No abstract

No abstract

Digital image correlation (DIC) is an optical technique for full field deformation measurement. The spatial resolution and precision of the measurements are limited by the number of pixels within the image. The use of magnifying optics provides greater spatial resolution images, enabling smaller displacements to be observed with greater accuracy. Increasing the magnification of an image significantly changes the appearance of the non-periodic, stochastic speckle pattern which provides the grey scale contrast necessary for the image correlation method. In the paper a methodology is developed to evaluate the properties of different speckle pattern types under a range of resolutions up to 705 pixel / mm. Numerical deformation of the patterns is also undertaken to evaluate how the changes in the pattern properties affect the accuracy of the DIC measurements.

A point-wise approach to the analysis of complex composite structures using digital image correlation and thermoelastic stress analysis", Strain, 51, 2015, 311-323. DOI: 10.1111 A point-wise approach to the analysis of complex composite structures using digital image correlation and thermoelastic stress analysis Abstract:Thermoelastic Stress Analysis (TSA) and Digital Image Correlation (DIC) are used to examine the stress and strain distributions around the geometric discontinuity in a composite double butt strap joint (DBSJ). A well-known major limitation in conducting analysis using TSA is that it provides a metric that is only related to the sum of the principal stresses and cannot provide the component stresses/strains. The stress metric is related to the thermoelastic response by a combination of material properties known as the thermoelastic constant (coefficient of thermal expansion divided by density and specific heat). The thermoelastic constant is usually obtained by a calibration process. For calibration purposes when using orthotropic materials it is necessary to obtain the thermoelastic constant in the principal material directions, as the principal stress directions for a general structure are unknown. Often it is assumed that the principal stress directions are coincident with the principal material directions. Clearly, this assumption is not valid in complex stress systems and therefore a means of obtaining the thermoelastic constants in the principal stress directions is required. Such a region is that in the neighbourhood of the discontinuities in a bonded lap joint. A methodology is presented which employs a point wise manipulation of the Crammond, G., Boyd, S.W. and Dulieu-Barton, J.M., "A point-wise approach to the analysis of complex composite structures using digital image correlation and thermoelastic stress analysis", Strain, 51, 2015, 311-323.

No abstract