某型飞机双座弹射轨迹仿真分析

以HTY-8座椅为原型,建立了具有轨迹发散作用的仿真模型,通过仿真,比较分析了发散火箭在不同冲量和不同弹射条件下对弹射轨迹的影响。仿真结果表明,在零速度或速度较低的弹射条件下,采用发散火箭是必要的。在中高速弹射条件下,由于前后座椅弹射具有一定的时间差,X方向轨迹离散,前后座椅弹射轨迹发散,发散火箭的作用并不明显,尚需进一步分析人椅分离后先弹射的座椅的运动轨迹。在不利姿态弹射条件下,横滚时发散火箭作用并不明显,俯冲时则能够起到轨迹发散作用。     

军用飞机弹射座椅惯量计算

人椅系统惯量是弹射救生6自由度性能计算所需的非常重要的数据。在以往的简化计算中，惯量的计算结果精度不够，不能满足使用要求。这里根据人椅系统的实际结构、尺寸构造三维实体模型，从而计算其重量、重心及惯量，其中人体分第5、50及95百分位，分别对应座椅的上、中及下位。计算结果成功地用于地面试验中。此方法可以精确地计算弹射座持的惯性矩及惯性积。     

某型火箭弹射座椅椅盆侧板基于穿盖条件的强度仿真研究

本文以火箭弹射座椅及飞机座舱舱盖为研究对象,建立座椅侧板有限元模型和舱盖模型,模拟椅盆侧板的穿盖过程,评估侧板的动态冲击性能。这种方法可降低研发过程中的试验经费,缩短试验周期,具有很重要的工程意义。     

火箭弹射座椅椅盆侧板在1100km/h速度气动载荷下的安全性研究

以火箭弹射座椅侧板为研究对象,研究不同外形的侧板在座椅弹射出舱后承受高速气流吹袭的能力,评估侧板及其连接件的安全性。这种研究方法可在同类型弹射座椅上推广应用。     

多自由度坐姿人体上体系统动力学建模与振动特性研究

针对动态环境汽车人机界面设计分析的需要，依据多体动力学原理建立了坐姿人体上体系统4自由度的垂直振动模型，并推导了描述人体位移、速度和加速度三种响应的STH，DPM，AM理论表达式．依据已有的人体振动试验数据，运用系统辨识方法，进行振动模型的动力学参数识别，并将所识别出的参数进行人体振动特性计算．验证研究表明，所计算出的人体振动特性数据与人体振动特性测试数据有较高的吻合度．以汽车人机界面设计为实例，通过模型研究了人-车（人-椅）系统人体和座椅的振动特征．所得结果对合理选取汽车座椅参数，提高汽车人机界面设计的宜人性和合理性有一定的指导意义．     

弹射座椅气动参数的数值计算

为了解决弹射座椅研究中风洞试验不足和气动参数缺乏的问题,尝试了采用计算流体力学（CFD） 方法,利用CFD计算软件Fluent求解N－S方程,对弹射座椅的外流场进行数值计算,求得了弹射座椅不同姿态 下的气动参数值,并将部分气动参数与风洞试验的测量值进行了对比,结果发现,计算结果与试验值的变化趋 势完全相同,大多数计算值与试验值的误差都在１０％以内,能够满足工程计算的需要,可以作为试验值的补充 和替代。通过CFD方法在弹射座椅气动参数计算中的应用,可以看到CFD方法在弹射座椅的研究中有着广阔的 应用前景。     

面向座椅舒适性分析的三维人体参数化建模

应用三维坐姿人体模型可在座椅的设计阶段高效精确地进行座椅几何舒适性分析。参照二维坐姿人体模板拟定三维坐姿人体模型的结构要素,采用基于特征造型的方法构建三维人体模型。采用基于原型模型的参数化建模方法,实现对三维坐姿人体模型的参数化驱动。通过＂人—椅＂模型的几何匹配,自动精确提取坐姿人体模型的姿态角度,对比人体坐姿标准舒适角度范围,实现座椅舒适性的评价和分析。     

面向人体振动响应的ISD悬架座椅性能分析

为解决悬架座椅设计中降低固有频率和保证系统刚度之间的设计矛盾,进一步改善悬架座椅舒适性,将惯容器运用到悬架座椅系统中。建立了ISD(Inerter-Spring-Damper)悬架座椅模型,选出了最适合座椅的ISD结构,并结合三自由度坐姿人体模型(ISO 5982—2001)模型)建立了四自由度人-椅系统集中参数模型。根据座椅台架试验对悬架座椅参数和人体参数进行了识别。分析了模型在不同频段下的动态响应,惯质系数在不同频段激励下的取值,以及惯质系数对座椅舒适性的影响和惯质系数与阻尼的匹配关系。结果显示,将惯容器运用于悬架座椅能明显降低系统固有频率、改善座椅舒适性;惯容器、弹簧和阻尼器三者并联是最适合悬架座椅隔振的ISD结构,舒适性的改善程度和最优惯质系数取值都与激励特征有关。     

座椅材料的热舒适及其评价

本文分析了座椅的热舒适性对人体的影响,阐述了座椅材料与热舒适相关的几项物理性能及测试方法,最后提出了座椅热舒适性的主客观评价方法。在客观评价方法中,除测试座椅材料的热物理指标外,还可以采用探头式温湿度计测量人一椅界面问温湿度,同时进行主观评价,从而将主客观评价结果很好的联系起来。     

基于加速粒子群算法的车辆座椅悬架最优控制研究

针对传统最优线性二次型控制器中加权矩阵往往由设计者根据经验确定的问题,提出一种应用加速粒子群算法确定加权矩阵的方法。建立"车轮-车身-座椅、人体"6自由度随机振动系统模型,采用加速粒子群算法对座椅悬架进行参数优化,并对优化后系统进行最优线性二次型控制。将基于加速粒子群算法的最优线性二次型座椅悬架系统中"座椅、人体"垂向加速度与初始系统及基于常规粒子群算法和遗传算法的最优线性二次型控制系统进行对比,验证了此控制系统的有效性和优越性。     

Layer thickness and draft angle selection for stereolithography injection mould tooling

The introduction of rapid prototyping has allowed engineers and designers to generate physical models of required parts very early on in the design and development phase. Further to this, the use of stereolithography (SL) cavities as a rapid tooling method has allowed plastic prototype parts to be produced in their most common production manner -- by injection moulding. The process is best suited to small production runs where the high costs of conventionally machined tooling is prohibitive. One of the major drawbacks of the SL injectionmoulding process is the susceptibility of the tools to premature failure. SL tools may break under the force exerted by part ejection when the friction between a moulding and a core is greater than the tensile strength of the core, resulting in tensile failure. Very few justified recommendations exist about the choice of mould design variables that can lower the part ejection force experienced and reduce the risk of SL tool failure. This research investigates the ejection forces resulting from SL injection moulding tools which are identical in all respects except for their build layer thickness and incorporated draft angles in an attempt to identify appropriate evidence for recommendations with respect to these design variables and SL injection moulding. The results show that adjustment of draft angle results in a change of part ejection force as a reasonably linear relationship. An adjustment of the build layer thickness results in a change in part ejection force as a more non-linear relationship. The adjustment of build layer thickness had a greater effect on ejection force than the adjustment of draft angle. The results also show that the surface roughness of all tools remains unchanged after moulding a number of parts in polypropylene. A mathematical model was used in an attempt to predict ejection forces according to the moulding material used. This model reflected the experimental results in terms of relative values but not in absolute values, which may be due to inappropriate specific values used in their calculation. Finite element analysis (FEA) was used in an attempt to identify the factors involved in the ejection process. Results indicate that the effect of draft angle on ejection force is due to elastic deformation of the surface roughness. A fact borne out by the lack of damage to the surface after ejection.     

A strategy for designing stable nanocrystalline alloys by thermo-kinetic synergy

Aiming to design stable nanocrystalline(NC) materials, so far, it has been proposed to construct nanostructure stability maps in terms of thermodynamic parameters, while kinetic stabilization has seldom been considered, despite the synergy of thermodynamics and kinetics. Consequently, the thermodynamically stabilized NC materials may be easily subjected to grain growth at high temperatures due to the weakly kinetic stabilization. Starting from the thermo-kinetic synergy, a stabilization criterion is proposed as a function of intrinsic solute parameters(e.g. the activation energy for bulk diffusion and the segregation enthalpy), intrinsic solvent parameters(e.g. the intrinsic activation energy for GB migration and the GB energy) and processing parameters(e.g. the grain size, the temperature and the solute concentration). Using first-principles calculations for a series of combinations between fifty-one substitutional alloying atoms as solute atoms and Fe atom as fixed solvent atom, it is shown that the thermal stability neither simply increases with increasing the segregation enthalpy as expected by thermodynamic stabilization, nor monotonically increases with increasing the activation energy for bulk diffusion as described by kinetic stabilization. By combination of thermodynamic and kinetic contributions, the current stabilization criterion evaluates quantitatively the thermal stability, thus permitting convenient comparisons among NC materials involved by various combinations of the solute atoms, the solvent atoms, or the processing conditions. Validity of this thermo-kinetic stabilization criterion has been tested by current experiment results of Fe-Y alloy and previously published data of Fe-Ni, Fe-Cr, Fe-Zr and Fe-Ag alloys,etc., which opens a new window for designing NC materials with sufficiently high thermal stability and sufficiently small grain size.     

Motivating drivers to correctly adjust head restraints: assessing effectiveness of three different interventions

Three types of driver educational strategies were tested to determine the most effective approach for motivating drivers to adjust their head restraints to the correct vertical position: (1) a human interactive personal contact with a member of an ICBC-trained head restraint adjustment team, (2) a passive video presentation of the consequences of correct and incorrect head restraint adjustment, and (3) an interactive three-dimensional kinetic model showing the consequences of correct and incorrect head restraint adjustment. An experimental pretest–posttest control group design was used. A different educational treatment was used in each of three lanes of a vehicle emissions testing facility, with a fourth lane with no intervention serving as a control group. Observational and self-reported data were obtained from a total of 1 974 vehicles entering and exiting the facility. The human intervention led to significantly more drivers actually adjusting their head restraints immediately after the intervention than the passive video or interactive kinetic model approaches, which were both no different from the control group. The human intervention was recommended as the most effective and was implemented successfully on a limited basis during 3 months of 1995 and again during 3 months of 1996.     

The pilot dimensions method: reconciling steering and conformity in workshops

In machining workshops, workpieces are produced according to dimensions known as manufacturing dimensions. For the same workpiece and the same manufacturing plan, several sets of manufacturing dimensions can be used but none satisfies simultaneously the two main missions workshops need to fulfil: (a) ensuring conformity of products to their design dimension tolerances (also called blueprint tolerances); and (b) steering machines in order to compensate for tool wear. The set of manufacturing dimensions obtained from the design dimensions using the minimal chain of dimensions method is optimal for a conformity check of workpieces but is practically unusable for steering machines because of the complexity of its relationships toward the tool correctors and tools dimensions. The pilot dimensions method consists of, on the one hand, identifying and representing these tool correctors and these tool/program dimensions on the production drawings (besides the manufacturing dimensions) and, on the other hand, determining their correction values through a mathematical set of relations after having measured the manufacturing dimensions on a workpiece. Doing so will strongly reduce adjustment time, reduce the number of workpieces used for adjustments and greatly enhance the quality of workpiece batches.     

Comparison of the energy absorption capability of crash boxes assembled by spot-weld and continuous joining techniques

The design of vehicle front structures for crashworthiness is nowadays commonly based on a series of rigid subsystems that constitute a nearly undeformable survival cell for the passengers, and deformable subsystems able to efficiently dissipate the vehicle kinetic energy. During frontal crash, which is by far the most dangerous impact situation, the front rails represent the main deformable components aimed to dissipate the kinetic energy of the vehicle, therefore their behaviour is crucial to obtain good vehicle performance, with stable and controlled energy dissipation. The design of the front rail, usually consisting of a thin-walled prismatic column, requires definition of the geometry, that is, of the shape and dimensions of the cross section, of the thickness of the material, and of the material itself.     

两相流喷射器流动模型研究

研究了压缩/喷射制冷系统中两相流喷射器内的射流发展过程,沿喷射器内部射流的流动方向分段对射流压力调整过程、射流混合、均匀过程和扩压过程进行建模,得到喷射器的引射比和出口背压随冷凝温度与蒸发温度的变化特性.模型的预测结果与实验测试结果在变化趋势上完全一致,压缩/喷射制冷循环中的冷凝温度越大,喷射器的引射比和出口背压越大,节能效果越好;蒸发温度存在一个最佳值,使得引射比最大,出口背压增大效果较好.     

Effects of Four Key Process Variables on Size Shrinkages of Low Temperature Co-Fired Ceramic Substrates

The effects of four key process variables on the size shrinkages of low temperature co-fired ceramic substrates were investigated using the methods of design of experiments (DOE), analysis of variance (ANOVA), and multivariable regression. The process variables investigated were raw tape thickness, laminating pressure, coining pressure, and coining time. The results revealed that coining pressure had the most significant effect on the size shrinkages of the low temperature co-fired ceramic samples under the process conditions set in this study. The average lateral size shrinkage and thickness shrinkage of the LTCC samples produced with a coining pressure of 320 MPa were significantly lower and higher than those produced with a coining pressure of 50 MPa with shrinkage differences of 3.6% and 6.2%, respectively. The effects of tape thickness, the interaction of tape thickness, laminating pressure, and coining pressure, the interaction of tape thickness and coining pressure, and the interaction of tape thickness and laminating pressure were also significant. Two regression equations were obtained and the shrinkage values could be estimated using them. The coefficients of determination R² were 99.9% and 98.9%, respectively, and the P values were smaller than 0.001 for the two regression equations. This can allow engineers to calculate the dimensions especially lateral dimensions and features such as pad pitches at the design stage and to set the process parameters at the manufacturing stage.     

Pseudo-second order models for the adsorption of safranin onto activated carbon: comparison of linear and non-linear regression methods

Kinetic experiments were carried out for the sorption of safranin onto activated carbon particles. The kinetic data were fitted to pseudo-second order model of Ho, Sobkowsk and Czerwinski, Blanchard et al. and Ritchie by linear and non-linear regression methods. Non-linear method was found to be a better way of obtaining the parameters involved in the second order rate kinetic expressions. Both linear and non-linear regression showed that the Sobkowsk and Czerwinski and Ritchie's pseudo-second order models were the same. Non-linear regression analysis showed that both Blanchard et al. and Ho have similar ideas on the pseudo-second order model but with different assumptions. The best fit of experimental data in Ho's pseudo-second order expression by linear and non-linear regression method showed that Ho pseudo-second order model was a better kinetic expression when compared to other pseudo-second order kinetic expressions.     

湿喷机机械臂喷枪振动特性的研究

为了提高某公司生产的CHP30型湿喷机机械臂的工作性能,运用D H坐标法对该机械臂进行运动学分析;基于刚柔耦合系统动力学理论,建立了机械臂的刚柔耦合模型,利用ADAMS分别对机械臂的刚性模型和刚柔耦合模型进行了动力学分析,得到了不同载荷情况下机械臂末端在各坐标轴方向上的位置曲线.仿真结果表明：机械臂和混凝土的重力动载荷以及喷射作用力是其产生振动的主要原因,最大振幅约为0.04 m,与实际情况相吻合;端部喷射作用力对机械臂末端振动的影响程度因喷射方位的改变而变化,喷射侧面时,振幅最大,喷射顶部时,振幅最小;橡胶输送管悬挂在2个锁扣上时对机械臂的振动影响较小.仿真结果对湿喷机机械臂的设计有一定的指导作用,同时为机械臂末端的轨迹规划和机械臂的疲劳分析提供了理论依据．