Surface Discontinuity Detection via Direct Strain Imaging

2013 ◽  
Author(s):  
Athanasios Iliopoulos ◽  
John G. Michopoulos
Keyword(s):  
Biaxial Loading ◽  
Strain Tensor ◽  
Strain Imaging ◽  
Engineering Strain ◽  
New Approach ◽  
Full Field ◽  
Full Field Measurement ◽  
Slant Crack ◽  
Novel Method ◽  
Surface Discontinuity

Direct strain imaging is a recently developed full-field strain measurement method that accomplishes full field measurement of the strain tensor on the surface of a deforming body, by using arbitrarily oriented engineering strain measurements. This new approach doesn’t make any assumption on the compatibility of the strain field and thus it allows for consistent representation of media that may be or may not be discontinuous. In this paper, we present a novel method for detecting whether a discontinuity exists on a deformed body by evaluating the validity of the compatibility conditions over the imaging field. This approach can also be used for quantifying the shape and length of the discontinuity or crack. Synthetic numerical experiments based on the exact solution of a slant crack under biaxial loading were conducted to establish the detectability performance and the associated uncertainty of detection. Very encouraging results were derived indicating that for realistic levels of noise the method was found to be able to detect discontinuities as small as 0.3 mm long with very high confidence.

Performance Analysis and Experimental Validation of the Direct Strain Imaging Method

2013 ◽  
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.

scholarly journals Full-Field Bridge Deflection Monitoring with Off-Axis Digital Image Correlation

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5058
Author(s):  
Long Tian ◽  
Jianhui Zhao ◽  
Bing Pan ◽  
Zhaoyang Wang
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Region Of Interest ◽  
Image Correlation ◽  
New Approach ◽  
Full Field ◽  
Straight Line ◽  
Beam Experiment ◽  
Novel Method

Video deflectometer based on using off-axis digital image correlation (DIC) has emerged as a robust non-contact optical tool for deflection measurements of bridges. In practice, a video deflectometer often needs to measure the deflections at multiple positions of the bridge. The existing 2D-DIC-based measurement methods usually use a laser rangefinder to measure the distance from each point to the camera to obtain the scale factor for the point. It is only suitable for the deflection measurements of a few points since manually measuring distances for a large number of points is time consuming and impractical. In this paper, a novel method for full-field bridge deflection measurement based on off-axis DIC is proposed. Because the bridge is usually a slender structure and the region of interest on the bridge is often a narrow band, the new approach can determine the scale factors of all the points of interest with a spatial straight-line fitting scheme. Moreover, the proposed technique employs reliability-guided processing and a fast initial parameter estimation strategy for real-time and accurate image-matching analysis. An indoor cantilever beam experiment verified the accuracy of the proposed approach, and a field test of a high-speed railway bridge demonstrated the robustness and practicability of the technique.

scholarly journals LiDAR-Based Glass Detection for Improved Occupancy Grid Mapping

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2263
Author(s):  
Haileleol Tibebu ◽  
Jamie Roche ◽  
Varuna De Silva ◽  
Ahmet Kondoz
Keyword(s):  
Laser Scanner ◽  
Point Clouds ◽  
Light Detection And Ranging ◽  
Test Results ◽  
New Approach ◽  
Occupancy Grid ◽  
Laser Scanners ◽  
Novel Method ◽  
Occupancy Grid Mapping ◽  
Cartesian Coordinate

Creating an accurate awareness of the environment using laser scanners is a major challenge in robotics and auto industries. LiDAR (light detection and ranging) is a powerful laser scanner that provides a detailed map of the environment. However, efficient and accurate mapping of the environment is yet to be obtained, as most modern environments contain glass, which is invisible to LiDAR. In this paper, a method to effectively detect and localise glass using LiDAR sensors is proposed. This new approach is based on the variation of range measurements between neighbouring point clouds, using a two-step filter. The first filter examines the change in the standard deviation of neighbouring clouds. The second filter uses a change in distance and intensity between neighbouring pules to refine the results from the first filter and estimate the glass profile width before updating the cartesian coordinate and range measurement by the instrument. Test results demonstrate the detection and localisation of glass and the elimination of errors caused by glass in occupancy grid maps. This novel method detects frameless glass from a long range and does not depend on intensity peak with an accuracy of 96.2%.

scholarly journals Raman and Infrared Thermometry for Microsystems

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
Leslie M. Phinney ◽  
Wei-Yang Lu ◽  
Justin R. Serrano
Keyword(s):  
Data Collection ◽  
Spatial Resolution ◽  
Infrared Imaging ◽  
Silicon On Insulator ◽  
Pixel Size ◽  
Full Field ◽  
Infrared Thermometry ◽  
Full Field Measurement ◽  
Typical Data ◽  
Field Temperature

This paper reports and compares Raman and infrared thermometry measurements along the legs and on the shuttle of a SOI (silicon on insulator) bent-beam thermal microactuator. Raman thermometry offers micron spatial resolution and measurement uncertainties of ±10 K. Typical data collection times are a minute per location leading to measurement times on the order of hours for a complete temperature profile. Infrared thermometry obtains a full-field measurement so the data collection time is on the order of a minute. The spatial resolution is determined by the pixel size, 25 μm by 25 μm for the system used, and infrared thermometry also has uncertainties of ±10 K after calibration with a nonpackaged sample. The Raman and infrared measured temperatures agreed both qualitatively and quantitatively. For example, when the thermal microactuator was operated at 7 V, the peak temperature on an interior leg is 437 K ± 10 K and 433 K ± 10 K from Raman and infrared thermometry, respectively. The two techniques are complementary for microsystems characterization when infrared imaging obtains a full-field temperature measurement and Raman thermometry interrogates regions for which higher spatial resolution is required.

scholarly journals New approach in the application of lignin for the synthesis of hybrid materials

2017 ◽  
Vol 89 (1) ◽  
pp. 161-171 ◽  
Author(s):  
Beata Podkościelna ◽  
Marta Goliszek ◽  
Olena Sevastyanova
Keyword(s):  
Suspension Polymerization ◽  
Nitrogen Adsorption ◽  
Experimental Protocol ◽  
New Approach ◽  
Surface Areas ◽  
Adsorption Data ◽  
Novel Method ◽  
Derivatives Of ◽  
Polymerization Method ◽  
Nitrogen Adsorption Data

AbstractIn this study, a novel method for the synthesis of hybrid, porous microspheres, including divinylbenzene (DVB), triethoxyvinylsilane (TEVS) and methacrylated lignin (L-Met), is presented. The methacrylic derivatives of kraft lignin were obtained by reaction with methacryloyl chloride according to a new experimental protocol. The course of the modification of lignin was confirmed by attenuated total reflectance (ATR-FTIR) and nuclear magnetic resonance (NMR) spectroscopy. The emulsion-suspension polymerization method was employed to obtain copolymers of DVD, TEVS and L-Met in spherical forms. The porous structures and morphologies of the obtained lignin-containing functionalized microspheres were investigated by low-temperature nitrogen adsorption data and scanning electron microscopy (SEM). The microspheres are demonstrated to be mesoporous materials with specific surface areas in the range of 430–520 m2/g. The effects of the lignin component on the porous structure, shape, swelling and thermal properties of the microspheres were evaluated.

scholarly journals Enhancement of Region of Interest CT Reconstructions through Multimodal Data

2018 ◽  
Vol 4 (1) ◽  
pp. 331-335
Author(s):  
David Schote ◽  
Tim Pfeiffer ◽  
Georg Rose
Keyword(s):  
Substantial Reduction ◽  
Region Of Interest ◽  
Proof Of Concept ◽  
Multimodal Data ◽  
New Approach ◽  
Full Field ◽  
Lack Of Information ◽  
Ct Data ◽  
Flight Measurements

AbstractComputed tomography (CT) scans are frequently used intraoperatively, for example to control the positioning of implants during intervention. Often, to provide the required information, a full field of view is unnecessary. I nstead, the region-of-interest (ROI) imaging can be performed, allowing for substantial reduction in the applied X-ray dose. However, ROI imaging leads to data inconsistencies, caused by the truncation of the projections. This lack of information severely impairs the quality of the reconstructed images. This study presents a proof-of-concept for a new approach that combines the incomplete CT data with ultrasound data and time of flight measurements in order to restore some of the lacking information. The routine is evaluated in a simulation study using the original Shepp-Logan phantom in ROI cases with different degrees of truncation. Image quality is assessed by means of normalized root mean square error. The proposed method significantly reduces truncation artifacts in the reconstructions and achieves considerable radiation exposure reductions.

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