Abstract:
In accordance with the present invention, an x-ray diffraction apparatus and method are provided in which an x-ray or goniometer head can be adjusted in different directions to allow the head to direct x-rays at a part from various positions. In this manner, measurements can be taken from a wider region of the part without requiring that the part itself be moved or that an operator move the unit, which can be relatively heavy. In one aspect, the head can be rotated about its internal axis so that it can more readily direct x-rays along curved surfaces of parts while keeping a substantially constant distance therefrom. It is preferred that the apparatus be a portable unit including adjustment mounts to allow the x-ray head to be moved in the different directions so that it can be transported for use in the field at the site at which a part is located. In this instance, the unit allows for measurements to be taken from the part while it remains in service. Accordingly, the present portable unit allows for x-ray diffraction techniques to be used on parts where it is not practical or economic to remove them from service, such as cables or wire ropes used as tension members for bridges. Moreover, the preferred portable x-ray diffraction unit herein provides an easy to interpret readout of the results of its measurements by generating a map at the part site so that, for example, any abnormalities in stress measurements taken will be highlighted in comparison to adjacent points on the map where more normal measurements are shown.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This is a division of prior application Ser. No. 09/539,346, filed Mar. 31, 2000, which is hereby incorporated herein by reference in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention relates to an apparatus and method for measuring strength related characteristics of a part using x-ray diffraction techniques and, more particularly, to an apparatus and method for measuring the strength related characteristics at a variety positions on the part.  
         BACKGROUND OF THE INVENTION  
         [0003]    The use of x-ray diffraction techniques for measuring residual stresses in crystalline substances such as metal or ceramic materials is well-known. The general idea with the use of x-ray diffraction is to subject the material to the radiation of x-rays with the resulting sensed x-ray diffraction peak interpreted to arrive at a measurement of a strength related characteristic, i.e. stress, retained austenite, hardness of the part material, to show, for instance, the level of fatigue in the material. While using coupons or removing the part from service for measurement by x-ray diffraction laboratory equipment is done, neither is particularly satisfactory in that coupons require a portion of the part to be removed therefrom, and removing a part to be measured from service can create undue downtime along with the requisite labor for removal and replacement of the part back into service.  
           [0004]    Accordingly, there is a need for portable x-ray diffraction equipment that can be used in the field at the site at which a part is located and without requiring the part to be removed from service. Portable x-ray diffraction equipment is known, however, some of these units suffer from great bulk making them less than ideal for use in field conditions. A further shortcoming with known x-ray diffraction equipment lies in the limitations in moving the goniometer head so that measurements can be taken across a sufficient number of positions on the part to obtain meaningful information therefrom, particularly where the part being tested has been used in the field where corrosion and other environmental use conditions can cause highly localized variations in the strength characteristic being determined. When the only measurements taken are those including such localized aberrations, the determination of what the remaining useful life of the part is before it needs to be retired to avoid fatigue failure thereof can be compromised.  
           [0005]    In the laboratory setting this shortcoming requires periodic operator intervention to shift the part being measured so that the goniometer head is in position to direct x-rays at different positions thereon. As is apparent, such operator intervention is time consuming and labor intensive. In the field with current portable units, an operator generally has to physically shift the x-ray diffraction unit including the goniometer head along the part to the different positions at which measurements are desired. In either instance, there is significant operator intervention that is required which is undesirable. In addition, a portable x-ray diffraction unit is needed that can take measurements from complexly-shaped parts and preferably without having to remove them from service while also providing an easy to interpret readout of the results of the measurements to show variations in the fatigue of the part in the region thereof that is measured.  
           [0006]    In this regard, currently there is no means available to directly and quantitatively measure the total strain and hence be able to calculate the total stress non-destructively, the dead load strain and hence the dead load stress on the following: wire rope and/or single strand and/or multi-strand cables once they are installed on a structure or component. In addition there is no technique which can determine the strains on individual strands which may comprise a cable bundle or wire rope.  
           [0007]    It would be desirable to be able to measure the total strain and hence determine the total stress on these types of load bearing members. Total strain is the residual strain plus the restraint strain plus the applied strain. Accordingly, the total strain relates to a material&#39;s remaining capacity to bear a load which is information that is particularly useful for load bearing structures for a number of safety and economic reasons.  
           [0008]    Similarly, it would be desirable to be able to measure the dead load strain and hence dead load stress, which is the strain as a result of the weight and restraint stain of the structure or component without the strain due to the intended carrying load.  
           [0009]    Another problem is that currently there is no means available to directly, accurately and non-destructively track the changes in wire rope and cable strain due to corrosion, creep, fatigue, overload etc.  
           [0010]    A further problem is that currently there is no means available to directly and quantitatively and non-destructively measure the strain and hence be able to calculate the stress on the following: wire rope and or single strand and or multi-strand cables installed on an existing structure or component.  
           [0011]    Despite the widespread use of cables, there are few tools available to inspect and characterize the stresses on cables. In fact, at this time there are two techniques currently in common use, a direct measurement by “jacking”, literally by deflecting the cable with a calibrated jack and an indirect method using the “time to damping” of an induced vibration. Both of these approaches to stress measurement are at best an approximation of cable force due to underlying assumptions as discussed in F. A. Zahn and B. Bitterli&#39;s paper “Developments in Non-Destructive Stay Cable Inspection Methods” delivered at the IABSE Symposium in San Francisco in August, 1995 (see pp. 861-866). This is because the accuracy of the measurement is less than ideal, the total stress in the cable is ignored and the techniques cannot characterize individual strands which may comprise a cable bundle. Accordingly, there is a need for an apparatus and method that can address these shortcomings.  
         SUMMARY OF THE INVENTION  
         [0012]    In accordance with the present invention, an x-ray diffraction apparatus and method are provided in which an x-ray or goniometer head can be adjusted in different directions to allow the head to direct x-rays at a part from various positions. In this manner, measurements can be taken from a wider region of the part without requiring that the part itself be moved or that an operator move the unit, which can be relatively heavy. In one aspect, the head can be rotated about its internal axis so that it can more readily direct x-rays along curved surfaces of parts while keeping a substantially constant distance therefrom. It is preferred that the apparatus be a portable unit including adjustment mounts to allow the x-ray head to be moved in the different directions so that it can be transported for use in the field at the site at which a part is located. In this instance, the unit allows for measurements to be taken from the part while it remains in service. Accordingly, the present portable unit allows for x-ray diffraction techniques to be used on parts where it is not practical or economic to remove them from service, such as cables or wire ropes used as tension members for bridges. Moreover, the preferred portable x-ray diffraction unit herein provides an easy to interpret readout of the results of its measurements by generating a map at the part site so that, for example, any abnormalities in stress measurements taken will be highlighted in comparison to adjacent points on the map where more normal measurements are shown.  
           [0013]    In one form of the invention, an apparatus is provided having an x-ray head adjustable in at least three mutually transverse axes for directing x-rays from different positions toward a part. The apparatus includes a frame for supporting the x-ray head. An x-axis adjustment mount of the frame is provided and which is operably connected to the head for adjusting the head in an x-axis fore and aft direction. A y-axis adjustment mount of the frame is provided and which is operably connected to the head for adjusting the head in a y-axis lateral direction. A z-axis adjustment mount of the frame is provided and which is operably connected to the head for adjusting the head in a z-axis vertical direction. Accordingly, the present x-ray diffraction apparatus is significantly improved in terms of its ability to coordinate movements of the head in three different axes of movement so that it can scan across a region of a part and direct x-rays thereat from different positions for taking measurements at a larger range of positions on the part than had been available via prior x-ray diffraction equipment. As the adjustment mounts are preferably integrated with the frame that supports the x-ray head, there is little need for operator intervention to move the part to reach the different points thereon from which measurements are desired to be taken.  
           [0014]    In one form, the frame includes a fixture portion that is adapted to removably attach the frame to the part to allow the x-ray head to be used on parts in the field. With the fixture portion attached to the part to be measured, an operator merely has to initialize the x-ray diffraction unit for taking the desired measurements and otherwise need not intervene during the operation of the unit. This is in contrast to prior art x-ray diffraction equipment which requires an operator to hold the unit in position with respect to the part while the measurements are taken.  
           [0015]    In another form, the fixture portion includes adjustable clamps for removably attaching the frame to different sizes of cables with the adjustable clamps comprising the y-axis adjustment mount to allow the head to be located at different positions along the length of the cable. The adjustable clamps for the fixture portion are advantageous as they do not require a different fixture to be constructed for each different part that is to be measured. Instead, the adjustable clamps can be used on cables of a variety of sizes for attaching the frame thereto.  
           [0016]    In one form, the x, y and z adjustment mounts include linear drives for linearly adjusting the head in three mutually perpendicular directions with the x and y adjustment mounts allowing the head to direct x-rays to a predetermined region on the part and the z adjustment mount allowing the focal distance of the head from the part to be adjusted.  
           [0017]    In another form, the frame and x, y and z adjustment mounts are integrated in a portable x-ray diffraction unit for being transported to different part sites. A stand distinct from the portable unit is provided for supporting the unit a desired part site. The integrated portable x-ray diffraction unit herein allows for measurements to be taken from parts in the field and from different points on the part by way of the integrated adjustment mounts.  
           [0018]    It is preferred that the unit and the stand have an adjustable attachment therebetween to allow the unit and stand to be shifted to different positions relative to each other.  
           [0019]    In a preferred form, the head includes detectors for sensing the x-rays off from the part. A controller is provided connected to the head for receiving signals from the detectors and including circuitry adapted to generate maps of a strength related characteristic of the part at the part site with the strength related characteristic being based on the received signals.  
           [0020]    In another form, the head includes an elongate housing having a longitudinal axis, and the frame includes an r-axis adjustment mount operably connected to the head for adjusting the head in an r-axis rotary direction about the housing axis to allow the head to direct x-rays at contoured parts. Preferably, the frame includes a phi-axis adjustment mount operably connected to the head for adjusting the head in a phi-axis rotary direction transverse to the r-axis rotary direction. The phi-axis adjustment mount can be disposed forwardly in the x-axis direction from the z-axis adjustment mount.  
           [0021]    In a preferred form, a touch sensor is provided which is shifted into engagement with the part with the head a predetermined distance from the part in the z-axis direction. A controller is signaled by the touch sensor for repeatable locating of the head at the predetermined distance from the part after use of the sensor. Preferably, the controller includes a teach mode to allow and operator to shift the touch sensor into engagement with the part at various locations thereon by shifting of the head via the adjustment mounts for mapping part contour so that the head precisely directs x-rays toward the part at the various locations along its contour.  
           [0022]    In another form of the invention, an apparatus is provided for directing x-rays at parts with curved surfaces. The apparatus includes an x-ray head having an elongate housing including a longitudinal axis thereof, and a frame for supporting the x-ray head. An adjustment mount of the frame allows the head to undergo rotary movement about the longitudinal axis thereof to substantially keep the head at a predetermined distance from a curved surface of a part at which x-rays are directed at various positions along the part curved surface. Prior x-ray diffraction equipment has been limited to taking measurements from flat, planar surfaces. Where the part includes a curved surface, an operator would have to physically shift or rotate the part to allow the x-ray head to direct x-rays at different positions therealong. In contrast, the present apparatus including the adjustment mount for rotating the head about the housing axis allows the head to take measurements at various positions along the part curved surface while maintaining a substantially constant distance therefrom.  
           [0023]    Preferably, a plurality of other adjustment mounts are provided for moving the head in a plurality of different directions so that the head moves in a path that substantially matches the contour along the part defined by the different positions at which x-rays are to be directed. As described more fully hereinafter, the contour of the part can be mapped into the memory of the controller which can then coordinate the operation of the adjustment mounts to allow the head to move in a path that keeps it at constant distance from the part despite complex shapes of its contour that may be present.  
           [0024]    In another aspect of the invention, a method for obtaining strength related characteristics of a part is provided. The method includes providing a portable x-ray diffraction unit including an x-ray head having integrated adjustment mechanisms for shifting the head in a plurality of different directions, transporting the portable unit to a site at which the part is in service, orienting the x-ray head relative to the part for directing x-rays thereat, shifting the x-ray head via the adjustment mechanisms to direct x-rays at various positions on the part for obtaining a sufficiently large distribution range of measurements of the desired part characteristics for proper strength analysis thereof, detecting the diffraction of the x-rays from the part at the various positions thereon, transmitting signals to a controller for the portable unit that are based on the detected x-rays, interpreting the signals in circuitry of the controller to render measurements of at least one strength related characteristic of the part, and generating a map at the part site of the part characteristics across the entire distribution range of measurements for the part.  
           [0025]    By generating maps at the part site, a person can readily determine the areas of the measured region where the strength related characteristic is in either normal or abnormal ranges therefor. The present method using an x-ray head having integrated adjustment mechanisms and which is incorporated in a portable x-ray diffraction unit makes it possible to generate the maps on site at a part location.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 is a perspective view of a portable x-ray diffraction apparatus including a frame having adjustable mounts for allowing an x-ray head to move in different directions and a fixture portion for attaching the frame of the unit to a bridge tension member to be measured;  
         [0027]    [0027]FIG. 2 is a side-elevational view of a portable unit similar to FIG. 1 including integrated x, y, z, r and phi adjustment mounts for moving the x-ray head in respective x, y, z, r and phi axes corresponding to the different mounts;  
         [0028]    [0028]FIG. 3 is a view similar to FIG. 2 showing a goniometer and detector mount of the x-ray head rotated  90  degrees from the FIG. 2 position;  
         [0029]    [0029]FIG. 4 is a plan view of the portable unit of FIGS. 2 and 3 showing the x-ray head rotated about the phi axis;  
         [0030]    [0030]FIG. 5 is a front elevational view of the portable unit of FIGS.  2 - 4  showing an arcuate oscillation drive for the x-ray head;  
         [0031]    [0031]FIG. 6 is a side elevational view of another portable x-ray diffraction unit including adjustment mounts on a frame thereof for moving the x-ray head in different directions and showing a stand portion of the frame for supporting the unit at the part site;  
         [0032]    [0032]FIG. 7 is a front elevational view of the portable unit of FIG. 6 showing coarse y and z axes adjustment mounts of the stand for moving the head in corresponding y and z axes of movement;  
         [0033]    [0033]FIG. 8 is a side elevational view of another portable unit including a stand for supporting the unit a part site with adjustment mounts for moving the head in different directions;  
         [0034]    [0034]FIG. 9 is a rear elevational view of the unit and stand portion of FIG. 8 showing y and z axes adjustment mounts for moving the head in corresponding y and z axes of movement;  
         [0035]    [0035]FIG. 10 is a flow chart of a method of providing for automatic refocusing of the head at a predetermined focus distance from the part to be measured;  
         [0036]    [0036]FIGS. 11A and 11B are a flow chart of a method in accordance with the present invention of teaching a controller for the x-ray diffraction unit the path in which the head is to travel to obtained the desired measurements from different positions on a part to be measured;  
         [0037]    [0037]FIG. 12 is a elevational view of the part sensor for use in the autofocus and teach map methods of the present invention; and  
         [0038]    FIGS.  13 A- 13 C are views of maps of residual stress of a part that can be generated in the field with the apparatus and method of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]    In FIG. 1, an x-ray diffraction apparatus  10  in accordance with the present invention is shown. The apparatus  10  includes an x-ray head  12  from which x-rays are directed at a part  14 , such as the illustrated bridge tension member  16 . The main advantage provided by the present apparatus  10  is in the ability of the x-ray head  12  to be moved in a plurality of different directions relative to the part via various adjustment mounts, generally designated  18 , that are provided on frame structure  20  supporting the x-ray head  12  for its movements. In this regard, the adjustment mounts  18  afford the head  12  a range of movement so that the head  12  can direct x-rays at the part from different positions thereof and at corresponding different positions on the part  14 . As discussed, this is particularly helpful where the part  14  is in service and subject to various use and environmental conditions that can cause highly specific and localized variations in the strength-related characteristic being measured by the x-ray diffraction apparatus  10 . By having the ability to scan a region of the part, aberrations in the characteristic being measured by the apparatus  10  can be readily determined so, for instance, such localized variations will not unduly influence the determination as to the remaining useful life of the part  14 . By way of example and not limitation, the adjustment mounts  18  herein can provide the x-ray head  12  with movements in the range of 2 to 4 inches.  
         [0040]    In the preferred and illustrated form of FIG. 1, the apparatus  10  is a portable unit that can be transported to a site at which the part  14  is in service. As shown, the portable apparatus  10  includes a fixture portion  22  at the front thereof which enables the frame  20  to be removably attached to the bridge cable or wire rope  16 . In this manner, the portable x-ray apparatus  10  can be taken to the bridge and mounted to the cable  16  so that measurements can be taken therefrom without requiring it be removed from service or that the operator hold the apparatus  10  while the measurements are taken. In addition, the apparatus  10  allows measurements to be taken in conditions where due to loading or environmental reasons, the bridge tension member  16  is moving or vibrating. The fixture portion  22  is designed such that it does not introduce or attenuate the axial strain experienced by the wire rope or cable.  
         [0041]    The fixture portion  22  allows easy positioning of the apparatus  10  relative to the bridge tension member  16  and is suitable for a wide range of wire rope and cable bundle sizes. To this end, the fixture portion  22  includes a pair of adjustable clamps  24 . The adjustable clamps  24  of the fixture portion  22  allow the apparatus  10  to be used on tension members  16  having a wide variety of sizes without requiring a different fixture each time the tension member that is to be measured changes in diameter or configuration over a previously measured member  16 . The adjustable clamps  24  each include a right angle bracket member  26  having an upper plate portion  28  and a vertical rear plate portion  30 . Arms  32  and  34  of the frame  20  are attached at the forward ends as by welding or the like to the rear plate  30  of the clamps  24 . Tightening members in the form of chains  36  are provided to adjustably tighten the clamps  24  onto the bridge tension member  16 . The chains  36  run over an upstanding guide  38  near the juncture of the bracket plates  28  and  30  and around the tension member  16 , as can best seen in FIG. 2. To tighten the clamps  24  onto the tension member  16 , free ends  38  of the chains  36  are pulled to draw the chains  36  tight about the tension member  16  and bracket  26 . A plastic protective sheet  39  can be wrapped on the tension member  16  to minimize damage thereto with the clamps  24  tightened thereon. Releasing the adjustable clamps  24  allows the portable apparatus  10  to be clamped onto various locations along the length of the tension member  16  and about its circumference, and can serve as one of the adjustment mounts  18  for coarse movement of the goniometer head  12  in a lateral, y-axis direction, as will be more fully described hereinafter.  
         [0042]    The x-ray diffraction apparatus  10  will next be more particularly described. The x-ray head  12  herein utilizes divergent x-ray optics that are preferably combined with a close proximity focus distance of approximately 30 to 40 millimeters, a predetermined sized aperture of the head  12  which results in an appropriately shaped divergent x-ray beam such as to illuminate the bridge tension member  16  as shown at  40  in FIG. 1, and a movable mask  42  which can limit the strain data measured, for example, to one wire rope or cable strand at a time. The mask  42  is specifically designed for the wire rope or cable  16  to be measured so that the curvature thereof has little or no effect on the measurements being taken via the x-ray head  12  herein.  
         [0043]    The divergent x-ray optics provide better illumination of the material grains resulting in better definition of the diffraction peaks through increased counting statistics. The close proximity also reduces the attenuation of the x-ray signal both traveling to and from the object  14  being measured. In the case of textured materials and/or materials which exhibit preferred orientation of the material grains, better illumination is helpful and typically wire rope and cable strands  16  would be subjected to textured conditions by virtue of their fabrication process. Accordingly, the preferred short focal distance herein is particularly useful where the part  14  being measured is the illustrated bridge tension member  16 .  
         [0044]    In typical x-ray diffraction systems, the x-ray head  12  generates x-rays in an elongated housing  44  extending in a fore and aft x-axis direction along an internal, longitudinal axis  46  thereof. A target anode (not shown) in the housing  44  directs x-rays out from the housing  44  through a collimator  48  at the lower, forward end thereof. The x-rays from the collimator  48  are directed at a specific point on the part  14  to be measured. Fiber optic detectors  50  are mounted on either side of the collimator  48  on an arcuate detector mount  52 . Depending on the x-ray diffraction technique utilized, the x-ray head  12  can remain stationary while directing x-rays at the point on the part  14  from which measurements are desired, or the head can be oscillated in an arcuate path through a variety of tilt angles via a beta oscillation drive  54  (FIG. 5) so that the point on the part  14  is subject to multiple exposures by way of the multiple tilt angles at which the x-rays are directed at the part  14  from the head  12 , and specifically the collimator  48  thereof. As is known, the beta oscillation drive  54  can be of a rack and pinion variety, including an arcuate rack  56  that is driven in a similarly shaped slot of an arcuate slide bearing block  58 .  
         [0045]    The beta oscillation drive  54  typically is not designed for the x-ray head  12  to take measurements from different points on the part  14  absent movement of the part  14  itself or without manually holding and moving the head along the part  14  to the different positions. In this regard, the apparatus  10  of the present invention utilizes a plurality of adjustment mounts  18  that provide for either manual or automated movement of the x-ray head in a plurality of different directions without requiring that the part  14  be moved or that the operator hold the x-ray diffraction apparatus at the different positions. The adjustment mounts  18  can include those that allow for both rough adjustments of the x-ray head  12  where high speed of movement and/or a large range of motion are desired, and for small, precision movements of the x-ray head  12  so that x-rays can be directed at different positions on the part  14  that are in close proximity to each other.  
         [0046]    The frame  20  including the fixture portion  22  thereof in the apparatus  10  of FIG. 1 includes the following adjustment mounts  18 : x-axis adjustment mount  60  for highly controlled movements of the x-ray head  12  in the fore and aft x-axis direction as indicated by arrow  62 ; rough x-axis adjustment mount  64  which allows for coarse movements of the x-ray head  12  in the x-axis direction  62 ; rough z-axis adjustment mount  66  which allows for coarse up and down movement of the x-ray head  12  in a pivotal z-axis direction indicated by arrow  68 .  
         [0047]    In a lateral y-axis direction such as along the bridge tension member axis  70 , the previously described fixture adjustable clamps  24  can be utilized for coarse movements by releasing the clamps  24  and shifting the apparatus  10  along the axis  70 . Alternatively, the rough x-axis adjustment mount  64  can be used as will be described hereinafter for coarser, larger movements of the x-ray head  12  in the axial direction of the member  16 .  
         [0048]    As can be seen in FIG. 1, the x-ray head  12  can be connected to the forward end of the bearing block  58  which, in turn, is connected to a bracket portion  72  of the frame structure  20 . A clevis member  74  is connected to the rear of the bracket portion  72 . A threaded adjustment rod  76  extends in the x-axis direction  62  into an x-axis slide  78  with the threaded rod  76  being rotatably mounted therein. The slide member  78  can have a dovetail shape for fitting in dovetail slot  80  of slide bearing block  82 . An internally threaded nut (not shown) fixed relative to the rod  76 , and the slide member  78  and block  82  can be provided so that rotating the enlarged knob end  84  of the adjustment rod  76  causes the member  78  to linearly slide in the x-axis direction  62  in the slot  80 . The slide member  78  is operably connected to the x-ray head  12  at the forward end of the frame  20  by a pair of ears  86  upstanding therefrom and adjustably connected to the clevis member  74 , as described more fully hereinafter.  
         [0049]    For coarse movements along the x-axis direction  62 , the rough x-axis adjustment mount  64  employs pivoting of the arms  34  about pivot members  88  attached to the rear of the arms  34 . The bottom of the bearing block  82  is in sliding engagement with the tops of the arms  34  so that as the arms  34  are pivoted about their respective pivot members  88  in a direction away from each other, the bearing block  82  will be caused to slide forwardly along the tops of the arms  34 , thus moving the head  12  in the x-axis direction  62 . Bringing the arms  34  back toward their parallel disposition causes the bearing block  82  to slide rearwardly in the x-axis direction  62 . To use the mount  64  to move the head  12  in the y-axis direction, both arms  34  are pivoted in the same direction while recognizing that this will also give the head  12  a component of movement in the x-axis direction due to the pivoting action of the arms  34  which will be imparted to the head  12 . In addition, axial strains experienced by the bridge tension member  16  can be taken up by slight pivoting of the arms  34  which, although creating movement of the head  12 , should be of a sufficiently minimal character so as not to cause errors during measurement.  
         [0050]    As previously described, the ears  86  extend upwardly from the slide member  78 . In this regard, a support member  90  is provided between the slide member  78  and the ears  86  with the ears  86  projecting upwardly therefrom. The ears  86  are spaced laterally from each other so that they fit between rearwardly extending arms  92  of the clevis member  74 . The arms  92  and ears  86  are secured by way of quick disconnect pins  94  extending through aligned apertures  96  and  98  thereof.  
         [0051]    The rough z-axis adjustment mount  66  is formed by arcuate slots  100  provided in each of the clevis arms  92  and through which adjustment screws  102  extend and into the ears  86 . Accordingly, to make coarse adjustments in the z-axis direction  68 , the quick disconnect pins  94  are pulled and the adjustment screws  102  are loosened. This allows the position of the x-ray head  12  to be adjusted in the z-axis direction  68  by pivoting thereof in a substantially vertical direction until at the desired vertical distance from the part  14  from which measurements are to be taken. Once in the proper position, the adjustment screws  102  can be tightened in their adjusted positions in the slots  100  with the pins  94  reinserted in the apertures  96  and  98 . As is apparent, because of the pivoting action, there is a fore and aft x-axis component of movement associated with the coarse vertical movement in the z-axis direction  68 .  
         [0052]    The apparatus  10  of FIG. 1 also includes a rough phi-axis adjustment mount  104  to allow the x-ray head  12  to be pivoted about a vertical axis. As shown in FIG. 1, the phi-axis adjustment mount  104  is formed by a pivot member  106  which allows the support member  90  to be pivoted relative to the slide member  78  in a rotary phi-axis direction as indicated by arrow  108 . In this manner, the x-ray head  12  can be provided with compound x-y axes movement via the phi-axis adjustment mount  104 .  
         [0053]    FIGS.  2 - 5  are directed to an apparatus  10   a  similar to apparatus  10  in that the x-ray head  12  thereof is capable of movements in a plurality of different directions. It also is preferably adapted to be portable and mounted to a bridge tension member  16  via fixture portion  22  thereof. As best seen in FIG. 4, the rough x-axis adjustment mount  64  is substantially the same as previously described. Similarly, the rough z-axis adjustment mount  66  is also similar to that previously described for apparatus  10 . The x-axis adjustment mount  60  of apparatus  10  is substantially the same in apparatus  10   a ; however, an additional fine x-axis adjustment mount  110  is incorporated in frame  112  of the apparatus  10   a  so that both coarse and precision measurements of the head  12  can be made in the x-axis direction  62 . Also, a fine phi-axis adjustment mount  114  is incorporated in the frame  112 .  
         [0054]    As can be seen in FIGS. 2 and 3, the frame  112  includes a vertical wall portion  116  and a horizontal wall portion  118  connected at the top of the wall portion  118  and projecting forwardly therefrom. The horizontal wall portion  118  generally extends above and overhangs the x-ray head  12  with the x-ray head  12  cantilevered out from the bottom of the vertical wall portion  116  by a rearwardly extending support arm  120  connected to the rear of the x-ray head housing  44  at its forward end and to mounting portion  122  at the rear thereof with the mounting portion  122  being offset from the housing axis  46 .  
         [0055]    The apparatus  10   a  further includes a fine z-axis adjustment mount  124  incorporated in the frame  10   a  for moving the x-ray head  12  in a vertical z-axis direction as indicated by arrow  125 . This is in addition to the previously described rough z-axis adjustment mount  66  which allows for coarser pivoting movement of the x-ray head  12  in an up and down fashion along an arcuate path as indicated by arrow  68 . Z-axis drive block  126  is attached to the frame  112  near the bottom of the vertical wall portion  116  and a gusset  128  is attached between the wall portions  116  and  118  at the juncture thereof. A z-axis linear drive in the form of screw drive  130  is mounted in the z-axis drive block  126  with its upper end in the gusset portion  128 . Where the z-axis drive  130  is automated, motor  132  therefor can be located in the gusset portion  128  and include an encoder  133  for providing precise position feedback information to a controller  135  (FIG. 13) which can be disposed in a control box (not shown) remote from the apparatus  10   a  to provide a closed-loop feedback system for automated movements of the x-ray head  12  herein. Accordingly, operation of the screw drive  130  causes the x-ray head  12 , which is operably connected to the z-axis drive block  126 , to shift in a vertical up and down direction  125  for providing small, precision movements of the head  12 . In this manner, the precision movements provided to the head  12  by the z-axis drive  130  allows for precision tuning of the focal distance of the head  12  from the piece part  14  to be measured.  
         [0056]    The frame  112  also incorporates a fine y-axis adjustment mount  134 . More particularly, the drive block  126  includes a dovetail slot  136 , and a y-axis slide member  138  has a rear dovetail portion  140  which mates in the dovetail slot  136 . The fine y-axis adjustment mount  134  is operably connected to the x-ray head  12  by way of cantilevered portion  142  extending forwardly from the y-axis slide member  138  and attached to the bottom of the mounting portion  122  of support arm  120 . A y-axis linear drive in the form of screw drive  144  is provided, as can be seen in FIG. 4. Where the y-axis drive  144  is automated, y-axis motor  145  is provided including an encoder  147  similar to the z-axis motor  132 . Accordingly, operation of the screw drive  144 , either manually or automatically if it is motorized, causes the head  12  to move in a lateral, y-axis direction  146 . For the phi-axis adjustment mount  114 , the horizontal wall  118  includes a lower wall portion  148  that is pivotal relative to upper wall or handle portion  150 . In this regard, operation of the y-axis screw drive  144  causes the head  44  to shift laterally relative to the wall portion  148  thereabove, as can be seen in FIG. 4.  
         [0057]    The fine phi-axis adjustment mount  114  is provided at the forward end of the wall portion  118  and includes a pivot drive member  152  pivotally interconnecting the lower and upper wall portions  148  and  150 . Where automated, the phi-axis adjustment mount  114  includes motor  154  and associated encoder  156 . Accordingly, operation of the phi-axis pivot drive member  152  causes pivoting of the wall portion  148  relative to the wall portion  150  about rotary phi-axis indicated by arrow  158 . This is in addition to the rotary movement provided by phi-axis adjustment mount  104  in rotary direction  108  about a pivot axis that is rearwardly of the pivot axis of the rotary direction  158 .  
         [0058]    The fine x-axis adjustment mount  110  includes slide member  158  and slide bearing  160  which can have a dovetail mating fit with one another, as can be seen in FIG. 5. The slide member  158  can be provided on the gusset  128  with the bearing  160  formed in the lower wall portion  148 . A linear x-axis drive in the form of screw drive  162  is provided in the slide  158 , and where automated, includes a motor  132  and associated encoder  133 . Operation of the x-axis screw drive  162  causes fine precision movements of the x-ray head  12  in the fore and aft, x-axis direction indicated by arrow  164  this movement is in addition to the coarse x-axis movement afforded by rough x-axis adjustment mount  64 .  
         [0059]    An r-axis adjustment mount  166  is also provided at the rear of the vertical wall portion  116  for rotating the x-ray head  12  about its axis  46 . The r-axis adjustment mount  166  is operably connected to the head  12  via the structure between the frame wall portion  116  and the head housing  44  so that rotation of the housing  44  also entails rotation of the fine x-axis adjustment mount  110 , fine phi-axis adjustment mount  114 , fine z-axis adjustment mount  124 , and fine y-axis adjustment mount  134 . The r-axis adjustment mount  166  includes a rotary drive in the form of rotary member  168 , and where automated, a motor  170  and associated encoder  172  for rotating the member  168  in a rotary r-axis direction as indicated by arrow  174 .  
         [0060]    The r-axis adjustment mount  166  is of particular value where curved surfaces exist on the part  14  such as pipes and the like so that rotation of the head  12  in the r-axis direction  174  keeps the head  12  at a substantially constant distance from the curved surface. In this manner, the r-axis mount adjustment  166  saves the time associated with the process of lifting the head  12  away from the part, rotating the curved surface and then bringing the head  12  back into the proper focused position relative to the part curved surface, and the potential for errors this process entails. Instead, the r-axis adjustment mount  166  allows the head  12  to be rotated about its axis  46  to track the curvature of the curved surface on the part  14  maintaining a substantially constant focused distance therefrom without requiring constant recalibration each time a different point on the part is to be measured.  
         [0061]    In both apparatus  10  and apparatus  10   a , the adjustment mounts  18  provide the head  12  the ability to be moved to different positions relative to the part  14  without moving the part itself. Both rough and fine adjustments mounts  18  are provided so that an operator can move to different regions on a part  14  in a rapid manner where accuracy is not as critical but speed of movement is more important, and then can use the fine adjustment mounts to precisely control head movement as it scans across a particular region on the part  14  between measurement points thereon. This combination provides for highly efficient and accurate measurements across a representative sampling of points on a part  14  so that determinations can be more accurately made with respect to the measured strength characteristic(s) of the part  14  and its remaining useful life. In addition to the advantage with respect to curved surfaces previously discussed, the movements of the head  12  in the x-, y- and z-axes allow for parts having multilevel surfaces to be measured without requiring operator intervention to move the parts  14 , and the attendant time delays associated therewith, as described above. Accordingly, the present invention provides improved flexibility in terms of the types of parts  14  that can be efficiently measured and accurately characterized with the x-ray diffraction equipment described herein.  
         [0062]    Referring next to FIGS. 6 and 7, x-ray diffraction apparatus  10   b  is shown which is similar to those previously described although it lack the fixture portion  22  and instead is adapted more generally for measuring different types of parts, such as pipes. To this end, the apparatus  10   b  includes a forward measuring portion  176  including the x-ray head  12  and a rearward stand portion  178  that are distinct from each other and are interconnected via an adjustable connection  180  similar to the previously described rough z-axis adjustment mount  66  in both apparatus  10  and  10   a . In this manner, the relative position between the measuring portion  176  and the stand portion  178  can be adjusted in a pivotal direction as indicated by arrow  182 . The measuring portion  176  of the apparatus  10   b  incorporates substantially the same fine x-axis adjustment mount  110 , fine phi-axis adjustment mount  114 , fine z-axis adjustment mount  124 , fine y-axis adjustment mount  134 , and r-axis adjustment mount  166  as in the previously described apparatus  10   a . Accordingly, the head  12  is capable of taking measurements from a large number of different positions in a region on the part  14  without necessitating movement of the part itself. Further, because of the distinct nature of the portions  176  and  178  of the apparatus  10   b , the unit is highly portable and accordingly, both are provided with handles with the handle for the measuring portion  176  formed on upper wall portion  150  as in apparatus  10   a , and the stand portion  178  including a handle  184 , as best seen in FIG. 6.  
         [0063]    Coarse movements of the x-ray head  12  can be provided by adjustment mounts  18  incorporated into the stand portion  178 . A rough x-axis adjustment mount  186  includes an x-axis linear drive in the form of screw drive  188  which can be either manually operated or automated via motor  190  and associated encoder  192  thereof. Operation of the x-axis screw drive  188  will cause the head  12  to shift in the x-axis direction  164 . Rough y-axis adjustment mount  194  is similarly constructed including a y-axis linear drive in the form of screw drive  196  which can be either manually operated or automated via motor  198  and associated encoder  200 . Accordingly, operation of the screw drive  196  causes movement of the x-ray head  12  in the y-axis direction  146 . Finally, rough z-axis adjustment mount  202  is provided on the stand portion  178  and includes a z-axis linear drive in the form of screw drive  204  that can be either manually operated or automated via motor  206  and associated encoder  208 . Accordingly, operation of the linear drive  204  causes the x-ray head  12  to undergo coarse and rapid movement in the psi-axis direction  125 .  
         [0064]    As is apparent, each of the rough x-, y- and z-axes adjustment mounts  186 ,  194  and  202 , respectively, shift the entire measuring portion  176  including all of the adjustment mounts thereof in the corresponding direction of movement. In this manner, the relative positions of the fine adjustments mounts will not change as the rough adjustment mounts  186 ,  194  and  202  are operated. Further, it will be noted that the construction of the rough and fine adjustments  18  are very similar in apparatus  10   b . Accordingly, it is contemplated that their main distinction in terms of providing the head  12  with either coarse or fine, precision movements may be with respect to the speed at which they are operated.  
         [0065]    It should be recognized that instead of the stand portion  178 , a robot arm or the like could be utilized, particularly where the apparatus  10   b  is not required for field use. The robot arm could be controlled to give coarse movements to the measuring portion  176  to facilitate rapid movement of the head  12  to the general area from which x-rays are to be directed at the part to be measured.  
         [0066]    [0066]FIGS. 6 and 7 also show a housing  209  connected to the stand portion  178  by bracket arm  211  with the housing  209  including the electronics for interpreting the signals received by the detectors  50 . Mounting the housing  209  to the stand  178  as shown is desirable so that its heavy weight is not borne by the adjustment mounts and wo that it does not have to be moved by the associated drives thereof.  
         [0067]    To mount the apparatus  10   b  to the part  14  being measured, a pair of magnetic feet  210  can be provided at the lower end thereof. The magnetic feet  210  can include permanent magnets for clamping the stand portion  178  tightly to the magnetic material of the part  14  which inactivated. In addition, the feet  210  can include a safety strap attachment  212  to provide additional support by a safety strap wrapped about the part  14  and pulled tight thereabout via crank arm  214  of the attachment  212 .  
         [0068]    [0068]FIGS. 8 and 9 are directed to another x-ray diffraction apparatus  10   c  in accordance with the invention which also includes a forward measurement portion  214  including x-ray head  12  and a rearward stand portion  216  with an adjustable interconnection  218  therebetween similar to apparatus  10   b . The adjustable interconnection  218  is slightly different in that both portions  214  and  216  include devises  220  and  222 , respectively, in which respective arcuate slots  224  and  226  are formed. An interconnection link  228  extends between the devises  220  and  222  and can be fixed at various positions in the slots  224  and  226  at either end thereof. In this manner, the portions  214  and  216  can be pivoted in an arcuate up and down direction as indicated by arrow  228  with a so-called knuckling action provided by the wide range of relative positions they can assume based on the different positions the link  228  can be fixed in each of the slots  224  and  226 .  
         [0069]    The forward measuring portion  214  is significantly modified over that of x-ray diffraction apparatus  10   b  as the wall portions  116  and  118  of the frame  112  are absent due to the elimination of the adjustment mounts in the measuring portion  214 . In this manner, the x-ray head  12  can more readily fit into confined spaces such as in the inside diameter of a pipe or in other openings of parts  14  including surfaces to be measured. Adjustments of the head  12  can be provided via the rearward stand portion  216  and the adjustment mounts thereof which are substantially the same as that described for apparatus  10   b . In this regard, the stand portion  216  includes an x-axis adjustment mount  186 , a y-axis adjustment mount  194  and a z-axis adjustment mount  202 . In this instance, because of the lack of the fine adjustment mounts in the measuring portion  214 , the speed of the associated motors of the respective adjustment mounts incorporated in the stand portion  216  can be reduced so as to improve the accuracy in moving the head  12  between positions to be measured as previously has been discussed. Accordingly, the mounts  186 ,  194  and  202  serve as both the rough and the fine adjustment mounts for the head  12  in apparatus  10   c.    
         [0070]    [0070]FIGS. 10, 11 a  and  11   b  show flow charts that depict methods for creating a map of the shape or configuration of the region or portion of the part  14  desired to be measured so that the head  12  can move under command of the controller  135  via the adjustment mounts  18  to the precise positions needed to have properly focused x-rays directed at the positions on the part to be measured. FIG. 10 shows how focusing can be accomplished using a part sensor in the form of touch sensor  230 , shown in FIG. 12. The touch sensor  230  includes a probe  232  that when lowered into engagement with the part is depressed for actuating a microswitch  234  housed in the probe body  236 . Circuitry in the sensor  230  detects the actuation of the switch  234  and signals the controller  135  by way of interconnect cable  238 .  
         [0071]    To use the touch sensor  230 , it is removed from a stored position remote from the x-ray head  12  and placed onto the head  12  so that the probe  232  extends in a downward direction parallel to the collimator  48 . An operator using a remote control box can coordinate movement of the head via the adjustment mounts and once in position lower the head  12  down until the probe  232  engages the surface of the part  14  to be measured. At this point, the head will be in its focus position at a predetermined distance defined by the length of the probe  232  from the part surface. Accordingly, for different focus distances, different length probes  232  can be utilized. Once the probe  232  engages the part surface, the controller  135  will receive the signal from switch  234  and store the position of the head  12  in memory, and in particular the positions of each of the adjustment mounts. Thereafter, the head  12  moves back to a home or initial position away from the part  12 , and the touch sensor  230  is placed back in its stored position. At this point, all an operator has to do to focus the head  12  relative to the part surface is to click on a refocus icon in a Windows based program for instance or a “teach” key on the remote control box held by the operator and the head  12  under command of the controller  135  will automatically move back down to the previously determined focus position.  
         [0072]    Referring next to FIGS. 11 a  and  11   b , the software of the controller  135  can be programmed to allow the controller  135  to learn or be taught the contour on the region of the part surface from which measurements are desired. Although it is contemplated that the touch sensor  230  will be utilized for this purpose, it is also possible that the software can be adapted to accept and understand a digital interpretation of the part configuration, such as via a CAD drawing. To build the part configuration map in accordance with FIGS. 11 a  and  11   b , the numerals  1  and  2  after the letters x, y, z indicate whether the motors are for the fine adjustment mounts (numeral  1 ) or for the rough adjustment mounts (numeral  2 ). To build the part map, the operator moves the head  12  by way of control over the adjustment mounts such as either via a PC Windows operating program or by controls on the remote control box. The operator moves the head to a position over each point on the part surface from which x-rays are to be directed thereat. At this position, the operator can actuate the “teach” key and the head will use the above-described “autofocus” routine to focus on the part surface. In a like manner, the operator will move the head  12  to the next position from which x-rays are to be directed at the next point on the part surface and initiate the “autofocus” sequence previously described. In this manner, each position of the head  12  will be stored in the controller so that the controller can command the head  12  to move in a precise path keeping the head  12  at a focused distance from the part positions to be measured. In addition, because of the use of the various adjustment mounts  18  as previously described, the x-ray diffraction equipment described herein can be made to automatically take measurements from fairly complex shapes without requiring any operator intervention.  
         [0073]    Further, where the equipment is used at a part site, it is desirable for the controller  135  to be adapted for generating maps of the measured strength characteristic so that an operator in the field can make ready comparisons of, for example, stress measurements to easily determine whether localized stress aberrations are present or more importantly if there undue tensile stresses that are more representative of overall fatigue affecting part life. As shown in the stress maps of FIGS.  13 A- 13 C, the areas on the maps of FIGS. 13B and 13C between the vertical lines show undesirable tensile stresses in an easy to see fashion. By providing these types of maps to field personnel at their job site, it is anticipated that the value of the x-ray diffraction equipment will be unquestionably realized.  
         [0074]    While there have been illustrated and described particular embodiments of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true spirit and scope of the present invention.