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.     

含多源损伤的胶接修补结构有限元分析方法

采用有限元法研究含多源损伤结构的胶接修补问题,利用二维三层有限元模型对损伤区进行了数值模拟,并选取典型多源损伤情况中含共线双裂纹铝板结构为算例,详细分析了含多裂纹胶接修补结构中两裂纹相对位置、补片尺寸、铺层和厚度对应力强度因子的影响.结果表明,复合材料胶接修补可明显降低含共线双裂纹母板的应力强度因子;对于确定的裂纹和应力场,应对复合材料补片长度和厚度等参数进行优化设计,以获得最佳的修补效果.     

单搭拉剪胶焊接头的应力和刚度分析

胶焊复合连接技术兼具胶接和点焊的优点,它因提高结构强度和刚度而使车辆轻量化成为可能.以胶接理论为基础,考虑了被粘体剪切应变,将焊点视为大剪切弹性模量胶粘剂,胶层和焊点沿其厚度方向的剪应力不变,建立了胶焊单搭拉剪接头的线弹性应力解析模型.在应力模型基础上,将接头各组成部分看作是独立承载的拉伸和剪切弹簧单元,得到了其刚度解析模型.应力模型中的正应力和剪应力与有限元解吻合得较好,证明理论模型正确,参数研究中确定了影响胶焊单搭接头应力分布特征的关键耦合参数.     

含裂粘补结构胶层剪应力的计算

提出了一种计算含裂粘补结构胶层剪应力的新方法。采用有限元计算补片的影响系数，使用已有解析解计算蒙皮的影响系数。利用位移协调条件，列出有限多组联立方程。解出含裂粘补结构胶层剪应力。计算结果较好的反映了含裂粘补结构胶层剪应力的实际变化趋势，该方法同样可应用于其他结构如高梯度基膜复合材料剪应力的计算。     

含界面裂纹的不可压缩双金属胶接件的解析变分－守恒积分解法

本文根据平面问题的复变函数理论推导了含界面裂纹双金属胶接件满足微分方程、开裂界面边界条件与未开裂界面连续条件的应力与位移本征函数展开式，并建立了不可压缩双金属界面裂纹的复合型守恒积分及其与应力强度因子之关系，进而利用分区广义变分原理满足其余边界条件确定包含应力强度因子在内的展开式系数，得到守恒积分并求出应力强度因子．数值计算表明，沿不同回路的在恒积分具有很好的守恒性而且由这两种方法所得应力强度因子具有很好的一致性．     

单搭接胶接接头弹性应力的二维分析方法

提出一种能得到单搭接胶接接头二维弹性应力解析解的的一般分析方法.该方法从纵向正应力沿厚度线性分布的理论假设出发,用完整的几何方程与本构方程,在考虑了被粘物与胶层的剪应力和剥离正应力沿厚度的变化,而且严格满足包括搭接区端头胶层剪应力为零的所有边界条件下,能够准确地预测接头任意点的应力状态,并适用于被粘物/胶层几何和材料属性的任何组合.通过与以往的解析解和有限元分析结果对比表明:不仅胶层平均剪应力最大值发生在距胶层端头很近的位置处,而且平均剥离正应力最大值位置也距离接头端头很近.这与以往绝大多数理论解预测"胶层剪应力和剥离正应力最大值都发生在端头处"的结论不同;该解析解有很好的精度和较广的适用范围.     

含界面裂纹的不可压缩双金属胶接件的解析变分－守恒积分解法

本文根据平面问题的复变函数理论推导了含界面裂纹双金属胶接件满足微分方程、开裂界面边界条件与未开裂界面连续条件的应力与位移本征函数展开式，并建立了不可压缩双金属界面裂纹的复合型守恒积分及其与应力强度因子之关系，进而利用分区广义变分原理满足其余边界条件确定包含应力强度因子在内的展开式系数，得到守恒积分并求出应力强度因子．数值计算表明，沿不同回路的在恒积分具有很好的守恒性而且由这两种方法所得应力强度因子具有很好的一致性．     

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。     

复合材料补片加固钢板的粘接应力与失效模拟

在ANSYS有限元软件中建立三维有限元模型,对复合材料补片单面加固钢板进行数值模拟,使用内聚力单元模拟胶层脱粘和扩展过程,有限元模型计算结果与试验结果吻合较好,弹性极限载荷和失效载荷的相对误差分别为9.6%和4.2%。计算得到了模型在拉伸载荷作用下的载荷-位移曲线、胶层剪应力和剥离应力分布情况以及补片x轴向应力分布情况。结果表明,胶层端部最先达到极限强度后出现开裂,脱粘从补片两端开始逐渐向中心扩展,且扩展过程是非对称的;当补片发生部分脱粘后,补片应力集中在未脱粘处,承载长度逐渐减小、承载能力逐渐降低。     

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。     

Linear coupled bending and extension of an unbalanced bonded repair

An unbalanced repair is a composite patch bonded to one side of a cracked structure for the purpose of preventing or reducing damage growth in the substrate. A single-sided repair offsets the load path within the structure, inducing out-of-plane bending. This bending increases the stress intensity in the underlying crack and causes adhesive peel stresses and bending of the repair which can, relative to a repair that is restrained against bending, lead to early failure. In this article the authors correct the analysis of Wang and Rose [Wang, C.H., Rose, L.R.F., 1997. On the design of bonded patches for one-sided repair. In: Proceedings of the 11th International Conference on Composite materials, Gold Coast, Australia, vol. 5, pp. 347–356] developed by using an energy analysis of a single-sided or unbalanced repair applied to a very long-crack, to comply with Maxwell’s reciprocal theorem and to account for transverse normal and shear stresses at the crack tip and the accompanying shear deflections. The authors then develop closed-form equations useful for bonded composite repair design and damage tolerance assessment of cracks of arbitrary length by developing a new method for interpolation between this long-crack limit and a short-crack limit based on the stress intensity and crack face displacements for an unreinforced crack. The interpolation method is then tested against an advanced line-spring model that has been created by using a 6th order generalized plane strain plate formulation in extension and a new 8th order formulation in bending, thus allowing for the inclusion of transverse shear and normal stresses. The closed-form equations are found to be accurate when compared to the line-spring model, and to provide reasonable results when compared to a three-dimensional finite element model of a bonded repair. Inaccuracies are shown to exist principally in the determination of the nominal stresses in the vicinity of the crack.     

含裂纹铆接加筋板抗破损能力的优化设计

以非对称含裂纹铆接加筋板裂尖应力强度因子解析解为基础,考虑到加筋桁条的位置、尺寸对裂尖应力强度因子的影响,应用最大应力强度因子最小化的方法建立了含裂纹铆接加筋板的数学模型,用虚拟目标函数法对模型进行转化并用基于BFGS法的外罚函数法求解此问题,获得最小应力强度因子意义下的最优结构构型参数,从而使含裂纹铆接加筋板获得最佳的抗破损能力。算例验证了本文方法的有效性和正确性。     

A three-parameter elastic foundation model for interface stresses in curved beams externally strengthened by a thin FRP plate

Externally bonding of fiber reinforced polymer (FRP) plates or sheets has become a popular method for strengthening reinforced concrete structures. Stresses along the FRP–concrete interface are of great importance to the effectiveness of this type of strengthening because high stress concentration along the FRP–concrete interface can lead to the FRP debonding from the concrete beam. In this study, we develop an analytical solution of interface stresses in a curved structural beam bonded with a thin plate. A novel three-parameter elastic foundation model is used to describe the behavior of the adhesive layer. This adhesive layer model is an extension of the two-parameter elastic foundation commonly used in existing studies. It assumes that the shear stress in the adhesive layer is constant through the thickness, and the interface normal stresses along two concrete/adhesive and adhesive/FRP interfaces are different. Closed-form solutions are obtained for these two interfacial normal stresses, shear stress within the adhesive layer, and beam forces. The validation of these solutions is confirmed by finite element analysis.     

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.     

Balanced and unbalanced patching of cracked lap joints using weighted adhesive plate element

First order shear deformation theory is applied to analyze the behavior of one-side (unbalanced) and two-side (balanced) patched lap joints containing initial through cracks. The joints are made of adherends bonded together by adhesives. An adhesive interface plate element is introduced; it consists of an adhesive layer weighted by influence of the adherend. The thin adhesive layer is assumed to behave elastically and modelled as a simple tension-shear spring. The mathematical model contains layers of adherend and weighted adhesive layer.Finite elements are employed to model the adherend with an 8-node isoparametric plate element and interface layer with a 16-node plate element. Numerical results are obtained for one-side and two-side patches the width of which could be narrower or wider than the crack length. The former leads to bulging and possible peeling while the latter provides better bonding. Stresses and crack-tip stress intensity factors are calculated for different patch thickness. Effectiveness of the weighted adhesive layer model is exhibited by comparing the present results with those found in previous work where the adhesive is modelled as an individual layer.     

膜-基复合材料界面剪应力的三维半解析计算

 采用影响系数法对膜-基复合材料的界面剪应力三维半解析进行 了分析研究.利用三维有限元方法对薄膜的影响系数进行了计算. 将 基体作为半无限大体，利用其平面边界作用单位力时的位移场解析 解，得到基体的影响系数. 结果表明，对膜-基复合材料界面剪应力 进行三维半解析计算，克服了完全用三维有限元对其进行计算的限 制，为该类问题的分析提供了新的途径.     

5级人防口部粘钢封堵接头抗爆实验研究

通过粘钢实现一典型汽车库人防口部封堵的设计方案,并对原设计方案进行相似设计后,对粘钢接头结构实验模型在核爆炸压力模拟器中进行模爆实验,得到沿竖向支座钢板的位移和应变时程曲线,并和有限元数值解进行了对比,其结果均较吻合,通过沿竖向支座钢板的应变分布规律得到钢板-混凝土界面之间的粘结应力;检验了在5级人防爆炸冲击波作用下,混凝土墙与钢板间粘结面承载力的可靠性;分析了5级人防爆炸荷载作用下支座钢板沿竖向应力的分布规律,为确定混凝土墙与钢板之间粘结应力的计算方法提供了参考。     

FRP加固梁的FRP-混凝土界面脱胶分析

为了研究纤维增强聚合物(fiber reinforced polymer, FRP) 加固梁的FRP-混凝土界面脱胶破坏过程,本文将混凝土梁和FRP 板均视为线弹性的欧拉-伯努利梁(Euler-Bernoulli beams), 且两者通过粘结层胶结在一起. 对于FRP-混凝土结构,有两种形式的脱胶破坏：板端脱胶破坏和跨中裂缝导致的脱胶破坏.对于FRP-混凝土梁,利用合理的粘结模型按第2 种脱胶失效形式,详细讨论了FRP-混凝土界面的脱胶过程,得到了不同阶段的胶结滑移、界面剪应力和FRP 轴向力的解析解. 实验研究验证了理论分析的结果,参数研究进一步探讨了胶结长度和粘结层厚度对于FRP-混凝土界面脱胶行为的影响.     

Analytical solution for a strained reinforcement layer bonded to lip-shaped crack under remote mode Ⅲ uniform load and concentrated load

In this paper,the analytical solution of stress field for a strained reinforcement layer bonded to a lip-shaped crack under a remote mode Ⅲ uniform load and a concentrated load is obtained explicitly in the series form by using the technical of conformal mapping and the method of analytic continuation.The effects of material combinations,bond of interface and geometric configurations on interfacial stresses generated by eigenstrain,remote load and concentrated load are studied.The results show that the stress concentration and interfacial stresses can be reduced by rational material combinations and geometric configurations designs for different load forms.     

Analytical solution for a strained reinforcement layer bonded to lip-shaped crack under remote mode III uniform load and concentrated load

In this paper, the analytical solution of stress field for a strained reinforcement layer bonded to a lip-shaped crack under a remote mode III uniform load and a concentrated load is obtained explicitly in the series form by using the technical of conformal mapping and the method of analytic continuation. The effects of material combinations, bond of interface and geometric configurations on interfaciai stresses generated by eigenstrain, remote load and concentrated load are studied. The results show that the stress concentration and interfaciai stresses can be reduced by rational material combinations and geometric configurations designs for different load forms.