Pyroshock Loaded MISO Response Janet C. Wolfson* and Jason R. Foley Air Force Research Laboratory * AFRL/RWMF; 306 W. Eglin Blvd., Bldg. 432; Eglin AFB, FL 32542-5430, janet.wolfson@eglin.af.mil Alain L. Beliveau Applied Research Associates, Inc. Greg Falbo and Jeff Van Karsen LMS Americas ABSTRACT The Air Force Research Laboratory has developed a new testing method that utilizes pyroshock loading to excite a structure simultaneously over multiple axes. One of the areas of investigation in developing this test capability is the effects of multiple pyroshock loading on the output response of the test structure. A series of Single Input- Single Output (SISO) and Multiple Input-Single Output (MISO) tests have been performed using a combination of single and multiple impact hammers in different geometric configurations. The impacts were applied both simultaneously and individually. The response of the structure was analyzed evaluating the acceleration time history, Frequency Response Functions, and Shock Response Spectra. This analysis was used to determine optimum placement of the multiple input locations and desired output response for the future field tests. INTRODUCTION The Air Force Research Lab (AFRL) conducts research in a wide variety of energy regimes. This research is designed to evaluate aspects of a test article over a variety of scales from components to systems and sub-scale to full-scale. One aspect of these endeavors is the multi-axial excitation of a system over the entire frequency spectrum from low (10 Hz) to high (10 kHz) as well as different amplitudes (i.e. – accelerations). A new test article was proposed and an the initial computational study was performed. The analytical results were then compared to a similar near-field pyroshock test. [1] This analysis led to the development of the Multi-Axial Pyroshock Plate (MAPP) test set-up. Initial pyroshock tests were performed on the MAPP test set-up where acceleration time histories were captured and Shock Response Spectra (SRS) were calculated. The success of the tests was determined by comparing the SRS from the tests with a desired SRS band. These initial tests show that the technology could simulate aspects of the SRS, however, the application of the pyroshock needs further refinement. In order to determine the optimum placement of pyroshock inputs a study utilizing the Multiple InputSingle Output (MISO) methodology was performed. A series of laboratory tests were completed on a small aluminum plate. The initial tests focused on a Single Input-Multiple Output (SIMO) analysis at thirty-two different input locations and four output locations. Acceleration time-histories were captured at each location. From that data the Frequency Response Functions (FRF) and Shock Response Spectra (SRS) are calculated. The second series of laboratory tests involved performing a series of Multiple Input-Single Output (MISO) tests. The same analysis was performed on these tests and a comparison was made between the FRF’s and SRS’s of the single and multiple inputs. Based on the data analyzed from the laboratory tests initial locations of small pyroshock inputs were determined and a test plan was developed for future field tests to determine the feasibility of this approach for larger input forces. This paper will provide a brief overview of the initial MAPP field tests and discuss the results from that analysis. It will then provide a detailed discussion of the sub-scale laboratory tests and the SIMO and MISO studies that were preformed. It will show the benefits of utilizing the MISO methodology over the SIMO tests in achieving a higher magnitude of response depicted in a FRF and SRS. The paper will conclude with a brief discussion of the field tests that will be performed to verify this methodology before it is expanded to include the MAPP test set-up. T. Proulx (ed.), Modal Analysis Topics, Volume 3, Conference Proceedings of the Society for Experimental Mechanics Series 6, 533 DOI 10.1007/978-1-4419-9299-4_45, © The Society for Experimental Mechanics, Inc. 2011
RkJQdWJsaXNoZXIy MTMzNzEzMQ==