Pierre Dehombreux

• MEng., PhD
• Head of Faculty at University of Mons

The degradation of the cutting tool and its optimal replacement is a major problem in machining given the variability in this degradation even under constant cutting conditions. Therefore, monitoring the degradation of cutting tools is an important part of the process in order to replace the tool at the optimal time and thus reduce operating costs....

In manufacturing, tool wear monitoring is crucial as it directly influences production quality and operating costs. Inaccurate replacement strategies can result in increased costs and substandard parts. Various Artificial Intelligence (AI) methods have been proposed to monitor tool wear using cutting signals, but a comprehensive performance compari...

Optimal replacement of machining cutting tools is a major challenge in today's manufacturing industry. Due to the degradation of the tool during machining, late replacement of the tool leads to the risk of producing parts that do not meet technical specifications, while early replacement increases machine downtime and tool costs. To replace tools a...

In this paper, we develop an adaptation of the LuGre friction model so as to allow the development of the friction force and its application in any directions on systems subjected to varying normal forces. This is achieved by projecting a modified LuGre model adapted to varying normal forces in 3D along an arbitrary orthogonal system. Consequently,...

In turning operations, the wear of cutting tools is inevitable. As workpieces produced with worn tools may fail to meet specifications, the machining industries focus on replacement policies that mitigate the risk of losses due to scrap. Several strategies, from empiric laws to more advanced statistical models, have been proposed in the literature....

Additive manufacturing is feeding great hopes for future developments in fields such as aeronautical, biomedical and rapid tooling industries. However, limitations are still restricting its use to make prototypes and hampering mass production. In the case of titanium alloy printing (e.g. Ti6Al4V) with the EBM (Electron Beam Melting) process, the ma...

The important losses in the machining industry due to improper replacement of cutting inserts induces the necessity of optimizing the maintenance policies in such contexts. However, the variety of industrial practices, end-of-life criteria, and optimization criteria does not allow a clear view on the maintenance policy performance evaluation. The g...

The optimization of the cutting tools replacement is often overlooked, despite the huge losses associated with their improper maintenance. This presentation aims at bringing up to date this particular maintenance action. Register to AMEST20 (https://www.amest2020.eng.cam.ac.uk/) or watch this presentation on YouTube: https://www.youtube.com/watch?v...

Additive manufacturing is feeding great hopes for future developments in fields such as aeronautical, biomedical and rapid tooling industrssssies. However, limitations are still restricting its use to make prototypes and hampering mass production. In the case of titanium alloy printing (e.g. Ti6Al4V) with the EBM (Electron Beam Melting) process, th...

The important portion of machining costs associated with cutting inserts and scraps induces the search for better effectiveness in turning. This paper presents the results of an exploratory study on the influence of tool flank wear on roughness indicators (arithmetic average roughness, root mean square roughness and maximum height of the roughness...

The machining industry raises an ever-growing concern for the significant cost of cutting tools in the production process of mechanical parts, with a focus on the replacement policy of these inserts. While an early maintenance induces lower tool return on investment, scraps and inherent costs stem from late replacement. The framework of this paper...

Cutting tools replacement is an important industrial concern because of the costs that stem from them. In many cases, cutting inserts are replaced either too late or too early. Consequently, either workpieces are scraped or cutting inserts are wasted. That is why there is a need for on-line evaluation of cutting tool wear, hence their residual life...

A high proportion of machined goods production costs are associated with the management of cutting inserts. Early replacement leads to waste of inserts, whereas late maintenance induces scraps. The usual end-of-life criterion for cutting inserts is either based on machining duration, or on tool wear. The direct, optical evaluation of tool wear is t...

Nowadays companies are constantly looking for maximum production efficiency and profitability. To achieve this goal, maintenance actions taken aim to improve the products quality. This article proposes a literature review of the techniques used in order to optimize the maintenance and the quality control of a production tool based on measurement of...

Industrial concerns arise regarding the significant cost of cutting tools in machining process. In particular, their improper replacement policy can lead either to scraps, or to early tool replacements, which would waste fine tools. ISO 3685 provides the flank wear end-of-life criterion. Flank wear is also the nominal type of wear for longest tool...

Nowadays companies are constantly looking for maximum production efficiency. To achieve this goal, the actions taken aim to reduce the overall costs of the company. Thus, measures are taken to ensure the availability of production equipment at the same time as good product quality. This article proposes a study in order to optimize the maintenance...

Les entreprises actuelles recherchent en permanence une efficacité de production maximale. Pour atteindre cet objectif, les actions menées visent à réduire les coûts globaux de l’entreprise. Ainsi, des mesures sont prises pour assurer la disponibilité des équipements de production en même temps qu’une bonne qualité des produits. Cet article propose...

In machining processes, a significant cost contribution is related to the cutting tool insert. A precocious replacement leads to lesser profitability of the cutting tool while a late replacement tends to produce more scraps due to advanced wear of the cutting tool insert. To optimize the replacement times, there is a need to develop an integrated m...

This paper presents an adaptive maintenance model for equipment that can be adjusted (minor preventive maintenance, imperfect state) or replaced (major preventive maintenance, as good as new) at specific scheduled times based on degradation measurements. An initial reliability law that uses a degradation-based model is built from the collection of...

An important proportion of the cost of machined mechanical elements emanates from the cost of cutting tools inserts. A large part of these costs is due to improper maintenance decisions. In this paper, we demonstrate the use of a gamma process tool wear simulation for providing tool lifetimes at several cutting speeds. We show the use of a survival...

Maintaining a track line in a good condition is a continuous challenge since it has to deal with various track line heterogeneities that contribute to accelerate its degradation. As a result, railway tracks should be inspected regularly to detect geometry faults and to plan maintenance actions in consequence. A maintenance plan that minimizes track...

Maintaining a track line in a good condition is a continuous challenge since it has to deal with various track line heterogeneities that contribute to accelerate its degradation. As a result, railway tracks should be inspected regularly to detect geometry faults and to plan maintenance actions in consequence. A maintenance plan that minimizes track...

Le but de cette communication est d'établir une comparaison des processus stochastiques gamma et Wiener pour la modélisation de données relatives à des défauts de géométrie de sections d'une ligne ferroviaire située en Suède. Le processus gamma, de par son caractère monotone et selon la littérature, semble être utilisé de manière exclusive pour mod...

In the field of cutting tool reliability, an investigation based on four complementary approaches for tool wear assessment is proposed: the approach 1 is a general failure times approach (statistical reliability based on flank wear threshold hitting times), the approach 2 is based on power consumption monitoring (statistical reliability based on po...

Optimiser les temps d’inspection et de maintenance de tronçons de voie ferroviaire Garantir des critères de sécurité tout en minimisant les coûts de maintenance Dégradation représentée par des indices de qualité de géométrie de voie Seuils limites sur ces indices de qualité Modélisation de la dégradation par des processus stochastiques Stratégie de...

Simulation de la dégradation des outils de coupe par un procédé gamma Utilisation et ajustement d’un modèle de Cox aux risques proportionnels Prédiction de la durée de vie d’un outil coupant en fonction de la vitesse de coupe (pour un couple outil-matériau particulier) Vérification de la prédiction face à de nouvelles simulations Analyse de la qual...

La maîtrise de l'usure des outils de coupe constitue un des défis majeurs pour réduire les coûts de production et de non-conformité des pièces réalisées en usinage. Pour y parvenir, il est nécessaire de pouvoir modéliser les mécanismes phénoménologiques d'usure intervenant lors de la coupe et de prédire la durée de vie résiduelle de l'outil. Dans c...

Simulation of manufacturing processes (also called virtual manufacturing) is an important research topic in order to optimize the added value of the manufacturing chain. The mastering of these techniques allows companies to remain competitive on the market. Machining operations are very complex to simulate numerically due to the severe conditions u...

L’objectif de cet article est de proposer un modèle de maintenance adaptative pour des équipements pouvant soit être réparés (maintenance imparfaite) ou remplacés (maintenance AGAN) en des instants particuliers prédéterminés obtenus à partir de mesures et de prédictions de la dégradation. Une première loi de fiabilité est obtenue à partir de la dis...

The goal of this paper is to share experience about the degradation assessment of railway track point machines. A real scale point machine test bench was used to perform several thousands of maneuvers. Recorded data consisted in the measurements of the shaft speed and the torque during a maneuver. Some faulty conditions were introduced to obtain de...

La plupart des entreprises sont à la recherche de moyens permettant d'accroître l'efficacité de leur production. Les tentatives visant à réduire les coûts globaux de production sont parfaitement en accord avec cet objectif. Cet article propose une approche de modélisation des procédés de fabrication et tente de démontrer les avantages d'une optimis...

Purpose – The purpose of this paper is to highlight the need for degradation data in order to improve the reliability and the mean residual life estimation of a specific item of equipment and to adapt the preventive maintenance tasks accordingly. Design/methodology/approach – An initial reliability model which uses a degradation-based reliability...

This paper presents an effective formulation to model an automatic transmission for evaluating the vehicle performance in the early development stage of a powertrain design. The corresponding equations of motion are obtained with the help of the virtual power principle, involving all rotating parts of the gearbox. Del Castillo's method is used to e...

Airspace industry components frequently need high added value part including some featuredifficult to manufacture. One of the best example is the thin walls of parts (airplanes frames orthe turbine blades) that have a very low stiffness. The finishing operations for high height to thicknessratio parts lead to chatter vibrations, unacceptable dimens...

This paper focuses on the reliability estimation of equipment based on degradation data and on a economic maintenance model that takes into account corrective and preventive replacements as well as inspection costs. We generate the degradation data with a semi-Markov model with 3 states. Each state has a constant degradation rate that contributes t...

The key to a successful intelligent maintenance consists in replacing worn equipment before a failure occurs. In this context a predictive maintenance policy can be implemented if a degradation indicator is available. This paper focuses on mechanical equipment with degradation over time under various load conditions. More specifically, we will stud...

Optimisation of the milling process is often based on simplified models of the cutting forces generated during the machining operations. Most of the simulation algorithms use simple linear relationship between cutting forces and the undeformed section of the chip. The coefficients of those models (often called specific pressure) are considered to b...

Within the framework of monitoring rotating machines, vibration analysis remains an effective tool for fault detection. This analysis generally consists of measuring acceleration signals from critical and judiciously chosen points of a machine with the help of piezoelectric sensors. However, relevant information concerning the machine health can be...

This study evaluated the possibility of infrared thermography to measure accurately the temperature of ele-ments of a rotating device, within the scope of condition monitoring. The tested machine was a blower cou-pled to a 500 kW electric motor, that operated in multiples regimes. The thermograms were acquired by a fixed thermographic camera and we...

RÉSUMÉ. Afin d'optimiser les politiques d'intervention de maintenance, la connaissance de la durée de vie résiduelle d'une machine est primordiale. En effet, si un remplacement anticipé provoque des coûts d'intervention supplémentaires, l'attente de la défaillance de la machine peut avoir des conséquences bien plus importantes, non seulement par le...

dégradation progressif qui peut être quantifié dans le temps et sur lequel un seuil limite peut être fixé, il est utile de suivre l'évolution de ce processus à différents instants pour évaluer l'état de santé actuel de l'équipement et prévoir son évolution future. A partir des mesures prélevées, un modèle de dégradation peut alors être ajusté. Les...

Rapid development of ITC technologies and decreasing cost of their implications pave the road for the vast applications of condition monitoring in industrial maintenance. In the mean time, maintenance outsourcing of the crucial equipments, as a part of new business strategy, has become a common practice of the SMEs to pursuit their commercial objec...

The key of a succesful intelligent maintenance consists of replacing a worn equipement just before a failure occurs. In this context, predic-tive maintenance policy can be implemented if a degradation indicator is available. This article proposes some degradation models to estimate the reliability of an equipement. Two classes of models are investi...

In this paper, we will propose a framework to perform the optimization of periodical maintenance tasks for a production line, with a specific viewpoint on uncertainty issues from the modelling step to the analysis of numerical results. From a structured log file of operational data, we build a reliability-based model (block diagram) that is used to...

This communication presents the accelerated life testing theory in order to model the reliability of complex systems subject to variable solicitations. The reliability models of series and parallel systems are established and compared with the Cox's proportional hazards model. A methodology of reliability determination according to solicitations va...

Maintenance is the science that studies the compendium of technical and management actions, from the point of view of planning as well as management, which enable an organisation to perform economic, safe, efficient and environmentally effective management, according to established quality standards, of any type of asset or group of assets (Fedele...

Maintenance activities concern the most important assets of firms and can directly impact the competitiveness of companies. Its performance influences the entire production process, from product quality to on-time delivery. Poor maintenance procedures can cost millions of euros in repairs and can lead to very poor products’ quality and substantial...

Warranty of products is a way for manufacturers to raise their clients' trust and, for customers, to protect themselves against economical consequences of malfunctions. The warranty contract may include a bonus (or a penalty) associated with the realization of a prescribed performance level (a number of failures in a fixed period). Such an adaptive...

One of the most important maintenance costs in tramway transport comes from wear of wheel profiles. In the highly competitive railway market, the prediction of wear is then a major concern of the constructors. In this article, we present and compare four models well adapted to tramway conditions, involving contacts on the rolling tread and on the f...

Simulation of the milling process is a widespread method to improve productivity in the machining process and several phenomena can be studied and controlled by this mean. All these methods need input parameters that characterize the interaction between the tool and the workpiece in order to evaluate the cutting forces. Many models exist, but the i...

Purpose Reliability models are generally estimated from small samples. This paper seeks to calculate the uncertainty affecting reliability parameters in function of the sample size. Design/methodology/approach The confidence intervals are calculated on the basis of Monte Carlo simulations and using the variance‐covariance matrix; the two methods a...

Simulation of the milling process is a widespread method to improve productivity in the machining process. Several phenomena can be studied and controlled by this mean. All the simulation methods need parameters that characterize the interaction between the tool and the workpiece in order to evaluate the cutting forces. Many models were developed t...

Several methods to predict vibratory the behavior in machining are listed in the literature. Some of them consist in the linearization of the machining process; they lead to the traditional form known as the 'stability lobes'. This approach does not take into account some characteristics of the milling process (periodic variation of chip thickness,...

The use of vibration data analysis in faults identification often comes up against the question of definition and choice of pertinent features to feed a diagnosis system. An experimental study has been performed on 162 different operation conditions induced on a mechanical test rig by combination of 4 multilevel fault types. Vibration signals are p...

The aim of this article is the identification of reliability parameters on the basis of small samples. First, we have evaluated the errors affecting reliability models and parameters (e.g. mean up time) of non repairable systems. Second, we have studied repairable systems and browsed in the broad line reliability theory characterizing these systems...

A quasi-mode shape (QMS) based dynamic finite element model updating method is developed. The proposed method is applied to locate main model errors. To assess this method, a success ratio for error localization is also defined. Numerical example for printed circuit board (PCB) showed that the new method is much improved compared with force-balance...

Finite Element Model Updating has for objective to increase the correlation between the experimental dynamic responses of a structure and the predictions from a model. Among different initial choices, these procedures need to establish a set of representative parameters to be updated in which some are in real error and some are not. It is therefore...

To be efficient, the simulation of multibody system dynamics requires fast and robust numerical algorithms for the time integration of the motion equations usually described by Differential Algebraic Equations (DAEs). Firstly, multistep schemes especially built up for second-order differential equations are developed. Some of them exhibit superior...

In multibody systems, the deformation of a flexible body is generally modelled by a weighted summation of previously chosen deformation modes. Mode sets composed of static and vibration modes, which proved efficient in structural analysis, are commonly used in practice. The paper presents how the classical reductions can be adapted to better fit th...

During motion, the topology of some special industrial mechanisms may change due to intermittent contact joints, leading to addition, deletion or modification of constraints. The bases of a general computer-aided simulation approach for mechanisms with time-varying topology are developed in this paper. Relative coordinates are used to describe in a...

Three kinds of criteria are described that can be used to evaluate the severity of different vibration environments. The first one is based on the maximal stress induced by the environment on a reference 1 dof mechanical system. The second one uses the classical concept of cumulative damage associated with the assumption of the Miner. The third one...

Operating data are measurements taken from a system under operating conditions. They contain a combination of the system characteristics and generally unknown loading conditions. The scope of this paper is to describe several methods of investigating operational phenomena and to discuss some of their limitations. The use of transmissibilities, mono...

This paper is concerned with the direct dynamic analysis of mechanisms comprising flexible members. It is first recalled how the time integration of the dynamic equations governing the motion of a flexible mechanism is conditioned by the availability of the so-called iteration matrix. The latter is obtained not only from the mass matrix, which is s...

Computer-aided kinematic and dynamic analysis of mechanical systems can be performed in several ways, differing from each others in the nature of coordinates used as configuration parameters, in the analytical principles leading to the equations of motion, and finally, in the numerical algorithms for solving the non-linear set of differential/algeb...

Performances of computer-aided dynamic analysis of mechanisms widely depend on: - nature of coordinates used for localization and orientation of the bodies in space, - analytical principles on which computer codes are founded, - numerical algorithms for solving non-linear systems of differential-algebraic equations. The direct dynamic solution appr...

Résumé Pour évaluer la fiabilité d'un système mécanique soumis à des sollicitations variables, il est nécessaire de connaître les modes de défaillance auxquels le système est soumis. Les systèmes mécaniques étant généralement complexes, cet article présente deux librairies MATLAB Reliabilitix et Simulatrix développées pour estimer la fiabilité de t...

This paper discusses the interest of some degra-dation models and measurements in order to improve the reliability assessment of an equipment. Classical methods used to estimate the reliability are based on a set of failure times on which a reliability model is fitted. Usual models are exponential, Weibull and lognormal laws. If an equipment is sub...

la modÈlisation des dÈfaillances. ABSTRACT. With thegrowing complexity of industrial equipments, optimal performance can only be guaranteed with an appropriated maintenance policy. A platform that simulates and optimizes maintenance policies, named OPTIMAIN, has been developed . It is based on a reliability analysis of equipments, in order to model...

Reliability is defined as the probability that a system will perform properly for a specific period of time under a given set of operating conditions. Particularly, we focus our research on reliability of mechanical equipment and accurate prediction of Mean Up Time (MUT) of the system. As this problem is quite difficult to solve analyt- ically, two...

The estimation of reliability of mechanical sys- tems under variable constraints needs the knowledge of the failure modes to which the system is subjected. These me- chanical systems are generally complex, that is why this article first presents two MATLAB libraries Reliabilitix and Simulatrix developed to estimate reliability of such systems. Two...