MULTI-AXIAL PYROSHOCK PLATE (MAPP) SET-UP The initial study of the Multi-Axis Pyroshock Plate (MAPP) test set-up occurred in April 2010. The test article consists of a 4’ x 8’ x 1” thick T6061 aluminum plate that is hung from an aluminum tube by turn buckles. They suspend the plate in simulated Free-Free boundary conditions. The aluminum tube that supports the MAPP test system spans 22’ and is connected to concrete blast walls through the use of 3/8” expansion anchors. A “bookshelf” has been welded to the front of the plate, it is 6” long and is constructed out of T6061 Aluminum tube stock. The nominal dimensions on the tube stock are 6” x 6” x ½”. Figure 1(a) depicts the entire plate with the bookshelf. Figure 1(b) shows a closer view of the bookshelf and a steel plate that is attached to it. In order to allow for the connection of the steel plate, or any other test article, to the bookshelf a series of 8 - 0.32” diameter thru holes were drilled into the bookshelf. A standard x-, y-, z, coordinate system is assumed for this test article. The x-axis runs along the long side of the plate [along the bottom edge of the plate shown in Figure 1(a)] while the y-axis is located parallel to the short side of the plate [along the left hand side of the plate in Figure 1(a)]. The origin of the coordinate system is located at the lower left hand corner of the plate in the photo below. The z-axis comes out of the plate and runs along the 6” length of the bookshelf. This coordinate system will be used in the discussion of the results for both the field and laboratory tests. a) Overall MAPP Test Set-up b) view of “bookshelf” and steel plate Figure 1 MAPP test article A series of four tests were performed using small amount of explosive near the center of the plate. Two of the tests utilized a custom AFRL tri-axial mount that housed three shock accelerometers placed in the center of the steel plate attached to the bookshelf. The other two tests utilized a component centered on the bookshelf with the same AFRL tri-axial mount and accelerometers placed within it. The component was attached to the bookshelf through a series of bolts. INITIAL TEST RESULTS In the complex environment that AFRL is interested in there is an accepted methodology of developing test requirements using a Shock Response Spectrum (SRS), which was used as our initial figure of merit. The SRS has been proposed as a tool for evaluating the damage potential in a given acceleration time history. The SRS is defined using an array of 1-D spring-mass systems, each with a spring constant tuned to a different resonant frequency ( ω = √k/m). The maximum acceleration by an oscillator when coupled to a rigid base moving with the specified acceleration time history defines the “positive” or “negative” SRS depending on the direction of the shock. Further details on the SRS can be found in comprehensive reviews, e.g., Irvine [2]; other spectral 534
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