含孔复合材料层合板孔边的应力集中

针对含孔有限宽复合材料层合板的应力集中问题,提出一种计算孔边应力分布及应力集中因子的方法：先利用经典层板理论,将复合材料层合板化归为各向异性板;再将各向异性板等效转换为一偏轴拉伸的单向纤维层板;最后利用含孔偏轴单向板的孔边应力计算公式来分析一般铺层层合板孔边应力集中情况。根据所推导的计算公式,分析讨论了板宽/孔径比、铺层比例、铺层方式、材料性能参数等因素对孔边应力集中的影响。     

有限宽度和椭圆孔形状对缺口层合板强度预测的影响

本文采用有限元方法对正交各向异性材料含有不同椭圆孔形状的有限宽度板作了分析,给出了有限宽度和椭圆孔形状对应力集中因子K₁和孔边应力分布σ_y(x,0)的影响公式。数值结果表明:正交各向异性板的有限宽度和椭圆孔形状对K_r和σ_y(x,0)的影响均与各向同性材料不同,所以有限宽度和椭圆孔形状将对缺口层合板强度的预测产生影响。      

不同孔口形状对含孔复合材料板孔边应力状态影响的研究

对复合材料结构而言,孔口边界条件的建立和处理比金属材料要复杂得多。针对含不同孔形的复合材料板,根据非均质各向异性弹性理论和复变函数理论,通过保角映射方法建立精确的边界条件,解决了某些复杂孔形的边值问题。得到了含圆、矩形和六边形孔复合材料板孔边应力的解析解。并针对不同孔形在受外荷载作用的情况下的应力状态,以及它们对孔边应力集中系数的影响进行了探讨。     

不同材料及荷载下含椭圆和圆孔树脂基复合材料板孔边应力场比较

针对实际工程中常见的含圆孔和椭圆孔的树脂基复合材料板,建立基于Mathematica的计算模型,对带有圆形和椭圆孔的复合材料板,在不同荷载作用下进行计算,对两种孔形应力分布作比较。而且以两种不同材料含孔板为例,对不同荷载作用下的孔边应力进行计算,并对材料对孔边应力场的影响作较为全面的比较。为在实际工程中对孔形、材料以及所受外荷载进行合理选择提供理论依据。     

基于点应力破坏准则的含圆孔树脂基正交各向异性板的强度计算

对于实际工程中常见的含孔结构,建立利用保角映射原理对含圆孔树脂基复合材料板的孔边应力进行准确分析的方法,采用所给出的方法可以得到孔边在板边外荷载作用下的应力分布,然后采用点应力破坏准则对板进行全面的强度校核。文中不仅对带有圆形孔的复合材料板,在拉应力作用情况下的孔边应力场进行了计算,而且对外荷载、孔口尺寸、某点距孔边的距离以及材料性质等因素对应力的影响进行了较为全面的仿真分析。     

含椭圆孔压电材料的电弹场

采用复变函数的方法,研究了含椭圆孔的压电材料在无限远处受力电荷载作用的平面问题。与已有文献不同,通过求解10元一次方程,得到了满足可导通和不可导通电边界条件,孔内和压电材料体内电弹场的通解。以PZT一4压电陶瓷为例,给出了孔内的电场、压电材料体内电弹场沿孔边和坐标轴向的分布情况。得出了以下新的结论:含椭圆孔压电材料的电弹场与边界条件、力电荷载的方向、椭圆孔的形状有关,但在水平方向的拉伸载荷和电位移的作用下,椭圆孔的形状对长半轴处的环向电位移和正应力的最大值没有影响。     

不同荷载作用下各向异性度对树脂基正交各向异性圆孔板孔边应力分布的影响

含孔结构在机械结构、装备中随处可见。针对含圆孔的树脂基复合材料板,采用解析法对几种常见荷载对孔边应力场的影响进行分析。对两个主方向的杨氏模量的变化对孔边应力的影响进行仿真分析,并对在不同荷载作用下,各向异性度对孔边应力场的影响进行比较。通过计算可知,随着杨氏模量的增大,孔边应力也增大,且随杨氏模量E1增大所引起的孔边应...     

四点支承单层开孔玻璃承载性能的有限差分法分析

基于小挠度薄板的近似理论,采用有限差分法分析了4 点支承带孔玻璃板位移和应力的分布规律,并通过对点支承处进行特殊处理,建立了奇点模型,同时提供了孔边应力的计算公式。该计算模型描绘了点支玻璃板中应力分布的特点,直观、理论性强且操作简便,且计算结果与现行规程、有限元计算的结果较好的吻合。孔边应力的计算方法可为规程的补充提供必要理论依据。     

小孔法测量正交各向异性材料残余应力

讨论了小孔法测量正交各向异性材料残余应力。以正交各向异性无限大板孔边应力场解析解为基础, 导出了释放应变矩阵计算表达式, 并用一个算例验证了该计算式的正确性。      

集中载荷作用下含椭圆夹杂各向异性板的解法

应用复变函数方法研究了含椭圆夹杂各向异性板在集中载荷作用下的解法，首先将复应力函数在椭圆夹杂与板的接触边界上展开成幂级数，然后代入问题的边界条件，最后得到了幂级数形式的复应力函数的系数的线性方程组，进一步求解可获得板的应力分布。     

Mixed mode fatigue growth of curved cracks emanating from fastener holes in aircraft lap joints

The finite element alternating method is extended further for analyzing multiple arbitrarily curved cracks in an isotropic plate under plane stress loading. The required analytical solution for an arbitrarily curved crack in an infinite isotropic plate is obtained by solving the integral equations formulated by Cheung and Chen (1987a, b). With the proposed method several example problems are solved in order to check the accuracy and efficiency of the method. Curved cracks emanating from loaded fastener holes, due to mixed mode fatigue crack growth, are also analyzed. Uniform far field plane stress loading on the plate and sinusoidally distributed pin loading on the fastener hole periphery are assumed to be applied. Small cracks emanating from fastener holes are assumed as initial cracks, and the subsequent fatigue crack growth behavior is examined until long arbitrarily curved cracks are formed near the fastener holes under mixed mode loading conditions.     

Stress concentrations in a plate with two unequal circular holes

This paper contains an exact solution for stresses which are produced in an infinite plate with two unequal circular holes by a uniform tension, an internal pressure or uniform shearing forces along a hole. Bipolar coordinates are used in the solution. Expressions of the hoop stress at the edges of holes are explicitly derived and the stress concentration factors are calculated. The stresses in an infinite plate with two contacted unequal circular holes are also discussed.     

含有任意多个椭圆孔复合材料层合板的应力场计算

本文应用各向异性弹性力学的复变函数理论,用多保角变换的方法,导出了含有任意多个任意位置椭圆孔的各向异性复合材料板的多复变量应力函数表达式,然后在单位圆周上进行复Fourier级数展开,用待定系数法确定应力函数的未知系数,从而计算弹性板的应力场.编制了相应的多工况运行的FORTRAN77标准化程序,进行了考题和算例分析,给出了级数的收敛状况和孔边周向应力的分布图.      

Numerical limit analysis of perforated plates

Full limit analysis is preseted of a thin plate under plane stress, perforated with circular holes arranged in a regular penetration pattern. The material is assumed to be elastic–perfectly plastic and to obey the Huber–Mises yield condition together with its associated flow law. The finite element tangential stiffness method is employed. Triangular constant-strain elements are used, the load being generated by means of constant edge displacements at the periphery of a suitably selected subregion. Load-displacement diagrams are obtained for various edge displacement programs and then an interaction curve is constructed for the perforated plate considered. Each computational step is associated with a certain plastic zone which develops until the limit state configuration is reached. The plate is provided with equilateral triangular configuration of holes with arbitrary cutout coefficients. The interaction curves are plotted against the Huber–Mises yield condition for the plate without openings.     

A method for stress intensity factor calculation of infinite plate containing multiple hole-edge cracks

Multiple site damage is the occurrence of small fatigue cracks at several sites within aging aircraft structures. Focusing on this typical structure, an analytical method for calculating the stress intensity factor of an infinite plate containing multiple hole-edge cracks was introduced in this paper. The properties of complex variable functions are used to evaluate the stress function. The approximate superposition method is applied to solve stress intensity factor problems on multiple holes. The equivalent crack is introduced to modify the method. Some numerical examples of an infinite plate containing two hole-edge cracks are examined by the method. By comparing the analytical and finite element analysis results it was realized that the analytical results are accurate and reliable. This modified analytical method is easier to apply than some traditional analytical methods and can provide stress intensity factor solutions for an infinite plate containing a random distribution of multiple hole-edge cracks.     

Ultimate state of a plate with several holes

A theoretical method is proposed for determining the ultimate state of a plate with several holes based on strength criteria of fracture mechanics and continuum mechanics. The ultimate state of a plate of finite width with two holes was found by the given method. As a result of realizing the indicated method, methods were developed for determining the stress state of a strip with two holes and the stress intensity factors in a strip with radial cracks extending to the edges of two holes. The maximum difference between the experimental and theoretical data (by the proposed method) does not exceed 12%.Translated from Problemy Prochnosti, No. 3, pp. 44–52, March, 1994.     

Stress concentration of a laminate weakened by multiple holes

A laminate weakened by multiple equal elliptical holes in series is treated as an anisotropic, infinite, multiply connected and thin plate. Using Faber series expansion and a complex potential method in the plane theory of elasticity of an anisotropic body, the general step to deduce the stress concentration in the laminate subjected to arbitrary in-plane loads at infinity is obtained. As a numerical example, the stress concentration of a particular laminate weakened by two, three or four equal circular holes in series is calculated. Moreover, the effects of the loading type, the number of holes and the relative distance between two neighbouring holes on the stress concentration of the laminate are discussed.     

流体流量分布器的设计

根据锐孔理论和两个假定,并应用锐孔流量原理的设计方法,保证通过孔板流量分布器所有锐孔的流体均匀。以小型空分设备分子筛吸附器的孔板分布器为例,通过例题演算,介绍了设计程序。     

姿控飞轮电控系统共模辐射分析与抑制

 为降低飞轮电控系统对其他星载电子设备的电磁干扰,以PWM全桥电路共模辐射源为研究对象,重点分析由开关管和散热片协同导致的共模辐射．建立铝制带鳍散热片计算模型,应用有限元数值计算法分析散热器能量耦合及辐射发射机理,以屏蔽作为主要抑制手段,研究屏蔽板尺寸、放置位置及通风孔对共模辐射抑制效应,并进一步提出屏蔽板改进结构．计算结果表明：使用2块屏蔽板在正确放置时就可有效抑制辐射,且屏蔽板越长,对共模辐射抑制效果越好;屏蔽板上有孔缝存在,对应的辐射就要比无孔时高,开孔个数本身对辐射的影响并不大．改进后的结构对共模辐射抑制效果更优于原结构,尤其体现在3.9 GHz窄频带范围内．     

船体开孔薄板面内剪切屈曲特性研究

船体板材不可避免地存在不同形式的开孔,开孔破坏了结构的连续性,对结构的强度、稳定性具有重要影响,因此研究船体板开孔结构的屈曲特性对保证船舶安全十分重要。在面内载荷作用下,通过画框型剪切夹具、3D全场变形测量-分析系统等对两种不同形式的船体开孔薄板进行剪切屈曲试验,获得了圆形开孔板和方形开孔板的临界屈曲载荷、全场位移/应变信息和拉力-伸长率曲线等;考虑试验夹具的影响,基于Abaqus对不同形式的开孔板进行数值仿真,通过对开孔板进行特征值屈曲分析和非线性屈曲分析,获得了两种不同形式船用开孔薄板的屈曲、后屈曲力学响应信息。通过数值仿真与试验结果的对比研究,验证了数值仿真方法的有效性、准确性。在此基础上,重点剖析载荷-伸长率关系、典型时刻板面全场位移、临界屈曲载荷以及开孔边缘的应力分布响应特征,明确了面积等效情况下圆孔和倒圆角方孔对方形薄板剪切稳定性的影响。为船用薄板面内剪切稳定性的试验和仿真研究以及大型船体结构的设计优化、力学性能评估等提供有益参考。