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Environmental Isolation
Published in Richard Leach, Stuart T. Smith, Basics of Precision Engineering, 2017
Waiel Elmadih, Marwène Nefzi, Eric S. Buice
The required performance of isolation can be described in terms of the characteristics of the machine response. In this context, two types of responses are distinguished: the steady-state and the transient response of the machine. The steady-state response is relevant when the external excitations are of long duration, as is the case of periodic and random vibrations that occur during the operation of the machine (see Sections 13.3.5 and 13.3.6). The transient response is relevant when the machine is subject to short-duration shocks that can occur (sometimes when the machine is not in operation during handling, transport or when being installed). Steady-state responses can be characterised by the transmissibility, which is defined as the ratio of the response amplitude of a system in the steady state to the excitation amplitude. Transmissibility is, therefore, the complement of isolation; the lower the transmissibility, the higher the isolation will be. For transient responses, shock response spectra (SRS) are used to evaluate the performance of the isolation, which is a plot of the maximum response to an applied shock. Transmissibility and shock responses are discussed in Section 13.4.1.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
Shock response spectrum (SRS) - Also called shock spectrum, the SRS is a curve that indicates a theoretical maximum response as a function of pulse duration and responding system natural frequency. The shock spectrum of a waveform is an indication of the shock’s damage potential in the frequency domain.
Recent developments on the water entry impact of wedges and projectiles
Published in Ships and Offshore Structures, 2022
Ahmad Zamir Chaudhry, Yao Shi, Guang Pan
Shi et al. (2019c) investigated the cavity characteristics of low velocity projectiles with various launch parameters. The effect of head shape of projectile, impact speed and launch angle on the cavity shape, pinch-off time, pinch-off depth and cavity ripples were discussed. It was observed that the cavity diameter enhances with the increase in the half-sphere angle of the projectile head which will consequently accelerate the surface seal. Both pinch-depth and pinch-off time are influenced by the occurrence time of the surface seal. Rippling frequencies observed during experimental studies were found close to the Minnaert frequency. In another study, Shi et al. (2020) examined the frequency domain characteristics of hydrodynamic loads for air-launched AUVs using the shock response spectrum method. Experimental set-up was provided with a launcher, an accelerometer, high-resolution imaging and a data collection unit. It was observed that the peak value of acceleration shock spectrum was linked with the peak width of the impact pulse and was not associated with the peak value of the pulse.
Experimental study and numerical model adequacy assessment of hull structure dynamic response subject to underwater explosion
Published in Ships and Offshore Structures, 2020
Wenqi Zhang, Xiongliang Yao, Yinan Wang, Zhikai Wang
Figure 13 shows that the intermediate frequency band (200–1000 Hz) is basically preserved by low-pass filtering and eliminating trend terms, while the energy in the high-frequency band (above 1000 Hz) is eliminated by low-pass filtering and the energy in the low-frequency band (1–200 Hz) is eliminated by eliminating trend terms. Figure 14 shows the shock response spectrum of the pre-processed shock signal. It should be noted that the shock response spectrum here refers to the pseudo-velocity spectrum. The shock response spectrum of signal shows the characteristics of equal velocity in the middle and low-frequency bands and equal acceleration in the high-frequency bands broadly.