A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Residual stress is that which remains in a body that is stationary and at equilibrium with its surroundings. It can be very detrimental to the performance of a material or the life of a component. Alternatively, beneficial residual stresses can be introduced deliberately. Residual stresses are more difficult to predict than the in-service stresses on which they superimpose. For this reason, it is important to have reliable methods for the measurement of these stresses and to understand the level of information they can provide. In this paper, which is the first part of a two part overview, the effect of residual stresses on fatigue lifetimes and structural integrity are first summarised, followed by the definition and measurement of residual stresses. Different types of stress are characterised according to the characteristic length scale over which they self-equilibrate. By comparing this length to the gauge volume of each technique, the capability of a range of techniques is assessed. In the sec...

Residual stress. Part 1 – Measurement techniques

A carbonized plain-weave silk fabric is fabricated into wearable and robust strain sensors, which can be stretched up to 500% and show high sensitivity in a wide strain range. This sensor can be assembled into wearable devices for detection of both large and subtle human activities, showing great potential for monitoring human motions and personal health.

Carbonized Silk Fabric for Ultrastretchable, Highly Sensitive, and Wearable Strain Sensors

Wearable sensors are increasingly finding their way into applications of kinesthetic sensing, personal health monitoring, and smart prosthetics/robotics. A graphene-based composite fiber sensor with a "compression spring" structure is fabricated, featuring the ability of detecting multiple kinds of deformation. This fiber sensor is integrated into wearable sensors for monitoring human activities and intricate movements of robotics successfully.

/pdf/a-stretchable-and-highly-sensitive-graphene-based-fiber-for-5glfmovo59.pdf

A Stretchable and Highly Sensitive Graphene-Based Fiber for Sensing Tensile Strain, Bending, and Torsion

http://doras.dcu.ie/17607/1/Review_of_residual_stresses-Final.pdf

Methods of measuring residual stresses in components

In this paper a new full-field method for the automatic analysis of isochromatic fringes in white light is presented. The method, named RGB photoelasticity, eliminates the typical drawbacks of the classical approach to photoelasticity in white light which requires a subjective analysis of colors and an experienced analyst to acquire and interpret the results.

Towards RGB photoelasticity: Full-field automated photoelasticity in white light

Photoelasticity is one of the most widely used full-field methods for experimental stress analysis. However, the collection of photoelastic parameters can be a long and tedious process. The advent of automated photoelastic systems has allowed the experimentalists to speed up the rate of analysis and to perform more complex investigations.This paper provides a survey of recent methods of automated photoelasticity developed in the last 20 years, i.e. methods of the fringe centres, half-fringe photoelasticity, phase-stepping photoelasticity, methods based on the Fourier transform, spectral content analysis (SCA) and RGB (red, green, blue) photoelasticity.

A review of automated methods for the collection and analysis of photoelastic data

Review of RGB photoelasticity

In this article, an approach based on an array of macro-fiber composite (MFC) transducers arranged as rosettes is proposed for high-velocity impact location on isotropic and composite aircraft panels Each rosette, using the directivity behavior of three MFC sensors, provides the direction of an incoming wave generated by the impact source as a principal strain angle A minimum of two rosettes is sufficient to determine the impact location by intersecting the wave directions The piezoelectric rosette approach is easier to implement than the well-known time-of-flight-based triangulation of acoustic emissions because it does not require knowledge of the wave speed in the material Hence, the technique does not have the drawbacks of time-of-flight triangulation associated to anisotropic materials or tapered sections The experiments reported herein show the applicability of the technique to high-velocity impacts created with a gas-gun firing spherical ice projectiles

High-velocity Impact Location on Aircraft Panels Using Macro-fiber Composite Piezoelectric Rosettes

The phase stepping technique has recently been applied to the automated analysis of photoelastic fringes to determine the isoclinic parameter and the relative retardation. Generally, in the...

Augusto Ajovalasit

Papers

Towards RGB photoelasticity: Full-field automated photoelasticity in white light

A review of automated methods for the collection and analysis of photoelastic data

Review of RGB photoelasticity

High-velocity Impact Location on Aircraft Panels Using Macro-fiber Composite Piezoelectric Rosettes

A method for reducing the influence of quarter-wave plate errors in phase stepping photoelasticity