Highly thermally conductive POSS-g-SiCp/UHMWPE composites with excellent dielectric properties and thermal stabilities

Polyhedral oligomeric silsesquioxane grafting thermally conductive silicon carbide particle (POSS-g-SiCp) fillers, are performed to fabricate highly thermally conductive ultra high molecular weight polyethylene (UHMWPE) composites combining with optimal dielectric properties and excellent thermal stabilities, via mechanical ball milling followed by hot-pressing method. The POSS-g-SiCp/UHMWPE composite with 40 wt% POSS-g-SiCp exhibits relative higher thermal conductivity, lower dielectric constant and more excellent thermal stability, the corresponding thermally conductive coefficient of 1.135 W/mK, the dielectric constant of 3.22, and the 5 wt% thermal weight loss temperature of 423 °C, which holds potential for packaging and thermal management in microelectronic devices. Agari’s semi-empirical model fitting reveals POSS-g-SiCp fillers have strong ability to form continuous thermally conductive networks.     

一种柔性曲柄滑块机构的解耦控制方法

基于对柔性机构运动学和动力学模型的分析与解耦,提出一种解耦控制方法。这种方法有效地利用了模型信息,将反馈划分为由刚性和柔性运动两路反馈,通过两组不同的控制器分别计算各自的输出量,并在控制器输出端叠加输出。针对曲柄滑块机构进行柔性动力学建模并实施了轨迹跟踪仿真。与同样基于动力学模型的计算力矩法进行了对比,结果证明本方法的可行性和高效性。     

A model for the static fracture toughness of ductile structural steel

Fracture of ductile structural steels generally occurs after void initiation, void growth and void coalescence. In order for ductile fracture of structural steels to occur, energy must be spent to induce void initiation and void growth. Therefore, fracture toughness for ductile fracture should be contributed from void initiation and void growth. On the basis of this suggestion static fracture toughness (K_IC) of ductile structural steels is decomposed into two parts: void nucleation-induced fracture toughness (denoted as K_IC.n) and void growth-induced fracture toughness (K_IC.g). K_IC.n, defined as the stress intensity factor at which voids ahead of a crack begins to form, is calculated from crack tip strain distribution and void nucleation strain distribution. In contrast, K_IC.g is determined by the void growth from the beginning of void nucleation to void coalescence. Therefore, K_IC.g relates to the void sizes and void distribution. In this paper, the expression for K_IC.g is given from the void sizes directly from fracture surfaces. The relationship between K_IC.n, K_IC.g and K_IC is expressed in the form (K_IC)²=(K_IC.n)²+(K_IC.g)². The newly developed model was applied to the fracture toughness evaluation of three structural steels (SN490, X65 and SA440), and the theoretical calculation agrees with the experimental results.     

Phase Field Modelling Allotropic Transformation of Solid Solution

Based on multiphase field conception and integrated with the idea of vectorvalued phase field, a phase field model for typical allotropic transformation of solid solution is proposed. The model takes the non-uniform distribution of grain boundaries of parent phase and crystal orientation into account in proper way, as being illustrated by the simulation of austenite to ferrite transformation in low carbon steel. It is found that the misorientation dependent grain boundary mobility shows strong influence on the formation of ferrite morphology comparing with the weak effect exerted by misorientation dependent grain boundary energy. The evolution of various types of grain boundaries are quantitatively characterized in terms of its respective grain boundary energy dissipation. The simulated ferrite fraction agrees well with the expectation from phase diagram, which verifies this model.     

油箱涂料涂层脱落原因分析及修补方案评估

针对飞机壁板在装配时出现的掉漆现象,通过湿胶带结合力、耐溶剂性、耐水性、耐盐水和燃油性、耐RP-3燃油性以及耐霉菌性等性能试验,以验证该批次材料的使用性能。同时针对耐水性试验不合格的问题,对试验结果进行了分析,以评估已装机零件使用的可行性,并就零件的涂层修补方案进行了可行性验证。     

飞机电子系统线路的故障维修分析

飞机电子线路在飞行过程中的运行状态会对飞机飞行性能造成直接影响。电子线路在实际工作中会产生一些故障,此种故障较为常见,并且故障表现形式会存在一定差异。本文能对飞机线路维修方法进行简单阐述,对线路故障检修措施进行简单分析,最后提出线路故障预防措施。     

载荷谱飞行实测振动环境谱数据处理研究

通过开展飞机振动环境谱的飞行实测,获取飞机设备舱、管路、部分飞机结构等振动环境情况,经过数据处理获取能够反映飞机实际使用下的振动环境数据,给出了典型任务剖面的功率谱密度处理结果,为飞机耐久性/损伤容限优化设计提供依据,进一步提高飞行的安全性和可靠性。     

民用飞机研制项目详细设计评审准则及流程

民用飞机研制过程中详细设计阶段的转段评审是十分重要的里程碑,在冻结设计基线、规划好全面试制和验证阶段的研制任务等方面意义重大。作为项目管理团队,严格按照阶段性退出准则,策划并组织好详细设计转段评审,不仅能够规避项目研制过程中重大技术风险,同时也能为项目在下一个研制阶段有序运行奠定良好的基础。     

定子套加热设备的研究及其电气系统设计

根据加热设备的实际需求,改变定子套的传统加热方法,对定子套感应加热专用设备进行了研究,以高频机为热源,采用信息技术、现代控制技术、机械结构设计等技术,对其设备结构和电气系统进行了设计和研究,主要包括设备的运行流程以及其电气系统原理图等。利用可编程逻辑控制器(PLC)实现对高频机以及外围设备等附件单元的控制,使其实现了对定子套进行高效、自动化加热以及规模化,使其具有节能,污染小等优势。经过实际的应用取得了良好的效果,满足了企业生产和设计要求。     

基于多体动力学的尾撬缓冲器动态性能研究

为了获得民机尾撬缓冲器吸能功量特性,提出了一套结合理论分析、协同仿真及试验验证的系统分析方法。以缓冲器理论分析模型为基础,建立了包含缓冲器动力学和液压系统的协同仿真模型;规划并实施了相应的落震仿真试验,将仿真结果与试验结果进行对比分析,验证了仿真模型的有效性和分析方法的可行性;详细讨论了不同充气压力和投放高度等关键参数对缓冲器动态性能的影响,总结了缓冲器功量、最大行程及最大轴向力随相关参数的变化规律。分析方法和结论可用于指导尾撬缓冲器的设计和选型,对民机的试飞工作具有一定的参考价值。