Study of Separation Mechanism and Characteristics of Ridge-Cut Explosive Bolts Using Numerical Analysis
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ORIGINAL PAPER
Study of Separation Mechanism and Characteristics of Ridge-Cut Explosive Bolts Using Numerical Analysis Juho Lee1
· Yong-Seok Kim2 · Seung-Ju Baek2 · Hyeon Su Jeong2
Received: 7 August 2020 / Revised: 22 October 2020 / Accepted: 26 October 2020 © The Korean Society for Aeronautical & Space Sciences 2020
Abstract Ridge-cut explosive bolts are a type of pyrotechnic release devices in which two connected structures are separated by explosives. They are designed such that shock waves can interact with and cut their body. Furthermore, they provide a clean separation surface and require a smaller explosive amount compared with other types of explosive bolts. In this study, ridge-cut explosive bolts of various diameters and with an exploding bridge wire (EBW) detonator were developed for use in sled testing. Their initial shapes were designed using an established procedure. Initial separation tests for the initial designs of the explosive bolts showed that considerable debris was produced for some models and that the explosive amount should be reduced. For the minimization of the number of experiments, the appropriate explosive amount was determined in advance through numerical analysis, which was performed using Autodyn, a commercial hydrocode. The numerical analysis technique used was improved to analyze the complete separation phenomena. The numerical results clearly revealed the separation mechanism and characteristics of the explosive bolts and helped determine an appropriate explosive amount for achieving a small amount of debris. Verification tests confirmed that explosive amounts determined using the numerical results were appropriate for separation and generated a small amount of debris. Keywords Explosive bolt · Pyrotechnics · Separation phenomenon · Hydrocodes · Autodyn
1 Introduction Explosive bolts are crucial devices in aircraft, spacecraft, and missile systems. In these bolts, two connected structures are separated or released by explosives. These devices involve explosives and are also referred to as pyrotechnic release devices, and they are classified into single-point separation devices, such as explosive bolts, pin pullers, and separation nuts, and linear separation devices, such as a flexible linear shaped charges [1, 2]. Various types of explosive bolts have been developed, depending on the requirements of the concerned system. The essential design requirements are that it should possess sufficient strength to connect the two structures, similar to ordinary bolts, and provide robustness against vibrations and shocks in the operating environment.
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Juho Lee [email protected]
1
Department of Aerospace Engineering, University of Ulsan, 93 Daehak-ro, Ulsan 44610, South Korea
2
The 4Th R&D Institute, Agency for Defense Development, Yuseong, P.O.Box 35, Daejeon 34186, South Korea
Depending on the separation mechanism, explosive bolts can be divided into many types, such as fragment type, pressure type, shear type, and ridge-cut type [3]. In fragment-type explosive bolts, the se
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