Priority scheduling policies for repair shops

The use of repair as an alternative to the replacement of products is a growing trend in many industries, especially those employing expensive assets. Repair shop environments are characterized by a greater degree of uncertainty than traditional job or assembly shop environments, and this introduces unique managerial complications. In this study, scheduling policies are examined in the repair shop environment where no end-item spares are available or where the spares stocking decision is deferred until the minimum obtainable flowtimes for enditems are established. Previous studies of scheduling policies have focused on the case where spares are allowed and have not considered all of the sources of variation in the repair environment. The model developed in this study incorporates these sources of uncertainty, as well as other factors likely to influence repair shop performance. The results show that the variability in repair shops is sufficiently higher than in traditional job or assembly shops to warrant different scheduling policies than those previously reported. The choice of scheduling policy to provide minimum flowtimes and RMS tardiness is operating-environment specific, and clear guidelines are presented for the manager in a repair shop environment.     

Modeling of Estimates of the Residual Life of Test Instruments and Radioelectronic Apparatus

Methods of determining point estimates of the residual life of test techniques and radioelectronic components are analyzed. Problems of constructing calculable group and individual models of typical components in order to predict their residual life are considered.     

Special Features of the Thermophysical Modeling of Instrument Cubicles of Spacecraft

Mathematical models which allow for the main mechanisms of heat transfer in instrument cubicles of modern spacecraft are presented. Results of numerical modeling of thermophysical processes in a typical module of the instrument cubicle of a communications spacecraft are given. On the basis of an analysis of multidimensional temperature fields we have drawn conclusions on the presence of substantial nonuniformity in the distribution of the temperature field in devices of radioelectronic spaceborne equipment.     

Spares Provisioning for Repairable Items: Cyclic Queues in Light Traffic

The classic machine repair problem is extended and modeled as a cyclic queue for the purpose of determining the number of spares and repair channels for a population of items subject to stochastic failure. In this system the operating units, removal of failed units, transportation to repair depot, and the repair itself are treated as four multi-server stations, each with exponential holding times. An exact model is developed from the literature on networks and cyclic queues and compared with a series approximation. Under a constraint requiring a high availability of spares which insures “light traffic queues,” the approximate model is found to be very accurate and computationally more efficient.     

批量独立可修件的备件需求预测仿真算法

利用Monte Carlo随机仿真技术，采用事件调度法的仿真策略对可修件的使用与维修过程进行仿真，给出了在给定备件和维修分队数量下批量独立可修件的备件保障概率仿真算法，并用一系列计算实倒证明了算法的可行性和正确性，该算法能有效解决安装在不同装备上，具有不同已工作时间、不同故障间隔时间分布、不同修复时间分布的可修件的备件保障概率计算问题，为备件的科学储备提供7有力的决策依据。     

On the availability of a k-out-of-N system given limited spares and repair capacity under a condition based maintenance strategy

This paper considers a k-out-of-N system with identical, repairable components. Maintenance is initiated when the number of failed components exceeds some critical level. After a possible set-up time, all failed components are replaced by spares. A multi-server repair shop repairs the failed components. The system availability depends on the spare part stock level, the maintenance policy and the repair capacity. We present a mathematical model supporting the trade-off between these three parameters. We present both an exact and an approximate approach to analyse our model. In some numerical experiments, we provide insight on the impact of repair capacity, number of spares and preventive maintenance policy on the availability.     

Multiple failures in a multi-item spares inventory model

Most inventory models dealing with spare parts assume independent part failures and hence one-at-a-time failure occurrences. In practice, for example when an aircraft engine undergoes repair, there is usually more than one part requiring replacement or repair; we denote this situation as 'multiple failures'. In this paper we represent multiple failures in a continuous, infinite horizon, order-for-order spares replenishment inventory model with cannibalization. We derive exact expressions for the distribution function and the expectation of the number of backlogged jobs; approximations are also provided. The results can be used to optimize spares inventories, to evaluate the effects of correlated failures, and to model the impact of parts commonality.     

Influence of polymer aging on reliability indices of a typical printed-circuit assembly of radioelectronic equipment

Mathematical modeling of nonlinear nonstationary temperature fields of a typical printed-circuit assembly of radioelectronic equipment has been performed in a three-dimensional formulation with account for the convective and radiative heat exchange with the environment. On the basis of the data of the numerical experiment the “aging” (degradation) indices of polymer materials under prolonged thermal action have been determined. It has been established that the reliability of an object modeled with account for the real temperature fields is five times lower compared to the realization of normalized thermal conditions. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 188–191, September–October, 2007.     

Multiobjective spare part allocation by means of genetic algorithms and Monte Carlo simulation

The management of spare parts is a major concern for several industrial organizations, due to the significant amount of resources invested every year for holding spares inventories.In this paper, we explore the possibility of using genetic algorithms for the task of optimizing the number of spare parts required by a multi-component system. To address the question of how many spares should be kept in inventory for each component kind, the analyst is required to define objective functions with respect to which the optimization is sought. In our work we will look at multiple objectives such as, for example, the maximization of system revenues and the minimization of the total spares volume. The modeling of the system failure, repair and replacement stochastic processes is done by means of Monte Carlo simulation, whose flexibility allows a closer adherence to reality.     

Software packages for determining the dynamic characteristic of printed components in radio-electronic apparatus

The use of numerical modeling for solving the problem of analyzing the dynamic characteristics of the printed components of radio-electronic apparatus is considered. A method is proposed for constructing models for the numerical solution of various problems based on the method of finite differences. Software packages are described and examples of the solution of problems of investigating the dynamics of printed circuits of radioelectronic apparatus on a computer are given.Translated from Izmeritel'naya Tekhnika, No. 5, pp. 57–60, May, 1994.     

考虑维修时间和惩罚的租赁设备维护策略研究

针对租赁设备维修时间的不确定性,建立考虑维修时间随机性的等周期预防性维护策略。该策略在考虑租赁设备维修时间随机性的同时,综合考虑对出租方的维修惩罚,包括维修时间惩罚、故障总次数惩罚以及可用度惩罚等因素对总成本的影响。从出租方的角度出发,建立以出租方总成本最小为目标的预防性维护策略优化模型。用MATLAB仿真求解出模型的最优预防性维护计划。算例分析表明,考虑租赁设备维修时间随机性和维修惩罚使租赁设备的维护更符合实际情况,能为租赁企业提供有效的设备维护策略。     

A Closed Queueing Network Model for Multi-Echelon Repairable Item Provisioning

A model of a two-echelon (two levels of repair, one level of supply) repairable-item provisioning system is presented. It is desired to find the capacities of the base and depot repair facilities as well as the spares level which together guarantee a specified system service level at minimum cost. Closed queueing network theory is used to model the stochastic process, and an implicit enumeration algorithm is used to solve the optimization problem.     

Diagnostics of Integrated Operational Amplifiers Mounted on Circuit Boards

Methods of estimating the soundness of operational amplifier microcircuits mounted on the circuit boards of radioelectronic apparatus are described. It is shown that it is possible to measure the gain independently of the components connected on the board with the amplifier.     

A Location-Allocation Model for a Two-Echelon Repair-Inventory System

In this paper a model is developed for determining physical location of a repair and stockage facility at the first echelon together with optimal allocation of recoverable spares to each location in a two-echelon repair-inventory system to minimize the total expected system cost. An illustrative example is included to indicate the application of the model and the iterative methodology developed.     

兼职辅助业务的冷贮备机器维修模型

 研究了多修理工同时兼职辅助业务的冷贮备机器维修模型,将其视为多服务台休假有限源排队,利用拟生灭过程方法,给出稳态下机器故障数的分布和等待维修时间的分布,并且指出了模型在某些情况下退化成几个特殊的机器维修模型,同时给出了它们的稳态分布．     

Simulation of the thermal conditions of radioelectronic devices using averaging methods

A possible realization of the system approach to the simulation of thermal fields in cassette radioelectronic devices is discussed, taking account of the multiscaling of their hierarchical structure by the successive application of averaging methods.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 4, pp. 682–688, October, 1990.     

Optimal Provisioning for Single-Echelon Repairable Item Inventory Control in a Time-Varying Environment

This paper presents an algorithm to find a least-cost mix of spares and repair channels, satisfying minimum performance measures, in a single-echelon repairable item inventory system. The monotonicity of the performance measures is the basis for using implicit enumeration in the optimization algorithm. The system analyzed is in a transient environment and is modeled as a birthdeath process with finite state space. The system's transition rates are allowed to vary over time. Transient probabilities are computed using randomization. Illustrative examples are presented.     

军械应急备件箱的设计

目的为满足当前军械应急维修保障需要,提升部队战斗力,研制一种新型的军械应急备件箱。方法通过部队调研得出军械应急备件箱的基本设计要求,运用机械原理和电子技术,重点从结构、功能和材料方面考虑,设计军械应急备件箱的技术方案。结果针对新研制的军械应急备件箱,分别进行了携运行能力、备件取用测试,测试结果表明军械应急备件箱携运行能力和备件取用便捷性均优于现有的备件箱。军械应急备件箱全箱采用了全封闭式结构,并分别在5,7,9,11 mm/min的降雨强度下进行了防水测试,均能保证备件盒内不渗水,说明该箱完全适用于在全天候条件下使用。结论经过试用认为,军械应急备件箱的研制弥补了现行部队军械维修时备件供应不精准且不便携行的缺陷,构建了合理的军械维修体系。     

Reliability of an Independent Component,s-Spare System with Exponential Life Times and General Repair Times

In this paper, the reliability of a system with N independent components supplied with a pool of s spares is investigated. The components have an exponential life time distribution and the failed components are repaired, one at a time, with a general repair time distribution. Numerical results are presented for the mean time to system failure (system is said to fail when a component fails with no spare available) and the reliability of the system in some special cases of interest.     

Performability of FMS based on stochastic process models

We address the design for reliability of complex systems, such as Flexible Manufacturing Systems (FMS), through mathematical modelling of the machine failure, spares inventory, and repair processes. The unique model allows separation of systems by Machine Part Type (MPT); thus, we can model an extremely complicated FMS through many simpler models. Our measure of system effectiveness is based on a performability measure that credits partial availability by the performance of the system in that state. By comparing performability measures, designers and managers can affect the system reliability. Examples demonstrate how to use these developments.