- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Correlative optical and X‐ray imaging of strain evolution during Double Torsion Fracture Toughness measurements in shale
摘要： Mode-I Fracture Toughness, KIc, was measured in six shale materials using the double torsion technique. During loading, crack propagation was imaged both using twin optical cameras, and with fast X-Ray radiograph acquisition. Samples of Bowland, Haynesville, Kimmeridge, Mancos, Middlecliff and Whitby shales were tested in a range of orientations. The measured fracture toughness values were found to be in good agreement with existing literature values. The two imaging techniques improve our understanding of local conditions around the fracture tip, through in-situ correlation of mechanical data, inelastic zone size and fracture-tip velocity. The optical Digital Image Correlation (DIC) technique proved useful as a means of determining the validity of individual experiments, by identifying experiments during which strains had developed in the two ”rigid” specimen halves. Strain maps determined through DIC of the optical images suggest that the scale of the inelastic zone is an order of magnitude smaller than the classically used approximation suggests. This smaller damage region suggests a narrower region of enhanced permeability around artificially generated fractures in shales. The resolvable crack-tip was tracked using radiograph data and found to travel at a velocity around 470 m.s?1 during failure, with little variation in speed between materials and orientations. Fracture pathways in the bedding parallel orientations were observed to deviate from linearity, commonly following layer boundaries. This suggests that while a fracture travelling parallel to bedding may travel at a similar speed to a bedding perpendicular fracture, it may have a more tortuous pathway, and therefore access a larger surface area.
关键词： shale materials,fracture tip velocity,Double-torsion fracture toughness,optical digital image correlation,crack-mouth opening displacement,radiograph imaging
更新于2025-09-09 09:28:46
-
Advanced Materials for Electromagnetic Shielding (Fundamentals, Properties, and Applications) || Mechanical Performance Characterization of EMI Shielding Materials Using Optical Experimental Techniques
摘要： In this chapter, the full field optical experimental methods for characterizing the mechanical performance of EMI shielding materials have been discussed. Interest in this type of physical problem is motivated by its importance in many practical applications. One major disadvantage of the use of optical techniques in characterizing the mechanical performance of EMI shielding materials is their full field and noncontact with the materials. The information outlined in this chapter may help researchers and engineers in their study of the unknown features of related complex systems for technological applications in characterizing EMI shielding materials.
关键词： EMI shielding materials,photoelastic method,digital gradient sensing,mechanical performance,moiré interferometry,digital image correlation,coherent gradient sensing,optical experimental techniques
更新于2025-09-04 15:30:14
-
Digital Image Correlation for discontinuous displacement measurement using subset segmentation
摘要： Deformation measurement is normally achieved by using Digital Image Correlation (DIC) technique when deformation is not discontinuous. However, the presence of discontinuities makes the deformation process very challenging and DIC fails. An innovative technique is proposed in this study which splits the subset (segment) of an image into multiple parts and use segmented subset of the image for correlation process. The performance of the proposed technique is evaluated using di?erent experiments where di?erent types of discontinuities are introduced in the deformation process at di?erent angles and having di?erent discontinuity opening sizes. The obtained results are compared with the recently proposed Discontinuous Digital Image Correlation (DDIC) technique. The results show that the proposed technique is more reliable and having high accuracy which reaches upto 1/100th of a pixel under favorable circumstances.
关键词： Deformation measurement,Discontinuous displacement measurement,Digital image correlation,Reconstruction of displacement ?elds,DIC,Subset segmentation
更新于2025-09-04 15:30:14
-
Extracting Displacement and Strain Fields from Checkerboard Images with the Localized Spectrum Analysis
摘要： The performance of white-light full-field measurement methods strongly depends on the nature of the pattern used to mark the surface on which displacements and strains are measured. Finding optimized patterns is therefore a topical question. The aim of this study is to examine the case of the checkerboard pattern. It is first shown that this periodic pattern can be processed with a Fourier-based technique such as LSA. Experiments are then carried out to compare the noise level in displacement and strain maps obtained by processing classic 2D grid and checkerboard images. The conclusion is that the noise level observed in displacement and strain maps is significantly lower with a checkerboard than with a classic 2D grid. A notched specimen is finally tested to illustrate that very low strain levels can be measured with checkerboard patterns.
关键词： Grid method,Checkerboard,Localized spectrum analysis,Optimal pattern,Digital image correlation,Heteroscedastic noise,Metrology,Pattern optimization,Windowed Fourier transform
更新于2025-09-04 15:30:14
-
Novel Boundary Edge Detection for Accurate 3D Surface Profilometry Using Digital Image Correlation
摘要： Digital image correlation (DIC) has emerged as a popular full-field surface profiling technique for analyzing both in-plane and out-of-plane dynamic structures. However, conventional DIC-based surface 3D profilometry often yields erroneous contours along surface edges. Boundary edge detection remains one of the key issues in DIC because a discontinuous surface edge cannot be detected due to optical diffraction and height ambiguity. To resolve the ambiguity of edge measurement in optical surface profilometry, this study develops a novel edge detection approach that incorporates a new algorithm using both the boundary subset and corner subset for accurate edge reconstruction. A pre-calibrated gauge block and a circle target were reconstructed to prove the feasibility of the proposed approach. Experiments on industrial objects with various surface reflective characteristics were also conducted. The results showed that the developed method achieved a 15-fold improvement in detection accuracy, with measurement error controlled within 1%.
关键词： automated optical inspection (AOI),edge detection,digital image correlation (DIC),random speckle images,surface profilometry
更新于2025-09-04 15:30:14