DIC Challenge: Developing Images and Guidelines for Evaluating Accuracy and Resolution of 2D Analyses

With the rapid spread in use of Digital Image Correlation (DIC) globally, it is important there be some standard methods of verifying and validating DIC codes. To this end, the DIC Challenge board was formed and is maintained under the auspices of the Society for Experimental Mechanics (SEM) and the international DIC society (iDICs). The goal of the DIC Board and the 2D–DIC Challenge is to supply a set of well-vetted sample images and a set of analysis guidelines for standardized reporting of 2D–DIC results from these sample images, as well as for comparing the inherent accuracy of different approaches and for providing users with a means of assessing their proper implementation. This document will outline the goals of the challenge, describe the image sets that are available, and give a comparison between 12 commercial and academic 2D–DIC codes using two of the challenge image sets.     

Real-time 3D Digital Image Correlation for Large Deformation and Rotation Measurements Based on a Deformation Transfer Scheme

Experimental Mechanics - With the recent increase in digital image correlation (DIC) applications, it is important to improve the computational efficiency of DIC and realize the closed loop control...     

Combining Image Compression with Digital Image Correlation

Experimental Mechanics - Digital image correlation (DIC) is a powerful experimental technique to determine displacement and strain fields. DIC methods usually require a large number of high...     

A Robust-to-Noise Deconvolution Algorithm to Enhance Displacement and Strain Maps Obtained with Local DIC and LSA

Experimental Mechanics - Digital Image Correlation (DIC) and Localized Spectrum Analysis (LSA) are two techniques available to extract displacement fields from images of deformed surfaces marked...     

Quantifying the Effectiveness of Patterning,Test Conditions,and DIC Parameters for Characterization of Plastic Strain Localization

Experimental Mechanics - Digital image correlation, commonly referred to as DIC, enables full-field measurements of displacements and strains from a surface of interest. While DIC offers major...     

Smart Digital Image Correlation Patterns via 3D Printing

Experimental Mechanics - Digital Image Correlation (DIC) is a popular experimental technique for measuring full-field deformations in materials. Accurate motion and displacement field...     

Augmented Lagrangian Digital Image Correlation

Experimental Mechanics - Digital image correlation (DIC) is a powerful experimental technique for measuring full-field displacement and strain. The basic idea of the method is to compare images of...     

Modal Analysis Using a Virtual Speckle Pattern Based Digital Image Correlation Method: An Application for an Artificial Flapping Wing

Experimental Mechanics - A conventional three-dimensional digital image correlation (DIC) based on painted speckle patterns has been used widely as a non-contact measurement method to study modal...     

Time-Resolved Digital Image Correlation in the Scanning Electron Microscope for Analysis of Time-Dependent Mechanisms

Experimental Mechanics - Background: Advancements in the Digitial Image Correlation (DIC) technique over the past decade have greatly improved spatial resolution. However, many processes, such as...     

Cool,Dry, Nano-scale DIC Patterning of Delicate,Heterogeneous, Non-planar Specimens by Micro-mist Nebulization

Experimental Mechanics - Background: Application of patterns to enable high-resolution Digital Image Correlation (DIC) at the small scale (μm/nm) is known to be very challenging as techniques...     

The Effect of the Ill-posed Problem on Quantitative Error Assessment in Digital Image Correlation

Experimental Mechanics - This work explores the effect of the ill-posed problem on uncertainty quantification for motion estimation using digital image correlation (DIC) (Sutton et al. [2009]). We...     

A Frequency Domain Error Model for Local 2D-DIC

Experimental Mechanics - Digital image correlation (DIC) has become a superior tool for surface deformation measurement so far. In order to improve its measurement accuracy, different error models...     

数字图像相关方法若干关键问题研究进展

本文报道了作者及其所在课题组近期在数字图像相关(DIC)测量方法上取得的重要研究进展。主要包括:(1)通过对DIC方法中反向组合高斯-牛顿算法的理论误差分析,提出了新的理论误差公式,进一步证明了反向组合高斯-牛顿算法在提高计算速度和测量精度方面的综合优势;(2)采用提出的理论误差公式,发展了数字散斑场的优化及制作方法,保证了测量结果的一致性和正确性;(3)基于相机阵列和图像拼接技术,发展了超分辨率数字图像相关方法,大大提高了DIC测量方法的应变测量分辨率;(4)提出了大视场条件下的三维系统标定方法,实现了三维测量系统的外参实时标定和多相机测量系统中相机位姿的自动矫正;(5)研制了便携式原位三维测量仪和多尺度DIC测量系统,实现了三维实时数字图像相关测量,进一步满足了DIC方法在工业在线检测和医学领域中的应用需求。     

Interlaboratory Study of Digital Volume Correlation Error Due to X-Ray Computed Tomography Equipment and Scan Parameters: an Update from the DVC Challenge

Experimental Mechanics - The quality of Digital Volume Correlation (DVC) full-field displacement measurements depends directly on the characteristics of the X-ray Computed Tomography (XCT)...     

Adaptive Rotated Gaussian Weighted Digital Image Correlation (RGW-DIC) for Heterogeneous Deformation Measurement

Background

Digital image correlation (DIC) has advanced to become a flexible, reliable and fast optical method for the measurement of non-contact and full-field surface deformation. However, the accuracy of existing methods in measuring heterogeneous deformation fields—especially for the high gradient strain field – can be improved.

Objective

In state-of-art local DIC applications, several methods have been put forward to adapt a subset to unknown deformation. Although improvements in performance using these methods are obtained, results are still ungratified for severely heterogeneous deformation such as the Star 2 and Star 5 images from DIC Challenge 2.0.

Methods

In this paper, a rotated Gaussian weighted zero-mean normalized sum of squared difference (RGW-ZNSSD) criterion function is proposed as the basis for RGW-DIC subset size adaptation. RGW-DIC can automatically determine the optimum weight distribution, hence self-adaptivity in subset size and orientation are achieved simultaneously.

Results

The effectiveness of the proposed RGW-DIC is verified using DIC-challenge 2.0 images and simulated sinusoidal deformation images. Results reveal that the adaptively determined subset weight distribution can significantly improve the accuracy of heterogeneous deformation measurement compared with traditional DIC and DIC with isotropic Gaussian weight functions.

Conclusions

The proposed RGW-DIC can be applied to unknown severely heterogeneous deformation measurement.

     

Numerical and Experimental Study of the Spatial Stress Distribution on the Cornea Surface During a Non-Contact Tonometry Examination

Experimental Mechanics - The determination of biomechanical properties of the cornea by a non-contact tonometry (NCT) examination requires a precise knowledge of the air puff generated in the...     

Online Stress Monitoring Technique Based on Lamb-wave Measurements and a Convolutional Neural Network Under Static and Dynamic Loadings

Experimental Mechanics - This paper presents the development of an online stress monitoring technique based on Lamb-wave measurements and a convolutional neural network (CNN) for metallic...     

Effects of Strain Path Changes on the Kinematics and the Intrinsic Dissipation Accompanying PLC Bands in Al-Mg Alloys

Experimental Mechanics - Plastic instabilities, such as the Portevin-Le Chatelier (PLC) effect, reduce material ductility and induce surface roughness during sheet metal forming. The formation and...     

Tracking Defects and Microstructural Heterogeneities in Meso-Scale Tensile Specimens Excised from Additively Manufactured Parts

Experimental Mechanics - The commercialization of additive manufacturing (AM) is underway in the aerospace and biomedical device industries [1, 2]. However, most metal parts produced by AM are...     

Correction to: Spatial DIC Errors due to Pattern-Induced Bias and Grey Level Discretization

Experimental Mechanics - The original article has been corrected to include labels on Figs. 4 and 9 and corrections made to the Eqs. (3), (4) and (8).