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Measurement of Aluminum Edge Stretching Limit Using 3D Digital Image Correlation

FCA US LLC-Changqing Du, Yongjun Zhou, Dajun Zhou
Oakland University-Xin Xie, Xiaona Li, Yi-Hsin Chen, Guobiao Yang, Yaqian Zheng, Bernard Sia, Christina Phillips, Lianxiang Yang
Published 2015-04-14 by SAE International in United States
This paper introduces an industrial application of digital image correlation technique on the measurement of aluminum edge stretching limit. In this study, notch-shape aluminum coupons with three different pre-strain conditions are tested. The edge stretching is proceeded by standard MTS machine. A dual-camera 3D Digital Image Correlation (DIC) system is used for the full field measurement of strain distribution in the thickness direction. Selected air brush is utilized to form a random distributed speckle pattern on the edge of sheet metal. A pair of special optical lens systems are used to observe the small measurement edge area. From the test results, it demonstrate that refer to the notched coupon thickness, pre-tension does not affect the fracture limit; refer to the virgin sheet thickness, the average edge stretch thinning limits show a consistent increasing trend as the pre-stretch strain increased. Test plan, experimental setup, and experimental results are shown in detail in this article.
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Measure of Forming Limit Strain on the Aluminum Sheets Passed Through Draw-Bead by Digital Image Correlation

FCA US LLC-Changqing Du, Yongjun Zhou
Ford Motor Co-Cedric Xia
Published 2015-04-14 by SAE International in United States
Accurate determination of the forming limit strain of aluminum sheet metal is an important topic which has not been fully solved by industry. Also, the effects of draw beads (enhanced forming limit behaviors), normally reported on steel sheet metals, on aluminum sheet metal is not fully understood. This paper introduces an experimental study on draw bead effects on aluminum sheet metals by measuring the forming limit strain zero (FLD0) of the sheet metal. Two kinds of aluminum, AL 6016-T4 and AL 5754-0, are used. Virgin material, 40% draw bead material and 60% draw bead material conditions are tested for each kind of aluminum. Marciniak punch tests were performed to create a plane strain condition. A dual camera Digital Image Correlation (DIC) system was used to record and measure the deformation distribution history during the punch test. The on-set necking timing is determined directly from surface shape change. The FLD0 of each test situation is reported in this article. From the results of this study, the draw bead effects (enhanced forming limit behaviors) are found in…
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The Research on Edge Tearing with Digital Image Correlation

FCA US LLC-Changqing Du, Dajun Zhou, Yongjun Zhou
Oakland University-Xiaona Li, Biyu Ye, Xinfeng Shi, Yaqian Zheng, Junrui Li, Lianxiang Yang
Published 2015-04-14 by SAE International in United States
Material formability is a very important aspect in the automotive stamping, which must be tested for the success of manufacturing. One of the most important sheet metal formability parameters for the stamping is the edge tear-ability. In this paper, a novel test method has been present to test the aluminum sheet edge tear-ability with 3D digital image correlation (DIC) system. The newly developed test specimen and fixture design are also presented. In order to capture the edge deformation and strain, sample's edge surface has been sprayed with artificial speckle. A standard MTS tensile machine was used to record the tearing load and displacement. Through the data processing and evaluation of sequence image, testing results are found valid and reliable. The results show that the 3D DIC system with double CCD can effectively carry out sheet edge tear deformation. The edge tearing test method is found to be a simple, reliable, high precision, and able to provide useful results.
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Spatial Phase-Shift Digital Shearography for Out-of-Plane Deformation Measurement

SAE International Journal of Materials and Manufacturing

Donghua University; Oakland University-Ping Zhong
Oakland University-Xin Xie, Yaqian Zheng, Xiaona Li, Bernard Sia, Lianxiang Yang
  • Journal Article
  • 2014-01-0824
Published 2014-04-01 by SAE International in United States
Measuring deformation under dynamic loading is still a key problem in the automobile industry. The first spatial phase-shift shearography system for relative deformation measurement is reported. Traditional temporal phase-shift technique-based shearography systems are capable of measuring relative deformation by using a reference object. However, due to its low acquisition rate, the existing temporal phase-shift shearography system can be only used under static loading situations. This paper introduces a digital shearography system which utilizes the spatial phase-shift technique to obtain an extremely high acquisition rate. The newly developed spatial phase-shift shearography system uses a Michelson-Interferometer as the shearing device. A high power laser at 532nm wavelength is used as the light source. A one mega pixels high speed CCD camera is used to record the speckle pattern interference. The spatial frequency carrier is introduced by tilting one of the mirrors in the Michelson-Interferometer. The Fourier Transform method (FT) is used to separate the spectra on spatial frequency domain. The Windowed Inverse Fourier Transform (WIFT) method is then used to evaluate the phase information of the recorded…
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