Development of the doppler electron velocimeter: theory.

Measurement of dynamic events at the nano-scale is currently impossible. This paper presents the theoretical underpinnings of a method for making these measurements using electron microscopes. Building on the work of Moellenstedt and Lichte who demonstrated Doppler shifting of an electron beam with a moving electron mirror, further work is proposed to perfect and utilize this concept in dynamic measurements. Specifically, using the concept of ''fringe-counting'' with the current principles of transmission electron holography, an extension of these methods to dynamic measurements is proposed. A presentation of the theory of Doppler electron wave shifting is given, starting from the development of the de Broglie wave, up through the equations describing interference effects and Doppler shifting in electron waves. A mathematical demonstration that Doppler shifting is identical to the conceptually easier to understand idea of counting moving fringes is given by analogy to optical interferometry. Finally, potential developmental experiments and uses of a Doppler electron microscope are discussed

Doppler electron velocimetry : notes on creating a practical tool.

The Doppler electron velocimeter (DEV) has been shown to be theoretically possible. This report attempts to answer the next logical question: Is it a practical instrument? The answer hinges upon whether enough electrons are available to create a time-varying Doppler current to be measured by a detector with enough sensitivity and bandwidth. The answer to both of these questions is a qualified yes. A target Doppler frequency of 1 MHz was set as a minimum rate of interest. At this target a theoretical beam current signal-to-noise ratio of 25-to-1 is shown for existing electron holography equipment. A detector is also demonstrated with a bandwidth of 1-MHz at a current of 10 pA. Additionally, a Linnik-type interferometer that would increase the available beam current is shown that would offer a more flexible arrangement for Doppler electron measurements over the traditional biprism

Widefield laser doppler velocimeter: development and theory.

The widefield laser Doppler velocimeter is a new measurement technique that significantly expands the functionality of a traditional scanning system. This new technique allows full-field velocity measurements without scanning, a drawback of traditional measurement techniques. This is particularly important for tests in which the sample is destroyed or the motion of the sample is non-repetitive. The goal of creating ''velocity movies'' was accomplished during the research, and this report describes the current functionality and operation of the system. The mathematical underpinnings and system setup are thoroughly described. Two prototype experiments are then presented to show the practical use of the current system. Details of the corresponding hardware used to collect the data and the associated software to analyze the data are presented

IMECE2005-80962 ANALYTICAL AND EXPERIMENTAL STUDIES OF ORTHOTROPIC CORNER- SUPPORTED PLATES WITH SEGMENTED IN-PLANE ACTUATORS

ABSTRACT This paper outlines a model for a corner-supported, thin, rectangular bimorph actuated by a two-dimensional array of segmented, orthotropic PVDF laminates; it investigates the realization and measurement of such a bimorph. First, a model is derived to determine the deflected shape of an orthotropic laminate for a given distribution of voltages over the actuator array. Then, boundary conditions are realized in a laboratory setup to approach the theoretical corner-supported boundary condition. Finally, deflection measurements of actuated orthotropic PVDF laminates are performed with Electronic Speckle Pattern Interferometry and are compared to the model results. NOMENCLATUR

Media 1: Uncertainty characterization of particle depth measurement using digital in-line holography and the hybrid method

Originally published in Optics Express on 04 November 2013 (oe-21-22-26432

Failure Process of Recycled Concrete Aggregate Mortars Based on Digital Image Correlation

International audienceThis study addresses the failure process of mortars made of three different sands. Prismatic 40 × 40 × 160 mm3 specimens were tested less than three points bending after 28 days of curing. Compressive tests were conducted on the two fragments of each mortar resulted from above flexural tests. The three different materials were: standard mortars performed with 0/2 mm natural rolled sand, mortars performed with 0/2 mm crushed sand and mortars performed with 0/2 mm fine recycled concrete aggregate (FRCA).The main aim of this experimental campaign was to study the influence on the mechanical properties of the substitution of natural sand (standardized or crushed gravel) with recycled sand when granular skeletons are identical. Crack propagation, displacement and strain fields, mechanical properties and other model parameters were obtained using 2D-DIC.The findings in these investigations could also be useful to understand the failure process and to improve the mechanical properties of mortars performed of FRCA by optimizing the granular skeleton

Fragmentation Properties of Explosively Driven Additively Manufactured 15-5 ph Stainless Steel Cylinders

Excerpt:This research characterized the fracture behavior of detonating additively manufactured cylinders and compared experimental fragment velocities with theoretical Gurney equation predictions. The additively manufactured cylinders’ interlayer bonding successfully endured explosive loadings, but reduced material ductility caused by processing-related defects decreased casing expansion performance

DIC Challenge: Developing Images and Guidelines for Evaluating Accuracy and Resolution of 2D Analyses

With the rapid spread in use of Digital Image Correlation (DIC) globally, it is important there be some standard methods of verifying and validating DIC codes. To this end, the DIC Challenge board was formed and is maintained under the auspices of the Society for Experimental Mechanics (SEM) and the international DIC society (iDICs). The goal of the DIC Board and the 2D-DIC Challenge is to supply a set of well-vetted sample images and a set of analysis guidelines for standardized reporting of 2D-DIC results from these sample images, as well as for comparing the inherent accuracy of different approaches and for providing users with a means of assessing their proper implementation. This document will outline the goals of the challenge, describe the image sets that are available, and give a comparison between 12 commercial and academic 2D-DIC codes using two of the challenge image sets.status: publishe