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1.
自紧炮管的疲劳寿命分析   总被引:1,自引:1,他引:0  
本文用有限单元法计算了自紧残余应力对应的炮管的应力强度因子.自紧残余应力采用了符合炮管材料具有强化和包辛格效应性能推导的公式计算,根据工作内压和残余应力共同作用下炮管的总应力强度因子和测定的炮钢断裂韧度及疲劳裂纹扩展性能,分析了自紧炮管的疲劳寿命及自紧度和裂纹构形对疲劳寿命的影响.  相似文献   

2.
本文研究了在自增强残余应力下,具有对称轴向双裂纹的厚壁简的应力强度因子的计算方法。文中采用了符合厚壁筒材料具有强化和包辛格效应实际性能的厚壁简自增强残余应力计算公式,通过叠加和等效载荷处理用有限单元法计算了残余应力对应的强度因子。本文的方法对具有自相平衡的残余应力结构的K1计算都有参考价值。  相似文献   

3.
残余应力下厚壁筒表面裂纹的应力强度因子计算   总被引:1,自引:0,他引:1  
本文首先介绍了边界元法计算裂纹尖端应力强度因子的基本理论,接着利用边界元法计算了在残余应力下不同厚壁筒内表面椭圆裂纹的应力强度因子,研究了其大不随椭圆裂纹不同而变化的规律,为厚壁筒结构的设计,制造以及疲劳寿命分析提供了许多有价值的参考资料。  相似文献   

4.
采用四步法计算了考虑循环载荷中压应力影响的正交异性钢桥面板的肋-面板焊缝表面裂纹扩展。第一步是基于正交异性钢桥面板的疲劳分析模型,计算肋-面板焊缝处的应力,第二步是通过肋-面板焊缝的三维局部模型,用Schwartz-Neumann交替法计算焊缝表面裂纹的应力强度因子分布,第三步是用二维断裂力学模型和增量塑性损伤模型,计算循环载荷中的压应力对裂纹扩展的影响,第四步是用第二步中的三维裂纹分析结果和第三步中的二维断裂力学模型得到的裂纹扩展公式,计算钢桥面板的肋-面板焊缝表面裂纹扩展。计算结果表明,对应于正交异性钢桥面板肋-面板焊缝处的循环应力,本文所用模型的裂纹尖端反向塑性区导致裂纹扩展率增加50%以上。研究结果为正交异性钢桥面板肋-面板焊缝裂纹的疲劳寿命分析提供了研究基础。  相似文献   

5.
基于概率断裂力学理论和Mome Caflo模拟方法,本文进行了自紧身管临界裂纹尺寸的可靠性研究。自紧身管内表面的疲劳裂纹考虑为半椭圆形式。裂纹尖端处的应力强度因子由内压和自紧残余应力共同产生。自紧残余应力采用了符合身管材料具有强化和包辛格效应性能推导的公式计算,它产生的应力强度因子通过权函数方法得到。根据断裂准则,可计算出自紧身管的临界裂纹尺寸。实例分析表明,对数正态分布为临界裂纹尺寸的最佳分布,同时给出了在各种置信度和可靠度下自紧身管的临界裂纹尺寸。  相似文献   

6.
基于子模型法的带有表面裂纹钢丝应力强度因子研究   总被引:1,自引:1,他引:0  
钢丝裂纹应力强度因子是进行钢丝疲劳断裂寿命评估、疲劳裂纹扩展分析和钢丝断裂强度评估等工作的重要参数。本文首先介绍了裂纹扩展分析软件FRANC3D,然后基于子模型法模拟研究了拉伸荷载作用下带有表面裂纹钢丝的应力强度因子,裂纹种类包括直线形裂纹和半圆形裂纹,最后拟合得到拉伸荷载作用下带表面裂纹钢丝的应力强度因子形状修正系数表达式,分析了利用该公式进行承载力评估时产生误差的原因。研究结果表明,利用子模型模拟分析拉伸荷载作用下带有表面裂纹的钢丝应力强度因子时计算精度高,计算速度快,对计算机硬件要求低;利用该方法得到的钢丝裂纹应力强度因子,在进行索承式桥梁吊索安全性能评估时,评估结果更精确。  相似文献   

7.
以Donahue等提出的疲劳裂纹扩展速率计算模型为基础,通过引入形状系数、张开比和残余应力等参数,建立了适用于焊接结构的疲劳裂纹扩展速率计算模型,分析了多种因素对焊接结构疲劳裂纹扩展速率的影响规律。结果表明,焊板厚度和焊缝余高的变化均会对焊接结构疲劳裂纹的扩展速率产生影响,在对焊接结构表面形状进行设计时应保有一定的焊缝余高;有效应力比的增大会降低焊接结构疲劳裂纹的扩展速率,且裂纹深度的变化不会改变有效应力比对焊接结构疲劳裂纹扩展速率的影响;残余应力的增大会提高焊接结构疲劳裂纹的扩展速率,且残余应力对疲劳裂纹扩展速率的促进作用随着裂纹深度的增加而增大,在对焊接结构的疲劳性能进行设计时须考虑残余应力对结构性能的影响。  相似文献   

8.
查子初  王志群 《实验力学》1991,6(2):169-176
本文提供了一种可以进行自增强处理的圆筒试样,通过实验用柔度法确定了该试样的表面裂纹的应力强度因子,介绍了含表面裂纹试样的柔度测试技术,导出了柔度与表面裂纹尖端前缘各点的应力强度因子的关系式,该式可作为各种含表面裂纹试样柔度法测表面裂纹 K_1因子的参考,本文还测定了不同自增强程度下,自增强圆筒的表面裂纹疲劳扩展规律。  相似文献   

9.
通过聚碳酸酯紧凑拉伸试件的疲劳裂纹扩展速率试验和同时进行的光弹性实验,作者发现随着疲劳裂纹的扩展在裂纹尖端附近产生逐渐加强和扩大的残余应力场,揭示出了裂纹尖端附近的闭合效应的存在,它将使应力强度因子降低.因此,疲劳裂纹扩展过程中应力强度因子幅度△K 的理论值应该修正。本文提出了一种简便有效的修正方案.  相似文献   

10.
航空发动机压气机叶片振动疲劳裂纹扩展规律研究   总被引:1,自引:0,他引:1  
以某型航空发动机压气机2级转子叶片为例,研究了叶片的振动疲劳裂纹扩展规律。研究过程中,首先利用有限元方法分别计算了试验状态与工作状态下叶片振动导致的裂纹尖端应力强度因子范围随裂纹长度的变化;试验研究了裂纹扩展速率与裂纹长度的关系。之后,综合计算结果和试验结论,得出叶片试验状态与工作状态下的裂纹扩展规律,并与Paris公式进行了比较,发现叶片的振动疲劳裂纹扩展速率dad N是与裂纹长度a和裂尖应力强度因子范围IΔK相关的多项式,而Paris公式不能描述叶片的振动疲劳裂纹扩展现象。研究结论可进一步确定叶片的损伤容限、确定合理的叶片检修周期,为保障飞行安全奠定基础。  相似文献   

11.
Pressure vessels which are subjected to cyclic external or internal high pressure are used in many fields of industry and need to be sure of reliability and safety. To ensure of reliability and safety, thick-walled cylinder, such as a cannon or nuclear reactor, is autofrettaged to induce advantageous residual stresses. The compressive residual stress which was introduced by autofrettage process acts to offset the tensile residual stress induced by internal pressure. It increases operating pressure and restrains crack initiation and crack propagation. As the autofrettage level increases, the magnitude of compressive residual stress at the bore also increases. However, the Bauschinger effect reduces the compressive residual stresses with prior tensile plastic strain, and decreases the beneficial autofrettage effect. There are some differences between theoretical solution considering elastic-perfectly material behavior and real autofrettage process results. The purpose of the present paper is to predict the accurate residual stress of SNCM 8 high strength steel using the Kendall model which was adopted by ASME Code. The tensile and uniaxial Bauschinger effect tests of SNCM 8 were performed to evaluate Bauschinger effect factor(BEF), thereafter this constant was used in calculating the residual stress. The residual stress distribution which is considering the Bauschinger effect was profiled using Kendall model, and the results were compared with the analytical and Finite Element analysis. The results were found that residual stress incorporating the Bauschinger effect at bore was smaller than ideal calculation. These results should be considered in designing pressure vessels.  相似文献   

12.
自紧身管疲劳寿命的可靠性分析   总被引:1,自引:0,他引:1  
基于概率断裂力学理论和Monte Carlo模拟方法,给出了自紧身管疲劳寿命的可靠性分析方法.自紧残余应力采用了符合身管材料具有强化和包辛格效应性能推导的公式计算,身管工作的应力强度因子通过权函数方法得到.实例分析结果表明,对数正态分布为身管疲劳寿命的最佳分布,同时给出了各种置信度和可靠度下的身管疲劳寿命.另外,还分析了初始裂纹尺寸和材料的断裂韧性对身管疲劳寿命的影响.该研究对保证身管的安全,避免灾难性事故的发生具有重要意义.  相似文献   

13.
The transient thermal stress problem of an inner-surface-coated hollow cylinder with multiple pre-existing surface cracks contained in the coating is considered. The transient temperature, induced thermal stress, and the crack tip stress intensity factor (SIF) are calculated for the cylinder via finite element method (FEM), which is exposed to convective cooling from the inner surface. As an example, the material pair of a chromium coating and an underlying steel substrate 30CrNi2MoVA is particularly evaluated. Numerical results are obtained for the stress intensity factors as a function of normalized quantities such as time, crack length, convection severity, material constants and crack spacing.  相似文献   

14.
The singular stress problem of a peripheral edge crack around a spherical cavity in a long circular cylinder under torsion is investigated. The problem is solved by using integral transforms and is reduced to the solution of two integral equations. The solution of these equations is obtained numerically by the method due to Erdogan, Gupta, and Cook, and the stress intensity factors, and crack opening displacements are displayed graphically.  相似文献   

15.
基于数字散斑相关方法测定Ⅰ型裂纹应力强度因子   总被引:1,自引:0,他引:1       下载免费PDF全文
提出了一种通过数字散斑相关方法测定金属材料Ⅰ型裂纹尖端位置和应力强度因子的实验方法.实验采用疲劳试验机对含Ⅰ型缺口的Cr12MoV钢试件预制裂纹,通过数字散斑相关方法测试试件在三点弯曲加载条件下裂纹的扩展过程及裂尖区域的位移场.将位移场数据代入裂尖位移场方程组,采用牛顿-拉普森方法求解含未知参量的裂尖非线性位移场方程组,计算裂尖位置和应力强度因子.实验结果表明,采用该方法可以准确地测定金属材料Ⅰ型裂纹应力强度因子、裂尖位置及裂纹扩展长度,解决了以往研究中因不能准确测定裂纹尖端位置,而无法准确计算Ⅰ型裂纹裂尖断裂参数的难题,揭示了金属材料裂纹扩展过程中应力强度因子演化特征.  相似文献   

16.
The behavior of crack growth for the fatigue damage accumulation near tip where damage is most severe is analyzed. Fatigue life is assessed for the welded members of bridges under traffic loading. Two parts are considered. They consist of the development of a fatigue damage accumulation model for welded bridge members and a method for calculating the stress intensity factor that is needed for evaluating the fatigue life of welded bridge members with cracks. Based on the concept of continuum damage accumulation and fatigue and fatigue crack growth relations, results are obtained to describe the relationship between the cracking count rate and the effective stress intensity factor. Crack growth and fatigue life are found for two types of welded members assisted by using fatigue experimental results. The stress intensity factors are modified by correcting for the geometric shape of the welded members in order to reflect the influence of the weldment and geometry. This is accomplished via the stress intensity factor. The calculated and measured fatigue lives were generally in good agreement for the initial cracking conditions of two types of welded members widely used in steel bridges.  相似文献   

17.
In this paper,the functions of warping displacement interruption defined on the crack lines are taken for the fundamental unknown functions.The torsion problem of cracked circular cylinder is reduced to solving a system of integral equations with strongly singular kernels.Using the numerical method of these equations,the torsional rigidities and the stress intensity factors are calculated to solve the torsion problem of circular cylinder with star-type and other different types of cracks.The numerical results are satisfactory.  相似文献   

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