Tensile Test for Polymer Plastics with Extreme Large Elongation Using Quad-Camera Digital Image Correlation

Xie, Xin; Zeng, Deliang; Li, Junrui; Dahl, Jeffrey; Zhao, Qiancheng; Yang, Lianxiang

doi:10.4271/2016-01-0418

Cited by 10 publications

(1 citation statement)

References 12 publications

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“…Compared to laser vibrometers, digital cameras are low-cost and capable to make simultaneous full-field measurements. Recently, high resolution and high-speed (frame rate) digital video cameras in conjunction with stereo-photogrammetry approaches, such as 3D digital image correlation (3D DIC) and 3D point tracking (3DPT), have been utilized to perform modal analysis and strain analysis on large-scale industrial structures [27][28][29][30][31][32][33][34]. Although 3D DIC and 3DPT provide smooth mode shapes with high accuracy, these methods generally require a speckle pattern or high contrast markers mounted or painted on the surface of the structure.…”

Section: Introductionmentioning

confidence: 99%

Vibration-based damage detection in wind turbine blades using Phase-based Motion Estimation and motion magnification

Sarrafi

Mao

Niezrecki

et al. 2018

Journal of Sound and Vibration

199

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Vibration-based Structural Health Monitoring (SHM) techniques are among the most common approaches for structural damage identification. The presence of damage in structures may be identified by monitoring the changes in dynamic behavior subject to external loading, and is typically performed by using experimental modal analysis (EMA) or operational modal analysis (OMA). These tools for SHM normally require a limited number of physically attached transducers (e.g. accelerometers) in order to record the response of the structure for further analysis. Signal conditioners, wires, wireless receivers and a data acquisition system (DAQ) are also typical components of traditional sensing systems used in vibration-based SHM. However, instrumentation of lightweight structures with contact sensors such as accelerometers may induce mass-loading effects, and for large-scale structures, the instrumentation is labor intensive and time consuming. Achieving high spatial measurement resolution for a large-scale structure is not always feasible while working with traditional contact sensors, and there is also the potential for a lack of reliability associated with fixed contact sensors in outliving the life-span of the host structure. Among the state-of-the-art noncontact measurements, digital video cameras are able to rapidly collect high-density spatial information from structures remotely. In this paper, the subtle motions from recorded video (i.e. a sequence of images) are extracted by means of Phase-based Motion Estimation (PME) and the extracted information is used to conduct damage identification on a 2.3-meter long Skystream® wind turbine blade (WTB). The PME and phased-based motion magnification approach estimates the structural motion from the captured sequence of images for both a baseline and damaged test cases on a wind turbine blade. Operational deflection shapes of the test articles are also quantified and compared for the baseline and damaged states. In addition, having proper lighting while working with high-speed cameras can be an issue, therefore image enhancement and contrast manipulation has also been performed to enhance the raw images. Ultimately, the extracted resonant frequencies and operational deflection shapes are used to detect the presence of damage, demonstrating the feasibility of implementing non-contact video measurements to perform realistic structural damage detection.

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