Analytical Evaluation of Design Margins for Force Limited Vibration Testing of Electro-optical Payloads. (2015)

• Record Type: Journal Article
• Authors: Singh, Sandeep Kumar; Yadav, Yeshpal; Verma, Anurag; Desai, Jaimin; Dewan, Chirag
• Is Part Of: Procedia engineering. Volume 114(2015)
• Page Start: 369
• Page End: 376
• Publication Date: 2015
• Subjects: FLVT -- Vibration -- Random -- Electro-optical -- Stress.; Engineering -- Congresses; Engineering -- Periodicals; Engineering; Conference proceedings; Periodicals; 620.005
• DOI: 10.1016/j.proeng.2015.08.081
• Languages: English
• ISSNs: 1877-7058

Abstract

Abstract: Optical payloads comprise optical elements like lens or mirrors which are fragile and most susceptible to failure. It is paramount that the design enables the payload to give best performance in terms of optical parameters and survivability is the rudimentary design constraint. Simulation is carried out based on the load levels on a vibration shaker with prescribed input given to the shaker bed.Since the mechanical impedance for the shaker bed is infinite, the constraint forces are higher than what would actually be observed due to the dynamic absorber effect. NASA provides a semi-empirical method which enables us to compute the force limit spectrum based on the payload and deck model. This provides a notched input spectrum which alleviates over testing of the payload. Fabrication of optical elements is a costly affair, so physical testing cannot be carried out until confidence is achieved regarding stress levels in the optical element. This calls for a methodology for analytical stress prediction. In this manuscript, we demonstrate a methodology to predict stresses in components analytically after predicting the notched input profile based on force limits before proceeding to testing at full level. We have also established a methodology to calculate sum of constraint forces in case of multiple constraint system taking into account the phase of the forces.FE and programming tools have been used in this work.A methodology which instils confidence in designer to test optical payloads at full level was successfully developed and demonstrated on an electro-optical payload. Stress profiles were computed analytically on all mirrors before going for actual testing.