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    2022,20(6):1-9, DOI: 10.6052/1672-6553-2021-068
    This paper attempts to summarize the traditional engineering fields and emerging engineering fields involved in the vibration problem in engineering, as well as the related research fields and research trends. However, due to the complexity of the vibration problem itself and continuous emergence of emerging engineering fields, this is a big topic, and it may be difficult to summarize accurately and in place in a small space.
    2022,20(6):10-23, DOI: 10.6052/1672-6553-2021-051
    South Xinjiang is an important agricultural production base in China. Due to its unique geographical location,the soil of agricultural land is subjected to soil caking and high salinity,which seriously hinders the normal growth of crops. In order to ensure the sustainable development of agriculture,deep ploughing has become a necessary part of improving the soil environment,and the high speed plough is an important ploughing machine to achieve efficient deep ploughing,but the domestic high speed plough basic design theory lacks integrity,systematization and standardization,This is one of the key factors leading to a gap between the high speed adaptability of domestic high speed ploughs and imported high speed ploughs. High speed ploughs are agricultural implements with an operating speed of over 7km/h. This paper takes the curved surface of high speed ploughs as the object of study,and focuses on the design method of the curved surface of high speed ploughs and the influence of structural parameters on their inherent characteristics. Firstly,based on the horizontal straight element line method,the design method of high speed plough body surface is proposed,and the design of high speed plough body surface is standardised,forming a relatively complete and standardised design method of high speed plough body surface. Secondly,the modal analysis of the specific high speed plough body surface is carried out using finite element software to obtain the natural frequencies and mode shapes of the high speed plough body surface. Finally,the effects of changes in height deviation,guide curve opening,guide curve mounting angle and spar angle on the inherent frequency of the curved surface of the high speed plough are investigated.The results of this paper provide a reference for the design and optimisation of high speed plough structures, and provide an appropriate complement to the basic design theory of high speed ploughs.
    2022,20(6):24-32, DOI: 10.6052/1672-6553-2021-050
    The dynamic problem of the cable with hose of alongside liquid cargo replenishment of ship was analysed, in and the effects of inclination angle of the cable, the position of saddle, the span of the cable were considered. The stress state of the cable and hose at each saddle position were obtained by the principle of statics. Then the dynamic model of the cable and hose of alongside liquid cargo replenishment were simplified to the cable system with multiple lumped masses. The higher order modal truncation of partial differential dynamic model was carried out by the Galerkin method. Moreover the dynamic characteristics of this system were analyzed under typical operating conditions. The results shows that there were complex dynamic characteristics in this system, such as typical period and chaos. The effects of the cable span and damping on the dynamic characteristics of the system were analyzed.
    2022,20(6):33-40, DOI: 10.6052/1672-6553-2021-053
    Based on the bifurcation theory, the levitation stability of maglev vehicle turnout beam coupling system is studied. The magnetic levitation electromagnet model, levitation controller model, vehicle system model and turnout beam model are established, and the vehicle turnout coupling model system is constructed. The dynamic levitation behavior of maglev vehicle on turnout beam is analyzed in detail. Three levitation states,i.e., steady levitation, self excited vibration and levitation sucking, are simulated and reproduced. The bifurcation characteristics of levitation vibration of vehicle turnout coupling system with different levitation control parameters are calculated by using the brute force method. The relationship between the mass and natural frequency of turnout and the stability region of suspension control parameters is studied. The results show that there are upper and lower limits for the stability region of the control parameter kp. As kp is less than the lower limit,there is the low frequency self excited vibration of the vehicle suspension system. As kp is greater than the upper limit is the coupled self excited vibration of the turnout. When the natural frequency of turnout is close to suspension frequency, the upper limit value of stability region of suspension control parameters is the smallest, and the lower limit value of stability region is not affected. By changing the mass of turnout, the levitation stability region can be expanded, and the coupling self excited vibration of turnout can be avoided.
    2022,20(6):41-48, DOI: 10.6052/1672-6553-2021-054
    In order to study the yaw instability of FPSO in regular waves, nonlinear fully coupled 6 DOF motion equations of moored floating body are established and solved numerically. The accuracy of equation is verified by comparing equilibrium yaw angles calculated by numerical simulation with model test. The influence of yaw instability on motion responses is studied. The influences of initial yaw angle and wave steepness on yaw instability and motion responses are also studied. The results show that the FPSO may lose the weathervane effect at particular wavelength to ship length ratio, and this increases the wave loads acting on the hull which arouse greater responses in roll and heave. The wave steepness doesn’t affect the final equilibrium yaw angle. However, it affects the time required to reach equilibrium and the response amplitude. The initial yaw angle affects the final equilibrium position and motion response of the FPSO.
    2022,20(6):49-57, DOI: 10.6052/1672-6553-2021-055
    The precision measurement and control instruments of the test bed will be disturbed by the vibration equipment in the working process, which will affect its normal operation. Therefore, it is necessary to use the vibration isolation device for vibration protection. Taking the double layer vibration isolation device as the research object, a multi mount and multi dimensional flexible dynamic model is established by combining the finite element method and impedance synthesis approach. The effects of different instrument mass, system structure and isolator parameters on the vibration transmission characteristics of the vibration isolation device are analyzed. The results show that the designed double layer vibration isolation device can meet the application requirements. Increasing the thickness of the upper table and reducing the stiffness of the vibration isolator can significantly improve the vibration isolation efficiency.
    2022,20(6):58-63, DOI: 10.6052/1672-6553-2021-056
    With the development of high pressure and high power of aviation hydraulic system, the vibration problem of hydraulic pipeline is increasingly not to be ignored. Reducing the vibration of hydraulic pipeline is of great significance to improve the safety of aircraft during flight. In this paper, the vibration characteristics of aviation hydraulic pipeline under pump source pulse condition are studied, and the mathematical model of vibration characteristics of hydraulic pipeline under the influence of fluid pressure and flow rate is established. The actual hydraulic pipeline system is modeled and fluid structure coupling simulation is carried out by using finite element software ANSYS, and the corresponding vibration response is obtained. The results show that the natural frequency of hydraulic pipeline varies with different fluid velocity and pressure. When the fluid pulsation frequency is close to the natural frequency of the pipeline system, the system will have resonance and the vibration amplitude increases greatly.
    2022,20(6):64-75, DOI: 10.6052/1672-6553-2022-042
    To solve the problems of low positioning accuracy and dependence on high precision IMU of the existing UWB IMU positioning system for wheeled mobile robots, a localization algorithm using error state Kalman filter to integrate UWB IMU Odometer is proposed to improve the position and attitude estimation accuracy of mobile robots using linear velocity measurement of odometry and pseudo measurement implied by the nonholonomic constraints. Meanwhile, for the nonlinear system composed of the multi sensor measurement models, a detailed theoretical analysis and mathematical proof of the observability of the system is carried out by an observability rank condition analysis method based on the Lie derivative, and the conditions under which the system is locally weakly observable are concluded, which determines the required measurement outputs and control inputs for unbiased estimation of the system states. The simulation results show that when the observability conditions are satisfied, the state estimation approach proposed in this paper can effectively obtain the accurate 6 DOF poses of the mobile robot and significantly improve the positioning accuracy compared with the conventional methods.
    2022,20(6):76-84, DOI: 10.6052/1672-6553-2021-081
    The modeling method of forward recursive formulation of flexible multibody systems is used in this paper. Based on the principle of velocity variation, a rigid flexible coupling dynamics model of a spacecraft with Stewart platform, flexible solar panels and CMG components was established. Due to the large degree of freedom of the model, unable to meet the needs of real time control. Therefore, an equivalent simplified model of the Stewart platform with simplified legs was established. Through comparison with the complete model of the flexible Stewart platform spacecraft, the correctness and efficiency of the established dynamic model were verified. The influence of the motion of the main platform and the vibration of the flexible panels board on the dynamic response of the payload is analyzed. It is pointed out that the motion of the main platform cannot be simply fixed or the vibration of the flexible panels cannot be ignored when designing the micro vibration suppression scheme of the Stewart platform. The research in this paper provides effective technical support for micro vibration damping and high precision pointing of spacecraft with Stewart platform.
    2022,20(6):85-93, DOI: 10.6052/1672-6553-2022-006
    In order to meet the requirements of different flight missions, the flexible wings of the folding wing aircrafts can be folded or deployed during the flight. As one of the key aspects of folding wing aircrafts, successful deployment and locking of the folding wings matters. Hence, in this work, the passive deployment dynamics of a hypersonic folding wing is studied. An accurate dynamic model is established and the parameters for deployment is investigated for the purpose of reducing the shock vibrations of the folding wing after deployment. Firstly, a flexible multibody dynamic model of the folding wings is established via the absolute nodal coordinate formulation (ANCF), which can accurately describe the large rotations and large deformations of the folding wings. The piston theory is utilized to derive the aerodynamic forces of the folding wing during deployment. The generalized α algorithm is used to solve the system dynamic equations. Secondly, the influence of the deployment torsion bar, the retarding spring, and the flight attitude on the dynamic response of the folding wing is studied. The system parameters are optimized to effectively reduce the shock vibrations of the folding wing.
    2022,20(6):94-100, DOI: 10.6052/1672-6553-2022-002
    The measurement acceleration of the force balance accelerometer (FBA) is calculated by the control force when the feedback control force is balanced with the external inertia force. Thus, the force balance control algorithm is the core of a force balance sensor. Most of the traditional control algorithms aim at minimizing the offset position of the sensitive elements from the equilibrium, which limits the measurement accuracy and applicable bandwidth of the force balance accelerometer. In this paper, taking a MEMS force balance sensor as the object, an optimal control algorithm of force balance accelerometer is proposed for minimizing the measurement error. By introducing measurement error as a new state variable, the difficult force balance control is transformed into an optimal control problem for response minimization, from which the analytical expression of the optimal control force is obtained. Based on the proposed control strategy, the real time high precision detection of unknown acceleration signal is realized. Numerical simulations are carried out for three different types of input acceleration signals (step, periodic and random). It is found that the proposed algorithm can accurately detect all kinds of input acceleration signals, and the frequency band of the measured signal reaches up to kHz. At the same time, the vibration response of the sensitive element can be effectively controlled, which guarantees the large dynamic range of a FBA. Our work provides the basis for the research of high performance force balance accelerometer with high precision and wide frequency band.
    2022,20(6):101-105, DOI: 10.6052/1672-6553-2022-047
    The axial velocity and the material’s heterogeneity introduce the great challenge on the vibration analysis of the functionally graded beam with an axial velocity. In this work, the dynamic model of the transverse vibration of the functionally graded beam with an axial velocity is reviewed in brief firstly. Based on the dynamic symmetry breaking theory and the generalized multi symplectic method for the infinite dimensional system, a structure preserving numerical scheme for the dynamic model is developed. In the numerical simulation, the critical step length satisfying the generalized multi symplectic condition is obtained with the given material parameters. The first six frequencies of the transverse vibration model are presented employing the differential quadrature method, the complex modal method and the structure preserving method respectively. From the numerical results, it can be found that the first six frequencies obtained by using the structure preserving method are highly consistent with those obtained by using the complex modal method. To improve the precision of the differential quadrature method, the main factors resulting in the error are investigated. The main contribution of this work is proposing a new approach to analyze the complex dynamic problem like the transverse vibration of the functionally graded beam with an axial velocity considered in this paper.
    2022,20(6):106-113, DOI: 10.6052/1672-6553-2022-012
    Herglotz’s variational principle provides a variational description of non conservative dissipation problems, and variable mass mechanics is widely used in nature and engineering. Therefore, it provides a new way to study variable mass mechanics by applying Herglotz’s variational principle to Lagrange equations and conservation laws of variable mass mechanics systems. In this paper, the Herglotz type generalized variational principle of mechanical systems with variable mass is established and the Herglotz type Lagrange equations of mechanical systems with variable mass are derived. Herglotz type Noether symmetry of variable mass mechanical systems is defined, and the Herglotz Noether theorem and its inverse theorem are established and proved. At the end of this paper, two concrete examples of non conservative systems with variable mass are given to illustrate the application of the results.
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    2014,12(3):193-200, DOI: 10.6052/1672-6553-2014-046
    [Abstract] (2187) [HTML] (0) [PDF 748.46 K] (4773)
    The spacecraft's ability to adapt to the harsh dynamics environment is critical for the whole space mission. Vibration test control technology is the key part of the dynamic environment test. The current progress, fundamental principles and key techniques development level of the spacecraft and vibration control algorithms overseas were analyzed. The basic ideas, effective ways and suggestions were given to domestic following research.
    2014,12(1):18-23, DOI: 10.6052/1672-6553-2013-068
    [Abstract] (2252) [HTML] (0) [PDF 1.13 M] (4566)
    The electromechanical coupling model of cantilevered piezoelectric harvester was developed by considering the nonlinearities of piezoelectric material, based on Hamilton theory, Rayleigh-Ritz method, Euler-Bernoulli beam theory and constant electrical field across the piezoelectric element. The response characteristics of the system were investigated numerically, and the influences of piezoelectric material nonlinear coefficient on the system response were analyzed. By exploring the nonlinear characteristics of the piezoelectric vibrator near the resonant frequency, the nature of the multi-solutions and jump phenomena in the resonance region was revealed. The results were verified experimentally. which provides a theoretical basis for the study of nonlinear mechanism of piezoelectric power generation system.
    2015,13(5):361-366, DOI: 10.6052/1672-6553-2014-064
    Dynamic and control systems often contain uncertain parameters that may result in uncertain predictions. In the interest of quantifying the effects of parameter uncertainties on response variability, this paper develops a stochastic response surface based method for the sensitivity analysis of uncertain parameters. Stochastic response surfaces were firstly constructed to describe the explicit relationships between uncertain parameters and responses. Then partial derivations were performed on the mathematical expressions of stochastic response surfaces in order to obtain sensitivity indices that simultaneously embody the effects of parameter means and standard deviations. Lastly, the developed method has been verified against a numerical cantilever beam containing uncertain geometric and material parameters. The sensitivity analysis results were compared with those given by the analysis of variance method.
    2014,12(3):243-247, DOI: 10.6052/1672-6553-2014-054
    [Abstract] (2023) [HTML] (0) [PDF 1.07 M] (4314)
    Random vibration test is very important to the aerospace equipment. The windage of ASD outside the frequency bandwidth was analyzed. The reason, premonition, affection and effective way were given. And the commonly used random vibration test and vibration test metrology standard for the ASD outside the frequency bandwidth were analyzed.
    2017,15(5):385-405, DOI: 10.6052/1672-6553-2017-039
    [Abstract] (1328) [HTML] (0) [PDF 1.91 M] (4289)
    In this review article, the growth and related academic communications in the dynamics of multibody systems are firstly surveyed. Then, the recent advances in the numerical algorithms for solving the dynamic equations of flexible multibody systems, the contact/impact dynamics of flexible multibody systems and the deployment of flexible space structures are systematically reviewed, together with several open problems of concern. Finally, some suggestions are made for the prospective researches on the dynamics of flexible multibody systems.
    2014,12(3):225-229, DOI: 10.6052/1672-6553-2014-051
    [Abstract] (1661) [HTML] (0) [PDF 1.38 M] (3914)
    Based on the staggered solution procedure of ANSYS and CFX software, the fluid structure coupling response of projectile during tail slapping has been researched. Structural response was simulated by using FEM and flow field was simulated by using inhomogeneous model and SST turbulence model. Finally, the influences of fluid structure coupling effect have been analyzed and the change law of body stress has been given.
    2014,12(3):269-273, DOI: 10.6052/1672-6553-2014-043
    [Abstract] (2512) [HTML] (0) [PDF 336.30 K] (3878)
    Aiming at the problem that the longitudinal modes of structural system of rocket need to be identified from its integral modes in engineering, a method that automatically identifies the longitudinal modes of structural system of rocket was proposed according to the theory of modal effective mass. Taking the vibration characteristics of system with lumped mass as a computing example, applying the finite element software, the beam model of system with lumped mass was established, and the longitudinal modes of the system were automatically identified based on the method. Compared with the system modal information calculated by the method of modal analysis, this automatic identification method not only can accurately identify the longitudinal modes of vibrating system, but also has automatic and high efficiency identification feature. It provides a theoretical basis for the dynamic model of POGO vibrating system in liquid rockets and other model of engineering systems to be accurately and promptly established.
    2016,14(2):97-108, DOI: 10.6052/1672-6553-2015-009
    [Abstract] (1478) [HTML] (0) [PDF 1.87 M] (3746)
    Based on the current research status of multi agents system control theory and technology, the paper makes a detailed overview for unmanned ground systems. From two aspects of behaviour and task cooperative control for multi agents, the relevant theory and application problem is discussed. Moreover, some existed open problems are presented and a possible future development is proposed. For unmanned ground systems, cooperative control will be of great importance in promoting social and military benefits and maximizing the executive function of ground mission.
    2012,10(1):21-26, DOI:
    A discrete finite dimensional dynamical model was built to describe the space large overall motion of tethered satellite system with an infinite dimensional viscoelastic tether in a long time. The tethered satellite system is a complex nolinear dynamic system. Considering the tether’s viscoelasticity, distributed mass and space form, the established improved bead model can meticulously describe the tether’s vertical and horizontal vibration. According to tether’s characteristic of tensile and not compressive, the slack tether unit model was set up to accurately reflect real stress of tether. The determination of the number of degrees of freedom of the system was studied. Based on numerical integral calculation, the dynamic response was obtained via numerical simulation of the deployment, retrievement and retainment process of tethered satellite system in a long time. The result is convergent. The simulation proves the important role of the stable equilibrium position in the dynamics of tethered space system.
    2008,6(4):301-306, DOI:
    The problem of P and PI feedback control to a time delay system was investigated,with the emphasis on the determination of the feedback gains that ensured the asymptotical stability of the delayed system. By means of Lambert W function,the feedback gain of P control can be expressed explicitly,so that the optimal feedback gain can be easily obtained. For the system under a PI control,the stable region of the feedback gains was determined on the basis of stability switches and D subdivision,and the optimal feedback gains that enabled the system to admit maximal stable margin were figured out numerically by using Lambert W function. From the viewpoint of computation,the present method is much simpler than the available methods.
    2013,11(1):12-19, DOI: 10.6052/1672-6553-2013-003
    [Abstract] (1569) [HTML] (0) [PDF 530.95 K] (3460)
    The dynamics of the whole aero-engine system has always been the important part that cannot be neglected in the research and design of the engine, as the framework of the engine, the vibration of the casing directly reflects the level of the whole aero engine vibration. In this paper, an analysis was made on the research of the problems and fault classification of aero-engine casing dynamics, and an overview was made on the research of present situation, development trend, problems and solutions of the domestic and foreign of casing dynamics, which expanded the present situation of the Inclusiveness problems of aero-engine casing dynamics. Finally, some proposals were put forward for the development of the casing dynamics suitable for our country aero-engine technology level.
    2014,12(2):183-187, DOI: 10.6052/1672-6553-2014-025
    [Abstract] (1028) [HTML] (0) [PDF 811.52 K] (3332)
    PMSM due to little harmonic, high precision torque, commonly is used in the servo system and the high performance speed control system. In this paper,the physical model of PMSM is simplified and the mathematical model of the motor is established in order to facilitate research.Thispaper uses id=0 control manner which is the simplest manner is vector control methods,motor electromagnetic torque equation is established based on rotor field oriented vector control.The system model, speed and current control block are build and simulated with MATLAB/Simulink.Simulation results shows that the waveform is consistent with thoretical analysis,the model has fast response and small overshoot.The system runs stably with good dynamic and static characteristics. The simulation makes full use of modularization design. All the parameters and their influence on the system can be changed and observed.It also can easily validate the control strategies and select the most suitable one. So this kind of simulation is good for system design and adjusting and validating.
    2013,11(4):357-362, DOI: 10.6052/1672-6553-2013-041
    At present, the main task of designing a mounting system of automotive engine powertrain is to select appropriate stiffness, position and angle of mounting components so that free-vibration modal frequency of the mounting system can avert from the exciting-force frequency at the idle speed of the engine and the natural frequency of vibration of the vehicle body and that the decoupling degree of each mode shape is increased as far as possible, so as to improve the vibration-isolation effect of the mounting system. The design of a mounting system based on strict decoupling at predetermined frequencies is to make the modal frequencies of the designed mounting system completely equal to the frequencies predetermined in accordance with the frequency planning of automotive design, and to enable strict decoupling of each mode shape of each mode, i.e., the decoupling degree of vibration energy in every direction equals to 1. Based on a free-vibration equation for a mounting system, this paper presents an equation system for designing a mounting system with strict decoupling at predetermined frequencies, provides a solving method for this equation system by using the theory of generalized inverse matrix or method of constructing function, so as to provide an optimal design method more efficient and simpler than the current modal optimization method of mounting system. Relevant example has validated the correctness of equations and solving method of the strict-decoupling design at predetermined frequencies.
    2014,12(3):283-288, DOI: 10.6052/1672-6553-2014-061
    [Abstract] (2164) [HTML] (0) [PDF 479.50 K] (3269)
    A method was presented to analyze the nonlinear flutter. Based on this method, the flutter characteristics of the high aspect wing were illustrated. The numerical results show that the flutter speed is decreased when the first horizontal bending mode involved. Secondly, this study discussed how the main direction of the composite influenced the character of the nonlinear vibration and flutter, and established the method of the flutter clipping to the high aspect wing. And the result shows that the stiffness of structure can be changed by changing the main direction of the composite. It mainly changes the horizontal bending mode, makes the main direction tend to the trailing edge, and then makes the section line move to the leading edge. Further analyzing the nonlinear flutter reveals that it is the changing of the horizontal bending mode that causes the flutter speed change obviously. And by the section line of this mode moves ahead, the flutter speed will become larger. In the study, two examples were illustrated to validate its truthiness.
    2014,12(3):205-209, DOI: 10.6052/1672-6553-2014-059
    [Abstract] (1732) [HTML] (0) [PDF 467.15 K] (3246)
    This paper investigated the passive nonlinear vibration control method used for energy absorbing in structures of spacecrafts. The structure and the dynamic model of the nonlinear energy sink which could adapt to the space environment were proposed. As nonlinear spring could not be acquired easily in reality, we proposed a new design for the NES based on employing an asymmetric NES force which was generated by two pairs of aligned permanent magnets. Then, the dynamic model for a cantilever beam structure coupled with nonlinear energy sink had been built theoretically. In addition, the passive vibration suppression effect of the nonlinear energy sink on the cantilever beam structure under transient excitation had been analyzed through Galerkin method and numerical analysis method. The results showed that the NES acquired up to 92% dissipation of the system energy imposed by shock excitation, hence the NES could adapt to the space environment and improve the reliability of space system.
    2014,12(3):253-258, DOI: 10.6052/1672-6553-2014-056
    [Abstract] (1534) [HTML] (0) [PDF 1.00 M] (3167)
    Taking account of the structural stiffness and the low order vibration frequencies, two schemes of multi-objective topology optimization were proposed to obtain the best aircraft lifting-surface structural design. Based on penalized density theory, the scheme one (named as constrain method) is to convert the multi-objective optimization to single-objective optimization by considering the minimum structural mass as the objective with constraints of reference points displacements and the low order vibration frequencies. The scheme two (named as the combination of constrain method and criterion function method) settles the multi-objective optimization by defining combined compliance index (CCI) as the objective, with the constraints of volume fraction and the low order vibration frequencies. The CCI is the function of structural compliance and low order vibration frequencies. Numerical results demonstrate the proposed schemes not only realize reducing the structural mass but also raise the first and second order frequencies.
    2016,14(3):247-252, DOI: 10.6052/1672-6553-2015-052
    [Abstract] (1368) [HTML] (0) [PDF 2.18 M] (3165)
    Tires are the only carrier of the contact between the vehicle and road surface. Their mechanical property is important for analysis and control on the vehicle dynamic response. At present, the tire simulation mostly focuses on the steady state model. But it can not describe the dynamic characteristic of the tire accurately. Therefore, it plays a significant role to add the dynamic tire model in the vehicle dynamics simulation. The tire friction model in the multi body dynamical software ADAMS is static, where the friction is regarded as a static value. However, in actual, the friction between the tire and road surface is dynamic, and it should be a dynamic function of the relative velocity and displacement. To this end, in this paper, the dynamic tire LuGre model using the Matlab/Simulink software is constructed. Through connecting the interface with Adams/Car, co simulation between the vehicle model and the simulink tire model is carried out in order to achieve the dynamic contact between tire and road and improve the accuracy of vehicle system analysis.
    2014,12(1):36-43, DOI: 10.6052/1672-6553-2013-110
    [Abstract] (1363) [HTML] (0) [PDF 2.22 M] (3095)
    The coupling nonlinear dynamic model of dual rotor system was established by using finite element method, and then the critical speed of revolution and mode shape were calculated by using the software MATLAB. In addition, the unbalance responses of dual rotor system were studied, and the vibration performances in different speeds of dual rotor casing systems were obtained. The research provides a theoretical basis for the design of the dual rotors system in engineering.
    2014,12(3):201-204, DOI: 10.6052/1672-6553-2014-048
    [Abstract] (1817) [HTML] (0) [PDF 296.79 K] (3005)
    Non-linear factors cannot be avoided in the design of aircraft structures. In this paper, a two-degree-of-freedom airfoil and cubic stiffness nonlinearities in pitching degree-of-freedom operating in supersonic flight speed regimes has been analyzed. The averaging method and the theory of flutter were used to analyze the nonlinear dynamic system of the dualistic airfoil in the supersonic flow. Then the correctness of the theoretical calculation was verified by numerical calculation, and the analysis result was given.
    2014,12(1):62-66, DOI: 10.6052/1672-6553-2013-097
    [Abstract] (1005) [HTML] (0) [PDF 832.87 K] (2922)
    A spline finite point method was presented to study the natural frequency of arch. The displacement mode shape function of the arch free vibration was simulated with a linear combination of cubic B spline. The free vibration frequency equation of arch structures was derived according to Hamilton principle, in which the effect of the dead load was considered. Meanwhile, the effect of the dead load on the natural frequency of arch structures was analyzed. The results show that the natural frequency of arch is reduced. The effect of influence depends on the stiffness of the arch itself. When the arch stiffness is certain, the bigger the rise span ration and the radius to thickness ration, the higher the effect of the dead load on the natural frequency of arch structures.

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