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In this study, we investigated the natural dynamic characteristics of bi-directional (2D) functionally graded material (FGM) beams using differential quadrature method (DQM). The higher order shear deformation theory was used to reconstruct the displacement and strain fields at any point on the beam. The resulting equilibrium equation of elasticity was expressed by stress is equivalently integrated along the height direction of a rectangular beam, which helps derive the ordinary differential characteristic equations of the free vibration problem of 2D FGM beams, including the natural frequency and the triple-coupled mode functions. Then, using the DQM, the eigenvalue problems of the derived differential equation for free vibration of 2D FGM beams were transformed into a set of algebraic equations representing the eigenvalue problems. The obtained algebraic equations were solved using the orthogonal triangular decomposition method (QR). First, several orders of natural frequencies of the free vibrations of 2D FGM beams were calculated sequentially, and then, the triple-coupled mode functions were obtained together. Numerical examples were used to illustrate the effects of the thickness ratio, grading indexes, and the supported edges on the natural frequency in detail. Numerical results validated the feasibility and accuracy of the developed DQM for solving the problem of free vibrations in 2D FGM beams. [ABSTRACT FROM AUTHOR]

To show dynamic properties of a motorized spindle at high speed, C01 type motorized spindle bearing-rotor system is used as a study object, and the dynamic model of the bearing-rotor system is established. The method to analyze vibration characteristics of motorized spindles by power flow is proposed, and it is found that the vibration energy is not necessarily considerable at the position where the vibration displacement response is significant. Finally, the system vibration energy distribution under different bearing stiffness is analyzed. The power flow method can analyze the dynamic characteristics of the bearing-rotor system in terms of energy distribution. [ABSTRACT FROM AUTHOR]

Abstract The artillery weapon system,characterized as a complex nonlinear mechanical system, is influenced by various factors affecting its muzzle vibration response.In the article, the model of the artillery system with variable cross-section and multistep barrel is established on the basis of the bending deformation equation, and the fundamental frequency equation is obtained, and the auxiliary verification is completed through modal testing and finite element methods. Then, considering the clearance between the barrel and the cradle, the equivalent nonlinear dynamic model of the vertical vibration of the muzzle is established is established. Furthermore, the multi-scale analysis method obtains the amplitude-frequency curve of the equivalent model under sinusoidal excitation, and analyzes the influence of parameters on the response characteristics. Finally, the vibration research system of the model of the artillery system is constructed to study the vibration characteristics of the muzzle. The results show that the equivalent nonlinear dynamic model established in the paper has certain accuracy, which can provide a certain reference for the related research of the artillery system

The artillery weapon system,characterized as a complex nonlinear mechanical system, is influenced by various factors affecting its muzzle vibration response.In the article, the model of the artillery system with variable cross-section and multistep barrel is established on the basis of the bending deformation equation, and the fundamental frequency equation is obtained, and the auxiliary verification is completed through modal testing and finite element methods. Then, considering the clearance between the barrel and the cradle, the equivalent nonlinear dynamic model of the vertical vibration of the muzzle is established is established. Furthermore, the multi-scale analysis method obtains the amplitude-frequency curve of the equivalent model under sinusoidal excitation, and analyzes the influence of parameters on the response characteristics. Finally, the vibration research system of the model of the artillery system is constructed to study the vibration characteristics of the muzzle. The results show that the equivalent nonlinear dynamic model established in the paper has certain accuracy, which can provide a certain reference for the related research of the artillery systemArticle highlights: An model for predicting the equivalent normal stiffness and fundamental frequency of vertical vibration of the muzzle in variable cross-section and multi-step barrel is established on the basis of quadratic integral method and Rayleigh method The impact of clearance and excitation on the response characteristics of the artillery system is examined for providing a reference for the design of the system. The accuracy and universality of the equivalent nonlinear dynamic model of the vertical vibration of the muzzle, considering the clearance, were verified by the vibration experiment. [ABSTRACT FROM AUTHOR]

Aiming at the problem of dynamic characteristic modeling of bolted connection structure considering the influence of roughness,a new model of bolted connection with rough surface joint surface replaced by spring damping model is established,which considers the influence of various factors such as bolt,gasket and rough joint surface on vibration characteristics. The model is based on the fractal theory of mechanical surface,and the calculation formula of the joint stiffness is obtained. Based on the finite element contact results,the spring layout of the spring damping model is determined,and the influence of the number of spring layouts on the vibration characteristics is studied. The experimental results show that the results of this method are very close to the experimental results,which show that this method is effective.

Aiming at the problems of vibration and noise exceeding the standard of a new batch of fans, the AVANT-7008 data acquisition analyzer was used to analyze the vibration time and frequency domain characteristics of the whole machine, outer frame and net cover of the fan under different speed conditions, the key techniques of free suspension modal test of the fan assembly were summarized. A multi-sensor triaxial vibration noise acquisition and analysis test method was proposed. The Modal Genius modal simulation analysis software was used to study the modal characteristics of the fan frame free suspension model, model data driving point was determined according to the actual sensor placement position, the modal characteristics of the free suspension model of the fan frame was studied, natural frequency and main mode of the frame was obtained. The results show that the frequency range that affects the vibration of the fan is between 280 Hz and 300 Hz and the frequency around 23. 13 Hz (when the fan speed is 1 400 r/min) ,the lateral vibration is larger than the longitudinal vibration amplitude, and the vibration structure of the outer frame structure with improved fragile position is significantly reduced in the A, Y and Z directions, which verifies the effectiveness of the designed modal test scheme. [ABSTRACT FROM AUTHOR]

In this study, the CFRP shafts made up of T700-SC multilayered composites have been designed to replace the steel shaft of a ship. An important design variable to be considered when designing composite material intermediate shafts is the natural frequency for resonance avoidance at critical rotational speed and torsional strength for axial load. In order to satisfy these, strength and modal analysis were performed. In order to minimize the deformation of the shape due to the residual stress after mandrel removal, it was laminated by axial symmetry. The fibers orientation angle has a great influence on the natural frequency of the drive shaft. The carbon fiber should be closely oriented at 3 0 ∘ to improve the modulus of elasticity in the direction of length of the intermediate shaft and to increase the natural frequency. Also, the optimum fiber orientation for maximum torsional strength should be close to 4 5 ∘ . The stacking pattern and the stacking order were finally decided considering the results of the finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• The mechanical properties of jujube branches are calculated from the micro end stress. • Through the difference analysis, the relative error between the experimental and model analysis results is analyzed. • The resonance frequency is obtained by frequency sweep test. • The best parameters are obtained through interactive experiments. To explore the vibration energy transmission characteristics of mechanical harvesting of jujube and improve the effectiveness of vibration harvesting, the vibration response characteristics of small and densely planted Jun jujube branches were experimentally studied and evaluated. According to the agronomic requirements of mechanical harvesting of jujube, first, this paper analyzes the vibration harvesting mechanism of jujube, establishes the transverse bending vibration mechanical model of jujube branches, and obtains the sixth-order natural frequency of jujube branches through vibration frequency sweep experiments. Based on the slope scoring principle and response surface method, the impact of different excitation parameters on the jujube branch vibration effect evaluation index P z was characterized through field experiments, and an optimized vibration effect score was obtained. The results showed that the low-order natural frequencies of small and densely planted jujube branches were mainly concentrated in the range of 6 ∼ 22 Hz, and the vibration response was the most intense at 17.5, 18.0 and 22.5 Hz, which was more conducive to vibration harvesting. By optimizing the relationship between the excitation parameters and evaluation index P z , a better jujube branch vibration effect score of P z = 85.63 is obtained, which provides a reference for the design and development of high-efficiency jujube vibration harvesting devices. [ABSTRACT FROM AUTHOR]

In this paper, vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method (FEM) by 8-node acoustic fluid elements. Vibration characteristics of the structure in finite fluid domain are calculated combining structure FEM mass matrix. By writing the relevant programs, numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain. [ABSTRACT FROM AUTHOR]

Studies on novel composite structures that can decrease floor height and improve constructional efficiency in order to increase spatial efficiency and lease revenue have been actively conducted. An innovative fire-proof, lightweight, absorbed, shallow, and hybrid (iFLASH) system was developed to solve construction site issues, such as improving constructability, reducing construction time, and attaining structural efficiency by reducing the weight of the building structure. This system can shorten the construction duration and decrease the floor height and structural weight, owing to features such as a low thickness and light weight. However, studies on the vibration characteristics of this new floor system have not been performed yet. As the general thickness of the iFLASH system ranges from 25 to 30 mm, it must have a sufficient floor vibration performance in order to be utilized. To evaluate the floor vibration performance of the iFLASH system, an experiment was performed in two buildings where the system was applied. This paper presents the results of the dynamic characteristics and serviceability testing as basic data for the vibration characteristics of the iFLASH system. [ABSTRACT FROM AUTHOR]