Digital Image Correlation (DIC) And Finite Element Modelling (FEM) Assessment On Hybrid Composite Carbon Glass Fibre Under Tensile And Flexural Loading

Digital Image Correlation results of in plane strain measurement is discussed and synthesized on deviation obtained from Finite Element Modelling strain contour. In plane deformation measurement technique of Digital Image Correlation (DIC) full field deformation on Hybrid Composite C/GFRP with comparison with Finite Element Modelling (FEM).The deformation displacement, in-plane strain xx, in-plane strain yy and in-plane shear strain xy are extracted from strain gauge and digital image correlation (DIC) technique via high-speed camera that captures during the experiment. Proposing the in plane deformation measurement technique of Digital Image Correlation (DIC) on Hybrid Composite C/GFRP with comparison to Finite Element Modelling (FEM) via Median Value

Study of image characteristics on digital image correlation error assessment

In this paper, errors related to digital image correlation (DIC) technique applied to measurements of displacements are estimated. This work is based on the generation of synthetic images representative of real speckle patterns. With these images, various parameters are treated in order to determine their impact on the measurement error. These parameters are related to the type of deformation imposed on the speckle, the speckle itself (encoding of the image, image saturation) or the software (subset size)

The Novel Digital Image Correlation Technique in Predicting Behaviour and Failure of Hybrid Composite

This paper presents a technique in measuring deformation occurs on in-plane hybrid composite CFRP/GFRP. The challenging task of extracting mechanical properties of the hybrid composite is assisted with the use of Digital Image Correlation (DIC) technique. DIC is an innovative technique which able to capture full field deformation of tensile deformation. The complex deformation captured for hybrid composite in-plane tensile deformation and behavior using Digital Image Correlation (DIC) under static loading is a new area of study in literature. Generally, hybrid composite consists of more than one reinforcing sections or multiple reinforcing or multiple matrix sections or single reinforcing phase with multiple matrix phases. As a result of a compromise between the materials within the hybrid composite, the deformation and stress analysis are to be evaluated and tailored as each constituent of material carry their own desired mechanical properties according to a performance requirement. It is found in relation of stress-strain relationship of hybrid composite under tensile loading via DIC, the modulus of elasticity is found to record value around 92-97GPa which in theoretical benchmark located in between value of Modulus of Elasticity, E1 for CFRP(120GPa) and GFRP(42GPa) which proves the occurrence of the hybrid effect. It is a new research area in utilizing digital image correlation (DIC) technique on hybrid composite rather than conventional composite in material characterization

Measurement Affecting Errors in Digital Image Correlation

Optical full-field measurement methods such as Digital Image Correlation (DIC) are increasingly used in the area of experimental mechanics. The reliability for each measurement technique depends on the knowledge of its uncertainty and the sources of errors of the results. The aim of this work is to systemize the sources of errors related to digital image correlation (DIC) technique applied to strain measurements. The paper is concluded by some suggestions proposed in order to minimize the errors

<i>In situ</i> observation of strain and phase transformation in plastically deformed 301 austenitic stainless steel

To inform the design of superior transformation-induced plasticity (TRIP) steels, it is important to understand what happens at the microstructural length scales. In this study, strain-induced martensitic transformation is studied by in situ digital image correlation (DIC) in a scanning electron microscope. Digital image correlation at submicron length scales enables mapping of transformation strains with high confidence. These are correlated with electron backscatter diffraction (EBSD) prior to and post deformation process to get a comprehensive understanding of the strain-induced transformation mechanism. The results are compared with mathematical models for enhanced prediction of strain-induced martensitic phase transformation

Validation of a wide plate finite element model using digital image correlation

To investigate the influence of global plastic deformations on girth weld defect tolerance in pipelines, a parametric finite element model has been developed. This paper provides an experimental validation of the model. It describes the test setup and instrumentation used for the evaluation of plastic strain fields around a notch in a tension loaded non-welded X65 mini wide plate. LVDT measurements and digital image correlation (DIC) results are compared to each other and to the results of finite element simulations. Whereas some deviation is observed owing to unavoidable experimental uncertainties and limitations of finite element modelling, the overall correspondence is more than satisfying

Importance of Exposure Time on Digital Image Correlation (DIC) at Extreme Temperatures

Extreme temperatures have increasingly played an important role in engineering applications, including leading edges during hypersonic flight, spacecraft re-entry, and propulsion systems. In order to design for such thermo-mechanical conditions, materials must be characterized using suitable measurement methods. DIC is a popular and versatile method in full-field measurement. In brief, DIC compares images of a sample between its undeformed and deformed state in order to get displacement and strain field maps. Since the images are acquired from digital cameras, it is important to have high contrast images for meaningful correlation. Exposure time is a pivotal camera setting relating to camera sensitivity. Alteration in exposure time results in variation of image contrast, thereby affecting DIC correlation. Also, it is well known that at extreme temperatures, materials emit light which can saturate DIC camera sensors, but the light can be mitigated using optical bandpass filters. In previous work, many have shown that blue bandpass filters can effectively extend the temperature range of DIC, and our lab has shown that ultraviolet (UV) filters can extend the range further. In this thesis, four different temperatures: room temperature, 1300°C, 1450°C, and 1600°C were tested by rigid-motion experiments. At each temperature level, UV images were acquired in order to examine the variation of DIC error over the whole range of exposure time. UV images were acquired at exposure times ranging from 500μs to 61,000μs, which are the minimum and maximum possible values for the cameras used in this thesis. The results showed that there were higher errors of UV-DIC at extremely dark or bright exposure times where as errors were generally insignificant at intermediate exposure times. In order to perform meaningful DIC up to 1600oC, the exposure time for the camera used in this thesis is suggested to be set between 10,000μs and 40,000μs

Analysis of Printed Circuit Boards strains using finite element analysis and digital image correlation

This paper investigates the use of digital image correlation (DIC) and finite element analysis for strain measurement on Printed Board Circuits (PCBs). Circuit boards (PCBs) are designed to mechanically support and electrically connect an electronic component assembly. Due to screw assemblies, the surface level differences on which the PCB is placed, the process of assembling the electronic components induces a certain state of stress and deformation in the PCB. The main components affected are microprocessors due to the way they are glued to PCBs with BGA - Ball grid arrays (BGA). Digital Image Correlation (DIC) is a full-field contactless optical method for measuring displacements and strain in experimental testing, based on the correlation of images taken during test. The experimental setup is realized with Dantec Q-400 system used for image capture and Istra 4D software for image correlations and data analyses. The maximum level of the obtained strain is compared with the allowable limit. Finite element analysis (FEA) is a numerical method of analysis for stresses and strain in structures of any given geometry

Digital image correlation as a usefful tool of analysis of hot cutting process

This study deals with the use of Digital Image Correlation (DIC) to investigate the physical phenomena taking place during the orthogonal cutting of a SG iron specimen at high temperature (around 1,000 °C). After h aving recalled the scientific and industrial context, the experimental procedure developed to record the pictures of the tool covered with a speckle pattern at a frequency of 10,000 Hz (thanks to a high speed camera) is explained. The quantitative exploitation of these recordings is leading to a first set of results showing how the cutting speed and the rake angle of the tool have an influence on the physics of the cutting operation.Arts et Métiers ParisTech - DGAR

Measurement of Pressure-Expansion Behaviour Required in Infant Airway Stents Using Digital Image Correlation (DIC) in Rabbit Trachea

INTRODUCTION: Airway stents are used during treatment of tracheal deformities in infants. However, complications including post implantation stent migration occur [1], resulting from too low stent radial stiffness, which causes permanent stent collapse. This collapse is partially controlled by the mechanical properties of the trachea. However, the mechanical behaviour of the human trachea is poorly understood [2]. A clearer understanding of this relationship should improve the long term performance of infant airway stents. Rabbit tracheas provide an appropriate model for neonates due to the similarities in size and shape [3]. Digital image correlation (DIC) compares the displacement of a random speckled pattern on the surface of a sample before and during deformation to compute mechanical strains [5]. The aim of this study was to determine the pressure-expansion characteristics of full length rabbit trachea using DIC and thereby predict the required mechanical properties for an infant airway stent. MATERIALS AND METHODS: Specimen preparation: Tracheas from New Zealand White rabbits (lengths 42.1±5.3mm, n=20), aged 13-16 weeks were dissected within 3hrs of sacrifice and immediately immersed in phosphate buffered saline and frozen. Prior to testing, samples were thawed and a random speckled pattern was produced on the surface of the trachea (Fig1A) using black ink (Higgins Black Magic, Water Proof Ink) superimposed on a white background (SupaDec Spray Paint). A balloon dilatation catheter (Ultrathin Diamond, Boston Scientific) connected to an inflation pump (Basix COMPAK Inflation syringe) was inserted through the tracheal cavity. DIC and loading regime: A Vic3D digital image correlation device (Rutherford Appleton Laboratory – really?? This is the supplier NOT the manufacturer) was used to record displacement vectors during tracheal expansion. Two high resolution cameras mounted onto a tripod were positioned so that the frontal surface of the trachea was visible to both cameras simultaneously, allowing 3D surface strain measurements. The balloon pressure was increased in increments of 0.2 atm (20kPa) while tracheal expansion was recorded. RESULTS: Axial/longitudinal strain (xx) for applied pressures of 0.2-1.0 atm increased from 0.0053- 0.01115 (Fig1b). DIC showed that deformation of the trachea by balloon dilatation was characterised by uneven expansion with higher Axial/longitudinal strain (yy) occurring distal to the balloon compared with the central zone of the trachea (Fig2). The tracheal expansion modulus at low strains was calculated to be 9.08MPa. Conclusions the DIC technique has the potential to provide accurate assessment of infant airway mechanics and prediction of pressure expansion properties required in paediatric tracheal stents