Abstract:
According to the present invention, there is provided an apparatus for positioning a specimen to be tested relative to an external force applicator. The external force applicator is adapted for engaging the specimen for test purposes. A defined path extends between a first position away from the external load applicator and a second position underneath the external load applicator. A carriage positioned on the defined path moves relative to the external force applicator between the first position which is a loading position away from the external force applicator and the second position which is an engagement position. When the specimen is in the second engagement position, the external force applicator can engage the specimen to conduct the test.

Description:
FIELD 
     The present invention relates to an apparatus for destructively testing a specimen, and more specifically to an apparatus and method for positioning the specimen for destructive testing. 
     BACKGROUND 
     Manufactures of concrete pipe, tile, man hole sections, and the like are required by ASTM International (ASTM) to perform a number of tests on their products to insure the products meet the stringent safety and reliability demands of the ASTM standards. One of these tests is the “External Load Crushing Test by the Three-Edge Bearing Test Method,” found in ASTM C 497 (the “Crush Test”). 
     The Crush Test applies an external load to the specimen and measures the point at which it cracks. A specimen is supported on a pair of lower bearings and a load is applied through an upper bearing. The prior art is replete with machines designed specifically for the Crush Test. Most of which require the specimen to be placed on a support frame then manually cajoled into position on top of the lower bearing and underneath the upper bearing. The task is arduous and time consuming. 
     SUMMARY 
     According to the present invention, there is provided an apparatus for positioning a specimen to be tested relative to an external force applicator. The external force applicator is adapted for engaging the specimen for test purposes. A defined path extends between a first position away from the external load applicator and a second position underneath the external load applicator. A carriage positioned on the defined path moves relative to the external force applicator between the first position which is a loading position away from the external force applicator and the second position which is an engagement position. When the specimen is in the second engagement position, the external force applicator can engage the specimen to conduct the test. 
     The carriage is provided with at least two rollers on opposite lateral sides of the carriage for selectively supporting the carriage for movement along the path. The rollers are moveable between a first position wherein the carriage is supported above the path for movement along the path and a second position wherein the carriage is contiguous with a lower load beam in the path such that the external force applicator can engage the specimen and the carriage remains stationary. 
     The carriage also includes a pair of parallel bearings rectangular in cross section positioned laterally across the carriage. A first and a second moveable support adapted for synchronized longitudinal inward and outward movement with respect to the center of the carriage lowers the specimen on to the bearings. In an embodiment, centering rollers rotationally support the specimen so that the specimen is moveable to a center position with its center of gravity between the pair of parallel bearings before it is lowered on to the bearings by the outward movement of the moveable support. 
     In another embodiment, there is provided a method for destructive testing of a specimen. A specimen is positioned on a carriage, which carriage has rollers and a pair of bearing strips. The specimen is then rotated until a vertical plane bisecting the specimen is normal to a top surface of the bearing strips. The specimen is then lowered on to the bearing strips such that the load is substantially equally dispersed upon both of the bearing strips. Next, the carriage is moved to a position such that the vertical plane bisecting the specimen is in alignment with an upper bearing on an external force applicator. The carriage is lowered on to a rigid structure. Finally downward external force is applied to the specimen, in order to carry out the destructive test. 
     Other aspects, features, and embodiments of the invention will become apparent upon review of the following description taken in connection with the accompanying drawings. The invention, though, is pointed out with particularity by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
         FIG. 1  is a perspective view of an apparatus for positioning a specimen underneath an external load applicator; 
         FIG. 2  is a front view of the apparatus shown in  FIG. 1 ; 
         FIG. 3  is a side view of the apparatus shown in  FIG. 1 ; 
         FIG. 4  is a perspective view of the external load applicator of  FIG. 1  with the load applicator in a lowered position; 
         FIG. 5  is a perspective view of the carriage and the defined path for position the specimen underneath the external load applicator; 
         FIG. 6  is a side view of the carriage in two positions on the defined path for transporting the specimen along the defined path; 
         FIG. 7  is a perspective view of the carriage shown in  FIG. 6 ; 
         FIG. 8  is a side view of the carriage shown in  FIG. 7 ; and 
         FIG. 9  is a top view of the carriage shown in  FIG. 6 . 
         FIG. 10  is a flow chart for a method for positioning a specimen for destructive testing. 
     
    
    
     DETAILED DESCRIPTION 
     The drawings illustrate a preferred embodiment of an apparatus  1  for positioning a specimen (not shown) underneath an external load applicator, indicated generally by the reference numeral  100 , for the purpose of conducting an “External Load Crushing Test by the Three-Edge Bearing Test Method,” in accordance with the testing procedure required by ASTM C 497 (the “Crush Test”). The Crush Test incorporates a three-edge bearing method of loading where an upper bearing  106  presses down upon a specimen to be tested positioned on a pair of lower bearings  201 . In this method, it is required to have the specimen&#39;s center of gravity centered as near as possible between lower bearings  201  and in-line with upper bearing  106  through which the load is applied. With the specimen&#39;s center of gravity positioned between lower bearings  201 , the weight of specimen and the force applied through upper bearing  106  is equally dispersed through lower bearings  201 . Upper bearing  106  is a rigid wood beam with or without an attached hard rubber strip. Lower bearings  201  are constructed of wood or hard rubber strips and fastened to a wooden or steel beam or directly to a concrete base. The rigidity of lower bearings  201  when fastened the beam or base should not deflect greater than 1/720 of the specimen length when the maximum load is applied. 
     External load applicator  100  is comprised of one or more hydraulic rams  103  combined with a positioning beam  102  and a upper load beam  105 . Upper load beam  105  has an upper bearing  106  affixed to its underside. Upper bearing  106  engages and crushes the specimen to be tested, via the force applied by hydraulic rams  103 . 
     In the illustrated embodiment, hydraulic rams  103  are disposed between positioning beam  102  and upper load beam  105 . Positioning beam  102  and upper load beam  105  are positioned within a vertically standing frame  101 , comprised of two vertically extending, spaced-apart parallel beams  110  joined at the top by upper beam  112  and at the bottom by a lower load beam  117 , which frame  101  provides a linear path for positioning beam  102  and upper load beam  105 . 
     Positioning beam  102  is selectively positionable to accommodate the diameter of the specimen to be tested. A plurality of spaced-apart holes  111  extend along the length of each of the two vertically parallel beams  110 . A pair of hydraulically actuated pins  109  are movable by hydraulic actuators  15  which are affixed to positioning beam  102 , in order to engage in selected ones of holes  111  to hold positioning beam  102  in a selected fixed position. 
     In the preferred embodiment, positioning beam  102  is suspended from cables  113  which pass over pulley  114  affixed to the outer end of upper beam  112 . The cables  113  then pass through pulley  107  and are affixed to the beam  110 . Pulley  107  is combined with an actuator  108  that is remotely controlled. In this embodiment, hydraulically activated pins  109  are also controlled remotely. When hydraulically activated pins  109  are disengaged from holes  111 , positioning beam  102  is held in position by cable  113  and pulley  107 . Actuator  108  raises or lowers positioning beam  102  to a predetermined position by moving pulley  107  up or down. When positioning beam  102  reaches the desired position, actuator  108  will move pins  109  to engage holes  111  to fix positioning beam  102  with frame  101 . 
     Lower load beam  117  is positioned in frame  101  directly beneath upper load beam  105 . Lower load beam  117  meets the Crush Test specifications by providing a rigid steel beam with a deflection not greater than 1/720 of the specimen length when the maximum load is applied. 
     A carriage  200  is provided to support the specimen and transport the specimen along a defined path  202  that extends from a loading position away from frame  101  to an engagement position beneath frame  101  and above lower load beam  117 . In the loading position, carriage  200  is positioned such that an operator can load the specimen to be tested on carriage  200  by any suitable means, such as a fork lift. Once the specimen is loaded, carriage  200  transports the specimen to frame  101  along defined path  202  to a position above lower load beam  117 . Carriage  200  lowers so that it is contiguous with lower load beam  117 . 
     The carriage will now be discussed more specifically in reference to  FIGS. 5-8 . When the operator loads the specimen onto carriage  200 , it is placed on a load positioning assembly  204 , in order to center the specimen on lower bearings  201 . Load positioning assembly  204 , includes first and second moveable supports  205  &amp;  206 , respectively. First and second moveable supports  205  &amp;  206  are combined with one or more actuators  207  adapted for synchronized inward and outward movement with respect to carriage  200 . In the illustrative embodiment, actuator  207  is a lead screw  207 . First and second moveable supports  205  &amp; 206  each have a pair of centering rollers  210 ,  211 ,  212 , and  213 . Centering rollers  210 ,  211 ,  212 , and  213  are of sufficient quality and strength to support the specimen which may weigh several tons. Optionally, safety members  209  are combined with first and second moveable supports  205  &amp;  206  and positioned behind centering rollers  210 ,  211 ,  212 , and  213  to prevent the specimen from rolling off carriage  200 . 
     To load a specimen, the operator positions the specimen on centering rollers  210 ,  211 ,  212 , and  213 . The specimen is supported above carriage  200  to allow the operator to position lower bearings  201  underneath the specimen in accordance with the requirements of the Crush Test. Since the specimen is supported directly above carriage  200 , the operator can easily center bearings  201  underneath the specimen. 
     Specimens are unlikely to be perfectly round and often they are oval-shaped. As stated above, its desired to have the specimen&#39;s center of gravity between lower bearings  201  so that the specimen&#39;s weight is equally dispersed. The specimen is rotatably supported on centering rollers  210 ,  211 ,  212 , and  213 , which allow the specimen to rotate so that its center of gravity can be centered above the mid point between lower bearings  201 . In an embodiment, one of the centering rollers  210 ,  211 ,  212 , and  213  is driven with a drive mechanism  216 . Drive mechanism  216  turns one of rollers  210 ,  211 ,  212 , and  213  which causes specimen to rotate. The operator can automatically rotate the specimen until its center of gravity is positioned directly over and in between lower bearings  201 . 
     When the specimen is centered above lower bearings  201 , first and second moveable supports  205  &amp; 206  are driven outward away from each other to lower the specimen on to lower bearings  201 . As previously stated, the specimen is positioned on rollers  210 ,  211 ,  212 , and  213 . As opposing rollers  210 ,  211  and  212 ,  213  are driven outward and away from each other the specimen moves downward until it rests on lower bearings  201 . With the specimen on lower bearings  201  it is ready for transport along defined path  202  to the engagement position underneath upper bearing  106 . 
     Carriage  200  is supported on four rollers  220  positioned at each corner of carriage  200 . Referring to  FIGS. 7 &amp; 9 , two rollers  220  are combined with one or more motors  221  to remotely move carriage  200  along defined path  202 . Rollers  220  pivot between a position engaged with defined path  202  and a position disengaged from defined path  202  by extending and retracting cylinder  223 . Rollers  220  are enclosed by a substantially triangular shaped pivot assembly  224 . Cylinder  223  is combined between the apex of pivot assembly  224  and carriage  200  and pivots about a pivot point  225 . Each of cylinders  223  are remotely controllable to uniformly raise and lower carriage  200 . 
     When carriage  200  arrives at the engagement position with the specimen underneath upper bearing  106  and above lower load beam  117 , rollers  220  are pivoted upwardly to engage carriage  200  contiguous with lower load beam  117  of external load applicator  100 , such that upper bearing  106  can engage the specimen and carriage  200  remains stationary. 
     Although the drawings have illustrated carriage  200  that moves along defined path  202 , similar principles apply to a stationary carriage  200  with a moveable frame  101  along a defined path  202 . Moreover, the principles are applicable to a method for positioning a specimen for destructive testing. The method begins by placing the specimen on centering rollers  210 - 213  of carriage  200  and positioning lower bearing  201  underneath the specimen. The specimen is then rotated until a vertical plane bisecting the specimen is normal to a top surface of lower bearings  201 . Once the specimen is centered, it is lowered on to lower bearings  201 , such that the weight is substantially equally dispersed upon both of lower bearings  201 . The specimen is then positioned with respect to upper bearing  106 , such that the vertical plane bisecting the specimen is in alignment with upper bearing  106 . When the specimen is aligned with lower bearings  201 , a first and second moveable support  205  &amp;  206 , respectively are moved outward to lower the specimen on to carriage  200 . Rollers  220 , that support the carriage  200 , are pivoted upward to lower the carriage to a stationary position. Finally, external force is applied to the specimen through upper bearing  106 . 
     Having thus provided a disclosure in connection with the preferred embodiments thereof, it will be evident to those skilled in the art that various revisions can be made to the preferred embodiments described herein without departing from the spirit and scope of this disclosure. It is my intention, however, that all such revisions and modifications that are evident to those skilled in the art will be included within the scope of the following claims.