基于有限元分析的板料形状对S梁拉深的影响

基于DYNAFORM动力显式有限元分析软件,将数值模拟技术应用于S梁的坯料优化过程,研究了不同的毛坯形状、尺寸对S梁拉深的成形极限图、厚度分布、减薄率的影响。通过对比分析不同的坯料成形模拟结果,确定较为合理的毛坯形状尺寸。研究结果表明:方式1是不可取的,而方式2能很好地成形出合格零件,最大减薄率为16.6%,最大增厚率为1.84%。在法兰处可以适当添加拉延筋以缓解起皱趋势。     

SGCMGs驱动的挠性航天器有限时间自适应鲁棒控制

针对挠性航天器系统中同时存在单框架控制力矩陀螺群(Single gimbaled control moment gyroscopes, SGCMGs) 摩擦非线性、电磁干扰力矩、惯量摄动以及外部干扰等问题, 提出了一种有限时间自适应鲁棒控制(Finite-time adaptive robust control, FTARC) 方法. 针对系统中存在未知参数的情况, 分别设计自适应更新律, 使得控制器的设计不依赖参数信息, 同时减小外部干扰对系统的不利影响. 应用Lyapunov稳定性理论证明了闭环系统姿态角误差和姿态角速度误差可在有限时间内收敛到原点附近的邻域内. 仿真结果表明, 所提控制律可实现挠性航天器姿态快速机动, 并获得甚高指向精度.     

基于LabVIEW的转动惯量测量系统设计

根据转动惯量测量试验要求,基于图形化编程语言LabVIEW8。2为平台,设计出一套转动惯量测量系统。该系统通过LabVIEW串口通信程序将采集数据传送到PC机,由LabVIEW测量系统对数据进行转换、曲线拟合处理和计算,实现了数据的实时获取、显示、存储。为简化曲线拟合处理程序,采用了LabVIEW与MATLAB相结合的方法对数据进行曲线拟合,得到了良好的效果。该系统满足了测量转动惯量试验的要求。     

有限元分析在解决沙漠胎66×44.00-25径向裂口的应用

利用有限元分析66×44.00-25径向裂口原因,探究产生机理,提出改进方向。结果表明：通过调整胎体和缓冲帘线角度、提高胶料的耐屈挠和耐老化性能,可以解决66×44.00-25早期径向裂口。     

大输出微控制力矩陀螺的设计

为了提高微控制力矩陀螺的输出力矩,提出了一种微型控制力矩陀螺的设计方案.所设计的微型控制力矩陀螺用角振动代替了传统控制力矩陀螺的转动,由转子角振动系统及框架角振动系统组成,实现了基于科氏效应的控制力矩输出.通过框架角振动系统的电极位置居中设置及在玻璃上挖槽的设计,避免了静电吸合现象.四个完全相同的微型控制力矩陀螺构成一...     

油气分离器失效分析

通过对油气分离器失效部位进行宏观检查、化学成分分析、金相分析、力学性能测试、断口形貌观察及能谱分析,认为工艺介质中硫化氢浓度的上升和材料纯净度不高是导致设备失效的根本原因,并提出了相应的建议。     

A statistical micromechanical model of multiple cracking for ultra high toughness cementitious composites

A new statistical micromechanical model of multiple cracking is proposed in which a general expression of the fiber bridging stress laws in the crack plane is established. In this model, the random distribution properties of fibers are considered. And the Weibull function is adopted to represent the flaw size distribution. The relationships of stress versus strain and crack width versus strain are proposed. The formulas of the crack width, crack space, strain capacity and fracture energy density at the end of multiple cracking processes are also deduced. The validity of the proposed model was demonstrated by experimental results.     

SCr420HB钢材D粗夹杂物分析及控制措施

本文针对SCr420HB汽车钢钢材D粗1．5级的质量问题,分析了产生的原因,提出了具体控制措施,使钢材高倍夹杂物Dm级别达到QJ／DT01．13135-2009标准要求。     

Effect of Cyclic Loading on Cracking Behaviour of X-70 Pipeline Steel in Near-Neutral pH Solutions

The cracking behaviour of X-70 pipeline steel in near-neutral pH solutions was studied under different modes of cyclic loading. The crack propagation process of X-70 pipeline steel under low frequency cyclic loading condition was controlled mainly by stress corrosion cracking (SCC) mechanism. Under mixed-mode cyclic loading, both higher tensile stress and shear stress made cracks easier to propagate. Applied cathodic potentials and high content of carbon dioxide in solutions also promoted the propagation of cracks. The propagation directions of cracks were different under different cyclic loading conditions. Under mode I (pure tensile stress) cyclic loading condition, cracks were straight and perpendicular to the tensile stress axis, while under mixed-mode I/Ill (tensile/shear stress) cyclic loading, cracks were sinuous and did not propagate in the direction perpendicular to the main tensile stress axis. Under the mixed-mode cyclic loading, cracks were much easier to propagate, suggesting that shear stress intensified the role of tensile stress. In addition, shear stress promoted the interaction between cracks, resulting in easier coalescence of cracks.