Perrin Smith Neto

The Shadow Moiré method using the phase shifting technique and digital image processing: computational implementation and application to the 3D-reconstruction of a buckled plate

The Shadow Moire fringe patterns are level lines of equal depth generated by interference between a master grid and its shadow projected on the surface. In simplistic approach, the minimum error is about the order of the master grid pitch, that is, always larger than 0,1 mm, resulting in an experimental technique of low precision. The use of a phase shift increases the accuracy of the Shadow Moire technique. The current work uses the phase shifting method to determine the surfaces three-dimensional shape using isothamic fringe patterns and digital image processing. The current study presents the method and applies it to images obtained by simulation for error evaluation, as well as to a buckled plate, obtaining excellent results. The method hands itself particularly useful to decrease the errors in the interpretation of the Moire fringes that can adversely affect the calculations of displacements in pieces containing many concave and convex regions in relatively small areas.

New equations for phase evaluation in measurements with an arbitrary but constant phase shift between captured intensity signs

We offer new equations for phase evaluation in measurements. Several phase-shifting equations with an arbitrary but constant phase shift between captured intensity signs are proposed. We show a mathematical model that seeks new equations by minimizing the uncertainty in measurements. The equations are similarly derived as the so-called Carre equation. The idea is to develop a generalization of the Carre equation that is not restricted to four images. Errors and random noise in the images cannot be eliminated, but the uncertainty due to their effects can be reduced by increasing the number of observations. An experimental analysis of the mistakes of the technique was made, as well as a detailed analysis of mistakes of the measurement. The advantages of the proposed equation are its precision in the measures taken, speed of processing, and the immunity to noise in signs and images.

Consequences of Enamel Preparation with Sodium Hypochlorite, Polyacrylic and Phosphoric Acids for the Bonding of Brackets with Resin-modified Glass Ionomer Cements

The search for the ideal orthodontic bonding material persists, one that provides physical, chemical, mechanical and biological characteristics to more effectively meet the clinical needs of orthodontists. One of the main challenges lies in achieving a sufficient bond strength that supports both masticatory and orthodontic mechanical loads without being too strong to jeopardize the integrity of the enamel upon removal of the accessories. Furthermore, the ideal bonding system should provide adequate working time for the orthodontist to position the accessories correctly, and it should be biocompatible

New numerical method for the photoelastic technique

The objective of this research is to find new equations for a novel phase-shifting method in digital photoelasticity. Some innovations are proposed. In terms of phase-shifting, only the analyzer is rotated, and the other equations are deduced by applying a new numerical technique instead of the usual algebraic techniques. This approach can be used to calculate a larger sequence of images. Each image represents a measurement of the stresses present in the object. Every photographic image has errors and random noise, but the uncertainties due to these effects can be reduced with a larger number of observations. Keywords: photoelasticity, metrology, stress analysis, optical measurement