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Experimental Study on Concrete Fracture Process Zone Using digital image correlation technique

JOURNAL OF TESTING AND EVALUATION 2021年第2期49卷 896-914页

作者： Li, Shengtao Chen, Xudong Feng, Lu Zhang, Xiangru Fan, Xiangqian Lu, Jun Hohai Univ Coll Civil & Transportat Engn Xikang Rd Nanjing 210098 Jiangsu Peoples R China Hohai Univ Coll Dayu Xikang Rd Nanjing 210098 Jiangsu Peoples R China Nanjing Hydraul Res Inst Dept Mat & Struct Engn 34 Hujuguan Rd Nanjing 210029 Jiangsu Peoples R China

The fracture process zone (FPZ) of concrete under three-point bending was extensively investigated using the digital image correlation technique. Surface displacement, strain components, crack opening displacement, effective crack length, and crack tip position were calculated and analyzed. The development of crack and FPZ were obtained through data processing and applied to the analysis of mechanical response. The development of the FPZ, divided into three stages, was found to have strong consistency with the change of the mechanical behavior of concrete. Two characteristic parameters of FPZ were used to study the size effect of concrete. It is found that with the increase of size, the FPZ will develop deeper at peak load. However, the ratio of the maximum length of the FPZ to the initial ligament length does not vary with size, which is about 0.85 in this study.

关键词： fracture process zone digital image correlation technique three-point flexural test crack propagation effective crack length size effect

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Experimental investigation on shear behavior of full-scale glued laminated bamboo beams under three-point loading test and using digital image correlation technique

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INDUSTRIAL CROPS AND PRODUCTS 2023年第PartB期204卷

作者： Xu, J. J. Xiong, W. W. Wang, X. Li, Z. Xiao, Y. Qin, S. J. Nanjing Tech Univ Coll Civil Engn Nanjing 211816 Peoples R China Zhejiang Univ Coll Civil Engn & Architecture Hangzhou 310058 Peoples R China Zhejiang Univ Univ Illinois Urbana Champaign Inst Dept Energy Environm & Sustainable Syst Sci Haining 314400 Peoples R China Zhejiang Univ Ninghai Joint Res Ctr Biobased Mat & Carbon Neutra Ningbo 315600 Peoples R China Hainan Univ Sch Civil Engn & Architecture Haikou 570228 Peoples R China

Applying bamboo in construction is expected to reduce carbon footprint and promote environmental protection. Very limited information is available in the literature about the shear behavior of glued laminated bamboo (glubam, i.e., a type of engineered bamboo) beams. To this end, this paper presents an experimental investigation of shear behavior for full-scale glubam beams using three-point loading test. Fourteen specimens were tested, considering the effect of shear span-depth ratio (a/d) and beam depth on the shear response of glubam beams. digital image correlation (DIC) technique was conducted to measure the strain fields on two specimens with different shear span-depth ratios. The test results show that the glubam beams with a/d= 1.0 occurred local compressive damage at the loading region and the mixed local compression-flexure damage;and beams with a/ d= 2.0 exhibited flexure-dominated damage together with a minor local compressive settlement at the loading region. Specifically, increasing the shear span-depth ratio reduces the load capacity but improves the ductility and minimizes the global damage in the glubam beam. Larger shear area of the beam has a smaller shear stress, which demonstates the scale effect on the shear behavior of the glubam beam. DIC technique is feasible for monitoring the shear behavior of glubam beams with a small shear span-depth ratio. Meanwhile, this technique can also be employed for the beams with a relatively large shear span-depth ratio to monitor the shear behavior at a relatively small deformation.

关键词： Glued laminated bamboo Beams Shear behavior digital image correlation technique Ductility

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Monitoring the failure process of cemented paste backfill at different curing times by using a digital image correlation technique

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CONSTRUCTION AND BUILDING MATERIALS 2022年 346卷

作者： Yang, Liujun Hou, Chen Zhu, Wancheng Liu, Xige Yan, Baoxu Li, Lei Northeastern Univ Ctr Rock Instabil & Seism Res Sch Resource & Civil Engn Shenyang 110819 Peoples R China Xian Univ Sci & Technol Energy Sch Xian 710054 Peoples R China

Understanding the mechanical properties and failure process of cemented paste backfill (CPB) is fundamental for the backfill design in underground mining. In this research, physical and mechanical tests were conducted on CPB having different hardening times. The volumetric water content (VWC) was used to reflect the CPB hard -ening process because it is a confirmed controlling variable that strongly correlated with the peak strength, brittleness index and maximum strain at fracture initiation. Moreover, the deformation behavior, fracture development and failure pattern of CPB having different curing times were observed by using a digital image correlation (DIC) technique. The experimental results suggest that the fracture development can be divided into four stages, the gestation, initiation, propagation and coalescence of fractures. The failure pattern changed from shear to tensile-shear composite and finally to tensile failure as the water content decreased. The results contribute to better understanding the time-dependent mechanical behavior of CPB after it is back-filled into underground stopes.

关键词： Cemented paste backfill Hardening process digital image correlation technique Failure process

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Fatigue crack growth mechanism in ferroelectric ceramics under alternating electric field: An investigation by digital image correlation technique

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ACTA MATERIALIA 2022年第0期235卷

作者： Li, Yingwei Chen, Zeji Duan, Guan Wuhan Univ Sch Civil Engn Wuhan 430072 Hubei Peoples R China Wuhan Univ State Key Lab Water Resources & Hydropower Engn Sc Wuhan 430072 Hubei Peoples R China Wuchang Univ Technol Sch Intelligent Construct Wuhan 430223 Hubei Peoples R China Southern Univ Sci & Technol Guangdong Prov Key Lab Funct Oxide Mat & Devices Shenzhen 518055 Guangdong Peoples R China Shaoguan Univ Sch Chem & Civil Engn Shaoguan 512005 Guangdong Peoples R China

The deformation of crack tip in PZT ceramics under cyclic electric field loading was characterized by digital image correlation (DIC) technique. Two other specimens without speckles were used to observe the physical processes during the crack propagation in-situ. The deformation of the region of interest is elucidated. Near the U-shaped notch, the DIC results directly reveal the existence of incompatible deformation. However, in the front of the newly formed crack, no incompatible deformation was observed. Additionally, in-situ observation reveals that, the crack growth occurs at the stage of crack closure when the crack propagates steadily. The observed pop-in behavior of the crack during the first cycle of electric field loading is rationalized by the interaction between the incompatible domain switching zones with and without U-shaped notch, which is consistent with the explanation of Westram et al. The subsequent crack propagation after the pop-in cannot be rationalized by the model exploited by Zhu and Yang, Wes tram et al., and Liu and Fang, which is thought to be related to three different factors - arcing, wedging and grain-to-grain interaction. The mechanism for the appearance and the disappearance of the incompatible domain switching zone near the U-shaped notch and around the tip of the newly formed crack is discussed based on the electrical boundary condition (EBC) of the crack surfaces we proposed recently.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Fatigue crack growth Lead zirconate titanate digital image correlation technique Electric field loading Domain switching

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A Study of Plastic Deformation of 08G2B Steel Before and at the Yield Plateau by digital image correlation technique. Part 1. Formation of Plastic and Elastic Deformation Waves

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METAL SCIENCE AND HEAT TREATMENT 2019年第5-6期61卷 274-279页

作者： Farber, V. M. Polukhina, O. N. Vichuzhanin, D. I. Khotinov, V. A. Smirnov, S. V. Ural Fed Univ UrFU Ekaterinburg Russia Russian Acad Sci Ural Branch Inst Engn Sci IMASh Ekaterinburg Russia

Specifics of plastic flow during tensile deformation of the samples of ultra-fine grained steel (08G2B) susceptible to deformation aging have been studied by using a digital image correlation technique. The heat treatment of steel was performed according to the following schemes: 1) heating to 250 degrees C, soaking for 30 min, and cooling in air;and 2) heating to 680 degrees C without soaking, and cooling in air. The standard flat samples were subjected to tensile testing at a constant deformation rate. It was shown that the Luders deformation in the tensile-loaded samples is concentrated in the flow channels formed at the stage of macro-elastic deformation and genetically connected with the maxima of the standing elastic wave.

关键词： tensile curve digital image correlation technique displacement field plastic flow channels

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High strain rate response of bio-composites using split Hopkinson pressure bar and digital image correlation technique

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INTERNATIONAL WOOD PRODUCTS JOURNAL 2019年第1期10卷 22-30页

作者： Pandya, Tejas S. Dave, Maharshi J. Street, Jason Blake, Cody Mitchell, Brian Univ Mississippi Mech Engn Dept Oxford MS 38677 USA Mississippi State Univ Franklin Ctr Dept Sustainable Bioprod Room 222Box 9820 Starkville MS 39762 USA

In this research, high strain rate response and energy absorption characteristics under dynamic compression loading of five different bio-composites were studied using a compression split Hopkinson pressure bar (SHPB) and DIC (digital image correlation) technique. This study is to map suitability of plant-based materials instead of petroleum-based plastic as a constituent raw material in composites. Bio-composites panels were made from Southern yellow pine (SYP), Corn starch (CS), and Methylene diphenyl diisocyanate (MDI) using a Dieffenbacher hot press. The ability of non-contact DIC analysis served as a valuable tool to measure the strains over a large range of deformation in wood-based bio-composites subjected to high strain rate compressive loading. Among all, Material 2 bio-composite with high manufacturing pressure had highest peak strength, shows that material behaviour at high strain rates is strongly dependent on the manufacturing pressure during fabrication. Presence of corn starch marginally increased the energy absorption capacity.

关键词： Bio-composites split Hopkinson pressure bar digital image correlation technique high strain rate specific energy absorption

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Damage and deformation assessment of earthquake-resistant RC slotted beam-column connections using digital image correlation technique

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ENGINEERING STRUCTURES 2020年 215卷 110442-110442页

作者： Oudah, Fadi El-Hacha, Raafat Dalhousie Univ Dept Civil & Resource Engn Halifax NS Canada Univ Calgary Dept Civil Engn Calgary AB Canada

Slotted-beam concrete connections with relocated plastic hinges mitigate yield penetration into the joint, result in minimal beam elongation, and achieve a non-tearing action to the attached slab when subjected to seismic excitation. Slotted-beam connections can have a single slot made at the bottom face of the beam member or double slots made at the top and bottom faces of the beam member. The former configuration is referred to as the Single Slotted Beam system (SSB), while the latter configuration is referred to as the Double Slotted Beam system (DSB). In this research, the damage evolution and deformation mechanisms of large-scale experimentally tested SSB and DSB connections with and without relocated vertical slots were investigated. The damage evolution was studied using ductility-based damage indices, energy-based damage indices, and other forms of damage assessment methods. The contribution of the beam deformation, column deformation, and joint deformation to the overall drift was assessed using the digital image correlation technique (DICT). The damage assessment indicated that relocating the vertical slots away from the face of the column resulted in decreasing the ductility capacity of the SSB system while it resulted in insignificant change up to a relocation distance equivalent to the beam effective shear depth in the DSB system. The deformation assessment indicated that increasing the relocation distance in the SSB system results in reducing the effectiveness of the system in relocating the center of rotation, while the relocation distance of the vertical slot has negligible influence on the effectiveness of relocating the center of rotation in the DSB system.

关键词： Concrete Connection Damage Deformation digital image correlation technique Earthquake-Resistant Slotted-Beam

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Application of digital image correlation technique for Measurement of Tensile Elastic Constants in Brazilian Tests on a Bi-Modular Crystalline Rock

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GEOTECHNICAL TESTING JOURNAL 2018年第4期41卷 664-674页

作者： Patel, Shantanu Martin, C. Derek Univ Alberta Donadeo Innovat Ctr Engn Dept Civil & Environm Engn 9211-116 St NW Edmonton AB T6G 1H9 Canada

Most rocks show different elastic properties in tension and compression (bi- modularity). In this study, we derive new equations to calculate the tensile Young's modulus and Poisson's ratio from a Brazilian test by incorporating bi-modularity into stress - strain equations. We tested Brazilian specimens of Lac du Bonnet granite and compared the Young's modulus and Poisson's ratio in tension obtained with the values from direct tension tests on dog- bone shaped specimens. digital image correlation (DIC) and conventional strain gauges were used to extract the strain on the flat surfaces of the Brazilian disks. With the DIC technique, a speckle density of approximately 250 speckles/cm(2) was needed to accurately capture the strain pattern. The strain measured using the DIC technique was consistent with the strain measured using the conventional strain gauges. The major advantage of the DIC technique is the ability to map the complete strain pattern over the surface of the Brazilian disk and quantify the uniformity of loading. The Young's modulus and Poisson's ratio in tension were obtained using the new equations and were found to be in general agreement with the values obtained from the direct tension tests.

关键词： Brazilian test digital image correlation technique tensile Young's modulus tensile Poisson's ratio bi-modularity

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Investigation of fracture properties of a piezoelectric stack actuator using the digital image correlation technique

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INTERNATIONAL JOURNAL OF FATIGUE 2017年第Part1期101卷 106-111页

作者： Ngoc San Ha Vinh Tung Le Goo, Nam Seo Konkuk Univ Smart Microsyst Res Lab Dept Adv Technol Fus Div Interdisciplinary Studies Seoul 05029 South Korea

In this study, the fracture properties of a piezoelectric stack actuator made of a single crystal (PMN-29PT) were investigated using a three point bending test along with the digital image correlation (DIC) technique. To simplify the model of the piezoelectric stack and minimize the cost, two layers of PMN-29PT and one thin copper electrode were glued together using silver conductive adhesive instead of a real piezoelectric stack with 40 PMN-29PT layers. The PMN-29PT layers were then strongly attached with a two square section acrylic beam forming a beam with the same geometry as the piezoelectric stack. The three point bending test results showed that the force at the crack onset was around 85% of the fracture force. The maximum stress and fracture energy from force-displacement data were measured to be 1.41 MPa and 3.83 J/m(2), respectively. Furthermore, the fracture surface indicated that the fracture energy was affected by the surface of the copper electrode, and that the rough surface of the electrode can increase the fracture energy. The fracture energy was determined using a simple beam theory. The fracture energy according to the simple beam theory was slightly smaller than that from force-displacement data. Understanding the measured fracture properties of the piezoelectric stack will help us prevent the fracture of the stack when the piezoelectric stack actuator is handled. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Fracture Stack actuator PMN-29PT digital image correlation technique Three point bending test

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Nonlinear 3PB and 4PB Flexural Behavior and Softening Localization for Epoxy Resin E 863 Using digital image correlation technique

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EXPERIMENTAL techniqueS 2016年第1期40卷 159-171页

作者： Fard, M. Y. Chattopadhyay, A. Liu, Y. Arizona State Univ Dept Mech & Aerosp Engn Sch Engn Matter Transport & Energy Tempe AZ 85287 USA

The effect of local strain and stress distribution in the polymeric material under out of plane loading is of interest in many applications. Flexural testing of the polymer resins is necessary to evaluate their mechanical behavior. In this paper, the flexural response of polymer resin Epon 863 mixed with the curing agent EPI-CURE 3290 using a 100/27 weight ratio has been investigated in three-point bending (3PB) and four-point bending (4PB) at different strain rates. Beams with different lengths and span to depth ratios were tested. Results show a higher flexural strength for 4PB than 3PB. Strain fields within the polymer beam structure were determined using the digital image correlation (DIC) technique to study the evolution of softening localization in 3PB and 4PB setups. Results show that the length of the softening localization is less than half of the thickness throughout the loading. The DIC technique was used to obtain the location of the neutral axis in the nonlinear stage of the material behavior. Results indicate the nonlinear variations of the neutral axis location for epoxy resin Epon E 863. The results show that the DIC technique can accurately characterize the material response of an epoxy resin for flexural loading.

关键词： 3PB Tests 4PB Tests Softening Localization Material Properties Epoxy Resin Moment Curvature Load Deflection digital image correlation technique

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