Article of the Year 2021
Remaining Useful Life Prediction of Rolling Bearings Based on Multiscale Convolutional Neural Network with Integrated Dilated Convolution BlocksRead the full article
Shock and Vibration publishes papers on all aspects of shock and vibration, especially in relation to civil, mechanical and aerospace engineering applications, as well as transport, materials and geoscience.
Chief Editor Dr Tai Thai is based at the University of Melbourne and his current research focuses on high strength materials for sustainable construction of buildings, bridges and other infrastructure.
Latest ArticlesMore articles
Seismic Response and Damage Analysis of Large Inverted Siphon Structure
Large-scale inverted siphon is a key hydraulic structure for building a national water network and realizing the spatial balance of water resources, and its safety under the action of earthquakes has become the focus of trans-basin water transfer projects. In this paper, Xiazhuang inverted siphon of water diversion in Central Yunnan is taken as the research object. Viscoelastic artificial boundary was used to simulate seismic waves spread in the soil, which include the natural site seismic waves and the waves fitted manually according to the site conditions. A three-dimensional finite element model of soil-structure-fluid interaction was established by software of ABAQUS, in which the fluid-structure interaction was simulated by user-defined element (UEL) built on additional Mass Method. Seismic response and damage analysis of large inverted siphon structure are carried out by the model. The results show that the dynamic displacement of the inverted siphon pipe is mainly horizontal sloshing, and the dynamic response of the pipe increases due to the water in the pipe; even the dynamic stress value in some areas is close to the design value of the concrete tensile strength. The damage analysis of inverted siphon pipe shows that the plastic deformation and the damage area develop rapidly with the increase of the peak ground acceleration (PGA), and the tensile damage area is generally larger than the compression damage area. The damage factor of the pipe under the working condition of the water is obviously larger relative to the working condition of no water. Therefore, it is suggested that the damage effect of earthquake should be considered in the design of large inverted siphon in high-intensity area.
Free Transverse Vibration of Circular Plate of Stepped Thickness with General Boundary Conditions by an Improved Fourier–Ritz Method
In this investigation, free vibration of stepped circular Mindlin plate with arbitrary boundary conditions is presented by an improved Fourier–Ritz method. Based on the locations of the step variations, the stepped circular plate can be divided into different concentric annular and circular plates. The first-order shear deformation plate theory is employed to establish the theoretical model. Once all the displacements of a stepped circular plate are expanded by an improved Fourier series expansion, an exact solution can be obtained based on the Rayleigh–Ritz procedure by the energy function of the current model. The convergence and accuracy of the proposed method are proved by several numerical examples. The effects of classical boundary conditions and geometrical parameters on the frequency parameters of a stepped circular plate are also analyzed.
Active Vibration Control of a Large Flexible Appendage Using a Novel Joint Mechanism
With the evolution of space exploration, large flexible appendages have been developed in space structures. External perturbation or attitude maneuvering stimulates the vibration (low frequencies) of the aforementioned structures. In this research, a novel joint mechanism was developed in conjunction with active control to inhibit the low-frequency vibration of a large flexible appendage. A compact active joint, based on the idea of electromagnetic direct drive, was designed. The dynamic equations for the large flexible appendage system and the active joint were derived using the Lagrange function with the assumed-modes approach. Single- and multi-frequency excitations were simulated by two noncontact strategies for periodic vibration stimulation along the direction of rotation. The research results revealed that the interference signal had a primary frequency bandwidth of 0.07–0.63 Hz, and the vibration attenuation was prominent between 5.95 and 32.41 dB within the valid bandwidth. Effective inhibition of both the larger and the smaller amplitude vibrations at frequencies lower than 1 Hz could be realized using the proposed active joint without attachment of intelligent materials onto the flexible appendage surface.
Geometrical-Feature-Preserving Adjoint Tomography of Near-Surface Structure with Seismic Early Arrival
Early arrival waveform inversion (EWI) is an essential approach to obtaining velocity structures in near-surface. Due to suffering from a cycle‐skipping issue, it is difficult to reach the global minima for conventional EWI with the misfit function of least-squares norm (L2‐norm). Following the optimal transportation theory, we developed an EWI solution with a new objective function based on quadratic‐Wasserstein‐metric (W2-norm) to maintain the geometric characteristics of the distribution and improve the stability and convexity of the inverse problem. First, we gave the continuous form of the adjoint source and the Frechet gradient of the Wasserstein metric for seismic early arrival, which leads to an easy and efficient way to implement in the adjoint-state method. Then, we conducted two synthetic experiments on the target model containing some velocity anomalies and hidden layers to test its effectiveness in mapping accurate and high-resolution near-surface velocity structure. The results show that the W2-normed EWI can mitigate cycle-skipping issues compared with the L2-normed EWI. In addition, it can deal with hidden layers and is robust in terms of noise. The application to a real dataset indicates that this new solution can recover more details in the shallow structure, especially in the aspect of dealing with hidden layers.
High-Speed Penetration Test and Numerical Simulation of Ceramic-Reactive Powder Concrete Composite Target
To study the protective performance of ceramic materials against the high-speed penetration of projectiles, seven ceramic-reactive powder concrete (C-RPC) composite targets were designed. Using a 100/30 mm two-stage light-gas gun, penetration tests were performed at 1.4–2.0 km/s. The results showed that the penetration depth of the C-RPC target body first increased and then decreased as the target speed increased, and the corresponding reverse penetration speed was between 1743.2 m/s and 1803.9 m/s. LS-DYNA software was used to perform a wide-speed numerical simulation study of a projectile’s high-speed penetration of the composite target, focusing on the analysis of the deformation, mass loss, passivation, and penetration depth of the projectile. Changes in the parameters were compared with the experimental results of a C-RPC penetration test, which together revealed the changes in the damaging effect of the missile’s high-speed penetration of the C-RPC composite target. It provided a damage analysis of the high-speed/super-high-speed penetration of the projectile, which provides a reference for targeted protection research.
Formation of an Explosively Formed Penetrator Warhead Using a Step-Shaped Charge
In this study, the formation mechanism of an explosively formed penetrator (EFP) with tail fins was analyzed. Through static denotation and dynamic flight tests, the feasibility of using a step-shaped liner during the formation of an EFP with tail fins was verified. The influences of the step depth, h, and the step angle, Φ, on the flight stability were then explored. Based on the consistency between the numerical simulation and experimental results, the influences of the step-shaped liner’s spherical arc radius, number of steps, and wall thickness on the formation and flight stability of an EFP with tail fins were further studied. The results showed that a T2 copper step-shaped liner performed better than a H90 brass liner. Compared with a hemispherical liner with an equal wall thickness, the step-shaped liners resulted in EFPs with initial angular velocities and relatively better flight stability. Moreover, a greater initial angular velocity led to a higher EFP landing accuracy.