Dynamic Characteristics Of Model Research Articles

Modeling of the nonlinear dynamic degradation characteristics of fiber-reinforced composite thin plates in thermal environment

In this research, the nonlinear dynamic degradation characteristics of fiber-reinforced composite plates in thermal environment are investigated through a novel dynamic degradation model, which is established by introducing the thermal and time fitting coefficients simultaneously to express dynamic elastic moduli of such composite materials. Based on the classical laminated plate theory, the improved exponential function method, the complex modulus approach and the Ritz method, the dynamic equations are derived to solve the dynamic parameters. Besides, a particle swarm optimization algorithm is employed to iteratively calculate dynamic elastic moduli, and the nonlinear least squares technique in MATLAB software is utilized to draw the three-dimensional fitted surfaces of dynamic elastic moduli, degradation time and temperature data, so that the concerned fitting coefficients in the model developed can be identified. In order to validate the dynamic degradation model, experimental measurements of E120 carbon fiber/ FRD-YG-03 resin composite thin plates are undertaken. The first three natural frequencies, resonant responses and modal damping ratios obtained from the model are compared with experimental results at different degradation time and stabilized thermal environment, which are shown to be in good agreement. Also, the specific influences with and without consideration of the degradation behavior on the dynamic characteristics are investigated and evaluated.

Dynamic Modeling of the Drying Process of Corn Grains using Neural Networks

This study examines the model development of the drying process of corn grains as a dynamic system. The appropriate use of a dynamic model for the drying process of corn grains could lead to an effective method for optimizing the system. The optimal control strategy can be determined by predicting the future behaviors of the process using a dynamic model. In this work, the dynamic characteristic of the water loss of corn grains during dynamics treatment of temperature in the drying process was measured in a continuous manner using a precise load cell. The nonlinear autoregressive with external input (NARX) neural network is used to identify and develop a model of dynamic characteristics of the drying process of corn grains. Then for model training and validation, the dynamic responses of the rate of water loss of corn grains to drying temperature were used. A three-layered NARX neural network model consists of 1-10-1 number neurons of each layer with two times delay was successfully developed to identify and make a model such a complex system. The developed model showed the accuracy of the rate water loss of corn grains during the drying process with the mean square error (MSE), and coefficient of determination (R-squared) values are 1.88892 x 10-4 and 0.891594 consecutively.

Modeling of nonlinear dynamic characteristics and experimental study of piezoelectric energy harvesters with a panel type structure

Panel flutter vibration is a typical aeroelastic phenomenon taking place in flying aircrafts as they move at high speed. The vibration has been a hot academic research aspect. The present paper focuses on converting this aerodynamic mechanical vibration into useful electricity by using piezoelectric patches. A mathematical Euler-Bernoulli distributed model of the piezoelectric energy harvesting system is established to investigate nonlinear dynamical behaviour of a piezoelectric cantilever plate. The dynamical responding ability of energy harvesting is numerically calculated. Influences of the length and the thickness of piezoelectric layer, the external resistance and wind velocity on the output performance are emphatically explored. A series of prototypes of piezoelectric energy harvesters with different physical dimensions were designed and manufactured. Wind tunnel experiments were setup and carried out at different wind velocities. The experimental results show that the harvesting power gets enhanced as increasing the wind velocity. The maximum power could be obtained at condition of a reasonable piezoelectric length and width. Maximum power is 2.0 mW at wind speed of 11.0 m/s. This work provides a strong theoretical and experimental basis for the study of aerodynamic energy harvesting from panel aircrafts.

Stability Research Considering Non-Linear Change in the Machining of Titanium Thin-Walled Parts.

Aiming to solve the problem whereby the damping process effect is significant and difficult to measure during low-speed machining of titanium alloy thin-walled parts, the ploughing coefficient of the flank face is obtained based on the frequency-domain decomposition (FDD) of the measured vibration signal and the energy balance principle, and then the process-damping prediction model is obtained. Aiming to solve the problem of non-linear change of dynamic characteristics of a workpiece caused by the material removal effect in the machining of titanium alloy thin-walled parts, a prediction model of dynamic characteristics of a workpiece is established based on the structural dynamic modification method. Meanwhile, the effect of material removal on the process-damping coefficient is studied, and the internal relationship between the process-damping coefficient and the dynamic characteristics of the workpiece is revealed. The stability lobe diagram is obtained by the full discretization in the titanium alloy milling process. The correctness of the model and stability prediction is verified by experiments under different working conditions. It is found that the coupling characteristics of process-damping and workpiece dynamic characteristics control the stability of the milling process. The research results can provide theoretical support for accurate characterization and process optimization of titanium alloy thin-walled workpiece milling.

Simulation Modeling of Dynamic Characteristics of Sea Crossing Bridge under Wind Invasion

Che, X., 2018. Simulation modeling of dynamic characteristics of sea crossing bridge under wind invasion. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 93–97. Coconut Creek (Florida), ISSN0749-0208.In order to improve the large deformation and vibration of the bridge under the dynamic action of wind, the stability of the bridge structure and the safety of the train operation are improved. A modeling method for dynamic feature change based on wind load is proposed. The dynamics characteristic model of bridge is established firstly. The modal synthesis method is adopted to analyze the whole vibration of the bridge structure, to greatly reduce the dynamic degree of freedom as well as the deformation and vibration of the bridge, and improve the stability and safety of the bridge structure. Then the dynamic characteristics of the bridge under the wind load are analyzed. The experimental results show that the proposed method can improve the stability of bridge structure and reduce the deformation and vibration of the bridge caused by wind power.

Dynamic Response of Electromagnetic Rail Launcher Due to Projectile Motion

The dynamic response in the dynamic launching process of electromagnetic rail launcher (EMRL) is very important for the design of launchers and armatures. With the Bernoulli–Euler beam located on an elastic support as an object of the study, the analytical model of EMRL dynamic characteristics under the influence of EM repulsive force and contact force between the armature and the rail is obtained, and the corresponding 3-D finite-element simulation model [moving load–rail model (MR model)] is established. On this basis, the 3-D finite-element simulation model [projectile–rail model (PR model)] considering the projection vibration is established to obtain the dynamic response of EMRL due to projectile vibration. Studies show that the calculation results of the analytical model agree well with that of the MR model. When the moving load works at a critical speed and reaches the point of action, the rail will have an increased deformation and then a harmonic vibration, whose amplitude is five or six times than that under the noncritical operating condition. The analysis of the impact of projectile vibration on the rail deformation makes it known that the vibration amplitude of the PR model is four or five times than that of the MR model because of projectile vibration. The greater the gap between the rail and the armature is, the more violent is the projectile vibration and the greater is the vertical deformation of the rail, and the greater the density of the payload with the same volume is, the more intense is the projectile vibration and the greater is the vertical deformation of the rail. When launching reaches the critical speed, the rail deformation of the PR model is less than that of the MR model, which is mainly caused by the vibration of the projectile, but the vibration periods of those two models are the same.

Passenger Car Active Suspension System Model for Better Dynamic Characteristics

The technological investigations to a light passenger car have been carried out in order to improve the comfort and safety features by the implementation of an active suspension system. A fuzzy logic control-based active suspension system is proposed for the fuel-efficient small passenger cars to fulfil the design upgradation requirements. The proposed design comprised of hydraulically powered actuators is installed at each of the car wheels between sprung and unsprung mass to compensate the ground forces in order to resolve the instability and comfort issues. The dynamic analysis figures out the significant improvement of 12% in comfort and 11.53% in the car stability.

Design of scaled model for dynamic characteristics of stiffened cylindrical shells based on equivalent similar method

ABSTRACTScaled model test is an effective means to verify the design of a stiffened cylindrical shell. However, there is a problem of similarity distortion by use of the traditional dimensional analysis to design scaled models. In this present study, an equivalent similar method is proposed to solve the problem. The method is applied to an axial stiffened cylindrical shell, and the equivalent criteria and scaling laws satisfying the equivalent similarity of global bending mode are derived and verified by numerical examples. The results indicate that the similarity distortion caused by practical conditions for the stiffened cylindrical shell can be solved and the parameters of scaled model can be designed more freely with the proposed equivalent similar method.

Constitutive model of frozen-soil dynamic characteristics under impact loading

To reveal the dynamic mechanical behavior of frozen soil under impact loading, nine groups of frozen-soil samples (the initial moisture content was 20%) under different experimental conditions are tested using the split Hopkinson pressure bar. In this study, a constitutive model for predicting the dynamic strength and compression deformation of frozen soil subjected to impact loading is developed. The model is derived from continuous fracture mechanics, and we assume that frozen soil is a continuous medium with preexisting microcracks. According to the modified Drucker–Prager criterion, a dynamic constitutive model coupled with the plastic and damage phase is established to describe the dynamic mechanical behavior of frozen soil before the peak stress. Considering the post-peak curve, the statistical significance of the uniform stress–strain relationship is not established; therefore, a cohesive crack model is used to model the frozen-soil softening process. Using a comparison, we find that the results of the experiment agree well with the calculated results; thus, the feasibility of the model is proven.

尺蠖型超磁致伸缩旋转驱动器的静动态特性建模与实验

尺蠖型超磁致伸缩旋转驱动器的静动态特性建模与实验

On modeling on a single-winding forced valve electromagnet in a circuit with a ballast resistor

We have built a mathematical model of starting up a forced U-shaped valve electromagnet of static voltage taking into account dynamic parameters and characteristics. The offered model takes into account the influence of eddy currents in the closed circuits of the magnetic system. At the first stage we have developed a mathematical model that allows to determine optimum dimensions, to minimize the mass of active materials (the total mass of copper for windings and ferromagnetic steel), that are used in construction of the electromagnet. Then, based on a known method of integration of the dynamic equations we have obtained an actuation model of the valve magnet taking onto account equivalent resistances of cores of both circular and rectangular cross-sections. Modeling of dynamic parameters and characteristics was done taking into account secondary con-tours without increasing order of differential equations. We list calculated values of dynamic parameters and characteristics of the electromagnet in a circuit with a balance resistor.

Research on modeling and identification of machine tool joint dynamic characteristics

Research on modeling and identification of machine tool joint dynamic characteristics

Issues of gas dynamic characteristics modeling: a study on a centrifugal compressor model stage

The paper presents the results of CFD-calculations of a centrifugal compressor stage with a high-pressure 3D impeller and a vaneless diffuser. The stage was designed by Prof. A. M. Simonov in the Problem Laboratory of Compressor LPI according to the following design parameters: flow rate coefficient 0.080, loading factor 0.74, and the relative Mach number 0.78. Two design grids were used: 2.4 and 4.4 million cells for the sector with one blade. The entire stage was calculated with a sparser grid. Special “Stage” interface conditions are used to interface the gas-dynamic parameters at the boundary regions. The SST turbulence model was used in the calculations. The results of efficiency characteristics and work coefficient comparison showed the following: in design flow rate all three variants of the calculation overstate the loading factor by 14.3%; the calculated characteristics of polytrophic work coefficient in the staging of 360 degrees are closest to the experimental characteristics, but the absolute value is greater than 12% at a flow rate coefficient of 0.085; the maximum calculated efficiency of a stage (the circle of 360 degrees) is almost equal to the measured maximum efficiency.

The Identification of Road Subsidence Zone from Stochastic Modelling of Dynamic Characteristics of a Moving Vehicle

PURPOSES: This paper develops a new stochastic approach to analyze the pavement-vehicle interaction model with a certain roughness and elasticity for the pavement foundation, thereby accommodating the deflection of the pavement, and to identify the road subsidence zone represented with a sudden changes in the elasticity of the foundation. METHODS: In the proposed model, a quarter-car model was combined with a filtered white noise model of road roughness and a two-layer foundation (Euler-Bernoulli beam for the top surface and Winkler foundation to represent the sub-structure soil). An augmented state-space model for the subsystems was formulated. Then, because the input is White noise and the system is represented as a single system, the Lyapunov equation governing the covariance of the system’s response was solved to obtain a structurally weak zone index (WZI). RESULTS: The results showed that the WZI from the pavement-vehicle interaction model is sensitive enough to identify road subsidence. In particular, the WZI rapidly changed with a small change in foundation elasticity, indicating that the model has the potential to detect road subsidence in the early stage. CONCLUSIONS: Beacause of the simplicity of the calculation, the proposed approach has potential applications in managing road conditions while a vehicle travels along the road and detecting road subsidence using a device with an on-board computational capability, such as a smart phone.

Modeling and experimentation of dynamic material removal characteristics in dual-axis wheel polishing

CCOS (computer-controlled optical surfacing) approach is widely used in different optical polishing processes for making ultra-precision components with high surface form accuracy requirements. Under the polishing mode using complex tool motions, middle-spatial-frequency errors (MSF, i.e., residual ripples) tend to be generated on the workpiece surface, which would deteriorate the functional performance of the parts. In this paper, a dynamical removal model (DRM) based on the spatial kinematic analysis and polishing material removal theory is proposed, to investigate the actual material removal characteristics in dual-axis wheel polishing (DAWP). The model is developed to calculate the overall material removal profile (low-spatial-frequency error, LSF) and the middle-spatial-frequency errors, simultaneously. The shape and the stability of the tool influence function (TIF) are firstly investigated. A series of straight line path polishing tests on BK7 glass are carried out to investigate the effects of process parameters on the generated MSF errors and also check the validity of the proposed DRM. Uniform polishing tests on 50 × 50 mm BK7 samples are conducted, under different polishing parameters, the power spectral density (PSD) characteristics of the surface are also analyzed. The results show that the proposed model can effectively predict the material removal profile and especially the ripple characteristics generated on the surface, which are not reflected when using the conventional convolution algorithm typically used in a CCOS process. When increasing the ratio of feed velocity to co-rotating speed, the wavelength and amplitude of the residual ripples increase, and the ratio of ripple amplitude to total material removal depth also increases. The level of residual ripples can be effectively restrained by the appropriate setting of the speed ratio (reducing the feed velocity or increasing the co-rotating speed).

Simulation modeling of dynamic characteristics of machining in NI LabView software environment to improve processing technique of a rod component

The paper considers a problem of providing required surface roughness of rod component during processing by means of forecasting dynamic characteristic of machine works with computer modeling taking into account transitional process. The role of the transitional process is performed by a modified structure in the surface layer of the blank created by preliminary laser effects; it is introduced into the computational model by means of a switch. To analyze the influence of preemptive structural change in the processed material onto the dynamic characteristic, a two-loop computational model describing delays in cutting force changes has been adopted. From the results of computational modeling in NI LabVIEW 2013 software environment, it has been discovered, that during the processing a stable suppression of arising self-vibration takes place when going through the modified structure zone. A positive effect in suppression of self-vibration is also supported with experimental research, thus providing a method of attaining preplanned surface roughness and allowing to remove the finishing operation from the current process to improve productivity and extend the modes of mechanical working. The article was prepared according to the State task (the project’s number № 9.10520.2018/11.12)

Numerical Modeling of the Seasonal Dynamic Characteristics of the Koxkar Glacier, in West Tianshan, China

Glaciers have very different dynamic characteristics during the ablation and accumulation seasons. A dynamic model to study the flow of the Koxkar Glacier is used. Ice velocity, ice viscosity, and the stress variation at different depths were studied. The aim was to compare the change in the glacier’s physical characteristics with changes in air temperature, analyze the movement mechanism at different temperatures in different seasons, and identify why temperature is the main driving force of glacier movement and change. The results show that the surface stresses have similar trends in different seasons, and that the stress in winter is larger than that in summer. This causes the ice body to break and promotes crack formation. Ice viscosity has an obvious seasonal variation, and this is especially noticeable for near-surface ice viscosity. The stress at the bottom did not change much at different temperatures. This indicates that the stress at the bottom is mainly affected by glacier morphology, hydrological characteristics, and geothermal flow.

Analysis of Various Approaches to Modeling of Dynamics of Lifting-Transport Vehicles

The results of analytical and numerical modeling of dynamic characteristics of linear and non-linear mathematical models of the “trolley-load” system of bridge and container cranes are presented. KiDyM software complex is used for numerical modeling, which, based on the use of the apparatus of structural matrices and the built-in computer algebra system, allows the construction of ordinary differential equations of motion of the class of systems under consideration at the analytical level. Recommendations on the possible use of the considered mathematical models of the “trolley-load” system in various regular and forced operation modes of bridge and container cranes are given on the basis of the analysis. The ratio of the results of calculations for various design models of regular and forced operation of the bridge crane has been established. The magnitude of the distribution of the maximum values of the dynamic characteristics of motion of the container crane has been designed by calculating the forced operation mode using various mathematical models.

Dynamic characteristics of tailings reservoir under seismic load

Earthquake is one of the most important factors that leads to the liquefaction of tailings and to the instability of the tailings reservoir. Therefore, it is of great practical significance to study the instability mechanism of the tailings reservoir under seismic load. In this study, the dynamic characteristics of the tailings reservoir under seismic load were investigated by carrying out a model test on the dynamic characteristics of the tailings dam. A model test of tailings dam failure and the dynamic characteristics model of the tailings reservoir under seismic load were established. Additionally, the dynamic characteristics under a seismic load were investigated. Additionally, the correctness of the dynamic characteristics model of the tailings reservoir was verified by numerical calculation. Researches show that with the increase in input peak acceleration, pore water pressure, earth pressure, and the horizontal and vertical displacements of the dam monitoring points are gradually increased. However, the acceleration amplification factor shows a declining trend. In the process of increasing the input peak acceleration, the saturation line and the lifting speed increases gradually. There is no obvious slip surface in the failure of the tailings dam, and the overall sliding is shown by the failure mode. The tailings reach each of the downstream sections. The mud height increases to the peak value, and then decreases gradually until stagnation. The results of this study can provide the theoretical basis and reference values for the stability analysis of a tailings reservoir under a seismic load, and the results are of great significance for controlling the risk factors in the operation of tailings reservoir, reducing the risk of tailings production safety, preventing the occurrence of tailing pond accidents, protecting the property safety of the downstream residents and enterprises, maintaining social stability around the reservoir area and creating a good ecological environment.

Mechanics modeling of dynamic characteristics of laminated thermoelectric cylindrical shells

Thermoelectric cylindrical shells have been widely used to convert waste heat of exhaust pipe into electric energy. They can also be used in refrigerating process to reduce the surface temperature in thermal protection system in modern supersonic space shuttles. This paper presents a transient model to investigate the dynamic characteristics of laminated thermoelectric cylindrical shells. The internal and external surfaces of the shell are assumed to be stress free. Analytical solutions of temperature, electric potential and thermal stress fields are obtained and are presented graphically. The effects of applied electric current density on the temperature, electric potential and thermal stress distributions are investigated. Numerical results show that the transient-state hoop stress at the internal surface of shell is higher than that of steady state. In addition, the power generation efficiency of thermoelectric shell is improved at a specific external applied electric current density. The models we constructed can evaluate the thermal and mechanical performances of materials subjected to temperatures higher than 1400 K therefore can be applied to many severe heating environments.