How to make a speckle pattern suitable for Digital Image Correlation?
Context: Speckle patterns & digital image correlation The principle of image correlation is based on tracking information from a so-called “reference” image in the following images, often called “deformed images.” When using digital image correlation (DIC), speckle patterns are created on the surface of a specimen to address uniqueness concerns. As a result, the accuracy…
Integrating multi-camera DIC at MBDA
As part of its increasing competence in cutting-edge measurement techniques, MBDA has launched a process of testing and internal auditing of measurement resources by multi-camera DIC (Digital Image Correlation). After testing these measurement tools on coupon-type test campaigns, a new stage has been launched with the testing of this technology on more complex structures using multi-camera systems. Compressive…
Crash-test and image correlation: how to measure seat deformations and follow the dummy’s movements
Crash tests are crucial in developing and certifying products, especially for the automotive, aeronautical, and railway industries. These tests simulate collision or impact scenarios in order to evaluate the resistance and safety of products. Among the equipment used to perform these tests is the reverse catapult, which is a device that projects an object, in…
Simulation correlation with Abaqus: how far we’ve come in linking a solver to our software environment
Need to perform a correlation between an Abaqus simulation model and measurements automatically? Whether it is by developing a Python script, actually using the C++ API or developing our parsers, we have experimented a lot with reading and writing formats related to this solver, whether it is to correlate displacement or deformation fields or simply…
Mechanical regularization in EikoTwin DIC
In EikoTwin DIC, the measurement of displacement fields is performed on the simulation mesh. However, as this mathematical problem is by nature ill-posed, a mechanical regularization parameter allows the user to add mechanical conditions to the field measurements. Contrary to most digital image correlation software, at EikoSim, we have chosen to use a mechanical “filter”.…
Digital image correlation for crack measurement
In the context of crack propagation tests on composite materials, digital image correlation provides a wealth of useful information for characterizing crack advance and even the GIc. Case study from Safran. This work is part of Paul Nicolino’s engineering internship at EikoSim, who graduated from INSA Lyon in 2021 in Mechanical Engineering. The problem: highly…
Sources of measurement errors with digital image correlation
In digital image correlation as in any measurement process, errors affect measured data. The characteristic of this method lies in the direct dependency between the test and the measurement error [1,2,3]. Indeed, errors need to be estimated for every new test. These errors can be classified in two categories: the bias corresponding to systematic errors…
Camera calibration: principles and procedures
Using a multi-camera system for metrology and accurate measurements requires the calibration of the pixel coordinates of these cameras. They can be represented mathematically by a projection model in the form of a matrix, allowing the passage of the position of 3D points to their projection in 2D image space. The process of estimating the…
Technical functionality: selection of the measurement mesh
On EikoTwin DIC, the measurements are directly expressed on the simulation mesh. In order to choose which areas of interest for the test are visible to the camera(s), the so-called measurement mesh must first be selected. Indeed, this mesh will be the one where the results will be calculated. It is, therefore, essential to select…
Measurement errors and digital image correlation
By Pierre Baudoin, R&D engineer at EikoSim When conducting a test campaign instrumented by digital image correlation, it must be possible to determine the characteristic measurement error for the quantities of interest studied (measured displacement or strain). This analysis is essential to know whether the measurement made is indeed the desired “signal” and not the…
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