搜索到2326篇“ CRACK-TIP“的相关文章
Geometry independent C^(*)-T_(z) dominance of three-dimensional quasistatic growing crack-tip fields in creeping solids
2022年
In creeping solids,plane stress and plane strain solutions for asymptotic singular crack-tip fields have been first put forward by Riedel and Rice with C^(*)as the dominating parameter and developed by Xiang and Guo into three-dimensional solution(3D)for stationary cracks under the domination of C^(*)with the constraint factor Tz.However,how to characterize the 3D crack-tip fields under creep damage-induced quasistatic growing conditions remains challenging.In this study,we reveal that,for 3D quasistatic growing cracks,the leading singular solution can effectively characterize the crack-tip stress distributions with relative errors less than 10.8%for relative creep time up to 0.8 in various specimens with finite thickness.For a given relative time,Tz distributions can be unified by the equivalent thickness concept,Beq.The results show that C^(*)-T_(z) can effectively quantify both the load and constraint effects on the crack-tip fields.Such geometry independent dominance can considerably simplify the treatments of load and constraint effects,thereby promoting the application of fracture mechanics in high-temperature damage tolerance designs.
PengFei CuiWanLin Guo
不同材料延性断裂韧性与裂尖拘束的关联及其影响因素分析被引量:5
2022年
基于不同材料、不同几何尺寸试样的延性断裂韧性数据,结合有限元计算,研究得到不同材料的标称化延性断裂韧性J_(c)/J_(ref)与统一拘束参数A_(d)之间的线性关联方程,其可用于基于J-A_(d)二参数法纳入面内/面外统一拘束的结构断裂预测和评定中。进一步基于GTN(Gurson-Tvergaard-Needleman)延性损伤模型的有限元法,数值分析了影响材料J_(c)/J_(ref)-A_(d)关联线的因素。结果表明,影响材料J_(c)/J_(ref)-A_(d)关联线的主要因素包括材料的应变硬化指数n,屈服强度σ_(0)和断裂特性。其中n对J_(c)/J_(ref)-A_(d)关联线斜率的影响最大;断裂特性的影响次之;σ_(0)的影响最小。低硬化指数n,低断裂阻力和低屈服强度σ_(0)的材料的延性断裂韧性对裂尖拘束的变化较敏感。对于这类材料的结构,在断裂预测和评定中要着重考虑裂尖拘束对断裂韧性的影响。
赵家鑫王国珍涂善东轩福贞
关键词:断裂韧性力学性能
Numerical Analysis of Crack-Tip Fields using a Meshless Method in Linear Elastic Materials
2022年
In this paper,the Discrete Least Squares Meshless(DLSM)method is developed to determine crack-tip fields.In DLSM,the problem domain and its boundary are discretized by unrelated field nodes used to introduce the shape functions by the moving least-squares(MLS)interpolant.This method aims to minimize the sum of squared residuals of the governing differential equations at any nodal point.Since high-continuity shape functions are used,some necessary treatments,including the visibility criterion,diffraction,and transparency approaches,are employed in the DLSM to introduce strong discontinuities such as cracks.The stress extrapolation and J-integral methods are used to calculate stress intensity factors.Three classic numerical examples using three approaches to defining discontinuities in the irregular distribution of nodal points are considered to investigate the effectiveness of the DLSM method.The numerical tests indicated that the proposed method effectively employed the approaches to defining discontinuities to deal with discontinuous boundaries.It was also demonstrated that the diffraction approach obtained higher accuracy than the other techniques.
Zahra SheikhiAkbar GhanbariMohammad KarkonSoleyman Ghouhestani
Fracture behavior dependent on crack-tip shapes in nanoscale crack-defect monolayer boron nitride sheets
2021年
Nanoscale defects,including cracks,circular holes,and the triangular-shaped defects,often occur in the growth of boron nitride nanosheets(BNNS).In this study,the fracture behavior of chiral BNNS with different crack-tip shapes and the interactions of nanoscale crack-defects are studied using molecular dynamics(MD)simulations and finite element(FE)analysis.Both MD and FE results indicate that the fracture strength of BNNS with two crack tips(t=2)is significantly higher than that with one crack tip(t=1),in which the difference in zigzag(ZZ)direction is more obvious than that in armchair(AC)direction,mainly due to the fact that the change of bond angles near the crack tips is more substantial in the ZZ direction than those in the AC direction.Our results show that the fracture strength of BNNS strongly depends on crack-tip shapes,chiral angles,the defect-to-crack tip spacing and deflection angles.Checking against the current MD simulations and FE analysis shows the present results are reasonable.This study should be of great importance for enhancing the fracture performance of BNNS by modulating their crack-tip shapes and the interactions of nanoscale crack-defects.
Wentao SuChunhua ZhuAnping HuaShanchen LiJunhua Zhao
固体推进剂药柱点火瞬态裂纹尖端场研究被引量:3
2021年
采用线粘弹性模型,开展了药柱点火瞬态的动态裂纹尖端场仿真研究。结果表明,在裂尖及附近很小的区域内存在应力奇异性,且裂纹前端主要受拉应力的作用。裂尖应力应变随距裂尖距离r的增加而逐渐减小并趋于一定值;在θ处于0°~90°时,最大主应力和环向应变随θ的增大逐渐增大,而在θ处于90°~180°时则随着θ的增加而逐渐减小。在有限元计算结果的基础上得到了裂尖区域的张开型应力分布并计算了动态应力强度因子值,同文献中获得的推进剂动态断裂韧性结果进行比较,预测了裂纹的起裂危险性。
龙兵高双胜金伟
关键词:药柱裂纹尖端场点火瞬态
正交异性板裂纹端部应力及变形通解被引量:5
2020年
本文根据正交异性板的力学性能,确定平面应力弹性力学的基本方程,利用复变函数方法求解含裂纹正交异性板的应力边值问题。采用I型裂纹作为典型实例,讨论了裂纹端部应力与变形的一般解法,推导出正交异性板的奇异应力和应变场,并得到裂纹张开位移与材料特性的关系。
贾普荣
关键词:正交异性板复变函数裂纹张开位移
端点衍射法测量表面开口缺陷深度试验研究
2020年
介绍了一种金属零部件表面开口裂纹深度的超声波测量方法,利用裂纹端点衍射、端角反射原理,可直接在预先校准好时基线的数字式超声检测仪的屏幕上读出裂纹的深度。在钢材料中制作了不同深度的人工裂纹,并用此方法测量其裂纹深度。结果表明,该方法可以测量出深度不小于3mm的裂纹,而且其他裂纹的测量值与实际值相近。此方法操作方便,裂纹深度直读,可应用于有限空间(如在役飞机机舱内)金属零部件表面开口裂纹的深度测量。
韩建宁王珏段宏伟张德智陈舒颖
关键词:超声检测横波
考虑变温效应的重力坝裂纹尖端场有限元分析
2020年
本文基于ABAQUS对刘家峡水电站含有裂纹的非溢流坝段进行有限元模拟分析,考虑由于季节变化引起的变温效应,获得了裂纹诱导的热应力场。结果表明,裂纹前沿应力场随着温度的变化而变化,与不考虑温度场的情形比较,变温引起的应力集中能够导致裂纹扩展,所得结论能为大坝的寿命估计提供一定的参考依据。
陈佳烨钟献词钟献词
关键词:重力坝温度场数值模拟
正交异性材料平面裂纹尖端应力场被引量:3
2020年
根据正交各向异性材料力学性能确定出了用应力函数表示的弹性力学基本方程,利用坐标变换和复变函数方法求解了正交异性材料平面裂纹体的应力边值问题。借鉴一般断裂力学解法构造了I型和II型裂纹问题的应力函数,推导出了正交各向异性板裂纹尖端区的奇异应力场。通过数值计算说明了裂纹尖端应力表达式的正确性,验证了裂尖前沿应力变化规律,即σx与材料特征参数h2成正比,而σy和τxy不随材料特性变化。
贾普荣锁永永
关键词:正交异性材料应力函数奇异应力场
正交异性材料I + II + III混合型裂纹尖端应力分析被引量:2
2020年
大多数工程材料显示出脆性特征(例如,复合材料),而脆性材料中的裂纹已公认为是工程结构破坏的主要原因,裂纹尖端应力场必然是建立断裂判据的基础。因此,本文重点讨论I + II + III混合型加载下的裂纹尖端应力,采用线弹性力学方法解决正交异性材料典型应力边值问题。首先确定三维空间问题的弹性力学基本方程,基于复变函数理论求解控制方程。接着利用应力函数和坐标变换求解基本方程。最终获得了混合型加载下正交异性材料裂纹尖端附近的应力分量通解。
贾普荣
关键词:正交异性材料弹性力学复变函数