Three-dimensional reconstruction of fracture surfaces: Area matching algorithms for automatic parallax measurements

This paper describes two solutions for systematic measurement of surface elevation that can be used for both profile and surface reconstructions for quantitative fractography case studies. The first one is developed under Khoros graphical interface environment. It consists of an adaption of the almost classical area matching algorithm, that is based on cross-correlation operations, to the well-known method of parallax measurements from stereo pairs. A normalization function was created to avoid false cross-correlation peaks, driving to the true window best matching solution at each region analyzed on both stereo projections. Some limitations to the use of scanning electron microscopy and the types of surface patterns are also discussed. The second algorithm is based on a spatial correlation function. This solution is implemented under the NIH Image macro programming, combining a good representation for low contrast regions and many improvements on overall user interface and performance. Its advantages and limitations are also presented.

Quantitative fractography by digital image processing: NIH Image macro tools for stereo pair analysis and 3-D reconstruction

A set of NIH Image macro programs was developed to make qualitative and quantitative analyses from digital stereo pictures produced by scanning electron microscopes. These tools were designed for image alignment, anaglyph representation, animation, reconstruction of true elevation surfaces, reconstruction of elevation profiles, true-scale elevation mapping and, for the quantitative approach, surface area and roughness calculations. Limitations on time processing, scanning techniques and programming concepts are also discussed.

Boundary identification criteria and geometry analysis of Al 7050 stretch zone from elevation profiles

This article describes the development of a method for analysis of the shape of the stretch zone surface based on parallax measurement theory and using digital image processing techniques. Accurate criteria for the definition of the boundaries of the stretch zone are established from profiles of fracture surfaces obtained from crack tip opening displacement tests on Al-7050 alloy samples. The elevation profiles behavior analysis is based on stretch zone width and height parameters. It is concluded that the geometry of the stretch zone profiles under plane strain conditions can be described by a semi-parabolic relationship. (C) Elsevier B.V., 1999. All rights reserved.

Geração automática de estereomodelos a partir de imagens digitais georreferenciadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo de algoritmos para reconstrução de relevos de superfícies irregulares: aplicações na fractografia quantitativa e caracterização de materiais

Pós-graduação em Engenharia Mecânica - FEG

Protocolo radiográfico para a instalação de mini-implantes: descrição da técnica

In the last decade mini-screws have gained popularity in orthodontics field and a correct placement of mini-screws is a critical point to the success of the skeletal anchorage. A careful clinical and radiographic diagnostic before insertion mini-screw is an essential requirement to achieve the central point of the radicular septum. The correct application of these pre-surgical procedures should avoid possible iatrogenic damages in periodontal ligament, dental roots, nasomaxillary cavities, or even important vascular tissues. As of today, periapical radiographs is a regular pre surgical procedure during mini-screw insertion technique. Nevertheless, accurate execution of the radiographic parallax technique can offer to us useful and precise radiographic images, to decide the right local insertion of mini-screws in to the septum bone. The purpose of this paper is to describe the ¬application of new positioning circular guides in conjunction with a ¬parallax radiographic protocol before placement of orthodontic mini-screws.