Estimating surface areas of mesh objects - A novel approach for signed distance fields

A tool was developed for surface area estimation of mesh model objects. The tool used signed distance fields together with ray mapping and constructive solid geometry operations to create solids with excluded overlapping surfaces. The goal of the study was to get an area estimation accuracy of at least 95%. The purpose of the tool was to be used inside the Cadmatic application for calculating paint area surfaces of models, especially on hull models. Other tools using signed distance fields are also available. The novelty in the developed tool is the possibility to calculate signed distance fields simultaneously on a large number of objects, and ray mapping taking care of any overlapping surfaces between the objects. The tool creates a single solid object that represents all inserted mesh objects, and the surface area estimation is done on this solid. The results show a sufficient area estimation accuracy, and acceptable runtimes even when applied on hundreds of mesh objects. Other objects, which should not be part of the surface area estimation, may overlap with the objects of interest and create so called hidden surfaces. These hidden surfaces could successfully be excluded from the total surface using constructive solid geometry operations.Ett verktyg utvecklades för ytarea-uppskattning av 3D-CAD modellobjekt. Målet med studien var att få en areauppskattningsnoggrannhet på minst 95 %. Syftet med verktyget var att användas i Cadmatic-applikationen för att beräkna målytsarea på modeller, speciellt på skrovmodeller. Andra verktyg som använder signerade avståndsfält är också tillgängliga. Det nya i det utvecklade verktyget är möjligheten att beräkna signerade avståndsfält samtidigt på ett stort antal objekt, och strålkartläggning som tar hand om eventuella överlappande ytor mellan objekten. Verktyget skapar ett enda fast objekt som representerar alla infogade nätobjekt, och ytareauppskattningen görs på detta solida objekt. Resultaten visar en tillräcklig noggrannhet för areauppskattning och acceptabla körtider även när de appliceras på hundratals objekt. Andra objekt som inte bör ingå i ytareauppskattningen, kan ändå överlappa de intressanta objekten och skapa så kallade dolda ytor. Dessa dolda ytor kunde framgångsrikt uteslutas från den totala ytan med hjälp av konstruktiva solidgeometrioperationer

A simulation framework for predicting process-induced distortions for precise manufacturing of aerospace thermoset composites

The choice of a suitable material model to simulate process induced distortions is important in order to achieve a right first time approach in the design of new moulds. This work investigates the ability of the Cure Hardening Instantaneously Linear Elastic (CHILE) model and a linear viscoelastic material model to predict process induced distortions of an aerospace composite frame. The material models were coupled with a cure kinetics model and a chemical shrinkage model in order to capture the multi-physics phenomena that take place during the curing process. The modelling of the viscoelastic behaviour of the resin is performed with the use of a generalized Maxwell model. A novel methodology is applied for shifting the relaxation times of the composite based on its temperature and degree of cure. It is shown that the viscoelastic model more accurately predicts the measured distortions due to its ability to account for stress relaxation

Formation of Tetrahydrofurano-, Aryltetralin, and Butyrolactone Norlignans through the Epoxidation of 9-Norlignans

Epoxidation of the C=C double bond in unsaturated norlignans derived from hydroxymatairesinol was studied. The intermediate epoxides were formed in up to quantitative conversions and were readily further transformed into tetrahydrofuran, aryltetralin, and butyrolactone products—in diastereomeric mixtures—through ring-closing reactions and intramolecular couplings. For epoxidation, the classical Prilezhaev reaction, using stoichiometric amounts of meta-chloroperbenzoic acid (mCPBA), was used. As an alternative method, a catalytic system using dimeric molybdenum-complexes [MoO2L]2 with ONO- or ONS-tridentate Schiff base ligands and aqueous tert-butyl hydroperoxide (TBHP) as oxidant was used on the same substrates. Although the epoxidation was quantitative when using the Mo-catalysts, the higher temperatures led to more side-products and lower yields. Kinetic studies were also performed on the Mo-catalyzed reactions

Oxidative Transformations of Lignans

Numerous oxidative transformations of lignan structures have been reported in the literature. In this paper we present an overview on the current findings in the field. The focus is put on transformations targeting a specific structure, a specific reaction, or an interconversion of the lignan skeleton. Oxidative transformations related to biosynthesis, antioxidant measurements, and total syntheses are mostly excluded. Non-metal mediated as well as metal mediated oxidations are reported, and mechanisms based on hydrogen abstractions, epoxidations, hydroxylations, and radical reactions are discussed for the transformation and interconversion of lignan structures. Enzymatic oxidations, photooxidation, and electrochemical oxidations are also briefly reported