Sensitivity Analysis of Mission Critical Shear Bolts of Combat Aircraft High-Speed Flexible Coupling
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TECHNICAL ARTICLE—PEER-REVIEWED
Sensitivity Analysis of Mission Critical Shear Bolts of Combat Aircraft High-Speed Flexible Coupling S. Nagesh . A. M. Junaid Basha . Dineshsingh G. Thakur
Submitted: 15 March 2015 / in revised form: 23 April 2015 / Published online: 29 July 2015 Ó ASM International 2015
Abstract The combat aircraft utilizes high-speed flexible coupling (HSFC) to transmit the power from the aircraft engine gear box to accessory gearbox and to accommodate misalignment arises in the drive line. The HSFC input drive end has three shear bolts with predetermined shear torque set value. The mission-critical shear bolt failure to act above maximum set value will damage the down-line components by excess torque transmission. The premature action of shear bolts below minimum set value will deprive the power to single-engine aircraft transmission which may even lead to loss of aircraft. To realize consistency performance of shear bolts, sensitivity analysis is carried out considering influencing parameters like shear section size, hardness and preload variation. Based on the analysis, grouping of bolts was enabled for consistent performance in shear torques. The experimental validations are carried out to correlate between theoretical prediction and model behavior. Keywords Bolted joints Shear section Tightening torque Sensitivity analysis Experimental validation
S. Nagesh A. M. Junaid Basha Combat Vehicles Research and Development Establishment, DRDO, Chennai, India S. Nagesh e-mail: [email protected] A. M. Junaid Basha e-mail: [email protected] D. G. Thakur (&) Department of Mechanical Engineering, Defence Institute of Advanced Technology, Pune, India e-mail: [email protected]; [email protected]
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Introduction The high-speed flexible coupling (HSFC) is used in combat aircraft application to transmit 185 kW of power at high speeds typically ranging from 10,000 to 18,000 rpm from the jet engine drive to the Aircraft Mounted Accessory Gear Box (AMAGB).The HSFC is capable of accommodating larger axial misalignment that arises due to the thermal expansion of the engine and parallel misalignment resulting from flight dynamics. The HSFC utilizes nonlubricated, metallic diaphragm-type coupling [1]. With the elastic material flexure of flexible plates, lower reaction forces are transmitted to HSFC end supports due to the applied misalignments [2]. To achieve an infinite life design for HSFC, it is necessary to keep away from the different natural frequencies from the operating range of speeds apart from the optimal structural strength to accommodate larger misalignment [3]. The HSFC has three shear bolts as a set, to protect the gear boxes, from excess input torque experienced in the drive line. The shear bolt is the mission-critical components in aircraft transmission line. The shear bolt failure to act above maximum set value will damage the down-line components by excess torque transmission. The premature action of shear bolts below minimum set value will deprive the power to singl
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