共查询到16条相似文献,搜索用时 62 毫秒
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基于断裂力学的疲劳裂纹扩展寿命问题的研究常常将裂纹尖端应力展开项的高次项忽略,引起了裂纹扩展模拟的误差,本文考虑高次项T-stress对裂纹扩展角的影响,对裂纹扩展过程做了数值模拟,结果显示相同裂纹扩展长度下,考虑T-stress会延长裂纹扩展寿命。文章首先采用修正的Paris-Erdogan 公式计算了两端承受均布拉伸载荷的边缘斜裂纹板的疲劳裂纹扩展寿命,裂纹扩展方向采用两参数修正的最大拉应力准则。由于结构尺寸,材料特性和载荷等因素具有不确定性,导致疲劳裂纹扩展过程带有一定的随机性,本文以材料属性和载荷为随机变量,在随机有限元法的基础上,结合计算可靠度的四阶矩法,Edgeworth级数展开方法,提出随机参数服从任意分布时的结构疲劳裂纹扩展寿命可靠度的计算方法。分析了参数为非正态分布时的平板裂纹扩展寿命可靠度随裂纹扩展的变化过程。本文方法可预测工程中板裂纹的扩展行为,以及预测裂纹板的可靠度。 相似文献
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本文提供了自增强厚壁圆筒疲劳裂纹扩展寿命的可靠性分析的方法和公式,自增强残余应力用符合厚壁筒用钢具有强化和包辛格效应实际性能推得的公式进行计算,残余应力对应的应力强度因子的计算采用了有限元法,得到了工作内压与自增强残余应力共同作用下的厚壁筒应力强度因子公式,通过实验测定了厚壁筒用钢的断裂韧度和疲劳裂纹扩展速率等性能。 相似文献
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疲劳安全与寿命可靠性评估二次三阶矩方法 总被引:4,自引:0,他引:4
提出了疲劳安全与寿命可靠性评估的二次三阶矩方法,并且给出了常用随机变量的三阶矩计算方法,由于采用三参数威尔布分布拟合,可以较好地描述各种分布形态的随机变量,与传统的一次二阶矩方法比较,该文提出的方法计算精度高,适应性强。 相似文献
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疲劳裂纹扩展门槛值试验的可靠性分析 总被引:2,自引:0,他引:2
本文用30块30CrMnSiA合金铜的CCT试件所测得的ΔK_(th)试验数据检验了随机变量ΔK_(th)的分布特性,确认材料与厚度相同的试件在相同应力比下所测得的ΔK_(th)值基本遵循正态分布。在此基础上对ΔK_(th)试验进行了如下可靠性分析:具有指定可靠度与置信度的ΔK_(th)值,不同材料ΔK_(th)的统计对比,最少试件数。 相似文献
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焊接接头低周疲劳裂纹扩展的统计分析与可靠性最弱环模型 总被引:4,自引:0,他引:4
在相同的试验条件下,对16MnR压力容器用钢焊接接头焊缝区、热影响区和母材区,分别做了15 根试样的低周疲劳试验,获得了三个区的低周疲劳寿命分布与裂纹扩展规律。试验表明,Paris公式中的两个参数m 和c 分别服从正态分布和对数正态分布,m 和log c 呈现统计线性关系。根据文中的统计结果,采用蒙特卡洛法对给定的两个裂纹长度间的扩展寿命进行了预测,预测结果与试验结果符合良好。文中还对焊接接头三个区的低周疲劳寿命进行了统计分析,获得了相应的概率密度函数,初步提出了整个焊接接头的可靠性最弱环模型。 相似文献
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IntroductionWhenacomponentforinstancethetransmissionshaftandthevibrationcomponent,etc.endureratherlowstresslevelandlongstresscycles,itssafetyiscontrolledbyfatiguestressanditcanbedesignedaccordingtotheinfinitelifedesignmethodofhighcyclefatigue .Whenacom… 相似文献
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Experimental analysis of propagation of fatigue crack on gears 总被引:1,自引:0,他引:1
Gears of different sizes and with different systems of loading are indispensable components of machines and devices. When optimizing such gear assemblies, on of the most important parameters is their required service life. To calculate the service life as precisely and reliably as possible, researchers need to use the required mathematical models for describing loading, the geometry, properties of materials and fracture mechanics parameters. The accuracy and reliability of the gear model assemblies can be compared only with appropriate experimental results. To this end, the authors have used and developed a series of methods and test pieces. A comparison of results has shown that the models and approaches are adequate. 相似文献
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提出了一个利用结构有限元方法中间隙元的原理来计算和分析疲劳寿命的新的累积损伤模型和方法。该方法利用间隙来模拟裂纹的形成和扩展 ,并提出新的累积损伤理论。不仅可以得到构件的疲劳总寿命 ,而且还可以用于计算裂纹的生成寿命、扩展寿命。同时又描述了裂纹的开裂过程 ,即裂纹的开裂尺寸和开裂方向。这为进行各种疲劳强度设计提供了一个新的思路和方法 相似文献
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An investigation is presented on the suitability and accuracy of a thermoelastic technique for the analysis of fatigue cracks.
The stress intensity factor ranges ΔK
I and ΔK
II are determined from thermoelastic data recorded from around the tip of a sharp slot in a steel specimen under biaxial load,
in order to assess the accuracy of the technique. ΔK
I and ΔK
II are determined to within 4% and 9% of a theoretical prediction, respectively. The results from a similar test on a fatigue
crack under biaxial load are also presented. These show that thermoelastic stress analysis is a rapid and accurate way of
analyzing mixed-mode fatigue cracks. A discussion is given on the potential of thermoelastic stress analysis of propagating
cracks. 相似文献
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E. Giner N. Sukumar F.D. Denia F.J. Fuenmayor 《International Journal of Solids and Structures》2008,45(22-23):5675-5687
In this paper, the extended finite element method (X-FEM) is considered for the analysis of fretting fatigue problems. A two-dimensional implementation of the X-FEM is carried out within the finite element software ABAQUS? by means of user subroutines, and crack propagation in fretting fatigue problems is investigated. On utilizing the non-linear contact capabilities of this code, the numerical technique is applied to a specimen-indenter model. The use of the X-FEM facilitates very accurate stress intensity factor computations on relatively coarse meshes, and furthermore, no remeshing is required for crack growth simulations. The implementation is applied to complete and incomplete contact fretting problems. A study of crack growth is conducted for several bulk loads applied to the specimen, and the influence of the initial crack angle is ascertained. The numerical simulations reveal the merits of applying the X-FEM to fretting fatigue problems. 相似文献