期刊文献+
共找到200篇文章
< 1 2 10 >
每页显示 20 50 100
Natural vibration and critical velocity of translating Timoshenko beam with non-homogeneous boundaries
1
作者 Yanan LI Jieyu DING +1 位作者 Hu DING Liqun CHEN 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2024年第9期1523-1538,共16页
In most practical engineering applications,the translating belt wraps around two fixed wheels.The boundary conditions of the dynamic model are typically specified as simply supported or fixed boundaries.In this paper,... In most practical engineering applications,the translating belt wraps around two fixed wheels.The boundary conditions of the dynamic model are typically specified as simply supported or fixed boundaries.In this paper,non-homogeneous boundaries are introduced by the support wheels.Utilizing the translating belt as the mechanical prototype,the vibration characteristics of translating Timoshenko beam models with nonhomogeneous boundaries are investigated for the first time.The governing equations of Timoshenko beam are deduced by employing the generalized Hamilton's principle.The effects of parameters such as the radius of wheel and the length of belt on vibration characteristics including the equilibrium deformations,critical velocities,natural frequencies,and modes,are numerically calculated and analyzed.The numerical results indicate that the beam experiences deformation characterized by varying curvatures near the wheels.The radii of the wheels play a pivotal role in determining the change in trend of the relative difference between two beam models.Comparing the results unearths that the relative difference in equilibrium deformations between the two beam models is more pronounced with smaller-sized wheels.When the two wheels are of equal size,the critical velocities of both beam models reach their respective minima.In addition,the relative difference in natural frequencies between the two beam models exhibits nonlinear variation and can easily exceed 50%.Furthermore,as the axial velocities increase,the impact of non-homogeneous boundaries on modal shape of translating beam becomes more significant.Although dealing with non-homogeneous boundaries is challenging,beam models with non-homogeneous boundaries are more sensitive to parameters,and the differences between the two types of beams undergo some interesting variations under the influence of non-homogeneous boundaries. 展开更多
关键词 translating beam Timoshenko beam non-homogeneous boundary natural frequency critical velocity
下载PDF
Research on Automatic Test System of Engine Blade Natural Frequency
2
作者 LU Yonghua LIU Jingjing +2 位作者 YANG Haibo HUANG Chuan MA Zhicheng 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2024年第4期476-487,共12页
Blades are one of the important components on aircraft engines.If they break due to vibration failure,the normal operation of the entire engine will be offected.Therefore,it is necessary to measure their natural frequ... Blades are one of the important components on aircraft engines.If they break due to vibration failure,the normal operation of the entire engine will be offected.Therefore,it is necessary to measure their natural frequency before installing them on the engine to avoid resonance.At present,most blade vibration testing systems require manual operation by operators,which has high requirements for operators and the testing process is also very cumbersome.Therefore,the testing efficiency is low and cannot meet the needs of efficient testing.To solve the current problems of low testing efficiency and high operational requirements,a high-precision and high-efficiency automatic test system is designed.The testing accuracy of this system can reach ±1%,and the testing efficiency is improved by 37% compared to manual testing.Firstly,the influence of compression force and vibration exciter position on natural frequency test is analyzed by amplitude-frequency curve,so as to calibrate servo cylinder and fourdimensional motion platform.Secondly,the sine wave signal is used as the excitation to sweep the blade linearly,and the natural frequency is determined by the amplitude peak in the frequency domain.Finally,the accuracy experiment and efficiency experiment are carried out on the developed test system,whose results verify its high efficiency and high precision. 展开更多
关键词 BLADE vibration failure natural frequency automatic test system
下载PDF
Numerical Approach to Simulate the Effect of Corrosion Damage on the Natural Frequency of Reinforced Concrete Structures
3
作者 Amthal Hakim Wael Slika +1 位作者 Rawan Machmouchi Adel Elkordi 《Structural Durability & Health Monitoring》 EI 2023年第3期175-194,共20页
Corrosion of reinforcing steel in concrete elements causes minor to major damage in different aspects.It may lead to spalling of concrete cover,reduction of section’s capacity and can alter the dynamic properties.For... Corrosion of reinforcing steel in concrete elements causes minor to major damage in different aspects.It may lead to spalling of concrete cover,reduction of section’s capacity and can alter the dynamic properties.For the dynamic properties,natural frequency is to be a reliable indicator of structural integrity that can be utilized in non-destructive corrosion assessment.Although the correlation between natural frequency and corrosion damage has been reflected in different experimental programs,few attempts have been made to investigate this relationship in forward modeling and/or structural health monitoring techniques.This can be attributed to the limited available data,the complex nature of corrosion,and the involvement of multidisciplinaryfields.Therefore,this study presents a numerical attempt to simulate the effect of corrosion damage on the natural frequency of the structure.The approach relies on simulating the time history response of the structure using a modified Bouc-Wen model that incorporates the nonlinear effects of corrosion.Then,modal analysis is utilized to assess the change in dynamic properties in the frequency domain.Tofinish up,regression algorithms are employed tofind optimal relationship between involved parameters,including corrosion damage as input,and natural frequency as output.The efficiency of the suggested framework is illustrated in thirteen buildings with cantilevered column lateral force-resisting system and different levels of corrosion. 展开更多
关键词 CORROSION concrete damage dynamic properties natural frequency nonlinear analysis modal analysis machine learning
下载PDF
Calculation,Simulation,and Testing for the Natural Frequency of a Micro Accelerometer 被引量:2
4
作者 熊继军 范波 +1 位作者 郭虎岗 高建飞 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2008年第9期1715-1722,共8页
A calculation and test method for the natural frequency of a high-g micro accelerometer with complex structures is presented. A universal formula for natural frequency, which can significantly simplify the structural ... A calculation and test method for the natural frequency of a high-g micro accelerometer with complex structures is presented. A universal formula for natural frequency, which can significantly simplify the structural design process, is deduced and confirmed by experiment. A simplified analytical model is established to describe the accelerometer's mechanical behavior and deduce the formula for the natural frequency. Finite element modeling is also conducted to evaluate the natural frequency of the micro-accelerometer and verify the formula. The results obtained from the analytical model and the finite element simulation show good agreement. Finally, a shock comparison method designed for acquiring the high frequency characteristics of the accelerometer is introduced to verify the formula by testing its actual natural frequency. 展开更多
关键词 natural frequency micro accelerometer Rayleigh-Ritz formula
下载PDF
A New Method for Calculation of Natural Frequency of Suspended Pipeline 被引量:1
5
作者 鲁晓光 唐友刚 郑治国 《Transactions of Tianjin University》 EI CAS 2002年第4期282-284,共3页
The buried pipelines are widely used in oil transportation. The pipelines become suspended in the river with flushing of floodwater. If the frequency of vortex shedding is near to the nature frequency of pipelines, it... The buried pipelines are widely used in oil transportation. The pipelines become suspended in the river with flushing of floodwater. If the frequency of vortex shedding is near to the nature frequency of pipelines, it will cause resonance of the suspended pipeline and result in the damage of pipelines. In this paper, the buried parts of pipeline in soil are treated as the half unlimited long beam placed on the elastic foundations. The vibration partial differential equations of suspended pipe and the parts buried in soil are derived respectively. The iterative calculation method is then presented. The results obtained from the suggested method are proved to be identical with the measured values. 展开更多
关键词 suspended pipeline half unlimited long beam natural frequency
下载PDF
Dynamic Characteristics of Functionally Graded Timoshenko Beams by Improved Differential Quadrature Method
6
作者 Xiaojun Huang Liaojun Zhang +1 位作者 Hanbo Cui Gaoxing Hu 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第8期1647-1668,共22页
This study proposes an effective method to enhance the accuracy of the Differential Quadrature Method(DQM)for calculating the dynamic characteristics of functionally graded beams by improving the form of discrete node... This study proposes an effective method to enhance the accuracy of the Differential Quadrature Method(DQM)for calculating the dynamic characteristics of functionally graded beams by improving the form of discrete node distribution.Firstly,based on the first-order shear deformation theory,the governing equation of free vibration of a functionally graded beam is transformed into the eigenvalue problem of ordinary differential equations with respect to beam axial displacement,transverse displacement,and cross-sectional rotation angle by considering the effects of shear deformation and rotational inertia of the beam cross-section.Then,ignoring the shear deformation of the beam section and only considering the effect of the rotational inertia of the section,the governing equation of the beam is transformed into the eigenvalue problem of ordinary differential equations with respect to beam transverse displacement.Based on the differential quadrature method theory,the eigenvalue problem of ordinary differential equations is transformed into the eigenvalue problem of standard generalized algebraic equations.Finally,the first several natural frequencies of the beam can be calculated.The feasibility and accuracy of the improved DQM are verified using the finite element method(FEM)and combined with the results of relevant literature. 展开更多
关键词 Timoshenko beams functionally graded materials dynamic characteristics natural frequency improved differential quadrature method
下载PDF
Influence of Trailing-Edge Wear on the Vibrational Behavior of Wind Turbine Blades
7
作者 Yuanjun Dai Xin Wei +2 位作者 Baohua Li Cong Wang Kunju Shi 《Fluid Dynamics & Materials Processing》 EI 2024年第2期337-348,共12页
To study the impact of the trailing-edge wear on the vibrational behavior of wind-turbine blades,unworn blades and trailing-edge worn blades have been assessed through relevant modal tests.According to these experimen... To study the impact of the trailing-edge wear on the vibrational behavior of wind-turbine blades,unworn blades and trailing-edge worn blades have been assessed through relevant modal tests.According to these experiments,the natural frequencies of trailing-edge worn blades-1,-2,and-3 increase the most in the second to fourth order,thefifth order increases in the middle,and thefirst order increases the least.The damping ratio data indi-cate that,in general,thefirstfive-order damping ratios of trailing-edge worn blades-1 and trailing-edge worn blades-2 are reduced,and thefirstfive-order damping ratios of trailing-edge worn blades-3 are slightly improved.The mode shape diagram shows that the trailing-edge worn blades-1 and-2 have a large swing in the tip and the blade,whereas the second-and third-order vibration shapes of the trailing edge-worn blade-3 tend to be improved.Overall,all these results reveal that the blade’s mass and the wear area are the main fac-tors affecting the vibration characteristics of wind turbine blades. 展开更多
关键词 Wind turbine modal test natural frequency damping ratio mode shape
下载PDF
A NEW METHOD FOR FINDING THE NATURAL FREQUENCY SET OF A LINEAR TIME-INVARIANT NETWORK
8
作者 吴雪 孙雨耕 《Transactions of Tianjin University》 EI CAS 1997年第2期28-35,共8页
This paper presents a new method for finding the natural frequency set of a linear time invariant network. In the paper deriving and proving of a common equation are described. It is for the first time that in the co... This paper presents a new method for finding the natural frequency set of a linear time invariant network. In the paper deriving and proving of a common equation are described. It is for the first time that in the common equation the natural frequencies of an n th order network are correlated with the n port parameters. The equation is simple and dual in form and clear in its physical meaning. The procedure of finding the solution is simplified and standardized, and it will not cause the loss of roots. The common equation would find wide use and be systematized. 展开更多
关键词 n th order linear time invariant networks natural frequencies n ports
下载PDF
Effect of vehicle weight on natural frequencies of bridges measured from traffic-induced vibration 被引量:16
9
作者 Chul-Young Kim Dae-Sung Jung +2 位作者 Nam-Sik Kim Soon-Duck Kwon Maria Q.Feng 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2003年第1期109-116,共8页
Recently,ambient vibration test(AVT)is widely used tu estimate dynamic characteristics of large civil struc- tures.Dynamic characteristics ean be affected by various envirnnmental factors such as humidity,intensity of... Recently,ambient vibration test(AVT)is widely used tu estimate dynamic characteristics of large civil struc- tures.Dynamic characteristics ean be affected by various envirnnmental factors such as humidity,intensity of wind,and temperature.Besides these environmental conditions,tire mass of vehicles may change the measured valnes when traffic-in- duced vibration is used as a source of AVT tor bridges.The effect of vehicle mass on dynamic characteristics is investigated through traffic-induced vibration tests on three bridges;(1)three-span suspension bridge(128m+404m+128m),(2) five-span continuous steel box girder bridge(59m+3@ 95m+59m),(3)simply supported plate girder bridge(46m). Acceleration histories of each measurement location under normal traffic are recorded for 30 minutes at field.These recor- ded histories are divided into individual vibrations and are combined into two groups aceording to the level of vibration;one by heavy vehicles such as trucks and buses and the other by light vehicles such as passenger cars.Separate processing of the two groups of signals shows that,for the middle and long-span bridges,the difference can be hardly detected,but,for the short span bridges whose mass is relatively small,the measured natural frequencies can change up to 5.4%. 展开更多
关键词 ambient vibration test traffic induced vibration vehicle mass suspension bridge short-span bridge dynamic characteristics natural frequency
下载PDF
Investigation of Microstructure, Natural Frequencies and Vibration Modes of Dragonfly Wing 被引量:13
10
作者 H. Rajabi M. Moghadami A. Darvizeh 《Journal of Bionic Engineering》 SCIE EI CSCD 2011年第2期165-173,共9页
In the present work, a thorough investigation on the microstructural and morphological aspects of dragonfly wings was carried out using scanning electron microscope. Then, based on this study and the previous reports,... In the present work, a thorough investigation on the microstructural and morphological aspects of dragonfly wings was carried out using scanning electron microscope. Then, based on this study and the previous reports, a precise three-dimensional numerical model was developed and natural frequencies and vibration modes of dragonfly forewing were determined by finite element method. The results shown that dragonfly wings are made of a series of adaptive materials, which form a very complex composite structure. This bio-composite fabrication has some unique features and potential benefits. Furthermore, the numerical results show that the first natural frequency of dragonfly wings is about 168 Hz and bending is the predominant deformation mode in this stage. The accuracy of the present analysis is verified by comparison of calculated results with experimental data. This paper may be helpful for micro aerial vehicle design concerning dynamic response. 展开更多
关键词 insect wing natural frequency vibration mode SEM finite element method
下载PDF
Theoretical analysis of natural frequency of externally prestressed concrete beam based on rigidity correction 被引量:3
11
作者 Hui-xia Xiong1,2, Yao-ting Zhang11.School of Civil Engineering & Mechanics, Huazhong University of Science and Technology, Wuhan 430074, China 2.Department of Civil Engineering, Nanyang Institute of Technology, Nanyang 473004, China. 《Journal of Pharmaceutical Analysis》 SCIE CAS 2009年第1期31-35,共5页
A dynamic test on externally prestressed simply supported concrete beams separately with three typical types of tendon distributions was conducted. The results show that the natural frequencies of the beams increase w... A dynamic test on externally prestressed simply supported concrete beams separately with three typical types of tendon distributions was conducted. The results show that the natural frequencies of the beams increase with the increase in the prestressing force at the tensioning stage, and the natural frequencies decrease after the cracks occur in the beams. Following the calculation formula of natural frequency of externally prestressed beam, which was reported in a literature, the natural frequencies of the experimental beams are calculated, and big errors are found between the test results and the calculated ones of natural frequency values. As a result, this paper has tried to adopt two methods to correct the rigidity parameter of the concrete beam in the formula for natural frequency calculation, and to use the corrected formula to calculate the frequencies of the experimental beams. The calculation results indicate a good consistency with the experimental ones, which verifies the feasibility of the corrected formula. 展开更多
关键词 externally prestressed concrete beam natural frequency rigidity correction regression analysis
下载PDF
Assessment of natural frequency of installed offshore wind turbines using nonlinear finite element model considering soil-monopile interaction 被引量:3
12
作者 Djillali Amar Bouzid Subhamoy Bhattacharya Lalahoum Otsmane 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2018年第2期333-346,共14页
A nonlinear finite element model is developed to examine the lateral behaviors of monopiles, which support offshore wind turbines(OWTs) chosen from five different offshore wind farms in Europe. The simulation is using... A nonlinear finite element model is developed to examine the lateral behaviors of monopiles, which support offshore wind turbines(OWTs) chosen from five different offshore wind farms in Europe. The simulation is using this model to accurately estimate the natural frequency of these slender structures, as a function of the interaction of the foundations with the subsoil. After a brief introduction to the wind power energy as a reliable alternative in comparison to fossil fuel, the paper focuses on concept of natural frequency as a primary indicator in designing the foundations of OWTs. Then the range of natural frequencies is provided for a safe design purpose. Next, an analytical expression of an OWT natural frequency is presented as a function of soil-monopile interaction through monopile head springs characterized by lateral stiffness KL, rotational stiffness KRand cross-coupling stiffness KLRof which the differences are discussed. The nonlinear pseudo three-dimensional finite element vertical slices model has been used to analyze the lateral behaviors of monopiles supporting the OWTs of different wind farm sites considered. Through the monopiles head movements(displacements and rotations), the values of KL, KRand KLRwere obtained and substituted in the analytical expression of natural frequency for comparison. The comparison results between computed and measured natural frequencies showed an excellent agreement for most cases. This confirms the convenience of the finite element model used for the accurate estimation of the monopile head stiffness. 展开更多
关键词 Nonlinear finite element analysis Vertical slices model Monopiles under horizontal loading natural frequency Monopile head stiffness Offshore wind turbines(OWTs)
下载PDF
ZERO MODE NATURAL FREQUENCY AND NONLINEAR VIBRATION OF COUPLED LATERAL AND TORSION OF A LARGE TURBINE GENERATOR 被引量:2
13
作者 TaNa QiuJiajun CaiGanhua 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2005年第2期302-306,共5页
Zero mode natural frequency (ZMNF) is found during experiments. The ZMNF andvibrations resulted by it are studied. First, calculating method of the ZMNF excited byelectromagnetic in vibrational system of coupled mecha... Zero mode natural frequency (ZMNF) is found during experiments. The ZMNF andvibrations resulted by it are studied. First, calculating method of the ZMNF excited byelectromagnetic in vibrational system of coupled mechanics and electrics are given from the view ofmagnetic energy. Laws that the ZMNF varies with active power and exciting current are obtained andare verified by experiments. Then, coupled lateral and torsional vibration of rotor shaft system isstudied by considering rest eccentricity, rotating eccentricity and swing eccentricity. UsingLargrange-Maxwell equation when three phases are asymmetric derives differential equation of thecoupled vibration. With energy method of nonlinear vibration, amplitude-frequency characteristics ofresonance are studied when rotating speed of rotor equals to ZMNF. The results show that ZMNF willoccur in turbine generators by the action of electromagnetic. Because ZMNF varies withelectromagnetic parameters, resonance can occur when exciting frequency of the rotor speed is fixedwhereas exciting current change. And also find that a generator is in the state of large amplitudein rated exciting current. 展开更多
关键词 Zero mode natural frequency Coupled vibration of lateral and torsionEccentricity Rotor shaft Hydro turbine generator
下载PDF
Natural frequencies analysis of a composite beam consisting of Euler-Bernoulli and Timoshenko beam segments alternately 被引量:2
14
作者 PENG Li-ping 《Journal of Central South University》 SCIE EI CAS CSCD 2017年第3期625-636,共12页
Present investigation is concerned with the free vibration property of a beam with periodically variable cross-sections.For the special geometry characteristic,the beam was modelled as the combination of long equal-le... Present investigation is concerned with the free vibration property of a beam with periodically variable cross-sections.For the special geometry characteristic,the beam was modelled as the combination of long equal-length uniform Euler-Bernoulli beam segments and short equal-length uniform Timoshenko beam segments alternately.By using continuity conditions,the hybrid beam unit(ETE-B) consisting of Euler-Bernoulli beam,Timoshenko beam and Euler-Bernoulli beam in sequence was developed.Classical boundary conditions of pinned-pinned,clamped-clamped and clamped-free were considered to obtain the natural frequencies.Numerical examples of the equal-length composite beam with 1,2 and 3 ETE-B units were presented and compared with the equal-length and equal-cross-section Euler-Bernoulli beam,respectively.The work demonstrates that natural frequencies of the composite beam are larger than those of the Euler-Bernoulli beam,which in practice,is the interpretation that the inner-welded plate can strengthen a hollow beam.In this work,comparisons with the finite element calculation were presented to validate the ETE-B model. 展开更多
关键词 natural frequency Euler-bernoulli beam Timoshenko beam hybrid beam unit composite beam
下载PDF
NATURAL FREQUENCY OF COMPONENT UNDER INFLUENCE OF WELDING RESIDUAL STRESS 被引量:2
15
作者 Gao Yongyi Lin Lichuan 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 1996年第1期135-140,共6页
According to the distribution feature of welding residual stress on plate with welding seam along axis,a mathematical model of the welding residual stress is established.A formula of natural frequency of four boundary... According to the distribution feature of welding residual stress on plate with welding seam along axis,a mathematical model of the welding residual stress is established.A formula of natural frequency of four boundary simply-supported quadrate thin plate with welding residual stress is developed.Some conclusions have been obtained.They are:(1)if there is welding residual stress,all natural frequencies of component are in increase,(2)change of high rank natural frequency under the influence of residual stress is larger than that of low rank natural frequency,and the higher the rank number is the larger the absolute amount of change of natural frequency is. 展开更多
关键词 mathematical model residual stress natural frequency WELDING quadrate thin plate
下载PDF
Determination of the natural frequencies of axially moving beams by the method of multiple scales 被引量:3
16
作者 杨晓东 陈立群 《Journal of Shanghai University(English Edition)》 CAS 2007年第3期251-254,共4页
The natural frequencies of an axially moving beam were determined by using the method of multiple scales. The method of second-order multiple scales could be directly applied to the governing equation if the axial mot... The natural frequencies of an axially moving beam were determined by using the method of multiple scales. The method of second-order multiple scales could be directly applied to the governing equation if the axial motion of the beam is assumed to be small. It can be concluded that the natural frequencies affected by the axial motion are proportional to the square of the velocity of the axially moving beam. The results obtained by the perturbation method were compared with those given with a numerical method and the comparison shows the correctness of the multiple-scale method if the velocity is rather small. 展开更多
关键词 the method of multiple scales natural frequency axially moving beam
下载PDF
NATURAL FREQUENCY FOR RECTANGULAR ORTHOTROPIC CORRUGATED-CORE SANDWICH PLATES WITH ALL EDGES SIMPLY-SUPPORTED 被引量:1
17
作者 WU Hui(吴晖) +1 位作者 YU Huan-ran(俞焕然) 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2001年第9期1019-1027,共9页
A simple approach to reduce the governing equations for orthotropic corrugated core sandwich plates to a single equation containing only one displacement function is presented, and the exact solution of the natural fr... A simple approach to reduce the governing equations for orthotropic corrugated core sandwich plates to a single equation containing only one displacement function is presented, and the exact solution of the natural frequencies for rectangular corrugated-core sandwich plates with all edges simply-supported is obtained. Furthermore, two special cases of practical interests are discussed in details. 展开更多
关键词 rectangular sandwich plates corrugated-core ORTHOTROPIC natural frequency displacement functional exact solution
下载PDF
Natural Characteristic of Thin-Wall Pipe under Uniformly Distributed Pressure 被引量:1
18
作者 Chao-Feng Li Qian-Sheng Tang +1 位作者 Hou-Xin She Bang-Chun Wen 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2018年第6期118-127,共10页
Natural characteristics of thin?wall pipe of the compressor under uniformly distributed pressure were presented in this paper based on a cylindrical shell model. In the traditional method, the beam model was usually u... Natural characteristics of thin?wall pipe of the compressor under uniformly distributed pressure were presented in this paper based on a cylindrical shell model. In the traditional method, the beam model was usually used to analyze the pipe system. In actual fact, the pipe segment of the compressor was always broken in the form of a long crack or a partial hole and the phenomenon was hardly explained by beam model. According to the structure characteristic of compressor pipe segment, whose radius is large and thickness is little, shell model shows the advantage in this kind of pipe problem. Based on Sanders’ shell theory, the vibration di erential equation of pipe was established by apply?ing the energy method. The influences of length to radius ratio(L/R), thickness to radius ratio(h/R), circumferential wave number(n) and pressure(q) on the natural frequencies of pipe were analyzed. The study shows: Pressure and structural parameters have a great e ect on the natural characteristics of the pipe. Natural frequency increases as the pressure increases, especially for the higher mode. The sensitivity of natural frequency on pressure becomes stronger with h/R ratio increases; when L/R ratio is greater than a certain critical value, the influence of the pressure on natural frequency will no longer be obvious. The value of n corresponding to the minimum natural frequency also depends on the value of pressure. In the end, analysis of the forced vibration of a specific pipeline model was given and the modal shapes were illustrated to understand the break of the pipe. The research here will provide the theory support for the dynamic design of related pressure pipe and further experiment study should be employed. 展开更多
关键词 Pipe vibration natural frequency Pulse pressures Geometric parameters Modal shape
下载PDF
Assessment of structural damage using natural frequency changes 被引量:4
19
作者 Shu-Qing Wang Hua-Jun Li 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2012年第1期118-127,共10页
The present paper develops a new method for damage localization and severity estimation based on the employment of modal strain energy. This method is able to determine the damage locations and estimate their severiti... The present paper develops a new method for damage localization and severity estimation based on the employment of modal strain energy. This method is able to determine the damage locations and estimate their severities, requiring only the information about the changes of a few lower natural frequencies. First, a damage quantification method is formulated and iterative approach is adopted for determining the damage extent. Then a damage localization algorithm is proposed, in which a damage indicator is formulated where unity value corresponds to the true damage scenario. Finally, numerical studies and model tests are conducted to demonstrate the effectiveness of the developed algorithm. 展开更多
关键词 Damage assessment Damage detection Strain energy - Modal analysis - natural frequency
下载PDF
Gravity Effect on the First Natural Frequency of Offshore Wind Turbine Structures 被引量:1
20
作者 Ma Hongwang Chen Longzhu 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2016年第1期95-101,共7页
The fatigue limit state is critical for most offshore wind turbine.To minimize the development of fatigue damage,dynamic amplification of the response must be avoided.Thus,it is important to ensure that the first natu... The fatigue limit state is critical for most offshore wind turbine.To minimize the development of fatigue damage,dynamic amplification of the response must be avoided.Thus,it is important to ensure that the first natural frequency of the offshore wind turbine does not coincide with the excitation frequencies related to wind turbine and wave loadings.For evaluating the self-gravity influence on the first natural frequency of wind turbine support structures,the offshore wind turbine system vibration is modeled using an Euler-Bernoulli beam with axial force and horizontal force.Real data from five wind turbines available in the market are considered.The sizes of wind turbines vary from 2.3MW to 6MW,and subsequently,the heights of tubular steel towers vary from 83 mto 100m.Results indicate that the average influence of gravity on the first natural frequency is nearly 1.8%.The first natural frequency is considered ranging from 1P(rototor frequency)to 3P(blade passing frequency).The design procedure requires an accurate evaluation of the first natural frequency.From this perspective,the first natural frequency is reduced since gravity needs to be considered for the design of offshore wind turbine support structures,especially when the first natural frequency of the offshore wind turbine is close to the lower limit,rotor frequency1 P. 展开更多
关键词 offshore wind turbine the first natural frequency GRAVITY Euler-Bernoulli beam
下载PDF
上一页 1 2 10 下一页 到第
使用帮助 返回顶部