积分方程法对含复杂孔形复合材料板孔边应力分布的研究

根据非均质各向异性弹性理论对含复杂孔形复合材料板进行孔边应力分析,解决复杂孔形的边界条件问题.建立基于准确的边界条件的边界积分方程,最终得到开口结构的应力分布,给出含六边形、矩形和机翼检修孔复合材料板的精确解析解,并用有限元方法进行对比计算.平面应力场借助保角映射的方法通过复变应力函数得到.     

含工程中常见孔型复合材料板孔边应力场分析

针对含不同孔型复合材料板,根据非均质各向异性弹性理论和复变函数理论,提出了积分方程法求解方案。建立了相应的数学模型,对含不同孔型复合材料板进行了孔边应力分析,通过保角映射方法建立精确的边界条件,解决了复杂孔型的边界条件问题,借助仿射变换能同时并且同方法的处理这两个应力函数在边界上的问题。建立了基于准确的边界条件的边界积分方程分析体系,最终得到开口结构的应力分布。给出了含矩形和八边形孔复合材料板的精确解析解。并针对不同的荷载状况,以及它们对矩形和八边形孔边应力集中系数的影响进行探讨。     

连接结构的孔边强化层对复合材料含孔板失效过程的影响

在实际工程中,复合材料开口孔周围应力集中现象十分严重,使孔边极易发生破坏,且破坏形式多种多样.为提高含孔复合材料板的结构强度,可在孔边铺设一层一定厚度的材料,用来强化含孔板的承载能力.以三维逐渐损伤理论为基础,采用商用软件ANSYS的二次开发语言,建立对复合材料含孔板进行孔边结构强化的模型,在拉伸载荷下对具有强化结构的...     

含孔各向异性板的孔边应力场分析

根据非均质各向异性弹性理论对含机翼检修孔复合材料板进行了孔边应力分析，解决了复杂孔形的边界条件问题，得到了精确解析解。对工程应用中常见的几种荷载状况（在不同纤维方向，不同加载形式、加载方向情况下）对孔边应力集中系数的影响进行了探讨。采用有限元法进行了对比计算。     

不同荷载作用下圆孔板孔边及孔口附近应力场的仿真分析

建立了基于弹性理论及复变函数理论的计算模型。利用所建立的计算模型对孔边应力场进行了分析,同时也对孔口附近的各应力分量进行了较为全面的计算,得到了一些有益的结论。对孔边各应力分量进行了比较,同时也对距孔边不同距离时的应力场进行了比较。另外,通过施加不同的荷载,对孔边的应力场以及距孔边不同距离时的应力场的影响进行了研究。     

预紧力作用下受拉层合板孔边接触问题研究

预紧力作用下受拉复合材料层合板连接件的孔边受载情况发生变化,对结构承载性能产生一定影响,以单钉双剪复合材料层合板为研究对象,给出了复合材料层合板螺栓连接孔边不同区域的接触边界条件,在此基础上建立三维有限元模型,对预紧力影响下的单钉双剪板孔边应力进行求解,获得了不同预紧力下孔边面内接触应力沿孔分布规律。结果表明:随着预紧力增加在连接孔的孔边接触区、过渡区和大部分非接触区,面内应力水平不断降低,但在孔的160°到180°的非接触区孔边应力取值出现一定上升趋势。     

机械连接结构中紧固件附近的力学性能

在经典弹性力学和弹簧模型方法的基础之上,采用ANSYS三维有限元方法,对单排多钉连接结构的钉载分配、孔边危险点的应力情况进行了分析,研究了影响钉载分配关系与孔边应力分布情况的主要因素,包括板厚、材料性能、构件尺寸及连接工艺等,重点探讨了板厚、材料刚度对孔边应力集中的影响。     

复合材料螺栓连接失效分析

复合材料螺栓连接的孔边应力分布和其失效模式的关系一直是机械连接强度分析中十分重要的问题,不同的失效模式区域所受的应力是不同的。首先采用了适当的孔边应力函数获得了失效区域孔边径向正应力、切向正应力和剪切应力的分布,分析了不同失效模式(挤压失效、剪切失效和拉伸失效)和其所受应力的关系。随后基于螺栓连接的三维实体有限元模型,将有限元分析的结果和解析法得出的结论进行了比较,发现的解析法计算的结果和有限元结果吻合良好,验证了复合材料螺栓连接的不同失效模式和其所受应力的关系。这表明复合材料螺栓连接不同的失效模式是由不同的应力所导致的。     

复合材料开孔层合板有限元网格划分方法研究

对复合材料开孔层合板有限元建模过程中网格划分方法进行量化研究。应用参数化的方法建立多种板宽孔径比、多种铺层比例的开孔层合板模型,逐级调整网格密度,计算单轴拉伸载荷作用下孔边最大应力集中系数。根据有限元结果,结合牛顿插值的数值计算方法,模拟出开孔层合板合理的网格密度划分方程。然后,对该网格划分方程下计算的数值解进行试验验证与解析解验证。结果表明,这种网格密度划分方程能有效地降低计算误差,可以在板宽孔径比大于3的复合材料开孔层合板的有限元计算中广泛使用。     

单向拉伸有限板中心椭圆孔边裂纹应力强度因子的估算近似公式

在现有的有限宽板修正系数公式的基础上，通过有限元计算分析，给出了一个较为理想的有限宽板修正系数公式。结合文中的无限板中心椭圆孔边裂纹的应力强度因子估算式，能很好地解决有限宽板中心椭圆孔边裂纹的应力强度因子的计算。有限元计算表明公式具有足够的精度。     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

SOLUTION OF DIFFERENT HOLES SHAPE BORDERS OF FIBRE REINFORCED COMPOSITE PLATES BY INTEGRAL EQUATIONS

Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.     

Computational simulation of deformation behavior of 2D-lattice continuum

Finite element methods for an elastic Cosserat continuum obeying micropolar theory and couple stress theory are developed and applied to the simulation of stress concentration around a circular hole in a lattice continuum plate, in which the lattice continuum is the continuum model for materials with lattice-like microstructure. In the formulation of the finite element method based on couple stress theory, a new method consisting of a kind of selective reduced integration is proposed to remedy the over-constraint problem which arises in the penalty method of constraining the micro- and macrorotation vectors. The proposed finite element methods are validated by comparing the numerical solutions of stress concentration around a circular hole in a uniform tension field to the exact solutions for the isotropic materials obeying both micropolar theory and couple stress theory. Subsequently, the proposed method is applied to the lattice continuum, which is a continuous model of discrete lattice structure obeying couple stress theory such as cancellous bone with trabecular architecture, to analyze the dependence of the stress concentration factor on the microstructural parameters. In the range where the dimensions of the structural parameters are comparable to the hole radius, the stress concentration factor rises when the principal direction of the lattice structure is aligned along the tensile direction, whereas it falls when these directions form an oblique angle. The proposed finite element methods are applicable in investigation of the deformation behavior of materials with microstructures.     

纳米尺度孔边裂纹裂尖Ⅲ型应力强度因子研究

研究了纳米尺度圆孔孔边裂纹在远场反平面剪切载荷作用下的断裂性能。基于Gurtin-Murdoch表面弹性理论和保角映射技术,利用复变弹性理论获得了该类非均匀材料应力场的解析解,给出了裂尖Ⅲ型应力强度因子的闭合解。基于所得解答,研究了孔边的应力场分布规律,讨论了裂尖应力强度因子的尺寸依赖效应以及圆孔相对尺寸对应力强度因子的影响。研究结果表明：孔边应力场呈现非单调分布,表面效应对孔边不同位置应力的影响程度不同;当圆孔裂纹的尺寸在纳米量级时,裂尖应力强度因子具有显著的尺寸依赖效应;圆孔相对裂纹尺寸对裂尖应力强度因子的影响规律受表面性能的制约,同时表面性能对应力强度因子的影响也取决于圆孔的相对尺寸。     

The finite expansion of a circular hole in an infinite plate: A dynamic solution

The problem of dynamic expansion of a finite circular hole in an infinite plate, of uniform initial thickness, in a state of plane stress is worked out by solving the equation of motion. A numerical solution is obtained for a strain-hardening material using (i) a continuous three-parameter stress-strain relation and (ii) Nadai's J₂-deformation theory of plasticity. The solution is obtained by the method of characteristics for both ramp velocity and ramp pressure prescribed at the hole boundary.     

复合材料开孔薄板受力有限元分析

对复合材料开孔层合板应力集中情况进行了深入探讨,给出理论上分析计算复合材料开孔应力集中的一般方法,得出了影响应力集中问题的主要因素.并通过有限元分析软件NASTRAN对一典型开孔复合材料层合板进行有限元分析,得出开孔复合材料板应力集中较金属材料严重的结论,具有一定的工程指导意义.     

复合材料杆梁有限元模拟方法研究

为了能够用匀质各向同性材料杆梁理论来解决非匀质复合材料杆梁的计算问题,文中从复合材料单向层压板材料常数的基本理论出发,论述了用有限元法模拟复合材料杆梁结构的理论和方法,包括如何确定复合材料杆梁的材料常数、抗弯刚度、轴惯矩、中性轴和截面应力等,并通过算例验证了所述理论和方法的正确性。该理论和方法对解决工程实际问题具有重要的参考价值。