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Qinwei Ma

Bio: Qinwei Ma is an academic researcher from Chinese Ministry of Education. The author has contributed to research in topics: Digital camera. The author has an hindex of 1, co-authored 1 publications receiving 28 citations.

Papers
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Journal ArticleDOI
TL;DR: The experimental results showed that the thermal expansion of the camera outer case and lens mount, instead of mechanical components within the camera, were the main reason for image expansion.
Abstract: The systematic error for photomechanic methods caused by self-heating induced image expansion when using a digital camera was systematically studied, and a new physical model to explain the mechanism has been proposed and verified. The experimental results showed that the thermal expansion of the camera outer case and lens mount, instead of mechanical components within the camera, were the main reason for image expansion. The corresponding systematic error for both image analysis and fringe analysis based photomechanic methods were analyzed and measured, then error compensation techniques were proposed and verified.

31 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the displacement of the reference sample rigidly attached behind the test sample is first measured using 2D-DIC, and then it is fitted using a parametric model to correct the displacements of the deformed sample to remove the influences of these unfavorable factors.
Abstract: The ideal pinhole imaging model commonly assumed for an ordinary two-dimensional digital image correlation (2D-DIC) system is neither perfect nor stable because of the existence of small out-of-plane motion of the test sample surface that occurred after loading, small out-of-plane motion of the sensor target due to temperature variation of a camera and unavoidable geometric distortion of an imaging lens. In certain cases, these disadvantages can lead to significant errors in the measured displacements and strains. Although a high-quality bilateral telecentric lens has been strongly recommended to be used in the 2D-DIC system as an essential optical component to achieve high-accuracy measurement, it is not generally applicable due to its fixed field of view, limited depth of focus and high cost. To minimize the errors associated with the imperfectness and instability of a common 2D-DIC system using a low-cost imaging lens, a generalized compensation method using a non-deformable reference sample is proposed in this work. With the proposed method, the displacement of the reference sample rigidly attached behind the test sample is first measured using 2D-DIC, and then it is fitted using a parametric model. The fitted parametric model is then used to correct the displacements of the deformed sample to remove the influences of these unfavorable factors. The validity of the proposed compensation method is first verified using out-of-plane translation, out-of-plane rotation, in-plane translation tests and their combinations. Uniaxial tensile tests of an aluminum specimen were also performed to quantitatively examine the strain accuracy of the proposed compensation method. Experiments show that the proposed compensation method is an easy-to-implement yet effective technique for achieving high-accuracy deformation measurement using an ordinary 2D-DIC system.

70 citations

Journal ArticleDOI
TL;DR: In this article, the second-order displacement gradients were used to evaluate the displacement and strain systematic errors of the digital image correlation (DIC) method in local deformations such as the Portevin-Le Chatelier bands, the deformations near the gap and the crack tips.

57 citations

Journal ArticleDOI
TL;DR: In this paper, the authors applied a pre-filtering to the images prior to the correlation so that the high-frequency contents of the speckle pattern were suppressed. Butterworth and Wiener filters were used to reduce the systematic error.

44 citations

Journal ArticleDOI
TL;DR: In this paper, a 3D-DIC system was used to measure the thermal deformation of a tungsten sample above 3000 °C, and three schemes based on blue light sources, self-radiating light sources and a dual wavelength optical filter were designed for three temperature ranges from room temperature to 3067 °C.

42 citations

Journal ArticleDOI
Bing Pan1
TL;DR: This paper aims to give a comprehensive overview and more insights of the work on thermal error analysis and compensation for DIC/DVC measurements.

30 citations