Abstract:
A holder for mounting a test strip for measuring the intensity of shot peening in internal cavities includes a receptacle receiving any of multiple inserts configured to form a segment of an internal cavity of a component to be peened. The test strip defines the remainder of the cavity. The shot stream to be measured is introduce into the cavity, after which the test strip is removed and measured in the conventional manner. Accordingly, the intensity of peening in internal cavities may be measured with relative accuracy. By providing multiple inserts, intensity of peening in cavities of varying sizes may be measured by simply changing the insert.

Description:
TECHNICAL FIELD 
     This invention relates to a holder for supporting a test strip used to measure the intensity of shot peening so that the intensity of shot peening in internal cavities may be controlled. 
     BACKGROUND OF THE INVENTION 
     Shot peening is commonly used to work harden critical components. When a component is shot peened, the component is exposed to a stream of shot which impacts upon the component. However, the intensity of shot peening must be carefully controlled, because peening at intensities both above and below a critical range will not harden the component properly. Accordingly, a procedure has been developed to measure the intensity of peening. Commonly, a test strip of known dimensions is mounted on a holder, the peening apparatus is set up in the same manner as it will be used to peen the component, and a stream of shot is directed against the test strip for a predetermined time period. The test strip is then removed from the holder, at which time the test strip relaxes into a natural curvature, the magnitude of which is measured by an appropriate gage, such as the gage disclosed in U.S. Pat. No. 5,297,418. If the measured deflection of the test strip indicates peening intensity within the desired range, peening of the component may be initiated. If the measured deflection is outside of the desired range, the equipment is adjusted, a new test strip is installed in the holder, and the process is repeated. 
     The foregoing process for measuring the intensity of the peening process works well for surface peening. However, critical components often include internal bores, slots, grooves and similar internal cavities, often having a complex shape, which must be peened. The above intensity measurement process does not yield accurate readings for such internal cavities, since the shot is concentrated in a small volume and ricochets off of the walls of the cavity, thus making measurement of the peening intensity by common methods difficult and inaccurate. 
     SUMMARY OF THE INVENTION 
     The present invention provides a relatively accurate measurement of the intensity of shot peening of internal cavities. A conventional test strip is mounted in a holder which includes a receptacle receiving any of multiple inserts configured to form a segment of an internal cavity of a component to be peened. The test strip defines the remainder of the cavity. The shot stream to be measured is introduce into the cavity, after which the test strip is removed and measured in the conventional manner. Accordingly, the intensity of peening in internal cavities may be measured with relative accuracy. By providing multiple inserts, intensity of peening in cavities of varying sizes may be measured by simply changing the insert. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view in perspective of peening equipment and a component having internal cavities which must be peened; 
     FIG. 2 is a view in perspective of a test strip holder made pursuant to the teachings of the present invention; 
     FIG. 3 is an exploded view in perspective of the test strip holder illustrated in FIG. 2; 
     FIG. 4 is a top plan view of the test strip holder illustrated in FIGS. 1 and 2; 
     FIG. 5 is a view in perspective of an insert block used in the test strip holder illustrated in FIGS. 2-4; 
     FIGS. 6 and 7 are side elevational views of insert blocks similar to those illustrated in FIGS. 6 and 7 but which define cavities of varying sizes; 
     FIG. 8 is a side elevational view of the test strip holder of FIGS. 1-4; and 
     FIG. 9 is a fragmentary cross sectional view of the circumscribed portion of FIG.  8   
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1 of the drawings, a component undergoing peening is generally indicated by the numeral  10  and is supported on a table  12 . The component  10  in this case is the hub of a fan assembly for a turbofan jet engine, but may be any component having bores or grooves requiring internal peening. In this case, the component  10  includes multiple, angulated, circumferentially spaced grooves  14  on the outer circumferential surface of the component  10 . The internal surfaces of the grooves  14  are peened by a peening gun  16  of a type well known to those skilled in the art. Shot is dispensed to the peening gun  16  from a suitable source (not shown) and is accelerated by compressed air supplied to the peening gun  16  and delivered through a hollow lance  18 , from which it is discharged radially through radial openings  20 . The gun  16  is mounted for movement along the axis of the lance  18  and the lance  18  extends at an angle corresponding to the angle of the grooves so that the lance may be moved into and along the grooves  14 . Accordingly, internal peening of the grooves  14  may be effected in a manner well known to those skilled in the art. 
     As discussed above, it is necessary to measure the intensity of the peening in the slots  14 , which is commonly effected by peening a test strip of standard dimensions. However, it is also important that peening of the test strip duplicate as nearly as possible the peening of the component  10 . Accordingly, since shot will ricochet off of the walls of the groove, it is necessary to accommodate this effect in peening of the test strip, and it is also important that the position of the peening gun  16  not be changed to peen the test strip. The holder  22  permits peening of a test strip while maintaining the setup of the peening gun and also accounts for ricochet of the shot within the slots  14 . 
     Referring now to FIGS. 2 and 3, the holder  22  includes a base  24  and a test strip support  26  which includes a pivotally mounted portion  28  and a removable portion  30 . A stepped down section  32  of a cylindrical pivot member  34  is rotatably received in a bore  36  defined within upright portion  38  of the base  24 . The pivot member  34  further includes a larger diameter section  40  which is secured to the pivotally mounted portion  28  of support  26  by screws  42 , which extend through apertures  44  in portion  28  and are engaged with threaded bores  46  in pivot member  34 . Accordingly, the portion  28  is secured for pivotal movement with the pivot member  34  as the pivot member  34  pivots relative to the base  24 . A thumbscrew  48  carried by upright portion  38  extends into the bore  36  and may be tightened against the outer circumferential surface of the stepped down section  32  to thereby lock the pivotally mounted portion  28  in a desired angular orientation with respect to the base  24 . 
     A slot  50  is defined in the front face  52  of the portion  28  for locating and supporting a standard peening test strip  54  (FIG. 3) in a testing position. The slot  50  is defined by side edges  56 , 58  which engage the opposite side edges  60 , 62  of the strip  54  when the strip  54  is installed in the slot  50 , and by a raised portion  64  of the bottom edge of the slot, which engages lower edge  66  of the strip  54 . Screws  66  support the strip  54  off of the back face  68  of the slot  50 . 
     The removable portion  30  of support  26  is secured to the pivotally mounted portion  28  by a pair of thumbscrews  70  which extend through apertures  72  in removable portion  30  and are received in threaded apertures  74  in portion  28 . The removable portion  30  defines a receptacle or socket  76  which receives any of multiple insert blocks  78  (FIGS.  2 , 4  and  5 ). The insert block  78  includes an open sided recess, which is defined by a segment  82  of a circumferentially extending wall. Although the circumferentially extending wall segment  82  is illustrated as curvilinear, the circumferentially extending wall segment  82  may be of any desired shape, including complex shapes which may have linear segments. The segment  82  terminates in opposite edges  84 , 86  which define a gap G therebetween. As shown in FIGS. 2 and 4, when the insert block  78  is installed in removable portion  30  and the portion  30  is installed on the pivotally mounted portion  28  with the test strip  54  installed in slot  50 , the test strip  54  extends across the gap G such that the test strip  54  and wall segment  82  define an internal cavity. The internal cavity has an open end  88  which extends through upper face  90  of the insert block  78 . Other insert blocks, such as insert blocks  78   a  (FIG. 6) and  78   b  (FIG. 7) may be used to represent cavities having different diameters and configurations, but each of the insert blocks  78 ,  78   a ,  78   b  have the same external dimensions so that each will fit into the receptacle  76 . 
     When the holder  22  is to be used, a test strip is installed in the slot  50  and an appropriate insert block  78  is installed in the receptacle  78 . The peening equipment, including the gun  16  and the lance  18 , are set up in exactly the same way that they will be used to peen the component  10 . Before the component  10  is mounted on table  12 , the holder  22  with the test strip and insert block installed therein are placed on the table  12  below the peening gun  16 . The thumbscrew  48  is loosened so that the angle of the support  26  may be adjusted relative to the base  24  so that the lance  18  may enter the cavity defined by the wall segment  82  and the test strip  54 . The thumbscrew  48  is then tightened to lock the support  26  in position. The lance  18  is lowered into the insert block through the open end  88  and shot is discharged through the lance as the lance is moved along the wall  82  and test strip  54  (as shown in FIGS.  8  and  9 ), in exactly the same manner that the lance  18  is moved to peen the internal slots  14  of component  10 . As illustrated in FIG. 9, shot ricochets off of the wall segment  82 , which provides increased peening intensity in addition to that provided by discharge of shot through the lance  18 . Accordingly, the intensity of peening of the test strip  54  closely approximates the intensity of peening of the slots  14  of component  10 . After peening has been completed, the test strip is removed from the holder  22 , by loosening or removing the removable portion  30  of support  26  by operating the thumbscrews  70 . After the test strip is removed from the holder, the test strip will curve into a natural deflection, the magnitude of which is a function of the intensity of peening. The magnitude of the deflection is measured by using an appropriate gage, such as the gage disclosed in U.S. Pat. No. 5,297,418, in a manner well known to those skilled in the art.