基于界面端奇异性理论的单纤维拔出试验的试件设计

在单纤维拔出试验中，由于试件的界面端存在应力奇异性，这使试验所得到的界面剪切强度数据失去合理性[1]。但从文献[1]关于微珠脱粘试验研究的结论中可以发现当基体的楔形角小于某临界角度后，微珠试件界面端应力奇异性几乎消失。由此启发我们设计出一种楔形角小于该纤维／基体系统临界角的锥面的拔出试件，这样即可以防止出现传统拔出试件在界面端的强应力奇异性，又可以避免微珠脱粘试验自身的缺陷。界面端具有任意楔形角的轴对称模型被用于分析和确定纤维／基体系统的临界角，对方程进行渐近展开和分离变量处理，根据边界条件可以得到关于特征值λ的特征方程，针对确定的纤维／基体系统可以得到特征值和楔形角的关系曲线，我们把应力奇异性指数等于-0．005时所对应的楔形角定义为临界角，以及根据临界角设计锥面拔出试件的方法。     

Long-term strength of metals and creep equations based on the Coulomb-Mohr criterion

It is proposed to construct long-term strength and creep relations for metals on the basis of the Coulomb-Mohr criterion. The creep equations and the long-term strength criterion for plane stress are analyzed in detail. Results of long-term strength calculations are compared with data of experiments with metallic materials. It is established that theoretical and experimental results are in satisfactory agreement. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 115–123, November–December, 2007.     

A PREDICTIVE APPROACH TO THE IN-PLANE MECHANICAL PROPERTIES OF STITCHED COMPOSITE LAMINATES

This contribution attempts to model the alteration of the in-plane elastic properties in laminates caused by stitching,and to predict the in-plane effective tensile strength of the stitched composite laminates.The distortion of in-plane fibers is considered to be the main cause that affects the in-plane mechanical properties.A fiber distortion model is proposed to characterize the fiber misalignment and the fiber content concentration due to stitching.The undistorted region,the fiber distortion region,the resin-rich pocket and the through-thickness reinforcement section are taken into account.The fiber misalignment and inhomogeneous fiber content due to stitching have been formulated by introducing two parameters,the distortion width and maximum misalignment.It has been found that the ply stress concentration in stitched laminates is influenced by the two concurrent factors,the stitch hole and inhomogeneous fiber content.The stitch hole brings about the stress concentration whereas the higher fiber content at the local region induced by stitching restrains the local deformation of the composite.The model is used to predict the tensile strength of the [0/45/0/-45/90/45/0/-45]_(2s) T300/QY9512 composite laminate stitched by Kevlar 29 yarn with different stitching configurations,showing an acceptable agreement with experimental data.     

Modeling the effect of diffusion of the ambient medium on the long-term strength of a hollow cylinder under uniaxial tension

The problem of the long-term strength of an extended thick-walled tube containing a corrosive medium in the internal cavity is solved. The diffusion of this medium into the tube material is analyzed. The diffusion equation is solved approximately by introducing the diffusion front, and the error of the solution is estimated. The dependence of the time of fracture of the tube on the variable tensile stress and the concentration of the medium filling the cavity is obtained. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 4, pp. 88–93, July–August, 2007.     

纤维树脂界面剪切强度及纤维强度分布参数的实验测定

界面剪切强度及纤维强度分布参数是复合材料设计及应用研究中的重要参数，本文采用单纤维段埋入法测定了上述两个参数。通过实验研究说明了单纤维段埋入法是一种测定界面剪切强度及纤维强度分布参数的有效的实验方法；同时证实了基体的力学性能对界面剪切强度有着重要的影响。全部实验在自制的实验系统上完成     

用试验室尺寸的试样预测混凝土及岩石结构的准脆性断裂

0Introduction Thefracturepropertiesofconcreteandrockmaterials,suchasfracturetoughnessKICand strengthfthavebeenofgreatinterestsformanyyearsbecauseoftheirimportantroleincontrolling thestructuralintegrityofvariousengineeringstructures[1-27].Varioustestingtec…     

拉压性能不同材料的几种结构的极限分析

给出了拉压性能不同材料（简称具有Ｓ－Ｄ效应的材料）的几种结构的极限载荷公式。揭示出材料的拉压性能不同对几种结构承载能力的影响规律。所给出的极限载荷公式可供工程设计人员参考。     

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基于27种合金钢与铝合金的机械、力学性能，分析对比了3种理论估算疲劳极限方法的估 算结果，发现3种方法中只有两种方法能够比较精确地估算材料的疲劳极限; 当引 入强度系数和应变硬化指数与常规机械与力学性能的关系之后，这两种方法都可借助材料的 常规机械与力学性能估算疲劳极限，估算过程中的限制性条件``高强度钢'应予取消.     

树枝状界面相开裂对纤维强度的影响

碳纤维增强铝的复合材料在制造过程中，由于发生化学反应而在界面上形成新相。该相并非均匀附着在纤维表面，而是以纤维为主杆形成树枝状。本文利用剪切滞后理论，同时考虑到界面相亦有承受轴向外载的能力，分析了界面相开裂对纤维强度的影响。结果表明界面相与纤维间界面强度以及该界面脱粘后的摩擦应力的增加都能使纤维在给定外载下破坏的概率减小；另外界面相的厚度、沿纤维方向的弹性模量、剪切模量的增加却使上述概率增加。     

改性膨胀土路堤填筑含水量优化试验研究

在控制含水量的前提下,对分别掺入不同量石灰、不同量水泥改性膨胀土试件进行强度和膨胀量试验,得到不同含 水量及不同石灰(水泥)掺量对改性膨胀土强度和膨胀性的影响,通过对实验所得数据的分析,找出含水量和掺石灰(水泥)剂 量的最佳融合点,并据此对膨胀土路堤填料的改性施工提出了一些有益的建议。