Edge Chamfering Algorithm

Võrreldes päris esemeid ja 3D mudeleid, tunneb 3D mudeli enamasti ära selle teravate servade tõttu. Eriti torkavad need silma kõvakatteliste mudelite puhul, nagu mööbli ja masinate mudelid, mis näevad kumeramate servadega välja reaalsemad. Selle lõputöö eesmärk on luua algoritm, mis kasutab servade tahumise tehnikat, et automaatselt mudeli teravaid servi kumerdada. Lõputöö kirjeldab 3D mudeleid ja kuidas neid mängumootoris salvestatakse, erinevaid viise servade tahumiseks ja loodud algoritmi implementatsiooni.When comparing real-life objects and 3D models, one telltale sign that an object in question is a model, is the sharpness of its edges. This is more apparent for hard surface models like models depicting furniture and machinery, which look more real if their edges are a bit rounder. The goal of this thesis is to create an algorithm that uses the edge chamfering technique to automatically smooth out all hard edges of a mesh. The thesis describes 3D models and how they are stored in a game engine, different ways to soften hard edges, and the implementation of the created algorithm

Repair of composite and wood structures

Tese de doutoramento. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto, Universidade de Trás-os-Montes e Alto Douro, Instituto Superior de Engenharia do Porto. 200

A survey on 3D CAD model quality assurance and testing

[EN] A new taxonomy of issues related to CAD model quality is presented, which distinguishes between explicit and procedural models. For each type of model, morphologic, syntactic, and semantic errors are characterized. The taxonomy was validated successfully when used to classify quality testing tools, which are aimed at detecting and repairing data errors that may affect the simplification, interoperability, and reusability of CAD models. The study shows that low semantic level errors that hamper simplification are reasonably covered in explicit representations, although many CAD quality testers are still unaffordable for Small and Medium Enterprises, both in terms of cost and training time. Interoperability has been reasonably solved by standards like STEP AP 203 and AP214, but model reusability is not feasible in explicit representations. Procedural representations are promising, as interactive modeling editors automatically prevent most morphologic errors derived from unsuitable modeling strategies. Interoperability problems between procedural representations are expected to decrease dramatically with STEP AP242. Higher semantic aspects of quality such as assurance of design intent, however, are hardly supported by current CAD quality testers. (C) 2016 Elsevier Ltd. All rights reserved.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund, through the ANNOTA project (Ref. TIN2013-46036-C3-1-R).González-Lluch, C.; Company, P.; Contero, M.; Camba, J.; Plumed, R. (2017). A survey on 3D CAD model quality assurance and testing. Computer-Aided Design. 83:64-79. https://doi.org/10.1016/j.cad.2016.10.003S64798

The leading-edge vortex of yacht sails

In the present work we experimentally verify, for the first time, that a stable Leading-Edge Vortex (LEV) can be formed on an asymmetric spinnaker, which is a high-lift sail used by yachts to sail downwind. We tested a rigid sail in isolation in a water flume at a Reynolds number of ca. 104. The flow field was measured with Particle Image Velocimetry (PIV) over horizontal cross sections. We found that on the leeward side of the sail (the suction side), the flow separates at the leading edge reattaching further downstream and forming a stable LEV. The LEV grows in diameter from the root to the tip of the sail, where it merges with the tip vortex. We detected the LEV using the γ criterion, and we verified its stability over time. The lift contribution provided by the LEV was computed solving a complex potential model of each sail section. This analysis indicated that the LEV provides more than 10% of the total sail’s lift. These findings suggest that the maximum lift of low-aspect-ratio wings with a sharp leading edge, such as spinnakers, can be enhanced by promoting the formation of a stable LEV

Designing for rapid manufacture

Thesis (M. Tech.) -- Central University of Technology, Free State, 2008As the tendency to use sol id freeform fabrication (SFF) technology for the manufacture of end use parts grew, so too did the need for a set of general guidelines that would aid designers with designs aimed specifically for rapid manufacture. Unfortunately, the revolutionary additive nature of SFF technology left certain fundamental principles of conventional design for manufacture and assembly outdated. This implied that whole chapters of theoretical work that had previously been done in this field had to be revised before it could be applied to rapid manufacturing. Furthermore, this additive nature of SFF technology seeded a series of new possibilities and new advantages that could be exploited in the manufacturing domain, and as a result drove design for rapid manufacturing principles even further apart from conventional design for manufacture and assembly philosophy. In this study the impact that rapid manufacture had on the conventional product development process and conventional design for manufacture and assembly guidelines were investigated. This investigation brought to light the inherent strengths and weaknesses of SFF, as well as the design for manufacture and assembly guidelines that became invalid, and consequently lead directly to the characterization of a set of design for rapid manufacture guidelines

Design study of a heavy duty hydraulic machine using finite element techniques

This thesis describes the systematic procedure for investigating the performance and the design analysis of the welded structure of a 150-tonne hydraulic press machine. This machine was designed by ENERPAC without any measurment or variable hydraulic system. The investigation discusses the theoretical and experimental model of the machine to establish the accurately optimal design analysis and further development of the present machine at minimum time and lower cost. The applicability of the existing PC based FE package, as a computer aided design tool, was also investigated. The theoretical model takes into account both conventional analytical formula and numerical technique, using Finite Element Analysis. The conventional model is based on the simple bending theory using the total strain energy principle for 2D beams. The LUSAS Finite Element software system is used as a tool to establish the theoretically predicted numerical model. This model has been discussed with different factors. The factors considered are: the boundary condition; the mesh density and the type of the element being used. The experimental model was based on the electrical method of processing the experimental results using a personal computer through an appropriate data acquisition. The apparatus of the experimental rig and the flow sequence of a computer program, which has been developed to facilitate the measurment of the load deformation of the machine and the load deformation of the workpiece, were discussed. A comparison has been made between the experimental and theoretically predicted results. A good agreement was found between the finite element and the experimental model. Although the conventional analytical model was in good agreement with the plane frame finite element using beam element, this agreement deteriorated between these models and the experimental models. Also, a comparison was made between the stiffness of the actual present machine and the standard stiffness of a similar machine before and after the theoretical modification and disagreement was found. A new optimal design of the structure of the press was discussed theoretically using plane stress finite element model. The factors considered in this optimal design are the width and the chamfering of the press structure. The stiffness of this model has been compared with the standard stiffness,as a design goal, and as a result of this a good agreement has been found and a practical conclusion has been drawn

Rebuilding Urban Place: Negotiating Individuality and Belonging

vi ABSTRACT Rebuilding Urban Place: Negotiating Individuality and Belonging New London, CT September 2013 PETER R. WEBSTER B.S.,TUFTS UNIVERSITY M.ARCH, UNIVERSITY OF MASSACHUSETTS, AMHERST Directed by: Professor Kathleen Lugosch The aim of this thesis is to test an approach for reconnecting ourselves with the urban fabric. By recognising the damage of urban renewal as more than simple blight but rather one that undermines our sense of place, we begin to appreciate the depth of the wound. It is not a matter of reconstructing what was taken away, but rather a process of rehabilitation. Re-establishing a viable sense of place requires the intertwining of both spatial form and social engagement. The project makes use of a parking lot located between the main street and a disruptive artery that forms a rift in the urban fabric. A spatial reorganization mediates the automotive scale of the rift and re-establishes a human one. A local organization, Hygienic Art, is poised to engage the rift with a new performing art center. Interactivity between the site and the client is reflected outward across the block and inward through the building. The center’s performance and service areas are designed to facilitate participatory events, which support the social interactions of the organisation and the extended community. This thesis examines how scale and materiality can nurture the individual and group experience, and how this might be tested at the scale of the city, street, organisation, event, parcel, and building

Development of a manufacturing feature-based design system

Traditional CAD systems are based on the serial approach of the product development cycle: the design process is not integrated with other activities and thus it can not provide information for subsequent phases of product development. In order to eliminate this problem, many modern CAD systems allow the composition of designs from building blocks of higher level of abstraction called features. Although features used in current systems tend to be named after manufacturing processes, they do not, in reality, provide valuable manufacturing data. Apart from the obvious disadvantage that process engineers need to re-evaluate the design and capture the intent of the designer, this approach also prohibits early detection of possible manufacturing problems. This research attempts to bring the design and manufacturing phases together by implementing manufacturing features. A design is composed entirely in a bottom-up manner using manufacturable entities in the same way as they would be produced during the manufacturing phase. Each feature consists of parameterised geometry, manufacturing information (including machine tool, cutting tools, cutting conditions, fixtures, and relative cost information), design limitations, functionality rules, and design-for-manufacture rules. The designer selects features from a hierarchical feature library. Upon insertion of a feature, the system ensures that no functionality or manufacturing rules are violated. If a feature is modified, the system validates the feature by making sure that it remains consistent with its original functionality and design-for-manufacture rules are re-applied. The system also allows analysis of designs, from a manufacturing point of view, that were not composed using features. In order to reduce the complexity of the system, design functionality and design-for manufacture rules are organised into a hierarchical system and are pointed to the appropriate entries of the feature hierarchy. The system makes it possible to avoid costly designs by eliminating possible manufacturing problems early in the product development cycle. It also makes computer-aided process planning feasible. The system is developed as an extension of a commercially available CAD/CAM system (Pro/Engineer), and at its current stage only deals with machining features. However, using the same principles, it can be expanded to cover other kinds of manufacturing processes

A review: drilling performance and hole quality of aluminium alloys for aerospace applications

Despite the growth of composites and other lightweight materials, aluminium alloys remain an attractive choice of the aerospace industry due to their mature manufacturing processes, good resistance to fatigue crack growth and superior damage tolerance. In the aerospace industry, the drilling process is the most challenging among all the other machining process as millions of holes are required for producing riveted and bolted joints in the assembly operation of the aircraft\u27s structures. The major challenges which arise from the drilling of these alloys are characterized by the poor hole quality which might initiate cracks within the airframe structure and reduces their reliability. This results in the rejection of parts at the assembly stage which directly impacts the manufacturing cost. Hence, appropriate selection of tool geometry, tool material and coatings, optimal cutting speed and feed rate, as well as drilling machines, is required to meet the requirement of machined parts. This motivates both academia and industries to further research on the application of drilling operations in the aircraft industry. This review aims to document details on drilling forces, drilling parameters, drill tool geometry, drill materials and coatings, chips formation, analysis of tool wear and hole metrics such as the hole size and circularity error, surface roughness, and burrs formation during the drilling of different aluminium alloys used in the aerospace industry. The focus will be mainly on Al2024 and Al7075 alloys since they are most commonly used and reported in the open literature

Direct modeling techniques in the conceptual design stage in immersive environments for DfA&D

Due to the fast – growing competition of the mass – products markets, companies are looking for new technologies to maximize productivity and minimize time and costs. In the perspective of Computer Aided Process Planning (CAPP), companies want to optimize fixture design and assembly planning for different goals. To meet these demands, the designers' interest in Design for Assembly and Disassembly is growing considerably and is increasingly being integrated into the CAPP. The work described in this thesis aims to exploit immersive technologies to support the design of mating elements and assembly / disassembly, by developing a data exchange flow between the immersive environment and the modeling environment that provides the high – level modeling rules, both for modeling features and for assembly relationships. The main objective of the research is to develop the capability to model and execute simple coupling commands in a virtual environment by using fast direct modeling commands. With this tool the designer can model the coupling elements, position them and modify their layout. Thanks to the physical engine embedded in the scene editor software, it is possible to take into consideration physical laws such as gravity and collision between elements. A library of predefined assembly features has been developed through the use of an external modeling engine and put into communication with the immersive interaction environment. Subsequently, the research involved the study of immersive technologies for workforce development and training of workers. The research on immersive training involved industrial case studies, such as the projection of the disassembly sequence of an industrial product on a head mounted display, and less industrial case studies, such as the manual skills development of carpenters for AEC sectors and the surgeon training in the pre – operative planning in medical field