冲击波超压存储测试技术研究

目的改进冲击波超压的测试方法,解决传感器长引线带来的安装不便、易受干扰的实际测试问题;方法利用所谓的存储测试技术,将压力传感器、适配电路、A/D转换器、触发控制电路、通讯接口及电池紧凑封装在坚固的钢壳内,构成一种可缮相对独立工作的便携式超压测试仪;结果研制成功了采样频率可编程的存储式超压测试仪,并对0.6kgTNT药柱的爆炸冲击波进行了多点测试,捕获数据完整可靠;结论冲击波超压存储测试技术具有抗干扰性强和无需电缆引线的优点,特别适宜于大范围多测点的试验场合.     

基于分布式测试系统的冲击波压力场重建的研究(英文)

采用存储测试技术设计了一套由多个测试节点组成的分布式测试系统,此系统可用于爆炸冲击波测试。该系统采用上升时间为微秒级的传感器点阵,能够快速响应瞬态冲击波信号。为减小动态响应误差,利用激波管对系统进行了动态标定。在静爆试验中由传感器点阵采集得到的爆炸冲击波超压峰值,采用三次样条插值算法对冲击波压力场进行了重建,并对重建结果进行了误差分析。     

Analysis of rough line contacts operating under mixed elastohydrodynamic lubrication conditions

Heavily loaded machine elements, such as gears, usually operate in the mixed lubrication regime. Surface roughness has a significant effect on the pressure distribution, the subsurface stress field, and the friction coefficient. Based on the superposition of a dry rough and a fully flooded smooth contact, a mixed lubrication model has been developed. The roughness profile is assumed to be known. Surface deformation is calculated by taking into account the pressure distribution that is built up by asperity contacts, asperity interactions, and lubricant flow. Thermal and sliding effects are incorporated into the analysis. Non‐Newtonian lubricant behaviour is considered by using a power‐law rheological model. The pressure distribution, subsurface stress field, and friction coefficient were calculated from the model at several points along the contact path for an FZG type C gear pair. It was shown that a significant part of the load is carried by the contacting asperities. The position of the maximum shear stress is very close to the surface.     

Wet sliding friction of elastomer compounds on a rough surface under varied lubrication conditions

‘Green’ tire bearing tread rubber reinforced with precipitated silica can exhibit improved wet traction performance. The underlying mechanism is currently not well understood. To improve our capability of rational material design for enhanced driving safety, wet sliding friction for various rubber compounds is tested on a Portland cement concrete surface under varied lubrication conditions. The wetting liquid is either ethanol or water, and the initial amount of liquid on the concrete surface is adjusted. Sliding friction is detected to alter with lubrication condition. Under ethanol lubrication, the sliding friction is markedly lower than that under water lubrication. Additionally the benefit in wet traction from silica is significantly diminished or eliminated in ethanol. Such observations cannot be rationalized with simple considerations of rubber bulk viscoelasticity, liquid viscosity, cavitation, or capillary effect. We believe that these observations strongly indicate the significance of interfacial interactions in determining the wet sliding friction of elastomer compounds. The potential relevance of capillary porosity in concrete and Marangoni drying effect to wet traction is also introduced.     

基于FLUENT的离心加速度下气压场仿真研究

针对多参数复合环境试验系统中离心加速度会造成气压场分布不均匀的问题,提出了一种添加风扇搅拌来改善气压场分布均匀度的方法.通过研究离心加速度与气压场的耦合机理,以流体运动控制方程和标准k～ε湍流模型为基础,建立了环境舱内的流体运动模型.采用有限体积数值分析的方法,对无风扇搅拌和有风扇搅拌两种情况下气压场的分布进行了仿真,...     

Determination of interfacial temperatures under extreme pressure conditions

Interfacial temperatures attained in a pin and v-block apparatus under extreme pressure (EP) conditions were measured using pins made from either copper or an aluminum alloy from the asymptotes in the curve of removal rate versus applied load since these have been shown to correspond to the temperatures at which the interfacial material melts. The interfacial temperature rise was proportional to the applied load, where the proportionality constant = A where is the interfacial friction coefficient and A a geometrical constant which has been previously measured for steel pins and v-blocks lubricated by chlorinated hydrocarbons dissolved in a poly -olefin as 2.3 ± 0.3 K/N. Values of A measured when using the aluminum alloy (2.4 ± 0.1) and for copper (2.1 ± 0.2) were in good agreement with this measurement and indicated that interfacial temperatures in excess of 1000 K can be attained during EP lubrication. Finally, the rate of material removal in the pin and v-block apparatus can be related to the metallurgical properties of the pins.     

Dynamic deformation under a modified split Hopkinson pressure bar experiment

This paper presents a modified split-Hopkinson pressure bar (SHPB) technique. The dynamic stress-strain behaviors were estimated at room temperature and subzero temperature to −75°C by using the conventional SHPB and compared with a modified SHPB technique. A computer simulation using a finite element algorithm is also performed to study the dynamic material responses. Furthermore, we attempt to find a proper material constitutive law by using the simulation process. It is suggested that the modified SHPB test used in this study can be successfully utilized to offer an experimental condition of a higher strain rate than that obtained from the conventional SHPB test.     

约束条件下公理化设计方法研究

提出了一种约束条件下解决设计问题的公理化设计方法,其方法主要分两步:(1)先不考虑约束条件,只考虑功能需求根据公理设计法构思初步方案;(2)根据约束条件完善方案,如果有多个约束条件,可分别考虑每个约束条件来逐步完善方案.通过车床螺纹车削系统设计的例子说明了该方法的有效性.     

机载SAR探测海面风场、海浪和海洋内波方法的分析与研究

从海洋环境探测的意义出发,通过分析星载SAR探测的局限性,引出了采用机载SAR探测海洋环境的必要性。分析认为机载SAR探测技术的迅速发展以及海面风场、海浪和海洋内波反演算法的日趋成熟,为机载SAR探测海面风场、海浪和海洋内波提供了可靠的装备、技术和算法支持。针对载机平台相对卫星平台高度低、速度慢和稳定性差的特点,提出了获取满足机载SAR对海探测技术指标和校正探测误差两种方法,以确保探测数据的适用性和准确性,并给出了实现这两种方法的理论依据和总体思路,最后提出了机载SAR探测海面风场、海浪和海洋内波方法的流程。     

A mixed-TEHD analysis and experiment of journal bearings under severe operating conditions

The increasingly high demands for compact design require journal bearings to work under severe operating conditions. A steady-state mixed-TEHD (thermo-elasto-hydrodynamic) model for journal bearings has been developed. The model considers the fluid flow in the gap formed by rough surfaces, asperity contact, surface thermoelastic deformations, and a temperature–pressure–viscosity relationship for the lubricant, as well as an angular misalignment between the journal and the bearing. The model is verified with experimentally measured temperature data. Numerical simulations of the operation of a typical journal bearing are conducted and the importance of several contributing factors in mixed lubrication is discussed. A bearing temperature transition has been experimentally identified and numerically analyzed.