Stability and integrity of mechanical joints in flight vehicles: Local and global energy density |
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| Authors: | GC Sih CH Chue |
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| Institution: | 1. Institute of Fracture and Solid Mechanics, Lehigh University, Bethlehem, PA 18015, USA;2. Department of Mechanical Engineering, National Cheng Kung University, TainanTaiwan, China;1. Department of Oculoplastic, Orbital, and Lacrimal Surgery, Aichi Medical University Hospital, 1-1 Yazako-Karimata, Nagakute, Aichi 480-1195, Japan;2. Department of Anatomy, Aichi Medical University, 1-1 Yazako-Karimata, Nagakute, Aichi, Japan;3. Department of Pathology, Aichi Medical University, 1-1 Yazako-Karimata, Nagakute, Aichi, Japan;1. Orthopaedic Department, AZ Groeninge, President Kennedylaan 4, 8500 Kortrijk, Belgium;2. GRECMIP - MIFAS (Groupe de Recherche et d’Etude en Chirurgie Mini-Invasive du Pied - Minimally Invasive Foot and Ankle Society), Merignac, France;3. Department of Development and Regeneration, KU Leuven, Leuven, Belgium;4. Department of Orthopaedics, Foot and Ankle Unit, University Hospitals Leuven, KU Leuven, Leuven, Belgium;5. Institute of Orthopaedic Research and Training, KU Leuven, Leuven, Belgium;6. Dept. Development and Regeneration, Faculty of Medicine, University of Leuven Campus Kortrijk, Etienne Sabbelaan 53, 8500 Kortrijk, Belgium;7. Radiology Department, AZ Groeninge Kortrijk, President Kennedylaan 4, 8500 Kortrijk, Belgium;1. Department of Rehabilitation Medicine, Changi General Hospital, Singapore;2. Rehabilitation Medicine, SingHealth Residency, Singapore;3. Department of Rehabilitation Medicine, Singapore General Hospital, Singapore;1. College of Aeronautics, Northwestern Polytechnical University, 127 West Youyi Rd., Beilin District, Xi''an, Shaanxi, 710072, PR China;2. National Key Laboratory of Science and Technology on Liquid Rocket Engine, 289 Feitian Rd., Aerospace Base, Xi''an, Shaanxi, 710100, PR China |
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| Abstract: | A methodology is presented for analyzing the inlfuence of mechanical joint failure on the global instability of flight vehicles. Considered are the ways with which loading, geometry and material of the vehicle can affect the structure instability and/or integrity. The peaks and valleys of the volume energy density function are assumed to coincide with failure by fracture and/or yielding while the distance between their local and global stationary values govern the structure instability. A single length parameter l can thus be applied to provide a measure of stability. The simultaneous occurrence of high energy density and large l at the same location should be avoided as it may have undesirable consequences.A flight vehicle consisting of four cylindrical shell-like structures connected by three tongue-and-groove joints is analyzed. The time-dependent load can be axisymmetric or non-axisymmetric. A semi-analytical finite element program is developed and used to solve for the transient stress and strain distribution from which contours of the volume energy density in the structure are obtained as a function of time. The magnitudes and locations of their local and global stationary values are then calculated and discussed in connection with potential failure by fracture. Stability behavior does not alter appreciably for axisymmetric flight. Considerable fluctuations in the energy density and the dynamic stability length parameter are found when non-axisymmetric loads are considered. |
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