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本文研究了反平面机械载荷、面内电载荷和面内磁载荷作用下磁电弹材料中含有纳米尺度孔边任意位置贯穿裂纹的Ⅲ型断裂力学性能.基于Gurtin-Murdoch表面弹性理论考虑纳米缺陷(孔洞和裂纹)的表面效应,利用磁电弹理论和复变弹性理论获得了纳米缺陷表面为磁电不可通条件下磁电弹场的精确解,给出了贯穿裂纹两端裂尖的磁电弹场强因子的解析表达.所得结果与已有研究比较说明了本文方法的有效性.讨论了裂纹位置、裂纹相互作用与施加多物理场载荷对无量纲磁电弹场强因子的影响.结果表明:贯穿裂纹裂尖的无量纲磁电弹场强因子尺寸效应显著;缺陷表面效应对裂纹耦合尖端场的影响受裂纹位置的制约;无量纲磁电弹场强因子受贯穿裂纹两端的裂纹长度比与施加力电磁载荷的显著影响. 相似文献
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研究纳米尺度时开裂椭圆孔的III型断裂性能。基于表面弹性理论和保角映射技术,利用复势函数理论获得了缺陷(裂纹和椭圆孔)周围应力场和裂纹尖端应力强度因子的闭合解答。所得结果具有一般性,许多已有和新的解答可由本文退化的特殊情形得到。利用解析结果讨论了缺陷的绝对尺寸、椭圆孔的形状比以及裂纹的相对尺寸对应力强度因子的影响。结果表明:考虑表面效应且缺陷尺寸在纳米尺度时,应力强度因子具有显著的尺寸依赖效应;应力强度因子随椭圆孔形状比的变化规律受缺陷表面常数的影响;缺陷表面效应的影响取决于椭圆孔的形状比,非常大的形状比屏蔽了表面效应的影响;裂纹相对尺寸非常小时表面效应影响较弱,裂纹相对尺寸较大时表面效应较为明显。 相似文献
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通过引入合适的数值保角映射,利用Stroh型公式研究一维六方压电准晶中正三角形孔边裂纹的反平面问题,给出在电非渗透边界条件下三角形孔边裂纹尖端的场强度因子和能量释放率。通过数值算例,讨论场强度因子和能量释放率随缺陷几何尺寸和力电荷载的变化规律。结果表明:随孔边裂纹长度的增加,场强度因子先急剧增加后减小,并趋于定值1,正三角形孔洞的尺寸对其影响可忽略不计;声子场和相位子场机械载荷总是促进裂纹扩展,而电位移对裂纹的扩展极大地依赖于声子场和相位子场载荷的大小。 相似文献
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基于Bernoulli-Euler梁振动理论,以等效弹簧来模拟裂纹引起的局部软化效应和由非完全固支边界条件引起的转角效应。推导了悬臂梁在不确定边界条件下确定其振动频率的特征方程,直接利用该特征方程,提出一种有效估计裂纹参数的优化方法,通过计算测量频率和理论频率之间的误差目标函数最小化即可识别裂纹参数-裂纹位置和深度。最后,应用两个实例-理想固支边界条件下和非完全固支边界条件下的悬臂梁实验来说明本文方法的有效性。实验结果表明:只需梁结构前三阶频率即可识别裂纹位置和深度。对于理想边界条件下的裂纹参数识别,在测量频率存在小误差情况下,该方法仍能给出比较满意的结果,对于非完全固支边界条件下的裂纹参数识别,利用本文方法能得到比Narkis的方法更精确的裂纹位置识别结果。同时本文方法还能给出比较满意的裂纹深度识别结果。 相似文献
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各向异性压电材料平面裂纹的耦合场分析 总被引:4,自引:1,他引:3
用Stroh方法分析了各向异性压电材料电导通型裂纹问题的耦合场。结果表明,裂纹面上的切向电场强度和法向电位移均为常数,在裂纹尖端有由弹性场的耦事作用产生的奇异电导通裂纹模型中的静电场对裂纹尖端扩展的能量释放率不作贡献。 相似文献
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WangBaolin HanJiecai DuShanyi 《Acta Mechanica Solida Sinica》2004,17(4):290-296
The electrical boundary conditions on the crack faces and their applicability in piezoelectric materials are discussed. A slit crack and a notch of ?nite thickness in piezoelectric materials subjected to combined mechanical and electrical loads is consi… 相似文献
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《International Journal of Solids and Structures》2007,44(2):387-398
This paper discusses the different electromagnetic boundary conditions on the crack-faces in magnetoelectroelastic materials, which possess coupled piezoelectric, piezomagnetic and magnetoelectric effects. A notch of finite thickness in these materials containing air (or vacuum) is also addressed. Four ideal crack-face electromagnetic boundary condition assumptions, that is, (a) electrically and magnetically impermeable crack, (b) electrically impermeable and magnetically permeable crack, (c) electrically permeable and magnetically impermeable crack and (d) electrically and magnetically permeable crack, are investigated separately. The influence of notch thickness on the field intensity factors at notch tips and the electromagnetic field inside the notch are obtained in closed-form. The results are compared with the ideal crack solutions. Applicability of crack-face electromagnetic boundary condition assumptions is discussed. 相似文献
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The applicability and effect of the crack surfaces thermoelectric boundary conditions in thermopiezoelectric fracture mechanics problem are discussed by using the finite thickness notch approach. The stress and electric displacement intensity factors at the notch tips, and thermal flux and electric displacement inside the notch are derived in closed-form. The numerical results are compared with the ideal crack solutions. It is found that the electrically impermeable crack boundary condition assumption is reasonable if the flaw in the material is a notch with finite width, and the thermal conductivity of air or vacuum inside the crack must be considered. 相似文献
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This paper discusses electromagnetic boundary conditions on crack faces in magneto- electroelastic materials, where piezoelectric, piezomagnetic and magnetoelectric effects are coupled. A notch of finite thickness in these materials is also addressed. Four idealized electromagnetic boundary conditions assumed for the crack-faces are separately investigated, i.e. (a) electrically and magnetically impermeable (crack-face), (b) electrically impermeable and magnetically permeable, (c) electrically permeable and magnetically impermeable, and (d) electrically and magnetically permeable. The influence of the notch thickness on important parameters, such as the field intensity factors, the energy release rate at the notch tips and the electromagnetic fields inside the notch, are studied and the results are obtained in closed-form. Results under different idealized electromagnetic boundary conditions on the crack-face are compared, and the applicability of these idealized assumptions is discussed.The project supported by the National Natural Science Foundation of China (10102004) The English text was polished by Yunming Chen. 相似文献
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The dynamic response of an interfacial crack between two dissimilar magnetoelectroelastic layers is investigated under magnetic, electrical and mechanical impact loadings. Four kinds of ideal crack-face assumptions, i.e., magnetoelectrically impermeable (Case 1), magnetically impermeable and electrically permeable (Case 2), magnetically permeable and electrically impermeable (Case 3) and magnetoelectrically permeable (Case 4), are adopted separately. The dynamic field intensity factors and energy release rates are derived. The effects of loading combinations and crack configurations especially for the former on the dynamic response are examined according to energy release rate criterion. The numerical results show that, among others, a negative magnetic (or electrical) loading is generally prone to inhibit the crack extension rather than a positive one for a magnetically (or electrically) impermeable interfacial crack. Results presented in this paper should have potential applications to the design of multilayered magnetoelectroelastic structures. 相似文献
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《Acta Mechanica Solida Sinica》2015,(2)
The extended finite element method is used to analyze a plate with two parallel edge cracks impacted by a cylindrical projectile. The influence of the impact speed, crack length,plate thickness and notch tip radius on the crack initiation and propagation is studied. Dynamics equations are solved by an implicit time integration scheme which is unconditionally stable. Very good agreement is achieved between numerical predictions and experimental results. The critical velocity of the crack initiation under different conditions is examined. The influence of the crack length is greater than that of the impact speed, plate thickness and notch tip radius. 相似文献
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《International Journal of Solids and Structures》2005,42(18-19):5118-5128
This paper investigates the interaction problem between a dislocation and a finite crack in piezoelectric media. Analytical solutions for the generalized two-dimensional problem of a dislocation that is interacting with a finite crack in piezoelectric media are formulated via Stroh formalism. The analysis is conducted on the unified electrical crack boundary condition with the introduction of the electric crack condition parameter that can describe all the electric crack boundary conditions. The two ideal crack boundary conditions, namely, the electrically impermeable and permeable crack assumptions are obtained as two special cases for the current solutions. Based on the complex variable method and the perturbation technique, closed form solutions are obtained. The field intensity factors at the crack tip and the image forces on the dislocation due to the crack are computed and discussed. 相似文献
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Summary This paper investigates the problem of an anti-plane interfacial crack between two dissimilar piezoelectric material layers. A single crack is first considered. The effect of interaction of two collinear cracks in the medium on the field intensity factors is investigated. The solutions of several particular cases, including an infinite piezoelectric bi-material and a piezoelectric material bonded to an elastic medium, are given. The bi-material constants governing the behavior of the crack tip fields are identified. By considering the crack as a notch of finite thickness, it is shown that the thickness of the notch has a pronounced influence on the crack tip field. The results for the assumption of a permeable crack represent the limit case where the notch thickness is reduced to zero.BLW would like to thank the National Science Foundation of China (#10102004) and the City University of Hong Kong (DAG #7100219) for the support of this work. YGS also thanks the Multidiscipline Scientific Research Foundation Project (HIT. MD 2001. 39) of the Harbin Institute of Technology and the SRF for ROCS, SEM.accepted for publication 3 April 2003 相似文献
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Summary A finite crack propagating at constant speed in a functionally graded piezoelectric strip (FGPS) bonded to a homogeneous piezoelectric strip is considered. It is assumed that the electroelastic material properties of the FGPS vary exponentially across the thickness of the strip, and that the bimaterial strip is under combined anti-plane mechanical shear and in-plane electrical loads. The analysis is conducted for the electrically unified crack boundary condition, which includes both the traditional permeable and the impermeable ones. By using the Fourier transform, the problem is reduced to the solution of Fredholm integral equations of the second kind. Numerical results for the stress intensity factor and the crack sliding displacement are presented to show the influences of the crack propagation speed, electric loads, FGPS gradation, crack length, electromechanical coupling coefficient, properties of the bonded homogeneous piezoelectric strip and crack location. 相似文献
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Tong-Yi Zhang 《Acta Mechanica Sinica》2002,18(5):537-550
The paper gives an overview on experimental observations of the failure behavior of electrically insulating and conducting
cracks in piezoelectric ceramics. The experiments include the indentation fracture test, the bending test on smooth samples,
and the fracture test on pre-notched (or pre-cracked) compact tension samples. For electrically insulating cracks, the experimental
results show a complicated fracture behavior under electrical and mechanical loading. Fracture data are much scattered when
a static electric field is applied. A statistically based fracture criterion is required. For electrically conducting cracks,
the experimental results demonstrate that static electric fields can fracture poled and depoled lead zirconate titanate ceramics
and that the concepts of fracture mechanics can be used to measure the electrical fracture toughness. Furthermore, the electrical
fracture toughness is much higher than the mechanical fracture toughness. The highly electrical fracture toughness arises
from the greater energy dissipation around the conductive crack tip under purely electric loading, which is impossible under
mechanical loading in the brittle ceramics.
The project supported by an RGC grant from the Research Grant Council of the Hong Kong Special Administrative Region, China 相似文献