Teaching durability in automotive applications using a reliability approach

Fatigue phenomena, which appear generally below the yield stress, is the cause of more than 80 % of in-service mechanical failures. However, the optimization of the weight and cost when designing mechanical components or structures, linked to improved performance, leads to increasingly stressed components. Therefore a fatigue design approach must be done by the engineer. This paper shows the experience gained over five academic years of teaching fatigue the assessment of automotive components using a reliability approach to predict probability of failure, in the engineering school, Arts et Métiers ParisTech, in France. The choice was made to present a comprehensive fatigue assessment approach using a method, initially developed in the automotive industry and since extended to the aeronautical and mechanical industries. This method is known as the “Stress-Strength interference analysis”. The “Stress” represents the distribution of the driver severity, and the “Strength” represents the distribution of the fatigue strength of all the components. A suspension arm is used to illustrate the approach. The Dang Van multiaxial fatigue criterion is implemented in a Finite Elements Code and a danger coefficient is visualized on the meshed structure. The fatigue analysis is interpreted with respect to the target reliability sought by the car- manufacturer

A Biaxial Fatigue Specimen for Uniaxial Loading

The aim of this paper is to present a novel un-notched fatigue test specimen in which a biaxial stress state is achieved using a uniaxial loading condition. This allows the problem of multi-axial fatigue to be studied using relatively common one-axis servo-hydraulic testing machines. In addition the specimen presented here is very compact and can be made using a small volume of material (100x40x4.5mm). For this specimen, the degree of biaxiality, defined by the parameter is equal to approximately 0.45. The specimen geometry was optimised using the Dang Van multi-axial fatigue criterion. In addition to use as a fatigue specimen, it has been demonstrated that the biaxial specimen presented here is also suitable for biaxial tensile tests, to determine the rupture strength of a material in a biaxial stress state. Two different materials have been investigated: The first was wrought aluminium 2024-O in the form of 5mm sheets. The second was a cast aluminium-silicon alloy AlSi7Cu0.5Mg0.3, commonly used in automotive and aeronautical applications. The fatigue strengths were determined at 2x106 cycles and at various R-ratios using a staircase procedure. For the aluminium 2024, it is shown that the biaxial stress state increases the maximum permissible first principal stress when compared to the uniaxial condition. However, in terms of the cast aluminium alloy, it has been demonstrated that this type of fatigue specimen is not suitable for materials containing casting defects, in particular micro-shrinkage pores, because the volume of material, in which the stress state is biaxial, is not large enough.The authors gratefully acknowledge the financial support of PSA – Peugeot Citroën and also that of the Conseil Général du Département de Maine-et-Loire, France

LES PASSEURS DE LANGUES : COMPETENCES INTERCULTURELLES ET SAVOIRS EXPERIENCIELS

International audienceThe subject of the PHD research in sociolinguistic ethnography led on a major international site in New Caledonia is to reveal the value of the intercultural skills of the administrative clerks attached to a unit in charge of visa and work permit procedures

LES PASSEURS DE LANGUES : COMPETENCES INTERCULTURELLES ET SAVOIRS EXPERIENCIELS

International audienceThe subject of the PHD research in sociolinguistic ethnography led on a major international site in New Caledonia is to reveal the value of the intercultural skills of the administrative clerks attached to a unit in charge of visa and work permit procedures

Quelles langues pour quels usages? Le cas d'un site de construction d'une usine de nickel en Nouvelle-Calédonie

The ethnographic field study held as employee of a major industrial building site in New-Caledonia, a remote French island situated in the South Pacific gave me access to intricate data on multilingual language practices in a short-lived city dedicated to labour. It allowed me to observe the language part of the work (Boutet 2001) and the balance of power between the transnational companies' global languages (English and French) and the wide variety of local languages spoken by the Filipino and Oceanian workforces mobilized to erect the plant. This led me to examine the gap between a normalized multilingualism supported by procedures and a relational multilingualism connected to belonging networks (professional, ethnical, social, cultural…). Breaking the rules of language boundaries, this industrial field proved to be a unique opportunity to analyze complex sociolinguistic reconfigurations at work illustrating the notion of sociolinguistic division of labour (Duchêne 2016)

The influence of laser assistance on the machinability of the titanium alloy Ti555-3

The Ti533-3 alloy is a new titanium alloy which is starting to see increased use in the aeronautical domain to improve the durability of components and to optimize the weight/resistance ratio. This alloy is characterized by greater resistance compared to the more commonly used titanium alloys such as Ti6Al4V. However, a disadvantage of the Ti533-3 alloy is that it is very difficult to machine. In this work, the use of laser-assisted machining has been tested to improve chip formation by a thermal softening phenomenon and to improve the machining productivity of the alloy. A parametric investigation of laser assistance on the machinability of the Ti555-3 titanium alloy shows that: (1) the cutting forces can be greatly decreased if the surface temperature is high; (2) the thermal gradient induced by laser heating modifies the surface integrity in terms of strain hardening and residual stresses in the workpiece; and (3) the chip formation mechanisms are also changed, by increasing the sawteeth frequency when using laser assistanc

A Biaxial Fatigue Specimen for Uniaxial Loading

The aim of this paper is to present a novel un-notched fatigue test specimen in which a biaxial stress state is achieved using a uniaxial loading condition. This allows the problem of multi-axial fatigue to be studied using relatively common one-axis servo-hydraulic testing machines. In addition the specimen presented here is very compact and can be made using a small volume of material (100x40x4.5mm). For this specimen, the degree of biaxiality, defined by the parameter is equal to approximately 0.45. The specimen geometry was optimised using the Dang Van multi-axial fatigue criterion. In addition to use as a fatigue specimen, it has been demonstrated that the biaxial specimen presented here is also suitable for biaxial tensile tests, to determine the rupture strength of a material in a biaxial stress state. Two different materials have been investigated: The first was wrought aluminium 2024-O in the form of 5mm sheets. The second was a cast aluminium-silicon alloy AlSi7Cu0.5Mg0.3, commonly used in automotive and aeronautical applications. The fatigue strengths were determined at 2x106 cycles and at various R-ratios using a staircase procedure. For the aluminium 2024, it is shown that the biaxial stress state increases the maximum permissible first principal stress when compared to the uniaxial condition. However, in terms of the cast aluminium alloy, it has been demonstrated that this type of fatigue specimen is not suitable for materials containing casting defects, in particular micro-shrinkage pores, because the volume of material, in which the stress state is biaxial, is not large enough.The authors gratefully acknowledge the financial support of PSA – Peugeot Citroën and also that of the Conseil Général du Département de Maine-et-Loire, France

Roma antica, sacra, moderna: The analogous Romes of the travel guide

The guidebook is not merely a registration of the city and its historical evolution or of the changing preferences of visitors but rather a device that selects and arranges aspects of the city—real as well as imaginary—into a coherent representation of that city. This is particularly the case in Rome, a city composed of three different entities: the ancient, the Christian, and—from the second half of the seventeenth century onward—the modern capital, each with their own monuments and histories. From the sixteenth century onward, Roman guidebooks use the categories of Roma antica, Roma sacra, and Roma moderna to define and represent these three components. In this essay, we argue that the changing application of these labels in the course of the sixteenth and seventeenth centuries reflects not only the far-going physical transformation of the city during that period but also new ways of thinking about the identity of Rome. The reconfiguration of the three “Romes” in the space of the guidebook, operated by means of a continuous rearrangement of sections, illustrations, and descriptions, illustrates how successive authors and publishers attempted to fit the three well-established categories onto reality. An examination of how English visitors reacted to Rome will demonstrate how effective the categories of Roma antica, sacra, and moderna were in organizing the perception of the contemporary city and its analogs.published or submitted for publicationOpe

Rituele betekenisgeving bij de contrareformatorische kerkbouw: de eerstesteenlegging van de Sint-Pietersabdijkerk in Gent (1629)(prov. Oost-Vl.)

In dit artikel wordt aangetoond dat inwijdingsrituelen, zoals de eerstesteenlegging van de Gentse Sint-Pietersabdijkerk anno 1629, op een unieke manier kunnen bijdragen tot de kennis van kerkelijke architectuur. Hiervoor moet men zich toespitsen op de specifieke historische context van de ceremonie, met bijzondere aandacht voor de parafernalia die daarbij zijn geproduceerd. In dit artikel werden twee belangrijke bronnen over de eerstesteenlegging van de Sint-Pietersabdijkerk (i.c. een dichtbundel en een bouwmedaille) geanalyseerd, om te achterhalen hoe ze tot een beter begrip van de architecturale betekenis van één van de eerste koepelkerken in de Zuidelijke Nederlanden konden bijdragen. Er werd vastgesteld dat de eerstesteenlegging in Gent nauw aansloot bij de Italiaanse traditie van luisterrijke ceremonies, kaderend in de brede antiprotestantse beweging sinds het Concilie van Trente. De eerstesteenlegging werd benut om het gebouw nog vóór zijn voltooiing met betekenis te beladen. Dat was bij de Sint-Pietersabdijkerk van prioritair belang, omwille van de contrareformatorische boodschap die de kerk in zich moest dragen. Men kon niet wachten op de effectieve realisatie van het gebouw, omdat het antiprotestantse offensief immers toen, anno 1629, nodig was. Door de boodschap die de commemoratieve medaille en de bundel lofzangen samen uitdroegen, probeerde men dit effect te bereiken. Het gedicht gunt de toehoorder of lezer al een vooruitblik op de toekomstige kerk, door het beschrijven van de aanvoer van bouwmaterialen, de staat van het bouwwerk etc. Dit beeld werd ondersteund door de talrijk vervaardigde bouwmedailles die de geplande voorgevel toonden. De gelijkenissen met de medaille van de Sint-Ignatiuskerk in Rome bleken hier bijzonder frappant