41 results about "Modal strain energy" patented technology

The invention discloses a method and system for identifying damage of a bridge structure. The method comprises the steps of arranging sensors on a target bridge, collecting pulse signals, collecting pulse signals of the target bridge structure under natural excitement with the sensors, obtaining high-precision impulse signals, acquiring incomplete modal parameters, conducting modal identification on the high-precision pulse signals through an improved NExT-ERA method, acquiring high-precision incomplete modal parameters, identifying the damage and establishing change rate indexes and indexes of incomplete modal strain energy, wherein the change rate indexes of the incomplete modal strain energy are used for representing damage positions, and the indexes of the incomplete modal strain energy are used for representing damage degrees. With the method for identifying the damage of the bridge structure, the damage positions and damage degrees of the target bridge structure can be obtained accurately, therefore, sudden disasters are prevented effectively, defect development is controlled timely, losses are cut, casualties are avoided, and the safety of the structure and users is guaranteed.

The invention discloses a structural damage identification method based on ridge estimation and an L curve method. The structural damage identification method comprises the steps of firstly, building a structural damage equation based on sensitivity of modal strain energy according to the sensitivity of the structural modal strain energy, then determining a basic estimation criterion of the ridge estimation according to the principle of Tikhonov regularization, then utilizing the L curve method for determining the optimal ridge parameter of the ridge estimation, working out the basic solution of the structural damage equation on the basis of the optimal ridge parameter, and finally correcting the result, so that the damage coefficient of a damage unit is obtained, and the structural damage is identified. According to the structural damage identification method based on the ridge estimation and the L curve method, by the adoption of the ridge estimation, the influence of an ill-conditioned problem on damage identification can be greatly reduced, the quasi-optimal ridge parameter is determined by the adoption of the L curve method, meanwhile, a correcting strategy for the ridge estimation is provided, and therefore the better damage estimation value is obtained.

The invention provides an integral and local information fusing method of structure health diagnosis based on monitoring information of integral acceleration and local stress sensors, which comprises the steps of: arranging acceleration and stress sensors on a target structure and carrying out vibration test to obtain acceleration and stress stroke response, and recognizing modal parameters of the structure; establishing a finite element model of the structure; and preliminarily determining the damage range by adopting the modal stress energy indexes through an actually measured modal vibration shape. The invention integrates information of the integral acceleration sensor and the local stress sensor for structural health diagnosis, fully utilizes multi-sensor information in the structural health monitoring, a Bayesian probability theory is adopted, considers the uncertainty of actually measured information, and accords with the engineering actual characteristic. The invention can obtain accurate, reliable and stable damage diagnosis results and has stronger noise immunity and robustness.

The invention discloses a multi-objective sensor distributed point optimizing method on the basis of self-adaptive differential evolution. The multi-objective sensor distributed point optimizing method includes steps of (1) setting up a finite element model of a structure to be measured, and utilizing the numerical solution method to obtain the dynamic characteristic data of the structure; extracting a vibration mode matrix of all alternative measuring points and utilizing all measuring points contained in various step vibration modes as the alternative resource of the optimization; (2) selecting more than two of the modal assurance criterion and various optimization criterions based on the modal strain energy and the measuring vibration displacement maximization as an objective function of the multi-objective constraint sensor optimization of the distributed points, wherein the objective function is used for evaluating advantages and disadvantages of clusters and is the basis for self-adaptive differential evolution algorithm operation, and the selecting process of the objective function is a process determining the optimization criterion; (3) solving the problem of the sensor optimization of the distributed points under the multi-objective constraint by means of the self-adaptive differential evolution algorithm.

The invention provides an equivalent modal strain energy damage identification method. The method comprises the following steps of: respectively solving corresponding modal strain energy by using a modal shape generated before and after being damaged; and then judging the damage position and the damage degree of the unit by using an strain energy equivalent index of each damage unit; if an index value is approximate to zero or has a negative value, expressing that no damage exists; and if the index value is a positive value, expressing that the unit has the damage, wherein the damage degree of the unit is the size of the equivalent index value. Compared with the strain energy variation rate method, a strain energy equivalent index method has the advantage of quantitative identification; and compared with the strain energy dissipation rating method, the strain energy equivalent index method has the advantage of higher identification precision.

The nondestructive health detection method for large structure includes the following steps: storage step, identification and location step, damage extent evaluation step and comparison and definition step. Said method can effectively detect the damaged position of said structure and can verify the correctness of the damage-diagnosed result. Said invention also provides the working principle of said detection method.

The invention discloses a constrained damping layer structure vibration calculation method. Through starting from a constrained damping layer damping and noise reducing mechanism, utilizing damping loss factors in statistical energy analysis to reflect damping effects of constrained damping layers, combining a modal strain energy method and considering frequency-dependent shear modulus and material loss factors of frequency of the constrained damping layers, a vibration calculation method for large-scale constrained damping layer structures is established, so that the forecast evaluation and optimized analysis of the constrained damping layers applied to large-scale structure damping and noise reducing are realized. According to the method, the calculation efficiency is remarkably improved and the vibration simulated analysis of the large-scale constrained damping layer structures can be realized; and the frequency-dependent characteristics of material shear modulus and material loss factors of the damping layers are considered so that the precision of simulated analysis is improved. By utilizing the method, optimized analysis can be carried out on laying positions and structure parameters of the constrained damping layers, the damping and noise reducing effects of the constrained damping layers can be forecasted, and the constrained damping layers can be utilized to carry out vibration and noise control on engineering structures.

The invention relates to a damage identification method for a light high-strength beam structure. According to the method, a comprehensive damage index of the structure is obtained based on an added mass frequency sensitivity damage equation and a modal strain energy damage equation, and the damage position and damage degree of the light high-strength beam are identified. The damage index calculated through a modal shape and modal strain energy can accurately express the damage position and damage degree of the light high-strength beam structure, calculated damage parameters are more accurate, and the method of solving the structure damage parameters is more accurate compared with the prior art.

Provided is a hydraulic radial steel gate constrained damping layer vibration reduction design method. The method comprises the following steps that 1, finite element simulation unit selection is conducted on components of all parts of a radial steel gate, a curved panel adopts a shell unit to simulate the stress state, support arms, beams and longitudinal beams adopt a beam unit to simulate the stress state, hanger rods adopt a rod unit to simulate the stress state, and dynamical property analysis is conducted on the radial steel gate; 2, the equivalent mass of water is calculated by adopting a Westergaard method, and the dynamic property influence of water pressure on the radial steel gate is simulated; 3, structural mode strain energy analysis is conducted on the radial steel gate, it is obtained through analysis that the value of radial steel gate support arm mode strain energy is the maximum value, and by means of a constrained damping layer arranged on the support arm structure of the radial steel gate, a flow-induced load effect of the radial steel gate can be reduced. According to the hydraulic steel radial gate constrained damping layer vibration reduction design method, structural damping of the radial steel gate is increased, and a flow-induced load vibration effect is reduced.

A multi-tuned mass damper vibration absorption design method for an arc-shaped steel gate comprises the following steps that 1, a finite element method is adopted for carrying out dynamic characteristic and power response analysis on the arc-shaped steel gate; 2, the influence of water pressure on the dynamic characteristic of the arc-shaped steel gate is simulated; 3, modal strain energy analysis is carried out on the arc-shaped steel gate to determine the optimal mounting position of an MTMD; 4, a multi-tuned mass damper is mounted on a branch arm of the arc-shaped steel gate; 5, according to the actual stress condition of the arc-shaped steel gate, the number of single-tuned mass dampers in the multi-tuned mass damper, the frequency distribution range of the multi-tuned mass damper and the damping rate of the multi-tuned mass damper are determined through optimization. The multi-tuned mass damper is arranged on the branch arm of the arc-shaped steel gate, the flow induced vibration response of the branch arm and even the whole structure can be effectively reduced under the condition that parameters of the multi-tuned mass damper are reasonable, and the aim of protecting the main structure is achieved.

The invention relates to a safety assessment method for a heavy load structure of a heavy type construction machine. The safety assessment method includes the concrete steps that modal shape vectors and stiffness matrixes are used for determining corresponding structural element modal strain energy and corresponding overall structure modal strain energy, wherein the modal shape vectors and the stiffness matrixes are generated before and after structural damage; element modal strain energy ratios before and after structural damage is determined by adopting the ratio of the element modal strain energy to the overall structure modal strain energy; the strain energy damage tolerance ratio degree DESR ij is determined through the ratio of element modal strain energy before structural damage to element modal strain energy after structural damage. When the modal strain energy damage tolerance ratio degree DESR ij approaches zero, it shows that the j element is not damaged, and the larger the modal strain energy damage tolerance ratio degree DESR ij is, the more serious the damage of the j element is damaged. According to the method, the modal strain energy damage tolerance ratio degrees of all the elements are sequentially calculated so that the positions and the degrees of structural damage can be obtained. Existence of structural damage of the heavy load structure of the heavy type construction machine and the positions of structural damage can be fast and accurately recognized, and the problem that structural damage of the heavy load structure of the heavy type construction machine is not prone to being recognized is solved.

The invention relates to a topological optimization design method for a constrained damping sheet structure. The method comprises the following steps: taking reciprocal minimization of a modal loss factor as an optimization design target, wherein the relative density of the constrained damping layer unit is used as a design variable and the usage amount of the constraint damping layer is a constraint condition; establishing a dynamic topological optimization model through a variable density method; establishing a finite element dynamic model through a laminated plate theory; obtaining the inherent frequency and the modal shape of the composite structure through modal analysis; and calculating a modal loss factor of the constrained damping structure based on a modal strain energy method, calculating the sensitivity of the target function to each design variable according to a sensitivity formula, filtering the sensitivity through a grid filtering technology, iterating the design variables by adopting a moving asymptotic line method, and outputting an optimal topological configuration when a termination condition is met. The optimal topological distribution of the constraint dampinglayer on the surface of the substrate is realized on the premise of adding a certain amount of constraint damping material, the vibration response is effectively reduced, and the material is saved.

The invention relates to a method for determining the bonding position of a loss factor frequency-dependent unconstrained damping layer on a white car body and belongs to the vehicle engineering technical field. According to an existing method, the frequency dependence of a damping material when the bonding position of an unconstrained damping layer on a white car body structure is not considered, and a proper unconstrained damping layer material cannot be selected out in the characteristic frequency range of the vibration of a car body plate, and the damping vibration reduction efficiency of the unconstrained damping layer material cannot be utilized maximally, while, with the method of the invention adopted, the above problems can be solved. According to the method, finite element modeling and modal analysis are performed on a car body structure, so that the magnitude and distribution of modal strain energy at each order of the car body structure are obtained, and the strain energy is superposed, so that the comprehensive modal strain energy of the car body structure can be obtained, and positions where the comprehensive modal strain energy is higher than a threshold value are extracted and are subjected to damping treatment, and the sum of modal strain energy of various units of various plates of the car body is calculated, wherein the various units of the various plates of the car body are subjected to unconstrained damping layer treatment under modal frequency at each order in the frequency range of damping vibration reduction, and a loss factor frequency-dependent unconstrained damping layer material can be selected, so that an optimal vibration reduction effect can be realized.

The invention relates to a modal strain energy-based damage occurrence judging method. The method comprises the following steps of: establishing a finite element model for an analysis object; carrying out repeated modal tests on the analysis object, wherein each test can obtain the first five-order modal shapes of the analysis object; obtaining a local rigidity matrix of each unit on the basis of a finite element solver; filling the local rigidity matrix of each unit into a total rigidity matrix to obtain a rigidity contribution value of each unit; respectively solving modal strain energy of each unit in each test; carrying out similarity calculation on a modal strain energy vector obtain in each test and a modal strain energy vector obtained for the first time according to the sequence of the tests, and adding the similarity of each unit. The method is used for judging whether damage occurs or not.

The invention discloses a method for improving the low-frequency vibration performance of a complex structure. Firstly, a test modal analysis method is adopted to obtain a test modal and vibration frequency response function of the automobile structure, and the test system comprises a vibration exciter, a test system, a test computer, a three-way acceleration sensor and the like. Then, a finite element analysis model of the vehicle body structure is built through a finite element modeling technology, the accuracy and reliability of the model are determined through modal benchmarking analysis,and the modal and vibration frequency response function of the finite element model is calculated. For the frequency with abnormal vibration frequency response function peak value, sensitivity analysis based on the plate thickness is carried out, and the plate with the local rigidity not matched with the overall rigidity of the vehicle body design is found. According to the concentrated distribution area of the modal strain energy on the plate under the frequency, a structure optimization method is adopted, so that the problem frequency vibration peak amplitude is greatly reduced, a good effect is obtained, the product performance is improved, the research and development and manufacturing period is shortened, and the cost is reduced.

The invention discloses a structural damage identification method based on modal strain energy and convolution neural network, comprising the following steps: S1, constructing a structural model through software simulation, and dividing a unit according to the structural model; S2: simulating several kinds of structural damage in different elements of the structural model; S3, extracting the first-order modal strain energy of the structure under the condition of free vibration, and converting the obtained data into matrix data form as the input of the convolution neural network; 4, training the convolution neural network; 5, carrying out actual measurement on that structure, and calculating the modal strain energy of different element in different order modes according to the element division mode of S1; S6: the data matrix of the modal vector of S5 being substituted into the trained convolution neural network of S4 to obtain the damage result of the structure. The invention improves the accuracy of damage identification, reduces the interference unit, and can identify the damage degree, and the damage degree can not be identified only by using the modal strain energy.

The invention discloses a method for improving the inherent vibration frequency of a mechanical structure. The method comprises the following steps of according to the method, subjecting a mechanicalstructure to a vibration mode test; establishing a finite element model and optimizing the rigidity of a connection part, carrying out modal analysis on the finite element model, confirming a relatively large strain energy position of the mechanical structure through topology optimization, DOE test design and modal strain energy analysis, and improving the inherent vibration frequency of the mechanical structure by arranging a beam unit and verifying the inherent vibration frequency of the mechanical structure. According to the method, test testing and theoretical simulation are combined, thestructural rigidity and the main position influencing the inherent vibration frequency of the mechanical structure are determined by carrying out vibration mode testing and size optimization on the mechanical structure, and the beam unit is additionally arranged, so that the effective improvement of the inherent vibration frequency is verified.

The invention relates to a local constraint damping plate vibration suppression analysis method, which comprises the following steps of: obtaining an area with dense modal strain energy distribution of a thin plate as a target area through finite element modal analysis, and determining a central position of initial distribution of constraint damping plates; describing geometric information of theconstrained damping plate through an explicit geometric description function; performing grid division on the constrained damping plate structure; establishing a stiffness matrix and a mass matrix ofthe entity constraint damping unit, and obtaining the stiffness matrix and the mass matrix of the composite unit cut by the constraint damping fin boundary; assembling the stiffness matrix and the mass matrix of each composite unit to obtain an integral stiffness matrix and an integral mass matrix, and establishing a finite element dynamic model of the constrained damping plate to obtain a modal loss factor of the constrained damping plate. Parameter analysis and optimization of the local constraint damping thin plate structure can be achieved, and grid redivision is not needed during parameter analysis and optimization; the method is simple in principle, easy to implement and high in application value.

The invention discloses a damping optimization design method, for constraining a damping drum, based on the modal strain energy method and solves the problem that the vibration stress of an aero engine drum is excessively large. The method includes adhering constraining damping material onto the inner wall of the aero engine drum, constructing a constraining damping drum, establishing a finite element model of the constraining damping drum, and performing modal analysis; determining the usage of the constraining damping material and the concerned modal, extracting the modal strain energy distribution of the damping layer, and determining the arranging position of the constraining damping material according to the usage of the constraining damping material and the strain energy distribution of the damping layer. The arranging position of the constraining damping material is trimmed annularly for the convenience of project implementation. According to the method, on the condition of setting the certain constraining damping material usage additionally, the arranging position of the constraining damping material can be determined rapidly, and the fine damping effect of the constraining damping drum can be achieved.

The invention discloses a structure damage degree identification method based on a convolutional neural network. The structure damage degree identification method comprises the following steps: S1, constructing a simply-supported beam structure, collecting training sample data according to the simply-supported beam structure, wherein the simply-supported beam structure comprises N units, and each unit has different modal strain energy, and the training sample data comprise the modal strain energy of each unit; S2, constructing an input matrix according to the modal strain energy of each unit; S3, constructing a model of the convolutional neural network according to the input matrix; S4, training the convolutional neural network by using the training sample data comprising the modal strain energy of each unit, and storing the trained convolutional neural network; and S5, predicting unknown simply supported beam structure damage by using the trained convolutional neural network. According to the structure damage degree identification method, a convolutional neural network weight sharing method is utilized, so that calculation parameters are reduced, and the calculation speed is high, and positive significance is achieved for application of a large-scale structure.

The invention belongs to the technical field of aero-engine fault diagnosis, and relates to an aero-engine blade damage online identification method. Comprising the following steps: establishing a damage-free blade finite element model, and calculating modal frequency and vibration mode of each order; establishing a non-damage blade test model, and identifying test modal frequency and vibration mode; taking the previous 10-order test modal frequency as a target value, taking the blade material parameter as a variable, correcting the blade finite element model, obtaining an accurate finite element model, and calculating a stiffness matrix of each element, where the unit stiffness matrix is assembled into an overall vibration mode stiffness matrix; measuring blade vibration parameters in a working state; reading vibration parameters and rotating speed parameters in real time through an online monitoring system, correcting the finite element model to complete damage positioning, calculating the modal strain energy change rate to complete damage evaluation, and displaying an alarm when the damage amount exceeds the limit. The blade damage position and the damage degree can be determined online to complete feedback, serious faults are prevented, the repair cost is reduced, and the flight safety is guaranteed.

The invention discloses a load-bearing structural member damage identification method and system based on a strain mode. The method comprises the following steps: constructing a finite element model before and after damage of a to-be-analyzed load-bearing structural member; carrying out multiple modal tests on the to-be-analyzed bearing structural member to obtain a strain modal after damage; performing modal analysis solution on the pre-damage finite element model to obtain a pre-damage overall stiffness matrix, an overall mass matrix, a pre-damage strain modal and an inherent frequency; solving the damaged finite element model to obtain a damaged overall stiffness matrix; obtaining modal strain energy before damage based on the integral stiffness matrix and the strain modal before damage; based on the post-damage overall stiffness matrix and the post-damage strain mode, obtaining post-damage modal strain energy; based on the inherent frequency, the overall mass matrix, the modal strain energy before and after damage and the element stiffness reduction coefficient, obtaining damage identification of the modal strain energy sensitivity; and solving the modal strain energy sensitivity structure damage equation based on the strain modal to obtain an identification result.

The invention relates to a passive vibration reduction method of a space science experiment cabinet, which comprises the following steps of establishing a finite element simulation model of the spacescience experiment cabinet in pretreatment software, and carrying out sine sweep frequency analysis and solution to obtain acceleration response results of the whole and each component; obtaining theenergy distribution of the whole cabinet and each component on a resonant frequency point; laying a constraint damping layer at the position with large modal strain energy of the key assembly; and carrying out the sinusoidal sweep frequency analysis solution on the space science experiment cabinet after the damping vibration attenuation is laid, compairing the change conditions of structure responses before and after the additional constraint damping layer, and verifying the reliability of the passive vibration attenuation method. According to the passive vibration reduction method for the space science experiment cabinet, the existing structure does not need to be changed, the structural function of the cabinet body is not affected, the dynamic environment of instruments, equipment and effective loads is improved to a certain extent, the comprehensive performance index of the experiment cabinet is improved, and the method is high in reliability and high in robustness and is easy to achieve.

The embodiment of the invention discloses a sensor measuring point position determination method and device. The method comprises the steps of acquiring a strain modal matrix of a multi-order modal; determining a Fischer information matrix according to the strain modal matrix; calculating a value of a determinant of the Fischer information matrix; and when the value of the determinant of the Fischer information matrix is determined to be the maximum value, indicating that the position of the target node identified in each order of modality in the multi-order modalities is the measuring point position of the sensor, wherein the target node is the node with the maximum modal strain energy in the plurality of nodes included in the order of modalities. Thus, when the value of the determinant of the Fischer information matrix is determined to be the maximum value, the position of the target node identified in each order of modality in the multi-order modalities is the measuring point position of the sensor, and redundancy of sensor configuration is avoided.

The invention discloses a gear box additional damping noise reduction method based on modal strain energy, which comprises the following steps: S1, establishing a gear box model, and carrying out modal analysis; S2, calculating a modal damping ratio of each order modal of the gearbox; S3, constructing a gear box boundary element model and a Box sound field, and calculating an acoustic transmissionvector; S4, performing vibration response calculation; S5, obtaining the relationship between the vibration speed and the sound pressure of the field points, superposing the sound pressure level caused by each node of the gearbox to each corresponding field point, and solving the radiation noise of the field points; S6, adding damping to the area corresponding to the field point with the maximumsound pressure level on the gear box, establishing an additional damping gear box model, and solving the radiation noise; and S7, performing noise reduction after additional damping, the scheme is determined to be a gearbox model with additional damping, noise reduction is not carried out after additional damping, and the step S6 is executed again to change the scheme with additional damping. Themethod is good in noise reduction effect on the gear box, good in practicability and worthy of popularization.