Abstract:
A method for ultrasonic testing includes placing an ultrasonic probe in a liquid bath inside of a pressure vessel having an elastomeric diaphragm stretched across an opening of the pressure vessel, applying pressure within the pressure vessel to bring the elastomeric diaphragm towards a test piece, and conducting ultrasonic testing of the test piece using the ultrasonic probe. A device for ultrasonic testing of a test piece includes a pressure vessel having an elastomeric diaphragm and an ultrasonic probe disposed within the pressure vessel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) to provisional application Ser. No. 60/916,451 filed May 7, 2007, herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to ultrasonic testing. Ultrasonic testing generally involves very short ultrasonic pulse-waves which are launched into materials to detect internal flaws or to determine the material type or characteristics of material. The nature of an ultrasound test requires that the ultrasonic probe come into complete contact with the surface of the test piece. The reason for this is that air between the probe and the test piece will give inconsistent and incorrect results in the test. Because the high frequency sound waves from the probe must travel into the test piece consistently across the entire test area there must not be any voids (air gaps) between the probe and the test piece. The very nature of an ultrasound test is to find unwanted voids in the test piece, without complete coupling between the test piece and the probe the test is of no use. 
     There are two primary methods of ensuring that the coupling between the probe  18  and the test piece are consistent. First, as shown in  FIG. 1 , coupling between the probe  18  and the piece  14  with a gel  16  and significant down-force of 30-40 PSI may be used. Second, as shown in  FIG. 2 , the test piece  14  and probe  18  may be immersed in a liquid bath  20 . While both of these methods are very effective in many applications they are not generally effective in high volume production, or with delicate test pieces or parts that are non-immersible. 
     Other challenges arise when the test piece is large enough to require that the probe be moved to test the entire surface. Because the probe must remain in intimate contact with the surface of the test piece motion of the probe across the surface of the test piece becomes very difficult. The coupling mechanism (gel or elastomeric couplant) can be worn out or will not maintain a consistent coupling with the test piece. The combination of high down force and high friction makes moving the probe while scanning ineffective. The probe can be moved over the test piece in immersion applications (because it is not touching the piece) however that is not of any use in non-immersion applications. 
     Due to problems such as the test pieces in question being fragile, non-immersible and having non-uniform surfaces, ultrasonic testing has significant limitation. What is needed is a way to overcome these and other problems. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, it is a primary object, feature, or advantage of the present invention to improve over the state of the art. 
     It is a further object, feature, or advantage of the present invention to provide for ultrasonic testing which does not require the test piece to come in contact with liquids. 
     A still further object, feature, or advantage of the present invention is to provide for ultrasonic testing which provides consistent coupling with all irregular surfaces. 
     Another object, feature, or advantage of the present invention is to provide for ultrasonic testing that does not require applying high concentrated forces to delicate surfaces. 
     Yet another object, feature, or advantage of the present invention is to provide for ultrasonic testing that allows the probe to be moved over the surface with little effort while maintaining the coupling to the test piece at all times. 
     One or more of these and/or other objects, features, or advantages of the present invention will become apparent from the specification and claims that follow. 
     According to one aspect of the present invention, a method for ultrasonic testing is provided. The method includes placing an ultrasonic probe in a liquid bath inside of a pressure vessel having an elastomeric diaphragm stretched across an opening of the pressure vessel and applying pressure within the pressure vessel to bring the elastomeric diagram towards a test piece. Ultrasonic testing of the test piece is then conducted using the ultrasonic probe. The pressure vessel may be a bell-jar. The test piece may be a catalyst substrate. 
     According to another aspect of the present invention, an apparatus for ultrasonic testing of a test piece is provided. The apparatus includes a pressure vessel having an elastomeric diaphragm and an ultrasonic probe disposed within the pressure vessel. There is a liquid bath within the pressure vessel. There may be a drive shaft operatively connected to the pressure vessel for rotating, translating, or otherwise actuating movement of the ultrasonic probe. There may be a mechanism for holding the ultrasonic probe in a static location. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a prior art method of ultrasonic testing where a gel couplet is used. 
         FIG. 2  illustrates a prior art method of ultrasonic testing where a test piece is placed in an immersion tank. 
         FIG. 3  is a perspective view of an ultrasound bell jar assembly according to one embodiment of the present invention. 
         FIG. 4  is a sectional perspective view of a portion of the ultrasound bell jar assembly. 
         FIG. 5  is a sectional view of a portion of the ultrasound bell jar assembly. 
         FIG. 6  is an exploded view of a bell-jar shown upside-down in service mode. 
         FIG. 7  is an image showing no pressure in the bell-jar on the DPF monolith substrate. 
         FIG. 8  is an image showing pressure in bell-jar on DPF monolith substrate-notice the cell structure appear. 
         FIG. 9  is an image showing pressure in the bell-jar on segmented substrate-notice the segments and cell structure appear. 
         FIG. 10  is an image showing the test bell-jar with water under pressure. 
         FIG. 11  is a perspective view of one embodiment of an ultrasound test unit 
         FIG. 12  is a top view of one embodiment of an ultrasound test unit. 
         FIG. 13  is a front view of one embodiment of an ultrasound test unit. 
         FIG. 14  is a side view of one embodiment of an ultrasound test unit. 
         FIG. 15  is a perspective view of one embodiment of a jar assembly. 
         FIG. 16  is a side view of one embodiment of jar assembly. 
         FIG. 17  is a top view of one embodiment of a jar assembly. 
         FIG. 18  is a sectional view of one embodiment of a jar assembly taken along line A-A of  FIG. 17 . 
         FIG. 19  is a detail view of A of  FIG. 18 . 
         FIG. 20  is a detail view of B of  FIG. 18 . 
         FIG. 21  is a detail view of C of  FIG. 18 . 
         FIG. 22  is a perspective view of one embodiment of a drive assembly. 
         FIG. 23  is a front view of the drive assembly of  FIG. 22 . 
         FIG. 24  is a perspective view of one embodiment of a drive assembly bearing housing. 
         FIG. 25  is an exploded view of one embodiment of a drive assembly bearing housing. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention includes a method for ultrasonic testing that addresses problems with conventional ultrasonic testing. This invention allows for the probe to be immersed while the part remains dry. An ultrasonic probe is suspended in a liquid bath inside of a bell-jar with an elastomeric diaphragm stretched across the bottom of the bell-jar. The liquid on the probe side of the elastomeric diaphragm provides consistent coupling with the test piece on the other side of the elastomer. By applying pressure inside of the bell-jar the elastomer is forced down against the test piece surface conforming to the irregularities in the surface and providing intimate contact at all points. The liquid bath in which the probe resides allows the probe to be moved effortlessly across the surface of the part with no unwanted forces applied to the test piece surface. Under very light pressure the elastomeric diaphragm only applies a very slight pressure to the delicate face of the test piece while maintaining the intimate contact required to ensure a consistent ultrasonic test. 
     The following diagrams depict the invention as used to inspect for internal cracking in automotive and diesel catalyst substrate. These substrates are made of ceramic or silicon carbide and are susceptible to internal cracking during manufacturing. The challenges in ultrasonically testing these pieces are due to the fragile nature of the parts, their inability to be immersed, their size and their typically irregular surfaces. Test results from ultrasonic testing may be used to characterize a test piece, identify flaws or defects in the test piece, reject test pieces, identify the absence of flaws or defects in a test or their other purposes. Of course, the present invention may be used in other contexts for testing of other types of test pieces, especially those which involve test pieces which are fragile in nature, have an inability to be immersed, and have irregular surfaces. 
       FIG. 3  illustrates one embodiment of a bell-jar assembly applied to an test object. The system  30  illustrates an ultrasound bell-jar assembly  32  proximate a test object  34 . Here, the test object  34  is a catalyst substrate. A substrate lift platform  36  is also shown for lifting the substrate  34  to the ultrasound bell-jar assembly  32 . The substrate lift platform  36  allows non-identical test objects to be used in the same setup.  FIG. 3  shows the system with a part in testing. The bell-jar assembly  32  houses the probe and sits above the test piece  34 . The test piece  34  is placed on a stable lift platform  36  which lifts it into the diaphragm of the bell-jar assembly  32 . Once the part is lifted into the diaphragm, pressure is applied inside the bell jar to force the diaphragm into the face of the test piece. 
       FIG. 4  illustrates another view of the ultrasound bell-jar assembly  32  where compressed air, which can be as low as one PSI, is received through an inlet  38 . A probe  40  within the ultrasound bell-jar assembly  32 . The probe  40  is placed proximate or adjacent an elastomeric diaphragm  42 . There is a liquid bath  44  within the ultrasound bell-jar assembly  32 . There is also a probe feed-through opening  46  to allow for electrical connections to the probe  40  to be pass into the ultrasound bell-jar assembly  32  while maintaining pressure.  FIG. 5  illustrates that an ultrasonic frequency signal  48  travels through the liquid bath  44  and the pressurized diaphragm  42  and into the test piece  34 . The probe  40  which is located inside of the bell-jar assembly  32  is suspended in a bath of liquid  44  which provides the consistent coupling with the top side of the pressurized diaphragm  42 . This liquid bath  44  allows the probe  40  to be situated some distance from the diaphragm  42  and gives it the ability to move freely over the surface of the part while maintaining its ultrasonic coupling with the part. All connections to the probe  40  are fed through the center shaft which supports and stabilizes the probe in the bath  44  via a sealed bearing assembly at the top of the bell-jar (probe feed-through  46 ). Once the part is in place and the bell-jar is pressurized the probe can sweep over the part to acquire the sample. Other inputs into the bell-jar include fluid supply ports, pressure relief ports, and additional ports for sensing and detection devices. 
       FIG. 6  provides an exploded view of the ultrasound bell-jar assembly  32 . The assembly  32  includes a secondary backing ring  50  and a main backing ring  52 . A clamp ring  54  in conjunction with nuts  58  and bolts  56  is used to secure the diaphragm  42 . Servicing the bell-jar and internal components is accomplished by rotating the bell-jar upside-down and removing the flange rings and the diaphragm. The backing rings  50 ,  52  are placed to clamp the diaphragm  42  in place and to back the diaphragm  42  in locations where the piece is not in contact with the diaphragm  42  to eliminate bulging of the pressurized diaphragm  42  in unsupported regions. 
       FIG. 7  is a photograph of a bell jar test showing no pressure across the face of the diaphragm.  FIG. 8  is a photograph illustrating pressure in pressure vessel on DPF monolith substrate-notice the cell structure showing through the membrane surface.  FIG. 9  is a photograph of pressure in the pressure vessel on segmented substrate-notice the segments and cell structure showing through the membrane surface. The pressure vessel may contain a liquid or gel solution which will act in conjunction with the pressurized diaphragm as the final couplant between the Ultrasonic probe and the test piece.  FIG. 10  is a photograph illustrating the test pressure vessel with water under pressure. 
       FIG. 11  is a perspective view of one embodiment of an ultrasound test unit. The ultrasound test unit  10  has a housing  12 .  FIG. 12  is a top view of the ultrasound test unit  10 .  FIG. 13  is a front view of the ultrasound test unit  10 .  FIG. 14  is a side view of the ultrasound test unit  10 . 
       FIG. 15  is a perspective view of one embodiment of a jar assembly showing the drive assembly. The assembly  60  includes a drive shaft  62  and a shaft collar  64 . A hard stop level  66  is also shown. A motor mount assembly  70  is shown as well as a bearing housing assembly  68 .  FIG. 16  is a side view of one embodiment of jar assembly.  FIG. 17  is a top view of one embodiment of a jar assembly. 
       FIG. 18  is a sectional view of one embodiment of a jar assembly taken along line A-A of  FIG. 17 .  FIG. 19  is a detail view of A of  FIG. 18 .  FIG. 20  is a detail view of B of  FIG. 18 .  FIG. 21  is a detail view of C of  FIG. 18 .  FIG. 22  is a perspective view of one embodiment of a drive assembly.  FIG. 23  is a front view of the drive assembly of  FIG. 22 .  FIG. 24  is a perspective view of one embodiment of a jar bearing housing. 
       FIG. 25  is an exploded view of one embodiment of a jar bearing housing  80 . A bearing housing  80  is shown as well as an outer bearing spacer  82  and an inner bearing spacer  84 . There is a lower bearing spacer  86 . A thrust bearing  88  is shown as well as thrust washers  90 . A shielded ball bearing  92  is shown as well as round O-ring  94  and a second round O-ring  96 . A U-cup seal  98  is shown as well as a finger disk spring  100 . 
     The present invention contemplates numerous variations, options, and alternatives. For example, the jar assembly need not be a jar but may be another form of a pressure vessel or container. The liquid bath may be of any number of types of liquids. Any number of drive mechanisms may be used. These and other variations, options, and alternatives are within the spirit and scope of the invention.