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A novel optical extensometer is developed to estimate the local uniform strain on planar surface accurately. The proposed system consists of a shared large format lens and two image sensors, which acquire pairs of images of two isolated small regions on the object surface simultaneously. Digital image correlation (DIC) algorithm is applied to determine the relative displacement between gauge points designated on recorded pairs of images. Then local strain can be extracted after dividing the relative displacement by the scale distance. Moreover, a special experimental setup called “correction sheet” is used to eliminate the virtual strain induced by out-of-plane motions. Uni-axial tensile experiments are performed to validate the reliability and resolution of the optical extensometer, and the measurement results demonstrate that the resolution of the optical extensometer achieves 2–3 με. 相似文献
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自动消除载荷偏心影响的引伸计研究 总被引:2,自引:0,他引:2
本文基于拉伸圆截面试样圆周上各点的应变分析,提出一种自动消除载荷偏心影响的引伸计。该引伸计结构简单、可靠、使用方便。特别是在测定金属杨氏模量中更为适用。用电测实验对比校核的数据表明,自动消除载荷偏心影响引伸计安装在不同位置上测量的相对误差不超过0.5%。 相似文献
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Measuring Fracture Energy in a Brittle Polymeric Material: Application of a High-Speed Optical Extensometer 总被引:1,自引:0,他引:1
The brittle fracture of polymethyl methacrylate (PMMA) was studied using a high-speed extensometer, which consisted of an
optical fiber and a position-sensing detector (PSD). Single-edge-cracked tensile specimens were pin-loaded with a special
jig so that they could split and fly in the loading direction after fracture. The flying height and residual deformation of
the split specimen were measured to estimate the elastic energy E
e and non-elastic energy E
n, respectively. By subtracting E
e and E
n from the external work U
ex applied to the specimen, the fracture energy E
f for creating a new fracture surface was evaluated. The results showed that E
e, E
n, and E
f increased with U
ex, and the ratio E
f/U
ex was about 45% over a wide range of U
ex. Energy release rate was also estimated using U
ex or E
f, and the results suggested that it was overestimated if E
e and E
n were included. 相似文献
5.
高精度应变式引伸计的研究 总被引:1,自引:0,他引:1
大量程引伸计的弹性元件处于大变形工伯状态,引伸计的非线性矛盾较突出。实验研究表明,某些结构的弹性元件,其线性度与结构的组合尺寸有关,存在着最佳线性条件,根据最佳条件和对夹持机构的考虑,设计了两种新型高精度引伸计。 相似文献
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Expressions for the directional dependence of Young's modulus and Poisson's ratio were derived for a general material under plane‐stress conditions. Experiments with a laser extensometer to measure the Young's modulus and Poisson's ratio directly by a tension test are described, and the results are compared with the theoretical expressions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 260–266, 2004 相似文献
7.
M. Tourlonias Ph.D. Student M. -A. Bueno L. Bigué B. Durand M. Renner 《Experimental Mechanics》2005,45(5):420-426
In this paper we present a contactless extensometer. For some flexible materials, with great displacements and deformations,
contact during measurement is not acceptable. In fact, contact measurement can modify the tensile behavior, as is the case
for fibrous materials. Contactless extensometers usually have to print or glue some marks on the sample, which may cause problems
during measurement. These extensometers typically use digital image processingto obtain deformation data. The principle used
in this study uses the natural periodicity or surface patterns inherent in most textile materials without any image processing.
During deformation the distance between two periods or pattern elements changes, allowing this method to measure the real-time
modification of this in-plane distance. The extensometer consists of two parts: an optical device and a signal processing
unit performing a Fourier analysis. Some results obtained during a tensile test on woven fabrics and non-wovens are presented
here. 相似文献
8.
Shuiqiang ZHANG Yichi ZHANG Ming CHEN Yanjun WANG Quan CUI Rong WU D. AROLA Dongsheng ZHANG 《应用数学和力学(英文版)》2018,39(7):967-980
The tensile response, the low cycle fatigue(LCF) resistance, and the creep behavior of an aluminum(Al) cast alloy are studied at ambient and elevated temperatures.A non-contact real-time optical extensometer based on the digital image correlation(DIC)is developed to achieve strain measurements without damage to the specimen. The optical extensometer is validated and used to monitor dynamic strains during the mechanical experiments. Results show that Young's modulus of the cast alloy decreases with the increasing temperature, and the percentage elongation to fracture at 100℃ is the lowest over the temperature range evaluated from 25℃ to 300℃. In the LCF test, the fatigue strength coefficient decreases, whereas the fatigue strength exponent increases with the rising temperature. The fatigue ductility coefficient and exponent reach maximum values at 100℃. As expected, the resistance to creep decreases with the increasing temperature and changes from 200℃ to 300℃. 相似文献
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基于三维数字图像相关方法(3D-DIC)的拉伸实验研究了铸铁的拉伸力学性能,分别得到了应力-应变曲线、弹性模量、抗拉强度、延伸率等拉伸力学性能参数.将3D-DIC应力-应变的测试结果与目前实验中使用广泛的接触式引伸计方法的实验结果作了对比,得到两者的应力-应变曲线基本重合,弹性模量相差不超过4%.此外,还对3D-DIC和机械引伸计的应变绝对误差和相对误差作了详细比较,实验表明3D-DIC在铸铁拉伸力学性能测试中具有足够的应变测量精度,完全可以取代传统引伸计成为一种有效的非接触式变形测量手段. 相似文献
10.
Mechanical testing of ultra-high temperature alloys 总被引:1,自引:0,他引:1
Specially designed facilities for tensile testing of ultra-high temperature alloys are presented. Ohmic heating is chosen
for easy access to the sample, fast attainable heating and cooling rates, simplicity in design and operation. Strain is measured
with a video extensometer by means of the software SuperCreep. The algorithm for the strain measurements is described. Stability
and accuracy of the test system were determined by testing an oxide dispersion strengthened Pt alloy. Performance of the video
extensometer was checked by thermal expansion tests on pure Pt. Tensile tests of the oxide dispersion strengthened alloy Pt-10
wt% Rh DPH at 1600°C have proven the reliability of the equipment. 相似文献
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