Comparison of Strain Rosettes and Digital Image Correlation for Measuring Vertebral Body Strain

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Hannah Gustafson ◽  
Gunter Siegmund ◽  
Peter Cripton
Keyword(s):  
Digital Image Correlation ◽  
Vertebral Body ◽  
Digital Image ◽  
Testing Machine ◽  
Image Correlation ◽  
Principal Strain ◽  
Materials Testing ◽  
Strain Gages ◽  
Strain Rosette ◽  
The Mean

Strain gages are commonly used to measure bone strain, but only provide strain at a single location. Digital image correlation (DIC) is an optical technique that provides the displacement, and therefore strain, over an entire region of interest on the bone surface. This study compares vertebral body strains measured using strain gages and DIC. The anterior surfaces of 15 cadaveric porcine vertebrae were prepared with a strain rosette and a speckled paint pattern for DIC. The vertebrae were loaded in compression with a materials testing machine, and two high-resolution cameras were used to image the anterior surface of the bones. The mean noise levels for the strain rosette and DIC were 1 με and 24 με, respectively. Bland–Altman analysis was used to compare strain from the DIC and rosette (excluding 44% of trials with some evidence of strain rosette failure or debonding); the mean difference ± 2 standard deviations (SDs) was −108 με ± 702 με for the minimum (compressive) principal strain and −53 με ± 332 με for the maximum (tensile) principal strain. Although the DIC has higher noise, it avoids the relatively high risk we observed of strain gage debonding. These results can be used to develop guidelines for selecting a method to measure strain on bone.

Validation of Digital Image Correlation Techniques for Strain Measurement in Biomechanical Test Models

2013 ◽  
Author(s):  
Renee D. Rogge ◽  
Scott R. Small ◽  
Derek B. Archer ◽  
Michael E. Berend ◽  
Merrill A. Ritter
Keyword(s):  
Aluminum Alloy ◽  
Digital Image Correlation ◽  
Polyurethane Foam ◽  
Digital Image ◽  
Measurement Techniques ◽  
Image Correlation ◽  
Principal Strain ◽  
Strain Gages ◽  
Full Field ◽  
Strain Measurements

Many previous biomechanical studies of bone and bone substitutes have estimated strains in these materials using strain gages. The purpose of this study was to compare digital image correlation (DIC) strain measurements to those obtained from strain gages in order to assess the applicability of DIC technology to common biomechanical testing scenarios. Compression and bending tests were conducted on aluminum alloy, polyurethane foam, and laminated polyurethane foam specimens. Results showed no significant differences in the principal strain values (or the variances) between strain gage and DIC measurements on the aluminum alloy and laminated polyurethane foam specimens. There were significance differences between the principal strain measurements of the non-laminated polyurethane foam specimens, but the deviation from the theoretical results was similar for both measurement techniques. In summary, DIC techniques provide similar results to those obtained from strain gages and also provide full field strain results.

The Analysis of Different Stochastic Patterns during Loading in Plastic Area Using DIC Method

2014 ◽  
Vol 611 ◽  
pp. 490-495
Author(s):  
Martin Schrötter ◽  
Martin Hagara ◽  
Matúš Kalina
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Correlation Method ◽  
Mean Value ◽  
Image Correlation ◽  
Black And White ◽  
Unloaded State ◽  
Measured Deformation ◽  
The Mean ◽  
Estimated Error

The aim of this article is to present the influence of stochastic pattern on results accuracy of digital image correlation method in plastic areas. The various types of stochastic patterns were applied on testing specimens which were then tensioned. There was correlated the intensity of black and white color (denoted as grey value) dispersed on a specimen, then the mean value of estimated error for unloaded state as well as state of highest measured deformation and finally the amount of non-correlated facets. Also the maximal deformation of specimens was compared by which the damage of stochastic pattern emerged.

scholarly journals Experimental and Numerical Investigations of Thin-Walled Stringer-Stiffened Panels Welded with RFSSW Technology under Uniaxial Compression

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1785 ◽  
Author(s):  
Andrzej Kubit ◽  
Tomasz Trzepiecinski ◽  
Łukasz Święch ◽  
Koen Faes ◽  
Jan Slota
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Testing Machine ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Stiffened Panels ◽  
Friction Stir ◽  
Uniaxial Tensile Testing ◽  
First Case ◽  
Thin Walled

Many aircraft structures are thin walled and stringer-stiffened, and therefore, prone to a loss of stability. This paper deals with accurate and validated stability analysis of the model of aircraft skin under compressive loading. Both experimental and numerical analyzes are conducted. Two different methods of joining panel elements are considered. In the first case, the panel is fabricated using rivets. In the second variant, the refill friction stir spot welding technique is used. Both types of panels are loaded in axial compression in a uniaxial tensile testing machine. The geometrically and physically nonlinear finite element analyzes of the panels were carried out in ABAQUS/Standard. The Digital Image Correlation measurement system ARAMIS has been utilized to monitor the buckling behavior and failure mode in the skin-stringer interface of the stiffened panels. The results of experiments and the digital image correlation system are presented and compared to the numerical simulations.

scholarly journals The use of charge-coupled device cameras for characterizing the mean deflected shape of an aerospace panel during broadband excitation

2018 ◽  
Vol 54 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Elias Lopez-Alba ◽  
Christopher M Sebastian ◽  
William JR Christian ◽  
Eann A Patterson
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
High Volume ◽  
Random Excitation ◽  
Frame Rate ◽  
Image Correlation ◽  
Charge Coupled Device ◽  
The Mean ◽  
Standard Frame

In vibration experiments demanding long-duration measurements, traditional point-wise techniques are often employed, despite the availability of high-speed digital image correlation. This is due to the high volume of images generated by the latter technique, which limit acquisition times and lengthen post-processing times. In this experimental investigation, it is demonstrated that standard frame rate charge-coupled device cameras yield results for the mean deflected shape of a reinforced aerospace panel subject to a random broadband excitation between 0 and 800 Hz that are not statistically different to those from high-speed cameras. The images from both types of camera were processed using digital image correlation to generate out-of-plane displacement maps, which were then decomposed using Chebyshev descriptors for ease of comparison and to determine the mean deflected shape. The results indicate that, with appropriate sampling rates and durations, standard frame rate charge-coupled device cameras can be used to study broadband random excitation behavior of structures when mean behavior needs to be characterized over long time scales compared to the excitation wavelengths. This is contrary to accepted procedures, but offers comparable accuracy with substantially reduced computational resources compared to using high-speed cameras, as well as effectively unlimited data acquisition periods, which is useful in condition monitoring, for example.

Digital Image Correlation Test System with Automatic Transmission for Quasi-Brittle Material

2013 ◽  
Vol 405-408 ◽  
pp. 2515-2519
Author(s):  
Hong Liang Yue ◽  
Chun Hui Zhang ◽  
Yan Wang
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Automatic Transmission ◽  
Testing Machine ◽  
Test System ◽  
Image Correlation ◽  
Displacement Discontinuity ◽  
Laptop Computer ◽  
Image Capture ◽  
Convolution Algorithm

To realize the automatic transmission for present digital image capture test system, a new system which consists of laptop computer, camera, fixing device and mechanical testing machine was presented and designed. The Monitor software, which was developed using MATLAB to realize automatic transmission function for the system, includes slow and high speed. The general stage and key stage for quasi-brittle materials can be effectively captured by the software. With MATLAB, the digital image correlation software (DIC) was developed. In DIC the first image is used as the base image. The images are sorted by photographing time (or file name), and the listing file is generated. The grid is drawn on the base image to divide the area into ‘facets’, the size of which can be adjusted between 1pixel and 100 pixels. Based on fast Fourier transform and convolution algorithm, the image comparison is realized and the deformation of the material is calculated. The designed system is applied to the compression test of a concrete specimen, and the results show that the system realizes automatic transmission image capture, and calculates accurate displacement. The displacement distribution is uniform in linear elastic stage, and varies in yielding stage. This is mostly due to localized failure and displacement discontinuity.

Buckling Measurement of Cylindrical Shells by Digital Image Correlation Method

2013 ◽  
Author(s):  
Tzu-Yu Kuo ◽  
Wei-Chung Wang ◽  
Chun-I Chu ◽  
Jia-He Chen ◽  
Te-Heng Hung ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Measurement ◽  
Cylindrical Shells ◽  
Compressive Load ◽  
Correlation Method ◽  
Tensile Tests ◽  
Image Correlation ◽  
Strain Gages ◽  
Full Field

In this study, deformation of cylindrical shells under axial compressive load was studied and characterized by a noncontact detection technique, called digital image correlation (DIC). As opposed to commonly used strain gages for measuring structure strains at specific points, the DIC method can render not only 2D but also 3D full-field measurements for strain as well as structure deformation. The accuracy of strain measurement obtained using the DIC method was carefully validated by following ASTM standard E8 for strain measurement using strain gages in tensile tests. The DIC technique provided convenient measurements for characterizing the buckling behaviors of defective cylindrical shell samples. This study has engineering implications for providing 3D strain and deformation analyses to ensure structure reliability and safety.

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