Abstract:
A method for detecting defects in a railway rail including a search unit and preferably a roller search unit (“RSU”) mounted on a test vehicle and in rolling contact with the running surface of the rails to inspect each rail. The RSU includes a tire filled with a liquid and a transducer assembly mounted within the tire. The transducer assembly includes one or more arrays of ultrasonic transducers directed toward the running surface of the rail. A laser profiler mounted on the test vehicle in combination with a linear encoder provide profile data which is communicated to a system controller to dynamically adjust the focal laws for the one or more arrays of transducers to dynamically steer the transmitted beams to produce the ideal inspection beam sets while the test vehicle is in motion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of co-pending application Ser. No. 61/526,094, filed on Aug. 22, 2011, entitled ULTRASONIC INSPECTION SYSTEM. 
     
    
     FIELD 
       [0002]    The present invention generally relates to a method of detecting defects in a structure and, more particularly, to a method of performing nondestructive-type testing in situ using ultrasonic transducers to detect flaws and defects in a railway rail. 
       BACKGROUND 
       [0003]    The United States Federal Railroad Administration has published statistics which indicate that train accidents caused by track failures including rail, joint bar and anchoring resulted in approximately 1,300 derailments from 2001 to 2011. The primary cause of these track failures was defects and fissures in the rail head. 
         [0004]    During their normal use and as would be expected, the rail portions of most track structures will be subjected to severe, and uncontrollable environmental conditions. These severe environmental conditions, over a relatively long period of time, may ultimately result in such rail developing certain detrimental flaws. 
         [0005]    In addition, in today&#39;s modern railroad industry, the rail portion of such track structures will quite often be required to support rather heavy loads being carried by modern freight cars. Furthermore, these heavy loads are travelling at relatively high speeds. It would not be uncommon for these freight cars, when they are fully loaded with cargo, to weigh up to generally about 125 tons. Such relatively heavy loads and high speeds can, also, result in undesirable damage to such rail portions of the track structure. Such damage, for example, may include stress fractures. 
         [0006]    It would be expected, therefore, that if these detrimental defects were not timely detected and, likewise, if they are left unrepaired such defects could lead to some rather catastrophic disasters, such as, a train derailment. 
         [0007]    As is equally well known, such train derailments are not only costly to the railroad industry from the standpoint of the damage that will likely be incurred to both the cargo being transported and to the railway equipment itself, but, even more importantly, such train derailments may also involve some rather serious injuries, or even worse death, to railway personnel and/or other persons who may be in the vicinity of a train derailment. 
         [0008]    It is further well known that a relatively large number of these train derailments have resulted in the undesirable and often costly evacuation of nearby homes and businesses. Such evacuation may be required, for example, when the cargo being transported involves certain highly hazardous chemical products. These hazardous chemical products will generally include both certain types of liquids, such as corrosive acids, and certain types of toxic gases, such as chlorine. 
         [0009]    To detect such flaws and defects, ultrasonic testing has been employed. Vehicles have been built which travel along the track and continuously perform ultrasonic testing of the track. These vehicles carry test units which apply ultrasonic signals to the rails, receive ultrasonic signals back from the rails, and provide indications of flaws and defects. 
         [0010]    Some of these systems employ small, thin-walled tires which roll along the rails. They are pressed down against the rail so as to have a flat area in contact with the rail. These tires contain acoustic transducers and are filled with a liquid, usually a water-glycol solution. The transducers are arranged at various angles to produce acoustic beams which travel through the mounting substrate and liquid and are directed toward the rail surface. The angles are predetermined based on the known geometry of a new rail. The high frequency electrical transducers are pulsed with energy and the generated beams pass through the material of the liquid and tire into the rail. The angle of incident of the beam with respect to the rail surface is predetermined based on the desired angle of refraction in a known material, assuming a horizontal head shape according to Snell&#39;s law. 
         [0011]    Only a few transducers can be mounted to the substrate due to spatial considerations. Also, the angles of the acoustic beams produced by the transducers are dictated by their fixed mounting angle. The rail head may be worn or deformed by the massive loads and stresses to which it is subjected. The shape of the rail head may change over time whereby the running surface of the rail head is no longer substantially horizontal. Because many of the inspection systems employ ultrasonic transducers mounted in a fixed position at a fixed angle relative to a presumed horizontal inspection surface, the resulting beam inspection angles may not be optimal and may fail to detect defects in the rail. 
       SUMMARY 
       [0012]    The present invention provides an apparatus for detecting defects in a railway rail. The apparatus includes a search unit and preferably a roller search unit (“RSU”) mounted on a test vehicle and in rolling contact with the running surface of the rails to inspect each rail. The RSU includes a tire filled with a liquid and a transducer assembly mounted within the tire. The transducer assembly includes one or more arrays of ultrasonic transducers directed toward the running surface of the rail. The liquid provides a coupling between the transducers through the tire wall and into the rail. Beams transmitted by the one or more arrays of ultrasonic transducers may be dynamically adjusted to compensate for the varying profile of the rail head and running surface. A laser profiler mounted on the test vehicle in combination with a linear encoder provide profile data which is communicated to a system controller to dynamically adjust the focal laws for the one or more arrays of transducers to steer the transmitted beams to produce the ideal inspection beam sets while the test vehicle is in motion. 
         [0013]    The ultrasonic phased array transducers including one or more transducer assemblies with 8 to 256 individual elements that are individually controlled may be used to effectively steer the inspection beam. The elements may be arranged in a strip (linear array), a square matrix (2-D array), a ring (annular array), a circular matrix (circular array), or other more complex shapes. 
         [0014]    An ultrasonic phased array transducer system varies the time between the pulsing of individual elements of the array in such a way that the individual waves from each individual element combine in predictable ways to steer or shape the beam emitted from the array. This is accomplished by pulsing the individual elements at calculated times. Based on the focal law of the array, the properties of the transducer assembly, the transmission medium and the geometry and acoustical properties of the test material, the beam can be dynamically steered through various angles and focal distances. Beam steering is accomplished in a fraction of a second allowing the beam to be steered to the optimal angle based on the orientation of the test material, such as a rail head, to scan from multiple angles, sweep over a range of angles, or scan at multiple focal depths. The ultrasonic phased array transducer can spatially sort a returning wave front according to the arrival time and amplitude at each element to be processed and displayed. 
         [0015]    The output from profiling sensors such as one or more laser transceivers or cameras are combined to determine the geometric profile of the rail, which is used by the system to determine the focal laws for the desired target of the ultrasonic beams generated by the ultrasonic phased array transducers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is an illustration of a test vehicle with an ultrasonic inspection system of the present invention. 
           [0017]      FIG. 2  is a diagrammatic illustration of a rail profiler system. 
           [0018]      FIG. 3  is a partial plan view of a rail head. 
           [0019]      FIG. 4  is a sectional end view of a rail. 
           [0020]      FIG. 5  is an illustration of two-dimensional profile data for a rail. 
           [0021]      FIG. 6  is a perspective view of a right carriage assembly. 
           [0022]      FIG. 7  is a perspective view of the carriage assembly. 
           [0023]      FIG. 8  is a partial sectional view of a first RSU assembly. 
           [0024]      FIG. 9  is a partial sectional view of a second RSU assembly. 
           [0025]      FIG. 10  is a perspective view of a phase array ultrasonic transducer assembly. 
           [0026]      FIG. 11  is a plan view of the phased array ultrasonic transducer assembly of  FIG. 10 . 
           [0027]      FIG. 12  is a perspective view of a phased array ultrasonic transducer from the assembly of  FIG. 10 . 
           [0028]      FIG. 13  is an illustration of beams generated from the ultrasonic phased array assembly of  FIG. 11 . 
           [0029]      FIG. 14  is a plan view of an ultrasonic transducer assembly. 
           [0030]      FIG. 15  is a sectional view of the ultrasonic transducer assembly of  FIG. 14  along line  15 - 15 . 
           [0031]      FIG. 16  is a plan view of an ultrasonic transducer assembly. 
           [0032]      FIG. 17  is an illustration of beams generated by phased array ultrasonic transducers for a worn rail head. 
           [0033]      FIG. 18  is an illustration of beams generated by phased array ultrasonic transducers for a rail head. 
           [0034]      FIG. 19  is an illustration of beams generated by phased array ultrasonic transducers for a worn rail head. 
           [0035]      FIG. 20  is an enlarged partial sectional view of a worn rail head illustrating a defect. 
           [0036]      FIG. 21  is an enlarged partial sectional view of a worn rail head illustrating another defect. 
       
    
    
     DESCRIPTION 
       [0037]    As required, detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for the claims and/or as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0038]    Moreover, except where otherwise expressly indicated, all numerical quantities in this description and in the claims are to be understood as modified by the word “about” in describing the broader scope of this invention. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary, the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures or combinations of any two or more members of the group or class may be equally suitable or preferred. 
         [0039]    Referring initially to  FIGS. 1 and 2 , a rail inspection apparatus unit is generally indicated by reference numeral  20 . The rail inspection apparatus includes a carriage  22  for supporting test assemblies  24  mounted behind a test vehicle  26 , a profiler system  28  mounted under the test vehicle  26 , and an encoder  30 , all of which are coupled to a system controller  32  mounted inside the test vehicle  26 . 
         [0040]    The test vehicle  26  includes front  34  and rear  36  rubber tires and flanged rail wheels  38  and  40 . The flanged rail wheels  38  and  40  engage rails  42 ,  44  when the test vehicle  26  is in a hi-rail configuration. In the hi-rail configuration the front tires  34  are not in contact with the ground or rails  42  and  44 , and the front of the test vehicle  26  is supported on the front flanged rail wheels  38 . The rear tires  36  are in contact with the rails  42  and  44  to drive the test vehicle  26  along the rails  42  and  44 . The encoder  30  is coupled to the front flanged rail wheels  38 . 
         [0041]    The encoder  30  outputs information to the test assemblies  24  and profiler system  28 , which is used to determine position. The encoder  30  is preferably a linear encoder that outputs a digital signal corresponding to the rotation of the flanged rail wheel  38 . The encoder  30  outputs a signal which corresponds to the rotation of the rail wheel  38 , which in turn is used to calculate the position of the test vehicle  26 . 
         [0042]    Referring to  FIGS. 1 and 2 , the profiler system  28  includes two pairs of laser transceivers  46  and  48 , and may also include two pairs of line scan cameras  50  and  52 , each of which is directed at rails  42  and  44 , respectively. The laser pair  46  includes a gauge side laser transceiver  54  and a field side laser transceiver  56  directed at rail  42 . Gauge side laser transceiver  54  scans the gauge side  58  of the rail  42 , including the web and base, across the rail head  60 . The field side laser transceiver  56  scans the field side  62  of the rail  42 , including the web and base, across the rail head  60 . Likewise, laser transceiver pair  48  includes a gauge side laser transceiver  64  and a field side laser transceiver  66  directed at rail  44 . Gauge side laser transceiver  64  scans the gauge side  68  of the rail  44 , including the web and base, across the rail head  70 . The field side laser transceiver  66  scans the field side  72  of the rail  44 , including the web and base, across the rail head  70 . Each laser transceiver may scan at a fixed rate or frequency or may be triggered by the encoder  30  output. A laser profiling system such as a LMI Gocator 2050available from LMI Technologies may be used. 
         [0043]    Line scan camera system  50  includes a gauge side line scan camera  76  and a field side line scan camera  78  directed at rail  42 . The gauge side line scan camera  76  captures a line or column of data of the gauge side  58  of the rail  42 . The field side line scan camera  78  captures a line or column of data of the field side  62  of the rail  42 . Likewise, the line scan camera system  52  include a gauge side line scan camera  80  and a field side line scan camera  82  directed at rail  44 . The gauge side line scan camera  80  captures a line or column of data of the gauge side  68  of the rail  44  while the field side line scan camera  82  captures a line or column of the field side  72  of the rail  44 . Line scan cameras such as a Basler Runner series available from Basler Vision Technologies may be used. 
         [0044]    Each of the line scan cameras  76 ,  78 ,  80  and  82  may be triggered by the encoder  30  output or scan at a set frequency such as 27,000 Hz, depending on the hardware selected and the storage capacity of the system. It should be understood that other frequencies and resolutions may be used for the line scan cameras and laser transceivers. Additionally, other image systems may be used such as a high definition video system, for example. 
         [0045]    The pair of laser transceivers  46  and line scan cameras  50  may be surrounded by a housing  84 . Laser transceivers  48  and line scan cameras  52  may be surrounded by a housing  86 . Each housing  84  and  86  encloses the laser transceivers and line scan cameras on the four vertical sides and top to protect the lasers and cameras from the environment, to improve the performance of the lasers and cameras in all ambient lighting conditions and to protect the eyes of any individuals working or located around the test vehicle  26 . 
         [0046]    Referring to  FIGS. 6-9 , the carriage assembly  22  includes right  100  and left  102  carriages. The right  100  and left carriages  102  are connected together by a cross member  104 , which includes a pneumatic or hydraulic cylinder  106  to adjust the width of the carriage  22  as necessary to engage the rails  42  and  44 . The left carriage  102  is a mirror image of the right carriage  100  so only the right carriage will be described in detail, it being understood that the same detailed description applies to the left carriage  102 . 
         [0047]    The right carriage  100  includes a pair of flanged rail wheels  107 , which support the carriage  100  on the rail  42 . The flanged rail wheels  107  are mounted to a frame  109 , to which a first roller search unit (“RSU”) assembly  108  and a second RSU assembly  110  is mounted. Nylon, Teflon® or other high density polymer blocks  112  are mounted between the flanged rail wheels  107  and the RSUs  108  and  110 . Spray nozzles  114  are mounted in the polymer blocks  112  and directed toward the running surface of the rail head  60  and the adjacent RSU  108  or  110 . The polymer blocks  112  provide protection for the RSUs  108  and  110 . The spray nozzles  114  spray a liquid such as water or a water/ethylene glycol mixture on the running surface of the rail head  60  to remove debris and to improve the contact of the RSUs  108  and  110  with the running surface  69  of the rail  42 . 
         [0048]    RSU assembly  108  includes a tire  120  mounted on a wheel  122 , which rotates with the tire  120  about an axle  124 . The tire is clamped to the wheel  122  at its bead  121  and includes a circumferential contact surface or tread  123 , which makes contact with the running surface  69  of the rail head  60 . The axle  124  is mounted to the frame  109 . The tire  120  contains a coupling liquid  126  such as a water/ethylene glycol mixture. A transducer assembly  128  may be positioned within the tire  120  and coupled to the axle  124 . The transducer assembly  128  includes a lower planar surface  129 , which is mounted facing the circumferential contact surface  123  of the tire  120 , and is maintained in a plane generally parallel to the running surface  69  of the rail head  60  at a fixed distance. 
         [0049]    RSU assembly  110  includes a tire  130  mounted on a wheel  132 , which rotates with the tire  130  about an axle  134 . The axle  134  is mounted to the frame  109 . The tire is clamped to the wheel  132  at its bead  131  and includes a circumferential contact surface or tread  133 , which makes contact with the running surface  69  of the rail head  60 . The tire  130  contains a coupling liquid  136  such as a water/ethylene glycol mixture. A transducer assembly  138  may be positioned within the tire  130  and coupled to the axle  134 . The transducer assembly  138  includes a lower planar surface  139 , which is mounted facing the circumferential contact surface  133  of the tire  130 , and is maintained in a plane generally parallel to the running surface  69  of the rail head  60  at a fixed distance. 
         [0050]    Referring to  FIGS. 9-13 , the transducer assembly  128  includes a transducer mount  140 , which may be formed from a high strength plastic, epoxy, resin, Noryl® resin blend of polyphenylene oxide and polystyrene (“PPO”), polyphenylene ether (“PPE”) resin, or a PPE/olefin resin blend, for example. 
         [0051]    Conventional ultrasonic transducers typically consist of a single transducer that generates and receives ultrasonic sound waves, or a pair of transducers, one generating sound waves and the other receiving the echo returns. Phased array transducers typically include a transducer assembly with 8 to 256 individual elements that are individually controlled. The elements may be arranged in a strip (linear array), a square matrix (2-D array), a ring (annular array), a circular matrix (circular array), or other more complex shapes. The transducers typically operate at frequencies from 1 MHz to 10 MHz, for example. 
         [0052]    The ultrasonic phased array transducer system varies the time between the pulsing of individual elements of the array in such a way that the individual waves from each individual element combine in predictable ways to steer or shape the beam from the array. This is accomplished by selectively energizing or pulsing the individual elements at independent times. These respective delays are referred to as delay laws and/or focal laws. Based on the focal law of the array, the properties of the transducer assembly mount, the transmission medium and the geometry and acoustical properties of the test material, the beam can be dynamically steered through various angles and focal distances. Beam steering is accomplished in a fraction of a second allowing the beam to be steered to the optimal angle based on the orientation of the test material, such as a rail head, to scan from multiple angles, sweep over a range of angles, or scan at multiple focal depths. The ultrasonic phased array transducer can spatially sort a returning wave front according to the arrival time and amplitude at each element to be processed and displayed. 
         [0053]    The transducer assembly  128  includes four ultrasonic phased array transducers  142 ,  144 ,  146  and  148  secured to the mount  140  for generating ultrasonic acoustic beams forward and backward longitudinally generally parallel to a longitudinal axis X of the rail  42  and acoustic beams across the rail  42  at an angle relative to the longitudinal axis X from both the gauge side  58  and the field side  62  to detect under shell defects. The transducer assembly  128  also includes two ultrasonic phased array transducers  150  and  152 , secured to the mount  140 , directed laterally or transversely relative to a lateral axis Y across the rail head  60  from both the gauge side  58  and field side  62 , to detect vertical split head (“VSH”) defects. 
         [0054]    The forward facing ultrasonic phased array transducers  142  and  146  are mounted on the transducer mount  140  on a compound symmetric wedge shape wherein surface  154  is formed or cut at two different angles, for example, a wedge angle  156  and a roof angle  158 . Wedge angle  156  may be between zero and 30 degrees and roof angle  158  may be between 10 and 55 degrees, for example. The backward facing ultrasonic phased array transducers  144  and  148  are symmetrically secured to the transducer mount  140  at the same angles as the corresponding forward facing ultrasonic phased array transducers  142  and  146 . The laterally facing ultrasonic phased array transducers  150  and  152  are secured to the transducer mount  140  at a roof angle of between about 10 and 55 degrees and a wedge angle of between about zero and 30 degrees, for example. For clarity, the ranges stated herein are stated as positive ranges, but it should be understood that a range includes a corresponding negative range or +/−a range. 
         [0055]    In the exemplary embodiment, ultrasonic phased array transducers  142  and  146  are secured to transducer mount  140  such that beams  160  and  162 , when viewed from above, are emitted parallel to rail  42  and when viewed in elevation view are emitted at an angle to produce a resultant beam in the rail  42  of about 60 to 80 degrees from vertical. Likewise, ultrasonic phased array transducers  144  and  148  emit beams  164  and  166  parallel to rail  42  in the opposite direction from beams  160  and  162  when viewed from above, and at an angle to produce a resultant beam in the rail  42  of about 60 to 80 degrees from a vertical axis Z when viewed in elevation. 
         [0056]    Ultrasonic phased array transducers  142  and  146  also emit ultrasonic beams  168  and  170  directed generally parallel to rail  42  when viewed from above, each crossing the rail  42  in opposite directions at an angle to produce a resultant beam in the rail  42  of about 10 to 30 degrees. When viewed in elevation view, beams  168  and  170  descend into rail  42  at an angle to produce a resultant beam in the rail  42  of about 60 to 80 degrees from vertical. Likewise, ultrasonic phased array transducers  144  and  148  also emit beams  172  and  174  directed generally parallel to rail  42  when viewed from above, each crossing the rail  42  in opposite directions at an angle to produce a resultant beam in the rail  42  of about 10 to 30 degrees. When viewed in elevation view, beams  172  and  174  descend into rail  42  at an angle to produce a resultant beam in the rail  42  of about 60 to 80 degrees from vertical. Ultrasonic beams  168 ,  170 ,  172  and  174  provides a view of under shell defects in the rail head  60  from both the gauge side  58  and the field side  62 . 
         [0057]    Ultrasonic phased array transducers  150  and  152  emit ultrasonic beams  176  and  178  which are directed downward at an angle to produce a resultant beam in the rail  42  of approximately 30 to 80 degrees to vertical when viewed in a transverse elevation view. Ultrasonic phased array transducers  150  and  152  may be longitudinally offset to avoid interference between the generated beams  176  and  178 . Beam  176  enters rail head  60  on the gauge side  58  and travels across head  60  to the field side  62 . Beam  178  enters rail head  60  on the field side  62  and travels across head  60  to the gauge side  58 . Beams  176  and  178  detect vertical split head defects. Additionally, ultrasonic phased array transducers  150  and  152  may induce a shear beam, compression beam, or both in the head  60  depending on the rail head shape constraints. 
         [0058]    Referring to FIGS.  8  and  14 - 16 , the transducer assembly  138  includes a transducer mount  200  formed from a Noryl® resin blend or other resin. The transducer assembly  138  may include individual ultrasonic transducers or one or more ultrasonic phased array transducers, directed at the rail  42 . Preferably, transducer assembly  138  includes a bank of forward-directed ultrasonic transducers  202  and rearward-directed ultrasonic transducers  204  mounted at an angle to produce a beam in the rail of approximately 30 to 60 degrees to vertical in opposite directions. As illustrated, banks  202  and  204  each include four ultrasonic transducers  206 ,  208 ,  210 ,  212 ,  214 ,  216 ,  218 ,  220 , although fewer or more ultrasonic transducers may be used. Each of the ultrasonic transducers  206 - 220  may be energized independently to emit a forward-directed beam  222  and a rearward-directed beam  224 . Beams  222  and  224  penetrate through the web  61  of the rail  42  to the foot  63  to detect defects, such as web and bolt hole cracks, weld defects and centrally located transverse defects. The transducers selected to fire are determined by the rail geometry and known mount alignment, which applies to each bank of ultrasonic transducers. 
         [0059]    The transducer assembly  138  may also include conventional transducers  226  and  228 , which may be mounted along a longitudinal centerline of transducer mount  200  to produce a refracted sheer wave of about 55 to 85 degrees. The transducers  226  and  228  may be energized to produce ultrasonic beams  230  and  232  at an angle to produce a resultant beam in the rail  42  of approximately 60 to 80 degrees relative to vertical axis Z in opposite directions generally parallel to longitudinal axis X. Beams  230  and  232  detect transverse defects along the transverse axis Y of the rail head  60 . 
         [0060]    Transducer assembly  138  may include an additional ultrasonic transducer bank  234  mounted at an angle of zero degrees to emit beam  236  substantially vertically through the web  61  to the foot  63 . Beam  236  detects defects such as bolt-hole cracks, centrally located defects as well as rail head  60  horizontal and angled defects. The ultrasonic transducers in bank  234  typically operate in pairs of adjacent ultrasonic transducers with one ultrasonic transducer emitting the beam  236  and the other ultrasonic transducer receiving the beam reflection. This pitch/catch combination reduces false returns from internal reflections within the RSU and reflections from the surface of the rail. 
         [0061]    The pair of ultrasonic transducers in bank  234  is tightly spaced and may be transversely arranged as illustrated in  FIG. 14  or may be longitudinally arranged in a stepped pattern as illustrated in  FIG. 16 . 
         [0062]    To calculate the focal law for each ultrasonic phased array transducer, raw cross section points are determined by the laser transceivers  46  and  48 . For simplicity and clarity, the process for one of the transverse pair  46  will be discussed, which will also apply to the other transceiver pair  48 . 
         [0063]    Referring to  FIGS. 2-5 , data is received by each of the laser transceivers  54  and  56 , which are directed at rail  42 . The data points are sent to the system controller  32  along with the encoder data from encoder  30 . Each set of data points from the laser transceivers represents a slice of the rail  42  at a given encoder count. The system controller  32  takes the raw data points from each laser transducers  54  and  56  for a given encoder count and processes the points to produce a two-dimensional slice of the rail  42  (see  FIG. 4 ). From the two-dimensional slice, the system controller may determine rail features such as the head  60 , web  61 , foot  63 , gauge surface of the head  65 , the field surface of the head  67 , the running surface  69 , the gauge corner  71 , the field corner  73 , the gauge side web surface  75  and the field side web surface  77 , for example, as well as the feature position and gauge of the rail. Additionally, extraneous material layers such as track structures (i.e. spikes, joint bars, etc.) and other layers such as weeds, and debris are identified and filtered out. Surface normals are calculated and smoothed through interpolation, averaging and plane segment reduction. 
         [0064]    Based on the transducer assembly  128  and orientation of each individual ultrasonic transducer array, a range of steering angles is iteratively calculated using ray tracing techniques for each transducer array for each slice  74  of the rail  42 , or at a predetermined interval based on time or travel. 
         [0065]    For example, for a given ultrasonic transducer array, a trial steering angle is selected for an element within the array. The acoustic interface collisions (time and position) are calculated. Using Snell&#39;s law, the refraction or reflection angles are calculated at the interface for a known material, such as steel. The surface normal and acoustic velocities in the material are used to calculate the refraction angle. This calculation is repeated for all interfaces. Next, a target collision is calculated and given a score based on the target proximity and orientation. This process may be repeated for all angles and all elements of the transducer array. The target score determines the selected ray for a given element. Algorithms such as binary ray search may be used to improve processing time or improving the acoustic beam. 
         [0066]    For each element of a given array, a total time travel to a common target point is calculated. The travel time for each element is compared to compute the relative delay in firing or energizing each element and receive digitizing delay to steer the resultant beam to the target point. For each profile slice of the rail, or at a fixed time interval, the focal laws are recalculated and compared to the focal laws for the previous profile slice of the rail. If the new focal laws are different than the current applicable focal law, the new focal law may be applied. The difference may be determined on a profile slice-by-profile slice basis, or for calculations falling outside a tolerance or range for the current applicable focal law. In this manner, the beam generated by the ultrasonic transducer array compensates for variations in the running surface  69  of the rail and the resultant effect on the angle of refraction. 
         [0067]    For the transducer assembly  138 , profile information is used to determine which transducers to fire for any given profile slice. For example, considering transducer bank  202 , the beam  222  generated by any of the transducers  206 - 212 , is oriented to penetrate the web  61  of the rail  42  and travel to the foot  63 . If no return signal is received, then no defect has been detected. However, in order for the beam  222  to penetrate through the web  61  to the foot  63 , the angle of incidence of the beam  222  relative to the surface  69  of the rail head  60  generally should be in a longitudinal plane (Y-Z axes) perpendicular to the plane (X-Z axes) of the running surface  69  and along the centerline  81  of the web  61 . If the running surface  69  is not in a horizontal plane or the web  61  is not oriented along the theoretical centerline of a new rail, the beam  222  may “miss” the web  61  and not penetrate to the foot  63 . 
         [0068]    To compensate for rail wear and variations prevalent in the field with a worn or damaged rail, profile data is used to determine which of the transducers  206 - 212  will be fired for any given profile slice. Typically, transducers  208  or  210  will likely be fired. 
         [0069]    Determination of which of the transducer pairs in the transducer bank  204  and  234  is also based on profile information and calculation of the incident angle which will penetrate the web  61 . 
         [0070]    Referring to the  FIGS. 1-3 , and  17 - 21 , as the test vehicle  26  travels along the rails  42  and  44 , the laser profiling system  28  scans the rails  42  and  44  and the data is output to the system controller  32 . A 2-D profile  74  is generated for each output from the encoder  30  or at a predetermined frequency, and the geometry of each slice  74  is determined The geometry information is used by the system controller  32  to dynamically calculate the optimal incident angle of a particular ultrasonic beam with respect to the rail head surface and steer the beam based on Huygen&#39;s principle and the focal laws. A steering angle for each transducer array may be calculated for each slice  74  or periodically. The calculated steering angle may be dynamically applied for each profile or may be applied when a profile, which is out of range or tolerance for a particular steering angle, persists for two or more calculated profiles. 
         [0071]    A focal law table is maintained by the system controller  32  and stored by encoder count. As the test vehicle travels down the rails which corresponds to the longitudinal or X-axis, the ultrasonic transducer system monitors the encoder count and selects the proper focal laws for each cycle. The ultrasonic transducer system delays firing of individual ultrasonic transducer elements within an array a given amount based on the applied focal law table, and delays receiving and sampling by the given amount for each element. The ultrasonic transducer system sums all element responses at appropriate time intervals and constructs an ASCAN per element group. The ASCAN is sent to the system controller  32  along with the encoder data. 
         [0072]    The ASCAN data from the ultrasonic transducer system is placed in 3-D by applying time along with the ray tracing calculated in the focal law calculations. The amplitude from the ASCAN may be represented in a number of ways such as color, transparency, and/or disc size, for example. The ASCAN data based on the encoder location data is then represented along with the data from the profiler and the image constructed from the line scan cameras to optionally present a 3-D image of the rail with the location of a defect detected within the rail. Additionally, the 3-D image may be viewed by the operator from any angle, rotating the image as desired, and overlaying camera data to provide additional information to the operator. 
         [0073]    When a relevant indication (defect) is detected, the area of the defect may be thoroughly inspected by taking advantage of the phased array&#39;s capability to sweep through a range of angles. This can be done in a single arc for a linear arrangement of phased array elements or in multiple dimensions for a matrix or other arrangement of phased array elements. The system controller  32  calculates focal laws to do a targeted sweep of an area at a higher resolution to verify, size and classify the defect. Further, two or more arrays of transducers may be focused on a defect to scan the defect from various angles to provide additional information to better characterize and display the defect. 
         [0074]    The rail cross sections illustrated in  FIGS. 4 and 5  show a rail profile for an unworn rail  42  with orientation axes X (longitudinal), Y (transverse) and Z (vertical). The rail cross section illustrated in  FIG. 18  shows a rail profile for an unworn rail  400 . The rail cross sections illustrated in FIGS.  17  and  19 - 21  show a rail profile for a worn rail  402 . Referring to  FIG. 18 , for the unworn rail  400 , the incident angles of beams  160  and  162  are dynamically adjusted by transducer arrays  142  and  146  respectively, to produce resultant beams  161  and  163 . 
         [0075]    Referring to  FIG. 17 , for the worn rail  402 , the incident angle of beam  160  is dynamically adjusted by transducer array  142  to produce resultant beam  161 . The incident angle of beam  162  is dynamically adjusted by transducer array  146  to produce resultant beam  163 . 
         [0076]    Referring to  FIG. 19 , for the worn rail  402 , the incident angle of beam  168  is dynamically adjusted by transducer array  142  to produce resultant beam  169 . The incident angle of beam  170  is dynamically adjusted by transducer array  146  to produce resultant beam  171 . Because of the worn rail head  406  on the gauge side  408  of the rail head  406  the angle of incident (the primary steering angle) is adjusted by steering the beam to achieve the desired angle of refraction in the rail head  406 . 
         [0077]    If a defect  410  or  412  for example, is detected, information such as the characteristics of the defect, location, image information at the location of defect, and geometry of the defect may be stored. Additionally, the system controller  32  may direct one or more phased array transducers in the second or additional trailing RSUs to scan or sweep the area of a defect detected by the first RSU  108  to obtain additional information regarding the defect. The defect location in the head, or anywhere a defect is located, may be displayed graphically along with the profile and line scan camera data to provide the operator with a 3-D image that may be manipulated, rotated and viewed from any orientation or angle. The defect may be viewed from any vantage point outside the rail or may be viewed from within the rail. The size of the defect  410  or  412 , for example, may be represented by concentric rings around the defect or by colors to provide additional information to the operator. 
         [0078]    It is to be understood that while certain now preferred forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims.