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1.
Liviu Marsavina Tomasz Sadowski Nicolae Faur 《Journal of Mechanical Science and Technology》2011,25(2):309-315
Ceramic-metal interfaces are often present in composite materials. The presence of cracks has a major impact on the reliability
of advanced materials, such as fiber or particle reinforced ceramic composites, ceramic interfaces and laminated ceramics.
The understanding of the failure mechanisms is very important, as is as the estimation of fracture parameters at the tip of
the crack approaching an interface and crack propagation path. A cracked sandwich plate loaded with axial uniform normal stress
was numerically investigated using plane strain Finite Element Analysis. The numerical results for the singularity orders
were compared with the analytical solution. The influences of the material combination and crack length on the radial and
circumferential stresses and displacement distributions were investigated. The Stress Intensity Factors were determined based
on numerical results using a displacement extrapolation method. The results for the non-dimensional stress intensity factors
show that at lower crack lengths the influence of material mismatch is lower, but this influence increases with increasing
crack length. 相似文献
2.
Seog Young Han M. N. L. Narasimhan T. C. Kennedy 《Journal of Mechanical Science and Technology》1989,3(2):103-112
The dynamic propagation of a finite crack under mode-1 loading in a micropolar elastic solid is investigated. By using an
integral transform method, a pair of two-dimensional singular integral equations governing stress and couple stress is formulated
in terms of displacement transverse to the crack, macro and micro rotations, and microinertia. These equations are solved
numerically, and solutions for dynamic stress intensity and couple stress intensity factors are obtained by utilizing the
values of the strengths of the square root singularities in macrorotation and the gradient of microrotation at the crack tips.
The motion of the crack tips and the load on the crack surface are not prescribed in the formulation of the problem. Therefore,
the method of solution is applicable to nonuniform rates of propagation of a crack under an arbitrary time-dependent load
on the crack surface. As an example, the diffraction of a micropolar dilatational wave by a stationary crack is considered.
The behavior of the microrotation field and the dynamic couple stress intensity factor, influenced by microinertia, in addition
to the dynamic stress intensity factor, are examined. The classical elasticity solution for the corresponding problem arises
as a special case when the micropolar moduli are dropped from the present solution. 相似文献
3.
The problem of stress concentration in bi-material bonded joint is investigated under the condition of without stress singularities. Disappearance conditions of stress singularity near interface corners and edges are determined based on analyses of eigenvalue equations. Straight-side and curved interface of materials are designed for the bi-material models to avoid singular stress fields around the interface corner and edge. Assuming that one stress component or combined stresses are responsible for failure at or near the interface, the stress concentration becomes critical for the design of bi-material joints with higher interfacial strength. Numerical results show that the stress state near the interface depends strongly on both the interface geometry and the combination of materials, and stress concentration may always occurs at or near the interface. Emphasis is placed on the necessity for geometric optimization of an interface in order to design singularity-free junction with higher interfacial strength. 相似文献
4.
Kwang Ho Lee Young Jae Lee Sang Bong Cho 《Journal of Mechanical Science and Technology》2009,23(5):1306-1322
When a crack propagates with acceleration, deceleration and time rates of change of stress intensity factors, it is very important
for us to understand the effects of acceleration, deceleration and time rates of change of stress intensity factors on the
individual stresses and displacements at the crack tip. Therefore, the crack tip stress and displacement fields for a transiently
propagating crack along gradient in functionally graded materials (FGMs) with an exponential variation of shear modulus and
density are developed and the characteristics of a transiently propagating crack from the fields are analyzed. The effects
of the rate of change of the stress intensity factor and the crack tip acceleration on the individual stresses at the crack
tip are opposite each other. Specially, the isochromatics (constant maximum shear stress) of Mode I tilt backward around the
crack tip with an increase of crack tip acceleration, and tilt forward around the crack tip with an increase of the rate of
change of the dynamic mode I stress intensity factor.
This paper was recommended for publication in revised form by Associate Editor Chongdu Cho
Kwang-Ho Lee received a Ph.D. degree in Yeungnam University in 1993. Dr. Lee is currently a professor at the School of Mechanical and
Automotive Engineering at Kyungpook National University in Korea. He also had worked in KOMSCO as an engineer and researcher
(1982.3–1996.2). He is interested in the fields of fracture and stress analysis on the composite, interface, nano and functionally
graded materials by theoretical and experimental mechanics. Specially, his major interest is analysis of dynamic crack tip
fields.
Young-Jae Lee received his B.S degree in Agricultural Civil Engineering from Gyeongsang National University (GNU) in 1982. He then received
his M.S. and Ph.D. degrees from GNU in 1984 and 1995, respectively. Dr. Lee is currently a professor at the department of
Civil Engineering at Kyungpook National University in Korea. From 2005 to 2006, he had served as an editor of Korea Institute for Structure Maintenance and Inspection. His research interests are in the area of evaluation, diagnosis and optimum design of structure.
Sang-Bong Cho received a Ph. D. degree from Tokyo University in 1989. Dr. Cho is currently a professor at the division of Mechanical and
Automation Engineering at Kyungnam University in Korea. His research interests are in the area of fracture mechanics, FEM
stress analysis and fretting fatigue. 相似文献
5.
使用边界积分方程方法,在有限部积分的意义下,将弹性半空间中垂于自边界面的平片裂纹归结为一组以裂纹面位移间数为示知函数的超奇异积仞氖限部积分蜞 建立了数值人出了用裂纹面位移间尖力强度因子的公式。通过对圆形、菜和矩形等贡型的平片裂纹问题的计算,分析了自由边界面对裂纹前沿应力强度因子的影响。 相似文献
6.
给出计算一般平面裂纹问题应力强度因子的半权函数方法。该方法引入两个满足裂纹面零应力条件、平衡方程以及裂尖位移具有r^-1/2奇异性的虚拟位移与应力函数的解析表达式,即半权函数。从功能互等定理出发,结合从裂纹下缘到上缘绕裂尖任意路径的位移与应力的近似值,得到Ⅰ、Ⅱ复合型应力强度因子KⅠ和KⅡ积分形式的表达式。由于在积分中避开了裂尖的奇异性,因此即使采用较粗糙的模型或方法得到的近似值,也可以得到精度较高的KⅠ、KⅡ。相对于权函数法,本方法的限制条件较少,半权函数易于获得,实用性强;相对于有限元法计算量小,模型建立简便。 相似文献
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This paper presents the dynamic magnetoelastic stress intensity factors of a Yoffe-type moving crack at the interface between two dissimilar soft ferromagnetic elastic half-planes. The solids are subjected to a uniform in-plane magnetic field and the crack is opened by internal normal and shear tractions. The problem is considered within the framework of linear magnetoelasticity. By application of the Fourier integral transform, the mixed boundary problem is reduced to a pair of integral equations of the second kind with Cauchy-type singularities. The singular integral equations are solved by means of a Jacobi polynomial expansion method. For a particular case, closed-form solutions are obtained. It is shown that the magnetoelastic stress intensity factors depend on the moving velocity of the crack, the magnetic field and the magnetoelastic properties of the materials. 相似文献
11.
Stress and displacement fields for an unsteadily propagating crack under mode I and II loading are developed through an asymptotic
analysis. Dynamic equilibrium equations for the unsteady state are developed and the solution to the displacement fields and
the stress fields for a crack propagating with high crack tip acceleration, deceleration and rapidly varying stress intensity
factor. The influence of transients on the higher order terms of the stress fields are explicitly revealed. Using these stress
components, isochromatic fringes around the propagating crack are generated for different crack speeds, crack tip accelerations
and the time rate of change of stress intensity factor, and the effects of the transients on these fringes are discussed.
The effects of the transients on the dynamic stress intensity factor are discussed when a crack propagates with high acceleration
and deceleration. The effect of transient on the time rate of change of dynamic stress intensity factor below Rayleigh wave
speed in an infinite body is also studied. 相似文献
12.
Lijun Zhang Yongrui Zhao Hengfu Xiang 《The International Journal of Advanced Manufacturing Technology》2013,65(1-4):549-555
For carrying out the precise cropping of metal bar with different geometrical sizes, it is very important to obtain the reasonable stress intensity factor of V-shaped notch tip rapidly and accurately. At first, a new precise cropping method, which is the high-speed peripheral low-stress bending fracture cropping is presented in the paper, and its working mechanism is also given in detail. The stress field near V-shaped notch tip is analyzed, and the stress extrapolation method is presented to compute the stress intensity factor of V-shaped notch tip. Based on it, the correctional expression of theoretical stress intensity factor in a handbook of stress intensity factor is also given. The contrasts between stress intensity factor results obtained by means of the stress extrapolation method and the corresponding theoretical results in the handbook of stress intensity factor are also carried out in detail. The results show that the two errors are not more than 5 % and are within a reasonable engineering range. The cropping experimental results for initial loading force and crack propagation life have also confirmed that the correctional expression of theoretical stress intensity factor is feasible. 相似文献
13.
从研究环形界面双相材料平面任点处沿径向、环向作用单位力时的弹性力学基本解出发,利用Betti定律、几何关系和虎克定律得到双材料平面环向裂纹问题的位移场和应力场表达式,经代入裂纹岸应力边界条件,导出极坐标下以裂纹岸位移间断为基本未知量的超奇异积分方程组;通过适当的积分变换,用有限部积分原理处理方程组中所包含的两类奇异积分—Cauchy奇异积分和超奇异积分,解决极坐标下环形界面双材料平面环向裂纹问题用超奇异积分方程法的理论描述与数值算法。在嵌入物半径足够大时,计算结果与已发表文献对直线界面情况下平行于界面裂纹问题的计算结果一致。 相似文献
14.
研究一种平面六节点应力奇异单元的计算精度问题。首先证明该单元具有1/槡r阶奇异性,然后用此单元计算同质材料中的裂纹和双材料界面裂纹的应力强度因子与裂尖应力分布,讨论裂纹尖端奇异单元的尺寸以及在奇异单元与常规单元之间布置一层过渡单元对精度的影响。研究发现,当布置在裂尖的奇异单元边长与裂纹长度的比值在0.1~0.2时,能得到足够精确的解答;而在此范围之外,随奇异单元尺寸进一步增大或减小,精度都会有所下降。对于同质材料中的裂纹以及模量比在10倍之内的双材料界面裂纹,布置过渡单元可以提高精度;而对于模量比大于20倍的界面裂纹,不设置过渡单元的计算结果却与理论解更接近。 相似文献
15.
高精度求解应力强度因子的数值外插法 总被引:7,自引:3,他引:4
首先介绍求解应力强度因子的传统蜕化奇异等参元法和一种新型的数值外插法,两种方法均在裂尖使用精度较高的蜕化奇异二次等参元,考虑到传统方法受裂尖单元尺寸大小,结构物类型,材料泊松比影响较大等缺陷,新方法使用了不同的插值手段。其次,讨论了两种方法插值基础的显著区别,结合空间Ⅰ型裂纹问题论证了新型数值外插法的插值基础,研究了两种方法的理论插值误差,发现本文提出的数值外插法比传统的蜕化奇异等参元法的理论精度高一阶,最后,对两种方法的计算误差进行了探讨。数值外插法考虑到有限元计算断裂问题的误差,能以一定的方式决定不同裂纹问题的优化裂尖单元尺寸。 相似文献
16.
含埋藏椭圆型裂纹的构件脉冲放电瞬间的耦合场分析 总被引:1,自引:0,他引:1
采用数值分析的方法,对含三维埋藏椭圆型裂纹的构件放电瞬间的耦合场进行分析。计算脉冲放电瞬间椭圆形裂纹尖端附近的温度场和等效应力场的分布状态;并通过改变模型尺寸的模拟分析影响放电参数的主要因素。计算结果表明,由于电流绕流产生的焦耳热源的作用,裂纹尖端处温度瞬时急剧升高,但沿椭圆形裂纹尖端的温度值并不相同,最大值发生在长轴附近,只要放电电流的强度足够大,可以使椭圆环形裂尖均熔化形成焊口,并围绕环形裂纹尖端附近产生很大的热压应力场,可有效地遏制裂纹的扩展;在相同放电电流强度下,对椭圆裂纹尖端温度影响较大的是裂纹的绝对尺寸和椭圆长短轴的相对尺寸。在研究过程中分成热一电耦合和热一应力耦合两个过程,综合考虑材料非线性、状态变化非线性和几何非线性,结果比较符合实际。 相似文献
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18.
复合材料补片参数对裂纹尖端应力强度因子的影响 总被引:2,自引:0,他引:2
利用有限元法对复合材料补片修补前后的铝合金薄板的裂纹尖端应力强度因子KI进行研究,分析各类补片参数对裂纹尖端应力强度因子的影响.结果表明,在正确选择复合材料补片的参数后,修补后铝合金板裂纹尖端的应力强度因子有显著地下降. 相似文献
19.
围绕V形切口尖端裂纹起裂方向,分析了V形切口尖端裂纹应力场、位移场、应力强度因子,提出了裂纹起裂方向的主应力判别准则。首先,详细给出了V形切口尖端应力应变场的求解方法,通过裂纹尖端场本征值的三次线性拟合及误差分析,确定了V形切口尖端裂纹位移场;然后,建立了V形切口尖端的数值分析模型,运用数值计算方法确定了应力强度因子和切口强度因子,提出了V形切口尖端裂纹起裂方向的主应力判断准则,给出了外推法求解分析过程;最后,以LY8为试验材料,在张角2β=60°的V形切口情况下,对提出的V形切口尖端裂纹起裂方向计算方法与判别准则进行了试验验证。 相似文献