20 results about "Modal damping ratio" patented technology

The invention relates to a large-span bridge flutter critical wind speed prediction method based on an L-P perturbation method. The method comprises the following steps that S1, physical characteristics and aerodynamic parameters of a bridge are obtained through a wind tunnel test to serve as basic data; s2, establishing a bridge motion control matrix equation based on modal displacement; s3, deriving an explicit solution of the modal frequency, the damping ratio and the modal characteristic of each modal branch based on an L-P perturbation method; s4, iteratively solving the modal frequency, directly solving the damping ratio, the amplitude ratio and the phase difference on the basis, observing the change of the modal damping ratio xi in each direction along with the wind speed U, and determining the flutter critical wind speed; the problems that an explicit closed solution of an existing three-degree-of-freedom flutter starting condition needs to carry out multiple times of iterative calculation on modal frequency, damping ratio and vibration mode, the influence of structural parameters and pneumatic parameters on pneumatic instability is difficult to clearly explain, and the flutter critical wind speed of a large-span bridge cannot be well predicted are solved.

The invention discloses a bridge dynamic performance rapid evaluation method based on dynamic displacement multi-parameter analysis. The method comprises the core steps that S1, a bridge theoretical fundamental frequency f theory and a theoretical impact coefficient mu theory are calculated, and dynamic load efficiency parameters are calibrated; s2, when the bridge is in a good state, the worst vehicle speed Vc, the maximum impact coefficient initial value mumax initial, the fundamental frequency initial value f initial, the first-order modal damping ratio initial value D initial and the quasi-static deformation reference value Ss are measured through a special loading vehicle; s3, collecting and processing daily patrol dynamic displacement data, and rapidly extracting and analyzing an actual measurement fundamental frequency f actual measurement, an actual measurement impact coefficient mu max actual measurement and an actual measurement damping ratio D actual measurement; and S4, comprehensively evaluating the dynamic performance of the bridge by analyzing the change conditions of the f actual measurement, the mumax actual measurement and the D actual measurement. According to the method, standardized rapid testing is achieved, single-time inspection only needs several minutes, traffic interruption is not needed, the rigidity, impact resistance and energy dissipation characteristics of the bridge structure are efficiently evaluated by means of the multiple objectively-quantified power parameters (the fundamental frequency, the impact coefficient and the damping ratio), and the scientificity and efficiency of daily inspection are remarkably improved.

The invention discloses a rotor craft aeroelastic stability prediction method, and relates to the field of rotor dynamics, the method comprises the following steps: constructing a nonlinear aeroelastic dynamics control equation, and determining dynamics sensitive parameters; constructing an input sample data set; obtaining an output sample data set based on the input sample data set and the nonlinear aeroelastic dynamics control equation; constructing a sample data set based on the input sample data set and the output sample data set; constructing an initial aeroelastic stability prediction model based on the de-noising diffusion probability model; training the initial aeroelastic stability prediction model by adopting the sample data set to obtain an aeroelastic stability prediction model; acquiring the working condition of the rotorcraft in real time to determine the value of the dynamic sensitive parameter of the rotorcraft; inputting the values of the dynamic sensitive parameters into the aeroelastic stability prediction model to obtain a corresponding modal damping ratio; and determining the aeroelastic stability of the rotorcraft based on the modal damping ratio. According to the method, the aeroelastic stability of the rotorcraft can be accurately predicted.

This application provides a method for forced response analysis of an integral bladed disk (IBD), comprising: constructing a finite element model of an IBD sector; conducting disk-coupled resonance analysis of the finite element model to obtain the frequency, mode shape, and relative vibration stress of the IBD blades under one to multiple node diameters, and plotting disk-coupled resonance diagrams; determining the critical node diameter related to the number of rotor and stator blades; determining the frequency order and corresponding critical resonance speed by combining the plotted disk-coupled resonance diagrams and the critical node diameter; performing damping tests on the IBD blades to obtain the frequency order and corresponding modal damping ratios; establishing a full-ring model of the IBD rotor blades and the stator blades before and after them; conducting steady flow field analysis of the full-ring model to obtain steady results as the initial field conditions for unsteady flow field analysis; conducting unsteady flow field analysis to obtain the actual vibration stress of the IBD; and conducting dynamic strength reserve analysis to evaluate the dynamic strength reserve of the high-load IBD under the analysis conditions.

A modal damping ratio identification method, system, device and computer readable storage medium, relating to the technical field of bridge engineering, specifically comprising: performing variational modal decomposition on the free vibration response of the target bridge to obtain a plurality of connotative modal components; determining the attributes of each connotative modal component based on the time domain and frequency domain characteristics of each connotative modal component, and taking the connotative modal component with the actual modal response attribute as the target connotative modal component; performing Hilbert transform on the target connotative modal component, and determining the target instantaneous amplitude and the target instantaneous frequency corresponding to the target connotative modal component based on the results of the Hilbert transform and the target connotative modal component; determining the instantaneous modal damping ratio corresponding to the target connotative modal component based on the target instantaneous amplitude and the target instantaneous frequency, so as to obtain the amplitude correlation of the modal damping ratio. The application improves the modal damping ratio identification precision.

This invention relates to a method for predicting the critical flutter wind speed of long-span bridges based on the L-P perturbation method, comprising the following steps: S1, obtaining the physical characteristics and aerodynamic parameters of the bridge as basic data through wind tunnel tests; S2, establishing the bridge motion control matrix equation based on modal displacement; S3, deriving explicit solutions for the modal frequencies, damping ratios, and modal characteristics of each modal branch based on the L-P perturbation method; S4, iteratively solving the modal frequencies, and directly solving the damping ratio, amplitude ratio, and phase difference on this basis, observing the change of the modal damping ratio ξ with the wind speed U in each direction, and determining the critical flutter wind speed; solving the problem that the existing explicit closed-form solution of the three-degree-of-freedom flutter initiation condition requires multiple iterative calculations of the modal frequencies, damping ratios, and mode shapes, and is difficult to clearly explain the influence of structural and aerodynamic parameters on aerodynamic instability, thus failing to accurately predict the critical flutter wind speed of long-span bridges.

This invention discloses a method for optimizing the multimodal damping ratio of a cable-composite damper-cable-end damper system, comprising the following steps: S1, constructing a coupled system of cable-composite damper-cable-end damper; S2, calculating the damped vibration frequency, damping ratio of each mode, and mode shape of the coupled system; S3, optimizing the multimodal damping ratio of the coupled system. This invention constructs a coupled system consisting of a conventional damper, a damped damper, and a cable-end damper working collaboratively. Then, using the average normalized damping ratio of the multimodal damping ratio as the optimization index, the method systematically optimizes key parameters such as the stiffness and damping of the composite damper, the damping coefficient of the cable-end damper, and its installation position to achieve an overall and balanced improvement in the damping level of each mode.

This invention discloses a method for identifying operating mode damping, a damage detection method, a system, and equipment. It involves acquiring the time-domain response signal of the structure under test in the form of random subsamples to obtain multiple sets of random subsample signals. The cross-correlation function of each set of random subsample signals is calculated using natural excitation technology to obtain free vibration signals. The sparse coefficient matrix of each free vibration signal is calculated using an orthogonal matching pursuit algorithm. The modal damping ratio is determined based on the sparse coefficient matrix, thereby identifying the operating mode damping of the structure under test. The operating mode damping identification method disclosed in this embodiment uses a random subsample signal acquisition method, which meets the requirements of natural excitation technology, enabling the identification of modal damping under operating excitation. Furthermore, the identification framework used in this embodiment is frequency-mode shape-damping, which improves the identification accuracy and provides technical support for the accurate identification of structural damage.

The invention relates to the technical field of numerical control machining and intelligent manufacturing, and discloses an intelligent machining control method and system for automobile part milling. The method comprises the steps that a vibration signal and stress data are obtained and preprocessed to obtain a time domain sequence; resolving the time domain sequence to obtain a modal damping ratio time-varying characteristic sequence; analyzing rigidity fluctuation and a critical state, and predicting a damping ratio trend to lock an advanced intervention opportunity point; generating a variable parameter control instruction sequence according to the intervention opportunity point; screening an optimal control parameter combination based on an efficiency and life model; and outputting a final flutter suppression signal in combination with real-time vibration feedback. According to the method, the dynamic change of the damping ratio can be tracked in real time, the flutter is accurately intervened in advance, and the production efficiency and the service life of the cutter are both considered while the machining stability is guaranteed.

The present application relates to a kind of transmission line galloping critical wind speed prediction method based on L-P perturbation method, comprising the following steps: S1, the physical characteristics and aerodynamic parameters of transmission line are obtained by wind tunnel test as basic data;S2, establish the motion control matrix equation of transmission line based on modal displacement;S3, explicit solution of modal frequency, damping ratio and modal characteristics of each modal branch is derived based on L-P perturbation method;S4, iteratively solve modal frequency, on this basis directly solve damping ratio, amplitude ratio and phase difference, observe the change of modal damping ratio ξ in each direction with wind speed U, determine the critical wind speed of galloping;The explicit closed solution of the existing three-degree-of-freedom galloping start-up condition needs to be calculated multiple times iteratively on modal frequency, damping ratio and mode shape, and it is difficult to clearly explain the influence of structural parameters and aerodynamic parameters on aerodynamic instability, and the critical wind speed of transmission line galloping cannot be well predicted.

The application discloses a propeller shaft system abnormal torsional vibration diagnosis method, device, equipment and storage medium, relates to the ship propulsion system technical field, and the method comprises the steps of obtaining the torsional vibration inherent frequency and the torsional vibration mode shape under a plurality of target orders of the propeller shaft system; calculating the modal mass and the modal damping ratio under each target order of the propeller shaft system, and calculating the support reaction force at the rear stern bearing and the front stern bearing; fitting the friction coefficient between the rear stern bearing, the front stern bearing and the propeller shaft system; according to the support reaction force, the friction coefficient and the torsional vibration mode shape under the target order, the friction excitation torque under the corresponding order torsional vibration mode shape is calculated, and the corresponding Taylor expansion coefficient of the friction excitation torque; according to the torsional vibration inherent frequency, the modal mass, the modal damping ratio and the Taylor expansion coefficient under the target order, it is judged whether the torsional vibration mode of the target order of the propeller shaft system is abnormal vibration. According to the shaft system design parameters, whether the friction torsional abnormal vibration will be generated can be predicted.

The invention relates to the technical field of finite element analysis, in particular to a viscous damping wall vibration attenuation performance analysis method based on finite element analysis, and the method comprises the steps: building a finite element model of a high-rise building structure, carrying out undamped modal analysis on the finite element model, extracting a mass matrix and a stiffness matrix, reading a modal vector of a dominant modal, and calculating the vibration attenuation performance of the high-rise building structure; calculating the inherent frequency and modal quality of the dominant mode; a simulation experiment is conducted on the finite element model, the equivalent modal damping ratio of the high-rise building structure is obtained, the peak displacement of the finite element model with the viscous damping wall is estimated, the estimation result and the design requirement are compared and judged, and the additional damping ratio is adjusted; determining the total viscous damping coefficient of the high-rise building structure; the nominal damping coefficient of each viscous damping wall is determined; and a damper unit in the finite element model is continuously adjusted, so that the finite element model with the viscous damping wall meets the design requirement. According to the method, the vibration attenuation performance analysis and design efficiency of the viscous damping wall can be improved.

The application relates to a wind power tower structure provided with a high-strength steel constraint damping enhancement section and a design method thereof, wherein the high-strength steel constraint damping enhancement section comprises a high-strength material layer, a damping layer and a constraint layer, the upper and lower ends of the high-strength material layer are connected with a non-energy dissipation section of a tower body respectively, the damping layer and the constraint layer are not directly connected with the non-energy dissipation section, the damping layer is attached to the high-strength material layer on one side and is attached with the constraint layer on the other side; the design method comprises the following steps: firstly, performing preliminary design on a wind power tower and a foundation thereof and determining the arrangement position of the high-strength steel constraint damping enhancement section; using high-strength steel to process the high-strength material layer; through modal damping ratio calculation, performing parameter analysis and optimization on the high-strength steel constraint damping enhancement section, and determining corresponding structure schemes and additional damping. Compared with the prior art, the application can overcome the limitations of current inertia-based and material-based technologies, realize the synergistic enhancement effect of the additional damping, reduce the steel consumption and improve the damping effect.

To provide an evaluation method of unstable vibration of a current collector for evaluating the presence or absence of unstable vibration generated in the current collector by a simple method without requiring parameter identification of the current collector.SOLUTION: A method of evaluating unstable vibration occurring in a current collector comprises: a step of dividing the whole system, which is the current collector when in sliding contact with an overhead line, into a plurality of sub-systems including a sub-system (1) including the current collector and a sub-system (2) including the overhead line; a step of acquiring the frequency response function of the sub-system (1) at the point of contact with the overhead line in contact with the current collector; a step of setting the stiffness, damping, and friction coefficient of the sub-system (2); a transfer function synthesis step of estimating the frequency response function of the whole system from the frequency response function of the sub-system (1) and the stiffness, damping, and friction coefficient of the sub-system (2); A process for identifying a mode characteristic based on a frequency response function of the whole system and identifying a mode damping ratio of the whole system, and stability evaluation of the whole system based on the mode damping ratio are performed.SELECTED DRAWING: Figure 2

The invention relates to a power transmission line galloping critical wind speed prediction method based on an L-P perturbation method. The method comprises the following steps that S1, physical characteristics and aerodynamic parameters of a power transmission line are obtained through a wind tunnel test to serve as basic data; s2, establishing a power transmission line motion control matrix equation based on modal displacement; s3, deriving an explicit solution of the modal frequency, the damping ratio and the modal characteristic of each modal branch based on an L-P perturbation method; s4, iteratively solving the modal frequency, directly solving the damping ratio, the amplitude ratio and the phase difference on this basis, observing the change of the modal damping ratio xi in each direction along with the wind speed U, and determining the galloping critical wind speed; the problems that an explicit closed solution of an existing three-degree-of-freedom galloping starting condition needs to carry out multiple times of iterative calculation on modal frequency, damping ratio and vibration mode, the influence of structural parameters and pneumatic parameters on pneumatic instability is difficult to clearly explain, and the galloping critical wind speed of a power transmission line cannot be well predicted are solved.

The invention discloses a blade vibration testing device coupled with a composite material friction element and a parameter optimization method of the blade vibration testing device. The blade vibration testing device comprises a basic platform, at least two simulation blade test pieces and a wedge-shaped friction element, each simulation blade test piece is fixed on the foundation platform, a damping structure is arranged on each simulation blade test piece, and a wedge-shaped contact surface is arranged at the end part of each damping structure; the wedge-shaped contact surfaces of two adjacent simulation blade test pieces are oppositely arranged; and the wedge-shaped friction element is arranged between the wedge-shaped contact surfaces of the two adjacent simulation blade test pieces. Applying harmonic excitation to the blade body surface of the simulation blade test piece; the instantaneous attenuation response of the simulation blade test piece is measured, the first-order bending vibration response is obtained through Fourier transform, and the first-order modal damping ratio of the simulation blade test piece is obtained through calculation. The influence of the friction damping effect at different positions on the vibration reduction effect can be explored, and the optimal geometric parameters of the wedge-shaped friction elements at all positions can be obtained.

The application belongs to the field of helicopter structure strength design, and relates to a method and device for obtaining body modal parameters through simulation analysis. The method comprises the following steps: optimizing a full machine dynamics model based on the requirement of ground resonance and tail rotor tail beam coupling stability calculation; adding structural damping of the body in the existing full machine dynamics model for the requirement of tail rotor tail beam coupling stability calculation; for a typical state, carrying out complex modal calculation based on a dynamics model of the body on the landing gear to obtain modal frequency, modal damping ratio, modal mass, modal shape and modal vector of the body on the landing gear; obtaining a modal shape of a key point from the modal shape, and obtaining a modal vector of the key point from the modal vector according to the modal shape of the key point; converting the modal mass into normalized modal mass according to the modal vector of the key point ， so as to calculate corresponding modal stiffness and modal damping.

The application discloses a particle damper damping performance test method and device, and a computer program product. The fixed end of the particle damper mounting substrate of the test device is arranged on a fixed support, and the free end of the particle damper mounting substrate is arranged away from the fixed support. The excitation unit is used to be connected with the excitation input point of the particle damper mounting substrate to send an excitation signal to the particle damper mounting substrate. The detection unit is arranged on the particle damper mounting substrate and is used to detect the acceleration change caused by the excitation signal. The control unit is used to obtain the first modal damping ratio of the particle damper mounting substrate and the second modal damping ratio after placing the particle damper to be tested according to the vibration frequency response curve obtained from the acceleration change. By comparing the first modal damping ratio and the second modal damping ratio, the test precision can be effectively improved, and good technical support is provided for evaluating the damping performance of the particle damper.

The invention discloses a floating fan damping control device and method based on a tuning multi-liquid-column damper. The system comprises a tuning multi-liquid-column damper installed on a floating platform, the tuning multi-liquid-column damper comprises a plurality of vertical liquid columns connected through a horizontal pipeline, and the horizontal pipeline is provided with a flow control valve and a controller. According to the method, the nonlinear water shake damping force of the TLMCD is equivalent to a linear damping term through a statistical linearization technology, and a linearization model suitable for modal analysis is established; key parameters of modal frequency and modal damping ratio are extracted, difference of dominant modal damping ratio is compared, and an influence mechanism of the modal damping ratio on vibration attenuation performance of the TLMCD is disclosed; and on the basis of the optimal damping parameter, continuous control is achieved by dynamically adjusting the head loss coefficient of the flow control valve. According to the method, the analysis and design problems of TLMCD nonlinear damping are solved, and the vibration suppression performance and the system robustness of the semi-submersible wind turbine under complex random wind wave excitation are improved.

The invention discloses a method, a system, equipment and a medium for dynamically adjusting a network following-network constructing rated capacity ratio and operation output. The method comprises the following steps of: determining a dominant modal damping ratio of a new energy station by utilizing a modal analysis method; when the dominant mode damping ratio is larger than the dominant mode damping ratio lower bound required by small disturbance stability or the stability improvement effect is lower than the minimum stability margin improvement limit, the rated capacity ratio of the new energy station is determined; based on the rated capacity ratio, the number of the converters under the network following control condition and the network construction control condition is determined, and when the new energy station is small in power generation, the converters under the network following control condition bear all active power output in the station, and the converters under the network following control condition do not output power; and when the new energy station is in a large power generation state, all the converters in the network following control condition are in a rated output state, and the remaining active output is borne by the converters in the network construction control condition. According to the invention, full-scene stability and stability margin optimization can be realized.