scholarly journals The Application of Digital Image Correlation for Measuring Residual Stress by Incremental Hole Drilling

2008 ◽  
Vol 13-14 ◽  
pp. 65-73 ◽  
Author(s):  
Jerry D. Lord ◽  
David Penn ◽  
P. Whitehead
Keyword(s):  
Residual Stress ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Gauge ◽  
Biaxial Stress ◽  
Image Correlation ◽  
Hole Drilling ◽  
Validation Data ◽  
Strain Fields ◽  
Incremental Hole Drilling

The measurement of residual stress using the incremental hole drilling is well established, but the main limitations with the conventional strain gauge approach are the requirements for surface preparation, the need for accurate alignment and drilling, the restricted range of hole geometries commensurate with the specific gauge designs, and the limited range of strain data averaged over the footprint of the strain gauge grid. Recent attempts to extend the method have seen the application of full field optical techniques such as electronic speckle pattern interferometry and holographic interferometry for measuring the strain fields around the hole, but these methods are sensitive to vibration and this limits their practical use to controlled laboratory environments. There are significant potential benefits therefore of using a more robust technique based on Digital Image Correlation (DIC), and work is presented in this study on the development of the method for measuring surface displacements and strain fields generated during incremental hole drilling. Some of the practical issues associated with the technique development, including the optimization of applied patterns, the development of the optical system and integration with current hole drilling equipment are discussed, and although measurements are only presented for a single load case - the equi-biaxial stress state introduced during shot peening - the novel aspect of this work is the integration of DIC measurements with incremental drilling and an application of the Integral Method analysis to measure the variation of residual stress with depth. Validation data comparing results from conventional strain gauge data and FE models is also presented.

Development of a New Method for Residual Stress Analysis on Fiber Reinforced Plastics with Use of Digital Image Correlation

2017 ◽  
Vol 742 ◽  
pp. 660-665 ◽  
Author(s):  
Thomas Rief ◽  
Joachim Hausmann ◽  
Nicole Motsch
Keyword(s):  
Residual Stress ◽  
Digital Image Correlation ◽  
Residual Stresses ◽  
Stress Analysis ◽  
Digital Image ◽  
Image Correlation ◽  
Strain Gauges ◽  
Hole Drilling ◽  
Drilling Process ◽  
Residual Stress Analysis

In scope of the investigation of residual stresses the hole drilling method is an accepted method. The method is though not applicable for materials with high anisotropic behavior. Therefore a new algorithm is derived which allows the calculation of residual stresses in laminates made of unidirectional layers. Also the strain gauges deliver only strains on the areas where the strain gauges are applied. With the use of a high resolution imaging system and digital image correlation this area and the informational output can be widely improved. First, the derivation of the residual stress analysis algorithm is presented. For this an adequate finite element model, which is modeling the cooldown process as well as the drilling process, is set up and the surface strains are extracted. Based on this information an algorithm is derived and presented. Within the derivation a change of the layup, a possible change of the cooldown process and a variation of the drilling steps can be investigated. In consequence the input parameters of the algorithm can vary dependent on these factors. Second, the new optical testing setup with refinements to be able to measure the small deformations within micro-strains on the specimen’s surface is prepared and the concept presented. To solve the problem of casting shadows of the drill a special camera setup is being used.

scholarly journals Design of a Unique Device for Residual Stresses Quantification by the Drilling Method Combining the PhotoStress and Digital Image Correlation

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 314
Author(s):  
Miroslav Pástor ◽  
Martin Hagara ◽  
Ivan Virgala ◽  
Adam Kaľavský ◽  
Alžbeta Sapietová ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Experimental Testing ◽  
Digital Processing ◽  
Image Correlation ◽  
Optical Systems ◽  
Hole Drilling ◽  
Element Analysis ◽  
Thin Specimen ◽  
Comparison Of The Results

This paper presents a uniquely designed device combining the hole-drilling technique with two optical systems based on the PhotoStress and digital image correlation (DIC) method, where the digital image correlation system moves with the cutting tool. The authors aimed to verify whether the accuracy of the drilled hole according to ASTM E837-13a standard and the positioning accuracy of the device were sufficient to achieve accurate results. The experimental testing was performed on a thin specimen made from strain sensitive coating PS-1D, which allowed comparison of the results obtained by both methods. Although application of the PhotoStress method allows analysis of the strains at the edge of the cut hole, it requires a lot of experimenter’s practical skills to assess the results correctly. On the other hand, the DIC method allows digital processing of the measured data. However, the problem is not only to determine the data at the edge of the hole, the results also significantly depend on the smoothing levels used. The quantitative comparison of the results obtained was performed using finite element analysis.

scholarly journals DIC (Digital Image Correlation) method in the research of RC beams strengthened with PBO-FRCM materials

2019 ◽  
Vol 97 ◽  
pp. 03008 ◽  
Author(s):  
Dorota Marcinczak ◽  
Tomasz Trapko
Keyword(s):  
Composite Materials ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Gauge ◽  
Concrete Beam ◽  
Correlation Method ◽  
Reinforced Concrete Beam ◽  
Image Correlation ◽  
Strain Gauges ◽  
Reference Image

The article presents tests of a reinforced concrete beam strengthened in a shear with PBO-FRCM composite materials. Measurement of the deformation of the composite was carried out using two methods - with strain gauges and the optical DIC method (Digital Image Correlation). The DIC method consists in taking a series of photographs of the tested object before and during loading. The surface of the tested element must have randomly spaced spots that are applied to the object before measurement. During the study, the cameras monitor the shifting of spots against each other, which in comparison to the reference image before loading gives information about strains and stresses of the tested element. Measurements of deformation of composite materials using strain gauges are difficult to clearly analyse, because the strain gauge is in a specific, limited place, which does not correspond to the work of the entire composite. In addition, the strain gauge tends to break at the place of crack. The article discusses this problem by presenting the results of deformation of PBO-FRCM composite meshes measured in two mentioned ways, their comparison and discussion of results.

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