WO2023077704A1 - 基于sn曲线的随机应力载荷谱分级方法、系统和存储介质 - Google Patents

基于sn曲线的随机应力载荷谱分级方法、系统和存储介质 Download PDF

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WO2023077704A1
WO2023077704A1 PCT/CN2022/079873 CN2022079873W WO2023077704A1 WO 2023077704 A1 WO2023077704 A1 WO 2023077704A1 CN 2022079873 W CN2022079873 W CN 2022079873W WO 2023077704 A1 WO2023077704 A1 WO 2023077704A1
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stress
spectrum
curve
fatigue life
level
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PCT/CN2022/079873
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French (fr)
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王有智
程拼拼
孙秀兵
傅晶焱
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上海合科科技有限公司
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/15—Vehicle, aircraft or watercraft design
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/17—Mechanical parametric or variational design
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/04—Ageing analysis or optimisation against ageing
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces

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  • the present invention relates to the field of transportation, in particular to a SN curve-based random stress load spectrum grading method used in various types of vehicle chassis load calculations;
  • the random stress load spectrum grading system for curves is a computer-readable storage medium for executing each step in the SN curve-based random stress load spectrum grading method.
  • the SN curve takes the fatigue strength of the material standard specimen as the ordinate, and takes the logarithm of the fatigue life lg N as the abscissa, which represents the relationship between the fatigue strength and the fatigue life of the standard specimen under certain cycle characteristics, also known as stress- life curve.
  • the random load spectrum needs to be simulated by the program load spectrum.
  • the program load spectrum of 4 to 16 levels can be compiled, which depends on the influence of the load spectrum level and series on the fatigue life.
  • the error between the test life and the random load spectrum, the 4th level load spectrum is larger than the 8th level load spectrum, and the load spectrum exceeding the 8th level is very similar to the 8th level load spectrum, and the 8th level program load spectrum is generally used.
  • interval method and amplitude ratio (ratio between the load value of a certain level and the maximum load value) coefficient method for the division of the load size of each level in the load spectrum of the 8-level program, usually according to the Conover amplitude ratio coefficient 1.0, 0.95, 0.85, 0.725 , 0.575, 0.425, 0.275, 0.125 classification.
  • an 8-level program load spectrum is used to simulate a random load spectrum, and the ratio coefficient adopts a fixed value, and the ratio coefficient has nothing to do with the characteristics of the random load spectrum.
  • large errors will be generated.
  • the fatigue life is more sensitive to the magnitude of the large value, and the error of fatigue calculation can be reduced by dividing more series for the magnitude of the large value.
  • the amplitude ratio coefficient in the prior art is fixed, and cannot be divided into more series in a large amplitude range, and cannot control the size of the fatigue life error caused by the classification.
  • the solution of the prior art is: consider the influence of load and frequency at the same time, allocate the frequency between the two load levels, improve the situation that the damage effect is smaller than the original load spectrum by using the method of approximately equal area area, and use two load levels In the case where the interval frequency is equally divided into upper and lower levels, the damage effect is larger than the original working load spectrum.
  • the calculation process is more complicated to distribute the load frequency reasonably between the two stages.
  • the strengthening load of the traditional 8-level spectrum is graded again to form a 10-level spectrum by using the equal interval method, which reflects the strengthening effect of low load. It is still not possible to control the extent of fatigue life calculation errors caused by the grading method.
  • the technical problem to be solved by the present invention is to provide a material-based SN curve, the program load spectrum amplitude coefficient can change with the random stress load spectrum, can control the calculation error of the graded fatigue life and can obtain the random stress according to the requirements of the graded fatigue life calculation error Random stress load spectrum classification method for load spectrum classification scheme.
  • the present invention also provides a computer-readable storage medium for performing each step in the SN curve-based random stress load spectrum grading method
  • the program load spectrum amplitude coefficient can change with the random stress load spectrum, can control the classification fatigue life calculation error and can obtain the random stress of the random stress load spectrum classification scheme according to the classification fatigue life calculation error requirements Load Spectrum Grading System.
  • the present invention provides a random stress load spectrum classification method based on SN curve, comprising the following steps:
  • the material S-N curve in engineering, it can be estimated according to the ultimate strength of the material to obtain the fatigue life of the first level , and then determine the fatigue life corresponding to other levels according to the fatigue life error control factor;
  • step S1 the count statistics rainflow count statistics.
  • the main function of the rainflow counting method is to simplify the measured load history into several load cycles for fatigue life estimation and fatigue test load spectrum. It is based on the two-parameter method, taking into account the two variables of dynamic strength (amplitude) and static strength (mean value), which conforms to the inherent characteristics of the fatigue load itself.
  • the Goodman formula is used for correction, and the specified mean value is 0.
  • the Goodman formula namely the Goodman diagram, refers to the relationship curve between the average stress and the maximum stress and the minimum stress of the parts subjected to alternating stress under the condition of equal life (equal number of cycles of destruction).
  • S a is the stress amplitude, MPa; S a0 is the equivalent zero mean stress, MPa; S m is the mean stress, MPa; S UTS material ultimate strength, MPa.
  • step S3 when implementing step S3, the following formula (1) is used to determine the fatigue life corresponding to each level;
  • N 1 is the fatigue life corresponding to the first level
  • N i is the fatigue life corresponding to the i level
  • p% is the fatigue life of each level Fatigue life error control factor
  • i is the stage number, according to the above formula (1) and SN curve
  • ⁇ i can be inversely deduced from N i .
  • the tensile strength S UTS of the selected material satisfies: ⁇ max ⁇ S UTS , and ⁇ max is the maximum stress amplitude of the one-dimensional stress spectrum.
  • the maximum stress amplitude ⁇ max of the equivalent 0-mean value should satisfy ⁇ max ⁇ S UTS , adjust S UTS , and re-transform the equivalent 0-mean value until it satisfies
  • the SN curve-based random stress load spectrum grading method is further improved, and the fatigue life error control factor of each level ranges from 0% to 1000%.
  • the reversed stress amplitude is between two adjacent levels of ⁇ i and ⁇ i+1 values, and the frequency of its occurrence is classified as the i-th level or level i+1.
  • the frequency of its occurrence is classified as the i+1th level, and the stress amplitude is ⁇ i+1 .
  • the SN curve-based random stress load spectrum grading method is further improved, and the SN curve is an expression using a power function, an exponential function or a three-parameter power function, or discrete points measured by experiments.
  • the SN curve-based random stress load spectrum classification method is further improved, and the fatigue life error control factors at all levels are equal;
  • the present invention provides a computer-readable storage medium for performing the steps in any one of the above-mentioned SN curve-based random stress load spectrum classification methods.
  • the present invention provides a random stress load spectrum grading system based on SN curve, which can be realized by means of computer programming technology, including:
  • a statistics module which is used to count and count the random stress load spectrum of the time history, and obtain the two-dimensional stress spectrum of the mean and amplitude;
  • a correction module which is used to select the ultimate strength of the material to perform correction, and the two-dimensional stress spectrum is equivalent to a one-dimensional stress spectrum with a specified mean value;
  • the fatigue life determination module obtains the first level according to the maximum stress amplitude in the one-dimensional stress spectrum of the equivalent specified mean value (that is, the stress amplitude of the first level) and the material S-N curve (in engineering, it can be estimated according to the ultimate strength of the material) Fatigue life, and then determine the fatigue life corresponding to other levels according to the fatigue life error control factor;
  • a stress amplitude calculation module which is used to deduce the stress amplitude according to the fatigue life and the SN curve, which is the amplitude of each level;
  • a division module which divides the stress amplitude and frequency in the one-dimensional stress spectrum into corresponding different levels
  • the occurrence frequency of each level of stress amplitude is obtained statistically to form a random stress load spectrum classification.
  • the count statistics rainflow count statistics are corrected by Goodman formula, and the specified mean value is 0.
  • the fatigue life determination module uses the following formula (1) to determine the corresponding fatigue life of each level;
  • N 1 is the fatigue life corresponding to the first level
  • N i is the fatigue life corresponding to the i-th level
  • p% is the fatigue life error control factor of each level
  • i is the level number.
  • the tensile strength S UTS of the selected material satisfies: ⁇ max ⁇ S UTS , ⁇ max is the maximum stress amplitude of the one-dimensional stress spectrum .
  • the SN curve-based random stress load spectrum grading system is further improved, and the fatigue life error control factor of each level ranges from 0% to 1000%.
  • the SN curve-based random stress load spectrum grading system is further improved, and the inverse derivation stress amplitude is between two adjacent values of ⁇ i and ⁇ i+1 , and the frequency of its occurrence is classified as Level i or level i+1.
  • the SN curve-based random stress load spectrum grading system is further improved, and the SN curve is an expression using a power function, an exponential function or a three-parameter power function, or discrete points measured by experiments.
  • the SN curve-based random stress load spectrum grading system is further improved, and the fatigue life error control factors at all levels are equal;
  • the present invention introduces the fatigue life error control factor p% based on the SN curve of the material.
  • the stress amplitude corresponding to the i-th level is ⁇ i
  • the corresponding fatigue life is N i
  • the classification is carried out according to formula (1)
  • the fatigue life ratio corresponding to the stress amplitude of two adjacent levels is a fixed value (1+p%) , so that the fatigue calculation error generated by the classification method can be controlled within p%, and then different random stress load spectrum classification schemes can be obtained according to the requirements of different fatigue life calculation errors.
  • Fig. 1 is a schematic flow chart of the present invention.
  • Embodiments of the present invention are described below through specific examples, and those skilled in the art can fully understand other advantages and technical effects of the present invention from the content disclosed in this specification.
  • the present invention can also be implemented or applied through different specific implementation modes, and various details in this specification can also be applied based on different viewpoints, and various modifications or changes can be made without departing from the general design idea of the invention. It should be noted that, in the case of no conflict, the following embodiments and features in the embodiments can be combined with each other.
  • the following exemplary embodiments of the invention may be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the technical solutions of these exemplary specific embodiments to those skilled in the art.
  • the present invention provides a kind of random stress load spectrum classification method based on SN curve, comprises the following steps:
  • the material S-N curve in engineering, it can be estimated according to the ultimate strength of the material to obtain the fatigue life of the first level , and then determine the fatigue life corresponding to other levels according to the fatigue life error control factor;
  • the invention provides a random stress load spectrum classification method based on the SN curve, comprising the following steps:
  • S a is the stress amplitude, MPa;
  • S a0 is the equivalent zero mean stress, MPa;
  • S m is the stress mean value, MPa;
  • the maximum stress amplitude of the equivalent 0-mean value is ⁇ max , satisfying ⁇ max ⁇ S UTS , if not satisfied, adjust S UTS , and perform the equivalent 0-mean conversion again until it is satisfied;
  • N 1 is the fatigue life corresponding to the first level
  • N i is the fatigue life corresponding to the i-th level
  • p% is the fatigue life error control factor of each level, the range of p% is 0% to 1000%
  • i is the level number;
  • the frequency of its occurrence is classified as the i-th level or the i+1-th level.
  • the SN curve is an expression using a power function, an exponential function or a three-parameter power function, or discrete points measured by experiments.
  • the fatigue life error control factors at all levels are equal; or, the fatigue life error control factors at all levels are not equal.
  • the present invention provides a computer-readable storage medium for performing the steps in the SN curve-based random stress load spectrum grading method described in any one of the first embodiment or the second embodiment.
  • the present invention provides a random stress load spectrum classification system based on SN curve, which can be realized by means of computer programming technology, including:
  • Statistical module it is used for carrying out counting statistics to the random stress load spectrum of time history, obtains the two-dimensional stress spectrum of mean value and amplitude;
  • a correction module which is used to select the ultimate strength of the material to perform correction, and the two-dimensional stress spectrum is equivalent to a one-dimensional stress spectrum with a specified mean value;
  • the fatigue life determination module obtains the first level according to the maximum stress amplitude in the one-dimensional stress spectrum of the equivalent specified mean value (that is, the stress amplitude of the first level) and the material S-N curve (in engineering, it can be estimated according to the ultimate strength of the material) Fatigue life, and then determine the fatigue life corresponding to other levels according to the fatigue life error control factor;
  • a stress amplitude calculation module which is used to deduce the stress amplitude according to the fatigue life and the SN curve, which is the amplitude of each level;
  • a division module which divides the stress amplitude and frequency in the one-dimensional stress spectrum into corresponding different levels
  • the occurrence frequency of each level of stress amplitude is obtained statistically to form a random stress load spectrum classification.
  • the present invention provides a random stress load spectrum classification system based on SN curve, which can be realized by means of computer programming technology, including:
  • a statistics module which is used to perform rainflow counting statistics on the random stress load spectrum of the time history, and obtain the two-dimensional stress spectrum of the mean value and amplitude;
  • a correction module which selects the ultimate strength of the material and uses the Goodman formula to perform correction, and the two-dimensional stress spectrum is equivalent to a one-dimensional stress spectrum with a mean value of 0; the equivalent formula is as follows (2);
  • S a is the stress amplitude, MPa;
  • S a0 is the equivalent zero mean stress, MPa;
  • S m is the stress mean value, MPa;
  • the maximum stress amplitude of the equivalent 0-mean value is ⁇ max , satisfying ⁇ max ⁇ S UTS , if not satisfied, adjust S UTS , and perform the equivalent 0-mean conversion again until it is satisfied;
  • Fatigue life determination module which obtains the first one according to the maximum stress amplitude (that is, the stress amplitude of the first level) and the material S-N curve (in engineering, it can be estimated according to the ultimate strength of the material) in the one-dimensional stress spectrum of the equivalent specified mean value. level, and then determine the corresponding fatigue life of other levels according to the fatigue life error control factor;
  • N 1 is the fatigue life corresponding to the first level
  • N i is the fatigue life corresponding to the i-th level
  • p% is the fatigue life error control factor of each level, the range of p% is 0% to 1000%
  • i is the level number;
  • a stress amplitude calculation module which is used to deduce the stress amplitude according to the fatigue life and the SN curve, which is the amplitude of each level;
  • a division module which divides the stress amplitude and frequency in the one-dimensional stress spectrum into corresponding different levels
  • the occurrence frequency of each level of stress amplitude is obtained statistically to form a random stress load spectrum classification.
  • the frequency of occurrence of the inverse deduced stress amplitude value between adjacent two levels of ⁇ i and ⁇ i+1 is classified as the i-th level or the i+1-th level.
  • the SN curve is an expression using a power function, an exponential function or a three-parameter power function, or discrete points measured by experiments.
  • the fatigue life error control factors at all levels are equal; or, the fatigue life error control factors at all levels are not equal.

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Abstract

本发明公开了一种基于SN曲线的随机应力载荷谱分级方法，包括：对时间历程的随机应力载荷谱进行计数统计，得到均值和幅值的二维应力谱；选择材料极限强度执行修正，将所述二维应力谱等效为指定均值的一维应力谱；根据等效的指定均值的一维应力谱中的最大应力幅值、材料S-N曲线得到第一级的疲劳寿命，确定其它各级对应的疲劳寿命；根据所述疲劳寿命和SN曲线反推出应力幅值，获得每一级的应力幅值；将一维应力谱中的应力幅值及频次划分到对应的不同级中,统计每一级应力幅值的频次，完成随机应力载荷谱的分级。本发明还公开了一种用于各类车辆底盘载荷计算中使用的基于SN曲线的随机应力载荷谱分级系统和一种计算机可读存储介质。

Description

基于SN曲线的随机应力载荷谱分级方法、系统和存储介质 技术领域
本发明涉及交通运输领域，特别涉及一种用于各类车辆底盘载荷计算中使用的基于SN曲线的随机应力载荷谱分级方法；以及，一种用于各类车辆底盘载荷计算中使用的基于SN曲线的随机应力载荷谱分级系统，一种用于执行所述基于SN曲线的随机应力载荷谱分级方法中各步骤的计算机可读存储介质。
背景技术
SN曲线是以材料标准试件疲劳强度为纵坐标，以疲劳寿命的对数值lg N为横坐标，表示一定循环特征下标准试件的疲劳强度与疲劳寿命之间关系的曲线，也称应力－寿命曲线。
在程序加载试验中，需要将随机载荷频谱用程序载荷谱来模拟，一般可以编制4～16级的程序载荷谱，这要根据载荷谱水平和级数对疲劳寿命的影响大小而定。一般来说，试验寿命与随机载荷谱的误差，4级载荷谱要比8级载荷谱大，而超过8级的载荷谱则和8级载荷谱极为相近，一般用8级程序载荷谱。8级程序载荷谱中各级载荷大小的划分一般有等间隔法和幅值比(某级载荷值与最大载荷值之比)系数法，常按Conover幅值比系数1.0、0.95、0.85、0.725、0.575、0.425、0.275、0.125分级。
现有技术用8级程序载荷谱来模拟随机载荷谱，比值系数采用固定值，该比值系数与随机载荷谱的特性无关。对于一些特殊的随机载荷谱，会产生较大的误差。疲劳寿命对数值大的幅值比较敏感，对数值大的幅值分较多的级数能够减小疲劳计算的误差。而现有技术中的幅值比值系数固定，不能够在数值大的幅值范围分更多的级数，且不能控制由分级引起的疲劳寿命误差的大小。现有技术的解决方案是：同时考虑载荷和频次的影响，对两载荷级间的频次进行分配，改善了用区域面积近似相等方法使损伤效应比原载荷谱小的情况，和用两载荷级间频次上下两级平分使损伤效应比原工作载荷谱大的情况。对两级间的载荷频次进行合理分配，计算过程较复杂。采用等间隔法将传统8级谱的强化载荷再次分级形成10级谱，反映了低载荷的强化效应。仍然无法控制由分级方法引起疲劳寿命计算误差的范围。
发明内容
在发明内容部分中引入了一系列简化形式的概念,该简化形式的概念均为本领域现有技术简化，这将在具体实施方式部分中进一步详细说明。本发明的发明内容部分并不意味着要试图限定出所要求保护的技术方案的关键特征和必要技术特征，更不意味着试图确定所要求保护的技术方案的保护范围。
本发明要解决的技术问题是提供一种基于材料的SN曲线，程序载荷谱幅值系数能随随机应力载荷谱变化，能控制分级疲劳寿命计算误差并能根据分级疲劳寿命计算误差要求获得随机应力载荷谱分级方案的随机应力载荷谱分级方法。
相应的，本发明还提供了一种用于执行所述基于SN曲线的随机应力载荷谱分级方法中各步骤的计算机可读存储介质；
以及，一种基于材料的SN曲线，程序载荷谱幅值系数能随随机应力载荷谱变化，能控制分级疲劳寿命计算误差并能根据分级疲劳寿命计算误差要求获得随机应力载荷谱分级方案的随机应力载荷谱分级系统。
为解决上述技术问题，本发明提供一种基于SN曲线的随机应力载荷谱分级方法，包括以下步骤：
S1，对时间历程的随机应力载荷谱进行计数统计，得到均值和幅值的二维应力谱；
S2，选择材料极限强度执行修正，将所述二维应力谱等效为指定均值的一维应力谱；
S3，根据等效的指定均值的一维应力谱中的最大应力幅值(即第一级的应力幅值)、材料S-N曲线(工程上可根据材料极限强度估算)得到第一级的疲劳寿命，然后根据疲劳寿命误差控制因子确定其它各级对应的疲劳寿命；
S4，根据所述疲劳寿命和SN曲线反推出应力幅值，获得每一级的应力幅值；
S5，将一维应力谱中的应力幅值及频次划分到对应的不同级中,统计每一级应力幅值的频次，完成随机应力载荷谱的分级。
可选择的，进一步改进所述基于SN曲线的随机应力载荷谱分级方法，步骤S1中，所述计数统计雨流计数统计。雨流计数法的主要功能是把实测载荷历程简化为若干个载荷循环，供疲劳寿命估算和编制疲劳试验载荷谱使用。它以双参数法为基础，考虑了动强度(幅值)和静强度(均值)两个变量，符合疲劳载荷本身固有的特性。
可选择的，进一步改进所述基于SN曲线的随机应力载荷谱分级方法，步骤S2中， 采用Goodman公式修正，所述指定均值为0。Goodman公式，即古德曼曲线(Goodman diagram)指受交变应力的零件，在等寿命(等破环循环次数)的条件下，其平均应力与最大应力和最小应力的关系曲线。
等效公式如下述公式(2)；
S a0＝S a/(1-S m/S UTS)    公式(2)；
S a为应力幅值，MPa；S a0为等效0均值应力，MPa；S m应力均值，MPa；S UTS材料极限强度，MPa。
可选择的，进一步改进所述基于SN曲线的随机应力载荷谱分级方法，实施步骤S3时，采用以下公式(1)确定每一级对应的疲劳寿命；
N i＝N i-1*(1+p％)＝N 1*(1+p％) (i-1)    公式(1)；
示例性的说明，取第1级的应力幅值σ 1＝σ max，根据SN曲线，N 1为第一级对应的疲劳寿命，N i为第i级对应的疲劳寿命,p％为各级疲劳寿命误差控制因子，i为级序号，依据上述公式(1)和SN曲线，由N i可反推出σ i。
可选择的，进一步改进所述基于SN曲线的随机应力载荷谱分级方法，所选材料的抗拉强度S UTS满足：σ max≤S UTS，σ max为一维应力谱的最大应力幅值。
即，等效0均值的最大应力幅值σ max，应满足σ max≤S UTS，调整S UTS，重新进行等效0均值转换，直至满足
可选择的，进一步改进所述基于SN曲线的随机应力载荷谱分级方法，所述各级疲劳寿命误差控制因子范围为0％～1000％。
可选择的，进一步改进所述基于SN曲线的随机应力载荷谱分级方法，所述反推出应力幅值相邻两级σ i、σ i+1数值之间，将其出现的频次归为第i级或第i+1级。
示例性的，应力幅值数值在相邻两级σ i、σ i+1数值之间，将其出现的频次归为第i+1级，应力幅值为σ i+1。
可选择的，进一步改进所述基于SN曲线的随机应力载荷谱分级方法，所述SN曲线是采用幂函数、指数函数或三参数幂函数的表达式，或试验测得的离散点。
示例性的，SN曲线的关系为幂函数，σ m·N＝C，N为疲劳寿命；m为指数，对于结构钢，一般取5～10；C为常数，可由m、S UTS确定。
可选择的，进一步改进所述基于SN曲线的随机应力载荷谱分级方法，所述各级疲劳寿命误差控制因子相等；
或，所述各级疲劳寿命误差控制因子不相等。
为解决上述技术问题，本发明提供一种用于执行上述任意一项所述基于SN曲线的随机应力载荷谱分级方法中步骤的计算机可读存储介质。
为解决上述技术问题，本发明提供一种基于SN曲线的随机应力载荷谱分级系统，其能通过计算机编程技术手段实现，包括：
统计模块，其用于对时间历程的随机应力载荷谱进行计数统计，得到均值和幅值的二维应力谱；
修正模块，其用于选择材料极限强度执行修正，将所述二维应力谱等效为指定均值为的一维应力谱；
疲劳寿命确定模块，根据等效的指定均值的一维应力谱中的最大应力幅值(即第一级的应力幅值)、材料S-N曲线(工程上可根据材料极限强度估算)得到第一级的疲劳寿命，然后根据疲劳寿命误差控制因子确定其它各级对应的疲劳寿命；
应力幅值计算模块，其用于根据所述疲劳寿命和SN曲线反推出应力幅值，即为每一级的幅值；
划分模块，其将一维应力谱中的应力幅值及频次划分到对应的不同级中；
分级模块，统计获得每一级应力幅值出现频次形成随机应力载荷谱分级。
可选择的，进一步改进所述基于SN曲线的随机应力载荷谱分级系统，所述计数统计雨流计数统计，采用Goodman公式修正，所述指定均值为0。
可选择的，进一步改进所述所述基于SN曲线的随机应力载荷谱分级系统，疲劳寿命确定模块采用以下公式(1)确定每一级对应的疲劳寿命；
N i＝N i-1*(1+p％)＝N 1*(1+p％) (i-1)    公式(1)；
N 1为第一级对应的疲劳寿命，N i为第i级对应的疲劳寿命,p％为各级疲劳寿命误差控制因子，i为级序号。
可选择的，进一步改进所述所述基于SN曲线的随机应力载荷谱分级系统，所选材料的抗拉强度S UTS满足：σ max≤S UTS，σ max为一维应力谱的最大应力幅值。
可选择的，进一步改进所述所述基于SN曲线的随机应力载荷谱分级系统，所述各级疲劳寿命误差控制因子范围为0％～1000％。
可选择的，进一步改进所述所述基于SN曲线的随机应力载荷谱分级系统，所述反推出应力幅值相邻两级σ i、σ i+1数值之间，将其出现的频次归为第i级或第i+1级。
可选择的，进一步改进所述所述基于SN曲线的随机应力载荷谱分级系统，所述SN曲线是采用幂函数、指数函数或三参数幂函数的表达式，或试验测得的离散点。
可选择的，进一步改进所述所述基于SN曲线的随机应力载荷谱分级系统，所述各级疲劳寿命误差控制因子相等；
或，所述各级疲劳寿命误差控制因子不相等。
本发明基于材料的SN曲线，引入疲劳寿命误差控制因子p％。将第i级对应的应力幅值为σ i，对应的疲劳寿命为N i，根据公式(1)进行分级，相邻两级应力幅值对应的疲劳寿命比值为定值(1+p％)，这样可控制由分级方法产生的疲劳计算误差在p％以内，进而是实现根据不同的疲劳寿命计算误差的要求，得到不同的随机应力载荷谱分级方案。
附图说明
本发明附图旨在示出根据本发明的特定示例性实施例中所使用的方法、结构和/或材料的一般特性，对说明书中的描述进行补充。然而，本发明附图是未按比例绘制的示意图，因而可能未能够准确反映任何所给出的实施例的精确结构或性能特点，本发明附图不应当被解释为限定或限制由根据本发明的示例性实施例所涵盖的数值或属性的范围。下面结合附图与具体实施方式对本发明作进一步详细的说明：
图1是本发明流程示意图。
具体实施方式
以下通过特定的具体实施例说明本发明的实施方式，本领域技术人员可由本说明书所公开的内容充分地了解本发明的其他优点与技术效果。本发明还可以通过不同的具体实施方式加以实施或应用，本说明书中的各项细节也可以基于不同观点加以应用，在没有背离发明总的设计思路下进行各种修饰或改变。需说明的是，在不冲突的情况下，以下实施例及实施例中的特征可以相互组合。本发明下述示例性实施例可以多种不同的形式来实施，并且不应当被解释为只限于这里所阐述的具体实施例。应当理解的是，提供这些实施例是为了使得本发明的公开彻底且完整，并且将这些示例性具体实施例的技术方案充分传达给本领域技术人员。
第一实施例；
参考图1所示，本发明提供一种基于SN曲线的随机应力载荷谱分级方法，包括以下步骤：
S1，对时间历程的随机应力载荷谱进行计数统计，得到均值和幅值的二维应力谱；
S2，选择材料极限强度执行修正，将所述二维应力谱等效为指定均值的一维应力谱；
S3，根据等效的指定均值的一维应力谱中的最大应力幅值(即第一级的应力幅值)、材料S-N曲线(工程上可根据材料极限强度估算)得到第一级的疲劳寿命，然后根据疲劳寿命误差控制因子确定其它各级对应的疲劳寿命；
S4，根据所述疲劳寿命和SN曲线反推出应力幅值，获得每一级的应力幅值；
S5，将一维应力谱中的应力幅值及频次划分到对应的不同级中,统计每一级应力幅值的频次，完成随机应力载荷谱的分级。
第二实施例；
本发明提供一种基于SN曲线的随机应力载荷谱分级方法，包括以下步骤：
S1，对时间历程的随机应力载荷谱进行雨流计数统计，得到均值和幅值的二维应力谱；
S2，选择材料极限强度采用Goodman公式执行修正，将所述二维应力谱等效为均值为0的一维应力谱；等效公式如下述公式(2)；
S a0＝S a/(1-S m/S UTS)    公式(2)；
S a为应力幅值，MPa；S a0为等效0均值应力，MPa；S m应力均值，MPa；S UTS材料极限强度，MPa；
等效0均值的最大应力幅值为σ max，满足σ max≤S UTS，如不满足，调整S UTS，重新进行等效0均值转换，直至满足；
S3，根据每一级应力幅值的、材料极限强度和疲劳寿命误差控制因子确定每一级对应的疲劳寿命；采用以下公式(1)确定每一级对应的疲劳寿命；
N i＝N i-1*(1+p％)＝N 1*(1+p％) (i-1)    公式(1)；
N 1为第一级对应的疲劳寿命，N i为第i级对应的疲劳寿命,p％为各级疲劳寿命误差控制因子，p％的范围为0％～1000％，i为级序号；
S4，根据所述疲劳寿命和SN曲线反推出应力幅值；
S5，将一维应力谱中的应力幅值及频次划分到对应的不同级中,统计每一级应力幅值的频次，完成随机应力载荷谱的分级。
可选择的，上述第二实施例中，所述反推出应力幅值相邻两级σ i、σ i+1数值之间，将其出现的频次归为第i级或第i+1级。
可选择的，上述第二实施例中，所述SN曲线是采用幂函数、指数函数或三参数幂函数的表达式，或试验测得的离散点。
可选择的，上述第二实施例中，所述各级疲劳寿命误差控制因子相等；或，所述各级疲劳寿命误差控制因子不相等。
第三实施例；
本发明提供一种用于执行第一实施例或第二实施例任意一项所述基于SN曲线的随机应力载荷谱分级方法中步骤的计算机可读存储介质。
第四实施例；
本发明提供一种基于SN曲线的随机应力载荷谱分级系统，其能通过计算机编程技术手段实现，包括：
统计模块，其用于对时间历程的随机应力载荷谱进行计数统计，得到均值和幅值的 二维应力谱；
修正模块，其用于选择材料极限强度执行修正，将所述二维应力谱等效为指定均值的一维应力谱；
疲劳寿命确定模块，根据等效的指定均值的一维应力谱中的最大应力幅值(即第一级的应力幅值)、材料S-N曲线(工程上可根据材料极限强度估算)得到第一级的疲劳寿命，然后根据疲劳寿命误差控制因子确定其它各级对应的疲劳寿命；
应力幅值计算模块，其用于根据所述疲劳寿命和SN曲线反推出应力幅值，即为每一级的幅值；
划分模块，其将一维应力谱中的应力幅值及频次划分到对应的不同级中；
分级模块，统计获得每一级应力幅值出现频次形成随机应力载荷谱分级。
第五实施例；
本发明提供一种基于SN曲线的随机应力载荷谱分级系统，其能通过计算机编程技术手段实现，包括：
统计模块，其用于对时间历程的随机应力载荷谱进行雨流计数统计，得到均值和幅值的二维应力谱；
修正模块，其选择材料极限强度采用Goodman公式执行修正，将所述二维应力谱等效为均值为0的一维应力谱；等效公式如下述公式(2)；
S a0＝S a/(1-S m/S UTS)    公式(2)；
S a为应力幅值，MPa；S a0为等效0均值应力，MPa；S m应力均值，MPa；S UTS材料极限强度，MPa；
等效0均值的最大应力幅值为σ max，满足σ max≤S UTS，如不满足，调整S UTS，重新进行等效0均值转换，直至满足；
疲劳寿命确定模块，其根据等效的指定均值的一维应力谱中的最大应力幅值(即第一级的应力幅值)、材料S-N曲线(工程上可根据材料极限强度估算)得到第一级的疲劳寿命，然后根据疲劳寿命误差控制因子确定其它各级对应的疲劳寿命；
N i＝N i-1*(1+p％)＝N 1*(1+p％) (i-1)    公式(1)；
N 1为第一级对应的疲劳寿命，N i为第i级对应的疲劳寿命,p％为各级疲劳寿命误差控制因子，p％的范围为0％～1000％，i为级序号；
应力幅值计算模块，其用于根据所述疲劳寿命和SN曲线反推出应力幅值，即为每一级的幅值；
划分模块，其将一维应力谱中的应力幅值及频次划分到对应的不同级中；
分级模块，统计获得每一级应力幅值出现频次形成随机应力载荷谱分级。
可选择的，上述第五实施例中，所述反推出应力幅值相邻两级σ i、σ i+1数值之间，将其出现的频次归为第i级或第i+1级。
可选择的，上述第五实施例中，所述SN曲线是采用幂函数、指数函数或三参数幂函数的表达式，或试验测得的离散点。
可选择的，上述第五实施例中，所述各级疲劳寿命误差控制因子相等；或，所述各级疲劳寿命误差控制因子不相等。
除非另有定义，否则这里所使用的全部术语(包括技术术语和科学术语)都具有与本发明所属领域的普通技术人员通常理解的意思相同的意思。还将理解的是，除非这里明确定义，否则诸如在通用字典中定义的术语这类术语应当被解释为具有与它们在相关领域语境中的意思相一致的意思，而不以理想的或过于正式的含义加以解释。
以上通过具体实施方式和实施例对本发明进行了详细的说明，但这些并非构成对本发明的限制。在不脱离本发明原理的情况下，本领域的技术人员还可做出许多变形和改进，这些也应视为本发明的保护范围。

Claims (18)

  1. 一种基于SN曲线的随机应力载荷谱分级方法，其特征在于，包括以下步骤：
    S1，对时间历程的随机应力载荷谱进行计数统计，得到均值和幅值的二维应力谱；
    S2，选择材料极限强度执行修正，将所述二维应力谱等效为指定均值的一维应力谱；
    S3，根据等效的指定均值的一维应力谱中的最大应力幅值、材料S-N曲线得到第一级的疲劳寿命，然后根据疲劳寿命误差控制因子确定其它各级对应的疲劳寿命；
    S4，根据所述疲劳寿命和SN曲线反推出应力幅值，获得每一级的应力幅值；
    S5，将一维应力谱中的应力幅值及频次划分到对应的不同级中,统计每一级应力幅值的频次，完成随机应力载荷谱的分级。
  2. 如权利要求1所述基于SN曲线的随机应力载荷谱分级方法，其特征在于：步骤S1中，所述计数统计是雨流计数统计。
  3. 如权利要求1所述基于SN曲线的随机应力载荷谱分级方法，其特征在于：步骤S2中，采用Goodman公式修正，所述指定均值为0。
  4. 如权利要求1所述基于SN曲线的随机应力载荷谱分级方法，其特征在于：实施步骤S3时，采用以下公式(1)确定每一级对应的疲劳寿命；
    N i＝N i-1*(1+p％)＝N 1*(1+p％) (i-1)     公式(1)；
    N 1为第一级对应的疲劳寿命，N i为第i级对应的疲劳寿命,p％为各级疲劳寿命误差控制因子，i为级序号。
  5. 如权利要求1所述基于SN曲线的随机应力载荷谱分级方法，其特征在于：所选材料的抗拉强度S UTS满足：σ max≤S UTS，σ max为一维应力谱的最大应力幅值。
  6. 如权利要求1所述基于SN曲线的随机应力载荷谱分级方法，其特征在于：所述各级疲劳寿命误差控制因子范围为0％～1000％。
  7. 如权利要求1所述基于SN曲线的随机应力载荷谱分级方法，其特征在于：所述反推出应力幅值相邻两级σ i、σ i+1数值之间，将其出现的频次归为第i级或第i+1级。
  8. 如权利要求1所述基于SN曲线的随机应力载荷谱分级方法，其特征在于：所述SN曲线是采用幂函数、指数函数或三参数幂函数的表达式，或试验测得的离散点。
  9. 如权利要求1所述基于SN曲线的随机应力载荷谱分级方法，其特征在于：所述各级疲劳寿命误差控制因子相等；
    或，所述各级疲劳寿命误差控制因子不相等。
  10. 一种用于执行权利要求1-8任意一项所述基于SN曲线的随机应力载荷谱分级方法中步骤的计算机可读存储介质。
  11. 一种基于SN曲线的随机应力载荷谱分级系统，其特征在于，包括：
    统计模块，其用于对时间历程的随机应力载荷谱进行计数统计，得到均值和幅值的二维应力谱；
    修正模块，其用于选择材料极限强度执行修正，将所述二维应力谱等效为指定均值的一维应力谱；
    疲劳寿命确定模块，根据等效的指定均值的一维应力谱中的最大应力幅值、材料S-N曲线得到第一级的疲劳寿命，然后根据疲劳寿命误差控制因子确定其它各级对应的疲劳寿命；
    应力幅值计算模块，其用于根据所述疲劳寿命和SN曲线反推出应力幅值，即为每一级的幅值；
    划分模块，其将一维应力谱中的应力幅值及频次划分到对应的不同级中；
    分级模块，统计获得每一级应力幅值出现频次形成随机应力载荷谱分级。
  12. 如权利要求10所述基于SN曲线的随机应力载荷谱分级系统，其特征在于：所述计数统计雨流计数统计，采用Goodman公式修正，所述指定均值为0。
  13. 如权利要求10所述基于SN曲线的随机应力载荷谱分级系统，其特征在于：疲劳寿命确定模块采用以下公式(1)确定每一级对应的疲劳寿命；
    N i＝N i-1*(1+p％)＝N 1*(1+p％) (i-1)       公式(1)；
    N 1为第一级对应的疲劳寿命，N i为第i级对应的疲劳寿命,p％为各级疲劳寿命误差控制因子，i为级序号。
  14. 如权利要求10所述基于SN曲线的随机应力载荷谱分级系统，其特征在于：所选材料的抗拉强度S UTS满足：σ max≤S UTS，σ max为一维应力谱的最大应力幅值。
  15. 如权利要求10所述基于SN曲线的随机应力载荷谱分级系统，其特征在于：所述各级疲劳寿命误差控制因子范围为0％～1000％。
  16. 如权利要求10所述基于SN曲线的随机应力载荷谱分级系统，其特征在于：所述反推出应力幅值相邻两级σ i、σ i+1数值之间，将其出现的频次归为第i级或第i+1级。
  17. 如权利要求10所述基于SN曲线的随机应力载荷谱分级系统，其特征在于：所述SN曲线是采用幂函数、指数函数或三参数幂函数的表达式，或试验测得的离散点。
  18. 如权利要求10所述基于SN曲线的随机应力载荷谱分级系统，其特征在于：所述各级疲劳寿命误差控制因子相等；
    或，所述各级疲劳寿命误差控制因子不相等。
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