浅论现场总线通信故障的处理技术

应用现场总线技术的现场总线控制系统(FCS)已成为工业自动化领域发展的热点和趋势,其通信故障却一直是影响FCS可靠运行的瓶颈.文章结合宝钢三期某FCS系统的通信故障实例,深入探讨了典型故障的现象、原因和处理技术,以期为FCS系统的通信故障处理提供借鉴与参考.     

用于铁道牵引供电系统故障诊断的数据仓库挖掘技术

利用Rough Set理论处理不分明关系的能力，提出了数据仓库挖掘的原理和方法，并对大量的实时与仿真数据集进行了约简，挖掘出系统参数值与各类故障之间的相互关系，抽取其隐含的关联规则，对实现铁道牵引供电系统性能状态的实时自动监测和故障诊断具有重要的参考价值。     

Wedge simulation method for calculating the reliability of linear dynamical systems

In this paper the problem of calculating the probability of failure of linear dynamical systems subjected to random excitations is considered. The failure probability can be described as a union of failure events each of which is described by a linear limit state function. While the failure probability due to a union of non-interacting limit state functions can be evaluated without difficulty, the interaction among the limit state functions makes the calculation of the failure probability a difficult and challenging task. A novel robust reliability methodology, referred to as Wedge-Simulation-Method, is proposed to calculate the probability that the response of a linear system subjected to Gaussian random excitation exceeds specified target thresholds. A numerical example is given to demonstrate the efficiency of the proposed method which is found to be enormously more efficient than Monte Carlo Simulations.     

On changing points of mean residual life and failure rate function for some generalized Weibull distributions

The failure rate function and mean residual life function are two important characteristics in reliability analysis. Although many papers have studied distributions with bathtub-shaped failure rate and their properties, few have focused on the underlying associations between the mean residual life and failure rate function of these distributions, especially with respect to their changing points. It is known that the change point for mean residual life can be much earlier than that of failure rate function. In fact, the failure rate function should be flat for a long period of time for a distribution to be useful in practice. When the difference between the change points is large, the flat portion tends to be longer. This paper investigates the change points and focuses on the difference of the changing points. The exponentiated Weibull, a modified Weibull, and an extended Weibull distribution, all with bathtub-shaped failure rate function will be used. Some other issues related to the flatness of the bathtub curve are discussed.     

φ28mm光杆断裂失效分析

28mm光杆使用78天后断裂。通过对断裂光杆的设计强度校核,断口的宏观形貌分析、材质及显微组织的检验,认为,由于光杆未按要求进行热处理,导致出现非正常显微组织,降低了零件的疲劳性能,加上光杆表面有损伤造成的应力集中,因此在使用后不久便发生断裂失效。     

Quasi-static crushing behaviour of hybrid and non-hybrid natural fibre composite solid cones

A comprehensive experimental investigation of the quasi-static axial crushing of hybrid and non-hybrid natural fibre/polyester composite solid cones between flat platens has been carried out. The composite solid cones were fabricated from two types of natural fibres namely oil palm fibre and coir fibre and different vertex angles varied from 0° to 60°. Typical load-deformation histories are presented and discussed. Crashworthiness parameters such as load carrying capacity; energy absorption capability and failure mechanism have been discussed. The results presented in this study will help us to understand the behaviour and characteristics of natural fibre composite as a filler material.     

Timed Behavior Trees for Failure Mode and Effects Analysis of time-critical systems

Behavior Trees are a graphical notation used for formalising functional requirements, and have been successfully applied to several industrial case studies. However, the standard notation does not support the concept of time, and consequently its application is limited to non-real-time systems. To overcome this limitation we extend the notation to timed Behavior Trees. We provide an operational semantics which is based on timed automata, and thus serves as a formal basis for the translation of timed Behavior Trees into the input notation of the timed model checker UPPAAL. System-level timing properties of a Behavior Tree model can then be automatically verified using UPPAAL. Based on the notational extensions with model checking support, we introduce timed Failure Mode and Effects Analysis, a process for identifying cause-consequence relationships between component failures and system hazards in real-time safety critical systems.     

电磁流量计在污水处理厂的应用

介绍了电磁流量计的工作原理及特点,对流量计在应用过程中出现的一系列问题进行了分析,即传感器选型、安装位置选择、投运、故障等,并提出了相应的解决方案。电磁流量计自2008年5月投入使用以来,效果显著。     

Dynamic properties of concrete in direct tension

An experimental study on the strain-rate dependent behavior of concrete in tension was carried out by means of a servo-hydraulic testing machine. The specimens were made in dumbbell shape and the tested strain rate ranged from 10^− 5/s to 10^− 0.3/s. Strain-rate effects on the tensile strength, the modulus of elasticity, the critical strain, the Poisson's ratio and the energy absorption capacity of concrete were studied. More emphasis was placed on the influence of temperature and moisture content on the strain-rate sensitivity. All test data were analyzed, discussed and compared with available reference materials. In addition, strain-rate effects on the damage pattern of specimens were studied. It was observed that the fractured surfaces of the specimens became more and more flattened and a number of coarse aggregates were broken along the failure surfaces. Based on this phenomenon an explanation to the physical mechanisms of strain-rate enhancement during rapid loading was proposed.     

Effect of branch frequency on dynamic fatigue behavior of slowly notched polyethylene polymers

Samples with the same weight average molecular weight and molecular weight distribution but different branch frequency were utilized to study the effects of branch frequency and thermal history on tie molecule density and their subsequent influence on the slow crack growth of short chain branched polyethylenes. The dynamic fatigue properties are improved significantly with increasing branch frequency and with samples crystalloid at fast cooling rate. However, at temperatures ranging from -20 to 80 °C. the amount of the failure cycle (Nf) improved due to the slight increase in branch frequency is less than those of samples prepared by crystallization at fast cooling rate. Additionally, it is interesting to note that the drawn fibers observed on the fracture surfaces were larger and longer for samples associated with longer Nf. In fact, it is interesting to note that the average number of tie molecules formed per chain (T(M)) of samples associated with longer Nt is also larger. This increasing in T(M) is suggested to be responsible for the improved fatigue properties of samples associated with larger branch frequency and crystallized at fast cooling rate.