紧固件连接部位热应力分析的理论算法

高超声速飞行器飞行过程中受到严酷的气动加热,导致紧固件连接部位由于热膨胀系数不匹配产生严重热应力,威胁结构安全,介绍了一种分析实心及空心紧固件连接部位在有或无初始间隙的情况下,承受均匀温度变化时产生的热应力的理论算法,并建立有限元模型进行仿真计算。通过理论算法和有限元计算得到两种接头的热应力大小及分布,两种方法的结果十分接近,说明这种分析算法是可行的,对于快速预估热应力水平、优化连接结构设计具有参考价值。     

复合材料非平面连接接头强度预测

基于渐进损伤分析方法,对一种复合材料非平面连接接头承受轴向拉伸载荷作用下的失效强度进行了研究,建立了三维渐进损伤有限元模型预测连接结构的失效行为,预测的失效载荷和载荷-位移曲线与试验结果的对比一致,验证了分析的有效性。     

Combined and interactive effects of interference fit and preloads on composite joints

The combined and interactive effects of the bolt-hole fit conditions and the preloads of the fasteners on the load carrying capacity of single-lap composite-to-titanium bolted joints have been investigated both experimentally and numerically. Quasi-static tests of the hybrid joints with different fit conditions are implemented, and a three dimensional finite element progressive failure analysis model is proposed to predict the influences of the bolt-hole fit conditions and fastener＇s pre- loads on the mechanical behaviors of the joints. Based on the experimental validated simulation method, a multi-factor, mixed levels orthogonal design table and the analysis of variance method are used to arrange the simulation conditions and to further study the interactive effects of preloads and fit conditions. Through the analysis of the results, for the researched double bolt, single-lap composite-titanium joints, it is found that： the effects of both the interference fit and the preloads change from positive into negative mode with the increase of the interference fit values or preload values; appropriate bolt-hole fit conditions and preloads can improve the bolt-hole contact conditions of the loaded joints, and then retard the fiber failures around the fastener holes, and increase the load carrying capacity of the joints eventually; the interactive effect of the bolt-hole interference fit conditions and preloads cannot be ignored and the parameters need to be considered together and synthetically as the joints are being optimized.     

考虑间隙和拧紧力矩的复合材料钉载分配均匀化方法

一种通过调整钉-孔间隙和拧紧力矩改善复合材料多钉连接钉载分配不均匀性的方法被提出。首先，基于改进的钉载分配测量方法测量各钉承载比例，采用SPSS软件得到各钉载比例的多元线性回归函数，并以钉-孔间隙和拧紧力矩为设计变量，建立多钉连接钉载分配的线性优化模型。然后，采用单纯形算法对优化模型进行求解，得到优化解。最后，以三钉单剪连接为例，对比计算和试验测量结果。结果表明：求解结果与试验测量结果吻合度较高；优化后，最高钉载比例从36.06%降低到33.45%；三钉单剪连接结构承载能力提高约10.8%，且改善结构失效形式为钉-孔挤压失效。     

PARAMETER IDENTIFICATION METHOD OF NONLINEAR JOINTS

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基于随机搜索法的机匣安装边螺栓连接优化设计

引入一种简便的约束优化方法——随机搜索法,通过建立机匣安装边螺栓连接的优化模型,基于Matlab平台进行了实例计算和分析,结果表明该方法应用于机匣安装边的螺栓连接优化是可行的。     

微动疲劳寿命可靠性分析方法研究

针对结构的微动疲劳问题,发展了一种寿命可靠性分析方法。在微动条件下,接触区域处于多轴应力状态,采用基于临界平面法的多轴疲劳参数对结构的微动疲劳寿命进行预测。在确定性寿命计算的基础上,考虑弹性模量、摩擦系数以及寿命预测模型中材料常数的随机性,利用响应面方法,结合Monte-Carlo模拟技术获得结构微动疲劳寿命可靠性模型。最后将此方法用于燕尾榫结构的微动疲劳寿命可靠性分析,验证了所提出方法的可行性和有效性。     

复合材料阶梯形胶接接头渐进损伤分析

建立了复合材料层合板双阶梯形胶接接头的三维(3D)有限元模型,并进行了拉伸载荷下的渐进损伤分析(Progressive damage analysis,PDA)。采用含正交各向异性损伤的连续介质损伤力学(Continuum damage mechanics,CDM)本构方程对层合板进行描述。采用粘聚区模型(Cohesive zone model,CZM)对共胶接界面进行模拟。引入合适的损伤起始和损伤扩展准则,预测了双阶梯形胶接接头的损伤扩展方式和连接效率。进一步讨论了台阶长度、外加铺层搭接长度及厚度对失效模式及连接效率的影响。     

Modeling on mechanical behavior and damage evolution of single-lap bolted composite interference-fit joints under thermal effects

This paper reports the modeling method and outcomes of mechanical performance and damage evolution of single-lap bolted composite interference-fit joints under extreme temperatures. The anisotropic continuum damage model involving thermal effects is established on continuum damage mechanics which integrates the shear nonlinearity constitutive relations characterized by Romberg-Osgood equation. The temperature-induced modification of thermal strains and material properties is incorporated in stress-strain analysis, extended 3D failure criteria and exponential damage evolution rules. The proposed model is calibrated and employed to simulate behavior of composite joints in interference fitting, bolt preloading, thermal and bearing loading processes, during which the influence of interference-fit sizes, preload levels, laminate layups and service temperatures is thoroughly investigated. The predicated interfacial behavior, bearing response and failure modes are in good agreement with experimental tests. The numerical model is even capable of reflecting some non-intuitive experimental findings such as residual stress relaxation and matrix softening at elevated temperatures.     

机械连接中钉的轴力和剪切力测量传感器

对机械连接中测量钉的轴力的各种测试方法进行总结,对复合材料多钉连接中钉载的多种测试方法进行分析,提出了一种能同时测量钉的轴力和剪切力的传感器。根据钉的受力情况和材料力学理论推导出钉的轴力和剪切力的计算表达式。设计了传感器的轴力和剪切力的两套测试装置,分别进行了轴力和剪切力的测试试验。对传感器测试结果的载荷-应变曲线的线性度、重复性进行了分析研究。测试结果表明：传感器的载荷-应变曲线具有良好的线性度和重复性,能满足工程上对测量传感器的技术要求。同时通过测试也发现,传感器的安装角对轴力和剪切力的测量结果无影响;安装紧力矩对剪切力的测量结果有影响,但随着外载的增大,影响会逐渐减小。