Optical Measurements,Modeling and Metrology

Scale Independent Approach to Strength Physics and Optical Interferometry

ABSTRACT Dynamics of deformation and fracture is considered based on a field theoretical approach. The basic postulate of this approach is that deformation is always locally linear elastic, and that the nonlinear behavior in the plastic regime can be formulated by considering the interaction of these local dynamics. By requesting that the transformation matrix representing […]

Optical Techniques That Measure Displacements: A Review of the Basic Principles Part 1

Keywords: moire, holography, speckle methods, fringe analysis, digital image correlation Abstract There are a number of optical techniques that can be used to measure displacements on surfaces utilizing electromagnetic radiation. Moire, holography, speckle interferometry speckle photography, developed separately in the range of visible light. These techniques make it feasible is to find displacements fields and […]

Optical Techniques That Measure Displacements: A Review of the Basic Principles Part 2

Recording displacements in a plane. Incoherent sources In the case of incoherent illumination the following derivations apply to all the methods that operate with incoherent illumination, moire and speckle photography. The speckle photography is in the same relationship to incoherent light moire that speckle interferometry is to moire interferometry. The classical speckle photography utilizes a […]

Optical Techniques That Measure Displacements: A Review of the Basic Principles Part 3

3-D Incoherent illumination The utilization of double viewing system as shown in Figure 17, can be applied to get 3-D information in a similar way to what was described in the preceding sections. The recording of the double illumination in the unloaded and loaded conditions yields the contour of the deformed surface. Likewise in incoherent […]

Optical Techniques That Measure Displacements: A Review of the Basic Principles Part 4

Displacement and spatial resolution of DIC There are two important aspects of DIC as applied to what is basically a speckle photography method. These two aspects are not specific to DIC as a method to retrieve displacements but are relevant to the currently prevailing methodology applied to the so called white speckles, the resolution in […]

Studying phase transformation in a shape memory alloy with full-field measurement techniques

ABSTRACT This paper deals with phase transformations that occur in a Cu-Al-Be single-crystal specimen of shape memory subjected to a tensile test. Two different techniques are used to experimentally evidence these phase transformations: the grid method to obtain strain maps and infrared thermography to deduce heat source distributions from temperature fields. Some typical strain and […]

Correlation between Mechanical Strength and Surface Conditions of Laser Assisted Machined Silicon Nitride Part 1

ABSTRACT High power fiber-coupled diode lasers for Laser-Assisted Machining (LAM) of ceramics provides an efficient, cost effective solution for surface finishing of ceramic products. This paper presents experimental evidence of advantages of LAM over the traditional diamond wheel grinding, a standard technique currently utilized in the finishing of ceramic surfaces. LAM, utilizing fiber-coupled diode lasers, […]

Correlation between Mechanical Strength and Surface Conditions of Laser Assisted Machined Silicon Nitride Part 2

EXPERIMENTAL RESULTS AND DISCUSSION Design of Experiments The room temperature flexural strength of LAM machined Si3N4 specimens were investigated, in both silicon nitrides, against surface conditions as listed in Table 1. All specimens were prepared on the prototype production LAM system. While, process parameters remain proprietary, please note that baseline multi-beam LAM parameters were used, […]

Analysis of speckle photographs by subtracting phase functions of digital Fourier transforms Part 1

Abstract This paper presents a method for measuring displacements and strain in digital speckle photography that is an alternative to currently used correlation techniques. The method is analogous to heterodyne speckle photogrammetry wherein optical Fourier transforms are taken of individually recorded specklegrams and combined in a heterodyne interferometer where an electronic phase meter measured the […]

Analysis of speckle photographs by subtracting phase functions of digital Fourier transforms Part 2

Comparison to Image Correlation The data set that generated the data presented in Table 5 was alternatively analyzed by image correlation via the equation, Where Cab(m,n) is the correlation of the two specklegram images, a and b, F-1 is the inverse Fourier transform operator, and  Fa and Fb are the Fourier transforms of the two […]