胶补加筋板应力强度因子及胶层剪应力计算

 在铆钉力法的基础上，提出计算胶接修补加筋板结构应力强度因子及胶层剪应力的解析法, 对分析胶接修补的加筋板强度具有现实意义. 利用影响系数，可以得到筋条、补片及蒙皮位 移的表达式，根据位移协调条件，建立联立方程，从而得到胶层剪应力及铆钉力. 通过解析 式，计算裂纹尖端的应力强度因子，分析补片对结构修补的效果，综合考虑了筋条及补片对 应力强度因子的影响.     

胶补加筋板应力强度因子及胶层剪应力计算

在铆钉力法的基础上，提出计算胶接修补加筋板结构应力强度因子及胶层剪应力的解析法，对分析胶接修补的加筋板强度具有现实意义．利用影响系数，可以得到筋条、补片及蒙皮位移的表达式，根据位移协调条件，建立联立方程，从而得到胶层剪应力及铆钉力．通过解析式，计算裂纹尖端的应力强度因子，分析补片对结构修补的效果，综合考虑了筋条及补片对应力强度因子的影响．     

金属损伤复合材料胶接修补结构力学试验研究

为评估金属损伤复合材料胶接修补结构的剩余强度和剩余寿命,进行了含腐蚀和疲劳损伤LY12CZ航空铝合金板碳/环氧复合材料补片胶接修复结构的力学性能试验,分析了在静拉伸和疲劳载荷作用下修补结构的破坏模式、失效机理。试验研究发现:复合材料胶接修补技术有效改善了腐蚀和疲劳损伤这两类损伤区域的受力状况,恢复了其载荷传递路线,其静拉伸失效形式为金属韧性断裂后胶层脱粘的分步渐进式破坏;与含损伤未修补试样相比,胶接修补大幅度提高了试件的剩余强度和剩余寿命恢复率,修补后铝合金试件承载能力增加了约25%,疲劳寿命增加至修补前的约4倍~5倍。     

腐蚀环境下复合材料修补件力学特性研究

采用复合材料补片胶接修补含裂纹LY12CZ铝合金板,开展了试验室大气环境和加速预腐蚀环境下复合材料修补件静强度拉伸和疲劳裂纹扩展对比试验研究.结果表明,复合材料补片均能显著提高损伤结构的拉伸强度和疲劳寿命,且短周期的预腐蚀环境对修补件两种力学特性的影响可以忽略不计.同时,基于Paris公式和Rose分析模型,建立了常规环境和预腐蚀环境下疲劳裂纹扩展寿命预测模型,通过与试验结果的对比证明了该模型的工程有效性.     

含裂纹金属薄板胶接补强的应力分析

本文应用弹塑性有限元分析胶接补强的含裂纹薄板结构,剪切单元被改进使之可连结平面等参单元并用于分析胶层应力。计算了补强后裂纹板的应力强度因子,并将计算结果与实验数据作了比较,分析表明,胶接补强可显著降低裂尖的应力集中,使裂纹板内应力分布趋于均匀。     

含裂纹金属薄板胶接补强的应力分析

本文应用弹塑性有限元分析胶接补强的含裂纹薄板结构,剪切单元被改进使之可连结平面等参单元并用于分析胶层应力。计算了补强后裂纹板的应力强度因子,并将计算结果与实验数据作了比较,分析表明,胶接补强可显著降低裂尖的应力集中,使裂纹板内应力分布趋于均匀。     

含广布腐蚀坑结构寿命评估方法

为了定量评估含广布腐蚀损伤老龄化飞机结构的剩余强度, 采用等效裂纹方法将腐蚀坑沿垂 直于外界最大主应力方向进行投影处理, 使其转化为具有相同寿命的等效初始表面裂纹, 然 后采用参数化有限元方法,求解等效裂纹前沿的应力强度因子、裂纹扩展方向和裂纹扩展增量, 建立并应用应力强度因子变化历程, 采用循环接循环的损伤累积方法对含广布等效表面裂纹 在疲劳载荷作用下的寿命进行了预测. 预测结果为复杂环境中含广布腐蚀坑的飞机结构寿命 预测提供了参考.     

复合材料胶接修补问题的试验研究和分析

用带中心裂纹的Ｌｙ１２ＣＺ铝合金板模拟飞机的损伤结构,对于不同的修补方式（单边和双边修补）,不同的补片材料（铝合金和复合材料）和几何尺寸以及脱胶等因素,进行了静强度和疲劳裂纹扩展试验． 实验表明． 胶结修补能明显地提高损伤结构的强度和疲劳寿命,同时实验还为修补实践的选材和几何参数的设计等提供了大量数据． 文中最后给出了修补结构疲劳裂纹的有限元计算估计,并与试验结果进行了比较和分析．     

复合材料的Ⅲ型动态断裂力学分析

本文综合利用 Laplace 变换和 Fourier 变换,从理论上分析了含有贯穿裂纹的层合复合材料在动载荷作用下裂纹尖端的Ⅲ型动态应力强度因子.并以冲击载荷为算例,考查了外层的厚度、拉、剪模量的变化对裂纹尖端应力强度因子的影响,为改善复合材料的断裂动力学性能提供了参考依据.     

复合材料胶接结构有限元分析方法研究进展

胶接结构的强度分析方法可以分为解析法和数值法两类,数值法主要是有限元方法.本文综述了复合材料胶接结构的有限元分析方法,按照胶接结构有限元模型建立的物理机理,将胶接结构力学分析模型分为基于有限元应力分析模型、基于断裂力学模型和基于损伤力学模型3类.详细介绍了这3类模型中的主要有限元建模分析方法:三维应力分析方法、虚拟裂纹闭合技术方法和内聚力模型方法,介绍了每种方法的基本思想、适用范围、优缺点、改进和扩展、有限元建模的实施步骤,以及有限元分析中应用该方法所取得的成果.第五部分从适用范围、应力奇异和破坏判据3个方面对这几种分析模型进行了对比分析.最后,对该领域发展趋势进行了展望.      

Fatigue crack growth analysis of adhesively repaired panel using perfectly and imperfectly composite patches

Fatigue crack behavior of cracked aluminum panel repaired with the imperfectly bonded composite patch is analyzed. The imperfection is in the form of debond which could result during the bonding of patch or the service life of the repaired structure. Debonds, of various sizes and at different locations with respect to the crack front, are investigated. An analytical procedure, involving two-dimensional finite element method having three layers to model cracked plate, adhesive and composite patch, is used to compute the stress intensity factors of test coupons. From the computed stress intensity factors, the crack growth rates are obtained analytically by assuming that the relationship between the stress intensity factor and the crack growth rate after repair is the same as the fatigue crack growth relationship for cracked panel material. The fatigue crack growth rates obtained experimentally and analytically are in good agreement with each other and they vary linearly with crack length inside the patch. The experimental results are bounded between its analytical counterparts at the mid-plane and free edge surfaces of the cracked panel. The present analytical procedure can, thus, be used to characterize the effects of imperfectly and perfectly bonded composite patch repairs on the durability and damage tolerance of the repaired structure.     

INVESTIGATION OF THE DYNAMIC BEHAVIOR OF TWO COLLINEAR ANTI-PLANE SHEAR CRACKS IN A PIEZOELECTRIC LAYER BONDED TO TWO HALF SPACES BY A NEW METOHD

IntroductionItiswell_knownthatpiezoelectricmaterialsproduceanelectricfieldwhendeformedandundergodeformationwhensubjectedtoanelectricfield .Thecouplingnatureofpiezoelectricmaterialshasattractedwideapplicationsinelectro_mechanicalandelectricdevices,suchaselectro_mechanicalactuators,sensorsandstructures.Whensubjectedtomechanicalandelectricalloadsinservice,thesepiezoelectricmaterialscanfailprematurelyduetodefects,e .g .,cracks,holds,etc.arisingduringtheirmanufactureprocess.Therefore,itisofgreatimp…     

DYNAMIC STRESS INTENSITY FACTORS AROUND TWO CRACKS NEAR AN INTERFACE OF TWO DISSIMILAR ELASTIC HALF－PLANES UNDER IN－PLANE SHEAR IMPACT LOAD

ＤＹＮＡＭＩＣＳＴＲＥＳＳＩＮＴＥＮＳＩＴＹＦＡＣＴＯＲＳＡＲＯＵＮＤＴＷＯＣＲＡＣＫＳＮＥＡＲＡＮＩＮＴＥＲＦＡＣＥＯＦＴＷＯＤＩＳＳＩＭＩＬＡＲＥＬＡＳＴＩＣＨＡＬＦ－ＰＬＡＮＥＳＵＮＤＥＲＩＮ－ＰＬＡＮＥＳＨＥＡＲＩＭＰＡＣＴＬＯＡＤＱｉａｎＲ...     

复合材料承受剪切时双裂纹周围的应力强度因子

本文研究了由各向同性和各向异性半无限接合而成的复合材料中的应力强度因子问题，在复合材料的接合面附近处具有与接合面平行且共线的两个Ｇｒｉｆｆｉｔｈ裂纹，裂纹面上作用有剪应力，本文利用付利叶变换将混合边值问题归毕为求解奇异积分方程问题，为求解这些方程，将裂纹面上，下的位移差展成级数，并满足理解纹面外侧边界条件，级数中的待定系数利用裂纹面内的边界条件和施密特方法求得，本文对硼纤维塑料和铝板接合的复合材料     

用三维有限元模型计算复合材料粘接修补裂纹板的J积分

用复合材料单边粘接修补带裂纹金属板是三维应力问题,而采用简化的二维有限元分析模型计算则有一定近似性。本文建立了三维有限元模型,并计算了其断裂参数J积分。计算分析结果表明,厚度方向上J积分值是变化的,并且修补边比未修补边的J积分值有明显减小;修补前后裂纹面的张开位移明显不同;裂纹板模型的J积分值与裂纹长度在修补前为二次关系,修补后,变成线性关系;粘胶和补片的厚度、粘胶的模量对J积分的影响比较显著。为了提高修补性能,需要对粘胶和补片的几何尺寸和材料性能进行优化。     

Dynamic behavior of two collinear interface cracks between two dissimilar functionally graded piezoelectric/piezomagnetic material strips

The dynamic interaction of two collinear interface cracks between two dissimilar functionally graded piezoelectric/piezomagnetic material strips subjected to the anti-plane shear harmonic stress waves was investigated. By using the Fourier transform, the problem can be solved with the help of a pair of triple integral equations in which the unknown variable is jump of displacement across the crack surfaces. These equations are solved using the Schmidt method. Numerical examples are provided to show the effect of the functionally graded parameter, the circular frequency of the incident waves and the thickness of the strip upon stress, electric displacement and magnetic flux intensity factors of cracks.     

正交各向异性功能梯度涂层-基底结构共线裂纹问题的断裂分析

论文研究了一正交各向异性功能梯涂层粘结到一均匀基底含共线裂纹的平面I型断裂问题.引入新的双参数指数函数模拟连续改变的材料性质,正交各向异性的主轴方向分别为平行和垂直于带的边界,采用积分变换技术,所求的问题转化为第一类的Cauchy奇异积分方程,获得了共线裂纹尖端应力场,结果显示了材料常数和几何参数对应力强度因子的影响.     

The stress intensity factors near the tips of two collinear cracks in composite under in-plane shear

In this paper, the stress-intensity factors for two collinear cracks in a composite bonded by an isotropic and an anisotropic half-plane were calculated. The cracks are paralell to the interface, and the crack surfaces are loaded by uniform shear stresses. By using Fourier transform, the mixed boundary value problem is reduced to a set of singular integral equations. For solving the integral equations, the crack surface displacements are expanded in triangular series and the unknown coefficients in the series are determined by the Schmidt method. The stress intensity factors for the cracks in the boron-fibre plastics and aluminium joined composite and in carbon-fibre reinforced plastics were calculated numerically.     

DYNAMIC BEHAVIOR OF TWO COLLINEAR PERMEABLE CRACKS IN A PIEZOELECTRIC LAYER BONDED TO TWO HALF SPACES

IntroductionIn the fracture mechanics studies for piezoelectric materials,differently electricboundary conditions at the crack surfaces have been proposed by many researchers.Forexample,for the sake of analytical simplification,the assumption that the cra…     

AN INVESTIGATION ON TWO CRACKS PERPEN DICULAR TO THE INTERFACES IN A PIEZOE LECTRIC LAYER BONDED TO TWO HALF SPACES BY THE SCHMIDT METHOD

The behavior of two collinear anti-plane shear cracks in a piezoelectric layer bonded to two half spaces is investigated by the Schmidt method. The cracks are vertically to the imerfaces of the piezoelectric layer. By using the Fourier transform, the problem can be solved with two pairs of triple integral equations. These equations are solved using the Schmidt method. This process is quite different from that adopted previously. Numerical examples are provided to show the effect of the geometry of the interacting cracks and the piezoelectric constants of the material upon the stress intensity factor of the cracks.