Wyniki wyszukiwania - BazTech

1

Suitability of DIC and ESPI optical methods for monitoring fatigue damage development in X10CrMoVNb9-1 power engineering steel

Kopec M., Brodecki A., Kukla D., Kowalewski Z. L.

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 4

542--554

EN

The aim of this research was to compare the effectiveness of two different optical measurement techniques (digital image correlation-DIC and electronic speckle pattern interferometry-ESPI) during fatigue damage development monitoring in X10CrMoVNb9-1 (P91) power engineering steel for pipes. The specimens machined from the as-received pipe were subjected to fatigue loadings and monitored simultaneously using DIC and ESPI techniques. It was found that DIC technique, although characterised by lower resolution, was more effective than ESPI. DIC allows to monitor the fatigue behaviour of steel specimens and accurately indicate the area of potential failure even within the initial stage of fatigue damage development.

2

Composite beams with indented construction joint – comparison of results of laboratory tests and numerical analysis

Sadowski Grzegorz, Wiliński Piotr, Halicka Anna

Budownictwo i Architektura

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2020

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Vol. 19, no 4

31--42

EN

The paper presents a comparative analysis of the behaviour of a composite beam, consisted of a precast element with indented surface and new concrete layer, subjected to 4-point bending. The results obtained from the virtual model of the beam created using the finite element method (Abaqus/CEA 2019 software) were compared with the laboratory test results obtained with use of the digital image correlation (DIC) method for identifying the crack pattern. The virtual model of composite beam was calibrated by the choice of interface parameters ensuring that the value of load resulting in delamination between concrete layers was close to that value obtained in the laboratory tests. The comparative analysis showed that the pattern of bending and shear cracks and the pattern of interface crack obtained with the finite element method reflect the laboratory test results properly. It can be assumed that the crack between concrete layers is related to the appearance and propagation of shear cracks. On the basis of FEM analysis it can be concluded that the phenomena identified as “shear friction” and “dowel action” are significantly activated after the interface cracking.

PL

W pracy przedstawiono analizę porównawczą zachowania się belki zespolonej składającej się z prefabrykatu z powierzchnią ukształtowaną z wrębami oraz betonu uzupełniającego, poddanej czteropunktowemu zginaniu. Otrzymane wyniki z wirtualnego modelu belki zespolonej wykonanego za pomocą metody elementów skończonych (Abaqus/CEA 2019) porównano z wynikami badań laboratoryjnych, w których dla identyfikacji obrazu zarysowania użyto metody obrazowej (DIC – digital image correlation). Wirtualny model belki zespolonej został skalibrowany (przez zmianę parametrów styku pomiędzy betonami) w taki sposób, aby odspojenie pomiędzy betonami powstało przy tym samym obciążeniu, co w badaniach laboratoryjnych. Analiza porównawcza wykazała, że obraz zarysowania od zginania, ścinania oraz obraz rozwoju rys w styku uzyskany metodą elementów skończonych dobrze odzwierciedla rzeczywiste wyniki badań. Można przypuszczać, że zarysowanie pomiędzy betonami związane jest z pojawieniem się i propagacją zarysowania od ścinania. Na podstawie analizy MES można stwierdzić, że zjawiska identyfikowane jako „shear friction” oraz „dowel action” w znacznym stopniu uaktywniają swoje działanie po zarysowaniu styku.

3

Stress field determination based on digital image correlation results

Musial Sandra, Nowak Marcin, Maj Michał

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 4

1183--1193

EN

The aim of this work was to determine the stress distribution during plastic deformation, based on the displacement field obtained using the digital image correlation (DIC) method. To achieve stress distribution, the experimentally measured displacement gradient and the elastoplastic material model with isotropic hardening were used. The proposed approach was implemented in the ThermoCorr program. The developed procedure was used to determine stress fields for uniaxial tension and simple shear processes, carried out on samples made of austenitic steel 304L. Both material parameters, such as the Young's modulus, Poisson's ratio, yield stress, and parameters of the hardening curve, were acquired experimentally. The macroscopic force obtained from the DIC-based stresses and its finite element analysis (FEA) equivalent were compared with that measured during the experi- ment. It was shown that the DIC-based approach gives more accurate results with respect to FEA, especially for a simple shear test, where FEA significantly overestimates the value of experimentally obtained macroscopic force.

4

Non-uniform illumination correction based on the retinex theory in digital image correlation measurement method

Gu G., She B., Xu G., Xu X.

Optica Applicata

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2017

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Vol. 47, nr 2

199--208

EN

Digital image correlation is a well-known optical measurement method for full-field deformation and strain measurements. The quality of speckle images used in digital image correlation calculation can directly affect the measurement accuracy of digital image correlation. In most practical measurement circumstances, a uniform illumination environment is usually required to illuminate the detected object in order to capture speckle images upon different deformed states with uniform background intensity. However, the tested object becomes so large that the adopted light source cannot cover all the interested area with uniform illumination, and the speckle images acquired by CCD camera may have non-uniform background intensity distributions. In this paper, the influence of non-uniform illumination is first analyzed in detail by means of a comparison of experimental results of digital image correlation using speckle patterns with both uniform and non-uniform intensity distributions. Then, a new correctional method based on the combination of the basic retinex theory and the illumination formulae of a point light source is proposed. Finally, a real experiment with non-uniform illumination is implemented to verify the effectiveness of this method.

5

Stress concentration on the contour of a plate opening: analytical, numerical and experimental approach

Momcilovic N., Motok M., Maneski T

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 4

1003--1012

EN

The objective of the paper is to analyze the stress concentration factor (SCF) in the corner of a rectangular plate opening with small radii of curvature and various methods for its derivation. Besides the finite element method, as the most used approach today, there are some analytical and experimental procedures that can obtain stress concentration results in such spots. An analytical approach can deliver prediction of the SCF around the corner but cannot illustrate the stress field opposite to the finite element method. On the other hand, finite element analysis needs much computation time to deal with very sensitive and fine mesh generation around concentration zones. Experimental devices, such as strain gauges are not able to perform measurements on areas where high gradient of stress occurs due to their lack of sensitiveness and larger dimensions compared to the measured part of a structure. The paper presents Digital Image Correlation (DIC) technique that obtains not only stress concentration, where other devices fail, but also provides full displacement, strain and stress field’s even where a high gradient of stress exists. These three methods are discussed, compared and illustrated on the model of a plate with rectangular opening subjected to tension.

6

The use the of digital image correlation in a strain analysis

Frankovsky P., Virgala I., Hudak P., Kostka J.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 4

1283--1292

EN

This paper provides a description of the basic principles and procedures that can be found in strain measurements by means of an experimental method known as the digital image correlation (DIC) while using the correlation system Q-400 and the evaluation software Istra4D. The second part of the paper includes the application of DIC method in strain measurements on a sample made of a PS-1A photoelastic material while using the correlation system Q-400.

7

Usage of Digital Image Correlation in Analysis of Cracking Processes

Marciniak B., Marciniak T., Lutowski Z., Bujnowski S.

Image Processing & Communications

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2012

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Vol. 17, no. 3

21--28

EN

In this paper, the analysis of the possibilities of using Digital Image Correlation (DIC) based on Graphics Processing Unit (GPU) for strain analysis in fatigue cracking processes is presented. The basic assumption for the discussed displacement and strain measurement method under time variable loads was obtaining high measurement sensitivity by simultaneously minimizing the measurement time consumption. For this purpose special computing procedures based on multiprocessor graphic cards were developed, which significantly reduced the total time of displacement and strain analysis. The developed digital procedure for correlation of images has been used for an example of displacement analysis in the method of fatigue crack propagation testing in airplane riveted joints. In this paper are presented the results of the researches of the team run by professor Antoni Zabłudowski.

8

Numerical modelling and verification of Polish ventricular assist device

Milenin A., Kopernik M., Jurkojć D., Gawlikowski M., Rusin T., Darłak M., Kustosz R.

Acta of Bioengineering and Biomechanics

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2012

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Vol. 14, no. 3

49-57

EN

The developed multiscale model of blood chamber of POLVAD (Polish ventricular assist device) was introduced. The tension test for polymer and digital image correlation (DIC) were performed for verification of the strains and displacements obtained in the numerical model of POLVAD_EXT. The numerical simulations were carried out in conditions given in the experiment to compare the results obtained on external surfaces of blood chamber of the POLVAD_EXT. The examined polymer applied in the POLVADs is sensitive to changes of temperature and this observation is considered in all prepared numerical models. The comparison of experimental and numerical results shows acceptable coincidence. There are some heterogeneous distributions of strains in experiment with respect to analysis of computed parameters. The comparison of two versions of blood chambers (POLVAD and POLVAD_EXT) in numerical analysis shows that POLVAD_EXT construction is better with respect to analysis of strain and stress. The maximum values of computed parameters are located in the regions between connectors on the internal surfaces of blood chambers of POLVAD.