CN118278225B - Material vibration S-N characteristic identification method and device based on structural vibration test - Google Patents
Material vibration S-N characteristic identification method and device based on structural vibration test Download PDFInfo
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Abstract
The invention discloses a material vibration S-N characteristic identification method and device based on a structural vibration test, relates to the field of engineering structure vibration, and is used for solving the problems that local strain response is difficult to quantitatively characterize and characteristic data universality is poor when the material vibration S-N characteristic is identified by a test method. Comprising the following steps: developing a structural vibration fatigue test of the target structure to obtain experimental result data; establishing an experimental structure dynamics model, adopting the model to carry out simulation on a vibration test, and identifying fatigue dangerous parts of the test structure under a vibration load to obtain structural stress characteristics; analyzing the structural vibration life based on the structural stress characteristics to obtain the structural vibration fatigue life; and simulating vibration stress aiming at each vibration level in different load levels, and comparing simulated vibration life data and experimental result data under each level to determine the vibration S-N characteristics of the material.
Description
Technical Field
The invention relates to the field of engineering structure vibration, in particular to a material vibration S-N characteristic identification method and device based on a structure vibration test.
Background
The stress-life curve of the material, namely the S-N curve, is the basis for evaluating the high cycle fatigue life of the structure in the service environment. For static fatigue, a material S-N curve test obtaining method based on standard samples such as test bars and test pieces and typical fatigue test devices such as a pulling and pressing fatigue machine and a rotating fatigue machine is formed, and corresponding standard specifications are formed. For vibration fatigue, the failure mode is similar to that of traditional quasi-static fatigue, and is expressed as follows: the stress and strain levels of the local parts are higher, under the action of cyclic load generated by vibration, accumulated damage is generated to cause the structure to initiate fatigue cracks, and the fatigue cracks continuously expand to finally cause the structure to crack, so that the structural vibration fatigue life assessment is also based on the S-N characteristic parameters of the material. Note that there is also a clear difference between vibration fatigue and static fatigue, mainly: 1) there is a significant difference between random vibration load and static periodic load, 2) the dangerous site vibration strain response is difficult to characterize with quantifiable and structurally independent nominal quantities, and 3) the volumetric effect of vibration fatigue is more pronounced due to stress concentration of the local vibration response superimposed structure itself. Therefore, the characteristic parameters of the material S-N in the vibration environment have a certain difference from those of the material S-N under static load, and the difficulty of obtaining the vibration S-N data of the material through the standard sample by referring to the traditional quasi-static fatigue method is high.
The vibration test of the design of the simulation test piece reserved through the characteristic structure and the equivalent reproduction of the load can realize the effective evaluation of the structural vibration fatigue life on the vibration test bed, and the life rule can be popularized and applied in the structure with the same specification. However, the simulation test piece is closely related to the corresponding structure and stress concentration form, and the structural life rule obtained by the test is difficult to popularize and apply to vibration fatigue life evaluation of other different specifications and different types of structures, and the universality is far lower than that of the material fatigue S-N characteristic parameters. Therefore, how to obtain the material vibration S-N characteristic parameters in a universal, simple and standard test mode becomes an engineering difficult problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a material vibration S-N characteristic identification method and device based on a structural vibration test, which are used for solving the problems that local strain response is difficult to quantitatively characterize and characteristic data universality is poor when the material vibration S-N characteristic is identified by a test method in the prior art.
In order to achieve the above object, the present invention provides the following technical solutions:
In a first aspect, the present invention provides a method for identifying S-N characteristics of vibration of a material based on a structural vibration test, the method comprising:
Developing a structural vibration fatigue test of the target structure to obtain experimental result data; the experimental result data at least comprises structural vibration frequency characteristics, strain response and vibration fatigue life data under different load orders;
Establishing an experimental structure dynamics model based on the experimental result data, performing simulation on a vibration test by adopting the experimental structure dynamics model, identifying fatigue dangerous parts of the experimental structure under a vibration load, and obtaining structural stress characteristics; the structural stress characteristics at least comprise stress power spectral density and volume distribution of dangerous parts;
analyzing the structural vibration life based on the structural stress characteristics to obtain the structural vibration fatigue life;
simulating vibration stress aiming at each vibration level in different load levels, and repeatedly sampling the vibration fatigue life of the structure to obtain simulated vibration life data under each level;
and comparing the simulated vibration life data with the experimental result data under each magnitude to determine the vibration S-N characteristics of the material.
Compared with the prior art, the material vibration S-N characteristic identification method based on the structure vibration test obtains experimental result data by developing the structure vibration fatigue test of the target structure; establishing an experimental structure dynamics model based on experimental result data, performing simulation on a vibration test by adopting the model, and identifying fatigue dangerous parts of the experimental structure under a vibration load to obtain structural stress characteristics; analyzing the structural vibration life based on the structural stress characteristics to obtain the structural vibration fatigue life; simulating vibration stress aiming at each vibration level in different load levels, and repeatedly sampling structural vibration fatigue life to obtain simulated vibration life data under each level; and comparing the simulated vibration life data with experimental result data under various orders to determine the vibration S-N characteristics of the material. In the invention, the influence of stress characteristics and material vibration S-N characteristics on the structural vibration life is separated, and modeling description is carried out, so that the structural vibration fatigue life model is established. Therefore, the material vibration S-N curve parameters are obtained through structural vibration simulation life data and test life data comparison optimization. The structural vibration life analysis is carried out based on the stress power spectral density and the volume distribution of dangerous parts in the structural stress characteristics, the normal stress state of each small volume can be ensured, the problem that the local strain response is difficult to be represented in an equivalent way due to the stress concentration in the prior art is solved, in addition, the difficulty of obtaining the vibration S-N data of the material by the standard sample in the traditional quasi-static fatigue method in the prior art is high, and the method provided by the invention can realize quantitative characterization of local strain response aiming at vibration load, so that accurate and universal material S-N performance data is provided for structural vibration fatigue analysis.
In a second aspect, the present invention provides a material vibration S-N characteristic identification apparatus based on a structural vibration test, the apparatus comprising:
The structure vibration fatigue test module is used for carrying out a structure vibration fatigue test of the target structure to obtain experimental result data; the experimental result data at least comprises structural vibration frequency characteristics, strain response and vibration fatigue life data under different load orders;
the structural stress feature determining module is used for establishing an experimental structural dynamics model based on the experimental result data, carrying out simulation on a vibration test by adopting the experimental structural dynamics model, identifying fatigue dangerous parts of the test structure under the vibration load and obtaining structural stress features; the structural stress characteristics at least comprise stress power spectral density and volume distribution of dangerous parts;
the structural vibration fatigue life determining module is used for analyzing the structural vibration life based on the structural stress characteristics to obtain the structural vibration fatigue life;
The vibration stress simulation module is used for simulating vibration stress aiming at each vibration magnitude in different load magnitudes, and repeatedly sampling the vibration fatigue life of the structure to obtain simulated vibration life data under each magnitude;
and the material vibration S-N characteristic identification module is used for comparing the simulated vibration life data with the experimental result data under various orders to determine the material vibration S-N characteristic.
The technical effects achieved by the apparatus type scheme provided in the second aspect are the same as those of the method type scheme provided in the first aspect, and are not described herein.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:
FIG. 1 is a schematic flow chart of a method for identifying S-N characteristics of material vibration based on a structural vibration test;
FIG. 2 is an overall flow chart of the solution provided by the present invention;
FIG. 3 is a schematic diagram of an exemplary reference structure;
FIG. 4 is a schematic diagram of vibration stress volume distribution at a dangerous portion of a test structure;
FIG. 5 is a schematic diagram of 100 times of vibration life data of each vibration magnitude sampling simulation of a test structure;
FIG. 6 is a schematic diagram showing the comparison of the similarity between the optimized simulated life data and the test data;
FIG. 7 is a graph of S-N vibration of a material identified using the method provided by the present invention;
fig. 8 is a schematic structural diagram of a material vibration S-N characteristic recognition device based on a structural vibration test according to the present invention.
Detailed Description
In order to clearly describe the technical solution of the embodiments of the present invention, in the embodiments of the present invention, the words "first", "second", etc. are used to distinguish the same item or similar items having substantially the same function and effect. For example, the first threshold and the second threshold are merely for distinguishing between different thresholds, and are not limited in order. It will be appreciated by those of skill in the art that the words "first," "second," and the like do not limit the amount and order of execution, and that the words "first," "second," and the like do not necessarily differ.
In the present invention, the words "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.
In the present invention, "at least one" means one or more, and "a plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a alone, a and B together, and B alone, wherein a, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (one) of a, b or c may represent: a, b, c, a and b, a and c, b and c, or a, b and c, wherein a, b, c can be single or multiple.
In the prior art, vibration S-N test load is difficult to apply, local strain response is difficult to quantitatively characterize, and characteristic data universality is poor. In order to solve the technical problem, the invention identifies the vibration S-N characteristic parameters of the material based on the structural vibration fatigue test and the service life rule.
Next, the scheme provided by the embodiments of the present specification will be described with reference to the accompanying drawings:
the structural object of this embodiment is shown in fig. 3, and mainly comprises an examination part, an upper connecting part and a lower connecting part. For this structure, the corresponding method flow is shown in fig. 1, and the flow for obtaining the material vibration S-N characteristic parameter thereof may include the following steps:
Step 110: developing a structural vibration fatigue test of the target structure to obtain experimental result data; the experimental result data at least comprises structural vibration frequency characteristics, strain response and vibration fatigue life data under different load orders.
The target structure may be an actual structure or an analog structure. When an experiment is carried out, the test structure is fixedly arranged on the vibrating table, the acceleration sensor is stuck at the upper connecting part, the strain gauge is stuck at the checking part, and the acceleration control sensor is stuck at the lower connecting part. And applying 4-magnitude vibration load to the test structure by using the vibration table, and carrying out vibration fatigue test on the structure or the simulated structure thereof to obtain first-order natural frequency of the structure, strain measuring point response of the checking part and vibration fatigue life data under different load magnitudes.
Step 120: establishing an experimental structure dynamics model based on the experimental result data, performing simulation on a vibration test by adopting the experimental structure dynamics model, identifying fatigue dangerous parts of the experimental structure under a vibration load, and obtaining structural stress characteristics; the structural stress features include at least a stress power spectral density and a volume distribution of the hazardous location.
In step 120, the method is divided into two parts, wherein the first part is structural dynamics modeling and calibration, and the second part is vibration stress simulation.
Aiming at structural dynamics modeling and calibration, a test structural dynamics model can be established for modal analysis and random vibration analysis when the structural dynamics modeling and calibration are realized; based on the simulation of modal analysis, the elastic modulus and the strain response data of the dynamic model are calibrated based on the frequency characteristic parameter obtained in the step 110, so that the first-order natural frequency of the simulation is the same as that of the test measurement. Based on the method, the damping of the dynamic model is calibrated by combining the analysis of random vibration, so that the dynamic strain simulated at the same position is the same as that of the test measurement.
For vibration stress simulation, the vibration test in step 110 is simulated by using the test structure dynamic model in step 120, fatigue dangerous parts of the test structure under vibration load are identified, and stress power spectral density and volume distribution of the dangerous parts are obtained.
Step 130: and analyzing the structural vibration life based on the structural stress characteristics to obtain the structural vibration fatigue life.
And simulating the vibration fatigue life of the test structure by using the simulation stress result in the step 120. Firstly, selecting an S-N characteristic description equation of a material, wherein the S-N characteristic description equation comprises a deterministic life equation and a life dispersion description equation under a given stress level; then, subdividing the dangerous part in the step 120 according to a certain characteristic volume, and obtaining the stress power spectrum density of each characteristic volume by using the stress data in the step 120; then, selecting a proper frequency domain life assessment model, and calculating the vibration life of each volume on the basis of a material S-N equation and the stress power spectral density of each characteristic volume; and finally, counting and identifying the minimum value of the vibration life in each volume as the structural vibration fatigue life.
Step 140: and simulating vibration stress aiming at each vibration level in different load levels, and repeatedly sampling the vibration fatigue life of the structure to obtain simulated vibration life data under each level.
In step 120, when the stress power spectral density and the vibration stress volume distribution of the dangerous portion are obtained, the fatigue dangerous portion of the test structure under the vibration load can be specifically identified as the chamfer of the middle part of the checking portion, and the stress power spectral density and the vibration stress volume distribution of the dangerous portion are obtained, wherein the dangerous portion and the vibration stress volume distribution thereof are shown in fig. 4.
Step 150: and comparing the simulated vibration life data with the experimental result data under each magnitude to determine the vibration S-N characteristics of the material.
The method in FIG. 1 obtains experimental result data by developing a structural vibration fatigue test of a target structure; establishing an experimental structure dynamics model based on experimental result data, performing simulation on a vibration test by adopting the model, and identifying fatigue dangerous parts of the experimental structure under a vibration load to obtain structural stress characteristics; analyzing the structural vibration life based on the structural stress characteristics to obtain the structural vibration fatigue life; simulating vibration stress aiming at each vibration level in different load levels, and repeatedly sampling structural vibration fatigue life to obtain simulated vibration life data under each level; and comparing the simulated vibration life data with experimental result data under various orders to determine the vibration S-N characteristics of the material. The method provided by the invention can be used for carrying out structural vibration life analysis based on the stress power spectral density and the volume distribution of dangerous parts in structural stress characteristics, can ensure the normal stress state of each small volume, solves the problem that the local strain response is difficult to be represented in an equivalent way due to stress concentration in the prior art, and has higher difficulty in obtaining the vibration S-N data of the material through a standard sample by the traditional quasi-static fatigue method in the prior art.
More specifically, the overall flow chart of the technical scheme provided by the invention is shown in fig. 2:
Firstly, performing a structural vibration fatigue test to obtain frequency and strain response; and carrying out structural dynamics modeling and calibration based on frequency and strain response, then adopting a constructed model to carry out vibration stress analysis, simulating to obtain structural stress characteristics, adopting a material vibration fatigue model to carry out structural vibration life analysis based on the structural stress characteristics, obtaining simulation life data, and carrying out vibration fatigue parameter calibration based on the simulation life data and experimental life data obtained in a vibration fatigue experiment to obtain material vibration fatigue parameters.
Based on the method of fig. 1, the examples of the present specification also provide some specific implementations of the method, as described below.
Optionally, step 130 may specifically include:
Selecting an S-N characteristic description equation of the material; the S-N characteristic description equation comprises a deterministic life equation and a life dispersion description equation under a given stress level;
subdividing the dangerous part according to a certain characteristic volume, and determining the stress power spectral density of each characteristic volume;
and selecting a corresponding frequency domain life assessment model, calculating the vibration life of each characteristic volume based on the S-N characteristic description equation and the stress power spectral density of each characteristic volume, and determining the minimum value in the vibration life of each characteristic volume as the structural vibration fatigue life.
The S-N characteristic describing equation represents the stress and fatigue life unique function relation of the material; the deterministic life rule is generally described in two-parameter and three-parameter forms, as in equation (1):
（1）
In the formula (1): As a function of the lifetime of the device, In the form of a logarithm of the lifetime,Parameters are described for deterministic life laws. The lifetime dispersion is typically described by a lognormal distribution, and thus the S-N characterization equation can be further described as equation (2):
（2）
Wherein, As a function of the lifetime of the device,In the form of a logarithm of the lifetime,The parameters are described for a deterministic life rule,As a result of the life-span dispersion coefficient,For a standard normal distribution, S represents stress and N is vibration lifetime.
Wherein, the characteristic volume refers to the minimum volume corresponding to the initiation of structural cracks, and in the volume, the cracks independently initiate and finally propagate to cause structural fracture. Thus, each characteristic volumetric vibration lifetime can be independently assessed and considered for the effect of the dispersion of the S-N characteristics of the localized material. Meanwhile, the structural dangerous volume can be considered to be formed by serially connecting characteristic volumes in the dangerous volume, and the structural vibration life is determined by the minimum value in the life of each characteristic volume.
The frequency domain life assessment model refers to a model for calculating vibration life through stress power spectrum density based on the S-N equation of the material, such as Bimodal model, dirlik model and the like.
Optionally, for each vibration magnitude in different load magnitudes, performing vibration stress simulation, and repeatedly sampling the structural vibration fatigue life to obtain simulated vibration life data under each magnitude, which specifically may include:
Under each vibration level in different load levels, carrying out random assignment on life dispersion parameters in the S-N characteristic description equation of each characteristic volume to obtain vibration life; repeating for a plurality of times to obtain simulated vibration life data under various orders.
Optionally, comparing the simulated vibration life data with the experimental result data under each magnitude to determine the material vibration S-N characteristic may specifically include:
Comparing the simulated vibration life data under each level with the experimental vibration life data of each level in the experimental result data; the simulated vibration life data of each magnitude covers the experimental vibration life data of each magnitude in the experimental result data, and under the condition that each magnitude meets the preset evaluation standard, the S-N characteristic description equation of the identification material is optimized.
Optionally, before optimizing the S-N characteristic description equation of the identification material under the condition that each magnitude meets the preset evaluation criterion, the method further comprises:
fitting the simulated vibration life data of each magnitude by using known distribution to obtain a distribution density function:
；
Wherein, For the life of the vibration,Is a distribution parameter;
using the distribution density function, a function is evaluated according to the likelihood degree, as in formula (4):
（4）
evaluating the approximation degree of the same-magnitude test life data and the simulation life data; wherein, In order to test the vibration life dispersion data,The ith trial representing the current magnitude,Representing the repetition number of the current magnitude test;
Evaluating and obtaining the approximation degree of the discrete data of each level of test and simulation vibration life by using the likelihood degree evaluation function;
and carrying out joint multiplication on the approximation degree calculated by each magnitude to obtain an overall approximation degree evaluation index.
Further, under the condition that all orders meet the preset evaluation standard, optimizing the S-N characteristic description equation of the identification material can specifically comprise:
taking the material S-N curve parameter in the S-N characteristic description equation as a design parameter, and determining the maximum value in the overall approximation degree evaluation index as an optimization target;
And optimizing and identifying the S-N curve parameters of the material based on the design parameters and the optimization targets.
Based on the design parameters and the optimization targets, after optimizing the S-N curve parameters of the identification material, the method may further include:
drawing a material S-N curve according to the optimized material S-N curve parameters;
and identifying the vibration S-N characteristic of the material based on experimental result data of the material S-N curve combined structure vibration fatigue test.
More specifically, when the life of vibration is simulated: and simulating the vibration fatigue life of the test structure by using the simulation stress result. First, the S-N characteristic description equation of the material is selected, and in this embodiment, a three-parameter S-N equation is selected, as in equation (5):
（5）
In formula (5): 、、 the method comprises the steps of taking the static fatigue corresponding parameters of the same material as the fatigue characteristic parameters of the material during initial analysis; next, a characteristic volume is selected Subdividing the dangerous part, and obtaining the vibration stress of each characteristic volume and the power spectrum density thereof by using stress data; then, an appropriate frequency domain lifetime assessment model is selected, and Dirlik models are selected in this embodiment, as in equation (6):
（6）
In formula (6): And Respectively the 2 nd order moment and the 4 th moment of the stress power spectrum density,Probability density function of stress amplitude; therefore, on the basis of a material S-N equation and the stress power spectral density of each characteristic volume, calculating the vibration life of each volume; and finally, counting and identifying the minimum value of the vibration life in each volume as the structural vibration fatigue life.
In addition, when sampling the simulated vibration life, the vibration stress is simulated for the 4 vibration orders in the step 110, and on the basis of the simulation, the obtained vibration life is repeatedly sampled, and 100 times of corresponding vibration life data of sampling simulation under each order are obtained, as shown in fig. 5.
Optionally, when the material S-N equation parameter optimization identification is performed, comparing the simulated vibration life data of each level with the test vibration life data of each level obtained in step 110, specifically including the following steps:
a. fitting the simulated vibration life data of each level by using known distribution to obtain a distribution density function and a distribution parameter;
b. Evaluating the approximation degree of the life data of the same-magnitude test and the simulation life data according to the likelihood degree by using the distribution density function a;
c. and (3) evaluating and obtaining the approximation degree of the discrete data of each level test and the simulated vibration life by using the likelihood degree evaluation function of the formula (4), and then obtaining the overall approximation degree evaluation index by means of joint multiplication.
Table 1 shows the approximate evaluation results of the simulated vibration life data of each magnitude and the experimental vibration life data of each magnitude under the static fatigue parameters of the materials, wherein,Is the reference load.
TABLE 1 structural simulation and test vibration Life similarity evaluation under static fatigue parameters of materials
As can be seen from table 1, the simulation distribution has a low similarity to the test lifetime. The material S-N curve parameters are used as design parameters, the maximum value of the total approximation degree evaluation index is an optimization target, the material S-N curve parameters are identified by a typical optimization method, and the comparison between simulation life data and tests of each level is shown in figure 6. It can be seen that after optimizing the parameters, the distribution of the simulated vibration life data at each level may cover the data obtained by the experiment in step 110, and the similarity is the greatest in the selectable parameter range.
Table 2 gives the static S-N curve parameters of the material and the optimally identified S-N curve parameters of the vibration of the material, wherein,Is a reference life,Is the reference stress.
TABLE 2 vibration S-N Curve parameters for materials
When the material S-N curve is drawn, the material S-N curve can be drawn according to the optimized material S-N curve parameters, as shown in figure 7, and the material S-N curve can be used subsequently.
According to the technical scheme provided by the embodiment of the specification, the stress characteristics and the influence of the material vibration S-N characteristics on the structural vibration life are separated based on the material vibration S-N characteristic identification method of the structural vibration test, and the structural vibration fatigue life model is established through modeling description. Therefore, the material vibration S-N curve parameters are obtained through structural vibration simulation life data and test life data comparison optimization. The invention can be seen through structural vibration fatigue test, structural dynamics modeling and calibration, vibration stress simulation, vibration life simulation, simulated vibration life sampling, material S-N equation parameter optimization and identification, S-N curve drawing and the like. The material vibration S-N characteristic is directly obtained by means of the structure or the vibration fatigue test of the simulation test piece, and the material vibration S-N characteristic is simple in design, strong in operability and easy to realize. The invention solves the technical problems that the vibration S-N test load is difficult to apply, the local strain response is difficult to be characterized in an equivalent way, and the characteristic data universality is poor, and provides a test and identification method for obtaining the more universal and universal material vibration S-N characteristic for researchers. The method can be widely applied to general vibration fatigue performance tests in the field of complex mechanical structures including liquid rocket engines, provides accurate and general material S-N performance data for structural vibration fatigue analysis, and has strong practicability and considerable economic benefit.
Based on the same thought, the invention also provides a material vibration S-N characteristic identification device based on a structural vibration test, as shown in fig. 8, the device can comprise:
The structure vibration fatigue test module 810 is used for carrying out a structure vibration fatigue test of the target structure to obtain experimental result data; the experimental result data at least comprises structural vibration frequency characteristics, strain response and vibration fatigue life data under different load orders;
The structural stress feature determining module 820 is configured to establish an experimental structural dynamics model based on the experimental result data, and perform simulation on a vibration test by using the experimental structural dynamics model, identify a fatigue dangerous part of the experimental structure under a vibration load, and obtain structural stress features; the structural stress characteristics at least comprise stress power spectral density and volume distribution of dangerous parts;
a structural vibration fatigue life determination module 830, configured to perform structural vibration life analysis based on the structural stress feature, to obtain a structural vibration fatigue life;
The vibration stress simulation module 840 is configured to simulate vibration stress for each vibration magnitude in different load magnitudes, and repeatedly sample the vibration fatigue life of the structure to obtain simulated vibration life data under each magnitude;
And the material vibration S-N characteristic identification module 850 is used for comparing the simulated vibration life data with the experimental result data under various orders to determine the material vibration S-N characteristic.
Based on the apparatus in fig. 8, some specific implementation units may also be included:
optionally, the structural vibration fatigue life determining module 830 may specifically include:
an S-N characteristic description equation determining unit for selecting an S-N characteristic description equation of the material; the S-N characteristic description equation comprises a deterministic life equation and a life dispersion description equation under a given stress level;
The volume subdivision unit is used for subdividing the dangerous part according to a certain characteristic volume and determining the stress power spectral density of each characteristic volume;
and the vibration life determining unit is used for selecting a corresponding frequency domain life evaluation model, calculating the vibration life of each characteristic volume based on the S-N characteristic description equation and the stress power spectral density of each characteristic volume, and determining the minimum value in the vibration life of each characteristic volume as the structural vibration fatigue life.
Optionally, the S-N characteristic description equation represents a stress-fatigue life-unique functional relationship of the material; the S-N characteristic descriptive equation is expressed as:
；
Wherein, As a function of the lifetime of the device,In the form of a logarithm of the lifetime,The parameters are described for a deterministic life rule,As a result of the life-span dispersion coefficient,For a standard normal distribution, S represents stress and N is vibration lifetime.
Optionally, the vibration stress simulation module 840 may specifically include:
The simulated vibration life data determining unit is used for carrying out random assignment on life dispersion parameters in the S-N characteristic description equation of each characteristic volume under each vibration magnitude in different load magnitudes to obtain the vibration life; repeating for a plurality of times to obtain simulated vibration life data under various orders.
Optionally, the material vibration S-N characteristic identification module 850 may specifically include:
The S-N characteristic description equation optimizing unit is used for comparing the simulated vibration life data under each level with the experimental vibration life data of each level in the experimental result data; the simulated vibration life data of each magnitude covers the experimental vibration life data of each magnitude in the experimental result data, and under the condition that each magnitude meets the preset evaluation standard, the S-N characteristic description equation of the identification material is optimized.
Optionally, the apparatus may further include:
The distribution density function determining unit is used for fitting the simulated vibration life data of each level by using known distribution to obtain a distribution density function:
；
Wherein, For the life of the vibration,Is a distribution parameter;
the approximation degree evaluation unit is used for evaluating the function according to likelihood degree by using the distribution density function:
；
evaluating the approximation degree of the same-magnitude test life data and the simulation life data; wherein, In order to test the vibration life dispersion data,The ith trial representing the current magnitude,Representing the repetition number of the current magnitude test;
Evaluating and obtaining the approximation degree of the discrete data of each level of test and simulation vibration life by using the likelihood degree evaluation function;
And the overall approximation degree evaluation index determining unit is used for carrying out joint multiplication on the approximation degree calculated by each level to obtain an overall approximation degree evaluation index.
Alternatively, the S-N characteristic description equation optimizing unit may be specifically configured to:
taking the material S-N curve parameter in the S-N characteristic description equation as a design parameter, and determining the maximum value in the overall approximation degree evaluation index as an optimization target;
And optimizing and identifying the S-N curve parameters of the material based on the design parameters and the optimization targets.
Optionally, the apparatus may further include:
The material S-N curve drawing unit is used for drawing and obtaining a material S-N curve according to the optimized material S-N curve parameters;
And the vibration S-N characteristic determining unit is used for identifying the vibration S-N characteristic of the material based on the experimental result data of the material S-N curve combined structure vibration fatigue test.
Optionally, the structural vibration fatigue test module 810 may be specifically configured to:
Fixedly mounting a test structure on a vibrating table, adhering an acceleration sensor at an upper connecting position, adhering a strain gauge at an examination position, and adhering an acceleration control sensor at a lower connecting position; and applying a preset magnitude vibration load to the test structure by using the vibration table, and carrying out a vibration fatigue test of the structure or the simulated structure to obtain first-order natural frequency of the structure, strain measuring point response of the checking part and vibration fatigue life data under different load magnitudes.
Although the invention is described herein in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
Although the invention has been described in connection with specific features and embodiments thereof, it will be apparent that various modifications and combinations can be made without departing from the spirit and scope of the invention. Accordingly, the specification and drawings are merely exemplary illustrations of the present invention as defined in the appended claims and are considered to cover any and all modifications, variations, combinations, or equivalents that fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (9)
1. The material vibration S-N characteristic identification method based on the structural vibration test is characterized by comprising the following steps of:
Developing a structural vibration fatigue test of the target structure to obtain experimental result data; the experimental result data at least comprises structural vibration frequency characteristics, strain response and vibration fatigue life data under different load orders;
Establishing an experimental structure dynamics model based on the experimental result data, performing simulation on a vibration test by adopting the experimental structure dynamics model, identifying fatigue dangerous parts of the experimental structure under a vibration load, and obtaining structural stress characteristics; the structural stress characteristics at least comprise stress power spectral density and volume distribution of dangerous parts;
analyzing the structural vibration life based on the structural stress characteristics to obtain the structural vibration fatigue life;
simulating vibration stress aiming at each vibration level in different load levels, and repeatedly sampling the vibration fatigue life of the structure to obtain simulated vibration life data under each level;
comparing the simulated vibration life data with the experimental result data under each level to determine the vibration S-N characteristics of the material;
the structural vibration life analysis is performed based on the structural stress characteristics to obtain structural vibration fatigue life, and the method specifically comprises the following steps:
Selecting an S-N characteristic description equation of the material; the S-N characteristic description equation comprises a deterministic life equation and a life dispersion description equation under a given stress level;
subdividing the dangerous part according to a certain characteristic volume, and determining the stress power spectral density of each characteristic volume;
selecting a corresponding frequency domain life assessment model, calculating the vibration life of each characteristic volume based on the S-N characteristic description equation and the stress power spectral density of each characteristic volume, and determining the minimum value in the vibration life of each characteristic volume as the structural vibration fatigue life;
When the vibration life is simulated, the simulation stress result is utilized to simulate the vibration fatigue life of the test structure, and the method specifically comprises the following steps: three parameters S-N equation are chosen, as the formula:
；
Wherein, In the form of a logarithm of the lifetime,As a result of the life-span dispersion coefficient,Is a standard normal distribution, S represents stress, N is vibration life,、、The method comprises the steps of taking the static fatigue corresponding parameters of the same material as the fatigue characteristic parameters of the material during initial analysis;
Selection of characteristic volume Subdividing the dangerous part, and obtaining the vibration stress of each characteristic volume and the power spectrum density thereof by using stress data;
A Dirlik model is selected, as the formula:
；
Wherein, AndRespectively the 2 nd order moment and the 4 th moment of the stress power spectrum density,Probability density function of stress amplitude; therefore, on the basis of a material S-N equation and the stress power spectral density of each characteristic volume, calculating the vibration life of each volume; and finally, counting and identifying the minimum value of the vibration life in each volume as the structural vibration fatigue life.
2. The method for identifying the S-N characteristics of the vibration of the material based on the structural vibration test according to claim 1, wherein the S-N characteristic description equation represents the stress-fatigue life-unique function relationship of the material; the S-N characteristic descriptive equation is expressed as:
；
Wherein, As a function of the lifetime of the device,Parameters are described for deterministic life laws.
3. The method for identifying the S-N characteristics of material vibration based on a structural vibration test according to claim 1, wherein for each vibration magnitude in different load magnitudes, simulation of vibration stress is performed, and repeated sampling is performed on the structural vibration fatigue life, so as to obtain simulated vibration life data under each magnitude, and the method specifically comprises the following steps:
Under each vibration level in different load levels, carrying out random assignment on life dispersion parameters in the S-N characteristic description equation of each characteristic volume to obtain vibration life; repeating for a plurality of times to obtain simulated vibration life data under various orders.
4. The method for identifying the S-N characteristics of the material vibration based on the structural vibration test according to claim 1, wherein the comparing the simulated vibration life data with the experimental result data under each magnitude is adopted to determine the S-N characteristics of the material vibration, and specifically comprises the following steps:
Comparing the simulated vibration life data under each level with the experimental vibration life data of each level in the experimental result data; the simulated vibration life data of each magnitude covers the experimental vibration life data of each magnitude in the experimental result data, and under the condition that each magnitude meets the preset evaluation standard, the S-N characteristic description equation of the identification material is optimized.
5. The method for identifying the S-N characteristics of the material vibration based on the structural vibration test according to claim 4, wherein before optimizing the S-N characteristic description equation of the identified material under the condition that the predetermined evaluation criteria are satisfied at each magnitude, further comprises:
fitting the simulated vibration life data of each magnitude by using known distribution to obtain a distribution density function:
；
Wherein, For the life of the vibration,Is a distribution parameter;
Using the distribution density function, evaluating the function according to the likelihood degree:
；
evaluating the approximation degree of the same-magnitude test life data and the simulation life data; wherein, In order to test the vibration life dispersion data,The ith trial representing the current magnitude,Representing the repetition number of the current magnitude test;
Evaluating and obtaining the approximation degree of the discrete data of each level of test and simulation vibration life by using the likelihood degree evaluation function;
and carrying out joint multiplication on the approximation degree calculated by each magnitude to obtain an overall approximation degree evaluation index.
6. The method for identifying the S-N characteristics of the material vibration based on the structural vibration test according to claim 5, wherein the S-N characteristic description equation of the identified material is optimized under the condition that the predetermined evaluation standard is satisfied at each magnitude, specifically comprising:
taking the material S-N curve parameter in the S-N characteristic description equation as a design parameter, and determining the maximum value in the overall approximation degree evaluation index as an optimization target;
And optimizing and identifying the S-N curve parameters of the material based on the design parameters and the optimization targets.
7. The method for identifying the S-N characteristics of the vibration of the material based on the structural vibration test according to claim 6, further comprising, after optimizing the S-N curve parameters of the identified material based on the design parameters and the optimization objective:
drawing a material S-N curve according to the optimized material S-N curve parameters;
and identifying the vibration S-N characteristic of the material based on experimental result data of the material S-N curve combined structure vibration fatigue test.
8. The method for identifying the S-N characteristics of the vibration of the material based on the structural vibration test according to claim 1, wherein the step of performing the structural vibration fatigue test of the target structure to obtain experimental result data comprises the following steps:
Fixedly mounting a test structure on a vibrating table, adhering an acceleration sensor at an upper connecting position, adhering a strain gauge at an examination position, and adhering an acceleration control sensor at a lower connecting position; and applying a preset magnitude vibration load to the test structure by using the vibration table, and carrying out a vibration fatigue test of the structure or the simulated structure to obtain first-order natural frequency of the structure, strain measuring point response of the checking part and vibration fatigue life data under different load magnitudes.
9. Material vibration S-N characteristic recognition device based on structure vibration test, its characterized in that, the device includes:
The structure vibration fatigue test module is used for carrying out a structure vibration fatigue test of the target structure to obtain experimental result data; the experimental result data at least comprises structural vibration frequency characteristics, strain response and vibration fatigue life data under different load orders;
the structural stress feature determining module is used for establishing an experimental structural dynamics model based on the experimental result data, carrying out simulation on a vibration test by adopting the experimental structural dynamics model, identifying fatigue dangerous parts of the test structure under the vibration load and obtaining structural stress features; the structural stress characteristics at least comprise stress power spectral density and volume distribution of dangerous parts;
the structural vibration fatigue life determining module is used for analyzing the structural vibration life based on the structural stress characteristics to obtain the structural vibration fatigue life;
The vibration stress simulation module is used for simulating vibration stress aiming at each vibration magnitude in different load magnitudes, and repeatedly sampling the vibration fatigue life of the structure to obtain simulated vibration life data under each magnitude;
The material vibration S-N characteristic identification module is used for comparing simulated vibration life data under various orders with the experimental result data to determine the material vibration S-N characteristic;
The structural vibration fatigue life determining module specifically comprises:
an S-N characteristic description equation determining unit for selecting an S-N characteristic description equation of the material; the S-N characteristic description equation comprises a deterministic life equation and a life dispersion description equation under a given stress level;
The volume subdivision unit is used for subdividing the dangerous part according to a certain characteristic volume and determining the stress power spectral density of each characteristic volume;
The vibration life determining unit is used for selecting a corresponding frequency domain life evaluation model, calculating the vibration life of each characteristic volume based on the S-N characteristic description equation and the stress power spectral density of each characteristic volume, and determining the minimum value in the vibration life of each characteristic volume as the structural vibration fatigue life;
When the vibration life is simulated, the simulation stress result is utilized to simulate the vibration fatigue life of the test structure, and the method specifically comprises the following steps: three parameters S-N equation are chosen, as the formula:
；
Wherein, 、、The method comprises the steps of taking the static fatigue corresponding parameters of the same material as the fatigue characteristic parameters of the material during initial analysis;
Selection of characteristic volume Subdividing the dangerous part, and obtaining the vibration stress of each characteristic volume and the power spectrum density thereof by using stress data;
A Dirlik model is selected, as the formula:
；
Wherein, AndRespectively the 2 nd order moment and the 4 th moment of the stress power spectrum density,Probability density function of stress amplitude; therefore, on the basis of a material S-N equation and the stress power spectral density of each characteristic volume, calculating the vibration life of each volume; and finally, counting and identifying the minimum value of the vibration life in each volume as the structural vibration fatigue life.
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