A multi-objective approach to facility layout problem by genetic search algorithm and Electre method

Tool Failure in Sequential Cutting of two Different Materials

In this paper the authors show that the premature tool breakage, characteristic of interrupted cutting, can be enhanced in sequential cutting of two materials having different mechanical and chemical properties. The results of experimental investigations carried out in turning pieces consisting of medium carbon steel and aluminium alloy show that the time to failure is significatively lower than that occurring in machining only one of the two materials; moreover the morphology of the damage depends by the cutting order. Working with the sequence steel-Al alloy welding phenomena caused by strong deoxidation due to the latter material are observed; these phenomena cause the early development …

Maintenance Planning For The Reliability Maximization In A Large System With Vagueness In The Reliability Values Of Some Components

This paper tackles the problem to single out the maintenance actions to be executed on a production system during the planned stop of given length. In detail, from a reliability viewpoint the system is assimilated as a series-parallel multi-component system and the maintenance actions need to maximize the system reliability up to the next planned stop. Moreover, it is assumed that some components reliability values are affected by vagueness within a given range. To solve the considered problem, an exact dynamic programming algorithm suitable to quickly point out the maintenance scheduling is developed and, moreover, it is formulated a proper parameter able to express the robustness of the o…

The FTOPSIS method to support FMECA analyses

This paper proposes an approach based on multi-criteria decisional methods to manage the results derived from reliability analyses. In detail, this paper proposes ranking the failure modes of a system when analyzed with failure modes, effects and criticality analysis (FMECA) using the technique for order preference by similarity to ideal solutions (TOPSIS). To better manage the uncertainty of evaluations made under the differing criteria, the TOPSIS method is applied in its fuzzy version (FTOPSIS). When the method is applied to a case study, the results highlight the main possible critical faults and supply fundamental information to take into account during the scheduling of maintenance ac…

Multi objective genetic algorithms for unequal area facility layout problems: A survey

The Unequal Area Facility Layout Problem (UA-FLP) comprises a class of extremely difficult and widely applicable optimization problems arising in diverse areas and meeting the requirements for real-world applications. In this paper we present our existing works of the past decade showing the evolutions obtained in the Genetic Algorithms (GA) used to solve the facility layout problem. GA have recently proven their effectiveness in finding (sub) optimal solutions to many NP-Hard problems such as UA-FLP. A main issue in such approach is related to the genetic encoding and to the evolutionary mechanism implemented, which must allow the efficient exploration of a wide solution space, preserving …

A fuzzy parameter to characterize the uncertainty in the plant layout design

The present work aims at proposing a methodology able to return a single parameter that synthesizes the aspects characterizing the layout design problem that the analyst translates into requests of closeness and distance among departments. In order to consider the uncertainty of the problem, closeness and distance requests are expressed by means of fuzzy numbers and a weight fuzzy function modules the importance of the aspects by allowing the analyst to express his/her priorities on the basis of the specific decisional context. The weight function is characterized by the presence of a threshold value that makes the method non compensative. The hypothesis herein assumed is that, when the dis…

A Multi-Criteria Group Decision To Support The Maintenance Service: A Case Study

The present paper wants to propose a methodology to support a group of decision makers into the choice of actions, to implement on a multi-component system, regarding the maintenance service. The choice has to be made on the basis of several criteria, namely the total maintenance cost, the system unavailability and by considering the maintenance actions feasibility. In particular, with the aim to select the maintenance service that represents for the group the best comprise among the criteria to satisfy, the proposed methodology consists of two multi-criteria decisions methods to apply in two successive phases. The first one regards the application of the Analytic Hierarchy Process (AHP) to…

Fractal dimension: A useful tool to describe the microgeometry of machined surfaces

Abstract The authors have utilized some concepts of fractal geometry to describe the complexity of profiles surveyed from surfaces worked by cutting. In particular an experimental analysis was carried out to investigate the influence of the worked material, cutting speed and cutting operation on the “fractal dimension” parameter. The obtained results show that this parameter is able to describe the irregularities of the profile on a small scale, which is important for an overall understanding of the functional behaviour of machined surfaces. Such descriptions cannot be derived from the more commonly employed parameters.

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An effective approach for the maintenance scheduling in large systems with required reliability level: A case study

This paper deals with the problem of the maintenance scheduling in a multi-component system for which a required reliability level has to be warranted until the next planned stop for maintenance. Particularly, the tackled problem concerns both the determination of the elements set on which to perform preventive maintenance and the optimal number of maintenance crews in order to warranty the required reliability level at the minimum maintenance cost. The problem is formulated as a mathematical programming model that becomes very hard to solve for large practical systems. For such reason, a new effective approach based on a constrained genetic algorithm is herein proposed and tested with refe…

A multi-decision makers approach to select the maintenance plan for a multi-component system.