scholarly journals PROCESSING OF HIGH-SPEED CAMERA IMAGES OF HOPKINSON BAR EXPERIMENTS USING DIGITAL IMAGE CORRELATION

2019 ◽  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Hopkinson Bar ◽  
Image Correlation ◽  
High Speed Camera

Scalable Detection of Defects in Additively Manufactured PLA Components

2018 ◽  
Author(s):  
Amol Kulkarni ◽  
Amey Vidvans ◽  
Mustafa Rifat ◽  
Gregory Bicknell ◽  
Xi Gong ◽  
...  
Keyword(s):  
High Resolution ◽  
Digital Image Correlation ◽  
Rigid Body ◽  
Digital Image ◽  
High Speed ◽  
Rotation Speed ◽  
Image Correlation ◽  
High Speed Camera ◽  
Body Rotation

The present work delineates a novel and scalable approach to characterization of defects in additively manufactured components. The approach is based on digital image correlation and involves characterization of surface speeds during rigid body rotation of the workpiece, followed by normalization with respect to rotation speed. Towards this, two different imaging sources were tested, viz. smartphone camera and sophisticated high-resolution/high-speed camera. The proposed approach successfully delineated horizontal and vertical notch defects in a simple FDM fabricated component. Accuracy of this approach was tested with concomitant laser based scanning. Some limitations of this approach were discussed.

scholarly journals TESTING OF HYBRID NICKEL-POLYURETHANE FOAMS AT HIGH STRAIN-RATES USING HOPKINSON BAR AND DIGITAL IMAGE CORRELATION

2018 ◽  
Vol 18 ◽  
pp. 72 ◽  
Author(s):  
Marcel Adorna ◽  
Petr Zlámal ◽  
Tomáš Fíla ◽  
Jan Falta ◽  
Markus Felten ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Equilibrium ◽  
Polyurethane Foams ◽  
Frame Rate ◽  
Image Correlation ◽  
Correlation Technique ◽  
High Speed Camera

In this paper Split Hopkinson pressure bar (SHPB) was used for dynamic testing of nickel coated polyurethane hybrid foams. The foams were manufactured by electrodeposition of a nickel coating on the standard open-cell polyurethane foam. High strength aluminium alloy bars instrumented with foil strain-gauges were used for dynamic loading of the specimens. Experiments were observed using a high-speed camera with frame-rate set to approx. 100-150 kfps. Precise synchronisation of the high-speed camera and the strain-gauge record was achieved using a through-beam photoelectric sensor. Dynamic equilibrium in the specimen was achieved in all measurements. Digital image correlation technique (DIC) was used to evaluate in-plane displacements and deformations of the samples. Specimens of two different dimensions were tested to investigate the collapse of the foam structure under high-speed loading at the specific strain-rate and strain.

High-speed digital-image correlation method

2009 ◽  
Vol 34 (13) ◽  
pp. 1955 ◽  
Author(s):  
Min Wang ◽  
Hao Wang ◽  
Yuwan Cen
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Correlation Method ◽  
Image Correlation ◽  
Digital Image Correlation Method

scholarly journals High-Speed X-ray Stereo Digital Image Correlation for Fluid-Structure Interactions in a Shock Tube

2020 ◽  
Author(s):  
Jeremy James ◽  
Elizabeth M. Jones ◽  
Enrico C. Quintana ◽  
Kyle P. Lynch ◽  
Benjamin R. Halls ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Shock Tube ◽  
Digital Image ◽  
High Speed ◽  
Image Correlation ◽  
Fluid Structure Interactions ◽  
Fluid Structure ◽  
X Ray ◽  
Stereo Digital Image Correlation

Local Elasto-Plastic Identification of the Behaviour of Friction Stir Welds with the Virtual Fields Method

2011 ◽  
Vol 70 ◽  
pp. 135-140 ◽  
Author(s):  
G. Le Louëdec ◽  
M.A. Sutton ◽  
Fabrice Pierron
Keyword(s):  
Mechanical Properties ◽  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Weld Zone ◽  
Spatial Variations ◽  
Image Correlation ◽  
Virtual Fields Method ◽  
Full Field ◽  
Friction Stir

Welding is one of the most popular joining technologies in industry. Depending on the materials to be joined, the geometry of the parts and the number of parts to be joined, there is a wide variety of methods that can be used. These joining techniques share a common feature: the material in the weld zone experiences different thermo-mechanical history, resulting in significant variations in material microstructure and spatial heterogeneity in mechanical properties. To optimize the joining process, or to refine the design of welded structures, it is necessary to identify the local mechanical properties within the different regions of the weld. The development of full-field kinematic measurements (digital image correlation, speckle interferometry, etc.) helps to shed a new light on this problem. The large amount of experimental information attained with these methods makes it possible to visualize the spatial distribution of strain on the specimen surface. Full-field kinematic measurements provide more information regarding the spatial variations in material behaviour. As a consequence, it is now possible to quantify the spatial variations in mechanical properties within the weld region through a properly constructed inverse analysis procedure. High speed tensile tests have been performed on FSW aluminium welds. The test was performed on an MTS machine at a cross-head speed of up to 76 mm/s. Displacement fields were measured across the specimen by coupling digital image correlation with a high-speed camera (Phantom V7.1) taking 1000 frames per second. Then, through the use of the virtual fields method it is possible to retrieve the mechanical parameters of the different areas of the weld from the strain field and the loading. The elastic parameters (Young’s modulus and Poisson’s ratio) are supposed to be constant through the weld. Their identification was carried out using the virtual fields method in elasticity using the data of the early stage of the experiment. Assuming that the mechanical properties (elastic and plastic) of the weld are constant through the thickness, the plastic parameters were identified on small sections through the specimen, using a simple linear hardening model. This method leads to a discrete identification of the evolution of the mechanical properties through the weld. It allows the understanding of the slight variations of yield stress and hardening due to the complexity of the welding process.

Dynamic Digital Image Correlation of a Dynamic Physical Model of the Vocal Folds

2005 ◽  
Author(s):  
S. Mantha ◽  
L. Mongeau ◽  
T. Siegmund
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Vocal Fold ◽  
High Speed ◽  
Vocal Folds ◽  
Image Correlation ◽  
Strain Component ◽  
Medial Surface ◽  
Superior Surface ◽  
Incomplete Closure

An experimental study of the vibratory deformation of the human vocal folds was conducted. Experiments were performed using model vocal folds [1, 2], Fig. 1, made of silicone rubber implemented into an air supply system, Fig. 2. The material used to cast the model is an isotropic homogeneous material, [3] with a tangent modulus E=5 kPa at ε = 0, i.e. elastic properties similar to those of the human vocal fold cover [4]. The advantages of the use of model larynx systems over the use of excised larynges include easy accessibility to fundamental studies of the vocal fold vibration without invasive testing. Acoustic analysis of voice or electroglottography provide certain insight into voice production processes but optical techniques for the study of vocal fold vibrations have drawn considerable attention. Videoendoscopy, stroboscopy, high-speed photography, and kymography have shown to provide a visual impression of vocal fold dynamics but are limited in providing insight into the fundamental deformation processes of the vocal folds. Quantitative measures of deformation have been conducted through micro-suture techniques but are invasive and allows for measurements of only view image points. Laser triangulation is non-invasive but is limited to only one local measurement point. Here, digital image correlation technique with the software VIC 3D [5] is applied. For the experimental set-up see Fig. 2. The analysis consists of (1) stereo correlation to obtain in-plane displacements and (2) stereo triangulation step to obtain out-of-plane deformation. For the stereo correlation images of the object at two different stages of deformation are compared. A point in the image of the undeformed object is matched with the corresponding point in the deformed stage. “Subsets” of digital images are traced via their gray value distribution from the undeformed reference image to the deformed image. The uniqueness of the matching is enabled by the creation of a speckle pattern on the object’s surface. Here, a white pigment is mixed into the silicone rubber and subsequently black enamel paint is sprayed onto the superior surface of the vocal folds. The stereo triangulation requires two images of the object at each stage of deformation. These are obtained in a single CCD frame by placing a beam splitter in the optical axis between camera and object. These images provide a “left” and “right” view of the model larynx. Thus, the deformed shape of the vocal folds can be obtained. The method allows for noninvasive measurement of the full-field displacement fields. Images of the superior surface of the model larynx are obtained by the use of a high speed digital camera with a frame rate of 3000 frames per second allowing for more than 30 image frames for each vibration cycle. For the 3D digital image correlation analysis two images of the object are obtained for each time instance as a beam splitter is placed in the optical axis between the camera and the model larynx. Phonation frequencies and onset pressure are given in Fig. 3, showing that the model larynx behavior is close to actual physiological data. Figs 4(a) and (b) provide superior views of the model larynx at maximum glottal opening and at glottal closure, respectively. As one example of measured strain fields, Figs 5(a) and (b) depict the distributions of the transverse strain component, on the glottal surface in a contour plot on the deformed superior surface. The knowledge of the distribution of this strain component is relevant to the assessment of the impact of vocal fold collision on potential tissue damage. In the position of maximum opening the vocal folds are deformed by a combination of a bulging-type deformation and the opening movement. At this time instance, the transverse strains at the medial surface are found to be negative, an indication of Poisson’s deformation. During the closing stage, vocal folds collide and simultaneously a mode 3 vibration pattern emerges. Closure of the glottal opening is not complete and two incomplete closure areas are formed during the closure stage. These open areas are located at the anterior and posterior ends of the model larynx, see Fig. 4(b). The finding of this type of incomplete closure is agreement with both actual glottal measurements [6] and 3D finite element simulations of [7]. Transverse strains during that stage are now positive and considerably larger that during the opening stage. Finally, Fig. 6 depicts the time evolution of the out of plane displacements along the medial surface for the closing phase and Fig. 7 depicts the maximum values of the longitudinal strain (at the coronal section of the medial surface) in dependence of the flow rate. These examples of measurements indicate that the DIC method is promising for studies of vocal fold dynamics.

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