58 results about "Modal damping ratio" patented technology

The invention discloses a steam turbine blade vibration test method and device. The method steps are that firstly, a blade force vibration status is analyzed and a blade excitation force mathematical model is built. Secondly, an excitation force is imposed on the blade by a vibration source. The frequency of the excitation force is regulated until resonance is generated between the blade and the vibration source. Vibration characteristics parameters values of the blade under the excitation force are measured. Thirdly, blade damping characteristics parameters, including modal damping ratio, damper contact stiffness and blade dynamic stress, are worked out according to the vibration characteristics parameters values. The device includes a test bed, a blade clamping mechanism arranged on the test bed, an excitation generator, a vibration parameter detector and a data processing system. The excitation vibration generator is fixed on the test bed. The excitation vibration head of the excitation vibration generator is fixed with the blade. Corresponding to the blade, the vibration parameter detector transforms the vibration signals of the blade into electric signals, which are input into the data processing system. The invention proves the vibration mechanism of the damping blade. A calculation model of the damping blade is constructed through the test parameters. Experience design is terminated. The blade design is standardized to step into a scientific design orbit.

The invention discloses a modal damping ratio rapid calculation method based on a pulse excitation response spectrum. The method comprises the following steps: firstly, determining excitation and vibration pick-up positions of a structure, wherein the excitation and vibration pick-up positions are on a node and a nodal line adjacent to a modal shape, and have remarkable responses under various test modal shapes; recording a vibration pick-up point response signal by a signal acquisition device, and performing discrete Fourier transform to obtain a response spectrum; extracting corresponding responses under a resonance (or peak) frequency an adjacent frequency thereof on the basis to obtain a stable response amplitude; and lastly, calculating relevant parameters such as a frequency ratio and a response ratio in order to realize identification of a modal damping ratio of the structure. Through adoption of the method, the technical problems that semi-power points are difficult to find accurately in a conventional semi-power method, a frequency response function needed for calculating the modal damping ratio cannot be acquired sometimes in a frequency domain method since certain excitation time domain signals are difficult to measure directly, and transient components are attenuated incompletely, operations are complicated and the like in response under contact type excitation in the prior art can be solved.

The invention discloses a method, a device, and a system for modal damping identification. The method for modal damping identification comprises steps: obtaining amplitude-frequency data of a rotor, and phase-frequency data; according to the obtained amplitude-frequency data, drawing an amplitude-frequency curve, determining a critical rotation speed point; according to the obtained phase-frequency data, drawing and fitting a phase-frequency curve, to obtain a fitted phase-frequency curve equation; according to the fitted phase-frequency curve equation, calculating the slope of the tangent line of the critical rotation speed point in the phase-frequency curve; and according to the calculated slope, obtaining a modal damping ratio. The method for modal damping identification conveniently and accurately determines critical rotation speed from the amplitude-frequency curve. By using the slope of the tangent line of the critical rotation speed point in the phase-frequency curve and the damping ratio are in a reciprocal relationship, the modal damping ratio is identified, so as to conveniently, rapidly, and accurately obtain the modal damping ratio.

The invention provides an identifying method for a modal parameter of a flexible satellite capable of restraining gyro noise influence. The method comprises the following steps: utilizing measuring data of a satellite body angular velocity while the satellite flies in an orbit to identify a modal frequency and a modal damping ratio parameter of the whole satellite; approximately regarding the measuring noise of the gyro in a short-term period as two parts, namely, constant drifting and random drifting; and performing differential treatment on the gyro data and utilizing the property of Gaussian noise three-order accumulated quantity constantly being zero to restrain the influences of the two parts of noises on an identifying result. Compared with the prior art, the identifying method for the modal parameter of the flexible satellite capable of restraining gyro noise influence can utilize the measuring data of the gyro on the satellite to perform modal parameter identification and restrain the measuring noise, so that the identification precision of the algorithm is increased.

A prediction method according to the present invention is a method for predicting a modal damping ratio of a composite head including two or more kinds of materials including a first material and a second material. The method includes the steps of: presuming at least a coefficient Px of a generalized Maxwell model M1 in the first material using a known material damping ratio ζ1; obtaining a calculation model of the head using the generalized Maxwell model M1; and calculating the modal damping ratio of the head based on analysis of the head using the calculation model. Preferably, the Maxwell model is further used also for the second material. Preferably, the method further includes the step of presuming a coefficient Py of a generalized Maxwell model M2 in the second material using a known material damping ratio ζ2.

The invention discloses a method and a device for judging movement stability of a railway vehicle bogie, and relates to the technical field of railway vehicles. Through cooperation of steps, in a line operation state, difficulty in recognizing snake movement vibration modal of the railway vehicle bogie is overcome, and long-term evolution trend of a railway vehicle can be acquired to determine allowance of movement stability of the railway vehicle. By the method and the device, interference, of line excitation factors like line irregularity, on recognition of snake movement modal damping ratio of the bogie can be effectively excluded, and interference, of influencing factors like elastic vibration of mounting parts and rotation excitation of rotating parts like a motor and a wheel pair on the bogie, on recognition of the snake movement modal damping ratio of the bogie can be effectively excluded.

The invention discloses a dynamic calibration method for a high-frequency force balance, which comprises the steps of performing whitening on a measurement signal x(t) to acquire a whitened signal z(t); seeking an orthogonal matrix V, enabling the whitened signal z(t) to equal to Vq(t), and thus acquiring a separated signal q(t); performing natural frequency and modal damping ratio recognition on the separated signal in modal coordinates; correcting the separated signal according to recognized parameters; and inversely deducing according to the separated signal to acquire a corrected pneumatic load. According to the invention, separation is performed on a coupling signal, and for independent components acquired by separation, natural frequency and modal damping ratio recognition is performed on the separated signals one by one by adopting a curve fitting method through combining aerodynamic characteristics, so that a dynamic amplification effect of a modal coupling system is corrected and eliminated, a real aerodynamic load spectrum density matrix is acquired finally, the reliability of parameter recognition and corresponding HFFB (High-Frequency Force Balance) dynamic signal calibration can be improved to the maximum extent, and an important basis is laid for subsequent accurate estimation for high-rise building prototype wind-induced responses.

The invention provides a valuation method for a general equivalent damping ratio of a large-scale cooling tower based on field measurement. The valuation method for the general equivalent damping ratio of the large-scale cooling tower based on the field measurement comprises the following steps: a, building a finite element model of the large-scale cooling tower; b, performing dynamic characteristic analysis on the finite element model; c, extracting mass participating coefficient ratios of vibration modes of all orders; d, performing the field measurement on the large-scale cooling tower to obtain a structural damping ratio by modal analysis; e, by considering all order damping ratios and vibration mode mass participating coefficients of corresponding orders, calculating to obtain equivalent modal damping ratios of all the orders; f, performing integration analysis to obtain the general equivalent damping ratio of an integral structure of the large-scale cooling tower. By using the valuation method for the general equivalent damping ratio of the large-scale cooling tower based on the field measurement, the limitation that a value range or a mean value of a damping ratio is only given out in dynamic analysis of a traditional cooling tower structure is overcome, and the accuracy and the reliability of wind resistance and earthquake proof analysis of the large-scale cooling tower are effectively improved.

The invention discloses a three-dimensional acousto-elastic analysis method of a ship for arbitrary damping processing of a structure and relates to the technical field of acoustics. The method comprises the steps of performing modal analysis on a finite element model of a ship structure with an initial damping laying layer to obtain a modal damping ratio of modalities at various orders of the ship structure; substituting the modal damping ratio of the modalities at various orders of the ship structure into an acousto-elastic coupling dynamic equation of the ship structure to obtain a composite structure dynamic equation of the ship structure; and performing vibration noise analysis on the coupling dynamic equations by use of a three-dimensional acousto-elastic theory of the ship. A damping laying optimization design scheme for the ship structure with structural acoustic radiation as an optimization objective is provided. According to the three-dimensional acousto-elastic analysis method of the ship for arbitrary damping processing of the structure, the direct vibration noise analysis for the laying-damped ship structure is implemented, and the method can be widely used for processing of the damping structure when the vibration noise of the ship is calculated and can provide a technical support for the damping laying design of the ship.

A servo controller includes: a sinusoidal wave disturbance input unit for supplying a sinusoidal wave disturbance to a speed control loop including a speed command generator, a torque command generator and a speed detector; a frequency response calculator for estimating the gain and phase from the output of the speed control loop; a resonance frequency detector for detecting resonance frequencies at which the gain becomes maximum; a resonance mode characteristics analyzer for estimating resonance characteristics from the frequency response; and, a reference modal damping ratio retainer for retaining a reference modal damping ratio as a resonance characteristic corresponding to the reference lubricating condition, and the resonance mode characteristics analyzer calculates lubrication characteristics on the basis of the reference modal damping ratio and the measured modal damping ratio at the resonance frequency corresponding to the reference modal damping ratio.

The invention belongs to the field of structural vibration control, and in particular relates to a semiactive stay cable control method of a variable damper based on non-linear friction type damping. The method provided by the invention comprises the following steps that: according to displacement amplitude of a cable at a damper, a damping force is continuously regulated from high to low; and under the action of a corresponding damping force, displacement of the damper is always located in the previous period when the damper is locked, thus the obtained modal damping ratio is always high. A concrete semiactive control algorithm is that the modal damping ratio obtained in each period is equal to an attenuation curve of a stabilization system, wherein the attenuation curve is in exponential attenuation. The damping force provided by the invention is always dissipated, thus performance is stable and robustness is good. The system modal damping ratio obtained by the invention is higher and is much higher than a passive optimal modal damping ratio obtained by a linear viscous damper, thus a damping effect is good. The semiactive control method provided by the invention is simple and practical and is convenient to operate.

The invention belongs to the technical field of instrument calibration, and discloses a time domain calibration method for a high-frequency base force balance signal. The method comprises the following steps: 1, inputting an observation signal x(t); 2, decoupling the observation signal x(t) in real time to obtain a decoupled modal signal q(t); 3, performing modal parameter identification on the modal signal q(t) under the modal coordinates; 4, constructing a digital filter to correct the modal signal q(t) according to a modal parameter identification result; and 5, obtaining a corrected aerodynamic load time history y(t) through back-stepping according to the corrected modal signal. According to the invention, an adaptive blind source separation algorithm is adopted to carry out online decoupling on a measurement signal, natural vibration frequency and modal damping ratio identification is carried out on a modal signal obtained through decoupling, a corresponding digital filter is further constructed, a corrected real aerodynamic load time history is finally obtained, and further time history analysis is facilitated. The defects that an existing correction method can only decouple signals in an off-line mode and cannot obtain the corrected aerodynamic load time history are overcome.

The invention discloses a thick plate rolling mill filled with particle damping and a filling method of the thick plate rolling mill. The rolling mill comprises rolling mill beams, a rolling mill house, an exhaust device, the particle damping and a blind plate. The rolling mill comprises the upper rolling mill beam and the lower rolling mill beam. A particle damping filling space is formed by the upper rolling mill beam, the lower rolling mill beam and the rolling mill house. The exhaust device is arranged on the upper rolling mill beam. The exhaust device communicates with the particle damping filling space. The lower rolling mill beam is provided with the blind plate. The blind plate is arranged in the particle damping filling space. By the adoption of the thick plate rolling mill filled with the particle damping and the filling method, the modal damping ratio of a rack in the horizontal direction and the vertical direction can be increased effectively, the attenuation amount of vibration energy on the transmission path of the rolling mill rack is increased greatly, the fatigue failure of related parts of the rolling mill is restrained effectively, the quality, accuracy and productivity of products are further improved, the downtime maintenance time is shortened greatly, and therefore huge economic benefits are generated.

The invention provides a method for identifying whole-spacecraft flexibility vibration modal parameters. The method for identifying the whole-spacecraft flexibility vibration modal parameters comprises the following steps that pose angular speed is obtained, specifically, i-axis pose angular speed data omega' i (t) after filtering is obtained after pose angular speed measuring data omega i (t) corresponding to an i-axis of an underdamping free vibration area after satellite on-orbit air injection closed-loop control, wherein the i-axis is any one of an X-axis, a Y-axis and a Z-axis in a spacerectangular coordinate system; filtering is carried out, specifically, filtering is carried out on the omega i (t) to obtain the i-axis pose angular speed data omega' i (t) after filtering; on-orbit vibration frequency is calculated, specifically, the on-orbit vibration frequency fi is calculated and obtained according to the omega' i (t); time series is calculated, specifically, the time series eta i (t) of a modal variable is calculated and obtained according to the omega' i (t); and damping is calculated, specifically, the damping epsilon i of the i-axis vibration mode is obtained accordingto calculation. The method for identifying the whole-spacecraft flexibility vibration modal parameters meets the requirement of flexible satellite on-orbit structural dynamic characteristic identification, and on-orbit flexibility vibration modal frequency and modal damping ratio and other whole-spacecraft flexibility vibration modal parameters are extracted.

The invention provides a method for identifying whole-satellite flexible vibration modal parameters by utilizing satellite gyroscope data. The whole-satellite flexible vibration modal parameters are identified by utilizing attitude angular velocity data measured by a gyroscope in an under-damping free vibration period after satellite on-orbit air injection control, wherein the whole-satellite flexible vibration modal parameters comprise an on-orbit flexible vibration modal frequency and a modal damping ratio. In the identification process, only gyro measurement data loaded on a satellite platform are used for analysis and processing, and displacement, speed and acceleration vibration sensors installed on flexible accessories are not used. According to the method, only measurement data of an existing inertial attitude sensor of a satellite platform are used for analysis and processing; the increased satellite design and manufacturing difficulty and the risk of on-orbit operation due tothe installation of other vibration sensors are avoided. The identified whole-satellite flexible vibration mode parameters can provide necessary support for application in the aspects of structural design, structural health monitoring, structural fault diagnosis, structural vibration control and the like of space flexible components.

The invention discloses a wind-induced vibration control method for a high-pier long-span bridge during a construction period, and relates to the technical field of civil engineering, and the main points of the technical scheme are that the method comprises the following steps: analyzing and obtaining inherent frequency information of a main beam; establishing an original finite element model; establishing a wind-resistant finite element model; carrying out structural dynamic characteristic complex modal analysis; evaluating and analyzing the complex modal dynamic characteristic result from the structure frequency and the modal damping ratio to obtain a first vibration reduction effect; performing evaluating and analyzing according to the buffeting response calculation result to obtain a second damping effect; verifying the test result of the wind-induced vibration response to obtain verification data; and correcting the elastic modulus of the bridge tower and girder concrete of the original finite element model according to the verification data. According to the method, wind-induced vibration control in the construction period of the main beam is carried out by adopting a wind-resistant measure that the vertical lower inhaul cable is matched with the swing type TMD, the wind-induced vibration response and the wind-induced buffeting load in the construction period of the main beam of a bridge structure can be effectively reduced, and the wind-resistant safety in the construction period of a bridge and the comfort of constructors are improved.

The invention discloses a box-type thin-walled part milling stability prediction method, used for solving the technical problem of lower prediction accuracy of an existing thin-walled part milling stability prediction method. The technical scheme is that the method comprises the steps of firstly using a modal hammer experiment to test a modal parameter of a tool and a modal damping ratio of a workpiece; then using a substructure modal synthesis method to calculate a workpiece dynamic characteristic with considering a material removal effect; afterwards, extracting dynamic displacements of the workpiece at different tool positions and different axial heights; finally establishing a multi-point contact milling dynamical model, substituting the previously obtained workpiece dynamic characteristic into the model, and solving reliability. Changes due to material removal, changes at different tool positions, and changes along the axial direction of the tool of the workpiece dynamic characteristic are considered at the same time, thus improving the prediction accuracy of box-type thin-walled part milling stability.

The invention relates to the field of material testing, and discloses a material parameter testing method and a testing device. The method comprises the following steps of obtaining an inherent frequency test value and a modal damping ratio test value of a to-be-tested sample at a specific temperature t, determining an inherent frequency theoretical value of the to-be-tested sample according to the inherent frequency test value, and determining a modal damping ratio theoretical value of the to-be-tested sample according to the modal damping ratio test value, determining the elasticity modulus, Poisson's ratio and thermal expansion coefficient of the to-be-tested sample according to the inherent frequency theoretical value of the to-be-tested sample, and determining the loss factor of the to-be-tested sample according to the modal damping ratio theoretical value of the to-be-tested sample. The testing method is used for solving the problem that material parameters in a high-temperature environment cannot be effectively obtained in the prior art.