多轴低周疲劳寿命预测软件

通过Visual Basic6.0各种控件和算法的运用，编制的“多轴低周疲劳寿命预测软件（MLCFP1.0）”，涉及多种疲劳寿命预测方法，特别适用于结构中出现非比较、多轴应力状态的情况，为多轴疲劳下的寿命预测提供了解决的有力工具。本软件还留有新模型的嵌入接口，数据处理过程实现多文件操作。后处理绘图软件LCF FIGURE1.0，能给出标准的疲劳寿命预测图形，其保存文件形式多样。     

45钢非线性多轴疲劳累积损伤律研究

对45号中碳钢薄壁圆管试件进行了拉-扭复合双轴加载的多种比例及非比例路径下的常幅疲劳寿命试验以及多种组合两级变路径的多轴累积疲劳试验。应用所得试验数据对现有的常用疲劳损伤累积模型进行验证,基于Manson损伤曲线累积模型添加载荷路径变换因子,提出了一个适用于多轴非比例加载的非线性疲劳损伤累积模型,并对模型进行了验证,数据点基本控制在2倍误差带之内,得到令人满意的预测结果。     

Evaluation method of multiaxial low cycle fatigue life for cubic single crystal material

The coupling effect of normal stress and shear stress on orthotropic materials happens when applied loading deflects from the directions of the principal axes of the material coordinate system. By taking account of the coupling effects, formulas of equivalent stress and strain for cubic single crystal materials are cited. Using the equivalent strain and equivalent stress for such material and a variable k, which is introduced to express the effect of asymmetrical cyclic loading on fatigue life, a low cycle fatigue (LCF) life prediction model for such material in multiaxial stress starts is proposed. On the basis of the yield criterion and constitutive model of cubic single crystal materials, a subroutine to calculate the thermo elastic-plastic stress-strain of the material on an ANSYS platform was developed. The cyclic stress-strain of DD3 notched specimens under asymmetrical loading at 680°C was analyzed. Low cycle fatigue test data of the single crystal nickel-based superalloy are used to fit the different parameters of the power law with multiple linear regression analysis. The equivalent stress and strain for a cubic single crystal material as failure parameters have the largest correlation coefficient. A power law exists between k and the failure cycle. The model was validated with LCF test data of CMSX-2 and DD3 single crystal nickel-based superalloys. All the test data fall into the factor of 2.5 for CMSX-2 hollow cylinder specimens and 2.0 scatter band for DD3 notched specimens, respectively.     

Reliability design of preventive maintenance scheduling for cumulative fatigue damage

As the cumulative running times of a locomotive truck increases, degradation such as fatigue, wear, and deterioration occur. Particularly the container train and uncovered freight train, their maintenance cost during their lifetime is three times more than the manufacturing cost. Generally, for the freight train, corrective maintenance to repair a bad part after a breakdown is not adapted; however, preventive maintenance that fixes a bad part before a breakdown is. Therefore, it is important and necessary to establish a system of optimal preventive maintenance and exact maintenance period. This study attempts to propose a preventive maintenance procedure that predicts a repair period using reliability function and instantaneous failure rate based on fatigue test and load history data. Additionally, this method is applied to the end beam of an uncovered freight train, which is the brake part, and its usefulness is examined and analyzed. This paper was recommended for publication in revised form by Associate Editor Chongdu Cho Seok-Heum Baek received a B.S. and M.S. degree in Mechanical Engineering from the Dong-A University in 2001 and 2003, respectively. He is currently a Ph.D. student at the School of Mechanical Engineering at Dong-A University in Busan, Korea. Student Baek works on ceramic composite design and robust and reliability-based design, and his research interests are in the areas of trade-off analysis in multicriteria optimization, design under uncertainty with incomplete information, and probabilistic design optimization. Seok-Swoo Cho received a B.S. degree in Mechanical Engineering from Dong-A University in 1991. He then went on to receive his M.S. from Dong-A University in 1993 and Ph.D. degree from Dong-A University in 1997. Dr. Cho is currently a Professor at the Vehicle Engineering at Kangwon National University in Kangwon-do, Korea. Dr. Cho works on crack growth modeling and composite design and optimization, and his research interests are in the areas of structural optimization and inverse and identification problems, and X-ray diffraction, brittle collapse and crack propagation, fatigue fracture phenomena. Hyun-Su Kim received a B.S. degree in Mechanical Engineering from Seoul National University in 1978. He then went on to receive his M.S. from KAIST in 1980 and Ph.D. degree from University of Iowa in 1989. Dr. Kim is currently a Professor at the Mechanical Engineering at Dong-A University in Busan, Korea. His research interests are in the area of high temperature creep fatigue, bio-engineering, design using the finite element method, optimization, and MEMS. Won-Sik Joo received a B.S. degree in Mechanical Engineering from Dong-A University in 1968. He then went on to receive his M.S. from Dong-A University in 1978 and Ph.D. degree from Kookmin University in 1988. Dr. Joo is currently a Professor at the Mechanical Engineering at Dong-A University in Busan, Korea. His research interests are in the area of creep and fatigue in high temperature alloy, fatigue design, and strength evaluation.     

基于线性疲劳累积损伤理论的直齿圆锥齿轮传动可靠度计算

线性疲劳累积损伤可靠性理论认为零部件的可靠度取决于抗疲劳损伤强度大于疲劳损伤量的概率,本文将此理论应用于直齿圆锥齿轮传动的可靠性设计,建立单级载荷谱工况下可靠度计算模型,通过分析和计算直齿圆锥齿轮设计算例,结果验证了基于线性疲劳累积损伤理论的可靠度计算模型在直齿圆锥齿轮传动可靠度计算中的可行性与合理性,为机械零部件的可靠性设计提供了理论依据。     

一种可用于复合材料寿命预测的非线性疲劳损伤累积模型

结合试验数据,提出了一种含有3个待定参数的非线性疲劳损伤累积模型,该模型能够描述复合材料结构疲劳损伤扩展3个阶段,即可以模拟初始循环载荷的损伤快速增长阶段、达到特征损伤状态时的缓慢增长阶段及断裂前损伤快速扩展的阶段。通过算例验证:本文模型与试验数据吻合性较好,可用于对复合材料结构疲劳寿命进行预测及损伤评估。     

基于损伤容限设计的疲劳裂纹扩展寿命估算

从损伤容限设计概念出发,以断裂力学理论为基础,在承认零构件内具有初始缺陷的基础上,应用著名的Par-is裂纹扩展速率公式,以对1020冷轧薄钢板在承受单轴恒幅循环载荷下的寿命次数的估算为例,介绍了一种简单实用的疲劳寿命估算方法,从而为技术人员在进行含裂纹件的疲劳裂纹扩展寿命计算中提供一定的理论依据。     

基于损伤力学-临界面法预估多轴疲劳寿命

基于损伤力学理论建立的非线性疲劳寿命预估模型在多轴疲劳寿命预估中获得了广泛的应用,但该模型并未考虑损伤面发生的位置及其物理意义,将其与临界面法相结合提出一种新的多轴非线性疲劳寿命预估模型,新模型能够弥补现有的非线性疲劳寿命预估模型未考虑临界面物理意义的不足。新模型从损伤的角度来预估多轴疲劳寿命,不仅考虑了临界面上裂纹形成及扩展的物理意义、相位差对附加强化现象的影响,而且对非对称加载下的平均应变进行修正。新模型仅仅利用单轴疲劳试验数据以及单轴疲劳材料常数就可以预估出试样的多轴疲劳寿命,从而避免了代价高昂的多轴疲劳试验。采用45钢、316不锈钢、钛合金TC4三种材料的多轴疲劳试验数据对提出的模型进行评估和验证,对几种材料比例/非比例以及对称/非对称加载下的多轴疲劳寿命进行预估,预估结果与试验结果的误差都在5%以内,结果表明提出的多轴非线性疲劳寿命预估模型具有较高的预估精度。     

Aero-engine blade fatigue analysis based on nonlinear continuum damage model using neural networks

Fatigue life and reliability of aero-engine blade are always of important significance to flight safety.The establishment of damage model is one of the key factors in blade fatigue research.Conventiona...     

Determination of fragments of multiaxial service loading strongly influencing the fatigue of machine components

The paper presents a method for determination of multiaxial load segments from original service histories, where the loaded machine part is meaningfully subjected to fatigue damage. These load segments are directly separated from a service-loading history, which can be of a random character. Typical procedures used for fatigue life assessment under multiaxial random loading are implemented to perform this task. While reduction from the multiaxial stress state to the equivalent uniaxial one, application of the linear multiaxial fatigue failure criteria was proposed. The equivalent stress history is subjected to the rainflow cycle-counting method, which allows to determine the amplitudes and mean values of counted cycles, their occurrence moment and time of duration. Influence of the stress mean value was taken into consideration with the Morrow's model. On the assumption of the linear Palmgren–Miner hypothesis of damage accumulation and the stress–life fatigue characteristics of the material, the damage-time function was determined. The load segments, where the influence on the material fatigue was significant, were determined on the basis of the fixed damage-intensity level and the proposed damage-intensity function. The presented method was studied on a hook loaded with two independent forces. FEM program which has the possibility to perform fatigue analysis was used during the computation for determining the expected place of crack initiation. The service-loading course was compressed to shorter one, so that only a small decrease of the fatigue damage in comparison with full length of the original service loading was observed. The proposed method seems to be right for preparing multiaxial loading histories in order to cut down the fatigue tests, especially in the case when the correlation between particular loading channels is very important.     

多轴变幅载荷下基于载荷支配模式的缺口件疲劳寿命预测方法

提出一种多轴变幅载荷下基于载荷支配模式的缺口件疲劳寿命预测方法。首先,通过循环计数方法确定多轴变幅载荷历程的计数循环(反复);其次,通过材料的循环应力应变关系和Neuber法推导出虚拟等效应变与真实等效应力之间的关系,并且分别将拉伸型和剪切型Shang-Wang多轴疲劳损伤参数替换虚拟等效应变幅来求解临界面上的真实等效应力幅;然后,通过真实等效应力幅和Neuber法则计算临界面上真实的拉压和剪切等效应变幅,并运用Manson-Coffin方程分别计算缺口部件的拉压和剪切疲劳寿命;最后,选择拉压和剪切疲劳损伤值中的较大值作为每个计数反复的疲劳损伤,并采用Miner法则进行疲劳损伤累积。缺口件多轴疲劳试验结果表明,采用基于载荷支配模式的缺口件疲劳寿命预测方法具有较高的预测准确度。     

中碳钢多轴循环特性的试验研究

针对拉扭薄壁疲劳试样,在控制总应用拉扭循环加载下对中碳钢进行了试验研究。分别测试对称与存在平均拉扭应变情况下,比例加载与非比例加载时,拉与扭的应力响应值随循环数的变化情况。     

A finite element model for rolling contact fatigue of refurbished bearings

Bearing refurbishing has become a popular method of extending the life of rolling element bearings. In the refurbishing process the raceways of the bearing may be ground to remove any surface damage prior to repolishing and reassembly with larger sized rolling elements. In the current study a continuum damage mechanics finite element model was developed to quantify the damage in original and refurbished bearings. After calculating the damage accumulation for a set number of contact cycles with the original bearing geometry, refurbishing is simulated by removing a layer of the original surface. The refurbished microstructural model is then subjected to additional computational contact cycles until a fatigue crack reaches the surface, signifying failure. This model preserves the fatigue damage accumulated prior to refurbishing and evaluates its influence on the refurbished bearing fatigue life. All refurbished bearing surfaces showed a significant amount of life after refurbishing with L₁₀ lives from the point of refurbishment, varying from 20% to 94% of the original L₁₀ life. The results indicate that the remaining life of the refurbished bearing population is inversely related to the time before refurbishing and is proportional to the depth of the regrinding. Results obtained from this investigation are in good agreement when compared to the Lundberg-Palmgren bearing life equation modified for analyzing the life of a refurbished bearing.     

基于累积损伤的渗碳齿轮钢疲劳寿命预测模型构建

采用轴向高频疲劳试验机进行超高周疲劳实验,研究了不同应力比(R=0和R=0.3)下渗碳齿轮钢疲劳特性。结果表明：在应力比为0和0.3时,渗碳齿轮钢的失效形式分为表面失效和内部失效。内部失效过程分为疲劳裂纹萌生阶段(夹杂-细颗粒区(fine granular area, FGA))、稳定扩展阶段(FGA-鱼眼)和瞬间断裂(鱼眼之外)。基于累积损伤法,建立了内部裂纹萌生和扩展阶段的疲劳寿命预测模型;最终建立了渗碳齿轮钢多应力比下的全寿命预测模型,预测精度较高。     

一种多轴载荷下的疲劳寿命预测模型

提出了一种多轴疲劳载荷下的疲劳寿命预测模型,该模型运用Von mises等效应力应变之间的关系,将单轴Manson~Coffin方程的寿命预测模型转化为多轴疲劳应力~寿命预测模型。以2A12铝合金为分析研究对象,依据相关的经验公式以及运用有限元仿真方法得出寿命预测模型的相关常数,从而获得寿命预测曲线。通过和实验结果比较可知,所提出的多轴寿命预测模型具有较好的预测精度,能有效的预测多轴载荷下的疲劳寿命。     

汽车变速器疲劳寿命的研究与发展综述

为了进一步推进汽车变速器疲劳寿命研究的发展,根据汽车变速器疲劳寿命研究方法的特点和应用状况,分别从变速器的载荷、变速器的疲劳试验和变速器的寿命预测3个方面对变速器寿命的研究进行了综述,为以后的研究提供参考。针对变速器载荷谱的编制,分析总结了现有的变速器载荷谱编制方法,其结果表明:程序载荷谱的编制是变速器载荷谱编制最准确有效的方法,但是现有的程序载荷谱并不能满足所有变速器寿命预测的要求;对于不同载荷谱作用下的疲劳试验,分析了每种试验的加载和试验结果,其结果表明:基于程序谱加载的疲劳试验能很好地模拟变速器的实际工作过程,试验结果最为准确;通过分析对比变速器寿命预测的几种常用的方法,其结果表明:概率疲劳寿命预测可以为变速器的研发和维修提供更全面的数据,是未来研究的重点。最后针对变速器载荷谱编制、虚拟试验和变速器疲劳数值仿真等,提出了其可能的研究热点和方向。     

起重机门架结构的疲劳寿命分析

重点介绍利用断裂力学理论进行门式起重机结构的疲劳寿命分析的方法,通过运用损伤容限设计方法对门架结构进行的疲劳寿命计算,得出了门机主梁与悬臂梁联结部位初始裂纹为0.5mm时门架结构的设计寿命,并分析了模型中参数变化对门架结构寿命的影响,说明利用该方法估算门架结构的寿命具有可行性,对实际工程具有参考价值。     

多轴疲劳寿命工程预测方法

介绍了一种预测受多轴交变载荷工程构件的低周疲劳寿命的方法。该方法以实例的应变计响应作为输入,通过一个循环塑性模型计算测量点的弹塑性应力应变分量,然后用多种多轴临界面疲劳损伤模型计算寿命。所发展的程序可处理一般的自由表面疲劳问题,它的应用通过分析一个典型的汽车零部件得到说明。     

高温比例与非比例加载下多轴疲劳寿命预测

针对拉扭多轴疲劳加载情况,分析最大剪切平面上的应变特性。利用临界损伤平面原理确定不同加载参数下的临界损伤平面,在此基础上提出一种基于单轴疲劳材料常数和高温蠕变特性的高温多轴疲劳寿命预测模型。利用高温合金材料GH4169薄壁管疲劳试样在控制应变拉扭循环加载下的试验数据,对所提出的寿命模型进行验证。结果表明,在高温低周拉扭循环加载下,所提出的高温疲劳寿命预测模型可以较好地预测高温疲劳寿命。     

Contact fatigue life prediction of a bevel gear under spectrum loading

Rolling contact fatigue (RCF) issues, such as pitting, might occur on bevel gears because load fluctuation induces considerable subsurface stress amplitudes. Such issues can dramatically affect the service life of associated machines. An accurate geometry model of a hypoid gear utilized in the main reducer of a heavy-duty vehicle is developed in this study with the commercial gear design software MASTA. Multiaxial stress–strain states are simulated with the finite element method, and the RCF life is predicted using the Brown–Miller–Morrow fatigue criterion. The patterns of fatigue life on the tooth surface are simulated under various loading levels, and the RCF S–N curve is numerically generated. Moreover, a typical torque–time history on the driven axle is described, followed by the construction of program load spectrum with the rain flow method and the Goodman mean stress equation. The effects of various fatigue damage accumulation rules on fatigue life are compared and discussed in detail. Predicted results reveal that the Miner linear rule provides the most optimistic result among the three selected rules, and the Manson bilinear rule produces the most conservative result.