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.     

CICC型超导导体外壳制作工艺研究

通过焊接参数的选定(焊接电流 I=150A,电压U=8.8V,焊接速度0.7～1m/min),保证单根导体长度不小于300m,焊缝无气孔,裂纹等焊接缺陷.使焊接后的CICC超导导体内部最接近焊缝位置的温度低于183℃,确保导体导电性能,导体焊缝耐压试验不低于5MPa,且氦气密性能良好,研制出的产品满足相关技术标准的质量...     

2A14铝合金返修焊技术

根据2A14铝合金的冶金特点，针对对接接头和锁底焊缝的不同要求，提出了相应的采用缺陷槽的补焊工艺。分析了焊接位置、补焊层数及两面补焊、预热和缓冷、补焊的收／起弧及长度、电源选择、环境控制、补焊顺序和方向，以及装配等因素的影响。由不同运载贮箱补焊的结果可知，该工艺措施有效，补焊质量较好，提高了补焊的一次合格率。     

Mechanical behavior of the metal parts welded with extraterrestrial regolith simulant by the solar concentrator in ISRU & ISRF application

The use of in-situ resources plays an important role on future extraterrestrial human activities for the facility repair and habitat construction, especially in sustainable space exploration of Moon and Mars. A method of the metal welded with extraterrestrial regolith simulant using solar processing under ambient conditions is presented. Metal parts are made of Q235B ferroalloy and TA2 titanium alloy into standard tensile members according to the ASTM code. They are disconnected from the middle in advance, and then welded together with lunar and Martian regolith simulant under ambient conditions, respectively. The entire welding process and precautions are detailed. Additionally, the mechanical behavior of weldments is characterized regarding their tensile strength. Furthermore, the fusion zone of weldments is studied by Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) measurements. The results show that it is possible to weld metal parts together with extraterrestrial regolith simulant by the solar concentrator. The average ultimate tensile strength of ferroalloy specimens welded with lunar and Martian regolith simulant is 2.94 MPa and 1.66 MPa; The average ultimate tensile strength of titanium alloy specimens welded with lunar and Martian regolith simulant is 4.95 MPa and 2.59 MPa. Moreover, the failure mode of all weldments was brittle failure. The welding joints strength derives from the phases that the regolith as the solder fusing into ferroalloys in a homogeneous way and titanium alloys in an inhomogeneous way. The presented method may provide a new thought for astronaut assistance associating with repairing and fabricating in subsequent Moon and Mars missions.     

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。     

振动处理对铝合金焊接结构变形与内应力的影响

铝合金的焊后延迟变形是生产中影响产品质量的重要问题，本文研究一种投资少、见效快的解决方法－振动处理。实验证明振动处理能降低铝合金焊接结构残余应力峰值，使内应力均匀化，对于控制焊接延迟变形有明显效果。振动后对焊缝组织的微观结构分析显示，振动处理降低了位错密度，因为位错密度是内应力的直接表征，因此振动处理的作用效果可以用振动前后微观结构的变化来解释。     

PARAMETER IDENTIFICATION METHOD OF NONLINEAR JOINTS

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公路隔离网专用焊机微机控制系统研制

介绍了公路隔离网专用焊机微机控制系统的功能、系统的硬件结构和软件设计。控制系统具有手动、半自动、全自动等工作方式，可自动补偿网压波动对焊接电流的影响。批量生产应用表明：控制系统操作方便，性能可靠，焊接质量稳定。