Ecole Des Mines De Paris Research Articles

Intervention Research as Management Research in Practice: Learning from a Case in the Fashion Design Industry

Research in the field of management and organizational sciences has yielded a deeper understanding of many emerging business issues. However, the relevance of the contributions has been increasingly criticized, in both the academic and public spheres. We propose the intervention research approach – originally developed by the research group at Ecole des Mines de Paris – as a design science approach able to address both the relevance gap issue and the growing complexity of management practice. It is argued that increasing our understanding of management requires research that is more insightful, influential and immediately applicable. This in turn requires closer collaboration between management and researchers during the inquiry process, which is not always easy to achieve. An illustrative case study of an intervention research project focusing on creativity, conducted inItaly in collaboration with a fashion company, demonstrates how intervention research can be rigorous and relevant to practitioners, and how it can advance theoretical knowledge in management science.

Minerals Scrutinized: Alberto Betim Paes Leme (1883-1938) and the Application of Spectrography1

Alberto Betim Paes Leme (1883–1938) was born in Rio de Janeiro, and graduated in Mining Engineering from the Ecole des Mines de Paris, in 1906, as did many of his countrymen throughout the 19th century. Soon afterwards, he returned to Brazil and worked in various public institutions, including the Brazilian Geological and Mineralogical Survey, and the National Museum, which was to become the University of Rio de Janeiro. In 1916 he was one of the founders of the Brazilian Academy of Sciences. His international connections, in particular with France through the Académie des Sciences and the Société Géologique, made him known and cited abroad, especially in France. Despite the wide range of geological topics he addressed, his seminal contribution was in the field of quantitative analysis of minerals using spectrography. He published various articles, which included: ‘Sur un nouveau procédé d’analyse quantitative’ (1918); ‘Procédé cinématique d’analyse spectrale quantitative’ (1934), and his book Analyse espectral applicada a mineralogia (1918) was reviewed in The American Mineralogist (1920). This paper focuses on the use of this technique and on the discussion of his methods and results.

Knowledge Management for Shared Earth Modeling

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 107152, "Knowledge Management for Shared Earth Modeling," by Laura Mastella, ecole des Mines de Paris and Universidade Federal do Rio Grande do Sul; Michel Perrin, ecole des Mines de Paris; Mara Abel, Universidade Federal do Rio Grande do Sul; and Jean-Francois Rainaud and Walid Touar, Institut Francais du Petrole, prepared for the 2007 SPE Europec Annual Conference and Exhibition, London, 11–14 June. Shared Earth modeling is a process of integrating static (geological structures) and dynamic (hydrocarbon production) data collected from several disciplines to construct a model of a subsurface resource. A shared Earth model (SEM) should allow sharing and integrating data and knowledge related to data interpretation. People from different disciplines, with different technical skills, should be able to provide an SEM with specific technical knowledge concerning how to evolve a hydrocarbon prospect at the various stages of its life cycle. Introduction For knowledge-intensive organizations, the knowledge-management process involves complex interaction of many types of information and expertise that are processed and integrated progressively to produce value results. This work examined the possibility of developing an information-system environment for supporting the generation, codification, and dissemination of geological knowledge related to reservoir modeling for oil/gas exploration. Preliminary Concepts Knowledge management refers to planned and integrated strategies of an organization to allocate and apply assets for knowledge value. These strategies include actions in seven areas: high-level management strategy; company culture and values; organizational structure; human-resources strategy; information system; results monitoring; and learning from companies, clients, government, universities, and others. Knowledge management is also necessary when a community of practice envisages distributing and sharing its knowledge in a homogeneous and organized manner. A community of practice is a group with a shared history and goals, which has, over time, negotiated meanings and shared norms, concepts, and ways of interacting about a particular domain of knowledge. Knowledge Generation. Knowledge is a result of applying cognitive abilities of a person, team, scientific community, or company to solve a problem. Knowledge may be produced internally with the efforts of an organization, in which case knowledge needs only to be recorded and stored. Otherwise, knowledge must be purchased or selected from an external source. Knowledge generation is the result of actions such as internal development, external acquisition, technology transfer, and multidisciplinary codevelopment. Knowledge Codification. Acquired knowledge must be codified so that it can be shared. Knowledge codification includes organizing, classifying, indexing, and storing knowledge. These actions are especially important in collecting new knowledge or retrieving dispersed existing knowledge, such as the corporate knowledge spread throughout the company or knowledge related to a complex process. The success of the codification stage depends on the efficiency of the chosen information systems and knowledge-engineering strategies.

Viscoplastic behaviour of a medium density polyethylene (MDPE): Constitutive equations based on double nonlinear deformation model

The viscoplastic behaviour of a medium density ethylene–butene copolymer (MDPE) is investigated by using samples cut out from thick-walled MDPE pipe. Extensive experimental work has been performed to characterise the nonlinear time-dependent response of such semi-crystalline thermoplastic material. Tests were carried out at 60 °C, on smooth tensile, full axisymmetrically notched creep tensile (FNCT) and double edge notched tensile (DENT) specimens. Tests were conducted under constant strain rate, creep, stress relaxation and dip-test conditions. The experimental data on smooth uniaxial specimens indicate two regimes of creep deformation as well as the existence of a back stress effect. The notched geometries allowed to investigate the creep behaviour of a structure with a local multiaxial stress states near to the crack tip. In order to model the observed material behaviour, a double inelastic deformation model, DID, containing two additive inelastic mechanisms is suggested. Both DID model and its parameters’ optimiser are already implemented in the F.E.M. Zset code at Ecole des Mines de Paris. It is shown that this model is able to reproduce the creep strain history on homogeneous uniaxial tensile tests in a large range of strain rate including the back stress effects, as well as on cracked specimens. Moreover, the time dependent multiaxial stress–strain fields computed (under finite strain formulation) in the vicinity of the crack tip are in good accordance with the Riedel and Rice (RR) analytical singularities. Thus, this fully predictive model clearly shows its superiority and effectiveness over models that take into account only one inelastic viscoplastic deformation under uniaxial conditions.

Long-term hydrodynamic response induced by past climatic and geomorphologic forcing: The case of the Paris basin, France

In the framework of safe underground storage of radioactive waste in low-permeability layers, it is essential to evaluate the mobility of deep groundwaters over timescales of several million years. On these timescales, the environmental evolution of a repository should depend upon a range of natural processes that are primarily driven by climate and geomorphologic variations. In this paper, the response of the Paris basin groundwater system to variations in its hydrodynamic boundary conditions induced by past climate and geodynamic changes over the last five million years is investigated. A three-dimensional transient modelling of the Paris basin aquifer/aquitard system was developed using the code NEWSAM (Ecole des Mines de Paris, ENSMP). The geometry and hydrodynamic parameters of the model originate from a basin model, NEWBAS (ENSMP), built to simulate the geological history of the basin. Geomorphologic evolution is deduced from digital elevation model analysis, which allows to estimate river-valley incision and alpine surrection. Climate forcing results from palaeoclimate modelling experiments using the LMDz atmospheric general circulation model (Institut Pierre Simon Laplace) with a refined spatial resolution, for the present, the Last Glacial Maximum (21 ka) and the Middle Pliocene Warmth (∼3 Ma). The water balance is computed by the distributed hydrological model MODSUR (ENSMP). Results about the simulated evolution of piezometric heads in the system in response to the altered boundary conditions are presented, in particular in the vicinity of ANDRA’s Bure potential repository site within the Callovo-Oxfordian argillaceous layer. For the present, the comparison of head patterns between steady state and time dependent simulation shows little differences for aquifer layers close to the surface but suggests a transient state of the current system in the main aquitards of the basin and in the deep aquifers, characterized by abnormally low fluid potentials. The dependence of the boundary-induced transient effects on the hydraulic diffusivity is illustrated by means of a sensitivity study.

Composite pressure vessels supply an answer to transport problems

Composite pressure vessels are finding increasing numbers of applications. However the traditional proof testing techniques have to be modified to take into account the failure processes encountered in this type of material. Professor Anthony R. Bunsell of the Ecole des Mines de Paris describes how this can be achieved.

Contribution of a three‐dimensional regional scale basin model to the study of the past fluid flow evolution and the present hydrology of the Paris basin, France

AbstractA basin model was built to simulate in three dimensions the 248 Myr geological history of the Paris basin, France, i.e. sedimentation, erosion, compaction heat and fluid flow. This multidisciplinary study was based on a detailed stratigraphic database of more than 1100 well logs together with a hydrodynamic database of 1000 data (heads and permeabilities). The region covers a maximum surface area of 700 000 km2. The NEWBAS code of the Ecole des Mines de Paris was used in order to simulate compaction and heat and fluid flow. Three examples of the use of this model are given to illustrate different features of the geological functioning of the basin.(i) By modelling processes such as sedimentation, compaction, fluid and heat flow, the model provides estimates of the hydraulic conductivity fields within one order of magnitude from observations at the regional scale. This permeability field can reproduce the present‐day observed pressures and fluxes in the basin.(ii) Observed excess pressures in the main aquitards are considered as possible consequences of the geological history of the basin. The calculated excess pressures are small and stay within the range of the measured values, between 0 and 2.75 MPa, close to the pressures in the aquifers. However, the weak excess pressures measured in the Callovo–Oxfordian sequence in the eastern part of the basin are not reproduced by the model. Mechanisms other than compaction disequilibrium must be invoked.(iii) This model also calculates regional‐scale palaeofluid flow whose value is currently arbitrarily assumed by geochemists when studying diagenetic processes. Hence, it provides a hydrologic background for diagenetic models. The cementation in the western Keuper reservoirs was investigated. Topographically driven flow during tectonic inversion periods, e.g. the Lower Cretaceous and Early Tertiary, is shown to be a plausible cause of brine migrations. This brine displacement would then explain the high salinities recorded in the fluid inclusions trapped in the Keuper cements. The conditions for the migration would have been most favourable at the time of the maximum burial, i.e. the Early Tertiary and not the Early Cretaceous as previously suggested.

Numerical Modeling in Materials Science and Engineering. Series in Computational Math, Vol 32

11R2. Numerical Modeling in Materials Science and Engineering. Series in Computational Math, Vol 32. - M Rappaz (Lab of Phys Metall, Swiss Fed Inst of Tech, Lausanne, 1015, Switzerland), M Bellet (Ecole des Mines de Paris, CEMEF, Sophia Antipolis, 06904, France), M Deville (Lab of Comput Eng, Swiss Fed Inst of Tech, Lausanne, 1015, Switzerland). Springer-Verlag, Berlin. 2003. 540 pp. ISBN 3-540-42676-0. $89.95.Reviewed by HM Srivastava (Dept of Math and Stat, Univ of Victoria, PO Box 3045, Victoria V8W 3P4, BC, Canada).The past two decades have witnessed an increasingly diversified account of the various numerical methods and their applications in the fields of materials science and engineering; in particular, the Monte Carlo methods, cellular automata, random walkers, atomistic methods related to molecular dynamics, boundary element methods, homogenization techniques based upon average conservation laws, and so on. The book under review is devoted to the numerical simulation and modeling in (especially) materials science and engineering. It aims at familiarizing the materials scientists and engineers with the numerical methods and techniques that are state-of-the-art in this subject. There are ten chapters in this book. Chapter 1 (Continuous Media) introduces the equations of conservation of mass, momentum, energy and solute, initiates an investigation of the principal equations for materials behavior (which are developed in depth in Chapters 5, 6, and 7), and provides the definitions of the boundary conditions and the initial conditions. And the last chapter (Chapter 10, Appendices) consists of the sections Table of Symbols, Vector Calculus, Gauss Integration Method, Non-Dimensional Numbers, and Interpretation of the Terms of the Elementary Stiffness Matrix for a Diffusion Problem on a Triangular Linear Finite Element. Chapter 2 (The Finite Difference Method), Chapter 3 (The Finite Element Method), and Chapter 4 (Elements of Numerical Algorithms) present lucid and more-or-less self-contained accounts of the subjects titled and also indicate the possibility of extending some of these methods to sundry more complicated cases which are not dealt with in detail in this book. Chapter 5 (Phase Transformations), Chapter 6 (Deformations of Solids), and Chapter 7 (Incompressible Fluid Flow) provide further in-depth developments of the aforementioned principal equations for materials behavior (which were introduced in Chapter 1 itself). The remaining chapters of this book, Chapter 8 (Inverse Methods) and Chapter 9 (Stochastic Methods) describe and illustrate the underlying general principles of each of these additional methods. With the natural exception of Chapter 10, each chapter of this book contains a bibliography for further reading. And, more importantly, Numerical Modeling in Materials Science and Engineering is full of useful computer-generated pictures and diagrams for illustrative purposes. In summary, this is a well written and well-organized reference book that will hopefully prove to be indispensable, especially for those materials scientists and engineers whose investigations make use of the various numerical methods and techniques developed in this book.

3-D modelling of salt and heat transport during the 248 m.y. evolution of the Paris basin : diagenetic implications

Abstract A 3-D model of the Paris basin was constructed to reconstitute its 248 m.y. geologic history from the Trias to the present. The model is based on detailed stratigraphic and lithographic data from about 1,100 petroleum drillings. Its scale is regional and it covers a surface area of 700,000 km2, which exceeds the present extent of the basin in order to allow the paleogeographic evolution of the European plate to be taken into account. The geological history is simulated with the numerical model NEWBAS from the Ecole des Mines de Paris. The model simulates sedimentation, erosion, compaction, fluid flow and processes of solute and heat transport. The objective of this article is to demonstrate the value of this type of modelling for estimating and quantifying the role of fluid circulation in geological processes. Studies of diagenetic cements in the Dogger and Keuper aquifers in the Paris basin have often led their authors to consider the involvement of regional fluid circulation. These studies provide estimates of paleotemperature and paleosalinity which impose constraints on the modelling but the latter may, in turn, contribute to date the events and estimate the relevant processes. By reconstructing heat and salt transport, as proposed in this article, it is therefore possible to define the influence of hydrodynamics on these processes. The history of heat and salt in the basin is shown at various stages on a representative NW-SE cross-section of a present-day flow line which is also valid for Tertiary times. We demonstrate that the role of hydrodynamics may be predominant for salt transport by gravity-driven flow, which explains the salinity increase in the Keuper aquifer and the role of the Bray fault in the salinisation of the Dogger. Although the heat transport is dominated by the conductive component, it is also influenced by the hydrodynamics with a possible convective cooling effect when the head in the aquifers increased at the end of the Tertiary erosion period. This may partly explain the higher temperatures, deduced from fluid inclusions in the Keuper, at the end of the chalk deposition as compared to present ones. According to our simulations, the early Tertiary is the period most compatible with the diagenetic observations for thermal (maximum burial and convective cooling effect) and chemical reasons (topography allowing migration of brines in the Keuper and the Dogger).

CSEG interviews Olivier Dubrule

Olivier Dubrule graduated as a civil engineer in 1978 from Ecole des Mines de Paris. At that time, the institution's “Centre de Géostatistique” was developing new methods and applications for the petroleum industry and Dubrule was offered the opportunity to work on a PhD with Professor G. Matheron, the father of geostatistics, as his thesis director. Having obtained his PhD in 1981, he was offered a job by Sohio in the United States, where for the next four years he worked on reservoir modeling for the Prudhoe Bay Field. Geostatistics was used mostly through kriging, for mapping petrophysical properties across the field. Next he went to work for Shell International in the Hague. In the mid-1980s geostatistical reservoir characterization was taking off. Object-based models and indicator simulation were subjects of great discussion, but most companies at the time were developing their own software. In 1991 Dubrule moved to Elf to head a reservoir characterization project. One of the results of the project was the first geostatistical inversion software, developed in cooperation with Stanford University. In 1994 Dubrule started a new geologic research group at the Elf Geoscience Research in London, where his team developed geostatistical techniques related to seismic data interpretation, with new tools for structural uncertainty quantification and geostatistical inversion of both seismic and production data. After the merger with Total, Dubrule became head of the Earth Modeling and Uncertainties Group, where they had gathered all the expertise related to uncertainty quantification, earth modeling, and geostatistics. Since 2001 Dubrule has been manager of Geoscience Training and Technical Image at Total. One of his areas of interest is technology transfer; the SEG Distinguished Instructor Short Course, “Geostatistics for Seismic Data Integration in Earth Models,” he taught in 28 cities in 20 countries, is part of this activity.

Uranium transport around the reactor zone at Bangombé and Okélobondo (Oklo): examples of hydrogeological and geochemical model integration and data evaluation

The sites at Bangombé and Okélobondo (Oklo) in Gabon provide a unique opportunity to study the behaviour of products from natural nuclear reactions in the vicinity of reactor zones which were active around two billion years ago. The Commission of the European Communities initiated the Oklo Natural Analogue Programme. One of the principal aims was to study indications of present time migration of elements from the reactor zones under ambient conditions. The hydrogeological and hydrochemical data from the Oklo sites were modelled in order to better understand the geochemical behaviour of radionuclides in the natural system, by using independent models and by comparing the modelling outcome. Two modelling approaches were used: M3 code (hydrochemical mixing and mass balance model), developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) and HYTEC (reactive transport model) developed by Ecole des Mines de Paris. Two different reactor zones were studied: Bangombé, a shallow site, the reactor being at 11 m depth, and OK84 at Okélobondo, situated at about 450 m depth, more comparable with a real repository location. This allowed the validation of modelling tools in two different sedimentary environments: one shallow, with a more homogeneous layering situated in an area of meteoric alteration, and the other offering the opportunity to study radionuclide migration from the reaction zone over a distance of 450 m through very heterogeneous sedimentary layers. The modeling results indicate that the chemical reactions retarding radionuclide transport are very different at the two sites. At Bangombé, the decomposition of organic material consumes oxygen and at Okélobondo the oxygen is consumed by inorganic reactions resulting, in both cases, in uranium retardation. Both modelling approaches (statistic with M3 code and deterministic with HYTEC code) could describe this situation. The goal of this exercise is to test codes which can help to describe and understand the processes taking place at the sites, validate the models with in situ data, and thus build confidence in the tools used for future site characterization. Ultimately, this allows identifying and selecting processes and parameters that can be used as input into repository performance assessment calculations and modelling exercises.

CSEG interviews Olivier Dubrule

PreviousNext You have accessThe Leading EdgeVolume 22, Issue 9CSEG interviews Olivier Dubrulehttps://doi.org/10.1190/tle22090850.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Olivier Dubrule graduated as a civil engineer in 1978 from Ecole des Mines de Paris. At that time, the institution's “Centre de Géostatistique” was developing new methods and applications for the petroleum industry and Dubrule was offered the opportunity to work on a PhD with Professor G. Matheron, the father of geostatistics, as his thesis director. Having obtained his PhD in 1981, he was offered a job by Sohio in the United States, where for the next four years he worked on reservoir modeling for the Prudhoe Bay Field. Geostatistics was used mostly through kriging, for mapping petrophysical properties across the field. Next he went to work for Shell International in the Hague. In the mid-1980s geostatistical reservoir characterization was taking off. Object-based models and indicator simulation were subjects of great discussion, but most companies at the time were developing their own software. In 1991 Dubrule moved to Elf to head a reservoir characterization project. One of the results of the project was the first geostatistical inversion software, developed in cooperation with Stanford University. In 1994 Dubrule started a new geologic research group at the Elf Geoscience Research in London, where his team developed geostatistical techniques related to seismic data interpretation, with new tools for structural uncertainty quantification and geostatistical inversion of both seismic and production data. After the merger with Total, Dubrule became head of the Earth Modeling and Uncertainties Group, where they had gathered all the expertise related to uncertainty quantification, earth modeling, and geostatistics. Since 2001 Dubrule has been manager of Geoscience Training and Technical Image at Total. One of his areas of interest is technology transfer; the SEG Distinguished Instructor Short Course, “Geostatistics for Seismic Data Integration in Earth Models,” he taught in 28 cities in 20 countries, is part of this activity.FiguresReferencesRelatedDetails Volume 22Issue 9Sep 2003Pages: 801–920ISSN (print):1070-485X ISSN (online):1938-3789 publication data© 2003 © 2003 by The Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 17 Aug 2012Published in print: 01 Sep 2003 CITATION INFORMATION (2003), "CSEG interviews Olivier Dubrule," The Leading Edge 22: 850-854. https://doi.org/10.1190/tle22090850.1 Plain-Language Summary PDF Download Metrics Loading ...

Gas Saturation in Heterogeneous Sandstone Reservoirs

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 71524, "Fieldwide Variations of Trapped Gas Saturation in Heterogeneous Sandstone Reservoirs," by G. Hamon, TotalFinaElf; K. Suzanne and J. Billiotte, Ecole des Mines de Paris; and V. Trocme, SPE, GazDeFrance, originally presented at the 2001 SPE Annual Technical Conference and Exhibition, New Orleans, 30 September-3 October.

Actor Network Theory and After

1. After ANT: Complexity, Naming and Topology: John Law (Lancaster University). 2. On Recalling ANT: Bruno Latour (Ecole des Mines de Paris). 3. Perpetuum Mobile: Substance, Force and the Sociology of Translation: Steven D. Brown (Keele University) and Rose Capdevila (Nene University College). 4. From Blindness to blindness: Museums, Heterogeneity and the Subject: Kevin Hetherington (Brunel University). 5. Ontological Politics: A Word and Some Questions: Annemarie Mol (Twente University). 6. Who Pays? Can We Pay Them Back?: Nick Lee (Keele University) and Paul Stenner (Bath University). 7. Materiality: Juggling Sameness and Difference: Anni Dugdale (Australian National University Canberra). 8. Staying True to the Laughter in Nigerian Classrooms: Helen Verran (Melbourne University). 9. What is Intellectual Property After?: Marilyn Strathern (Cambridge University). 10. Actor--Network Theory -- The Market Test: Michele Callon (Ecole des Mines de Paris). 11. Good Passages, Bad Passages: Ingunn Moser (University of Oslo) and John Law (Lancaster University). 12. A Sociology of Attachment: Music Amateurs, Drug Users: Emilie Gomart and Antoine Hennion (Ecole des Mines de Paris).

E STEREL: a formal method applied to avionic software development

Dassault Aviation is a French aircraft manufacturer building civil business jets (the Falcon family) and military jet fighters (the Mirage and Rafale families). It has been concerned with formal methods inside the development process of avionic software since 1989. In this paper, we give a comprehensive account of three industrial-size studies carried out at Dassault Aviation using the reactive synchronous language E STEREL and its toolset, in collaboration with the public research team that develops E STEREL at Ecole des Mines de Paris and INRIA Sophia-Antipolis. We deal with software engineering issues related to compilation, optimization and verification of safety-critical embedded software. The goal is to ensure production of efficient and reliable code.

Intergranular fracture stress and phosphorus grain boundary segregation of a Mn-Ni-Mo steel

*EDF, Direction des Etudes et Recherches, Dpt. Etude des Mate´riaux, Ecuelles, BP1,77283 Moreˆt sur Loing, France**Ecole des Mines de Paris, Centre des Mate´riaux, UMR CNRS 7633, BP87,91003 Evry Ce´dex, France(Received February 3, 1999)(Accepted February 18, 1999)IntroductionNuclear Reactor Pressure Vessel (RPV) steel A508 class 3 which is a low alloyed steel is not usuallysensitive to reversible temper embrittlement when properly heat treated. However heterogeneous zonesmay be present in particular near the inner side of the vessel. These zones result from the segregationof the alloying elements (C, Mn, Ni, Mo) and impurities (S, P) taking place during solidification of thematerial. They are called segregated zones (or ghost lines). They can reach 2 mm thick along the radiusand 30 mm long through the circumferential direction. Their susceptibility to reversible temperembrittlement is mainly due to grain boundary phosphorus segregation triggering brittle intergranularfracture when the material is tested at low temperature. In this material like in other steels the influenceof some other alloying elements (Mo, Mn...)isclearly significant (1) and should also be taken intoaccount. But phosphorus effect has proved to be predominant.The effect of ghost lines on A508 class 3 toughness properties has been pointed out (2) but has neverbeen quantitatively studied. The aim of the present study is therefore to find out a quantitativerelationship between grain boundary phosphorus segregation and critical intergranular fracture stress. Asynthetic steel with a chemical composition representative of an average segregated zone was preparedfor the present study. A number of heat treatments were applied to reach different embrittlementconditions. Then brittle fracture properties were obtained by performing cryogenic fracture tests onnotched tensile specimens while the corresponding grain boundary phosphorus levels were measured byAuger electron spectroscopy. Systematic fractographic observations were carried out. Moreover anattempt to determine the influence of temperature on the critical intergranular fracture stress was made.Materials and Heat TreatmentsThe intrinsic mechanical characteristics of segregated zones cannot be easily determined because oftheir very small dimensions (;2 mm width). A material with a chemical composition representative ofan average segregated zone was therefore prepared. Another plate was also elaborated with the nominalcomposition of A508 class 3 (3). A comparison between both materials can be made on Table 1 whereit is noted that the synthetic steel is enriched with most of the alloying elements. In particular

New developments in data processing of noisy images

In some of the methods used in metallography, the signal-noise ratio is so low that direct interpretation is not possible. With regard to microanalysis, the segregation in steels is currently being studied using quantitative X-ray mapping. The acquisition time and counting statistics are limiting factors, particularly for elements in low concentration that present low count rates compared with the background level. Noise from the useful information can be filtered out by geostatistical techniques. A new commercial software, IMAGEO, has been developed by the Ecole des Mines de Paris for noise filtering and signal deconvolution. The main features of this method and the software are described with detailed application examples. With this technique, it is now possible not only to get information from images that would be unusable, but, in the case of microanalysis, to save time for elements in higher concentration by using less counting time.

Fracture mechanics in creep situation interpretation of results on a test specimen

Fracture mechanics in creep situation is a difficult challenge for the 1990s. In France, CEA Saclay has conducted experimental tests on compact tension (CT) specimens at 650°C in order to investigate crack initiation under creep situations. The constitutive material is the 316SPH austenitic stainless steel used for most LMFR structures. Numerical simulations using SYSTUS code and simplified method analysis were performed on one of the tests (CT specimen at 650°C under constant load) to compare some parameters (notch opening, initiation time) with experimental values. The material constitutive law was represented by the complete elasto-viscoplastic CHABOCHE model for systus computation. Owing to geometrical characteristics such as thickness, the situation of the CT specimen was likely to be intermediate between plane stress and plane strain assumptions. From C ∗ parameter, incubation time obtained using the R5 rule was conservative in comparison with the test result. The continuum damage model developed at Ecole des Mines de Paris has also been used to assess creep damage in the notch tip area. The crack initiation time has been deduced from critical damage at characteristic distance ( X c = 0.05 mm). Considering critical damage specifically, for a CT specimen ( D c = 0.05), initiation time obtained was higher than the test result. The results of this study will contribute to the development of a methodology for nocivity analysis of cracks in creep situation.

Laser shock processing for superficial densification of PM materials: B. Dubrujeaud et al (Ecole des Mines de Paris, Paris, France)

Laser shock processing for superficial densification of PM materials: B. Dubrujeaud et al (Ecole des Mines de Paris, Paris, France)

Microstructure of titanium nitride coated alumina powder for reinforcement of HSS: C. Jouanny-Tresy et al, (Ecole des Mines de Paris, Evry, France)

Microstructure of titanium nitride coated alumina powder for reinforcement of HSS: C. Jouanny-Tresy et al, (Ecole des Mines de Paris, Evry, France)