Abstract
Shock response spectrum (SRS), calculated according to shock loading signal, is the primary metric for assessing the shock resistance ability of shipborne equipment. Nevertheless, the measured shock acceleration signal contains a trend term error that severely distorts the low frequency of the SRS. The accuracy of present correction methods cannot be assured due to a lack of reference. A discrete wavelet transform (DWT) and low-frequency oscillator combination method is proposed for correcting shock signals in this paper. The optimal wavelet parameters can be selected according to a low-frequency spectrum baseline fitted by the measured relative displacement to reject low-frequency trend term errors. Shock machine test results show that the average difference between the low-frequency spectrum baseline and uncorrected SRS is reduced from 89.8% to 3.2%, while the SRS slope rolled off to 5.8 dB/oct after imposing the proposed correction. The corrected SRS can faithfully show the actual shock loading characteristics of shipborne equipment in shock tests.
Highlights
Warships, inevitably, are attacked by underwater weapons in the course of battle
Underwater explosion tests are the most direct and effective approach to determine the shock resistance of shipborne equipment [3], but they are costly, labor intensive, and dependent on a great deal of material resources; they cannot be deployed at will [4, 5]. e shock tester is a mechanism that can provide mechanical shock in formation for certain smaller pieces of shipborne equipment. e shock properties are controllable and the shock can be repeated within the appropriate accuracy requirements
A novel technique comprised of discrete wavelet transform (DWT) and low-frequency oscillator data was developed in this study for shock test signal correction. e method was validated in a shock machine test. e main conclusions of this work can be summarized as follows: (1) It is difficult to accurately determine shock acceleration signals in shock resistance tests on shipborne equipment. e trend term error that is mixed within the signals severely distorts the low-frequency response and seriously affects the shock resistance assessment. e actual shock signal must be accurately restored
Summary
Warships are attacked by underwater weapons in the course of battle. Even if a warship is not directly hit, the shock wave generated by the underwater explosion can seriously damage the ship’s equipment and degrade its effectiveness [1]. e shock resistance of shipborne equipment directly affects its combat performance [2]. Shock and Vibration and Wu controlled the integral trend term error by high-pass filtering [12] These methods are not suitable for processing nonstationary and nonlinear shock signals. Even if the shock signal does not contain a trend term, the correlation coefficient of positive and negative SRS drops sharply once system damping exceeds 0.02, affecting the choice of wavelet parameters [18]. A method for quantitatively selecting wavelet parameters based on the best Pearson correlation coefficient between the corrected SRS and a low-frequency spectrum baseline is given.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
