On the feasibility of crack propagation tracking and full field strain imaging via a strain compatibility functional and the Direct Strain Imaging method

In this paper we present an investigation on the feasibility of exploiting the Direct Strain Imaging (DSI) method for the purpose of tracking propagating discontinuities on the surface of a deformable body under mechanical load. The proposed approach is based on a strain compatibility functional that does not require any assumptions about the continuity conditions of the underlying medium. The proposed approach is based on the recently introduced Direct Strain Imaging method that is used to identify with high accuracy the full fields of strain tensor components that are required to define the strain compatibility functional. We performed synthetic numerical experiments based on the exercising the eXtended Finite Element Method solution for simulating a propagating crack of a particular problem in order to assess the feasibility and potential of the proposed approach. We demonstrated that indeed our DSI-based approach can achieve a very accurate determination of the crack trajectory even under noisy conditions.

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Performance Analysis and Experimental Validation of the Direct Strain Imaging Method

Volume 2A: 33rd Computers and Information in Engineering Conference ◽

10.1115/detc2013-13015 ◽

2013 ◽

Cited By ~ 1

Author(s):

Athanasios Iliopoulos ◽

John G. Michopoulos ◽

John C. Hermanson

Keyword(s):

Experimental Validation ◽

Strain Tensor ◽

Operating Parameter ◽

Strain Imaging ◽

Imaging Method ◽

Engineering Strain ◽

Full Field ◽

Strain Measurements ◽

Full Field Measurement ◽

Preliminary Validation

Direct Strain Imaging accomplishes full field measurement of the strain tensor on the surface of a deforming body, by utilizing arbitrarily oriented engineering strain measurements originating from digital imaging. In this paper an evaluation of the method’s performance with respect to its operating parameter space is presented along with a preliminary validation based on actual experiments on composite material specimens under tension. It has been shown that the method exhibits excellent accuracy characteristics and outperforms methods based on displacement differentiation.

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Full-Field Strain Characterizations and Fracture Process of Rock Blasting Using a Small-Scale Double-Hole Bench Model

Advances in Civil Engineering ◽

10.1155/2020/8649258 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Jun Yang ◽

Xin Liu ◽

Zhenyang Xu ◽

Hongliang Tang ◽

Qi Yu

Keyword(s):

Digital Image Correlation ◽

Crack Propagation ◽

Digital Image ◽

Fracture Process ◽

Image Correlation ◽

Field Strain ◽

Small Scale ◽

Rock Blasting ◽

Full Field ◽

Bench Model

A small-scale double-hole bench model is designed with granite to study the fracture mechanism of rock blasting. By combining high-speed camera and digital image correlation, the full-field strain characterization and fracture process of the specimen bevel surface are investigated. The preliminary test results show that the strain concentration zone corresponds to the crack propagation location, and digital image correlation can well detect the crack propagation. In addition, through observing the crack propagation pattern on the specimen bevel surface, it can be seen that the fracture of the specimen is caused by the dominant horizontal crack and the dominant vertical crack, and the generation of the dominant horizontal crack takes precedence over that of the dominant vertical. Finally, the measurements of two-dimensional digital image correlation and three-dimensional digital image correlation are discussed.

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Full-field X-ray diffraction microscopy using polymeric compound refractive lenses

Journal of Applied Crystallography ◽

10.1107/s1600576714021256 ◽

2014 ◽

Vol 47 (6) ◽

pp. 1882-1888 ◽

Cited By ~ 11

Author(s):

J. Hilhorst ◽

F. Marschall ◽

T. N. Tran Thi ◽

A. Last ◽

T. U. Schülli

Keyword(s):

Imaging Techniques ◽

Light And Electron Microscopy ◽

Added Value ◽

Acquisition Time ◽

Imaging Method ◽

X Ray Diffraction ◽

Polymeric Compound ◽

Full Field ◽

X Ray ◽

Diffraction Imaging

Diffraction imaging is the science of imaging samples under diffraction conditions. Diffraction imaging techniques are well established in visible light and electron microscopy, and have also been widely employed in X-ray science in the form of X-ray topography. Over the past two decades, interest in X-ray diffraction imaging has taken flight and resulted in a wide variety of methods. This article discusses a new full-field imaging method, which uses polymer compound refractive lenses as a microscope objective to capture a diffracted X-ray beam coming from a large illuminated area on a sample. This produces an image of the diffracting parts of the sample on a camera. It is shown that this technique has added value in the field, owing to its high imaging speed, while being competitive in resolution and level of detail of obtained information. Using a model sample, it is shown that lattice tilts and strain in single crystals can be resolved simultaneously down to 10−3° and Δa/a= 10−5, respectively, with submicrometre resolution over an area of 100 × 100 µm and a total image acquisition time of less than 60 s.

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Material parameter identification using finite elements with time-adaptive higher-order time integration and experimental full-field strain information

Computational Mechanics ◽

10.1007/s00466-021-01998-3 ◽

2021 ◽

Author(s):

Stefan Hartmann ◽

Rose Rogin Gilbert

Keyword(s):

Experimental Data ◽

Finite Elements ◽

Parameter Identification ◽

Material Parameter ◽

Measurement Data ◽

Least Square ◽

Image Correlation ◽

Field Strain ◽

Material Parameter Identification ◽

Full Field

AbstractIn this article, we follow a thorough matrix presentation of material parameter identification using a least-square approach, where the model is given by non-linear finite elements, and the experimental data is provided by both force data as well as full-field strain measurement data based on digital image correlation. First, the rigorous concept of semi-discretization for the direct problem is chosen, where—in the first step—the spatial discretization yields a large system of differential-algebraic equation (DAE-system). This is solved using a time-adaptive, high-order, singly diagonally-implicit Runge–Kutta method. Second, to study the fully analytical versus fully numerical determination of the sensitivities, required in a gradient-based optimization scheme, the force determination using the Lagrange-multiplier method and the strain computation must be provided explicitly. The consideration of the strains is necessary to circumvent the influence of rigid body motions occurring in the experimental data. This is done by applying an external strain determination tool which is based on the nodal displacements of the finite element program. Third, we apply the concept of local identifiability on the entire parameter identification procedure and show its influence on the choice of the parameters of the rate-type constitutive model. As a test example, a finite strain viscoelasticity model and biaxial tensile tests applied to a rubber-like material are chosen.

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