École Nationale d'Ingénieurs de Metz

This paper presents a proposal for a manufacturing upper ontology, aimed to draft a common semantic net in manufacturing domain. Usefulness of ontologies for data formalization and sharing, especially in a manufacturing environment, are first discussed. Details are given about the Web Ontology Language (OWL) and its adequation for ontologies in the manufacturing systems is shown. A concrete proposal named MASON (MAnufacturing’s Semantics ONtology) is presented and two applications of this ontology are exposed: automatic cost estimation and semantic-aware multiagent system for manufacturing.

PURPOSE: The aim of this study was to evaluate the influence of the retention mechanism on the behavior of a mandibular implant-retained overdenture (IRO) during the simulation of mastication. Therefore, a complete three-dimensional finite element model of a mandible with its IRO was developed. MATERIALS AND METHODS: The geometry of the edentulous mandible and overdenture was generated from computed tomography. Two MKIII implants (Nobel Biocare) with ball abutments and Dalbo Plus (Cendres et Métaux) attachments were placed in the canine areas. Three foodstuff positions were analyzed for two retention mechanisms, "resilient" or "rigid". Special attention was given to the modeling of the mandibular environment and of the existing contact between the different components. A probable muscular action was determined following the minimal work principle. RESULTS: The food-crushing force was provided by masseters with a two-third/one-third ratio between working and non-working sides. The "resilient" configuration provided a wider contact area between the mucosa of the denture bearing area and the prosthesis. An increase of the mastication force transiting through the mucosa was also noted and lower stresses were observed in the bone surrounding implants. CONCLUSION: Resilient attachments allowed for an increase of the mastication load transiting through denture bearing surface. Furthermore, this study proposed an accurate model of the mandibular IRO, including its environment and faithful behavior reproduction.

The design of reverse logistics and remanufacturing processes and the recovery of end-of-life products have been well-studied in the literature. Quality, reliability, maintenance and warranty for recovered products and the remanufacturing activities that extend their life are integral issues in reverse logistics. This paper reviews recent and relevant literature on these issues in closed-loop supply chains, with a focus on remanufactured or second-hand products. The published literature is first classified into domain areas of research and practice. The wide array of mathematical tools and techniques used in the literature are then identified and mapped. Finally, the findings are summarised and the main research gaps are highlighted.

With the globalization of manufacturing activities and increasing requirements on interoperability, standardization will play an important role in R&D and day-to-day activities related to enterprise integration and engineering. The paper presents a survey of relevant standards in this area. After a brief introduction on various standardization activities carried out worldwide, the paper gives an overview of the major results achieved and work being performed so far. Comparisons between various standards are presented. A concluding summary and some recommendations for future works are given as part of the conclusion.

Abstract In rolling bearing analysis Hertzian contact theory is used to compute local contact stiffness. This theory does not have a closed form analytical solution and requires numerical calculations to obtain results. Using approximations of elliptical functions and with a mathematical study of Hertzian results, an empirical explicit formulation is proposed in this paper and allows us to obtain the dimensions, the displacement, and the contact stress with at least 0.003% precision and it can be applied to a large range of ellipticity of the contact surface.

PURPOSE: The aim of this work was to study the biomechanical behavior of a "All-on-four" implant-supported prosthesis through a finite element analysis using either isotropic or anisotropic properties of bone. The influence of foodstuff position during mastication was also analysed. MATERIALS AND METHODS: A three-dimensional finite element model of a mandible with a prosthesis supported by four implants was developed. The geometry of the edentulous mandible and prosthesis was generated from computed tomography. Four MKIII implants (two vertical and two tilted) were modeled. The bone elastic properties used in the anisotropic simulations were orthotropic. The comparison of isotropic and anisotropic models was carried out in the loading condition of mastication with a foodstuff positioned on molar. Three distinct configurations, corresponding to three foodstuff positions, were then studied. MSC/Marc code was used to perform all computations. RESULTS: Significant differences in stress, strain, and strain energy densities were found in the comparison of isotropic and orthotropic models. Molar position was revealed to be the most critical one, from a stress and strain level point of view, for implants and framework and consequently for peri-implant bone. It was also observed that implant tilting leads to high stress concentrations in bone for the "All-on-four" concept. CONCLUSION: This study showed that the anisotropic behaviour of bone cannot be neglected in the numerical simulations. The actual design of the prosthesis is not optimal concerning the capacity of all metallic parts to support loads. Finally, it was demonstrated that the tilting of implants induced a high stress level at bone-implant interface.

This paper presents a new class of Petri nets, called process nets with resources (PNRs), for modeling manufacturing systems where only parts can interact with resources, and resources alone cannot interact with one another. PNRs properly include S/sup 3/PR, augmented marked graphs, and some subclasses of resource control net (RCN) merged nets and ERCN merged nets. As a result, PNRs can model far more complex manufacturing process flows and resource sharing than these nets. To construct a PNR, we first build a process net to specify the process flow for each part type. A process net is a consistent, conservative, strongly connected, and live Petri net that satisfies three conditions, including strong reversibility. Then resource places denoting the availability of resource types are added to the process nets. We generalize strong reversibility for PNRs in order to check a sufficient condition for reversibility of PNRs. It is shown that strong reversibility and reversibility of a PNR depends on the siphons. Liveness of a PNR can be verified by checking the potential firing ability of all transitions of each isolated process net, which is, informally speaking, a process net with all resources allocated to it. A manufacturing example is given to show the applicability of PNRs.

The microstructure and the local texture of a large IMI 834 forging were characterized using the Electron Back Scattered Diffraction (EBSD) technique. Crystallographic domains called macrozones and formed by a majority of primary alpha(p) grains with their axes in nearly the same direction were found. They had a band-like structure, parallel to the axial direction of the forging. The influence of these macrozones on the cold dwell-fatigue properties was studied. Several samples were tested under cold dwell-fatigue conditions. The crack initiation and the short-distance propagation region optically matched a bright region that contained numerous quasi-cleavage facets. The analysis of the EBSD measurements showed that this bright region was enclosed within a sharp textured region with axes at less than 30 degrees from the loading axis. The crystallographic features of the crack nucleation site and the crack propagation path were also analysed.

This paper proposes an integrated method for preventive maintenance and inventory control of a production line, composed of n machines (n ≥ 1) without intermediate buffers. The machines are subject to failures and an age-dependent preventive maintenance policy is used. Approximate analytical results are proposed for the one machine case. Simulation software is used to model and simulate the behaviour of the production line of n machines under various maintenance and inventory control strategies. A methodology combining the simulation and genetic algorithms is proposed jointly to optimize maintenance and inventory control policies. Results are compared with the analytical solutions.

A novel line balancing problem is considered. It differs from assembly line balancing problems in that the operations of each workstation are partitioned into blocks of simultaneously executed (parallel) operations. The blocks of each workstation are executed sequentially. For the line design stage considered in this paper, the compatibility (inclusion and exclusion) constraints for grouping operations into blocks and workstations as well as precedence constraints are known. The goal is to minimize a weighted sum of the number of workstations and the number of blocks while achieving a desired cycle time and satisfying all the constraints. The developed exact and heuristic methods are based on a mixed-integer programming approach. Experimental results are reported.

Integrated process planning and scheduling (IPPS) is a manufacturing strategy that considers process planning and scheduling as an integrated function rather than two separated functions performed sequentially. In this paper, we propose a new heuristic to IPPS problem for reconfigurable manufacturing systems (RMS). An RMS consists mainly of reconfigurable machine tools (RMTs), each with multiple configurations, and can perform different operations with different capacities. The proposed heuristic takes into account the multi-configuration nature of machines to integrate both process planning and scheduling. To illustrate the applicability and the efficiency of the proposed heuristic, a numerical example is presented where the heuristic is compared to a classical sequential process planning and scheduling strategy using a discrete-event simulation framework. The results show an advantage of the proposed heuristic over the sequential process planning and scheduling strategy.

A helicopter maneuvers naturally in an environment where the execution of the task can easily be affected by atmospheric turbulence, which leads to variations of its model parameters. This paper discusses the nature of the disturbances acting on the helicopter and proposes an approach to counter the effects. The disturbance consists of vertical and lateral wind gusts. A 7-degrees-of-freedom (DOF) nonlinear Lagrangian model with unknown disturbances is used. The model presents quite interesting control challenges due to nonlinearities, aerodynamic forces, under actuation, and its non-minimum phase dynamics. Two approaches of robust control are compared via simulations with a Tiny CP3 helicopter model: an approximate feedback linearization and an active disturbance rejection control using the approximate feedback linearization procedure. Several simulations show that adding an observer can compensate the effect of disturbances. The proposed controller has been tested in a real-time application to control the yaw angular displacement of a Tiny CP3 mini-helicopter mounted on an experiment platform.

This paper deals with imperfect preventive maintenance (PM) optimisation problem. The system to be maintained is typically a production system assumed to be continuously monitored and subject to stochastic degradation. To assess such degradation, the proposed maintenance model takes into account both corrective maintenance (CM) and PM. The system undergoes PM whenever its reliability reaches an appropriate value, while CM is performed at system failure. After a given number of maintenance actions, the system is preventively replaced by a new one. Both CM as well as PM are considered imperfect, i.e. they bring the system to an operating state which lies between two extreme states, namely the as bad as old state and as good as new state. The imperfect effect of CM and PM is modelled on the basis of the hybrid hazard rate model. The objective of the proposed PM optimisation model consists on finding the optimal reliability threshold together with the optimal number of PM actions to maximise the average availability of the system. A mathematical model is then proposed. To solve this problem an algorithm is provided. A numerical example is presented to illustrate the proposed maintenance optimisation model.

This paper uses siphons to analyze the class of Petri nets constructed by a modular approach by Jeng and DiCesare (1995) for modeling manufacturing systems with shared resources. A resource point of view is taken. First the behavior of each resource is modeled using resource control nets, strongly connected state machines with one place being marked initially. Interactions among the resources are modeled through merging of common transition subnets. This paper provides conditions, expressed in terms of siphons, under which reversibility and liveness of the integrated model are obtained. Relations between siphons and circular-wait are formally established. Superiority of the siphon-based analysis over a previous analysis using circular wait is shown.

ABSTRACT A numerical model has been established in order to simulate the propagation of pressure waves in water networks. The present model formulation is based on a system of partial hyperbolic differential equations. This system has been solved via the characteristics method. The current model provides the necessary data and the necessary damping of water hammer waves, taking into account the structure of the pipe network and the pressure loss. The numerical algorithm estimates the maximum pressure values resulting from the water hammer when closing valves in the network and consequently, the maximum stresses in the pipes have been calculated. In the case of simultaneous closing of several valves, the over pressure can exceed the admissible pressure. In this case, the severity of a defect such as a corrosion crater (pit) has been estimated by computing a safety factor for the stress distribution at the defect tip. This allows the applied notch stress intensity factor to be obtained. To investigate the defect geometry effects, semi‐spherical and semi‐elliptical defects are deemed to exist in up to one‐half of the thickness of the pipe wall. The outcomes have been introduced into the structural integrity assessment procedure (SINTAP) failure diagram assessment (FAD) in order to obtain the safety factor value. Conventionally, it is considered that a failure hazard exists if this safety factor is less than two.

Abstract: In this work, the viscoplastic behaviour of 6082‐T6 and 7075‐T6 aluminium alloys is examined over a wide range of strain rates. Three different testing techniques were applied to this investigation: low‐rate experiments were performed using a regular servo‐hydraulic testing machine, high‐rate tests were conducted using a split Hopkinson bar apparatus and very‐high‐rate experiments were carried out using a miniaturised direct impact test arrangement. The latter testing set‐up allowed for the characterisation of material flow at strain rates up to . These experimental results showed a sharp increase in the rate sensitivity of the materials once a threshold loading rate of is exceeded. This behaviour may be attributed to the presence of viscous drag on high‐velocity dislocation motion. In addition, the thermo‐viscoplastic behaviour of the 6082‐T6 and 7075‐T6 aluminium alloys was analytically described using the extended Rusinek–Klepaczko model of viscous drag effects. Satisfactory correlation was observed between the experiments and the constitutive model results over the entire range of strain rates studied,

The generation of residual stresses in orthogonal machining is analysed by using an Arbitrary Lagrangian Eulerian (ALE) finite element approach. It is shown that a substantial level of tensile residual stresses can be obtained in the vicinity of the machined surface without any contribution of thermal effects. This motivates the development of a parametric study to analyse the effects of the thermomechanical coupling parameters on residual stresses. The roles of thermal expansion, of thermal softening and of the Taylor–Quinney coefficient (controlling the heat generated by plastic flow) are considered separately. The influence of friction is also analysed by assuming dry cutting conditions and a Coulomb friction law. The friction coefficient has a complex effect by controlling heat generation (frictional heating) along the tool rake and clearance faces and the propensity for the chip to stick to the tool. Geometrical effects such as the tool rake angle and the tool edge radius are also discussed.

Averaging models are proposed for viscoplastic and elastic-viscoplastic heterogeneous materials. The case of rigid viscoplastic materials is first discussed. Large deformations are considered. A first class of models is based on different linearizations of the nonlinear local response. A second class of models is obtained from approximate solutions of the nonlinear Eshelby problem. In this problem, an ellipsoid with uniform nonlinear properties is embedded in an infinite homogeneous matrix. An approximate solution is obtained by approaching the matrix behavior with an affine response. Using this solution of the nonlinear Eshelby problem, the average strain rate is calculated in each phase of the composite material, each phase being represented by an ellipsoid embedded in an infinite reference medium. By adequate choices of the reference medium, different averaging models are obtained (self-consistent scheme, nonlinear Mori Tanaka model…). Finally, elasticity is included in the modelling, but with a restriction to small deformations.

We present a new deadlock prevention algorithm for a class Petri nets. A new class of net that is extended from S/sup 3/PR, called ES/sup 3/PR, where deadlocks are related to unmarked siphons. This method is an iterative approach by adding two kinds of control places, called the ordinary control place and weighted control place, to the original model to prevent siphons from being unmarked. We obtained the relation of the algorithm, liveness and reversibility of the controlled net. Finally, a flexible manufacturing example is presented for illustrating the method.

In order to optimize the mechanical behavior of high speed rotors, it is useful to know the load-displacement law of the angular-contact ball bearing. The relationship between preload, speed, and contact angle is studied and a new analytical approach is proposed, giving explicitly and with good precision the contact angle versus preload and rotational speed for the special case of elastically preloaded high speed angular-contact ball bearing.