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Innovative Approach to Low Cost Shock Testing Fixture for Medium Weight, Shock Isolated Equipment


OBJECTIVE: Design, develop, and validate a low frequency deck simulating fixture for the Medium Weight Shock Machine that is a low cost alternative to Floating Shock Platform testing of medium weight deck mounted equipment. DESCRIPTION: Shock testing and qualification is essential to the certification process of critical equipment installed in submarines. Shock qualification testing must adequately simulate the environment and input forces to ensure a level of resistance to shock, see reference 2. Currently, shock qualification testing of Class II medium weight (500-4500 lb) submarine equipment requires underwater explosion (UNDEX) testing utilizing a Floating Shock Platform (FSP). The conduct of a UNDEX testing against a Floating Shock Platform is substantially more expensive than testing on a Medium Weight Shock Machine (MWSM), see reference 1 and 3 below. It is not currently permissible to test Class II medium weight equipment on the more cost effective machine because there is no existing MWSM fixture/method that adequately simulates the dynamic environment. Currently, no fixture or method exists for the MWSM that allows for Class II medium weight equipment testing on a MWSM. As a result, medium weight Class II equipment has to be shock tested on FSPs which is substantially more expensive and schedule intensive than testing on a MWSM. Testing on a MWSM is on average $20k, approximately five times less expensive than testing on a FSP. Although medium weight Class II equipment is light enough to be mounted in a MWSM, a technology, technique, or fixture does not exist that sufficiently replicates the low frequency during a FSP shock event. This SBIR topic seeks an innovative and cost efficient solution for shock testing of medium weight Class II equipment. Solutions need to integrate with MWSM, simulate FSP deck responses, and replicate low frequency shock events and be tunable to 7, 10, 14, 20, and 28 Hz, see reference 3 below. PHASE I: Develop solution concepts that will be able to determine the motion characteristics of the FSP inner-bottom and deck simulation fixtures. Concepts should be developed using available FSP test data and modeling and simulation techniques. Develop and analyze a solution concept compatible with a MWSM that can produce motions similar to the FSP inner-bottom and a tunable deck fixture. The concept must provide all of the potential damage producing mechanisms that are produced on the FSP and deck simulation fixture. PHASE II: Prototype and implement the proposed solution concept on a MWSM and construct a tunable deck simulation fixture for a MWSM. Validate the design by comparing the MWSM test results with MIL-S-901D FSP results. Develop a process for shock qualification testing of Class II medium weight equipment on the MWSM. PHASE III: If the Phase II is successful, the company will be expected to support the Navy in transitioning the technology for Navy use. The company will be expected to finalize fixture design and shock qualification testing process and complete certification process for test labs. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Most shock testing, for submarine and surface ship platforms, is performed at private test labs. Vendors, who develop Commercial Off the Shelf (COTS) equipment for military applications, may also use the test fixture and process to verify their COTS designs for non-military applications, such as commercial transportation. REFERENCES: 1. Clements, E.W."Shipboard Shock and Navy Devices for its Simulation", Naval Research Laboratory Report NRL 7396, July 14, 1972. 2. O"Hara, G.J."Effect upon shock spectra of the dynamic reaction of structures", Experimental Mechanics, 1961. 3."Shock Tests, H.I. (High-Impact) Shipboard Machinery, Equipment, and Systems, Requirements For", MIL-S-901D Amended by Interim change #1.
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