Process chain-oriented manufacturability assessment of products by using a constraint satisfaction problem

Dieser Beitrag stellt eine rechnergestützte Modellierungsstrategie vor, um Prozesskettenwissen, wie die Gestaltung der Fertigungsstufen, prozessübergreifende Fertigungsrestriktionen oder Fertigungshilfsmittel, für die Produktgestaltung zu formalisieren und im Kontext des Design for Manufacturing für Produkt- und Prozessgestaltungsentscheidungen bereitzustellen. Dabei werden am Beispiel einer Tailored-Forming-Prozesskette die Herstellungsschritte einer Multimaterial-Welle mittels eines Constraint-Satisfaction-Problems (CSP) modelliert, indem die geometrischen Transformationen einzelner Fertigungsstufen sowie Fertigungsrestriktionen in Form von Constraints und Fertigungsstufen sowie Fertigungshilfsmittel über Parameter in den CSP-Variablen formuliert werden. Das CSP ist damit in der Lage, ausgehend von einem Geometriemodell eines Bauteils eine prozesskettenorientierte Restriktionsprüfung zur Herstellbarkeitsbewertung durchzuführen und automatisiert Fertigungsstufen sowie Fertigungshilfsmittel zu konfigurieren.This paper presents a computer-aided modeling strategy to formalize process chain knowledge, such as the design of manufacturing stages, cross-process manufacturing constraints or manufacturing tools, for product design and to provide it for product and process design decisions in the context of design for manufacturing. Using the example of a tailored forming process chain, the manufacturing steps of a multi-material shaft are modeled by means of a constraint satisfaction problem (CSP) by formulating the geometric transformations of individual manufacturing steps as well as manufacturing restrictions in the form of constraints, and manufacturing steps as well as manufacturing resources via parameters in the CSP variables. The CSP is thus able to perform a process-chain-oriented restriction check for manufacturability evaluation based on a geometry model of a component and to automatically configure manufacturing stages and manufacturing resources and tools

Lerans mikrostruktur

The microstructure of some soft Swedish clays has been investigated by electron microscopy and described by statistical methods using simple structural parameters. The microstructural pattern was found to be characterized by aggregates coupled by links and groups of small particles. Certain microstructural properties seemed to be related to the geotechnical properties of the undisturbed clay material, such as the permeability and sensitivity. The microstructural changes by consolidation and shearing have been investigated. The results formed the basis of a hypothesis concerning the mechanism of these processes. The aggregates seemed to act like rigid bodies up to a certain stress level, the rigidity probably being connected with their low water content and the very high viscosity of the pore water

Transport Mechanisms in Smectite Clay Control Migration of Radionuclides Escaped from Disposed Nuclear Waste

At present two ideologies appear to govern the international selection of concepts for isolation of radionuclides escaped from High-Level Radioactive Waste (HLW) stored underground: “shallow” burial in mined repositories in crystalline rock, and deep geologic disposal in holes bored in crystalline or sedimentary rock, making use of metal canisters isolated from the rock by concrete or dense expansive clay. The present paper describes disposal in smectite clay for delaying or preventing radionuclides from reaching the biosphere when they can still cause great havoc. This is achieved by utilizing the great waste-isolating capacity of the expansive clay through its high hydrophilic capacity and large specific surface area, providing low porosity and limited interconnectivity of the voids, which both makes such clay low-permeable and operating with a very low through-diffusion rate of anionic species like iodine, and of some cationic radionuclides. The expandability of such clay means that it can swell and undergo self-healing in case of microstructural contraction caused by heating. The mechanisms involved in permeation and ion exchange are described based on conceptual microstructural models and their theoretical analogies. Stress/strain phenomena involved in saturation with fluids, desiccation, shearing under deviatoric conditions, and creep strain under stable conditions or at failure are described as well. Longevity matters are given limited space.Validerad;2020;Nivå 1;2020-09-03 (alebob)</p

Microstructure controls physical properties of smectite clay

Environmental protection by isolation of radionuclides escaped from High-Level Radioactive Waste stored underground in crystalline rock can be achieved by surrounding the metal canisters by smectite clay, which provides hindrance of radionuclides to migrate into the surroundings, and ductile embedment of them for absorbing seismic and tectonic displacements in the host rock. The waste-isolating capacity of the expansive clay is explained by its high hydrophilic capacity and large specific surface area giving low porosity and limited interconnectivity of the voids, which both makes such clay low-permeable and gives it a very low through-diffusion rate of anionic species like iodine, and of some cationic radionuclides. The expandability of such clay means that it can swell and undergo self-healing in case of microstructural contraction caused by heating. The mechanisms involved in permeation and ion exchange are described based on conceptual microstructural models and their theoretical analogies. Stress/strain phenomena involved in saturation with fluids, desiccation, shearing under deviatoric conditions, and creep strain under stable conditions or at failure are described as well. Longevity matters, which have been richly treated in the literature, is given limited space. Validerad;2019;Nivå 1;2019-09-02 (johcin)</p

Principles of locating, designing and constructing landfills of hazardous waste

Location, design and construction of a landfill of hazardous waste are in focus. The selected site must be physically stable, and an elevated area with good run-off conditions of precipitated water and tight underground is preferable. The detailed design must adaptate to what legislation requires and be decided on the basis of the required operational lifetime. Several concepts have been proposed and two major principles are compared: 1) location above ground on a drained base with a tight top liner and a less tight bottom liner, and 2) placement below ground with clay liners surrounding the entire waste mass. In either case collection of percolated water can be arranged but maintenance over several hundred years cannot be guaranteed. A design that totally eliminates percolation of the waste is ideal but a number of functions of such concepts need to be considered.Validerad; 2013; 20130814 (ysko)</p