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Columbia, SC, United States

Tofts A.,Correlated Solutions, Inc.
Laser Focus World | Year: 2012

Digital image correlation (DIC) is a non-contact measurement technique that uses high-resolution machine-vision digital cameras to accurately measure surface deformation in two or three dimensions. DIC eliminates lengthy process by measuring the displacements and strains over the entire surface of the specimen so precise gauge placement is not required. The end result is full-field 3D displacement and strain measurement of the specimen's surface. Validating theoretical computer models is an essential step to designing a quality product with an efficient use of materials. DIC makes this process much faster by providing richer data at higher rates. Because of its noncontact measurement principle and high spatial resolution, DIC can provide unprecedented measurement capabilities at high loading rates. DIC requires very precise camera synchronization to provide the tightest possible tolerances for spatial and temporal displacement calculations.

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2009

Development of a software tool capable of predicting crack growth in structures with complex geometries for accurate structural life predictions and residual strength assessment is proposed. The custom crack growth simulation tool, CRACK3D, will be used as the basic code for further development and implementation. First, further enhancement of the CRACK3D module for computational geometry and topology will be performed so that CRACK3D can handle most of geometric features present in modern aircraft structures. Second, CRACK3D will be modified to contain built-in advanced computing techniques, including high performance computing FORTRAN/C++ coding, parallel computation option for running on distributed memory system and shared memory systems. Third, the three-dimensional virtual crack closure technique, 3D VCCT, will be used to calculate stress intensity factors for complex crack geometries under arbitrary mixed mode loading conditions. Fourth, the alternate superposition-based method will be used to take into account the effect of residual stress on fatigue crack growth rates. This method is simple and relatively accurate. A crack closure based approach can also be implemented for improving the accuracy of the alternate superposition-based method if accuracy becomes a concern. Finally, experimental validation of the capabilities will be performed using either existing literature or simple coupon experiments. BENEFIT: Successful completion of the proposed effort provides the foundation for conversion of CRACK3D into a form that would provide AF personnel with an efficient and effective simulation tool for assessing selected flaw criticality. Specifically, the following results are anticipated. (1)A finite element formulation of VCCT with 10-noded tetrahedral elements, implemented in CRACK3D, for simulating three-dimensional crack growth using unstructured meshes. (2)A program module for re-meshing local regions around critical crack fronts and containing internal material boundaries, for modeling crack growth in multi-material structures. (3)A program module of computational geometry and topology for updating structural geometry and topology due to crack growth in structures with arbitrary, complex geometries.(4) A theoretical model and simulation methodology of fatigue crack growth in structures under mixed mode loading conditions, implemented in CRACK3D, for prediction of fatigue crack path under general loading conditions, and (5) An enhanced software package, CRACK3D, for calculation of stress intensity factors under mixed mode loading conditions and fatigue crack growth simulation, in addition to simulation of stable tearing crack growth. Taken together, completion of these developments provides the foundation for future Phase II efforts to make the 3D fracture analysis methodology both effective and relatively easy to use. The modified version of the software package CRACK3D is intended for commercialization at the completion of the Phase II effort. To achieve this goal, various strategies will be used to publicize CRACK3D and to demonstrate its capabilities and applications. Included in this effort will be development of a relatively easy-to-use interface to allow users to utilize the power of the methodology with minimal FE meshing effort.

Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase I | Award Amount: 119.26K | Year: 2010

The availability of ultra-high speed imaging equipment capable of frame rates up to 1 GHz has opened the potential for measurement of full-field three-dimensional deformation data during highly dynamic events by employing the digital image correlation method. However, due to the characteristics of ultra-high speed cameras as well as experimental conditions during ballistic events, the application of digital image correlation is not straightforward. We propose to develop novel image correlation algorithms and data pre- and post-processing technologies that address these issues and utilize the image data from ultra-high speed sensors to its optimal potential. Furthermore, we propose to develop an improved ultra-high speed image sensor that can provide greatly reduced bias in practical applications as well as enhanced light sensitivity. These developments will ultimately result in a full-field deformation measurement system capable of acquiring data at rates of 1 GHz with an accuracy comparable to current quasi-static stereo image correlation systems.

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2015

ABSTRACT:A cooperative small business and university research and development program is proposed to begin development of a robust, non-contacting, digital image correlation based, full-field strain measurement system for high temperature applications. The Phase I studies will demonstrate that a robust high temperature digital image correlation system (HTDICS) can be developed that is capable of acquiring full field deformation measurements (a) over a range of temperatures from room temperature to 1800F and higher, (b) over the same range of temperatures while subjected to different loading rates, including high levels of broadband acoustic loading and (c) at near real-time or at real time rates for immediate visualization of the deformation fields and potentially control of portions of the experiment.BENEFIT:Development of an HTDICS capable of acquiring full-field measurements at high temperature in quasi-real time will provide unprecedented ability for investigators to monitor progressive damage accumulation. This will improve understanding of the evolution processes prevalent in modern material systems subjected to aggressive environmental conditions, resulting in a more efficient (e.g. cost effective) life cycle testing environment without service interruptions. Furthermore, if HTDICS measurements can be acquired in real time, then it offers the potential for real-time control of experiments so that the environment can be altered in response to material changes in a manner that would increase understanding of the damage progression processes. Of course, the ability to acquire real time deformation measurements has broader implications regarding the ability to perform experiments with feedback control based on direct measurements of material response, a possibility that has hitherto been unattainable. Finally, when a structure (e.g. hypersonic vehicle/structure) is subjected to higher rate excitation/loading, then the ability to obtain near real time measurements provides investigators with the ability to modify the excitation so that structural failure does not occur.

Apparatuses and methods related to measuring motion or deformations of vibrating objects are provided. A plurality of images of an object are acquired in synchronization with a plurality of determined times of interest during oscillation of the object. The plurality of images are compared to obtain one or more quantities of interest of the object based at least in part on the plurality of images.

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