Journal of Vibroengineering
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A comparative study of phenomenological hysteretic models with application to recycled rubber-fibre reinforced bearings
Full text linkThe present study investigates the capability of different hysteresis models in representing the nonlinear behaviour of Recycled Rubber-Fibre Reinforced Bearings (RR-FRBs). A recently developed class of uniaxial phenomenological models is considered along with the Bouc-Wen Model (BWM). In particular, Bilinear Model (BM) and Exponential Model (EM), belonging to the class of above-mentioned phenomenological models, are used. The restoring force-displacement loops of RR-FRBs obtained from the different models are compared with the experimental studies retrieved from the literature. These first results show that the EM not only can accurately predict the behaviour of RR-FRBs, but it also requires a significantly lower computational time. Furthermore, to investigate the capability of the models in predicting the complete response of base-isolated structures, nonlinear time history analyses are carried out on a base-isolated rigid block with RR-FRBs. The response time histories of the rigid block and the restoring force-displacement loops obtained by using the EM are found to be in close agreement with the results obtained by adopting the BWM. In addition, the EM computational time is only 0.25 % of BWM. This clearly demonstrates the efficiency of EM in the seismic response analyses of base-isolated structures with RR-FRBs
Analysis of coupling fault correlation and nonlinear vibration of multi-stage gear transmission system
Full text linkIn the multistage gear transmission system, when multiple faults are coupled, the faults with weak signals are often hidden and hard to identify. Multi-fault coupling may also cause new coupling fault characteristics, such as new peaks or side bands in the spectrum. These characteristics are likely to contain fault information. Studying the sources of frequency components in coupled fault signals will help to decouple the signals and dig out the correlation characteristics between faults. The coupling fault of fixed-axis gear crack and planetary gear tooth broken was studied in this paper. The nonlinear dynamic model of the multi-stage gear transmission system was used for simulation, and the fault frequency characteristics of the system varying with the excitation frequency were obtained. The short-time Fourier transform (STFT) and waterfall plot analysis were applied to the experimental signals to separate the fault features. By comparing the theoretical and experimental signals, we found the natural frequency of the system, the side frequency characteristics of single fault and coupling fault, and the cause of new peaks. This study has a guiding significance for the separation and identification of coupling faults of the multi-stage gear transmission system
The study of damping control in semi-active car suspension
Full text linkPaper discusses apparently opposing goal functions in terms of car’s comfort and handling. Short descriptions of passive, semi-active and active suspensions with their features are included. Thereafter, employing a two-mass quarter car model, an idea of damping control strategy in semi-active car suspension is presented. The results of performed simulation tests for various inputs are depicted and thoroughly discussed with comparison to classical passive suspension’s response. On the grounds of obtained results, conclusions are formulated. What is more, a layout of further work is outlined, with the aim of system’s response optimization in terms of comfort and handling features, as well as reliable validation of efficiency of proposed damping control strategy
Effect of ply angle on nonlinear static aeroelasticity of high-aspect-ratio composite wing
Full text linkIn order to reduce the weight and improve aerodynamic characteristics, the new aircraft generally adopts lightweight composite materials and high-aspect-ratio layout. Such the structural layout aircraft will produce large nonlinear aeroelastic deformation under the action of aerodynamic loads. Due to the anisotropy of the composite, the composite ply angle of wing skin has a great influence on the elastic deformation of the high-aspect-ratio wing. In order to study the influence of the ply angle on the nonlinear static aeroelastic wing deformation, based on CFD/CSD unidirectional fluid-solid coupling, the structural deformation and stress of high-aspect-ratio composite wing were numerically solved. The wing deformation along the lift direction was taken as the optimization target. The structure strength was taken as the constraint. The ply angle for the composite skin of the high-aspect-ratio composite wing was optimized by the Screening method. The optimization results show the nonlinear static aeroelastic deformation of the wing in the lift direction is reduced by 39.1 %. The maximum stress of the wing beam and rib is reduced by 39.0 %. The maximum Tsai-Wu failure factor of the wing skin is reduced by 47.1 %
Dynamic modeling, simulation and experimental investigation on cycling-trainers equipped with suspensions considering human biomechanical characteristics
Full text linkAt present, to meet the innervation and the comfort of cycling-trainers, the trend of deploying suspension system is still upwards. However, there is no reliable dynamic model for cycling-trainers equipped with suspension systems, and the influence of the suspension damping on the dynamic responses needs to be explored. In this paper, based on a commercially available cycling-trainer with suspension systems, a non-linear dynamic model of trainer-human coupled system was established. According to the bench test, the damping coefficient of suspension dampers was measured. By the cycling test, the dynamic model was validated. The test values of the vertical acceleration of the human lower trunk are in agreement with the simulation values, in which the maximum deviation is less than 15.0 % and the root mean square deviation is less than 8.0 %. Based on the model, the influences of the damper damping on the dynamic responses were analyzed. The results show that the influence laws of the suspension damping characteristics on the human body responses vary greatly under the different riding frequencies, and an optimal damping exists to avoid excessive fatigue caused by vibration under the medium and low frequency riding conditions. The established model and the revealed rules can provide useful reference for the suspension design and optimization of cycling-trainers
On dynamics of a rotating hub-flexible rod-concentrated mass system considering rigid-flexible coupling effect
Full text linkRotating hub-flexible rod system is a typical rigid-flexible coupling dynamic mechanism, which has a wide range of industrial applications. In this paper, a comprehensive nonlinear dynamical model of a rotating hub-flexible rod-concentrated mass system considering rigid-flexible coupling effect is established to study its dynamic properties. By employing the Hamilton principle and classical beam theory, a set of differential equations of motion are derived including the couplings of the elastic deformation of the rod and the rigid rotation of the hub. The additional centrifugal force, tangential force and Coriolis force due to the rigid-flexible coupling effect are elaborated. The derived governing partial differential equations are solved by the Galerkin method. The validity of the present model is verified by a comparative study. The tip motion trajectories of the rod for the prescribed rotation, the dynamic responses of the hub and the rod for an external torque acting on the hub and the dimensionless natural frequencies of the system for the steady-state rotation are graphically presented. The influences of parameters such as rotational speed ratio, concentrated mass ratio, concentrated mass location ratio and initial eccentricity ratio on the dynamics are discussed in detail
A novel wind turbine gearbox fault diagnosis method based on ASO-VMD and NRF
Full text linkThe combination of feature extraction and pattern recognition can make it possible to realize wind turbine gearboxes based on vibration signals. However, these methods need to be constantly adjusted parameters and spend time training when processing different vibration signals, which is time-consuming. Aiming at reducing the number of parameters that need to be adjusted and training time, this paper proposes a variational mode decomposition (VMD) based on atomic search optimization (ASO) and neural random forest (NRF) fault diagnosis model. The parameters of the VMD are adaptively adjusted by the ASO, which has the advantages of less adjustment parameters. After ASO-VMD decomposition, signals will be used as the input of NRF. We evaluate our method on simulation gearbox model which is established by Solidworks and Adams. Experimental results show that our method has faster training speed and higher recognition accuracy without set many parameters manually
Gearbox fault diagnosis through quantum particle swarm optimization algorithm and kernel extreme learning machine
Full text linkGearbox is the key component of mechanical transmission system. Accurate fault diagnosis of gearbox is of great significance to ensure the operation of rotating machinery. Based on the comprehensive simulation test-bed in the laboratory, a gearbox fault diagnosis method based on QPSO-KELM is proposed. Firstly, the fault pre planting experiments of gear fault, bearing fault and gear bearing mixed fault are carried out on the comprehensive simulation test-bed. Then, the vibration signals collected are preprocessed by TSA to eliminate noise. The time domain, frequency domain and NASA feature parameters of the preprocessed signals are taken as training samples and test samples of QPSO-KELM. The experimental results show that the proposed method can effectively solve the problem of gearbox fault pattern recognition, and the fault diagnosis accuracy is higher than traditional methods, so the research has certain reference significance and engineering application value
Nonlinear dynamic response and deformation analysis of soil under the explosion shock loading
Full text linkEnergy is released during explosions, and this creates shock waves. The dynamic pressure generated from an explosion is transmitted through soil in the form of compression waves. In military engineering and industrial safety protection, soil, a blast-resistant material, is used to achieve blast resistance. This study used the blast pressure and ground acceleration measured in an experimental explosion to verify the results of finite element numerical analysis. A fluid–solid interaction numerical analysis method was employed to simulate a trinitrotoluene explosion on the ground. Through analysis of the dynamic characteristics of soil after an explosion, the relationship between the dynamic stress wave formed by the explosion and the plastic deformation of the soil was studied. The results may provide a reference for the design of blast-resistant protective soil layers
Seismic performance analysis of steel beam to CFST column connection with ductility and energy dissipation components
Full text linkConcrete-filled steel tubular (CFST) column to steel beam joint with the ductility and energy dissipation components is a type of connection which is used in prefabricated structures, to improve the capacity of connections and construction efficiency. In this paper, two different type of steel beam to CFST column connections with the penetrated high-strength bolts and end-plate are investigated, i.e., steel beam to CFST column connection with end plate (CJ-1), and T-stub bolted (CJ-2) connections. The finite element model (FEM) of steel beam to CFST column connection with the penetrated high-strength bolts under cyclic loading are conducted based on the whole process of the nonlinear explicit analysis method using ABAQUS. The feasibility of FEM is verified by a set of experimental results performed by our research group, as well as available test results from other researchers. The failure modes, bearing capacity, energy dissipation capacity and ductility and rigidity degeneration were studied. As a result, the load-displacement hysteretic loop curve of CJ-2 connection is plump. However, the hysteresis curve of CJ-1 shows pinching phenomenon. The value of buckling load and ultimate load of CJ-2 increased by 28 % and 30 % respectively, compared with CJ-1. With respect of stress analysis, the plastic strain accumulation position distribution is relatively uniform duo to the T-stub connection, avoiding the penetrated high-strength bolt early yield or fracture. The results show that the steel beam to CFST column connection with penetrated bolts and T-stub connection has good seismic capacity