Case Study of an Aerosol Explosion and a Method to Determine Explosion Temperatures

A failure analysis case study is presented for a two-piece aerosol containing tetrafluoroethane, commonly referred to as Refrigerant 134a. A gentleman was preparing to recharge the air conditioning system of an automobile when the bottom exploded off the aerosol container, propelling the body of the aerosol container like a rocket, which hit the man in the eye and blinded him in that eye. The aerosol was never connected to the air conditioner, therefore backpressure from the air conditioner (AC) compressor was ruled out as a cause for the explosion. The objective of the study was to determine why the aerosol exploded. Several recently developed test methods were used, including two types of heat-to-burst tests and a puncture chamber to measure the pressure-versus-temperature behavior of aerosols. More common test methods were also used, such as water bath pressure tests, hydro pressure burst tests, pneumatic pressure burst tests, hardness measurements, weight measurements, metallography, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and an accident scenario recreation. A semi-empirical correlation between the hardness and weights of the container bottoms was used to determine the explosion temperature and/or pressure. This semi-empirical correlation agrees in principle with an analysis of the explosion pressures using finite-element analysis (FEA). The root cause for the explosion was determined to be a lack of strength of the bottom of the two-piece aerosol coupled with heating the aerosol to temperatures significantly above room temperature.     

山西引黄工程南干线7# 隧洞衬砌外水压力研究

本文采用综合修正系数取代规范建议的单一折减系数,用渗流场分析方法确定作用在引黄入晋南干线7#隧洞衬砌上的外水压力。由己知钻孔水位及泉水位反演出各地层的渗透张量及地表入渗强度求得初始渗流场。衬砌外水压力分析中考虑了衬砌混凝土的渗透性以及排水、灌浆等工程措施的影响。根据分析结果,提出了系统排水孔布置的建议,得出了在相应的排水减压措施下衬砌厚度由原设计35cm减至25cm,这一建议已被采用,取得了巨大经济效益。     

BKX-Ⅰ型并联机床的谐响应分析

应用有限元分析软件(ANSYS),对BKXⅠ型并联机床进行谐响应分析,分别得到了机床各节点沿机床的虚拟轴X、Y和Z向的位移谐响应曲线。在此基础上,还分析了该机床的谐响应规律,并明确了谐响应的特点,为改善此类机床的动态特性提供了一定的参考依据。     

有限元仿真分析中的结构周期差异探讨

针对有限元仿真分析中结构自振周期减小的问题，讨论了几种主要的影响因素，并借用商品化设计软件TBSA，ETABS 和有限元分析软件ANSYS，通过对一个简单结构的多次计算，比较了这些因素的影响大小。     

电化学腐蚀法制备微细群圆柱

提出了微细群圆柱结构电化学腐蚀加工法及其形状和尺寸控制方式。根据电化学腐蚀基本原理,通过有限元分析计算群圆柱电化学腐蚀加工过程中的电场分布,优化设计阴极形状。开展了电化学腐蚀法制备微细群圆柱结构的工艺试验,获得了良好的试验结果。     

数控机床主轴部件变形的有限元分析

利用有限元分析方法进行优化设计,在产品设计阶段就能对主轴部件静、动态特性作出符合实际的预测,使数控机床主轴部件实现优化设计,进而提高产品一次设计成功率、缩短产品开发周期,提高数控机床产品的设计水平.     

弹性变形对仿人机器人步态规划的影响分析

仿人机器人行走步态研究的理论、方法及建模均未考虑系统各部件弹性变形的影响，导致行走实验结果与理论步态规划存在较大的差异，制约了步行质量的提高和连续快速稳定步行的实现。本文运用ANSYS有限元软件，针对清华大学研制的THBIP—Ⅰ型仿人机器人样机，建立精确的有限元模型，进行步行运动弹性变形及其对步态规划影响的有限元仿真分析，在此基础上提出了对步态规划进行局部修正完善的方法，步行实验证明该有限元模型及仿真分析结果是有效的。     

Photoelastic Studies on Rubber-to-Rubber Joints

Photoelasticity is a method which yields information on the principal stress difference and orientation in a composite structure. Various problems associated with this technique, especially those concerning the fundamental relationship between the fringe order and the stress, have yet to be investigated. A few studies of this relationship in a universal stress state have been presented, particularly in the field of rubber-to-metal and rubber-to-fabric composites, but no evaluations have so far been made in the field of rubber-to-rubber joints. Applying the photoelastic method, we report our observations on the stress distribution in a natural rubber to natural rubber joint subjected to uniaxial tension. A comparison between the results of experimental photoelastic studies and the corresponding computer modelling has been illustrated. The theoretical displacement pattern of the angular joints of bi-rubber part has also been highlighted.     

MEMS气体流量传感器的简易流量测试装置

为了完成所研制的MEMS气体流量传感器样品的流量测试与标定,设计制作了一种由标准流量发生器和传感器信号读出与数据采集电路组成的简易流量测试装置。标准流量发生器由注射器和可更换的砝码组成,利用不同的砝码配重,在注射器出气口产生合适的恒定气体流速。通过理论分析和Ansys有限元数值仿真,验证了简易标准流量发生器的可行性。传感器信号读出与数据采集电路基于内建多路A/D转换器的单片机实现,具有传感器加热电阻器的恒温控制、流量信号的数字检测和显示的功能。采用该简易流量测试装置对自行研制的MEMS气体流量传感器进行了流量测试与标定,获得了待测器件的标定参数、传感器流量测量的绝对误差和相对误差。     

缠绕管件轴压下径向形变和破坏模式的有限元分析与验证

本文采用缠绕工艺制备厚壁碳/环氧复合材料主承力管件,对所制备管件试样进行轴压破坏试验,并采用有限元分析软件ANSYS7.0对试验过程进行模拟分析.分析结果表明轴压管件径向形变最大的位置在距离管件端面20～25mm处,表明该位置容易发生破坏,与实验结果是一致的.