CN118095019A - A method and device for calculating the vibration fatigue crack growth life of an engine structure - Google Patents
A method and device for calculating the vibration fatigue crack growth life of an engine structure Download PDFInfo
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Abstract
本发明公开一种发动机结构振动疲劳裂纹扩展寿命的计算方法及装置，涉及力学性能测试表征技术领域，以获得可靠的断裂力学参数和裂纹扩展速率曲线，给出准确量化的裂纹扩展寿命，为重复使用发动机寿命评估提供方法指导。所述计算方法包括：获取发动机结构的有限元模型中考核段应力响应的时域随机应力谱；基于时域随机应力谱，对发动机结构的裂纹模型进行有限元分析处理，确定含裂纹结构的断裂力学参数；对按照预设裂纹扩展模式建立的裂纹扩展速率模型进行振动疲劳性能试验，利用参数识别确定裂纹扩展速率模型对应的目标参数值；结合裂纹扩展速率模型对应的参数值以及预设临界裂纹长度值进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。
The present invention discloses a method and device for calculating the vibration fatigue crack growth life of an engine structure, which relates to the technical field of mechanical performance test characterization, in order to obtain reliable fracture mechanics parameters and crack growth rate curves, give an accurately quantified crack growth life, and provide method guidance for the evaluation of the life of a reusable engine. The calculation method includes: obtaining a time-domain random stress spectrum of the stress response of the assessment section in a finite element model of the engine structure; based on the time-domain random stress spectrum, performing finite element analysis processing on the crack model of the engine structure to determine the fracture mechanics parameters of the cracked structure; performing a vibration fatigue performance test on a crack growth rate model established according to a preset crack growth mode, and determining the target parameter value corresponding to the crack growth rate model by using parameter identification; performing crack growth life calculation in combination with the parameter value corresponding to the crack growth rate model and a preset critical crack length value to obtain a target crack growth life.
Description
技术领域Technical Field
本发明涉及力学性能测试表征技术领域，尤其涉及一种发动机结构振动疲劳裂纹扩展寿命的计算方法及装置。The present invention relates to the technical field of mechanical performance test characterization, and in particular to a method and device for calculating the vibration fatigue crack growth life of an engine structure.
背景技术Background technique
重复使用发动机是航天运载动力系统的主要发展方向之一，在重复使用要求下，发动机的疲劳强度设计及寿命评估需求非常突出。传统的疲劳分析方法以应力/应变-寿命曲线（S-N曲线）为基础进行寿命预测，能够给出具有一定可靠度的寿命预测结果。然而，当疲劳分析方法用于重复使用结构时存在以下：S-N曲线寿命模型参数较少，无法完整描述疲劳损伤过程机制；此外，疲劳分析中的载荷因素主要考虑循环应力的大小和发生次数，难以考虑载荷次序对寿命的影响。这会导致寿命预测结果误差较大，不利于结构设计及评估。Reusable engines are one of the main development directions of space launch propulsion systems. Under the requirement of reuse, the fatigue strength design and life assessment of engines are very prominent. Traditional fatigue analysis methods use stress/strain-life curves (S-N curves) as the basis for life prediction, which can provide life prediction results with a certain degree of reliability. However, when fatigue analysis methods are used for reusable structures, the following problems exist: the S-N curve life model has fewer parameters and cannot fully describe the fatigue damage process mechanism; in addition, the load factors in fatigue analysis mainly consider the magnitude and number of occurrences of cyclic stress, and it is difficult to consider the impact of load sequence on life. This will lead to large errors in life prediction results, which is not conducive to structural design and evaluation.
基于断裂力学的损伤容限方法和裂纹扩展技术在航空领域已经广泛应用，目前，主要以线弹性断裂力学方法为主，适用于宏观长裂纹建模、材料性能试验及准静态疲劳寿命计算。液体火箭发动机的振动载荷是其重复使用过程中的显著载荷特征，振动环境下疲劳寿命大部分处于裂纹萌生阶段，为了保证发动机正常工作，需要保持结构完整性，通常不允许出现宏观裂纹或者穿透壁厚的裂纹。因此，基于断裂力学方法对发动机疲劳设计及寿命评估时，应重点考虑振动载荷下的结构响应特征、未穿透壁厚裂纹的损伤模式及有效的性能数据。目前，线弹性断裂力学用于裂纹萌生阶段的未穿透裂纹时存在参数不确定等局限性，另外，传统基于模态法的振动响应计算中直接引入裂纹将无法考虑弹塑性以及其他非线性情况，而裂纹问题的瞬态动力学计算规模和计算效率则限制了其在工程上普遍应用。因此，目前的断裂力学方法难以适应发动机在振动环境下疲劳裂纹寿命评估的需求。Damage tolerance methods and crack propagation techniques based on fracture mechanics have been widely used in the aviation field. At present, the linear elastic fracture mechanics method is mainly used, which is suitable for macroscopic long crack modeling, material performance testing and quasi-static fatigue life calculation. The vibration load of liquid rocket engines is a significant load feature during their repeated use. Most of the fatigue life under vibration environment is in the crack initiation stage. In order to ensure the normal operation of the engine, it is necessary to maintain structural integrity, and macroscopic cracks or cracks that penetrate the wall thickness are usually not allowed. Therefore, when evaluating the fatigue design and life of the engine based on the fracture mechanics method, the structural response characteristics under vibration loads, the damage mode of cracks that do not penetrate the wall thickness, and effective performance data should be considered. At present, there are limitations such as parameter uncertainty when linear elastic fracture mechanics is used for cracks that do not penetrate the crack initiation stage. In addition, the direct introduction of cracks in the traditional vibration response calculation based on the modal method will not be able to consider elastic-plastic and other nonlinear situations, and the transient dynamics calculation scale and calculation efficiency of the crack problem limit its widespread application in engineering. Therefore, the current fracture mechanics method is difficult to meet the needs of fatigue crack life evaluation of engines under vibration environments.
基于此，需要发展一种用于发动机结构振动载荷下疲劳裂纹扩展寿命预测方法，以获得可靠的断裂力学参数和裂纹扩展速率曲线，给出准确量化的裂纹扩展寿命，为重复使用发动机寿命评估提供方法指导。Based on this, it is necessary to develop a method for predicting the fatigue crack growth life under engine structure vibration loads in order to obtain reliable fracture mechanics parameters and crack growth rate curves, give accurate and quantified crack growth life, and provide methodological guidance for the life assessment of reused engines.
发明内容Summary of the invention
本发明的目的在于提供一种发动机结构振动疲劳裂纹扩展寿命的计算方法及装置，以获得可靠的断裂力学参数和裂纹扩展速率曲线，给出准确量化的裂纹扩展寿命，为重复使用发动机寿命评估提供方法指导。The purpose of the present invention is to provide a method and device for calculating the vibration fatigue crack growth life of an engine structure, so as to obtain reliable fracture mechanics parameters and crack growth rate curves, give an accurate and quantified crack growth life, and provide method guidance for the life assessment of a reused engine.
第一方面，本发明提供一种发动机结构振动疲劳裂纹扩展寿命的计算方法，所述计算方法包括：In a first aspect, the present invention provides a method for calculating the vibration fatigue crack growth life of an engine structure, the calculation method comprising:
获取发动机结构的有限元模型中考核段应力响应的时域随机应力谱；Obtain the time domain random stress spectrum of the stress response of the test section in the finite element model of the engine structure;
基于时域随机应力谱，对发动机结构的裂纹模型进行有限元分析处理，确定含裂纹结构的断裂力学参数；Based on the random stress spectrum in the time domain, the crack model of the engine structure is analyzed by finite element method to determine the fracture mechanics parameters of the cracked structure.
对按照预设裂纹扩展模式建立的裂纹扩展速率模型进行振动疲劳性能试验，利用参数识别确定裂纹扩展速率模型对应的目标参数值；Conducting a vibration fatigue performance test on the crack growth rate model established according to the preset crack growth mode, and determining the target parameter value corresponding to the crack growth rate model by using parameter identification;
结合裂纹扩展速率模型对应的参数值以及预设临界裂纹长度值进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。The crack growth life is calculated by combining the parameter values corresponding to the crack growth rate model and the preset critical crack length value to obtain the target crack growth life.
采用上述技术方案的情况下，在获取发动机结构的有限元模型中考核段应力响应的时域随机应力谱之后，基于时域随机应力谱，可以对发动机结构的裂纹模型进行有限元分析处理，从而确定含裂纹结构的断裂力学参数，并对按照预设裂纹扩展模式建立的裂纹扩展速率模型进行振动疲劳性能试验，利用参数识别确定裂纹扩展速率模型对应的目标参数值，最后可以结合裂纹扩展速率模型对应的参数值以及预设临界裂纹长度值进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。基于此，本发明综合了结构随机振动响应计算、振动应力响应时域模拟、裂纹建模及断裂力学参数计算、裂纹扩展速率模型参数及初始裂纹长度确定以及裂纹扩展寿命计算等内容，能够获得结构随机振动稳态响应和时域应力随机谱，给出准确量化的断裂力学参数，基于疲劳性能试验数据确定裂纹扩展速率模型参数及初始裂纹长度，实现结构裂纹扩展寿命计算，克服了传统疲劳分析方法以及线弹性断裂力学的宏观裂纹分析方法用于未穿透厚度裂纹在振动环境下的寿命计算时,机理不清晰、参数获取难、模型不适用导致计算结果偏差大的缺点。When the above technical solution is adopted, after obtaining the time-domain random stress spectrum of the stress response of the assessment section in the finite element model of the engine structure, the crack model of the engine structure can be subjected to finite element analysis based on the time-domain random stress spectrum, so as to determine the fracture mechanics parameters of the cracked structure, and conduct a vibration fatigue performance test on the crack growth rate model established according to the preset crack growth mode, and use parameter identification to determine the target parameter value corresponding to the crack growth rate model, and finally, the crack growth life can be calculated in combination with the parameter value corresponding to the crack growth rate model and the preset critical crack length value to obtain the target crack growth life. Based on this, the present invention integrates the calculation of structural random vibration response, time-domain simulation of vibration stress response, crack modeling and fracture mechanics parameter calculation, crack growth rate model parameters and initial crack length determination, and crack growth life calculation, etc., and can obtain the steady-state response of structural random vibration and the time-domain stress random spectrum, give accurate and quantified fracture mechanics parameters, determine the crack growth rate model parameters and the initial crack length based on fatigue performance test data, and realize the calculation of structural crack growth life, which overcomes the shortcomings of traditional fatigue analysis methods and macro crack analysis methods of linear elastic fracture mechanics when used for life calculation of non-penetrating thickness cracks in a vibration environment, such as unclear mechanism, difficult parameter acquisition, and inapplicable model, resulting in large deviations in calculation results.
由此可知，本发明提供的发动机结构振动疲劳裂纹扩展寿命的计算方法能够获得可靠的断裂力学参数和裂纹扩展速率曲线，给出准确量化的裂纹扩展寿命，为重复使用发动机寿命评估提供方法指导。It can be seen that the calculation method of the engine structure vibration fatigue crack growth life provided by the present invention can obtain reliable fracture mechanics parameters and crack growth rate curves, give accurate and quantified crack growth life, and provide method guidance for the life assessment of repeated-use engines.
第二方面，本发明还提供一种发动机结构振动疲劳裂纹扩展寿命的计算装置，用于实现第一方面的发动机结构振动疲劳裂纹扩展寿命的计算方法，计算装置包括：In a second aspect, the present invention further provides a device for calculating the vibration fatigue crack growth life of an engine structure, which is used to implement the method for calculating the vibration fatigue crack growth life of an engine structure of the first aspect, and the calculation device comprises:
获取模块，用于获取发动机结构的有限元模型中考核段应力响应的时域随机应力谱；An acquisition module, used to acquire a time-domain random stress spectrum of the stress response of the test section in the finite element model of the engine structure;
第一确定模块，用于基于时域随机应力谱，对发动机结构的裂纹模型进行有限元分析处理，确定含裂纹结构的断裂力学参数；The first determination module is used to perform finite element analysis on the crack model of the engine structure based on the time domain random stress spectrum to determine the fracture mechanics parameters of the cracked structure;
第二确定模块，用于对按照预设裂纹扩展模式建立的裂纹扩展速率模型进行振动疲劳性能试验，利用参数识别确定裂纹扩展速率模型对应的目标参数值；A second determination module is used to perform a vibration fatigue performance test on a crack growth rate model established according to a preset crack growth mode, and determine a target parameter value corresponding to the crack growth rate model by using parameter identification;
获得模块，用于结合裂纹扩展速率模型对应的参数值以及预设临界裂纹长度值进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。The acquisition module is used to calculate the crack growth life by combining the parameter values corresponding to the crack growth rate model and the preset critical crack length value to obtain the target crack growth life.
可选的，获取模块包括：Optionally, the acquisition module includes:
第一建立单元，用于建立发动机结构的有限元模型；A first building unit is used to build a finite element model of the engine structure;
第一确定单元，用于对发动机结构的有限元模型施加随机振动载荷激励，确定考核段应力响应的功率谱密度；The first determination unit is used to apply random vibration load excitation to the finite element model of the engine structure to determine the power spectrum density of the stress response of the assessment section;
第一获得单元，用于对功率谱密度进行抽样处理，获得考核段应力响应的时域随机应力谱。The first obtaining unit is used to perform sampling processing on the power spectrum density to obtain the time domain random stress spectrum of the stress response of the assessment section.
可选的，第一获得单元包括：Optionally, the first obtaining unit includes:
获取子单元，用于获取功率谱密度对应的应力幅值概率密度函数；An acquisition subunit is used to obtain a stress amplitude probability density function corresponding to a power spectrum density;
获得子单元，用于基于应力幅值概率密度函数以及峰值概率密度函数，对时域应力响应进行抽样处理，获得应力响应样本；An acquisition subunit is used to perform sampling processing on the time domain stress response based on the stress amplitude probability density function and the peak value probability density function to obtain a stress response sample;
确定子单元，用于对应力响应样本进行随机化处理，确定考核段应力响应的时域随机应力谱。A subunit is determined to perform random processing on the stress response samples and determine the time-domain random stress spectrum of the stress response of the assessment section.
可选的，第一确定模块包括：Optionally, the first determining module includes:
第二建立单元，用于建立发动机结构的裂纹模型；A second establishing unit is used to establish a crack model of the engine structure;
第二确定单元，用于基于时域随机应力谱，确定施加于裂纹模型的外载荷；a second determination unit, for determining an external load applied to the crack model based on the time-domain random stress spectrum;
第三确定单元，用于对施加了外载荷的裂纹模型进行弹-塑性有限元分析处理，确定各个裂纹长度对应的断裂力学参数。The third determination unit is used to perform elastic-plastic finite element analysis on the crack model to which the external load is applied, and determine the fracture mechanics parameters corresponding to each crack length.
可选的，断裂力学参数至少包括应力强度因子或J积分。Optionally, the fracture mechanics parameters include at least a stress intensity factor or a J-integral.
可选的，第二确定模块包括：Optionally, the second determining module includes:
第三建立单元，用于按照预设裂纹扩展模式建立裂纹扩展速率模型；A third establishing unit is used to establish a crack growth rate model according to a preset crack growth mode;
获取单元，用于获取发动机结构的振动疲劳应力-寿命试验曲线或振动疲劳应变-寿命试验曲线；An acquisition unit, used for acquiring a vibration fatigue stress-life test curve or a vibration fatigue strain-life test curve of an engine structure;
第四确定单元，用于基于振动疲劳应力-寿命试验曲线或振动疲劳应变-寿命试验曲线，结合初始裂纹长度和裂纹扩展速率参数的初始值，确定试验裂纹扩展寿命；A fourth determination unit is used to determine the test crack growth life based on the vibration fatigue stress-life test curve or the vibration fatigue strain-life test curve in combination with the initial crack length and the initial value of the crack growth rate parameter;
第五确定单元，用于利用参数优化的方法，对裂纹扩展速率参数的初始值进行优化，确定误差最小的参数值为裂纹扩展速率模型对应的参数值。The fifth determining unit is used to optimize the initial value of the crack growth rate parameter by using a parameter optimization method, and determine the parameter value with the smallest error as the parameter value corresponding to the crack growth rate model.
可选的，裂纹扩展速率模型，包括：Optional, crack growth rate models, including:
， ,
其中，其中，a为裂纹长度，N为循环次数，C，n，p，q为待定的模型参数值，f为裂纹张开/闭合函数，R为应力比，ΔK为应力强度因子幅值，ΔKth为裂纹扩展门槛值，Kmax为应力强度因子峰值，KC为断裂韧度。Among them, a is the crack length, N is the number of cycles, C, n, p, q are the values of the model parameters to be determined, f is the crack opening/closing function, R is the stress ratio, ΔK is the stress intensity factor amplitude, ΔKth is the crack extension threshold, Kmax is the stress intensity factor peak, and KC is the fracture toughness.
可选的，获得模块包括：Optionally, the acquisition module includes:
第二获得单元，用于结合时域随机应力谱、断裂力学参数、裂纹扩展速率模型对应的目标参数值以及预设临界裂纹长度值，利用循环接循环的方法或块谱平均寿命计算法进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。The second acquisition unit is used to combine the time domain random stress spectrum, fracture mechanics parameters, target parameter values corresponding to the crack growth rate model and the preset critical crack length value, and calculate the crack growth life using the cycle-by-cycle method or the block spectrum average life calculation method to obtain the target crack growth life.
第二方面提供的发动机结构振动疲劳裂纹扩展寿命的计算装置的有益效果与第一方面的实现方式描述的发动机结构振动疲劳裂纹扩展寿命的计算方法的有益效果相同，此处不做赘述。The beneficial effects of the device for calculating the vibration fatigue crack growth life of the engine structure provided in the second aspect are the same as the beneficial effects of the method for calculating the vibration fatigue crack growth life of the engine structure described in the implementation of the first aspect, and will not be repeated here.
附图说明BRIEF DESCRIPTION OF THE DRAWINGS
此处所说明的附图用来提供对本发明的进一步理解，构成本发明的一部分，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:
图1为本发明实施例中提供的一种发动机结构振动疲劳裂纹扩展寿命的计算方法的步骤流程图；FIG1 is a flowchart of a method for calculating the vibration fatigue crack growth life of an engine structure provided in an embodiment of the present invention;
图2为本发明实施例中提供的另一种发动机结构振动疲劳裂纹扩展寿命的计算方法的步骤流程图；FIG2 is a flowchart of another method for calculating the vibration fatigue crack growth life of an engine structure provided in an embodiment of the present invention;
图3为本发明实施例的结构考核部位及其振动应力响应功率谱密度曲线；FIG3 is a power spectrum density curve of the structural assessment part and its vibration stress response according to an embodiment of the present invention;
图4（a）为应力响应的典型窄带分布曲线；Figure 4 (a) shows a typical narrow-band distribution curve of stress response;
图4（b）为应力响应的典型宽带分布曲线；Figure 4(b) shows a typical broadband distribution curve of stress response;
图5为本发明实施例中时域应力随机谱示意图；FIG5 is a schematic diagram of a random stress spectrum in the time domain according to an embodiment of the present invention;
图6为本发明实施例中发动机结构的裂纹模型示意图；FIG6 is a schematic diagram of a crack model of an engine structure according to an embodiment of the present invention;
图7为本发明实施例中表面裂纹示意图；FIG7 is a schematic diagram of a surface crack in an embodiment of the present invention;
图8为本发明实施例中裂纹扩展速率模型参数及初始裂纹长度确定示意图；FIG8 is a schematic diagram of determining crack growth rate model parameters and initial crack length in an embodiment of the present invention;
图9为本发明实施例发动机结构振动疲劳裂纹扩展寿命的计算装置示意图。FIG. 9 is a schematic diagram of a device for calculating the vibration fatigue crack growth life of an engine structure according to an embodiment of the present invention.
具体实施方式Detailed ways
为了便于清楚描述本发明实施例的技术方案，在本发明的实施例中，采用了“第一”、“第二”等字样对功能和作用基本相同的相同项或相似项进行区分。例如，第一阈值和第二阈值仅仅是为了区分不同的阈值，并不对其先后顺序进行限定。本领域技术人员可以理解“第一”、“第二”等字样并不对数量和执行次序进行限定，并且“第一”、“第二”等字样也并不限定一定不同。In order to facilitate the clear description of the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, the words "first", "second" and the like are used to distinguish the same items or similar items with substantially the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and do not limit their order. Those skilled in the art can understand that the words "first", "second" and the like do not limit the quantity and execution order, and the words "first", "second" and the like do not necessarily limit them to be different.
需要说明的是，本发明中，“示例性的”或者“例如”等词用于表示作例子、例证或说明。本发明中被描述为“示例性的”或者“例如”的任何实施例或设计方案不应被解释为比其他实施例或设计方案更优选或更具优势。确切而言，使用“示例性的”或者“例如”等词旨在以具体方式呈现相关概念。It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.
本发明中，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B的情况，其中A，B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。“以下至少一项（个）”或其类似表达，是指的这些项中的任意组合，包括单项（个）或复数项（个）的任意组合。例如，a，b或c中的至少一项（个），可以表示：a，b，c，a和b的结合，a和c的结合，b和c的结合，或a、b和c的结合，其中a，b，c可以是单个，也可以是多个。In the present invention, "at least one" means one or more, and "plurality" means two or more. "And/or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and/or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character "/" generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.
如图1所示，本发明实施例提供一种发动机结构振动疲劳裂纹扩展寿命的计算方法，包括：As shown in FIG1 , an embodiment of the present invention provides a method for calculating the vibration fatigue crack growth life of an engine structure, comprising:
S101：获取发动机结构的有限元模型中考核段应力响应的时域随机应力谱。S101: Obtain a time-domain random stress spectrum of a stress response of an assessment section in a finite element model of an engine structure.
在本申请中，采用有限元方法对结构进行动力学建模，施加随机振动载荷激励得到考核部位应力响应的功率谱密度（Power Spectrum Density，PSD）和均方根值（RootMean Square，RMS）等动响应 。In this application, the finite element method is used to perform dynamic modeling of the structure, and random vibration load excitation is applied to obtain dynamic responses such as the power spectrum density (PSD) and root mean square (RMS) of the stress response of the test part.
根据获得的振动应力响应的功率谱密度，分析给出时域应力响应幅值和峰值的概率密度函数，然后抽样获得应力响应时域随机数，并形成时域随机应力谱。According to the power spectrum density of the vibration stress response obtained, the probability density function of the time domain stress response amplitude and peak value is analyzed and given, and then the time domain random number of the stress response is sampled to form a time domain random stress spectrum.
S102：基于时域随机应力谱，对发动机结构的裂纹模型进行有限元分析处理，确定含裂纹结构的断裂力学参数。S102: Based on the time-domain random stress spectrum, a finite element analysis is performed on the crack model of the engine structure to determine the fracture mechanics parameters of the cracked structure.
具体的，首先假设裂纹扩展模式，给定裂纹形式，并设定裂纹扩展路径。然后，对发动机结构进行裂纹建模，结构裂纹模型主要考虑两点：一是能够包络从初始裂纹到临界裂纹长度的扩展范围；二是包含对未穿透厚度裂纹的断裂力学参数有影响的主要结构特征，如圆角、开孔及变厚度等。最后，选取时域随机应力谱中载荷点作为外载荷施加于裂纹模型进行线弹性或弹-塑性有限元计算，得到各个裂纹长度ai对应的断裂力学参数Ki（应力强度因子）或Ji（J积分）。Specifically, first assume the crack propagation mode, give the crack form, and set the crack propagation path. Then, the engine structure is crack modeled. The structural crack model mainly considers two points: one is that it can envelop the extension range from the initial crack to the critical crack length; the other is that it contains the main structural features that affect the fracture mechanics parameters of non-penetrating thickness cracks, such as fillets, openings, and variable thickness. Finally, the load points in the time domain random stress spectrum are selected as external loads to be applied to the crack model for linear elastic or elastic-plastic finite element calculations to obtain the fracture mechanics parameters Ki (stress intensity factor) or Ji (J integral) corresponding to each crack length ai.
S103：对按照预设裂纹扩展模式建立的裂纹扩展速率模型进行振动疲劳性能试验，利用参数识别确定裂纹扩展速率模型对应的目标参数值。S103: performing a vibration fatigue performance test on the crack growth rate model established according to the preset crack growth mode, and determining a target parameter value corresponding to the crack growth rate model by using parameter identification.
具体的，首先，获取材料或结构件在振动载荷下的疲劳应力-寿命曲线或应变-寿命曲线等振动疲劳性能试验数据，给定裂纹扩展速率模型，并假设初始裂纹形式；然后，对振动疲劳性能试验件进行断裂力学计算，得到应力强度因子Ktest等断裂力学参数；最后，对振动疲劳性能试验数据（曲线）的每一个应力水平，预设裂纹扩展速率模型参数初值以及初始裂纹长度初值，计算各应力水平的试验裂纹扩展寿命，通过参数优化的方法，获得与试验寿命结果误差最小的参数优化结果作为最终参数识别值。Specifically, first, obtain vibration fatigue performance test data such as fatigue stress-life curve or strain-life curve of materials or structural parts under vibration load, give a crack growth rate model, and assume the initial crack form; then, perform fracture mechanics calculation on the vibration fatigue performance test piece to obtain fracture mechanics parameters such as stress intensity factor Ktest; finally, for each stress level of the vibration fatigue performance test data (curve), preset the initial values of the crack growth rate model parameters and the initial crack length, calculate the test crack growth life of each stress level, and obtain the parameter optimization result with the smallest error with the test life result as the final parameter identification value through the parameter optimization method.
基于此，本申请将以单一的力学参数S（应力或应变）和寿命N表征的材料疲劳损伤模型，转换成了用初始裂纹尺寸以及断裂力学性能参数表征的材料疲劳损伤模型，并得到了裂纹扩展速率模型参数值。Based on this, this application converts the material fatigue damage model characterized by a single mechanical parameter S (stress or strain) and life N into a material fatigue damage model characterized by initial crack size and fracture mechanics performance parameters, and obtains the crack growth rate model parameter value.
S104：结合裂纹扩展速率模型对应的参数值以及预设临界裂纹长度值进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。S104: Calculating the crack growth life by combining the parameter values corresponding to the crack growth rate model and the preset critical crack length value to obtain a target crack growth life.
具体的，将时域随机应力谱和断裂力学参数代入裂纹扩展速率模型，通过指定临界裂纹长度af，以及初始裂纹长度a0，采用循环接循环的方法或者块谱平均寿命计算方法进行裂纹扩展寿命计算，得到最终裂纹扩展寿命。应理解，一组应力随机谱对应一组裂纹扩展寿命值。Specifically, the time domain random stress spectrum and fracture mechanics parameters are substituted into the crack growth rate model, and the crack growth life is calculated by specifying the critical crack length af and the initial crack length a0, using the cycle-by-cycle method or the block spectrum average life calculation method to obtain the final crack growth life. It should be understood that a set of stress random spectra corresponds to a set of crack growth life values.
与现有技术相比，本发明实施例提供的发动机结构振动疲劳裂纹扩展寿命的计算方法，在获取发动机结构的有限元模型中考核段应力响应的时域随机应力谱之后，基于时域随机应力谱，可以对发动机结构的裂纹模型进行有限元分析处理，从而确定含裂纹结构的断裂力学参数，并对按照预设裂纹扩展模式建立的裂纹扩展速率模型进行振动疲劳性能试验，利用参数识别确定裂纹扩展速率模型对应的目标参数值，最后可以结合裂纹扩展速率模型对应的参数值以及预设临界裂纹长度值进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。基于此，本发明实施例综合了结构随机振动响应计算、振动应力响应时域模拟、裂纹建模及断裂力学参数计算、裂纹扩展速率模型参数及初始裂纹长度确定以及裂纹扩展寿命计算等内容，能够获得结构随机振动稳态响应和时域应力随机谱，给出准确量化的断裂力学参数，基于疲劳性能试验数据确定裂纹扩展速率模型参数及初始裂纹长度，实现结构裂纹扩展寿命计算，克服了传统疲劳分析方法以及线弹性断裂力学的宏观裂纹分析方法用于未穿透厚度裂纹在振动环境下的寿命计算时,机理不清晰、参数获取难、模型不适用导致计算结果偏差大的缺点。Compared with the prior art, the method for calculating the vibration fatigue crack growth life of an engine structure provided in an embodiment of the present invention can, after obtaining the time-domain random stress spectrum of the stress response of the assessment section in the finite element model of the engine structure, perform finite element analysis on the crack model of the engine structure based on the time-domain random stress spectrum, thereby determining the fracture mechanics parameters of the cracked structure, and perform a vibration fatigue performance test on the crack growth rate model established according to a preset crack growth mode, and use parameter identification to determine the target parameter value corresponding to the crack growth rate model, and finally, the crack growth life can be calculated in combination with the parameter value corresponding to the crack growth rate model and the preset critical crack length value to obtain the target crack growth life. Based on this, the embodiment of the present invention integrates the calculation of structural random vibration response, time-domain simulation of vibration stress response, crack modeling and calculation of fracture mechanics parameters, determination of crack growth rate model parameters and initial crack length, and calculation of crack growth life, etc., and can obtain the steady-state response of structural random vibration and the random spectrum of time-domain stress, give accurate and quantified fracture mechanics parameters, determine the crack growth rate model parameters and the initial crack length based on fatigue performance test data, and realize the calculation of structural crack growth life, which overcomes the shortcomings of traditional fatigue analysis methods and macro crack analysis methods of linear elastic fracture mechanics when used for life calculation of non-penetrating thickness cracks in a vibration environment, such as unclear mechanism, difficult parameter acquisition, and inapplicable model, resulting in large deviations in calculation results.
由此可知，本发明实施例提供的发动机结构振动疲劳裂纹扩展寿命的计算方法能够获得可靠的断裂力学参数和裂纹扩展速率曲线，给出准确量化的裂纹扩展寿命，为重复使用发动机寿命评估提供方法指导。It can be seen from this that the calculation method for the vibration fatigue crack growth life of the engine structure provided in the embodiment of the present invention can obtain reliable fracture mechanics parameters and crack growth rate curves, give an accurately quantified crack growth life, and provide methodological guidance for the life assessment of the reused engine.
如图2所示，本发明实施例还提供另一种发动机结构振动疲劳裂纹扩展寿命的计算方法，下面将结合图2~图8，详细说明本发明实施例提供的发动机结构振动疲劳裂纹扩展寿命的计算方法的具体步骤。As shown in FIG. 2 , an embodiment of the present invention also provides another method for calculating the vibration fatigue crack growth life of an engine structure. The specific steps of the method for calculating the vibration fatigue crack growth life of an engine structure provided by an embodiment of the present invention will be described in detail below in conjunction with FIGS. 2 to 8 .
S201：建立发动机结构的有限元模型。S201: Establish a finite element model of the engine structure.
S202：对发动机结构的有限元模型施加随机振动载荷激励，确定考核段应力响应的功率谱密度。S202: Apply random vibration load excitation to the finite element model of the engine structure to determine the power spectrum density of the stress response of the assessment section.
在本申请中，采用有限元方法对结构进行动力学仿真建模，施加随机振动载荷激励得到考核部位应力响应的功率谱密度（Power Spectrum Density，PSD）和均方根值（RootMean Square，RMS），如图3所示。图3示意出了发动机结构振动应力响应严重部位也即考核段的应力功率谱密度曲线，横坐标表示频率，单位是Hz，纵坐标表示应力功率谱密度，单位是MPa2/Hz。In this application, the finite element method is used to perform dynamic simulation modeling on the structure, and random vibration load excitation is applied to obtain the power spectrum density (PSD) and root mean square (RMS) of the stress response of the test part, as shown in Figure 3. Figure 3 shows the stress power spectrum density curve of the serious part of the engine structure vibration stress response, that is, the test section, the abscissa represents the frequency in Hz, and the ordinate represents the stress power spectrum density in MPa 2 /Hz.
S203：对功率谱密度进行抽样处理，获得考核段应力响应的时域随机应力谱。S203: Perform sampling processing on the power spectrum density to obtain a time-domain random stress spectrum of the stress response of the assessment section.
具体的，对获得的振动应力响应的功率谱密度，分析给出时域应力响应的概率密度函数，然后抽样获得应力响应时域随机数，并形成时域随机应力谱。Specifically, the power spectrum density of the obtained vibration stress response is analyzed to obtain the probability density function of the time domain stress response, and then the stress response time domain random numbers are sampled to form a time domain random stress spectrum.
上述步骤S203包括以下子步骤：The above step S203 includes the following sub-steps:
子步骤A1：获取功率谱密度对应的应力幅值概率密度函数；Sub-step A1: obtaining the stress amplitude probability density function corresponding to the power spectrum density;
子步骤A2：基于应力幅值概率密度函数以及峰值概率密度函数，对时域应力响应进行抽样处理，获得应力响应样本；Sub-step A2: based on the stress amplitude probability density function and the peak probability density function, sampling the time domain stress response to obtain stress response samples;
子步骤A3：对应力响应样本进行随机化处理，确定考核段应力响应的时域随机应力谱。Sub-step A3: Randomize the stress response samples to determine the time-domain random stress spectrum of the stress response of the assessment section.
对振动应力响应的PSD谱进行分析，图4（a）为应力响应的典型窄带分布曲线；图4（b）为应力响应的典型宽带分布曲线。如图4（b）所示，若为宽带随机分布，则采用Dirlik模型获得宽带分布的应力幅值概率密度函数；如图4（a）所示，若为窄带分布，则采用Narrow-band模型获得窄带分布的应力幅值概率密度函数；同时与假设的服从高斯分布的峰值概率密度函数相结合，对时域应力响应进行抽样，获得一组足够数量的应力响应样本，最后通过随机化方法获得时域随机应力谱，如图5所示，在图5中，横坐标表示时间，单位是s，纵坐标表示应力，单位是Mpa。The PSD spectrum of the vibration stress response is analyzed. Figure 4 (a) is a typical narrowband distribution curve of the stress response; Figure 4 (b) is a typical broadband distribution curve of the stress response. As shown in Figure 4 (b), if it is a broadband random distribution, the Dirlik model is used to obtain the probability density function of the stress amplitude of the broadband distribution; as shown in Figure 4 (a), if it is a narrowband distribution, the Narrow-band model is used to obtain the probability density function of the stress amplitude of the narrowband distribution; at the same time, combined with the assumed peak probability density function that obeys the Gaussian distribution, the time domain stress response is sampled to obtain a sufficient number of stress response samples, and finally the time domain random stress spectrum is obtained by randomization method, as shown in Figure 5. In Figure 5, the horizontal axis represents time in seconds, and the vertical axis represents stress in MPa.
S204：基于时域随机应力谱，对发动机结构的裂纹模型进行有限元分析处理，确定含裂纹结构的断裂力学参数。S204: Based on the time-domain random stress spectrum, a finite element analysis is performed on the crack model of the engine structure to determine the fracture mechanics parameters of the cracked structure.
其中，断裂力学参数至少包括应力强度因子或J积分。Among them, the fracture mechanics parameters at least include stress intensity factor or J integral.
上述步骤S204包括以下子步骤：The above step S204 includes the following sub-steps:
子步骤B1：建立发动机结构的裂纹模型，如图6所示；Sub-step B1: Establishing a crack model of the engine structure, as shown in FIG6 ;
子步骤B2：基于时域随机应力谱，确定施加于裂纹模型的外载荷；Sub-step B2: determining the external load applied to the crack model based on the time-domain random stress spectrum;
子步骤B3：对施加了外载荷的裂纹模型进行弹-塑性有限元分析处理，确定各个裂纹长度对应的断裂力学参数。Sub-step B3: Perform elastic-plastic finite element analysis on the crack model with external load applied to determine the fracture mechanics parameters corresponding to each crack length.
具体试验方法为：首先，假设裂纹扩展模式，给定裂纹形式，如边缘角裂纹（EdgeCrack）、表面裂纹（Surface Crack）如图7所示。或深埋裂纹（Embedded Crack）等，设定裂纹扩展路径。然后，对发动机结构的裂纹模型进行有限元建模，结构裂纹模型主要考虑两点：一是能够包络从初始裂纹到临界裂纹长度的扩展范围；二是包含对未穿透厚度裂纹的断裂力学参数有影响的主要结构特征，如圆角、开孔及变厚度等。最后，将上述考核段应力响应的时域随机应力谱作为外载荷施加于裂纹模型进行弹-塑性有限元计算，得到各个裂纹长度ai对应的断裂力学参数Ki（应力强度因子）或Ji（J积分）。The specific test method is as follows: First, assume the crack propagation mode and give the crack form, such as edge crack (EdgeCrack), surface crack (Surface Crack) as shown in Figure 7. Or embedded crack (Embedded Crack), etc., and set the crack propagation path. Then, the crack model of the engine structure is modeled by finite element. The structural crack model mainly considers two points: one is that it can envelop the extension range from the initial crack to the critical crack length; the other is that it contains the main structural features that affect the fracture mechanics parameters of the non-penetrating thickness crack, such as fillet, opening and variable thickness. Finally, the time domain random stress spectrum of the stress response of the above-mentioned assessment section is applied as an external load to the crack model for elastic-plastic finite element calculation to obtain the fracture mechanics parameters Ki (stress intensity factor) or Ji (J integral) corresponding to each crack length ai.
基于此，本申请将实际复杂结构的三维裂纹建模简化为反映结构裂纹主要特性及应力响应特征的适当规模裂纹建模问题，同时，将结构动力学响应作为载荷输入进行断裂力学计算，将动力学问题转化为了静力问题，进而能获得弹塑性断裂力学参数解，解决了基于模态法的稳态振动响应计算无法进行弹塑性分析和非线性因素仿真模拟的问题。Based on this, the present application simplifies the three-dimensional crack modeling of actual complex structures into an appropriate scale crack modeling problem that reflects the main characteristics of structural cracks and stress response features. At the same time, the structural dynamic response is used as the load input for fracture mechanics calculations, and the dynamic problem is converted into a static problem, thereby obtaining elastic-plastic fracture mechanics parameter solutions, solving the problem that the steady-state vibration response calculation based on the modal method cannot perform elastic-plastic analysis and nonlinear factor simulation.
S205：按照预设裂纹扩展模式建立裂纹扩展速率模型。S205: Establishing a crack growth rate model according to a preset crack growth mode.
具体的，给定裂纹扩展速率模型，模型考虑应力强度因子幅值、应力强度因子最大值、应力强度因子门槛值以及裂纹闭合等因素，如采用NASGRO裂纹扩展速率公式：Specifically, given a crack growth rate model, the model considers factors such as stress intensity factor amplitude, stress intensity factor maximum value, stress intensity factor threshold value and crack closure, such as using the NASGRO crack growth rate formula:
， ,
其中，a为裂纹长度，N为循环次数，C，n，p，q为待定的模型参数值，f为裂纹张开/闭合函数，R为应力比，ΔK为应力强度因子幅值，ΔKth为裂纹扩展门槛值，Kmax为应力强度因子峰值，KC为断裂韧度。Where a is the crack length, N is the number of cycles, C, n, p, q are the values of the model parameters to be determined, f is the crack opening/closing function, R is the stress ratio, ΔK is the stress intensity factor amplitude, ΔKth is the crack extension threshold, Kmax is the stress intensity factor peak, and KC is the fracture toughness.
S206：获取发动机结构的振动疲劳应力-寿命试验曲线或振动疲劳应变-寿命试验曲线。S206: Obtain a vibration fatigue stress-life test curve or a vibration fatigue strain-life test curve of the engine structure.
S207：基于振动疲劳应力-寿命试验曲线或振动疲劳应变-寿命试验曲线，结合初始裂纹长度和裂纹扩展速率参数的初始值，确定试验裂纹扩展寿命。S207: Based on the vibration fatigue stress-life test curve or the vibration fatigue strain-life test curve, combined with the initial values of the initial crack length and the crack growth rate parameter, determine the test crack growth life.
S208：利用参数优化的方法，对裂纹扩展速率参数的初始值进行优化，确定误差最小的参数值为裂纹扩展速率模型对应的参数值。S208: Optimizing the initial value of the crack growth rate parameter using a parameter optimization method, and determining the parameter value with the smallest error as the parameter value corresponding to the crack growth rate model.
在本申请中，获取材料或结构件的振动疲劳应力-寿命或应变-寿命试验数据（曲线），对试验的每一个应力/应变水平，假设初始裂纹长度a0和裂纹扩展速率参数的初值（a0ini，Cini，nini，pini，qini），并计算试验裂纹扩展寿命，通过参数优化的方法，获得与试验寿命结果误差最小的参数优化结果作为最终的目标参数值，如图8所示。In this application, the vibration fatigue stress-life or strain-life test data (curve) of the material or structural component is obtained, and for each stress/strain level of the test, the initial crack length a0 and the initial values of the crack growth rate parameters (a0 ini , C ini , n ini , pini , qini ) are assumed, and the test crack growth life is calculated. Through the parameter optimization method, the parameter optimization result with the smallest error with the test life result is obtained as the final target parameter value, as shown in Figure 8.
基于此，本申请将以单一的力学参数S（应力或应变）和寿命N表征的材料疲劳损伤模型，转换成了用裂纹尺寸及其断裂力学性能参数表征的材料疲劳损伤模型，并得到了裂纹扩展速率模型参数值。Based on this, this application converts the material fatigue damage model characterized by a single mechanical parameter S (stress or strain) and life N into a material fatigue damage model characterized by crack size and its fracture mechanics performance parameters, and obtains the crack growth rate model parameter value.
S209：结合裂纹扩展速率模型对应的参数值以及预设临界裂纹长度值进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。S209: Calculating the crack growth life by combining the parameter values corresponding to the crack growth rate model and the preset critical crack length value to obtain a target crack growth life.
在本申请中，结合时域随机应力谱、断裂力学参数、裂纹扩展速率模型对应的目标参数值以及预设临界裂纹长度值，利用循环接循环的方法或块谱平均寿命计算法进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。In this application, the crack growth life is calculated by combining the time-domain random stress spectrum, fracture mechanics parameters, target parameter values corresponding to the crack growth rate model and the preset critical crack length value, and the target crack growth life is obtained by using the cycle-by-cycle method or the block spectrum average life calculation method.
应理解，一组应力随机谱对应一组裂纹扩展寿命值。It should be understood that a set of stress random spectra corresponds to a set of crack growth life values.
本发明实施例的有益效果是：The beneficial effects of the embodiments of the present invention are:
（1）通过稳态振动响应计算和应力响应时域模拟，既考虑了结构应力响应的频域特征，也考虑了应力响应的时域统计特征，振动载荷下的应力特征得到完整保留，使寿命计算更加充分和精细；(1) Through steady-state vibration response calculation and stress response time domain simulation, both the frequency domain characteristics of the structural stress response and the time domain statistical characteristics of the stress response are taken into account. The stress characteristics under vibration load are fully preserved, making the life calculation more comprehensive and precise.
（2）将时域应力响应作为外载荷进行裂纹建模，一方面为结构整体裂纹建模转化为局部结构裂纹建模提供了载荷基础，降低了模型规模，大幅提高了计算效率。另一方面将动力学计算转化成了静力计算问题，能够获得更加真实的弹塑性和非线性解，断裂力学参数准确性得到显著改善；(2) Using the time-domain stress response as an external load for crack modeling provides a load basis for converting the overall structural crack modeling into the local structural crack modeling, reduces the model size, and greatly improves the calculation efficiency. On the other hand, the dynamic calculation is converted into a static calculation problem, which can obtain more realistic elastic-plastic and nonlinear solutions, and the accuracy of fracture mechanics parameters is significantly improved;
（3）充分利用疲劳性能试验数据识别裂纹扩展速率模型参数和初始裂纹长度分布，确保了裂纹扩展寿命计算关键性能参数的来源可靠，模型化机理更加清晰，避免了传统通过宏观长裂纹模型外插方法的不确定性，保证了计算模型和计算结果合理、可靠。(3) The fatigue performance test data is fully utilized to identify the crack growth rate model parameters and the initial crack length distribution, ensuring that the source of the key performance parameters for crack growth life calculation is reliable, the modeling mechanism is clearer, and the uncertainty of the traditional method of extrapolating the macroscopic long crack model is avoided, ensuring that the calculation model and calculation results are reasonable and reliable.
如图9所示，本发明实施例还提供一种发动机结构振动疲劳裂纹扩展寿命的计算装置300，用于实现上述实施例中发动机结构振动疲劳裂纹扩展寿命的计算方法，计算装置包括：As shown in FIG9 , an embodiment of the present invention further provides a device 300 for calculating the vibration fatigue crack growth life of an engine structure, which is used to implement the method for calculating the vibration fatigue crack growth life of an engine structure in the above embodiment. The device comprises:
获取模块301，用于获取发动机结构的有限元模型中考核段应力响应的时域随机应力谱；An acquisition module 301 is used to acquire a time-domain random stress spectrum of a stress response of an assessment section in a finite element model of an engine structure;
第一确定模块302，用于基于时域随机应力谱，对发动机结构的裂纹模型进行有限元分析处理，确定含裂纹结构的断裂力学参数；A first determination module 302 is used to perform finite element analysis on the crack model of the engine structure based on the time domain random stress spectrum to determine the fracture mechanics parameters of the cracked structure;
第二确定模块303，用于对按照预设裂纹扩展模式建立的裂纹扩展速率模型进行振动疲劳性能试验，利用参数识别确定裂纹扩展速率模型对应的目标参数值；The second determination module 303 is used to perform a vibration fatigue performance test on the crack growth rate model established according to the preset crack growth mode, and determine the target parameter value corresponding to the crack growth rate model by using parameter identification;
获得模块304，用于结合裂纹扩展速率模型对应的参数值以及预设临界裂纹长度值进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。The obtaining module 304 is used to calculate the crack growth life by combining the parameter values corresponding to the crack growth rate model and the preset critical crack length value to obtain the target crack growth life.
可选的，获取模块301包括：Optionally, the acquisition module 301 includes:
第一建立单元，用于建立发动机结构的有限元模型；A first building unit is used to build a finite element model of the engine structure;
第一确定单元，用于对发动机结构的有限元模型施加随机振动载荷激励，确定考核段应力响应的功率谱密度；The first determination unit is used to apply random vibration load excitation to the finite element model of the engine structure to determine the power spectrum density of the stress response of the assessment section;
第一获得单元，用于对功率谱密度进行抽样处理，获得考核段应力响应的时域随机应力谱。The first obtaining unit is used to perform sampling processing on the power spectrum density to obtain the time domain random stress spectrum of the stress response of the assessment section.
可选的，第一获得单元包括：Optionally, the first obtaining unit includes:
获取子单元，用于获取功率谱密度对应的应力幅值概率密度函数；An acquisition subunit is used to obtain a stress amplitude probability density function corresponding to a power spectrum density;
获得子单元，用于基于应力幅值概率密度函数以及峰值概率密度函数，对时域应力响应进行抽样处理，获得应力响应样本；An acquisition subunit is used to perform sampling processing on the time domain stress response based on the stress amplitude probability density function and the peak value probability density function to obtain a stress response sample;
确定子单元，用于对应力响应样本进行随机化处理，确定考核段应力响应的时域随机应力谱。A subunit is determined to perform random processing on the stress response samples and determine the time-domain random stress spectrum of the stress response of the assessment section.
可选的，第一确定模块302包括：Optionally, the first determining module 302 includes:
第二建立单元，用于建立发动机结构的裂纹模型；A second establishing unit is used to establish a crack model of the engine structure;
第二确定单元，用于基于时域随机应力谱，确定施加于裂纹模型的外载荷；a second determination unit, for determining an external load applied to the crack model based on the time-domain random stress spectrum;
第三确定单元，用于对施加了外载荷的裂纹模型进行弹-塑性有限元分析处理，确定各个裂纹长度对应的断裂力学参数。The third determination unit is used to perform elastic-plastic finite element analysis on the crack model to which the external load is applied, and determine the fracture mechanics parameters corresponding to each crack length.
可选的，断裂力学参数至少包括应力强度因子或J积分。Optionally, the fracture mechanics parameters include at least a stress intensity factor or a J-integral.
可选的，第二确定模块303包括：Optionally, the second determining module 303 includes:
第三建立单元，用于按照预设裂纹扩展模式建立裂纹扩展速率模型；A third establishing unit is used to establish a crack growth rate model according to a preset crack growth mode;
获取单元，用于获取发动机结构的振动疲劳应力-寿命试验曲线或振动疲劳应变-寿命试验曲线；An acquisition unit, used for acquiring a vibration fatigue stress-life test curve or a vibration fatigue strain-life test curve of an engine structure;
第四确定单元，用于基于振动疲劳应力-寿命试验曲线或振动疲劳应变-寿命试验曲线，结合初始裂纹长度和裂纹扩展速率参数的初始值，确定试验裂纹扩展寿命；A fourth determination unit is used to determine the test crack growth life based on the vibration fatigue stress-life test curve or the vibration fatigue strain-life test curve in combination with the initial crack length and the initial value of the crack growth rate parameter;
第五确定单元，用于利用参数优化的方法，对裂纹扩展速率参数的初始值进行优化，确定误差最小的参数值为裂纹扩展速率模型对应的参数值。The fifth determining unit is used to optimize the initial value of the crack growth rate parameter by using a parameter optimization method, and determine the parameter value with the smallest error as the parameter value corresponding to the crack growth rate model.
可选的，裂纹扩展速率模型，包括：Optional, crack growth rate models, including:
， ,
其中，其中，a为裂纹长度，N为循环次数，C，n，p，q为待定的模型参数值，f为裂纹张开/闭合函数，R为应力比，ΔK为应力强度因子幅值，ΔKth为裂纹扩展门槛值，Kmax为应力强度因子峰值，KC为断裂韧度。Among them, a is the crack length, N is the number of cycles, C, n, p, q are the values of the model parameters to be determined, f is the crack opening/closing function, R is the stress ratio, ΔK is the stress intensity factor amplitude, ΔKth is the crack extension threshold, Kmax is the stress intensity factor peak, and KC is the fracture toughness.
可选的，获得模块304包括：Optionally, the obtaining module 304 includes:
第二获得单元，用于结合时域随机应力谱、断裂力学参数、裂纹扩展速率模型对应的目标参数值以及预设临界裂纹长度值，利用循环接循环的方法或块谱平均寿命计算法进行裂纹扩展寿命计算，获得目标裂纹扩展寿命。The second acquisition unit is used to combine the time domain random stress spectrum, fracture mechanics parameters, target parameter values corresponding to the crack growth rate model and the preset critical crack length value, and calculate the crack growth life using the cycle-by-cycle method or the block spectrum average life calculation method to obtain the target crack growth life.
本发明实施例提供的发动机结构振动疲劳裂纹扩展寿命的计算装置的有益效果与上述实施例中描述的发动机结构振动疲劳裂纹扩展寿命的计算方法的有益效果相同，此处不做赘述。The beneficial effects of the device for calculating the vibration fatigue crack growth life of an engine structure provided in an embodiment of the present invention are the same as the beneficial effects of the method for calculating the vibration fatigue crack growth life of an engine structure described in the above embodiment, and are not described in detail here.
尽管在此结合各实施例对本发明进行了描述，然而，在实施所要求保护的本发明过程中，本领域技术人员通过查看附图、公开内容、以及所附权利要求书，可理解并实现公开实施例的其他变化。在权利要求中，“包括”（comprising）一词不排除其他组成部分或步骤，“一”或“一个”不排除多个的情况。单个处理器或其他单元可以实现权利要求中列举的若干项功能。相互不同的从属权利要求中记载了某些措施，但这并不表示这些措施不能组合起来产生良好的效果。Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in a claim. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.
尽管结合具体特征及其实施例对本发明进行了描述，显而易见的，在不脱离本发明的精神和范围的情况下，可对其进行各种修改和组合。相应地，本说明书和附图仅仅是所附权利要求所界定的本发明的示例性说明，且视为已覆盖本发明范围内的任意和所有修改、变化、组合或等同物。显然，本领域的技术人员可以对本发明进行各种改动和变型而不脱离本发明的精神和范围。这样，倘若本发明的这些修改和变型属于本发明权利要求及其等同技术的范围之内，则本发明也意图包括这些改动和变型在内。Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the claims of the present invention and their equivalents.
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