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| 1 | The influence of microwave irradiation on rocks for microwaveassisted underground excavation显示文摘Demand is growing for explosive-free rock breakage systems for civil and mining engineering, and spaceindustry applications. This paper highlights the work being undertaken in the Geomechanics Laboratoryof McGill University to make a real application of microwave-assisted mechanical rock breakage to fullfacetunneling machines and drilling. Comprehensive laboratory tests investigated the effect of microwaveradiation on temperature profiles and strength reduction in hard rocks (norite, granite, and basalt)for a range of exposure times and microwave power levels. The heating rate on the surface of the rockspecimens linearly decreased with distance between the sample and the microwave antenna, regardlessof microwave power level and exposure time. Tensile and uniaxial compressive strengths were reducedwith increasing exposure time and power level. Scanning electron micrographs (SEMs) highlightedfracture development in treated basalt. It was concluded that the microwave power level has a strongpositive influence on the amount of heat damage induced to the rock surface. Numerical simulations ofelectric field intensity and wave propagation conducted with COMSOL Multiphysics software generatedtemperature profiles that were in close agreement with experimental results. | Ferri Hassani Pejman M.Nekoovaght Nima Gharib | 2016 | Journal of Rock Mechanics and Geotechnical Engineering2016，8，1： | 69 |
| 2 | DEVELOPMENT OF INCONEL~ ALLOY 783,A LOW THERMAL EXPANSION,CRACK GROWTH RESISTANT SUPERALLOY显示文摘DEVELOPMENTOFINCONEL~ALLOY783,ALOWTHERMALEXPANSION,CRACKGROWTHRESISTANTSUPERALLOYJ.H.Thndermann(IncoAlloysInternational,Inc.... | J.H.Thndermann(Inco Alloys International, Inc., Huntington, WV 25705, USA ) | 1996 | Acta Metallurgica Sinica(English Letters)1996，9，6： | 23 |
| 3 | Theoretical analysis and experimental investigation on flexural performance of steel reinforced ultrahigh toughness cementitious composite (RUHTCC) beams显示文摘UHTCC (ultrahigh toughness cementitious composite), which is a kind of ultrahigh toughness cemen- titious composites material, exhibits pseudo strain hardening feature when subjected to tension load, and has enormous ductility and prominent crack dispersal ability. Accordingly, UHTCC can improve mechanical behavior of ordinary concrete structure especially its durability, and has been regarded as historical breakthrough to traditional cementitious materials. In this paper, the study focuses on flexure behavior of steel reinforced beam made of UHTCC. Based on the plane section assumption, along with two equilibrium equations of force and moment, the formulae to calculate the flexural load capability for the reinforced ultrahigh toughness cementitious composite (RUHTCC) beam were developed under the assumption that the compression stress- strain relationship in the UHTCC material is a bilinear model. Following this, the simplified formulae were further evolved by effective rectangle stress distribution approach in order to facilitate design of practical engineering. Two effective parameters introduced in effective rectangle approach were determined. The mathematical expressions to evaluate limited rein- forcement ratio, flexural stiffness as well as ductility index were proposed, too. Last, two series of dif- ferent reinforcement ratios of the RUHTCC beams were tested in four-point flexure loading. For com- parison purposes, ordinary RC (reinforced concrete) beams also were prepared. Both moment curva- ture curves and load mid-span displacement curves were recorded and compared with the theoretical calculations. A good agreement between them was found, which validates the proposed theoretical formulae. For ductility index, a slightly big difference between the experimental values and the calcu- lated ones exists. The experimental results show that, compared to control RC beams, the RUHTCC beam can improve both flexural capacity and ductility index, and the degree of improvement will de- crease with the increase in the reinforcement ratio. Particularly, the results also reveal that lager crack width in control beams can be greatly reduced by formation of tightly-spaced fine cracks in UHTCC, which offers more durable structures. | XU ShiLang ZHANG XiuFang | 2009 | Science China(Technological Sciences)2009，52，4： | 18 |
| 4 | Theoretical analysis on bending behavior of functionally graded composite beam crack-controlled by ultrahigh toughness cementitious composites显示文摘Ultrahigh toughness cementitious composites (UHTCC) obviously show strain hardening property under tensile or bending loading. The failure pattern of the UHTCC components exhibits multiple fine cracks under uniaxial tensile loading with prominent tensile strain capacity in excess of 3%, with merely 60 μm average crack width even corresponding to the ultimate tensile strain state. The approach adopted is based on the concept of functionally-graded concrete, where part of the concrete, which surrounds the main longitudinal reinforcement in a RC (reinforced concrete) member, is strategically replaced with UHTCC with excellent crack-controlling ability. Investigations on bending behavior of functionally-graded composite beam crack controlled by UHTCC has been carried out, including theo- retical analysis, experimental research on long composite beams without web reinforcement, validation and comparison between experimental and theoretical results, and analysis on crack control. In addition to improving bearing capacity, the results indicate that functionally-graded composite beams using UHTCC has been found to be very effective in preventing corrosion-induced damage compared with RC beams. Therefore, durability and service life of the structure could be enhanced. This paper discusses the development of internal force and crack propagation during loading process, and presents analysis of the internal force in different stages, moment-curvature relationship from loading to damage and calculation of mid-span deflection and ductility index. In the end, the theoretical formulae have been validated by experimental results. | XU ShiLang LI QingHua | 2009 | Science China(Technological Sciences)2009，52，2： | 17 |
| 5 | Simulation of influence of multi-defects on long-term working performance of high arch dam显示文摘As an integrated structure,an arch dam is assumed to bear loads in its design consideration.However,multi-defects,such as cracks and the opening of transverse joints,are unavoidable during construction and operation.Multi-defects will reduce the structural integrity and stiffness of the dam and affect its working performance and degree of safety.In the current paper,a numerical model of defects and a simulation method of a high arch dam are introduced.The Chencun arch dam is analyzed as a case study.An entire course simulation analysis of the Chencun arch dam from construction to operation is carried out,through which the opening of the transverse and longitudinal joints,formation of cracks,and their influence on deformation and stress of the dam are studied.According to the results of the analysis,appropriate measures should be adopted to prevent the development of cracks,and observation should be strengthened for a more timely discovery of risks. | ZHANG GuoXin ,LIU Yi,ZHENG CuiYing & FENG Fan State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin,Beijing 100038,China China Institute of Water Resources and Hydropower Research,Beijing 100038,China | 2011 | Science China(Technological Sciences)2011，54，S1： | 17 |
| 6 | Crack-induced anisotropy in the crust from shear wave splitting observed in Tangshan region,North China显示文摘Crack-inducedanisotropyinthecrustfromshearwavesplittingobservedinTangshanregion,NorthChinaYuanGAO(高原)Si-HuaZHENG;(郑斯华)andYong... | 高原 郑斯华 孙勇 | 1995 | Acta Seismologica Sinica(English Edition)1995，8，3： | 16 |
| 7 | Crack stop holes in steel bridge decks:Drilling method and effects显示文摘Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress gradient. The optimum drilling location and diameter were studied through analysis of different locations and diameters. By analyzing the effects of flank holes and an additional hole, drilling advice was proposed and fatigue testing of the cracks in a steel bridge deck with a crack stop hole was conducted. The results show that the stress at the crack tip with a crack stop hole decreased, and the major principal stress around the hole was distributed accordingly. The optimum position of the crack stop hole centre was where the centre of the crack stop hole was situated behind the crack and the hole edge coincided with the crack tip. Therefore, hole diameters larger than 8 mm, or those weakening the section by 10%, were suggested as the best diameters. In terms of multi-hole crack stopping, a flank hole was not recommended. The optimum horizontal position of flank holes was at a distance of 1/4 of a single hole diameter from, and in front of, the single hole. Besides, the experiment showed that crack stop hole could only prevent cracks from growing and had no influence on crack growth rate. | 傅中秋 吉伯海 谢曙辉 刘天笳 | 2017 | Journal of Central South University2017，24，10： | 16 |
| 8 | Fatigue crack initiation of magnesium alloys under elastic stress amplitudes:A review显示文摘The most advantageous property of magnesium(Mg)alloys is their density,which is lower compared with traditional metallic materials.Mg alloys,considered the lightest metallic structural material among others,have great potential for applications as secondary load components in the transportation and aerospace industries.The fatigue evaluation of Mg alloys under elastic stress amplitudes is very important in ensuring their service safety and reliability.Given their hexagonal close packed structure,the fatigue crack initiation of Mg and its alloys is closely related to the deformation mechanisms of twiuning and basal slips.However,for Mg alloys with shrinkage porosities and inclusions,fatigue cracks will preferentially initiate at these defects,remarkably reducing the fatigue lifetime.In this paper,some fundamental aspects about the fatigue crack initiation mechanisms of Mg alloys are reviewed,in cluding the 3 followings:1)Fatigue crack initiation of as-cast Mg alloys,2)influence of microstructure on fatigue crack initiation of wrought Mg alloys,and 3)the effect of heat treatment on fatigue initiation mechanisms.Moreover,some unresolved issues and future target on the fatigue crack initiation mechanism of Mg alloys are also described. | B.J.WANG D.K.XU S.D.WANG E.H.HAN | 2019 | Frontiers of Mechanical Engineering2019，14，1： | 15 |
| 9 | Detection of subcritical crack propagation for concrete dams显示文摘Subcritical propagation of cracks is a warning sign of fracture.If such propagation is detected at an early stage,timely maintenance measures can be taken to prevent the failure of structures.To detect the subcritical propagation of a crack,the crack needs to be monitored continuously in a long term, which is not realistic under certain conditions.However,cracks in concrete dams can be monitored continuously by dam monitoring to offer possible detection for subcritical propagation.In this paper, with measured crack openings from dam monitoring,a state equation for characterizing crack development is established based on the grey system theory.The relation between the stability of the equation and the subcritical crack propagation is investigated,then a criterion is proposed for detecting subcritical propagation.An example demonstrates the validity of the criterion and its potential for practical application. | BAO TengFei1 ,2&YU Hong 1,2 1College of Water Conservancy&Hydropower Engineering,Hohai University,Nanjing 210098,China 2National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety,Nanjing 210098,China | 2009 | Science China(Technological Sciences)2009，52，12： | 14 |
| 10 | Experimental investigation and analysis on flexural performance of functionally graded composite beam crack-controlled by ultrahigh toughness cementitious composites显示文摘Based on the concept of functionally graded concrete,UHTCC(ultrahigh toughness cementitious composites)material with excellent crack-controlling ability is strategically substituted for part of the concrete,which surrounds the main longitudinal reinforcement in a reinforced concrete member.Investigations on bending behavior of such a functionally graded composite beam crack-controlled by UHTCC(abbreviated as UHTCC-FGC beam)have been carried out.After establishing a theoretical cal-culation model,the paper discusses the results of four-point bending experiment on long composite beams without web reinforcement,and validates the theoretical formulae through experimental results of UHTCC-FGC beams with different thicknesses of UHTCC layer.Besides improving bearing capacity and saving steel reinforcements,the results indicate that UHTCC-FGC beams can also effectively control the deformation and enhance the ductility of members.At last,the optimal thickness of UHTCC layer in UHTCC-FGC beams has been confirmed,which can not only save materials and improve mechanical performance of members,but also be very effective in preventing corrosion-induced damage and enhancing the durability of members by controlling crack width below 0.05mm under service conditions. | LI QingHua XU ShiLang | 2009 | Science China(Technological Sciences)2009，52，6： | 13 |
| 11 | Experimental study of effect of post processing on fracture toughness and fatigue crack growth performance of selective laser melting Ti-6Al-4V显示文摘For Ti-6Al-4V,a titanium alloy increasingly used in aerospace structure,selective laser melting(SLM)is an attractive additive manufacturing technology,which is attributed to its complex construction capability with high accuracy and good surface quality.In order to obtain qualified mechanical properties,SLM parameters and post processing should be tailored for diverse service conditions.Fracture toughness and fatigue crack growth(FCG)behavior are critical characteristics for damage tolerance evaluation of such metallic structures,and they are affected by post processing technologies significantly.The objective of this study is to obtain the fracture toughness and fatigue crack growth behavior of Ti-6Al-4V manufactured by SLM,and to evaluate the influence of post-SLM thermomechanical treatment and surface machining.Fracture toughness and FCG tests were performed for SLM Ti-6Al-4V in three types of post processing status:as-built,heat treated and hot isostatically pressed(HIPed),respectively.Specimens with as-built and machined surface were tested.The microstructure and fractography were analyzed as well in order to investigate the relevance among manufacture process,microstructure and mechanical properties.The results demonstrate that as-built SLM Ti-6Al-4V presents poor ductility and FCG behavior due to martensitic microstructure and residual stresses.Both heat treatment and hot isostatic pressing improve the plane-stress fracture toughness and FCG performance considerably,while surface machining shows slight effect. | Haiying ZHANG Dengke DONG Shaopu SU An CHEN | 2019 | Chinese Journal of Aeronautics2019，32，10： | 13 |
| 12 | Rock-breaking mechanism and experimental analysis of confined blasting of borehole surrounding rock显示文摘The rock-breaking mechanism and effect of confined blasting were analysed by blasting and impact dynamic mechanics, fluid dynamic mechanics, fracture mechanics as well as blasting experiment. The results showed that the fracturing of surrounding rock in confined blasting condition is the result of coaction of rock pre-cracking by shock wave and stress wave and the continuing expanding crackenhancement of confined medium, and the model of crack development of borehole surrounding rock in confined blasting condition was established. This study acquired the damage range of surrounding rock under the action of shock wave and stress wave, as well as the crack development characteristics of surrounding rock after the wedge-in confined medium into the crack space. Deep-hole confined blasting experiment on large rock showed that the high-efficient utilisation of in-hole explosive was achieved and the safety of rock blasting operation was ensured. Safe static rock-breaking under the action of high-efficient explosive blasting was achieved as well as the unification of super dynamic load of explosive blasting and static rock-breaking of water medium. | Liu Changyou Yang Jingxuan Yu Bin | 2017 | International Journal of Mining Science and Technology2017，27，5： | 12 |
| 13 | Studies on the effect of weld defect on the fatigue behavior of welded structures显示文摘Structural integrity isstated as the science and technology of margin between safety and disaster. Systematic prediction of structural integrity of critical structures such ascombustion chambers,pressure vessels,nuclear reactor components,boilers etc.,ensures the human safety,environmental protection,and the economical considerations.The present work aims at prediction of fatigue behaviour of symmetric structures like pressure vessels in the presence of common welding defects such as lack of fusion( LOF),lack of penetration( LOP) and porosity.A ring type specimen which replicates the stress pattern in thepressure vessel is considered for the study of severity of weld imperfections. Initial dimensions of weld defects are arrived by performing NDT inspection.Crack growth analysis is carried out to determine the remaining life of the welded joint with defects. | Ramu Murugan Prabhu Raja Venugobal Thyla Pudukkarai Ramaswami Sathiskumar Jothi Somu Chinnusamy | 2018 | China Welding2018，27，1： | 12 |
| 14 | A fiber optic sensor for detecting and monitoring cracks in concrete structures显示文摘The formation and propagation of cracks reflect the aging and pathologic changes of concrete structures and may cause problems such as seepage and long-term durability. Crack detection and monitoring is therefore an effective way to evaluate structural health conditions. An important challenge in such a task is that the locations and orientations of cracks in concrete structures are difficult to predict due to material inhomogeneity and complexity. The number of the required conventional electric and electromagnetic sensors to cover all possible cracks may be too large to be practical for a monitoring scheme. In this paper, a fiber optic sensor with distributed crack sensing capability based on optical time domain reflectometry is proposed and its sensing principle is introduced. Experiments are conducted to obtain the optical power loss versus crack opening at different fiber inclination angles, and then a model is developed to quantify it. Finally, an experiment is performed to demonstrate the practical application of the sensor. The test results show that detecting and monitoring cracks with the sensor do not require a-priori knowledge of crack locations and orientations. | BAO TengFei1,2*, WANG JiaLin1,2 & YAO Yuan1,2 1 State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210024, China 2 National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Hohai University, Nanjing 210024, China | 2010 | Science China(Technological Sciences)2010，53，11： | 11 |
| 15 | A continuous/discontinuous deformation analysis(CDDA)method based on deformable blocks for fracture modeling显示文摘In the framework of finite element meshes,a novel continuous/discontinuous deformation analysis(CDDA)method is proposed in this paper for modeling of crack problems.In the present CDDA,simple polynomial interpolations are defined at the deformable block elements,and a link element is employed to connect the adjacent block elements.The CDDA is particularly suitable for modeling the fracture propagation because the switch from continuous deformation analysis to discontinuous deformation analysis is natural and convenient without additional procedures.The SIFs(stress intensity factors)for various types of cracks,such as kinked cracks or curved cracks,can be easily computed in the CDDA by using the virtual crack extension technique(VCET).Both the formulation and implementation of the VCET in CDDA are simple and straightforward.Numerical examples indicate that the present CDDA can obtain high accuracy in SIF results with simple polynomial interpolations and insensitive to mesh sizes,and can automatically simulate the crack propagation without degrading accuracy. | Yongchang CAI Hehua ZHU Xiaoying ZHUANG | 2013 | Frontiers of Structural and Civil Engineering2013，7，4： | 10 |
| 16 | A novel vibration modeling method for a rotating blade with breathing cracks显示文摘This paper proposes a vibration modeling method for a rotating blade with breathing cracks, considering the coupling of the centrifugal effects, the breathing effects and the crack effects. Firstly, considering the combined effects of the centrifugal stress and the bending stress, a crack breathing model for the rotating blade is proposed. Since the crack surface cannot provide the spanwise centrifugal tensile stress, an additional bending moment will be generated at the crack surface in the rotating state.Therefore, an additional bending moment caused by the centrifugal stress is then constructed. In addition, due to the discontinuity of the crack cross section, the additional stiffness caused by the centrifugal effects of the cracked blade will be smaller than that of the normal blade. Therefore, a correction coefficient of the centrifugal stiffness is built. Furthermore, based on the Lagrange equation and the assumed modal method, the vibration equation of the rotating blade with a breathing crack is established(RBC model), and a strategy is constructed for solving this vibration equation. Finally, taking the finite element model(FEM) as a reference, the vibration responses of the RBC model, the open crack model(OC) and the bilinear crack model(BC) are compared. The necessity of the RBC model is illustrated, and the accuracy of the RBC model is verified. The RBC model is a computationally efficient alternative to the finite element analysis for the rotating cracked blade. It can provide an important tool for the vibration modeling and the vibration analysis of the rotating shaft-disk-blade system with cracked blades. | XIE JingSong ZI YanYang ZHANG MingQuan LUO QinYuan | 2019 | Science China(Technological Sciences)2019，62，2： | 10 |
| 17 | Experimental study about nano-deformation field near quasi-cleavage crack tip显示文摘Using the nano-moire method, we measure the near tip nanoscopic deformation on the {111 } plane of single crystal silicon with a loaded quasi-cleavage crack running in the [110] direction. The measured strain distribution ahead of the crack tip agrees with the linear elastic fracture mechanics prediction up to 10 nm from the crack tip. Dislocations of Peierls type are detected and they extend from the crack tip over a length of hundreds of Burgers vectors. | 邢永明 戴福隆 杨卫FML | 2000 | Science China Mathematics2000，43，9： | 10 |
| 18 | Analytical theory of flexural behavior of concrete beam reinforced with textile-combined steel显示文摘Textile-reinforced concrete (TRC) is a new high performance cementitious composite material,which not only has superior corrosion resistance but also can effectively limit the development of concrete cracks and make the crack width and spacing of concrete become smaller.However,due to the brittle feature of fiber materials,the TRC structural member has no distinct failure symptom when it arrives at its ultimate load.At the same time,ordinary reinforced concrete (RC) elements have large dead weight and can not efficiently restrict the expansion of the main crack of structures because of the restriction of their special cover thickness.In order to overcome the disadvantages of both the TRC and the RC,a new architecture reinforced with textile-combined steel is proposed in this study,making full use of the advantages of the above two structures.The cover concrete at the tension zone of an RC element is partially replaced with TRC and thus the steel reinforcements replaced with textiles are subtracted.Compared with the old one,the new structure has less dead weight and has the merits of service safety and good durability.The flexural development process of the proper beam with this new structure is investigated in this paper and based on the plane section assumption,analytical equations are derived by using nonlinear analysis theory,including the load-carrying capacity at different stages and moment-curvature relationship and mid-span deflection during the entire loading process.Comparison between the calculated and the experimental results reveals satisfactory agreement and thus verifies the feasibility of the equations. | XU ShiLang & YIN ShiPing Department of Civil Engineering,Dalian University of Technology,Dalian 116024,China | 2010 | Science China(Technological Sciences)2010，53，6： | 10 |
| 19 | Study on magnetic memory signals of medium carbon steel specimens with surface crack precut during loading process显示文摘Static tensile test and tensile-tensile fatigue test of medium carbon steel sheet specimens with surface crack precut were performed on MTS810 hydraulic testing machine to clear the meaning of the point of Hp(y) value zero. Magnetic memory signals were measured during the test process. The results show that only one point of Hp(y) zero value exists in all measured magnetic signal curves during the loading process, which should be a sign of intersection of positive-negative magnetic poles after magnetic ordered state appears and does not indicate the position of surface crack precut. The analysis shows that the surface crack precut can not interrupt the magnetic ordered state occurred during the test completely, hence its Hp(y) value is not zero. However, the crack extending to a penetrated defect at the instant of specimen′s fracture leads to the discontinuance of magnetic ordered state. | DONG Lihong XU Binshi DONG Shiyun YE Minghui CHEN Qunzhi | 2006 | Rare Metals2006，25，z1： | 9 |
| 20 | Influence of grain size on the small fatigue crack initiation and propagation behaviors of a nickel-based superalloy at 650℃显示文摘GH4169 at 650℃ in atmosphere was investigated by using single edge notch tensile specimens. The number of main cracks and crack initiation mechanisms at the notch surface strongly depended on the grain size. The crack initiation life accounted for more percentages of the total fatigue life for the alloy with smaller grain size. The fatigue life generally increased with increasing crack initiation life. The small crack transited to long crack when its length reached 10 times the grain size. | Xumin Zhu Congyang Gong Yun-Fei Jia Runzi Wang Chengcheng Zhang Yao Fu Shan-Tung Tu Xian-Cheng Zhang | 2019 | Journal of Materials Science & Technology2019，35，8： | 9 |
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