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Probabilistic assessment of a road bridge based on inspection data - a case study emphasizing concrete strength
Get PDFAdvancing seismic capacity curve predictions with a meta-modeling framework for structural systems
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Multi-hazard stochastic time-dependent tropical cyclone fragilities for coastal structures
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Implementation of a void formation and transport computational framework with applicability to liquid composite moulding
No full textThe inclusion of reliable void formation and transport models in process models for LCM is paramount to guarantee the reliability of the manufactured parts, since it allows the estimation of part in-situ void content after mould filling, as well as the estimation of the ideal bleeding time.
The incorporation of void dynamics into mould filling simulations has traditionally been under the form of unsaturated flow, where a continuous saturation field is advected. However, these models lack the prediction of the morphological properties of voids, which are known to influence their mobility through the reinforcement, as well as the final part mechanical properties. Also, direct numerical simulation methodologies, which are fundamentally based on the Volume of Fluid (VoF) method, can provide void morphological data but are too computationally expensive to apply directly into an entire mould filling domain.
Particle tracking methodologies have extensively been used in computational fluid dynamics (CFD), to solve problems in which the fluid flow carries solid particles, such as in sediment deposition. This methodology could prove to be a computationally efficient way to deal with the different void morphologies registered, both during void generation, as well as transport, since each void is taken as a discrete particle, thus possessing its own set of properties.
As of today, mould filling simulation software do not encompass such a methodology to allow mould design optimization. This work discusses the implementation of such a methodology, envisioning a streamlined application into process design
Machining of Hybrid Composite Materials
No full textComposite materials have been having an increasing importance in the industry. Their high specific properties and their high flexibility that allows tailoring materials that suit the needs of practically every project, have been leading to a growth in the demand of this kind of materials. Fiber-Metal Laminates have an established usage on the aeronautic industry and lately have been subject of research by the automotive industry.
Since composite manufacturing methods allow the obtention of components with their final geometry, drilling is the most used machining operation in the machining of composites. Drilling of composites is very demanding from the tools point of view, with very high wear rates and several defects can occur to the workpiece like delamination, fiber pull-outs, burrs and matrix degradation. When combined with a metal, additional challenges appear in drilling these materials such as loads of different magnitudes during a single operation and surface defects on the interface because of chip removal. Orbital drilling is seen as a promising alternative to conventional drilling, presenting several advantages that result in holes with higher quality.
Given the interest the automotive industry has been showing in fiber-metal laminates constituted by steel and carbon fiber reinforced plastics (CFRP) and due to the lack of information regarding drilling of this combination of materials, the aim of this work was to evaluate the influence of the machining parameters in the quality of holes obtained by orbital drilling. A full factorial design of experiments was done and the influence of the parameters was then evaluated by means of an Analysis of Variance (ANOVA)
