Spécification (norme technique)

vignette|Exemple de spécifications relatives à un appareil de sécurité. vignette|Plaque de tare d'un camion. Une spécification est un ensemble explicite d'exigences à satisfaire par un matériau, produit ou service. Si un matériau, produit ou service ne parviennent pas à satisfaire à une ou plusieurs des spécifications applicables, il peut être désigné comme étant hors spécification. Une spécification technique peut être développée en privé, par exemple, par une société, un organisme de réglementation, ou une organisation militaire, ou bien elle peut être développée par des organismes de normalisation qui sont souvent plus amenés à développer des normes volontaires (ces normes volontaires pouvant devenir obligatoires si elles sont adoptées par un du gouvernement ou un contrat d'entreprise). Attentes et exigences exprimées dans l'étude préalable La phase de spécification doit être précédée par une étude préalable, qui décrit l'existant et les attentes et exigences générales

Passages sédunois; restructuration du site des anciens pénitenciers de Sion (VS)

Lucien Roy

Entre les châteaux de Valère et de Tourbillon, surplombant une partie de la ville de Sion, se dressent l’ancien Pénitencier et l’ancienne Chancellerie cantonale. Cloitrés à l’intérieur d’une enceinte massive, ces deux bâtiments sont passés aux mains des musées cantonaux valaisans à l’aube de l’an 2000. Ils accueillent aujourd’hui différentes expositions temporaires et n’ont subi que peu d’aménagements pour cette nouvelle affectation. Ils fonctionnent ainsi toujours comme deux entités distinctes, bien que leurs fonctions soient liées. La nouvelle intervention résout les difficultés du site au moyen d’une construction temporaire à même de changer radicalement l’image du lieu. Cette structure légère s’inspire du type de la galerie autour de laquelle s’articule les différents espaces d’expositions. Elle sert donc à la fois d’élément d’unification et de circulation à travers les deux bâtiments existants. Elle définit également une cour centrale qui clarifie l’organisation générale du site. Ce projet démontre le rôle que le bois peut jouer dans un projet architectural aujourd’hui. A savoir un matériau qui puisse être économiquement compétitif, grâce à l’utilisation d’éléments standardisés et courants dans la région, mais aussi comme ayant le pouvoir d’évoquer un imaginaire collectif vaste et varié. De par sa situation géographique, le projet rend ainsi hommage aussi bien aux anciennes constructions en bois de la ville moyenâgeuse qu’aux grands chantiers des ouvrages d’arts valaisans du XXe siècle.

2021

Influence of residual stresses on the buckling capacity of axially loaded steel columns

Gabriele Falconi

Over the past 60-80 years, the design methodology of steel structures comprising conventional steel profiles, such as HEA, HEB or HEM, has remained unchanged. However, during the 21st century, production methods have improved considerably. The aim of this study is to develop the basis for evaluating and refining the design methodology of steel members by considering realistic residual stress distributions generated during the fabrication process. Out of the numerous production methods, in this study we focus on hot rolled wide flange cross sections which are the most commonly used profiles in construction. Design specifications vary from one country to another. A comparison of the Swiss, European, Canadian, and Japanese approaches would help towards understanding the factors influencing the sizing of steel profiles. Simplified methods based on analytical and semi-experimental models have been developed over time to help engineers consider the phenomenon of lateral buckling by ensuring a sufficient degree of safety. Considering that the above design specifications have been developed based on experimental research of steel profiles and materials characteristic of old practices, this study investigates potential updates in the current design practices. To succeed in this challenge, it is imperative that the residual stress distributions of current cross-sectional and material characteristics are explained. Several studies throughout the past years have tried to focus on formulating simplified models that consider residual stress distributions. The accuracy of these models is investigated and recommendations are provided based on the best fits to measured residual stress distributions. These have explicitly been collected from nearly 10 experimental programs leading to more than 30 measured distributions with 𝐻/𝐵 (where 𝐻 is the height of the wide flange section and 𝐵 is the width) ranging from 0.95 to 2.22 (where 𝑡𝑓 is the thickness of the flange) ranging from 6.30 to 40mm. To supplement the knowledge regarding the residual stress distributions of current material specifications and to widen the cross-sectional range of available distributions, five additional wide flange residual stress distribution measurements (i.e., HEA160, HEM500, IPE120, IPE200 and IPE360) are implemented for the sake of this study. These distributions have been precisely determined through destructive laboratory measurements (i.e., cutting method) that are thoroughly explained in this thesis. In the advent of new technology and software development, structural element simulation can be performed in a thorough and precise manner. With the aid continuum finite element analysis (CFEA), the influence of residual stresses on lateral buckling of columns under axial load will be investigated. Eight cross-sectional profiles (i.e., HEA160, HEB500, HEM300, HEM500, IPE120, IPE200, IPE 360 and IPE400) are investigated. The CFEA consider realistic residual stress distributions that have been conducted by RESSLab, EPFL. The ultimate compressive load of these profiles considering varying buckling lengths (𝜆̅𝑘 ranging from 0.49 to 1.93, where 𝜆̅𝑘 is the normalised buckling length) are determined and compared with available design specifications.

2021

Machine Tool Use Phase

Ioan Oliver Avram

This thesis is motivated from the fundamental decision problem in today's manufacturing industry which could be summarized as one simple question: how is it possible to achieve economic growth by taking advantage of the latest technologies while protecting the environment? The machine tool has undergone a remarkable change in recent years and the classical concept of an independent, manually operated machine tool, specially dedicated to a particular machining process no longer belongs to the production environment. The increasing usage of computer control and measuring equipment as well as workpiece and tool handling devices has transformed the machine tool into a sophisticated hybrid production system having a lower demand for human supervision of the process. All these efforts are gathered together in order to achieve a high productivity system able to machine different parts respecting quality requirements at the lowest cost. In addition, increasing attention to the environmental and health impacts by governmental regulations and by growing awareness in society is forcing manufacturers to find environmentally friendly designs and machining strategies. The objective of this research is to propose a multicriteria decision aid methodology (MCDA) for evaluation of the use phase of a machine tool system by jointly considering economical, technical and environmental criteria which allows the decision maker to be in a better position to make sustainable decisions. The evaluation is carried out at two levels by addressing the process level with its local cutting area effects and the main activities of the machine tool system by giving full consideration to reduction/elimination of the cutting fluid and reduction of the overall energy consumption. After carefully reviewing previous research, a consistent hierarchical evaluation criteria structure and an entity relationship diagram characterizing the organizational scheme of a database, which stores the data to be used in the evaluation process, is proposed for each level. As a second step, this thesis proposes a model for estimation of the mechanical energy requirements of the cutting subsystem of a machine tool based on the cutter location data, the cutting parameters and the technical specifications of the spindle and feed axes. The MCDA methodology and the energy consumption model were implemented in a software tool using the VBA (Visual Basic for Applications) language and was validated through various tests consisting in the machining of different milling and drilling features of a prismatic part by employing different cutting parameters and cooling/lubrication alternatives. In addition to the cutting tests, an extensive monitoring of the power share amongst the main subsystems of a modern machining center was carried out and a power data collection framework was proposed. The acquisition, interpretation and storage of the experimental data were supported by a measurement platform developed in the LabVIEW environment.

EPFL2010

Machine Tool Use Phase

Ioan Oliver Avram

EPFL2010

Influence of residual stresses on the buckling capacity of axially loaded steel columns

Gabriele Falconi

2021