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A review on evaluation of crack resistance of asphalt mixture by semi-circular bending test

Journal of Road Engineering 2023年第1期3卷 87-97页

作者： Yongjun Meng Weikang Kong Chaoliang Gou Shenwen Deng Yirong Hu Jing Chen Liupeng Fan School of Civil Engineering and Architecture Guangxi UniversityNanning 530004China Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education Guangxi UniversityNanning 530004China Special Geological Highway Safety Engineering Technology Research Center Guangxi UniversityNanning 530004China National High-performance Computing Center Nanning Branch Nanning 530004China

Although there are many kinds of fracture tests to choose from in evaluating the crack resistance of asphalt mixture,the semi-circular bending(SCB)test has attracted a lot of attention in the academic road engineering community because of its simplicity,stability,and flexibility in testing and evaluation.The SCB test has become a common method to study the cracking resistance of asphalt mixture in recent years.This paper mainly summarizes the overview of the SCB test,summarizes some research results and common characterization parameters of the SCB test method in monotone test and fatigue test in recent years,and predicts and suggests the research direction of the SCB test in the future.It is found that the research on the monotonic SCB test is more comprehensive,and the research on the SCB fatigue test needs to be further improved in the aspects of loading mode,characterization parameter selection,and so on.Researchers can flexibly adjust the geometric dimensions and the test parameters of semi-cylindrical specimens,and conduct comprehensive analysis combined with the results of numerical simulation.The crack resistance of asphalt mixture can be comprehensively evaluated by fracture energy,fracture toughness,stiffness,flexibility index and other fracture indicators,combined with the crack propagation of the specimen.The analysis of numerical simulation can confirm the test results.In order to standardize the setting of fatigue parameters for future application,it is necessary to standardize the setting of bending performance.

关键词： Asphalt mixture crack resistance Fatigue performance Semi-circular bending test

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Toughening effects of Mo and Nb addition on impact toughness and crack resistance of titanium alloys

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Journal of Materials Science & Technology 2021年第20期79卷 147-164页

作者： Shixing Huang Qinyang Zhao Yongqing Zhao Cheng Lin Cong Wu Weiju Jia Chengliang Mao Vincent Ji School of Materials Science and Engineering Northeastern UniversityShenyangLiaoning110819China School of Material Science and Engineering Chang’an UniversityXi’anShaanxi710064China Northwest Institute for Nonferrous Metal Research Xi’anShaanxi710016China School of Mechanical Engineering Liaoning Shihua UniversityFushunLiaoning113001China ICMMO/SP2M UMR CNRS 8182UniversitéParis-SaclayOrsay91405France

Ti-6Al,Ti-6Al-2Mo and Ti-6Al-3Nb alloys were prepared to investigate the toughening effects ofβstabilizers Mo and Nb on impact toughness and crack resistance of titanium alloys.Instrumented Charpy impact tests showed that the total impact absorbed energy of Ti-6Al-2Mo and Ti-6Al-3Nb(∼64 J)were two times higher than that of Ti-6Al(∼30 J),indicating the higher impact toughness of Ti-6Al-2Mo and Ti-6Al-3Nb alloys.Analysis of load-displacement curves revealed the similar crack initiation energy of Ti-6Al,Ti-6Al-2Mo and Ti-6Al-3Nb(15.4 J,16.1 J and 15.0 J,respectively).However,the higher crack propagation energy of Ti-6Al-2Mo and Ti-6Al-3Nb(46.7 J and 48.3 J,respectively)were about three times higher than that of Ti-6Al(14.4 J),indicating the stronger resistance to crack propagation in Ti-6Al-2Mo and Ti-6Al-3Nb.Post-mortem analysis of impact samples demonstrated that the increased dislocation density and deformation twinning were mainly responsible for the stronger resistance to crack propagation in Ti-6Al-2Mo and Ti-6Al-3Nb.Due to the invisibility of dislocation activation and deformation twinning during the Charpy impact process,a mathematical model has been proposed to evaluate the effects of Al,Mo and Nb elements on dislocation mobility based on the Yu Rui-huang electron theory.Addition of Mo and Nb elements significantly improved the dislocation mobility in Ti-6Al-2Mo and Ti-6Al-3Nb compared to that in Ti-6Al alloy.Therefore,more dislocations were activated in Ti-6Al-2Mo and Ti-6Al-3Nb which supplied the larger plastic deformation under impact loading.A dislocation-based model also has been proposed to interpret the nucleation and propagation of deformation twinning under the impact loading.Dislocation pileup atα/βinterfaces provided potential sites for nucleation of deformation twinning in Ti-6Al-2Mo and Ti-6Al-3Nb.Furthermore,deformation twinning facilitated the dislocation motion inαgrains with hard orientations.The increased dislocation mobility and deformation twinning were responsible for the stronger crack

关键词： Titanium alloy Impact toughness crack resistance Dislocation mobility Deformation twinning

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Effects of alloy elements on microstructure and crack resistance of Fe-C-Cr weld surfacing layer

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China Welding 2003年第2期12卷 92-97页

作者：孙大谦王文权宣兆志任振安 School of Materials Science and Engineering Jilin University Changchun 130025

Effects of alloy elements on the microstructure and crack resistance of Fe-C-Cr weld surfacing layer were investigated. The results show that microstructures of the layer mainly consist of carbides and austenite matrix. Increasing C and Cr contents impair the crack resistance of the layer due to increased amount of brittle carbides. The addition of Ni, Nb or Mo improves the crack resistance of Fe-C-Cr weld surfacing layer by increasing the amount of austenite and forming fine NbC or M 7C 3 carbides in the layer. But, the excessive Nb (>2.50wt%) or Mo (>1.88wt%) impairs the crack resistance of the layer, which has relation with increased carbides or carbide coarsening and austenite matrix solid solution strengthening. The proper combination of C, Cr, Ni, Nb and Mo can further improve not only the crack resistance of Fe-C-Cr weld surfacing layer but also the erosion resistance as a result of fine NbC and M 7C 3 carbides distributing uniformly in austenite matrix. The optimal layer compositions are 3.05wt%C, 20.58wt%Cr, 1.75wt%Ni, 2.00wt%Nb and 1.88wt%Mo.

关键词： weld surfacing layer alloy element crack resistance

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Study on the improvement of the crack resistance property of mortar added with jute fibers

Study on the improvement of the crack resistance property of...

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2006中国国际毛纺织会议暨IWTO羊毛论坛

作者： Yu Husheng1,2, Chi Deling2, Yan Haojing1 (1. College of Textiles, Donghua University, Shanghai 200051,China 2. College of Textiles and Garment,Qingdao University, Qingdao,Shandong 266071, China)

Investigation on the improvement of crack resistance of mortar by adding reinforce fibers was dealt with in this paper. It reveals that jute fibers yields better results in comparison with polypropylene, and the smaller the linear density and shorter in length the added fiber, the greater crack resistance of the mortar specimen. The test was carried out by study of the crack developed on the specimen during solidification. The cracks are then classified according to their width, and then the distribution form of the total length of the cracks in each group and the crack index could be obtained. The crack resistance ability is clarified by suggestion of ACI-544.

关键词： fiber fiber-reinforced mortar crack crack resistance crack index

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Effects of Nb Addition on Charpy Impact Properties of TiVTa Refractory High‑Entropy Alloy

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Acta Metallurgica Sinica(English Letters) 2023年第3期36卷 405-416页

作者： Xue Yin Yan‑Kun Dou Xin‑Fu He Ke Jin Cheng‑Long Wang Ya‑Guang Dong Cun‑Yong Wang Yun‑Fei Xue Wen Yang Department of Reactor Engineering Technology Research China Institute of Atomic EnergyBeijing 102413China School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Advance Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China

In the present study,the effects of Nb addition on Charpy impact properties of TiVTa refractory high-entropy alloy with high strength-ductility trade-off were systematically studied by using the instrumented Charpy impact testing machine.The experimental results showed that the impact toughness was remarkably improved by Nb addition in TiVTa to form TiVTaNb alloy.The crack initiation energy and propagation energy of TiVTaNb were 67.3%and 24.9%higher than that of TiVTa,indicating that Nb addition simultaneously reinforced the resistance to crack initiation and propagation.The impact fracture of TiVTaNb exhibited larger bending degree of shear lips,deeper dimples and more secondary cracks which effectively dissipated more impact energy.The deformation mechanism of TiVTa alloy was dominated by dislocation activities.While in TiVTaNb,the deformation mechanism was synergized by dislocation activities and deformation twinning,which were the main contributors for the improved impact properties and the stronger crack resistance of TiVTaNb alloy under impact loading.

关键词： Refractory high-entropy alloys Nb addition Impact property crack resistance Deformation mechanism

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Sensitive Evaluation on Early cracking Tendency of Concrete with Inclusion of Light-burnt MgO

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Journal of Wuhan University of Technology(Materials Science) 2011年第5期26卷 1018-1022页

作者：陈霞 Changjiang River Scientific Research Institute

The advanced temperature and stress test machine was introduced to determine the early cracking tendency of concrete with inclusion of light-burnt MgO under full restraint by tracking the development of thermal,physical and deformation properties.Results showed that light-burnt MgO being incorporated ranging between 4 wt% and 6 wt% of cementitious materials was beneficial to increase the maximum compressive stress and cracking stress of concrete by 0.37 MPa and 0.2 MPa on average respectively.The second zero stress temperature was reduced by 11.4 ℃ and the maximum temperature was slightly reduced while cracking thermal impact was significantly enhanced from 59.8 ℃ to 66.2 ℃.Sensitive anti-cracking coefficient F was forwarded to assess the early cracking tendency of concrete and the inclusion of 4 wt% light-burnt MgO with activity of 109 s ranked the best in crack resistance.

关键词： crack resistance cracking stress light-burnt MgO concrete sensitive evaluation

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Research on Concrete Preparation for the Steel-concrete Composite Segment of Jingyue Yangtze River Bridge

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武汉理工大学学报 2010年第17期32卷 196-200页

作者： DENG B Wuhan Harbor Engineering Design & Research Institute Co. Ltd Wuhan 430071China Key lab of large-span Bridge Construction Technology Ministry of CommunicationWuhan 430071China School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

To improve the quality of the steel-concrete composite segment of the box girder,to ensure the compactness of concrete to avoid debonding and to enhance the fatigue strength of concrete are critical to the concrete preparation for such site. Furthermore,the coordination ability to deformation between steel and concrete is also important because of great difference of the elastic modulus between them. Concrete for the steel-concrete composite segment with high fluidity,excellent crack resistance and low shrinkage was prepared by adding efficient poly-carboxylic water-reducing agent,high quality fly ash and expansion agent to it. The quality of the concrete of the half partial testing block showed that the optimal mix proportion of polypropylene fiber reinforced concrete had achieved expected effect,ensured high quality,thus meeting the requirements of construction.

关键词： steel-concrete composite segment polypropylene fiber reinforced concrete crack resistance

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Determination of the Fracture Toughness of Optomechanical Devices

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Optics and Photonics Journal 2016年第11期6卷 298-304页

作者： George A. Kurilenko Valerik S. Ayrapetyan Novosibirsk State Technical University Novosibirsk Russia Siberian State University of Geosystems and Technology Novosibirsk Russia

Static fracture toughness characteristics are traditionally determined in tests of standard notched specimens using a P-V curve, where P is the load and V is the notch-opening displacement. This curve has a characteristic point Q. At the load PQ corresponding to this point, the crack starts to propagate. For this load, the fracture toughness characteristics are then calculated. In brittle (elastic) fracture, the P-V curve at the onset of crack propagation has an extremum (or a local extremum), from whose ordinate PQ is determined with sufficient accuracy. In ductile and elastic-ductile fracture, P-V curves are monotonically increasing, and PQ is calculated using the 5% secant offset method without taking into account the characteristics of the material, so that the PQ is determined inaccurately. To improve the accuracy of PQ determination, we propose a thermographic method for determining the fracture toughness of metals. This method involves plotting the load P against the temperature change ΔТ over a relatively short period of time at the notch tip. This plot is then transformed to a P-ΔS curve, where ΔS is the specific entropy increment at the notch tip, which is calculated through ΔТ. This thermodynamic diagram has a characteristic step at the beginning of crack propagation, and from the ordinate of this step, PQ can be determined much more accurately. Furthermore, in the thermographic method, the preparation of test specimens can be simplified by replacing the process of growing a fatigue crack at the tip of a notch by making a sharp cut, which provides significant time savings. Statistical processing and comparison of test results of steel 20 specimens using the conventional and thermographic methods have shown the advantages of the thermographic method in accuracy and complexity.

关键词： crack resistance Stress Intensity Factor Temperature Entropy Specified Load Incision Cut crack Motion

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