Impact force identification in structures using time-domain spectral finite elements
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O R I G I NA L PA P E R
Raghavendra B. Kulkarni Manish Trikha
· S. Gopalakrishnan ·
Impact force identification in structures using time-domain spectral finite elements
Received: 8 March 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract During the launch and subsequent life of a spacecraft, there are various transient loads due to stage separation and micro-meteorite impact which a spacecraft structure must be designed to withstand. However, the force histories for these transients at these locations are not available to design the structure due to practical considerations like mounting of instrumentation. To address this problem, a new algorithm for performing impact force identification based on time-domain responses measured at various locations is proposed. The time-domain spectral finite element model is adopted as it requires a fewer number of measured responses which clearly has an advantage with respect to conventional finite element method. Hence, we use time-domain spectral finite element method, to generate the mass, stiffness, and damping matrices, which are required to perform force identification. Experiments are performed to obtain the time-domain responses on the beam and portal frame structures on which force identification is performed. The efficiency of the new algorithm is demonstrated using a variety of responses and different one-dimensional structures. However, the proposed algorithm is general in nature and can be used for one-, two-, and three-dimensional structures and with conventional generalized finite element model. The results from the proposed algorithm show an excellent match between the reconstructed force histories and the experimentally measured force.
1 Introduction During the launch and subsequent life in orbit for a spacecraft, there are various transient loads due to stage separation, heat shield separation, and on orbit micro-meteorite impact which a spacecraft structure must be designed to withstand. However, the force histories for these transients are not available to design the structure due to practical consideration of mounting of the instrumentation. Hence, we measure various responses at different locations and reconstruct the force histories. There are two kinds of problems in mechanics: one is the forward problem solved using the conventional analysis where the input force is known and responses are to be computed, and the other is the inverse problem where the cause (force) is to be determined knowing the responses. There are two classes of inverse problems: in the first, if the responses at one or few locations are known, one has to identify the forces causing these responses, and the process of determining the forces from the measured responses is normally referred to as “force identification problems.” In the second type of R. B. Kulkarni (B) UR Rao Satellite Center, Indian Space Research Organisation, Vimanapura Post, Bengaluru 560019, India E-mail: [email protected] S. Gopalakrishnan Department of Aerospace Engineering, Indian In
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