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New measurement method of Poisson's ratio of thin films by applying digital image correlation technique

INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING 2014年第5期15卷 883-888页

作者： Kang, Dong-Joong Chen, Feifei Park, Jun-Hyub Pusan Natl Univ Sch Mech Engn Pusan 609735 South Korea Tongmyong Univ Dept Mechatron Eng Coll Engn Pusan 608711 South Korea

This paper describes a new method to measure the Poisson's ratio of thin films by applying digital image correlation technique. image regions in region of interest (ROI) before and after deformation are compared to each other for precise measurement. For the microsized sample, a representative sub-pixel registration algorithm is applied which is the Newton-Raphson iteration method combined with bicubic intensity interpolation. The first order derivatives of the intensities in the axial loading direction and the transverse direction to loading axis were solved and Poisson's ratio is the absolute value of the ratio of transverse strain to the corresponding axial strain resulting from uniformly distributed axial stress below the proportional limit of the material. To verify this method, microtensile tests of BeCu thin film were performed and the micro-tensile properties including Poisson's ratio of BeCu thin film were measured. To obtain more accurate Poisson's ratio, the stress-strain curve was divided into several intervals to calculate the Poisson's ratios of BeCu. And, the average value of the Poisson's ratios of several intervals came to 0.304. Besides, the ultimate tensile strength, 0.2% yield strength and elastic modulus of BeCu were obtained and came to 1065 MPa, 1037 MPa, 102 GPa, respectively.

关键词： Poisson's ratio digital image correlation technique BeCu thin film Sub-pixel registration algorithm

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The effects of in-situ SiAlON on the properties and fracture behavior of alumina-based castables: Based on microcrack toughening mechanism

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CERAMICS INTERNATIONAL 2025年第4期51卷 4549-4559页

作者： Zhou, Jiwei Jiang, Jiawen Yu, Renhong Wang, Jiaping Sun, Chenyu Wang, Xin Guo, Qiwei Zang, Yunfei Li, Xinli Henan Univ Sci & Technol High Temp Mat Res Inst Luoyang 471003 Henan Peoples R China Prov & Ministerial Coconstruct Collaborat Innovat Luoyang 471023 Henan Peoples R China Sinosteel Luoyang Inst Refractories Res Co Ltd State Key Lab Adv Refractories Luoyang 471039 Henan Peoples R China

This study investigates the effect of adding Si powder on the microstructure and fracture behavior of in-situ SiAlON bonded alumina-based castables and clarifies the toughness improvement mechanism. The in-situ SiAlON bonded alumina-based castables were obtained using a nitriding reaction method with Si powder as the precursor. The fracture behavior of the specimens was characterised using the wedge-splitting test (WST) and digital image correlation technique (DIC). It was found that introducing in-situ SiAlON bonding phases can significantly improve the fracture behavior and toughness. The toughness parameter (GF/sigma NT) increased from 18.9 mu m to 38.6 mu m as the addition of Si powder increased from 0 wt% to 6 wt%. The primary toughness mechanism of the castables is microcrack toughening. The formation of microcracks is the consequence of a mismatch in the thermal expansion coefficients (CTE) of the corundum and in-situ SiAlON phases.

关键词： In-situ SiAlON Fracture behavior Wedge splitting test digital image correlation technique Alumina-based castables

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Effects of freeze-thaw cycles on fatigue performance of asphalt mixture and a fatigue-freeze-thaw damage evolution model

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CONSTRUCTION AND BUILDING MATERIALS 2024年 449卷

作者： Zhang, Fei Li, Xin Wang, Lan Xue, Zhihua Guo, Zhixiang Inner Mongolia Univ Technol Key Lab Civil Engn Struct & Mech Hohhot 010051 Peoples R China Inner Mongolia Univ Technol Sch Civil Engn Hohhot 010051 Peoples R China Inner Mongolia Univ Technol Sch Sci Hohhot 010051 Peoples R China Chongqing Univ Sch Civil Engn 83 Shabei St Chongqing 400045 Peoples R China

To study the effect of freeze-thaw (FT) cycles on the fatigue performance of composite crumb rubber modified asphalt mixtures (CCRMA), a semicircular bending fatigue test based on the digital image correlation technique (DIC) was used to measure the fatigue life (N-f) of CCRMA and SBS modified asphalt mixtures (SBSMA) and the horizontal strain (Exx) of the DIC deformation field under repeated loading. The variation laws of N-f, Exx and the damage factor (D) defined based on Exx were analyzed under FT cycle conditions. In addition, considering the important influence of FT cycles on the N-f and damage evolution characteristics of asphalt mixtures, based on the classical Chaboche damage evolution model, the influence of FT cycle was considered, a fatigue-freeze-thaw damage evolution model that reflects the effects of FT cycling variables and stress levels on asphalt mixtures was constructed. The results indicate that the Exx peak of asphalt mixture shifts forward with increasing FT cycle number. After 20 FT cycles, the N-f of CCRMA decreased by 73.4 %, 62.1 %, and 75.1 %, while that of SBSMA decreased by 76.5 %, 58.6 %, and 74.6 % at stress ratios of 0.2, 0.3, and 0.4, respectively. The fatigue-freeze-thaw damage evolution model predictions were in agreement with experimental results, with the goodness of fit (R-2) of all N-f prediction models being greater than 0.9. With the exception of a few outliers, the relative error between the measured and predicted N-f for the two asphalt mixtures was within 15 %. This indicates that the model can effectively predict the N-f and damage evolution laws of asphalt mixtures at different stress levels after an arbitrary number of FT cycles. The related research results provide a theoretical basis for predicting the N-f of new roads in cold regions under FT cycles.

关键词： Asphalt mixture digital image correlation technique Freeze-thaw cycle Fatigue damage Damage evolution model

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Experimental investigation on biaxial mechanical properties of laminated rock and floor heave mechanism of tunnel based on DIC

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ENGINEERING FAILURE ANALYSIS 2024年 156卷

作者： Luo, Pingkuang Li, Diyuan Zhang, Chengxi Ru, Wenkai Han, Zhenyu Ma, Jinyin Cent South Univ Sch Resources & Safety Engn Changsha 410083 Peoples R China Southeast Univ Sch Civil Engn Nanjing 210096 Jiangsu Peoples R China Monash Univ Dept Civil Engn Melbourne Vic 3800 Australia

Floor heave at the bottom of a tunnel is a common defect during tunnel service. To study the deformation behavior and failure characteristics of the floor, laminated sandstone specimens with precracked U-shaped grooves were prepared, and a series of biaxial compression tests were carried out in the laboratory. Two typical floor structures of a tunnel (with and without inverts) and four lateral stress levels (sigma 2 = 0, 5, 10 and 15 MPa) were considered. The effects of lateral stress and inverted structure on the deformation and failure characteristics of the floor were investigated. The displacement, strain evolution and failure extent of the floor were analyzed based on the digital image correlation (DIC) technique. The testing results show that the stress concentration at the U-shaped grooves of the specimens can be effectively reduced by the inverted structure. The specimen with an invert can bear more axial deformation and axial stress than that without an invert. The V-shaped notch failure behavior occurred near the tunnel sidewalls for the specimen without an invert, and it occurred in the middle of the tunnel floor for the specimen with an invert. The failure intensity of the V-shaped notch was positively related to the lateral stresses. With the increasing of axial stress, the heave displacement at the tunnel floor gradually increased, while the settlement displacement of the sidewall showed a trend of first increasing and then decreasing. The tensile strain concentration area of the floor undergoes a process of increasing and then decreasing and finally transforms to compressive strain. The failure characteristics of the sandstone specimen observed in the laboratory tests are consistent with the phenomena in real tunnel engineering. In addition, the deformation and failure mechanism of the tunnel floor was analyzed. The key points for the treatment of tunnel floor heave are put forward based on the testing results.

关键词： Biaxial compression test Tunnel floor heave digital image correlation technique V-shaped notch Laminated rock

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Identification of Bimodular Material Parameters via a Semi-Closed Form Solution of the Brazilian Test

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EXPERIMENTAL MECHANICS 2024年第6期64卷 805-821页

作者： Hong, H. Baranger, T. N. Univ Claude Bernard Lyon 1 LMC2 EA7427 82 Bd Niels Bohr F-69622 Villeurbanne France

Backgrounddigital image correlation (DIC) is an advanced measurement technique capable of capturing full-field surface displacements in a non-invasive manner. However, the application of such measurements in the identification of bimodular materials remains insufficiently *** with Analytic Solution Updating (RAU) has been proposed for the identification of mechanical elastic parameters of asymmetric constitutive law behavior using the Brazilian test. This method accomplishes identification by minimizing the gap between the measurements and the semi-closed form *** types of data are employed: the first derived from the semi-closed form solution and the second measured on a 42-day aged mortar specimen using DIC. In the RAU method, three distinct cases are implemented to identify mechanical elastic parameters. These cases are determined by the nature of the data utilized, which can be categorized into axial displacement field, strains at the center, and full-field surface displacement measured on a given specimen *** RAU method successfully identified the compressive, tensile Young's modulus, and the compressive Poisson's ratio from the surface data provided. The identification with full-field surface displacement presented the highest level of accuracy in the RAU method using the identified results of synthetic *** RAU method demonstrates significant accuracy and practicality in identifying the mechanical elastic parameters of bimodular materials.

关键词： Brazilian test digital image correlation technique Bimodular material Tensile modulus Compressive modulus Identification Recalibration

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Tensile properties of transversely isotropic closed-cell PVC foam under quasi-static and dynamic loadings

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JOURNAL OF SANDWICH STRUCTURES & MATERIALS 2024年第3期26卷 373-395页

作者： Tang, Yu Li, Yue Jiang, Xiongwen Zhao, Jiuzhou Zhao, Geng Xie, Wenbo Zhang, Wei Harbin Inst Technol Dept Astronaut Sci & Mech Harbin Peoples R China Xian Aerosp Prop Inst State Key Lab Sci & Technol Liquid Rocket Engine Xian Peoples R China PowerChina Kunming Engn Corp Ltd Kunming Peoples R China Harbin Inst Technol Dept Astronaut Sci & Mech 92 Xidazhi St Harbin 150001 Peoples R China

The uniaxial tensile mechanical properties of PVC foam considering the effects of strain rate ((epsilon) over dot = 0:0007 - 523s(-1)) and anisotropy (R = 1 - 1.57) have been investigated by quasi-static and dynamic (Split Hopkinson Tensile Bar, SHTB) tests. Combined high-speed camera system and digital image correlation (DIC) technique, the real-time surface strain field of the specimen during the whole tensile process was obtained. On this basis, the macroscopic response and failure mode of PVC foam were investigated. The failure mechanism of PVC foam under tensile loading was revealed through Scanning Electron Microscope (SEM) images on fracture cross-section of loaded specimen. Finally, based on experimental data, a prediction equation on tensile strength of PVC foam considering the effects of strain rate and loading angle (anisotropy) is proposed. Furthermore, a nonlinear constitutive model is developed to describe the uniaxial tensile mechanical properties of PVC foam.

关键词： Polyvinyl chloride foam strain rate and anisotropy digital image correlation technique macroscopic failure mode microscopic failure mechanism prediction of tensile strength nonlinear constitutive model

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Experimental and numerical simulation on the sliding process of roof rock blocks triggered by dynamic disturbance

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Underground Space 2023年第3期10卷 269-293页

作者： Feng Dai Wancheng Zhu Min Ren Leilei Niu Chen Hou Center for Rock Instability and Seismicity Research Department of Mining EngineeringSchool of Resources and Civil EngineeringNortheastern UniversityShenyang 110819China Faculty of Land Resources Engineering Kunming University of Science and TechnologyKunming 650093China

With the excavation of underground opening,the roof rock block may fall under external dynamic *** this paper,the roof rock mass was simplified as a rock block system composed of trapezoidal rock blocks.A series of experiments and numerical simulations were performed to study the sliding process of the key block under the horizontal static clamping load and vertical impact *** propagation of stress wave in the block system were captured and analyzed by using high-speed camera and digital image correlation *** results reveal that a pendulum-type wave was generated due to the propagation and superposition of stress waves in the block ***,the governing mechanism of the sliding displacement of the key block was clarified based on the propagation of incident stress waves or pendulum-type ***,it is found that the sliding distance of the key block decreases in a power function with the increasing friction coefficient,or decreases in a parabolic function with the increasing trapezoid internal ***,a case study on the roof block sliding of the roadway at a gold mine was conducted,and it is concluded that the sliding of the key block resulted from the coupled effects of"shear driving"and"low friction"driven by stress wave propagation,regardless of a single or multi-layer rock block *** results may provide technical guideline for preventing rock-falling accidents caused by blasting distur-bances in underground mining.

关键词： Roof rock block Sliding instability Dynamic disturbance Pendulum-type wave digital image correlation technique Numerical simulation

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Mechanical characteristics and crack evolution in specimens with double over-excavated cavities: experimental and numerical investigations

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COMPUTATIONAL PARTICLE MECHANICS 2024年第3期11卷 1421-1440页

作者： Man, Zhongyi Liu, Chun Wei, Mingyao China Univ Min & Technol CUMT Key Lab Gas & Fire Control Coal Mines Xuzhou 221116 Jiangsu Peoples R China China Univ Min & Technol CUMT Sch Safety Engn Xuzhou 221116 Jiangsu Peoples R China China Univ Min & Technol CUMT Natl Joint Engn Lab Internet Appl Technol Mines Xuzhou 221116 Jiangsu Peoples R China Henan Polytech Univ State & Local Joint Engn Lab Gas Drainage & Ground Jiaozuo 454002 Peoples R China

The mechanically over-excavated cavity along the borehole represents an innovative technology designed to enhance permeability in soft coal seams. This study aims to elucidate the complex mechanisms that influence the mechanical properties and crack evolution of over-excavated cavities. Uniaxial compression tests were performed on coal specimens with double over-excavated cavities, and the impact of cavity length-height ratio and shape on mechanical properties and crack evolution was investigated using digital image correlation techniques and acoustic emission (AE) measurements. Discrete element method simulations provided deeper insights into stress evolution and crack behavior around the cavities. The presence of an over-excavated cavity significantly affected the specimen's mechanical properties, with the effect's magnitude closely linked to the length-height ratio. As this ratio decreased, the peak stress and elastic modulus of the specimen increased. Specimens containing elliptical cavities demonstrated higher elastic modulus and peak stress compared to those with rectangular cavities of the same length. Crack initiation and propagation displayed distinct features, such as a sudden surge in AE counts and the appearance of strain concentration regions. The failure mode of the specimen was dominated by shear failure combined with tensile failure, and spalling of the specimen appeared as the length-height ratio decreased, indicating stronger damage. Numerical simulations aligned well with experimental findings, revealing tensile and shear cracks as predominant, with failure resulting from crack coalescence. Specimens containing rectangular cavities were more prone to failure than those with elliptical cavities due to stress concentration in corners. The maximum compressive principal stress was concentrated at the tips of the left and right flaws. The release and transfer of stress concentration zones played a pivotal role in influencing the evolution and behavior

关键词： Gas drainage Mechanical properties Crack evolution digital image correlation technique Stress distribution

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Shear performance assessment of repaired honeycomb sandwich composite panels: An experimental and numerical study

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POLYMER COMPOSITES 2023年第11期44卷 7510-7520页

作者： Zhang, Yidong Sun, Xinyang Liao, Feng Qiao, Yijun Lei, Guannan Lu, Huihu North Univ China Sch Mech Engn Taiyuan Peoples R China Harbin Inst Technol Dept Astronaut Sci & Mech Harbin Peoples R China China Aerodynam Res & Dev Ctr Low Speed Aerodynam Inst Mianyang Peoples R China North Univ China Sch Mech Engn Taiyuan 030051 Peoples R China

This article presents an effective test method for evaluating the shear performance of repaired honeycomb sandwich panels consisting of glass fiber/epoxy matrix skin and Nomex honeycomb core. Addressing the insufficient research on the shear performance of honeycomb sandwich panels after repair in existing literature, this study conducted mechanical performance tests on the honeycomb sandwich panels before and after repair using the picture frame test method. Surface strain measurements are obtained using digital image correlation (DIC) techniques, and load-displacement and shear stress-strain curves are generated from the experimental results. The study concludes that the repair method utilized in this investigation is effective in restoring the mechanical properties of the sandwich panels. In addition, finite element models of the honeycomb sandwich panels before and after repair are established, and a comparative analysis is conducted between the experimental and simulation results. The study examines the shear modulus, ultimate load, and failure mode of the repaired and unrepaired specimens. The findings verify the feasibility of the picture frame test method for evaluating the shear performance of honeycomb sandwich panels. This study provides valuable insights into the design of shear performance repair for honeycomb sandwich panels and offers theoretical support for material recycling.

关键词： digital image correlation technique honeycomb sandwich panels picture frame test repair process shear performance

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Experimental and numerical analysis of hyperelastic plates using Mooney-Rivlin strain energy function and meshless collocation method

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ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS 2023年第1期150卷 199-218页

作者： Hosseini, Shahram Rahimi, Gholamhossein Tarbiat Modares Univ Tehran Iran

In this research, the flexural behavior of a hyperelastic plate made of silicone under uniformly distributed loading was investigated. The displacements and strains were formulated using the first-order shear deformation plate theory (FSDPT). The right Cauchy-Green tensor and Mooney-Rivlin strain energy function were employed to formulate hyperelastic silicone plate governing equations. The strong-form of the governing equations of the silicone plate using Mooney-Rivlin strain energy function and Euler-Lagrange relations were derived for the first time. In the governing equations, the effects of geometrical and material nonlinearity effects were considered simultaneously. The meshless collocation method (MCM) and thin-plate spline radial basis function were utilized to discretize the governing equations. The arc-length continuation algorithm was also used for analyzing the system of non-linear equations. MCM results were compared to those of the experimental test to validate the results of the meshless method. For this purpose, a square silicone plate with simply supported boundary conditions under uniformly distributed loading was investigated via the digital image correlation (DIC) technique. According to the obtained results, the MCM based on radial basis function is an adequate method for non-linear analysis of hyperelastic plates with Mooney-Rivlin strain energy function under uniformly distributed loading.

关键词： Hyperelastic plate Meshless collocation method Radial basis function digital image correlation technique

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