Z125与N234对NR和S-SBR硫化胶增强效果的比较

在比表面积相近的情况下,探讨白炭黑(Z125)及碳黑(N234)对天然橡胶(NR)和溶聚丁苯橡胶(S-SBR)硫化胶的抗割口增长能力及动态力学性能的影响.结果表明,Z125和N234对NR和S-SBR两种硫化胶的增强效果相差不大;NR硫化胶的抗割口增长能力明显好于S-SBR硫化胶;NR中填充Z125的抗割口增长能力好于N234且随疲劳次数的增加Z125的优势更加明显,而S-SBR中填充N234的抗割口增长能力好于Z125且两者的抗割口增长速率基本不随疲劳次数的增加而改变;Z125使NR和S-SBR硫化胶在0℃和70℃下的tanδ值分别低于N234增强相应硫化胶.     

乙醇液滴蒸发过程对压力振荡动态响应的试验研究

设计制造了一种旋转式气流换向阀,使用该换向阀能够产生较高频率、较大振幅的压力振荡,在此基础上建立了压力振荡环境下燃料液滴蒸发过程的试验系统,利用高速阴影成像系统对乙醇液滴蒸发过程对压力振荡动态响应特性进行了试验研究,试验结果表明,乙醇液滴蒸发过程对压力振荡具有快速响应的能力,压力振荡过程中,蒸发速率并不与环境压力的值成正比,蒸发速率的最大值发生在压力下降过程的后期阶段,蒸发速率的大小与压力振荡的频率、振幅有关。     

绝热材料动态烧蚀试验方法

为了研究绝热材料的动态烧蚀特性,建立了一种敞开环境下绝热材料烧蚀表面的实时监测方法,用光学技术实时记录绝热材料试样表面烧蚀形貌和烧蚀面退移过程,通过图像处理,成功获得了绝热材料动态烧蚀率和烧蚀形貌的相关信息。该监测方法可对一定条件下炭化层的动态烧蚀性能进行评估,通过图像的批处理可获得每一时刻的动态烧蚀率和前n秒的平均线烧蚀率,适用于绝热材料动态烧蚀特性研究,还可以用于研究在绝热材料表面的炭化层形成和消耗特性。     

基于峰度的变步长恒模盲均衡技术

相对于基于训练序列的均衡方式,盲均衡能够提高信道利用率,更适于自适应组网和侦听,其中的恒模算法因实现简单而受到广泛关注,但是固定步长的恒模盲均衡器存在收敛速度和稳态误差上的矛盾。根据峰度定理,盲均衡器输出信号的峰度小于等于源信号的峰度,且只有达到收敛时才相等。文章采用均衡器输出信号峰度误差控制步长的变化,仿真表明变步长均衡器能够一定程度克服这一矛盾。     

浅析影响高模量碳纤维/ 树脂基复合材料力学性能的因素

为提高高模量碳纤维复合材料的力学性能,研究改性氰酸酯、5228、4211与碳纤维结合面结合性能.用SEM、AFM、微脱粘仪、万能力学试验机等仪器设备,观察了碳纤维表面微观形貌、树脂基体与碳纤维结合面微观粘接情况,并对复合材料的宏观力学性能进行分析研究.结果表明,高模量碳纤维随着模量的提高,袁层的缺陷与沟槽减少、表面活性降低,与树脂的结合面粘接强度减弱;改性氰酸酯与纤维的结合面粘接性能较好、5228次之、4211较差;树脂与纤维结合面粘接强度大的,其复合材料的力学性能好.     

T800/5228E复合材料层合板动态冲击力学响应

研究了宽冲击能量范围(12.8、25.5、34.2、42.3与51 J)内T800/5228E复合材料层合板动态冲击力学响应历程.结果表明,复合材料层合板损伤历程依次为裂纹引发→分层扩展→最大损伤→二次损伤等,冲击能量基本不会对其发展演化历程产生影响;力学损伤参数研究发现,赫兹失效载荷Fh与冲击能量成线性关系,而最大作用载荷Fmax与冲击能量为特定指数函数关系.不可逆能量Lw与能量吸收率η研究表明,两者均与冲击能量保持单调递增关系,反映复合材料板的损伤程度在加重,但损伤面积基本趋于稳定,纤维断裂等二次损伤可能成为新型能量吸收方式.     

Analytical Solution for Predicting In-plane Elastic Shear Properties of 2D Orthogonal PWF Composites

This paper proposes a new analytical solution to predict the shear modulus of a two-dimensional(2D) plain weave fabric(PWF) composite accounting for the interaction of orthogonal interlacing strands with coupled shear deformation modes including not only relative bending but also torsion,etc.The two orthogonal yarns in a micromechanical unit cell are idealized as curved beams with a path depicted by using sinusoidal shape functions.The internal forces and macroscopic deformations carried by the yarn families,together with macroscopic shear modulus of PWFs are derived by means of a strain energy approach founded on micromechanics.Three sets of experimental data pertinent to three kinds of 2D orthogonal PWF composites have been implemented to validate the new model.The calculations from the new model are also compared with those by using two models in the earlier literature.It is shown that the experimental results correlate well with predictions from the new model.     

微小推力冷气发动机动静态性能实验研究

针对所设计的微小推力冷气发动机进行高空模拟试验,搭建了试验系统,并应用推力测试装置测量了发动机不同推进剂下的推力和比冲,得到了发动机的稳态特征参数,当分别以丙烷和氮气为推进剂时,平均比冲分别为83.5s和75.6s.为了获得发动机的动态特征参数,对推力测量装置进行了负阶跃力和正阶跃力动态标定,通过标定数据的对比验证得到推力测量系统的延迟时间为90ms;进而在特定试验工况下,给出了发动机和推力测量装置实际上升时间的计算方法,得到丙烷质量流量为40mg/s时,发动机的上升时间为27.1 ms.     

Numerical and experimental investigation on dynamic performance of bump foil journal bearing based on journal orbit

Widespread usage of bump-type foil journal bearing (BFJB) in oil-free micro-turbomachinery requires accurate predictions of dynamic performance characteristics, although it remains a challenging issue because BFJB reflects nonlinear both structurally and aerodynamically. This paper presented a simple experimental method to semi-directly obtain the minimum film thickness and dynamic stiffness of BFJB using the journal orbit. Numerical calculations and simulations are conducted to validate the experimental method. The micro-deformation and interaction of various foils are taken into consideration to improve the model precision. The results from the numerical model regarding the BFJB dynamic characteristics are compared with the experimental results coming from a dedicated test rig, which shows that the experimental results fluctuate obviously and agree not well with the numerical results at the start stage due to the presence of dry friction at that time, nevertheless, they show fantastic agreement as soon as a gas film is gradually generated to separate the shaft from the top foil. Therefore, the proposed experimental method is effective to predict film thickness and dynamic characteristics during the period from the lift-off time to the land-off time. The dynamic characteristics, along with the journal orbits also can be used to rapidly predict the dynamics behavior of rotor-bearing systems.     

面向空间应用的双核容错微处理器的研究与实现

介绍了用双核微处理器实现的容错微处理器系统SPARC—V8FIS。该系统由两个同构微处理器与支持容错操作的容错管理模块组成。微处理器是基于SPRARCV8规范的32-bit微处理器。容错管理模块提供了错误检测、诊断、从“软故障”中故障恢复，以及当发生“硬故障”时，将系统配置成单一处理器继续执行的机制，以适应空间复杂环境应用。SPARC—V8FIS用较少的硬件实现了所有容错操作，以很低的性能损失达到了很高的系统可靠性。