Abstract:
A method of simulating dropping of a box on an impact specimen is disclosed. An illustrative embodiment of the method includes providing an impact head simulating a corner of a box, providing an impact specimen, causing impact of the impact head with the impact specimen and examining the impact specimen. A method of simulating dropping of a box on an impact specimen is also disclosed.

Description:
FIELD OF THE INVENTION 
   The present invention relates to box drop impact tests for testing floor panels. More particularly, the present invention relates to an impact head and method which simulates impact of an edge or corner on a box against an impact specimen in a box drop impact test. 
   BACKGROUND OF THE INVENTION 
   Cargo compartment flooring in the cargo compartment of an aircraft is required to withstand certain minimum weight and drop test standards. Typically, cargo compartment flooring includes multiple floor panels which are attached to permanently installed transverse and longitudinal beams. For example, a floor panel which is 18 inches square and supported at two edges must be able to sustain, without failure, a minimum of 2,000 pounds applied over an area which is 1 inch in diameter in the center of the panel. The upper surface of the cargo compartment flooring must be adapted to support a load of 400 pounds which is applied by a ¾ inch diameter steel ball without failure or permanent indentation which is greater than 0.05 inch. 
   A floor panel must be sufficiently strong to withstand, without failure, impact from a sturdily-constructed pine box which is uniformly-loaded such that the box and its contents weigh 200 pounds and is dropped from a height of 13 inches above the panel (distance between the panel and the lowest corner of the box) such that one corner of the box strikes the center of the panel. A line between the center of gravity of the box and the contact point with the floor panel is vertical upon impact. The corner radius of the box cannot exceed ½ inch. The local deformation in the floor caused by the impact cannot exceed 0.3 inches. One of the limitations of the conventional box drop method for testing floor panels of aircraft cargo compartments, however, is that the method is time-consuming and expensive. 
   SUMMARY OF THE INVENTION 
   The present invention is generally directed to a method of simulating dropping of a box on an impact specimen is disclosed. An illustrative embodiment of the method includes providing an impact head simulating a corner of a box, providing an impact specimen, causing impact of the impact head with the impact specimen and examining the impact specimen. 
   The present invention is also generally directed to an impact head which simulates a corner of a box. An illustrative embodiment of the impact head includes an impact head base, a pair of head surfaces provided in the impact head base, a head ridge joining the pair of head surfaces and an impact point at an end of the head ridge. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a side view of an impact head suitable for implementation of the invention. 
       FIG. 2  is a top view of the impact head. 
       FIG. 3  is a front view of an impact apparatus, with an illustrative embodiment of the impact head of the invention mounted on a load cell of the impact apparatus prior to impact of the impact head with an impact specimen (shown in phantom). 
       FIG. 4  is a front view of an impact apparatus, after impact of the impact head with the impact specimen (shown in phantom). 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring initially to  FIGS. 1 and 2 , an illustrative embodiment of the impact head according to the invention is generally indicated by reference numeral  1 . The impact head  1  is shaped to simulate the corner of a wooden box in a box drop impact test, which will be hereinafter described. The impact head  1  is a wood such as pine, for example, and typically includes an impact head base  2  having a generally flat or planar base surface  2   a . A shaft opening  8  extends into the base surface  2   a . In a typical embodiment of the impact head  1 , the shaft opening  8  is 0.5″ in diameter. The impact head base  2  has a pair of angled or sloped head surfaces  3 . The head surfaces  3  taper to join each other along a head ridge  5 . The head surfaces  3  have head edges  4  which join at an impact point  6  at one end of the head ridge  5 . Typically, the corner radius of the impact point  6  does not exceed about ½ inch. As shown in  FIG. 1 , wood grains  7  of the impact head  1  are oriented at a generally 45-degree angle with respect to the plane of the base surface  2   a.    
   Referring next to  FIGS. 3 and 4 , an impact testing apparatus  16  in typical implementation of the impact head  1  is shown. The impact testing apparatus  16  may be, for example, a conventional Dynatup® impact testing apparatus. The impact testing apparatus  16  typically includes an impact platform  17  having multiple platform legs  18  and a platform panel  19  supported by the platform legs  18 . A head opening  20  extends through the platform panel  19 . Multiple rebound brakes  29  extend from the platform panel  19  of the impact platform  17 . Rails  22  extend upwardly from the respective rebound brakes  29 . An impact frame  24  extends from the impact platform  17 . A release box  25  is supported by the impact frame  24  and detachably supports a weight  27  through a releasable hook  26 . An elongated load cell  28  extends downwardly from the weight  27 . The weight  27  is slidably mounted on the rails  22  of the impact testing apparatus  16 . 
   In typical application of the invention, the impact head  1  is used in conjunction with the impact testing apparatus  16  to test the strength of an impact specimen  35  (shown in phantom in  FIGS. 3 and 4 ), such as a floor panel which is to be used as flooring in a cargo compartment of an aircraft, for example. The impact head  1  is fabricated to simulate the corner of a wooden box having a selected weight in the simulated dropping of the box on the impact specimen  35  in order to test the strength of the impact specimen  35 . The impact specimen  35  is typically supported beneath the platform panel  19  of the impact platform  17  on a pair of spaced-apart specimen support blocks  34 . In typical application, the impact specimen  35  is 18″ square. Each of the specimen support blocks  34  is 18″ long and 1″ wide. The impact specimen  35  is placed across the specimen support blocks  34  to simulate suspension of the impact specimen  35  between two plates in a typical box drop test. 
   The magnitude of the weight  27 , which corresponds to the weight of a wooden box in an actual box drop test, is selected. In a typical simulated box drop test, the weight  27  is 200 lbs., although the magnitude of the weight  27  may be lesser or greater depending on the desired application of the impact head  1 . The impact head  1  is attached to the load cell  28  typically by threadably inserting a threaded shaft (not shown) provided on the load cell  28  into the shaft opening  8  of the impact head base  2 . The weight  27  is supported by the release box  25  by causing engagement of the release hook  26  with the weight  27 . The distance between the impact point  6  of the impact head  1  and a contact point  36  on the surface of the impact specimen  35  is typically about 13 inches. Furthermore, the impact point  6  of the impact head  1  is directly vertical with respect to the contact point  36  on the surface of the impact specimen  35 . 
   The weight  27  is released from the release box  25  typically by lever-actuated disengagement of the release hook  26  from the weight  27 . Accordingly, the weight  27  slides downwardly on the rails  22  until the impact head  1  extends through the head opening  20  in the platform panel  19  and then the impact point  6  of the impact head  1  strikes the contact point  36  on the impact specimen  35 . The wood grains  7  of the impact head  1  are oriented at a generally 45-degree angle with respect to the plane of the impact specimen  35 . The weight  27  is then raised on the rails  22  and re-attached to the release hook  26 , after which the contact point  36  on the impact specimen  35  is examined. In applications in which the impact specimen  35  is an aircraft cargo compartment floor panel, the local deformation in the impact specimen  35  at the contact point  36  typically must not exceed 0.3 inches to pass the box drop test. 
   Although this invention has been described with respect to certain exemplary embodiments, it is to be understood that the specific embodiments are for purposes of illustration and not limitation, as other variations will occur to those of ordinary skill in the art.