六自由度弧焊机器人的运动可靠性分析

Although a few studies have analyzed repeatability,accuracy,errors and safety of robot,little attention has been paid to the stochastic approach with open-loop mechanisms,especially robot manipulators.Considering the random nature of dimensional tolerance and clearance in manufacturing and assembling operations,a stochastic approach to figure out reliability of the robot should be required.In this paper,reliability is used to reflect the ability of 6-DOF arc welding robot in completing tasks safely and accurately.With the assumption that all kinematic parameters are independent random variables following normal distribution,the kinematic accuracy error model and reliability model are presented based on the Denavt-Hartenberg(D-H) representation and error propagation theory.     

手机信号采集与传输技术设计与实现

嵌入式平台上,3G手机的信号采集和传输由于数据速率过高,在实现上存在较大的难度,设计了一种由射频芯片、FPGA和CY7C68013构成的手机信号采集和传输方案.以TD-SCDMA信号为例,设计了系统的硬件架构和软件部分,包括FPGA中的软件及USB固件程序.最后提出验证方案,结果表明,该方案能使高达102.4 Mbit/s的TD-SCDMA数据流实现准确无误的采集和传输.     

MoDTP与MoDTC的合成与复配

叙述了ＭｏＤＴＰ、ＭｏＤＴＣ的合成方法以及它们与ＺＤＴＰ等的复配物。     

现代电子与信息技术发展与展望

现代电子与信息技术对国民经济的发展正在起着越来越重要的作用,本文介绍了现代电子与信息技术发展态势,并对现代电子信息技术的发展趋势进行了简要的阐述.     

环境法与民法的互动与发展

环境法是在对传统法理的反思与突破的基础上产生的新型部门法,它以鲜明的生态观和生态本位的立法理念,掀起了法律发展进程中的生态化运动,也对民法的发展产生了深远的影响,在臼益严重的环境问题面前,民法面临发展的困境和变革的压力.环境法与民法的互动与发展成为时代的必然.民法为环境法的产生与发展提供成熟的理论基础、制度渊源和分析工具,环境法为民法注入生态化的理念和发展动力,为民法指明了变革的方向.     

WDPT与ADPT的接种反应与分析

接种吸附百白破混合制剂(WDPT)后出现的发热、红肿、硬结等接种反应给患儿带来了很大痛苦，已成为影响接种率的重要因素。为降低百白破疫苗接种反应，保证接种质量，近几年我们逐步推广使用了吸附无细胞百白破疫苗(ADPT)，取得了良好的效果。对接种WDPT与ADPT的每例接种反应分别进行了观察分析。现将结果报告如下：     

受众心理与新媒体的教育与引导

通过探讨受众的注意、认知和态度层面的效果以及行为层面的效果,新媒体在报道中,应该讲究教育与引导的艺术,在了解受众心理的基础上加以有效教育与引导,才能更好地发挥作用.     

武钢电网继电保护与自动装置运行与分析

在统计数据的基础上,对武钢电网2004年继电保护运行情况做了比较和分析。着重说明了成绩的取得与“继电保护年”所做的各项工作密不可分,指出了武钢电网继电保护存在的问题,并提出了改进建议。     

接地与接零的理论与应用

在电力系统中,接地和接零是否合理,不仅影响电力系统的正常运行,而且还关系到人身安全.本文结合接地保护和接零保护的理论,分析了保护接地和保护接零的作用、应用范围及其在实践中的应用和注意事项.     

情感与英语教学

阐述了情感对英语教学的作用和目前英语教学的现状,就如何在英语教学中注重情感培养,促进英语教学质量的提高进行了探讨.     

Analysis and modeling of the strength, life and reliability of an automobile component

The elasto-plastie stress/strain behavior of an automobile rear axle was analyzed by three-dimension finite element method. Based on the stress in critical area where fatigue crack appears, the fatigue life of the welded structure was predicted using the critical shear stress plane criterion. To improve the fatigue property of the rear-axle, the welding-seam was strengthened by both pellet spraying and plasma melting, and evident improvement was experimentally illustrated. Based on the viewpoint that a complex component is also a system in the respect of reliability assessment and statistical dependence among component failures （ i. e. the so call ＂common cause failure＂） is inherent for system under stochastic load environment, a system-level load-strength interference model was presented and the reliability of the rear axle was estimated as a system, instead of a component.     

半轴断裂原因分析

采用原子发射光谱仪、光学电子显微镜等对某汽车半轴的断裂失效原因进行了分析。结果表明:半轴断裂是由于在半轴的基体显微组织中存在有大量的网状铁素体、沿晶界和晶内存在针状魏氏体、奥氏体晶粒粗大且大小不均匀、超尺寸非金属夹杂物等缺陷,轴颈部的过渡圆角小,在交变应力作用下产生的疲劳断裂。改进轴的设计和热处理工艺,可防止半轴发生断裂     

Life assessment for creep and fatigue of steam turbine components

Improvement of life assessment technologies for power plant materials and components is important in order to meet demands for economy and reliability. As for steam turbines, blade root and disc joints are one of the critical parts in turbines that experience the most severe creep and fatigue damage under high temperature or corrosive environment. In these parts, the structural stress concentration areas are close to the contact planes of blades and rotors, and this produces a complicated stress-strain field. Therefore, life assessment technologies based on precise stress analysis methods and damage mechanisms are necessary to ensure the reliability and economy of steam turbines. In this paper, creep and fatigue tests results by using component specimens simulating blade and rotor joint portions are described. Damage mechanisms of joint portions were investigated based on the observations of the micro-crack initiation and growth behaviors. Life assessment methodologies for joint structures are also discussed, based on the micro-damage, micro-crack or micro-cavity, and nonlinear finite element analyses of component specimens.     

钢轨表面疲劳裂纹扩展机制

 针对轮轨接触疲劳问题,基于Hertz接触理论与库伦摩擦定律,建立含表面裂纹的轮轨接触疲劳计算模型,并对加载位置、轴重、摩擦因数等因素对裂纹扩展速率的影响进行研究。结果表明,轮轨滚动接触的表面裂纹为I-II型裂纹,且以II型扩展为主,其最容易发生断裂的位置在接触斑边缘。轴重和摩擦力是影响轮轨接触疲劳的两个重要因素;随着轴重的增加,应力强度因子[KI、][KII]均呈增加趋势,20 t相对于10 t分别增加359%和185%;随着摩擦因数的增加,应力强度因子[KI、][KII]均呈增加趋势,0.3的摩擦因数相对于无摩擦分别增加了108.7%和119.3%,表明摩擦力的存在明显加剧了裂纹扩展速率。在钢轨涂油养护时,应优先选用固体润滑剂。     

Dynamic Response and Fatigue of Steel Tied-Arch Bridge

The Toutle River Bridge is a steel tied-arch bridge, one that vibrates extensively and has sustained significant fatigue cracking. An experimental study into the cause of this behavior is described. Computer analyses of the bridge behavior are used to estimate the expected response and to establish appropriate locations for instrumentation. The instruments were installed and field tests were performed. Controlled tests were performed with trucks of known axle weight and spacing. Some controlled tests were performed with trucks traveling at known speed and in a specific driving lane with no other traffic on the bridge. Controlled tests were used to calibrate the instrumentation and establish the basic bridge behavior. The results showed that composite action had been lost in the heavily loaded stringers, and little amplification of dynamic response was noted. The measured periods of vibration generally compared well with computer predictions. Uncontrolled truck traffic was then measured for approximately one month. This data was used to establish load spectra and to estimate the fatigue life of critical components. Fatigue, which is caused by calculated stress ranges, should not be important on this bridge for another 20 to 30 years. Existing fatigue damage is driven by distortional fatigue caused by the large bridge deformations. Several options for dealing with the problem are presented.     

Fatigue Reliability of Multidimensional Vibratory Degrading Systems under Random Loading

In this paper, the basic methodology for the fatigue reliability assessment of randomly vibrating multidegree-of-freedom systems is presented within the coupled response-degradation model. The fatigue process in the system components is quantified by the fatigue crack growth equations which—via the stress range—are coupled with the system response. Simultaneously, the system dynamics is affected by fatigue process via its stiffness degradation so that it provides the actual stress values to the fatigue growth equation. In addition to the general coupled response-degradation analysis, its special case of noncoupled fatigue crack growth is treated as well for the wide-band stationary applied stress by the use of its first four spectral moments and the approximate, empirically motivated, Dirlik’s probability distribution for the stress range. Both, the general analysis and the illustrating exemplary problems elaborated in the paper provide the route to the fatigue reliability estimation in complex–hierarchical vibratory systems under random loading.     

60kg级冲压桥壳钢600QK的生产实践和应用

根据汽车桥壳用钢使用特点进行了成分和工艺设计,采用复合微合金化技术在中厚板生产线上生产出60 kg级冲压桥壳专用钢600QK,其力学性能、焊接和冲压性能均满足冲压桥壳的使用要求。疲劳台架试验表明,疲劳寿命均在100万次以上,满足了冲压桥壳轻量化和高疲劳寿命的要求。     

Theoretical Considerations on Corrosion Fatigue Crack Initiation

Based on corrosion kinetics and fracture mechanics, it has been possible to determine quantitatively the corrosion fatigue life for three different types of corrosion behavior. Under general, active corrosion, corrosion fatigue life is controlled by the corrosion rate and the applied alternating stress range. If pitting corrosion occurs, corrosion fatigue life depends on the incubation time for nucleating a pit, the pit growth kinetics, and a critical pit depth, which is a function of the applied stress range. It has been assumed that under passive corrosion conditions, the passive layer has to be penetrated by slip steps, to form corrosion fatigue cracks. The corrosion fatigue crack initiation in this case is controlled by the repassivation kinetics of the material and also by a critical notch depth, depending on the applied stress range. It has been found that a critical current density exists, below which no corrosion fatigue cracks can initiate. Comparison of the theoretically calculated life times with experimental results showed a quite good correlation. M. MüLLER, formerly Research Engineer with Brown Boveri Research Center, Baden, Switzerland.     

压痕对车轴钢疲劳极限的影响

利用硬度计在光滑沙漏状车轴钢疲劳试样上制造压痕,同时利用电火花在试样上加工缺陷,通过疲劳试验研究两种缺陷尺寸与试样疲劳极限之间的关系.将两类试样的测试结果和基于材料硬度、缺陷投影面积的Murakami模型计算结果进行对比.利用扫描电镜观察试样疲劳断口.结果表明,与计算结果相比较,压痕局部塑性变形导致的加工硬化和残余应力对试样的疲劳强度没有影响,裂纹依然从应力集中最大的压痕底部起裂.电火花缺陷表面粗糙度较大引起二次缺口效应,表面硬脆的重铸白层上还有微孔和微裂纹存在,导致此类试样疲劳强度低于模型计算结果,裂纹从电火花缺口底部多处萌生.      

A probabilistic approach to evaluate creep and fatigue damage in critical components

The subject of reliability assessment of plant components is of considerable importance to maintenance and operations engineers. There exist different degradation mechanisms such as creep and fatigue in the plant components operating under conditions of high pressure and temperature. Hence, the safety issue of these components must be addressed by a realistic reliability model so that the frequency of in-service inspection activities can be optimized. In this work, a probabilistic module based on first order reliability method and Markov model is used in order to calculate different failure state probabilities of an in-service thermal power plant pipe-bend. This procedure helps in online risk assessment of critical plant components. The method of determination partial safety factors of the above component for optimum design based on a target reliability level is also discussed.