共查询到19条相似文献,搜索用时 187 毫秒
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基于模糊综合判定的网壳结构强震失效模式研究 总被引:1,自引:0,他引:1
为合理判别单层网壳结构在强震下的两类失效模式,指导网壳工程在地震区的实践,该文采用考虑材料损伤累积的荷载域全程分析方法,对单层球面网壳和单层柱面网壳在动力荷载下(包括强震)的响应进行了系统的参数分析。简述了两类失效模式的结构表现及结构响应特征;引入模糊数学中的模糊综合判定理论,确定了网壳结构多项响应因素与模糊失效模式集合的关系,建立了基于模糊综合判定的网壳结构动力失效模式判别模型;通过分析表明:所建立的模型具有准确的判别效果,可对网壳结构在动力荷载下的失效模式进行判别。 相似文献
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张瑞琴 《中国新技术新产品》2008,(14):115-115
拉弯矫直机主要用于薄带材的矫直,在我国的应用越来越广泛。文章分析了拉弯矫直机组的特点,介绍了某拉弯矫直机组的设备组成及参数,并重点介绍了其电气控制系统。 相似文献
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基于结构破坏的首次穿越模型,应用随机结构分析概率摄动法确定系统响应及系统不同失效模式之间动态相关性.数值算例表明,随机非线性系统不同位移之间、位移与速度之间均存在相关性;系统不同失效模式间同样具有相关性,并且在考察的大部分状态下,这种相关性具有动态、强相关等特点,相关失效是系统失效的主要模式.数值算例中计算结果应用Monte Carlo随机模拟方法进行验证均较好吻合,表明了该方法是能够满足工程计算要求的,从而为非线性随机振动系统不同失效模式间动态相关系数的确定提供方法参考. 相似文献
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将QSIM定性模拟方法与Petri网集成用于描述管理人员素质变化过程,采用概率统计的方法处理模拟结果以提高管理人员任职资格确定的准确程度.将企业管理者的素质划分为成就动机、领导能力、人际关系能力、专业职务能力四类,设计了企业管理人员素质变化过程的PETRI网模型,规定了变量知识的表示方法和网络变迁推理规则;设计了基于素质改变成本的网络知识状态转移过滤规则,以防止定性模拟过程中的组合爆炸;设计了管理人员素质确定的概率统计处理方法,并给出了一个应用示例说明其应用过程. 相似文献
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预应力CFRP 加固混凝土结构技术因其在材料性能利用方面的优越性能已成为CFRP 加固的热点方向,其中预应力CFRP 加固结构的可靠性是这一方向研究的重要内容。该文分析了影响预应力CFRP 板加固钢筋混凝土受弯构件承载力的主要变量的概率特征,考虑CFRP 板尺寸效应和应力分布的影响,采用Weibull 分布推导了CFRP 板的极限强度概率分布函数,根据预应力CFRP 张拉工艺,分析了预应力损失随机变量,建立了在不同失效模式(破坏形态)下的受弯构件抗力概率模型,并开展了参数敏感性分析,获得各个失效模式下抗力概率模型的主要影响因素。研究结果表明:抗力概率模型是预应力CFRP 加固结构的失效概率计算与可靠度校准的重要内容之一,各参数的影响规律与各失效模式的破坏形式密切相关。 相似文献
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该文定义了构件的截面损伤指标,基于增量动力分析(IDA)方法,对地震输入下结构的失效模式进行分类,进一步统计得出各失效模式下构件端部截面损伤均值。提出基于概率的地震失效模式识别方法,建立各失效模式下结构失效概率关系表达式。基于OpenSees平台,对一个20层benchmark钢框架结构模型进行数值分析,结果表明,根据关键层的损伤状态可以合理地划分失效模式,引入构件重要性系数能较好地反映各构件截面损伤对结构失效模式的影响,基于概率的地震失效模式识别方法能有效的判别结构发生各失效模式的概率大小。 相似文献
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S. K. Yang 《Quality and Reliability Engineering International》2004,20(8):761-776
This paper describes the application of Petri nets to remote diagnosis for failures of cardiac pacemakers. The operations, structures and basic control methods of the different types of cardiac pacemakers are first described. A combined synchronous pacemaker is modeled into a Petri net in this study. Twelve checkpoints are added into the modeled Petri net so as to construct a Petri net for failure diagnosis. A remote mode for failure diagnosis of implanted pacemakers is also designed by the Petri net approach. A low‐power transmitter transmits a checking‐code with 12 digits from the implanted pacemaker to the outside of the patient's body manually or automatically. By observing the markings of the checking code, the working status and the health condition of the pacemaker are clear at a glance. Applications of the Petri net method for failure diagnosis and control optimization are discussed. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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The aim of this paper is to describe a method to integrate the results of process simulations in availability studies. It is shown that this can be achieved if two conditions are met: firstly, close co-operation between process experts and reliability engineers and secondly, a flexible modelling tool. Principles of the modelling method, the interpreted stochastic Petri nets, are provided. The way to use them to model plant availability is described, together with a computer code enabling calculations to be made. The aim of the plant availability study and how results of process simulations were integrated in the Petri net model is then explained. Results are discussed and conclusions given on the ability of interpreted stochastic Petri nets to model complex systems. 相似文献
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This paper combines universal moment generating function technique with stochastic Petri nets to solve the redundancy optimization problem for multi-state systems under repair policies. Redundant elements are included in order to achieve a desirable level of production availability. The elements of the system are characterized by their cost, performance and availability. These elements are chosen from a list of products available on the market. The number of repair teams is less than the number of reparable elements, and a repair policy specifies the maintenance priorities between the system elements. A heuristic is proposed to determine the minimal cost system configuration under availability constraints. This heuristic, first applies universal moment generating function technique to evaluate the system availability, assuming unlimited maintenance resources. Once a preliminary solution is found by the optimization algorithm, stochastic Petri nets are used to model different repair policies, and to find the best system configuration (architecture and number of repairmen) in terms of global performance (availability and cost). This combined procedure is applied to a reference example. 相似文献
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This paper presents an analytical approach for the evaluation of multi‐user safety critical systems presenting a failure delayed behavior pattern. As a consequence of a failure event, the performance of these systems worsens progressively due to the internal fault tolerance mechanisms or the complacency of the users regarding the temporary unavailability of the services. A distinctive feature of the approach is the ability to handle stochastic models containing multiple processes with generalized distributions. The approach is based on the determination of analytical expressions to measure reliability, for instance, frequency and probability of failure states, which may be evaluated using general purpose mathematical tools. The paper first reviews other well‐established techniques employed in the assessment of non‐Markovian systems, particularly those based on stochastic Petri nets. The rationale of the new approach and its fundamental algorithms are presented together with a set of illustrative examples which highlight the strengths of the approach, as well as its limitations. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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The reliability of a system is the probability that the system will perform its intended mission under given conditions. This
paper provides an overview of the approaches to reliability modelling and identifies their strengths and weaknesses. The models
discussed include structure models, simple stochastic models and decomposable stochastic models. Ignoring time-dependence,
structure models give reliability as a function of the topological structure of the system. Simple stochastic models make
direct use of the properties of underlying stochastic processes, while decomposable models consider more complex systems and
analyse them through subsystems. Petri nets and dataflow graphs facilitate the analysis of complex systems by providing a
convenient framework for reliability analysis. 相似文献
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A methodology is developed which uses Petri nets instead of the fault tree methodology and solves for reliability indices utilising fuzzy Lambda–Tau method. Fuzzy set theory is used for representing the failure rate and repair time instead of the classical (crisp) set theory because fuzzy numbers allow expert opinions, linguistic variables, operating conditions, uncertainty and imprecision in reliability information to be incorporated into the system model. Petri nets are used because unlike the fault tree methodology, the use of Petri nets allows efficient simultaneous generation of minimal cut and path sets. 相似文献
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Although Petri nets have various capabilities, the Petri net approach is done on paper. A field‐programmable gate array (FPGA) is implemented in this study so as to realize basic Petri net symbols, logic structures in Petri nets, and specific functions for Petri nets by logic circuits. As an example, a Petri net for an early failure detection and isolation arrangement (EFDIA) is implemented as an application‐specific integrated circuit (ASIC) on a Xilinx Demonstration Board. This ASIC is verified by three simulations dealing with three different failure scenarios of a system, and the ASIC functions identically to the EFDIA Petri net. Accordingly, not only the EFDIA Petri net but also any specific function Petri nets can be implemented by FPGA circuits. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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Petri nets are a powerful technique widely used in the modeling and analysis of complex manufacturing systems and processes. Due to their capability in modeling the dynamics of the systems, Petri nets have been combined with fault tree analysis techniques to determine the average rate of occurrence of system failures. Current methods in combining Petri nets with fault trees for system failure analysis compute the average rate of occurrence of system failures by tracking the markings of the Petri net models. The limitations of these methods are that tracking the markings of a Petri net represented by a reachability tree can be very complicated as the size of the system grows. Therefore, these methods offer less flexibility in analyzing sequential failures in the system. To overcome the limitations of the current methods in applying Petri nets for system failure assessment, this paper expands and extends the concept of counters used in Petri net simulation to perform the failure and reliability analysis of complex systems. The presented method allows the system failures to be modeled using general Petri nets with inhibitor arcs and loops, which employs fewer variables than existing marking‐based methods and substantially accelerates the computations. It can be applied to real system failure analysis where basic events can have different failure rates. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Petri nets are useful for modelling a variety of asynchronous and concurrent systems, such as automated manufacturing, computer fault tolerant systems, and communication networks. This study employs an airbag inflator system as an example to demonstrate a Petri net approach to failure analysis. This paper uses Petri nets to study minimum cut sets finding, marking transfer, and dynamic behaviour of system failure. For Petri net models incorporating sensors, fault detection and higher-level fault avoidance is dealt with. Compared with fault trees that present only static logic relations between events, Petri nets indeed offer more capabilities in the scope of failure analysis. © 1997 John Wiley & Sons, Ltd. 相似文献