A three-frame digital image correlation (DIC) method for the measurement of small displacements and strains

Abstract

Digital image correlation (DIC) has become a well-established approach for the calculation of full-field displacement and strains within the field of experimental mechanics. Since their introduction, DIC methods have been relying on only two images to measure the displacements and strains that materials undergo under load. It can be foreseen that the use of additional image information for the calculus of displacements and strains, although computationally more expensive, can positively impact DIC method accuracy under both ideal and challenging experimental conditions. Such accuracy improvements are especially important when measuring very small deformations, which still constitutes a great challenge: small displacements and strains translate into equally small digital image intensity changes on the material's surface, which are affected by the digitization processes of the imaging hardware and by other image acquisition effects such as image noise. This paper proposes a new three-frame Newton-Raphson DIC method and evaluates it from the standpoints of accuracy and speed. The method models the deformations that are to be measured under the assumption that the deformation occurs at approximately the same rate between each two consecutive images in the three image sequences that are employed. The aim is to investigate how the use of image data from more than two images impacts accuracy and what is the effect on the computational speed. The proposed method is compared with the classic two-frame Newton-Raphson method in three experiments. Two experiments rely on numerically deformed images that simulate heterogeneous deformations. The third experiment uses images from a real deformation experiment. Results indicate that although it is computationally more demanding, the three-frame method significantly improves displacement and strain accuracy and is less sensitive to image noise.

Experimental Investigation of Delamination Growth in Composite Laminates under a Compressive Load

“…Among others, Infrared Thermography (IRT) and Digital Image Correlation (DIC), whose combination has been used in [14] to study plastic deformations, can be considered effective and reliable no-contact experimental techniques able to assess the integrity of composite structures. The Infrared Thermography technique is usually adopted to evaluate the temperature field [15][16][17], while the Digital Image Correlation technique has been found able to satisfy the increasing demand of experimental detailed information connected to a deformation problem [18][19][20][21][22][23]. The advantages related to these two techniques are the real-time measures, the high precision, and the absence of any contact or interference with the measured samples.…”

Infrared thermography coupled with digital image correlation in studying plastic deformation on the mesoscale level

“…Recently, it has become realizable thanks to the development of full-field measurement techniques, e.g., infrared thermography (IRT) for measuring temperature field [11][12][13] and digital image correlation (DIC) method for accessing displacement and strain fields [14][15][16][17][18][19]. These techniques have the advantages of non-contact, real-time, full-field measurement and high precision.…”

Dynamic response of reverse Taylor impact based on DIC technology

“…The pixel was employed by Asundi [11] to measure the displacement of object. Cofaru et al [12] elaborated on the calculation principles of DIC method, using the method to analyze the test data under low strain rate, and then, obtained the accurate results. High-speed DIC method was applied to three-point bending test which was loaded by Hopkinson bar, and the mechanical properties of aluminum under the action of bending is obtained by Pierron et al [13].…”