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CN111947950B - Multi-dimensional comprehensive stress life test load spectrum design method based on load information matrix - Google Patents

Multi-dimensional comprehensive stress life test load spectrum design method based on load information matrix Download PDF

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CN111947950B
CN111947950B CN202010630354.XA CN202010630354A CN111947950B CN 111947950 B CN111947950 B CN 111947950B CN 202010630354 A CN202010630354 A CN 202010630354A CN 111947950 B CN111947950 B CN 111947950B
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CN111947950A (en
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马仲海
聂松林
尹方龙
纪辉
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Beijing University of Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M99/00—Subject matter not provided for in other groups of this subclass
    • G01M99/007—Subject matter not provided for in other groups of this subclass by applying a load, e.g. for resistance or wear testing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
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Abstract

The invention discloses a multi-dimensional comprehensive stress life test load spectrum design method based on a load information matrix, which is applied to the field of life tests of electromechanical equipment under complex working conditions. The method is characterized in that a load information matrix statistical method is utilized to perform statistical analysis on various different types of stress characteristics borne under complex working conditions, and an acceleration model is utilized to perform normalization processing on stress levels. The load information matrix can take account of the application duration of different types of stress and the switching frequency before the stress level. The comprehensive stress test load spectrum of the electromechanical equipment subjected to various stresses at the same time can be effectively counted and analyzed, and the stress level of the load information matrix can be accelerated according to the acceleration factor according to the equivalent accumulated damage consistency theory, so that the test application is shortened, and the design of the accelerated life test load spectrum is completed. The method provides an effective load spectrum statistics and design method for electromechanical equipment bearing multidimensional stress, and facilitates the development of a life test and an accelerated life test.

Description

Multi-dimensional comprehensive stress life test load spectrum design method based on load information matrix
Technical Field
The invention belongs to the field of reliability and service life tests of electromechanical products, and particularly relates to a multi-dimensional comprehensive stress test load spectrum design method based on a load information matrix.
Background
The reliability life test plays an important role in the determination and verification of the reliability of the electromechanical product and the further improvement and guidance of the service life of the equipment, and the service life characteristics and the failure rule of the tested product can be deeply known through the reliability life test. Generally, the life characteristics of some simple electromechanical devices are obtained by a life test method under normal conditions. However, for the electromechanical products with high reliability and long service life, such as the hydraulic pump of the airplane for example, because the electromechanical products have precise design, complex manufacturing process, high production cost and strong specificity, the electromechanical products are generally not produced in large quantities, and the situations of carrying out life tests of the whole life cycle and related destructive life tests are fewer. The life test under normal conditions can cause the life test cycle to be overlong, the life test cost is huge, the development cycle can be overlong, the development requirement cannot be matched, and the market competitiveness of the product is reduced. Therefore, in engineering, an accelerated life test method is generally adopted to evaluate the life of the electromechanical products, that is, on the premise that a failure mechanism is not changed, the working stress is improved, so that the test time of the tested products is accelerated.
At present, the accelerated life test method of electronic products is mature, has perfect test specifications and statistical methods, can be classified into constant stress acceleration, stepping stress acceleration, sequential stress acceleration and alternating stress acceleration, and mostly adopts single stress to test. The electromechanical product is more complex than an electronic product because of a failure mechanism, and can be stressed by various types of stress such as constant stress, alternating stress and the like in the operation process, the characteristics of various failure modes, serious stress coupling, variable stress bearing and the like are determined by the complexity of working conditions and periodic stress, and the service life characteristic of the electromechanical product cannot be completely dependent on the action of single stress. Therefore, the traditional single-stress acceleration test load spectrum is difficult to meet the acceleration test requirements of mechanical products under multiple stresses, the test result has deviation from the service life index under the actual working condition, and great challenges are brought to reliability and service life evaluation. Considering that the load spectrum and the acceleration method under the test environment of the existing electromechanical product are difficult to accurately reflect the actual complex working conditions and give an accurate service life evaluation result, how to design the service life test aiming at the characteristics of the actual multidimensional stress and the load spectrum of the accelerated service life test become the key for breaking through the theory and the statistical method of the multidimensional comprehensive stress accelerated service life test of the electromechanical product.
Disclosure of Invention
The invention provides a multi-dimensional comprehensive stress life test load spectrum design method based on a load information matrix, aiming at realizing that a reliability life test of an electromechanical product can be matched with a complex working condition under a multi-stress load on the premise of not changing the failure mechanism of the electromechanical product, provides a practical, operable and practical load spectrum design method according with the actual working condition for the statistics and design of the multi-stress load spectrum of the electromechanical product, and provides an effective method for the design and life evaluation of the reliability life test load spectrum.
The technical scheme adopted by the invention is a multi-dimensional comprehensive stress life test load spectrum design method based on a load information matrix, and specifically comprises the following steps:
analyzing a failure mode and a failure mechanism of an electromechanical product needing a life test, and extracting sensitive stress related to the failure mechanism;
secondly, selecting a corresponding acceleration model according to the failure mechanism of the described electromechanical product, and establishing the relation between the failure process of the electromechanical product and the sensitive stress; normalizing all the stresses according to the stress range which can be borne;
thirdly, establishing a load information matrix for the normalized sensitive stress and respective stress characteristics to form a multi-dimensional comprehensive stress load information matrix;
designing a comprehensive stress reliability life test load spectrum under the conventional stress by utilizing a load matrix and a load spectrum generation algorithm; and if an acceleration life test needs to be designed, improving the stress level in the load matrix according to the acceleration factor, and then generating an acceleration load spectrum. And finally, guiding the service life test by using the generated multidimensional comprehensive stress test load spectrum.
The invention has the advantages that:
(1) according to the method, through characteristic analysis of various stresses under a conventional working condition, a design flow of a load spectrum under the combined action of multi-dimensional stresses is formulated, and the actual operation working condition of the described electromechanical product is truly reflected;
(2) the load spectrum design method based on the load information matrix not only can be used for generating a life test load spectrum, but also can represent the distribution of each stress level and the influence on the life of the electromechanical product through the load information matrix;
(3) the accelerated life test design basis based on the load information matrix is provided, the accelerated load information matrix is calculated on the premise that the failure mechanism is not changed, the stress level is improved, the acceleration spectrum is generated, and the test time is greatly shortened.
Drawings
FIG. 1 is a diagram of four common stress types;
FIG. 2 is a four stress load information matrix;
FIG. 3 is a composite stress test spectrum generated based on a load information matrix;
FIG. 4 is a cross section of the flow rate of a life test of a hydraulic pump;
FIG. 5 is a cross section of the rotating speed of the hydraulic pump in the life test;
FIG. 6 is a hydraulic pump composite stress test spectrum generated based on a load information matrix;
fig. 7 is a flow chart of a method of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The invention relates to a multi-dimensional comprehensive stress life test load spectrum design method based on a load information matrix, the flow is shown as figure 7, and the method comprises the following steps:
the method comprises the steps of firstly, analyzing a main failure mode and a failure mechanism of the electromechanical product, and extracting sensitive stress related to failure.
Summarizing failure modes and extracting sensitive stress which is marked as S according to the operation environment of the electromechanical product and the analysis of various failure samples1,S2,...,SNWherein N is the total stress number.
Selecting a corresponding acceleration model according to the failure mechanism of the described electromechanical product, establishing the relation between the failure process of the product and the sensitive stress, and carrying out normalization processing on all the stresses according to the minimum stress and the maximum limit stress;
respectively with Sn,0,Sn,HThe minimum stress and the maximum ultimate stress (N ═ 1,2, …, N) representing the nth stress, and the corresponding normalized calculation formula is adopted for different acceleration models, and the common acceleration models based on failure physics mainly include a power law model, an Arrhenius (Arrhenius) model, an exponential model and the like, and the relation between the stress and the degradation process is represented by h(s), and the above models can be described as follows:
Figure BDA0002564591180000031
wherein ξ0And alpha is a model coefficient, s is the stress magnitude, the model is subjected to unified normalization processing, x is more than or equal to 0 and less than or equal to 1 to represent the normalized stress magnitude value, and the normalized equation can be described as follows:
h(x)＝exp(α0+α1x) (2)
wherein alpha is0And alpha1The values of the coefficients of the equation after the normalization processing are related to an acceleration model, and are shown in a formula (3):
Figure BDA0002564591180000032
in the formula s0And sHMinimum stress and maximum ultimate stress levels, respectively.
Stress of nthnThe normalized expression of (a) is solved by the following form:
Figure BDA0002564591180000041
Figure BDA0002564591180000042
is a function related to an acceleration model, and the calculation of stress values of different models can be obtained according to the formulas (1) and (2):
Figure BDA0002564591180000043
thirdly, establishing a load information matrix for the normalized sensitive stress and respective stress characteristics to form a multi-dimensional comprehensive stress load information matrix;
the load information matrix comprises all stresses and stress magnitudes in the test and test time information, and is recorded as LIM (n, i, j), wherein i and j are different stress levels respectively. The load information matrix is a three-dimensional matrix, and for four common stress types as shown in fig. 1, the statistical method is as follows:
(1) alternating stress load information matrix statistical method
For an electromechanical product with periodic motion, it is inevitable to be subjected to periodic alternating stress, as shown in fig. 1(a), such stress includes the switching characteristics between different stress levels and the duration of the stress levels. Assuming this stress is the 1 st stress, the stress sequence in this time domain can be described as:
Figure BDA0002564591180000044
wherein: LIM (1, i, j) represents a load information matrix of stress 1, i, j are respectively different stress levels, tiThe duration of each stress stage, T is the total duration of stress 1,
Figure BDA0002564591180000045
mi,ja statistical value representing the transition of stress 1 from level i to level j,
Figure BDA0002564591180000046
operators representing the number of elements in the set, k representing the load switch point, XkThe load information matrix of the stress 1 can be obtained by information statistics of the stress spectrum in the time domain for the state at the switching point k.
Specifically, taking the load spectrum in fig. 1(a) as an example, the load information matrix obtained by analyzing and counting the original signal is as follows:
Figure BDA0002564591180000051
(2) stepping stress load information matrix statistical method
Assuming that this stress is the 2 nd stress, as shown in fig. 1(b), for a step stress, it can be regarded as an alternating stress sequence in which the stress is switched from a low level to a high level only, and according to equation (6), the step stress load information matrix can be described as:
Figure BDA0002564591180000052
thus, taking the load spectrum in fig. 1(b) as an example, the load information matrix of constant stress can be represented as:
Figure BDA0002564591180000053
(3) sequence-advance stress load information matrix statistical method
As shown in FIG. 1(c), assuming the progressive stress is the 3 rd stress, the stress level thereof gradually increases with time, and therefore, attention needs to be paid to the initial stress level x thereoflAnd final cut-off stress level xuThe step stress load information matrix may be described as:
Figure BDA0002564591180000054
here, ═ δ (T) dt ═ T is the total test duration.
Figure BDA0002564591180000061
(4) Constant stress load information matrix statistical method
As shown in fig. 1(d), assuming that the constant stress is the 4 th stress, the stress remains unchanged for the total test duration, and therefore, the load information matrix for the constant stress can be described as:
Figure BDA0002564591180000062
namely, the load information matrix of fig. 1(d) is:
LIM(4,i,j)＝40,i＝j＝0.4 (13)
based on the above-mentioned statistics for different types of stress load information, the final integrated stress load information matrix of the product can be represented as shown in fig. 2. Through statistics and analysis of the comprehensive load information matrix, stress distribution and duration of each grade of stress can be obtained, and therefore all stress characteristics borne by the life cycle of the product are described uniformly.
Designing a comprehensive stress reliability life test load spectrum under the conventional stress by using a load matrix and a load spectrum generation algorithm; and if an acceleration life test needs to be designed, improving the stress level in the load matrix according to the acceleration factor, and then generating an acceleration load spectrum. And finally, guiding the service life test by using the generated multidimensional comprehensive stress test load spectrum.
(1) Load spectrum generation method for conventional life test
Since the load information matrix includes both the switching frequency information of the stress sequence and the duration of each level of stress, the switching probability of the stress level is calculated according to the load information matrix LIM (n, i, j). Using X as a certain state in the stress sequence, and using P (X) corresponding to each level of stressk＝xk|Xk-1＝xk-1) Indicates that the state k is x at the switching timekAnd the probability is related to the probability of switching point k-1 only. Further calculation is carried out through LIM (n, i, j), and a transition matrix Q of the state can be obtainedTThe following are:
Figure BDA0002564591180000063
Figure BDA0002564591180000064
wherein q isijFor the magnitude of the probability of transition from stress level i to stress level j, diThe proportion of the duration of the load at stress level i.
Using a transfer matrix QTI.e. a conventional load spectrum can be generated from the switching characteristics of the stress. The above four categoriesThe conventional load spectrum of stress generation is shown in fig. 3.
(2) Accelerated life test load spectrum generation method
According to the principle of equivalent damage consistency, reversely deducing the stress after acceleration through a set acceleration factor and an acceleration model, obtaining the stress after acceleration according to a formula (3), and utilizing a transfer matrix QTAn acceleration load spectrum is generated.
The invention adopts a life test load spectrum design method based on a load information matrix to count the full life cycle load of an electromechanical product under multidimensional stress, the information matrix not only realizes the statistical description of a time domain stress sequence in the matrix, but also can analyze stress distribution and switching states of various levels through the load matrix, and a load spectrum for guiding the life test is designed and generated through load matrix operation. The method provided by the invention realizes statistics and reproduction of the load spectrum under the complex working conditions under multiple stresses according to the physical failure mechanism of the electromechanical equipment without changing the failure mode of the electromechanical equipment, and can efficiently and quickly generate the load spectrum of the life test and guide the life test.
Examples
The life test load spectrum of the aviation general variable hydraulic pump is designed as follows by adopting the method of the invention:
the aviation general variable pump mostly adopts the form of a plunger pump, and the plunger pump is used as a main energy supply element of aircraft hydraulic equipment, is an indispensable important component of an airborne hydraulic system, and the service life and the quality of the plunger pump can influence the safety and the reliability of the whole aircraft. Therefore, life tests are performed on such plunger pumps. Firstly, through the analysis of the failure mechanism of the plunger pump, the sensitive stress of the plunger pump mainly comprises the rotating speed, the working pressure and the outlet flow of the pump. Therefore, these three types of stresses are mainly applied in designing a load spectrum for a life test. The minimum stress and the maximum ultimate stress are shown in table 1.
TABLE 1 minimum and maximum ultimate stress for plunger pumps
Figure BDA0002564591180000071
In the actual operation, the output flow rate of the hydraulic pump is shown in table 2.
TABLE 2 flow demand table for each flight phase
Figure BDA0002564591180000072
Figure BDA0002564591180000081
Through the failure mechanism analysis of the plunger pump, the main failure reason is leakage and vibration increase caused by the abrasion of three pairs of key friction pairs (rotor-valve plate pair, cylinder body-plunger pair and sliding shoe-swash plate pair), and finally the plunger pump fails to work normally and fails. Wherein, the abrasion of the rotor-thrust plate pair and the slipper-swash plate pair is calculated by adopting a power rate model:
v1＝apbωc (16)
wherein v is1For wear rate, p is pressure and ω is hydraulic pump speed. and a, b and c need to carry out parameter estimation according to experimental data. And the cylinder-plunger pair can be described by an Archard wear model:
v2＝KeQ2p (17)
wherein, KeAre Archard wear model coefficients. In the service life test of the hydraulic pump, constant stress is adopted for pressure, and alternating stress is adopted for flow according to the working condition requirement. Based on the SAE-AS19692B hydraulic pump general test standard shown in FIG. 4 and FIG. 5, the normalized statistical analysis is performed on the flow and rotation speed stress levels and the switching characteristics, the normalized stress level can be solved according to the power law model of formula (5), and the flow and rotation speed law is shown in FIG. 4 and FIG. 5.
Through statistics of the stress sequence, a flow load information matrix LIM (1, i, j) and a rotation speed load information matrix LIM (2, i, j) can be obtained as follows:
Figure BDA0002564591180000082
Figure BDA0002564591180000083
since the pressure is a constant stress, LIM (3, i, j) is 2000, and i is 0.
By using the load information matrix and the load generation method, the load spectrum of three conventional 2000-hour life tests of the flow rate, the rotating speed and the pressure of the hydraulic pump is shown in fig. 6. If acceleration is needed, the magnitude of the acceleration stress can be calculated according to the required acceleration factor and the formulas (16) and (17) respectively, so as to ensure that the wear rates before and after acceleration are consistent. By performing the load spectrum as shown in fig. 6 according to the new stress level, the test time can be shortened, and the acceleration can be achieved.

Claims (3)

1.一种基于载荷信息矩阵的多维综合应力寿命试验载荷谱设计方法，其特征在于：1. a multi-dimensional comprehensive stress life test load spectrum design method based on load information matrix, is characterized in that: 步骤一、分析需要进行寿命试验的机电产品其失效模式及失效机理，并且提取与失效机理相关的敏感应力；Step 1. Analyze the failure mode and failure mechanism of the electromechanical product that needs to be tested for life, and extract the sensitive stress related to the failure mechanism; 步骤二、根据所描述机电产品的失效机理，选取相应的加速模型，建立机电产品的失效过程与敏感应力之间的关系；按照所能承受的应力范围大小，对所有应力进行归一化处理；Step 2: According to the described failure mechanism of the electromechanical product, select a corresponding acceleration model to establish the relationship between the failure process of the electromechanical product and the sensitive stress; normalize all the stresses according to the range of the stress that can be tolerated; 步骤三、对上述归一化处理的敏感应力及各自的应力特性，建立载荷信息矩阵，形成多维综合应力载荷信息矩阵；Step 3, establishing a load information matrix for the above-mentioned normalized sensitive stress and their respective stress characteristics, and forming a multi-dimensional comprehensive stress load information matrix; 步骤四、利用载荷矩阵以及载荷谱生成算法，设计常规应力下的综合应力可靠性寿命试验载荷谱；若需要设计加速寿命试验，则根据加速因子，提高载荷矩阵中的应力等级，再进行加速载荷谱的生成；最后利用生成的多维综合应力试验载荷谱指导寿命试验；Step 4. Use the load matrix and the load spectrum generation algorithm to design the load spectrum of the comprehensive stress reliability life test under conventional stress; if an accelerated life test needs to be designed, increase the stress level in the load matrix according to the acceleration factor, and then carry out the accelerated load Generation of spectrum; finally, the generated multi-dimensional comprehensive stress test load spectrum is used to guide the life test; 步骤一中，根据机电产品的运行环境以及对各类失效样本的分析，总结失效模式，并提炼敏感应力，记为S1,S2,...,SN，其中，N为总的应力个数；In step 1, according to the operating environment of the electromechanical product and the analysis of various failure samples, the failure mode is summarized, and the sensitive stress is refined, denoted as S 1 , S 2 ,...,S N , where N is the total stress number; 步骤二中，分别用Sn,0,Sn,H表示第n个应力的最小应力和最大极限应力，n＝1,2,…,N)，对于不同的加速模型采用与之对应的归一化计算公式，用h(s)来表示应力与退化过程的关系，加速模型描述为：In step 2, Sn,0 , Sn ,H are used to represent the minimum stress and maximum ultimate stress of the nth stress, n=1,2,...,N), and the corresponding normalization is used for different acceleration models. The unified calculation formula uses h(s) to represent the relationship between the stress and the degradation process. The acceleration model is described as:
Figure FDA0003454768830000011
Figure FDA0003454768830000011
 ξ0和α为模型系数，s为应力大小，对上述模型进行统一归一化处理，用0≤x≤1来表示归一化后的应力大小值，归一化后的方程描述为：ξ 0 and α are the model coefficients, and s is the stress size. The above model is uniformly normalized, and 0≤x≤1 is used to represent the normalized stress size value. The normalized equation is described as: h(x)＝exp(α0+α1x) (2)h(x)=exp(α 0 +α 1 x) (2) α0和α1为归一化处理后方程的系数，其取值与加速模型相关，如公式(3)所示：α 0 and α 1 are the coefficients of the equation after normalization, and their values are related to the acceleration model, as shown in formula (3):
Figure FDA0003454768830000012
Figure FDA0003454768830000012
 式中s0和sH分别为最小应力和最大极限应力大小；where s 0 and s H are the minimum stress and maximum ultimate stress, respectively; 第n个应力sn的归一化表述由如下形式进行求解：The normalized representation of the nth stress sn is solved by:
Figure FDA0003454768830000021
Figure FDA0003454768830000021
Figure FDA0003454768830000022
是与加速模型相关的函数，根据公式(1)和(2)即可得到不同模型应力值的计算：
Figure FDA0003454768830000022
is a function related to the acceleration model. According to formulas (1) and (2), the calculation of the stress values of different models can be obtained:
Figure FDA0003454768830000023
Figure FDA0003454768830000023
 2.根据权利要求1所述的一种基于载荷信息矩阵的多维综合应力寿命试验载荷谱设计方法，其特征在于：2. a kind of multi-dimensional comprehensive stress life test load spectrum design method based on load information matrix according to claim 1, is characterized in that: 载荷信息矩阵包括试验中的所有应力以及应力大小，试验时间信息，载荷信息矩阵记为LIM(n,i,j),其中，i，j分别为不同的应力等级；The load information matrix includes all the stresses in the test, the stress magnitude, and the test time information. The load information matrix is denoted as LIM(n, i, j), where i and j are different stress levels; 该载荷信息矩阵是一个三维矩阵，针对四种应力类型，统计方法如下：The load information matrix is a three-dimensional matrix. For the four stress types, the statistical methods are as follows: (1)交变应力载荷信息矩阵统计方法(1) Statistical method of alternating stress load information matrix 对于做周期性运动的机电产品，不可避免会受到周期性的交变应力，此类应力包括不同应力等级间切换特性以及应力等级的持续时长；假设此应力为第1个应力，该时域内的应力序列可以描述为：For electromechanical products that do periodic motion, periodic alternating stress is inevitable. Such stress includes the switching characteristics between different stress levels and the duration of the stress level. Assuming that this stress is the first stress, the stress in this time domain The stress sequence can be described as:
Figure FDA0003454768830000024
Figure FDA0003454768830000024
 其中：LIM(1,i,j)表示应力1的载荷信息矩阵，i，j分别为不同的应力等级，ti为各级应力持续的时间，T为应力1总时长，
Figure FDA0003454768830000025
mi,j表示应力1从等级i转移到等级j的统计值，
Figure FDA0003454768830000026
表示集合中元素个数的运算符，k表示载荷切换点，Xk为在切换点k时的状态，通过对时域中应力谱的信息统计，即可得到应力1的载荷信息矩阵；Among them: LIM(1,i,j) represents the load information matrix of stress 1, i, j are different stress levels, t i is the duration of stress at all levels, T is the total duration of stress 1,
Figure FDA0003454768830000025
m i,j represents the statistical value of the transfer of stress 1 from level i to level j,
Figure FDA0003454768830000026
is an operator representing the number of elements in the set, k represents the load switching point, X k is the state at the switching point k, and the load information matrix of stress 1 can be obtained by statistics of the stress spectrum in the time domain; 载荷谱中，通过对原信号的分析并统计，得到其载荷信息矩阵如下：In the load spectrum, through the analysis and statistics of the original signal, the load information matrix is obtained as follows:
Figure FDA0003454768830000031
Figure FDA0003454768830000031
 (2)步进应力载荷信息矩阵统计方法(2) Statistical method of step-by-step stress load information matrix 假设此应力为第2个应力，对于步进应力，应力只从低等级向高等级切换的交变应力序列，根据公式(6)，步进应力载荷信息矩阵描述为：Assuming that this stress is the second stress, for the step stress, the stress only switches from the low level to the high level of the alternating stress sequence. According to formula (6), the step stress load information matrix is described as:
Figure FDA0003454768830000032
Figure FDA0003454768830000032
 载荷谱中，恒定应力的载荷信息矩阵表示为：In the load spectrum, the load information matrix of constant stress is expressed as:
Figure FDA0003454768830000033
Figure FDA0003454768830000033
 (3)序进应力载荷信息矩阵统计方法(3) Statistical method of sequential stress load information matrix 假设序进应力为第3个应力，应力等级随时间逐渐增大，初始应力等级xl以及最终截止应力等级xu步进应力载荷信息矩阵描述为：Assuming that the sequential stress is the third stress, and the stress level gradually increases with time, the initial stress level x l and the final cut-off stress level x u step stress load information matrix is described as:
Figure FDA0003454768830000034
Figure FDA0003454768830000034
 ∫δ(t)dt＝T为总试验时长；∫δ(t)dt=T is the total test duration;
Figure FDA0003454768830000035
Figure FDA0003454768830000035
 (4)恒定应力载荷信息矩阵统计方法(4) Statistical method of constant stress load information matrix 假设恒定应力为第4个应力，该应力在总试验时长下保持不变，恒定应力的载荷信息矩阵描述为：Assuming that the constant stress is the 4th stress, which remains constant over the total test duration, the load information matrix for the constant stress is described as:
Figure FDA0003454768830000041
Figure FDA0003454768830000041
 载荷信息矩阵为：The load information matrix is: LIM(4,i,j)＝40,i＝j＝0.4 (13)LIM(4,i,j)=40,i=j=0.4 (13) 根据对不同类型应力载荷信息的分别统计，最终该产品的综合应力载荷信息矩阵；通过对综合载荷信息矩阵的统计与分析，即可得到应力分布以及各等级应力的持续时间，从而对产品生命周期所承受的所有应力特性统一进行描述。According to the statistics of different types of stress and load information, the final comprehensive stress and load information matrix of the product; through the statistics and analysis of the comprehensive load information matrix, the stress distribution and the duration of each level of stress can be obtained, so as to determine the product life cycle. All stress characteristics experienced are described uniformly. 3.根据权利要求2所述的一种基于载荷信息矩阵的多维综合应力寿命试验载荷谱设计方法，其特征在于：3. a kind of multi-dimensional comprehensive stress life test load spectrum design method based on load information matrix according to claim 2, is characterized in that: 步骤四中，In step four, (1)常规寿命试验载荷谱生成方法(1) Generation method of conventional life test load spectrum 由于载荷信息矩阵中既包含应力序列的切换频次信息，又包含每个等级应力的持续时间，根据载荷信息矩阵LIM(n,i,j)，计算应力等级的切换概率；以x为应力序列中的某个状态，对应各个等级的应力，用P(Xk＝xk|Xk-1＝xk-1)表示在切换时刻k状态为xk的概率，且该概率仅仅与切换点k-1的概率有关；通过LIM(n,i,j)进行进一步的计算，即得到状态的转移矩阵QT，如下：Since the load information matrix contains not only the switching frequency information of the stress sequence, but also the duration of each level of stress, the switching probability of the stress level is calculated according to the load information matrix LIM(n, i, j); A certain state of , corresponding to the stress of each level, use P(X k =x k |X k-1 =x k-1 ) to represent the probability that the state k is x k at the switching moment, and this probability is only related to the switching point k The probability of -1 is related; further calculation is performed by LIM(n,i,j), that is, the state transition matrix Q T is obtained, as follows:
Figure FDA0003454768830000042
Figure FDA0003454768830000042
Figure FDA0003454768830000043
Figure FDA0003454768830000043
 其中，qij为从应力等级i转移到应力等级j的概率大小，di为应力等级为i时载荷持续时长所占的比例；Among them, q ij is the probability of transferring from the stress level i to the stress level j, and d i is the proportion of the load duration when the stress level is i; 利用转移矩阵QT，即可根据应力的切换特性生成常规载荷谱；上述四类应力生成的常规载荷谱；Using the transfer matrix Q T , the conventional load spectrum can be generated according to the switching characteristics of the stress; the conventional load spectrum generated by the above four types of stress; (2)加速寿命试验载荷谱生成方法(2) Generation method of accelerated life test load spectrum 根据等效损伤一致原则，通过设定的加速因子和加速模型反推加速后的应力大小，根据公式(3)得到加速后的应力大小，利用转移矩阵QT生成加速载荷谱。According to the principle of equivalent damage consistency, the stress after acceleration is reversed through the set acceleration factor and acceleration model, and the stress after acceleration is obtained according to formula (3), and the acceleration load spectrum is generated by using the transfer matrix QT .
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