两级载荷下复合材料层板疲劳与寿命预测

研究了复合材料层板疲劳过程中的累积应变演化规律，建立了以累积应变为基础的非线性积累损伤法则，实验结果表明：文中提出的累积应变方法能够较好地反映加载次序效应，准确地预测了复合材料层板在两级载荷下的疲劳寿命。     

Dynamical behaviors of nonlinear viscoelastic thick plates with damage

Based on the deformation hypothesis of Timoshenko's plates and the Boltzmann's superposition principles for linear viscoelastic materials, the nonlinear equations governing the dynamical behavior of Timoshenko's viscoelastic thick plates with damage are presented. The Galerkin method is applied to simplify the set of equations. The numerical methods in nonlinear dynamics are used to solve the simplified systems. It could be seen that there are plenty of dynamical properties for dynamical systems formed by this kind of viscoelastic thick plate with damage under a transverse harmonic load. The influences of load, geometry and material parameters on the dynamical behavior of the nonlinear system are investigated in detail. At the same time, the effect of damage on the dynamical behavior of plate is also discussed.     

碳纤维悬挂支臂疲劳损伤实验研究

对碳纤维复合材料某型飞机垂直尾翼方向舵悬挂支臂完成了谱载疲劳、冲击损伤、损伤扩展和剩余强度试验，采用超声波检查方法对其全过程的损伤状态进行了跟踪实验研究，其结果与位移等试验一致．     

On the problem of interfacial damage in fibre-reinforced composites under variable loads

In this paper, the theoretical background for the failure analysis of fibre-reinforced composites under variable repeated loads in the framework of direct methods is presented. It is based on a local shakedown analysis in a representative volume element of the composite and the use of averaging techniques to study the influence of each component (matrix, fibre and interface) on the macroscopic response of such composite.     

疲劳损伤问题中有效应力的一种定义

有效应力是损伤力学中的一个重要概念,这个概念的提出为用无损状态下的本构方程描述有损伤材料的行为提供了有效手段.本文探讨损伤力学中有效应力的定义,通过对损伤演化规律的分析,指出有效应力的一般定义不适用于疲劳损伤问题.本文认为,疲劳问题中的有效应力应该以等效寿命为基础,并根据剩余寿命的概念引入了疲劳损伤问题中有效应力的一种定义.     

疲劳损伤伤演方程中材料常数的确定

损伤力学作为近年来固体力学的一个非常活跃的分支,其本构关系和损伤演化方程是核心内容。损伤演化方程中材料常数的确定,是损伤力学中最基本却很重要的工作。利用大范围损伤下的预估拉压和弯曲疲劳裂纹形成寿命的封闭解答,应用最小二乘法给出了确定损伤演化方程dD/dN=α(Δε)m中材料常数α、m的方法。该方法可作为确定这种类型损伤演化方程材料常数的一般方法。     

负温钢纤维混凝土受压损伤过程的实验研究

利用岩石力学试验系统(RMT)对负温下钢纤维混凝土进行了单轴压缩实验,测得了-5℃、-10℃、-15℃、-20℃下钢纤维混凝土的应力-应变曲线、杨氏模量、极限应力、泊松比等。实验结果表明材料的强度、杨氏模量随温度的下降而上升,尤其是当温度由-10℃下降至-15℃时,这些物理量变化特别显著,之后它们将逐渐趋于某一稳定值。本文对钢纤维混凝土力学性能的温度效应进行了分析并对实验结果进行了细观上的讨论。最后针对负温钢纤维混凝土应力-应变曲线的特点,基于塑性力学和损伤力学理论,建立了负温钢纤维混凝土的含损伤本构方程。该方程物理概念清晰,形式简单,具有一定的应用参考价值。     

Micromechanics-based elastic damage modeling of particulate composites with weakened interfaces

A micromechanical framework is proposed to predict the effective elastic behavior and weakened interface evolution of particulate composites. The Eshelby’s tensor for an ellipsoidal inclusion with slightly weakened interface [Qu, J., 1993a. Eshelby tensor for an elastic inclusion with slightly weakened interfaces. Journal of Applied Mechanics 60 (4), 1048–1050; Qu, J., 1993b. The effect of slightly weakened interfaces on the overall elastic properties of composite materials. Mechanics of Materials 14, 269–281] is adopted to model spherical particles having imperfect interfaces in the composites and is incorporated into the micromechanical framework. Based on the Eshelby’s micromechanics, the effective elastic moduli of three-phase particulate composites are derived. A damage model is subsequently considered in accordance with the Weibull’s probabilistic function to characterize the varying probability of evolution of weakened interface between the inclusion and the matrix. The proposed micromechanical elastic damage model is applied to the uniaxial, biaxial and triaxial tensile loadings to predict the various stress–strain responses. Comparisons between the present predictions with other numerical and analytical predictions and available experimental data are conducted to assess the potential of the present framework.     

电荷耦合器件在质子辐照下的粒子输运仿真与效应分析

应用蒙特卡洛方法计算了质子在科学级电荷耦合器件(charge-coupled device, CCD) 结构中的能量沉积, 并结合该CCD的质子辐照试验及退火试验数据, 分析了器件的辐射损伤机理. 仿真计算体硅内沉积的位移损伤剂量和栅氧化层的电离损伤剂量, 辐照与退火试验过程中主要考察暗信号、电荷转移效率两个参数的变化规律. 研究结果显示, 暗信号和电荷转移效率的变化规律与位移、电离损伤剂量一致; 退火后暗信号大幅度降低, 辐照导致的表面暗信号增加占总暗信号增加的比例至少为80%; 退火后电荷转移效率恢复较小, 电荷转移效率降低的原因主要为体缺陷. 通过总结试验规律, 推导出了电荷转移效率退化程度的预估公式及其损伤因子k_damage.