Vladimir Popović

Optimisation of maintenance concept choice using risk-decision factor – a case study

The design of maintenance system and the corresponding logistic support is a very complex process, during which the aim is to find the compromise solutions regarding the relations among different maintenance procedures and the ways of their implementation. As a result of this, various solutions can be adopted, since this is conditioned by a series of important factors and criteria, which can be contradictory sometimes. There are different perspectives on ways of solving practical maintenance problems, that is dilemmas when it comes to the choice of maintenance concept. The principal dilemma is how and when to decide on carrying out maintenance procedures. Should the decision be based on theoretical grounds or experience, how does one reconcile those two extremes, who is to decide upon this? In this article we have offered one, basically new solution as a possibility for maintenance concept choice, based on a significant modification of the widely used failure modes and effects analysis (FMEA) method. This solution is risk-decision factor (RDF). This is a result of seven parameters (of different importance and weight) that have the key impact on the process of production and logistic support. The application of this factor is illustrated by the example of planning, organisation and functioning of the maintenance system applied in The Institute for Manufacturing Banknotes and Coins (ZIN) in Belgrade.

Application Of New Decision Making Model Based On Modified Cost-Benefit Analysis — A Case Study: Belgrade Tramway Transit

Tramway transit has an important place within the public transportation system of Belgrade. However, due to the very unfavorable age structure, the bad condition of tramway tracks and infrastructure, as well as the maintenance system that require significant advancement, Belgrade tramways are in very bad repair, so the transport requirements are not properly met. The principal task of the analysis presented in this paper is to recognize and estimate the justifiability of investment into various solutions for revitalization of Belgrade tramway rolling stock. We have chosen a somewhat different from usual approach to decision making, that is, applied a combination of cost-benefit, life-cycle cost and multi-criteria analysis.

Warranty optimisation based on the prediction of costs to the manufacturer using neural network model and Monte Carlo simulation

Warranty is a powerful marketing tool, but it always involves additional costs to the manufacturer. In order to reduce these costs and make use of warrantys marketing potential, the manufacturer needs to master the techniques for warranty cost prediction according to the reliability characteristics of the product. In this paper a combination free replacement and pro rata warranty policy is analysed as warranty model for one type of light bulbs. Since operating conditions have a great impact on product reliability, they need to be considered in such analysis. A neural network model is used to predict light bulb reliability characteristics based on the data from the tests of light bulbs in various operating conditions. Compared with a linear regression model used in the literature for similar tasks, the neural network model proved to be a more accurate method for such prediction. Reliability parameters obtained in this way are later used in Monte Carlo simulation for the prediction of times to failure needed for warranty cost calculation. The results of the analysis make possible for the manufacturer to choose the optimal warranty policy based on expected product operating conditions. In such a way, the manufacturer can lower the costs and increase the profit.

Defining the functional and physical compatibility of a modernized tramway rolling stock with a newly planned LRT system: a case study of Belgrade

According to the Belgrade Master Plan for 2021, the public transportation system for the city and its region will include three rail modes: a modernized existing tramway, regional rail, and a new light rail transit (LRT) mode. In the coming years all three rail modes should be developed simultaneously and in a coordinated manner. The introduction of LRT is to be realized in several phases, and its first line will partially follow the alignment of an existing tramway line. As the present tramway vehicles are obsolete, new rolling stock must be designed and purchased to be compatible with many of the elements of the LRT. Ways to adjust the new tramways to the LRT rolling stock represent the central topic of this paper. The basic technical and operating characteristics of the new tramway are defined with respect to their required compatibility with the LRT stock and infrastructure.

Choosing the Right Warranty Policy - from the Customer's to the Manufacturer's Point of View

Product warranty is a powerful marketing tool, but it always involves additional costs to the manufacturer. This paper deals with the warranty cost analysis for one type of passenger car batteries. Costs were calculated for three variants of fully renewing combination free replacement and pro-rata policy and for different warranty parameters. After choosing the price range for the product, a market research was performed to determine which warranty policy customers recognize as most favourable to them. Obtained results are guideline for the manufacturer to choose the warranty that minimizes the costs and maximizes the profit.

Analysis of Comfort Parameters in Special Purpose Vehicles from Technological Development Point of View

The analysis of comfort parameters in the crew cabin space of two variants of the special purpose off-road vehicle is presented, taking technological development aspects into account. Tests of noise, vibration and heating – cooling efficiency have been performed in realistic operating conditions, during the intensive driving on three selected test tracks, in order to ensure the repeatability of the obtained results. Measuring of noise and vibration levels at the drivers, co-drivers and crew members’ seats were performed at strictly defined vehicle speed. Heating efficiency tests for the cabin have been performed in laboratory conditions, inside a cold chamber with the constant temperature of (−16 °C), whereas cooling efficiency tests were conducted in the hot chamber at the temperature of (+40 °C). The results of these tests enable the selection of a more comfortable variant of vehicle, wherein the one with less seats for passengers in the cabin which, in addition to more comfort also has the advantage of greater storage space, and from the application flexibility standpoint, which is offered by the possibility of transporting more passengers and less load, such vehicles offer better environment control from within the vehicle.