are provided with aligned bore holes which accomodate threaded fastener screws 112 for secur-ing the prism assembly to the housing 82. The bracket 108 has an arm 114 also formed with a bore hole. That bore hole is internally threaded, and in one instance may secure the transducer probe 80 to a positioning bracket or arm, not shown, and used, for exami~le, in instances whère the workpiece 98 is movable relative to the probe 80. A]ternati:ely, the arm 114 may be equipped with a threaded stud 71 which i9 movable longitudinally tllereof, to accomodate use of the probe 80 with a curved sùrface specimen, i.e., to prevent rocking of the probe on the workpiece surface. Note that it is higilly desirable Eor the worlcpiece sur-Eace to be free of paint etc. in these regions where probe reaclings are taken.
In Figures 5 and 6, a transducer head 120 is seen to comprise fl tr.,311sclucer elemellL 122 in the form of a f]at ceramic wafer, enclosed by backing materi;31 124 within an inslllating collar 126. The collar 126 i9 i~self received within a tubular brass enclosure 128, whicil may or may not be threaded exteriorly. The back face of enclosure 128 is closed by a printed circuit board 132 which has circuit elements 134 and contacts 136 .
~R/
8~2 thereon as requircd. Sce l;igures 6 al-)d 6a. Electrical conducting means 138 connect Lhe transduc~r eLement 122 to the circuit board 132. A thin layer of gold is often evaporated onto the transducer's front face to pro-vide good electrical contact: between the probe enclosure 128 and the trans-ducer front face. A wear plate 142 is bonded to the gold layer 140. In the case of Figure 6a where a "wrap-around" transducer elernent 122 is used, that element is bonded to the brass enclosure 128 by an electrically con-ductive adhesive or bonding rnaterial. A layer of gold 140 need not be used in that form of transducer head 120.
Figure 7b shows a typical hook-up using an ultrasonic probe as described therein. The ultrasonic pulser/receiver is any one of the units available commercially, i.e., Krautcrarner Unit USIP II, Sonic UWA
Mark III, etc.
- The foregoing has described both generically and specifically a number of embodiments of this invention. Some alternative conligurations have been suggested. It is therefore envisaged by this invention to include all such changes and modifications as fall within the scope of the claims below.
MR/~l~
.
Claims (10)
IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An ultrasonic probe for use in a system for measuring the length of a reflecting anomaly in a workpiece, said probe being operative to yield an output signal having elements therein which are directly related to the length of said anomaly, said probe comprising;
(a) a first transducer having a face for transmitting an incident beam;
(b) a second transducer acoustically non-coupled to the first transducer, and having a face for receiving a portion of the incident beam reflected from an extremity of the anomaly;
(c) directing means connected to at least one of the transducers so as to cause the transducers to be oriented in a manner such that orthogonal projections of the transducer faces intersect to define a depth of field in which the extremity of said anomaly is locatable; and (d) a housing for supporting the transducers and the directing means, and including signal conducting means connectible to an ultrasonic source to drive the transmitting transducer and to signal processing and displaying apparatus that provides a read-out of said length of the anomaly.
(a) a first transducer having a face for transmitting an incident beam;
(b) a second transducer acoustically non-coupled to the first transducer, and having a face for receiving a portion of the incident beam reflected from an extremity of the anomaly;
(c) directing means connected to at least one of the transducers so as to cause the transducers to be oriented in a manner such that orthogonal projections of the transducer faces intersect to define a depth of field in which the extremity of said anomaly is locatable; and (d) a housing for supporting the transducers and the directing means, and including signal conducting means connectible to an ultrasonic source to drive the transmitting transducer and to signal processing and displaying apparatus that provides a read-out of said length of the anomaly.
2. The ultrasonic probe defined in claim 1, wherein the directing means comprises two similar prisms joined physically together by coupling plates and acoustical attenuating material disposed between said plates and the prisms thereby rendering the prisms acoustically non-coupled, each prism serving to mount a related one of the transducers.
3. The ultrasonic probe defined in claim 1, wherein the first and second transducers are of different materials.
4. The ultrasonic probe defined in claim 1 or 2, wherein the first and second transducers are of the same material.
5. The ultrasonic probe defined in claim 1, 2 or 3, wherein said transducer faces are circular and of the same diameter.
6. The ultrasonic probe defined in claim 1, 2 or 3, wherein the directing means comprises two identically similar prisms joined physically together by coupling plates and acoustical attenuating material disposed between said plates and the prisms thereby rendering the prisms coustically non-coupled, each prism serving to mount a related one of the transducers.
7. The ultrasonic probe defined in claim 1 or 3, wherein the transmitting transducer is of lead zirconate titanate and the receiving transducer is of lead meta niobate.
8. An ultrasonic probe for use in a system for measuring the length of a crack in a workpiece, said probe being operative to yield an out-put signal having elements therein which are directly related to the length of said crack, said probe comprising;
(a) a first transducer having a face for transmitting an incident beam;
(b) a second transducer acoustically non-coupled to the first transducer, and having a face for receiving a portion of the incident beam reflected from an extremity of said crack;
(c) directing means in the form of a pair of similar prisms, one prism being connected to a related one of the transducers, causing the transducer faces to be so oriented that orthogonal projections of each transducer face intersect along a line defining a depth of field in which the crack extremity is locatable; and (d) a housing supporting the directing means and transducers, and including signal conducting means connectible to an ultrasonic source for driving the transmitting transducer and to signal processing and dis-playing apparatus adapted to provide a read-out of the crack length.
(a) a first transducer having a face for transmitting an incident beam;
(b) a second transducer acoustically non-coupled to the first transducer, and having a face for receiving a portion of the incident beam reflected from an extremity of said crack;
(c) directing means in the form of a pair of similar prisms, one prism being connected to a related one of the transducers, causing the transducer faces to be so oriented that orthogonal projections of each transducer face intersect along a line defining a depth of field in which the crack extremity is locatable; and (d) a housing supporting the directing means and transducers, and including signal conducting means connectible to an ultrasonic source for driving the transmitting transducer and to signal processing and dis-playing apparatus adapted to provide a read-out of the crack length.
9. The ultrasonic probe defined in claim 8, wherein the direct-ing prisms are identically similar in shape, size and composition.
10. The ultrasonic probe defined in claim 1, 8 or 9, wherein the directing means comprises a pair of identically similar prisms dis-posed in mirror image symmetry with respect to an axis perpendicular to a plane containing a face of each prism opposite to the faces thereof on which the transducers are mounted, said plane, in use, being parallel to a workpiece surface on which the probe is to be used.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000327084A CA1118882A (en) | 1979-05-07 | 1979-05-07 | Ultrasonic probe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000327084A CA1118882A (en) | 1979-05-07 | 1979-05-07 | Ultrasonic probe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1118882A true CA1118882A (en) | 1982-02-23 |
Family
ID=4114151
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000327084A Expired CA1118882A (en) | 1979-05-07 | 1979-05-07 | Ultrasonic probe |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1118882A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0223038A1 (en) * | 1985-10-17 | 1987-05-27 | Siemens Aktiengesellschaft | Sensing head for ultrasonic examination |
| DE102016015108A1 (en) * | 2016-12-20 | 2018-06-21 | Rheinmetall Air Defence Ag | Wear measuring device for measuring the wear of a weapon barrel |
-
1979
- 1979-05-07 CA CA000327084A patent/CA1118882A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0223038A1 (en) * | 1985-10-17 | 1987-05-27 | Siemens Aktiengesellschaft | Sensing head for ultrasonic examination |
| DE102016015108A1 (en) * | 2016-12-20 | 2018-06-21 | Rheinmetall Air Defence Ag | Wear measuring device for measuring the wear of a weapon barrel |
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