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Recent development in low-constraint fracture toughness testing for structural integrity assessment of pipelines

Jidong KANG, James A. GIANETTO, William R. TYSON

《机械工程前沿（英文）》 2018年 第13卷 第4期   页码 546-553 doi: 10.1007/s11465-018-0501-2

摘要：

Fracture toughness measurement is an integral part of structural integrity assessment of pipelines. Traditionally, a single-edge-notched bend (SE(B)) specimen with a deep crack is recommended in many existing pipeline structural integrity assessment procedures. Such a test provides high constraint and therefore conservative fracture toughness results. However, for girth welds in service, defects are usually subjected to primarily tensile loading where the constraint is usually much lower than in the three-point bend case. Moreover, there is increasing use of strain-based design of pipelines that allows applied strains above yield. Low-constraint toughness tests represent more realistic loading conditions for girth weld defects, and the corresponding increased toughness can minimize unnecessary conservatism in assessments. In this review, we present recent developments in low-constraint fracture toughness testing, specifically using single-edge-notched tension specimens, SENT or SE(T). We focus our review on the test procedure development and automation, round-robin test results and some common concerns such as the effect of crack tip, crack size monitoring techniques, and testing at low temperatures. Examples are also given of the integration of fracture toughness data from SE(T) tests into structural integrity assessment.

关键词： fracture toughness     constraint effect     single-edge-notched tension test     pipeline     structural integrity assessment    

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Identify the contribution of vehicle non-exhaust emissions: a single particle aerosol mass spectrometertest case at typical road environment

《环境科学与工程前沿（英文）》 2023年 第17卷 第5期 doi: 10.1007/s11783-023-1662-8

摘要：

● A single particle observation was conducted in a high traffic flow road environment.

关键词： Non-exhaust emissions     SPAMS     PMF     Roadside environment    

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Numerical analysis of bearing behaviors of single batter piles under horizontal loads in various directions

《结构与土木工程前沿（英文）》 2023年 第17卷 第2期   页码 224-237 doi: 10.1007/s11709-022-0914-1

摘要： The horizontal bearing behavior of a single batter pile (SBP) is vital to its application in practical engineering; however, the horizontal responses of SBPs change with the directions of horizontal loads, and this phenomenon is rarely investigated. Therefore, the directional differences in the horizontal bearing behaviors of SBPs are investigated in this study. Four model tests are conducted to preliminarily examine the effects of the skew angle of horizontal loads on the horizontal bearing capacities and distributions of the bending moments of the SBPs. Subsequently, the differences in the responses of the SBPs under horizontal loads in various directions at full scale are analyzed comprehensively via finite-element (FE) analysis. The effects of the skew angle on SBP-soil interaction are discussed. Moreover, an empirical design method is proposed based on the FE analysis results to predict the bearing ratios of SBPs in medium-dense and dense sand while considering the effects of the skew angle, batter angle, and pile diameter. The method is confirmed to be effective, as confirmed by the close agreement between the predicting results with the model test (reported in this study) and centrifuge model test results (reported in the literature).

关键词： single batter pile     skew horizontal load     model test     finite-element analysis     empirical design method    

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Progressive failure analysis of notched composite plate by utilizing macro mechanics approach

《结构与土木工程前沿（英文）》 2021年 第15卷 第3期   页码 623-642 doi: 10.1007/s11709-021-0726-8

摘要： In this study, gradual and sudden reduction methods were combined to simulate a progressive failure in notched composite plates using a macro mechanics approach. Using the presented method, a progressive failure is simulated based on a linear softening law prior to a catastrophic failure, and thereafter, sudden reduction methods are employed for modeling a progressive failure. This combination method significantly reduces the computational cost and is also capable of simultaneously predicting the first and last ply failures (LPFs) in composite plates. The proposed method is intended to predict the first ply failure (FPF), LPF, and dominant failure modes of carbon/epoxy and glass/epoxy notched composite plates. In addition, the effects of mechanical properties and different stacking sequences on the propagation of damage in notched composite plates were studied. The results of the presented method were compared with experimental data previously reported in the literature. By comparing the numerical and experimental data, it is revealed that the proposed method can accurately simulate the failure propagation in notched composite plates at a low computational cost.

关键词： progressive failure     notched composite plate     Hashin failure criterion     macro mechanics approach     finite element method    

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Behavior of dam concrete under biaxial compression-tension and triaxial compression-compression-tension

WANG Huailiang, SONG Yupu

《结构与土木工程前沿（英文）》 2008年 第2卷 第4期   页码 323-328 doi: 10.1007/s11709-008-0043-5

摘要： In order to meet the requirement for nonlinear analysis and design of mass concrete structures, the deformation behavior and strength of three-graded concrete specimens 250 mm × 250 mm × 400 mm with a maximum aggregate size of 80 mm and the corresponding wet-screened concrete specimens 150 mm × 150 mm × 300 mm with a maximum aggregate size of 40 mm were studied experimentally. Specimens subjected to biaxial compression-tension (C-T) and triaxial compression-compression-tension (C-C-T) stress states. Test data indicate that both the deformation and strength of the mass concrete specimens are lower than those of the corresponding wet-screened concrete small specimens, but the initial tangent modulus of the stress-strain curve of the former is greater than that of the latter. Test results show that the wet-screened effect and size effect of the specimens under complex stress states are obvious such that these should be considered in the design of mass concrete structures. In addition, respective failure criteria for mass concrete in principal stress space and octahedron stress space are proposed.

关键词： requirement     wet-screened concrete     compression-tension     maximum aggregate     principal    

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A new method of studying collapsibility of loess

Yuanqing ZHU , Zhenghan CHEN ,

《结构与土木工程前沿（英文）》 2009年 第3卷 第3期   页码 305-311 doi: 10.1007/s11709-009-0040-3

摘要： A new triaxial testing system that could control suction in wetting-induced collapsible tests was successfully developed to study the suction effects on wetting-induced collapsible deformation. The pedestal of the triaxial cell was made up of two parts, and the equipment not only could control suction but also could make water accessible to soil. A pressure/volume-controlled equipment was combined with the triaxial system to measure the water volume absorbed by samples accurately and to add pressure on water to filtrate into the sample. The apparatus could measure volume change precisely and keep the deviator stress unvaried, as well as measure the volume of water filtrating into the samples exactly. A triaxial collapsible testing procedure was described using the new apparatus for undisturbed collapsible loess with controlled suction. Furthermore, a series of double triaxial collapsible tests were conducted under different suctions and the same net cell pressure, and tests under different net cell pressures and the same suction were also done. It was indicated that the collapsible deformation increased with the increasing suction, and the effect of the net cell pressure on collapsible deformation was remarkable. The new triaxial apparatus was a useful facility to study the collapsible behavior of loess.

关键词： triaxial apparatus for collapsible soils     controlled suction     pressure/volume controlled equipment     double triaxial collapsible test     single triaxial collapsible test    

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Concepts and implementation of strain-based criteria in design codes for steel structures

Reidar BJORHOVDE

《结构与土木工程前沿（英文）》 2012年 第6卷 第3期   页码 210-216 doi: 10.1007/s11709-012-0165-7

摘要： A uniaxial tension test is commonly used to determine the mechanical properties of steel, but it has no meaning for the response of the material in a structure. The test was developed as a consensus solution by producers, fabricators, designers and code writers, to have a standard by which similar materials could be compared to a common base. It does not represent the actual behavior of the steel in a structure, and was never intended to do so. To study the true behavior of the structure and how the material responds it would be better to determine the strains and deformations that will take place during actual service condition. Such characteristics reflect the real behavior, whether in the elastic or inelastic range. If stresses or forces are needed, these are easily determined by the value of the strain and the relevant material modulus, along with the type of cross section, whether elastic or inelastic. The paper addresses the properties of a range of structural steels, how these are incorporated into design standards and how the standards define deformation characteristics and demands for bolted and welded connections.

关键词： steel     stress-strain characteristics     tension test     strain design     actual behavior     improved design codes    

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Evaluation of regenerative braking based on single-pedal control for electric vehicles

Wei LIU, Xintian LIU, Yansong WANG, Hongzhong QI

《机械工程前沿（英文）》 2020年 第15卷 第1期   页码 166-179 doi: 10.1007/s11465-019-0546-x

摘要： More than 25% of vehicle kinetic energy can be recycled under urban driving cycles. A single-pedal control strategy for regenerative braking is proposed to further enhance energy efficiency. Acceleration and deceleration are controlled by a single pedal, which alleviates driving intensity and prompts energy recovery. Regenerative braking is theoretically analyzed based on the construction of the single-pedal system, vehicle braking dynamics, and energy conservation law. The single-pedal control strategy is developed by considering daily driving conditions, and a single-pedal simulation model is established. Typical driving cycles are simulated to verify the effectiveness of the single-pedal control strategy. A dynamometer test is conducted to confirm the validity of the simulation model. Results show that using the single-pedal control strategy for electric vehicles can effectively improve the energy recovery rate and extend the driving range under the premise of ensuring safety while braking. The study lays a technical foundation for the optimization of regenerative braking systems and development of single-pedal control systems, which are conducive to the promotion and popularization of electric vehicles.

关键词： electric vehicle     single-pedal control     regenerative braking     co-simulation     dynamometer test    

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Seismic stability of earth slopes with tension crack

Yundong ZHOU, Fei ZHANG, Jingquan Wang, Yufeng GAO, Guangyu DAI

《结构与土木工程前沿（英文）》 2019年 第13卷 第4期   页码 950-964 doi: 10.1007/s11709-019-0529-3

摘要： Cracks at the crest of slopes frequently occur during earthquakes. Such cracks result from limited tension strength of the soil. A tension cut-off in Mohr-Coulomb shear strength can represent this limited strength. Presented is an extension of variational analysis of slope stability with a tension crack considering seismicity. Both translational and rotational failure mechanisms are included in a pseudo-static analysis of slope stability. Developed is a closed-form to assess the seismic stability of slopes with zero tensile strength. The results indicate that the presence of the tension crack has significant effects on the seismic stability of slopes, i.e. leading to small value of the yield acceleration. Considering soil tension strength in seismic slope analysis may lead to overestimation on the stability, as much as 50% for vertical slopes. Imposing tension crack results in transit of the critical failure mode to a straight line from a log-spiral, except for flat slopes with small soil cohesion. Under seismic conditions, large cohesion may increase the depth of crack, moving it closer to the slope.

关键词： slope stability     tension     crack     limit equilibrium     seismic effect    

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Release of elements from municipal solid waste incineration fly ash

Wei WANG, Lei ZHENG, Feng WANG, Xiao WAN, Keqing YIN, Xingbao GAO

《环境科学与工程前沿（英文）》 2010年 第4卷 第4期   页码 482-489 doi: 10.1007/s11783-010-0245-7

摘要： The element-release behavior of municipal solid waste incineration fly ash was explored through leaching test with continuous set-point pH (pH test) and serial single reaction cell (SSRC) tests. First, the relationship between element release and acid neutralizing capacity (ANC) consumption was examined with a pH test. Four types of release behaviors were identified which are characteristic for different elements: (1) release curves that were almost linear with ANC consumption (Ca, Zn, and Cd); (2) release that was significantly faster than ANC (Na, K, and Cl); (3) curves that featured a strong increase with ANC consumption, after a transient release, followed by an almost equal decrease (Si and S); and (4) release that is strongly retarded compared with ANC consumption (Cr, Cu, and Pb). In the SSRC system, it the existence of a pH front and a wash-out phenomenon is demonstrated. Combining the results from the SSRC test with the kinetic analysis of the ANC system in the pH test, it was inferred that less than one-third of the ANC measured from a batch pH titration plays a neutralization role in a field situation. The methodologies described may provide a powerful set of tools for systematic evaluation of element release from solid wastes.

关键词： pHstat test     Serial single reaction cell test (SSRC)     leaching     heavy metal    

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Surface tension of liquid metal: role, mechanism and application

Xi ZHAO, Shuo XU, Jing LIU

《能源前沿（英文）》 2017年 第11卷 第4期   页码 535-567 doi: 10.1007/s11708-017-0463-9

摘要： Surface tension plays a core role in dominating various surface and interface phenomena. For liquid metals with high melting temperature, a profound understanding of the behaviors of surface tension is crucial in industrial processes such as casting, welding, and solidification, etc. Recently, the room temperature liquid metal (RTLM) mainly composed of gallium-based alloys has caused widespread concerns due to its increasingly realized unique virtues. The surface properties of such materials are rather vital in nearly all applications involved from chip cooling, thermal energy harvesting, hydrogen generation, shape changeable soft machines, printed electronics to 3D fabrication, etc. owing to its pretty large surface tension of approximately 700 mN/m. In order to promote the research of surface tension of RTLM, this paper is dedicated to present an overview on the roles and mechanisms of surface tension of liquid metal and summarize the latest progresses on the understanding of the basic knowledge, theories, influencing factors and experimental measurement methods clarified so far. As a practical technique to regulate the surface tension of RTLM, the fundamental principles and applications of electrowetting are also interpreted. Moreover, the unique phenomena of RTLM surface tension issues such as surface tension driven self-actuation, modified wettability on various substrates and the functions of oxides are discussed to give an insight into the acting mechanism of surface tension. Furthermore, future directions worthy of pursuing are pointed out.

关键词： surface tension     liquid metal     soft machine     printed electronics     electrowetting     self-actuation    

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Correlation between tension softening relation and crack extension resistance in concrete

Xiufang ZHANG , Shilang XU ,

《结构与土木工程前沿（英文）》 2009年 第3卷 第3期   页码 323-329 doi: 10.1007/s11709-009-0041-2

摘要： Changes of the material fracture energy consumption with crack propagation can be described by a crack extension resistance curve, one of the fundamental fracture criteria in crack mechanics. Recently, experimental observation of the fracture behavior in concrete was used to develop a new fracture criterion, the crack extension resistance curve, to analyze crack propagation during the entire concrete fracture process. The variation of the crack extension resistance is mainly associated with the energy consumption in the fracture process zone ahead of the stress-free crack tip. The crack extension resistance is then a function of the softening curve, which is a basic mechanical property in the fracture process zone. The relationship between the softening curve and the crack extension resistance curve is then analyzed based on results of three-point bending beams tests. The results indicate that the characteristic points of the crack extension resistance curve is closely related to the characteristic point on used tension softening curve.

关键词： concrete     fracture process zone     crack extension GR resistance     tension softening curve    

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Edge preparation methods for cutting tools: a review

《机械工程前沿（英文）》 2023年 第18卷 第4期 doi: 10.1007/s11465-023-0766-y

摘要： Edge preparation can remove cutting edge defects, such as burrs, chippings, and grinding marks, generated in the grinding process and improve the cutting performance and service life of tools. Various edge preparation methods have been proposed for different tool matrix materials, geometries, and application requirements. This study presents a scientific and systematic review of the development of tool edge preparation technology and provides ideas for its future development. First, typical edge characterization methods, which associate the microgeometric characteristics of the cutting edge with cutting performance, are briefly introduced. Then, edge preparation methods for cutting tools, in which materials at the cutting edge area are removed to decrease defects and obtain a suitable microgeometry of the cutting edge for machining, are discussed. New edge preparation methods are explored on the basis of existing processing technologies, and the principles, advantages, and limitations of these methods are systematically summarized and analyzed. Edge preparation methods are classified into two categories: mechanical processing methods and nontraditional processing methods. These methods are compared from the aspects of edge consistency, surface quality, efficiency, processing difficulty, machining cost, and general availability. In this manner, a more intuitive understanding of the characteristics can be gained. Finally, the future development direction of tool edge preparation technology is prospected.

关键词： edge preparation method     preparation principle     cutting edge geometry     edge characterization     tool performance    

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Temperature and structural responses of a single-section utility tunnel throughout fire exposure

Yanmin YANG; Ying XIONG; Yongqing LI; Xiangkun MENG; Peng WANG; Tianyuan CAI

《结构与土木工程前沿（英文）》 2022年 第16卷 第10期   页码 1351-1364 doi: 10.1007/s11709-022-0857-6

摘要： In this study, fire tests of four single-section scaled-down utility tunnels were conducted. By analyzing temperature and structural responses of the utility tunnel throughout the fire exposure, the effects on the fire behavior of two different construction methods, cast-in-situ and prefabricated, and of two different materials, ordinary concrete and full lightweight concrete, were explored. The results of the study showed that the shear failure of the cast-in-situ utility tunnel occurred at the end of the top or bottom plate, and the failure of the prefabricated utility tunnel occurred at the junction of the prefabricated member and post-cast concrete. As the temperature increased, the temperature gradient along the thickness direction of the tunnel became apparent. The maximum temperature difference between the inner and outer wall surfaces was 531.7 °C. The highest temperature occurred in the cooling stage after stopping the heating, which provided a reference for the fire protection design and rescue of the utility tunnel. The displacement of the top plate of the prefabricated utility tunnel was 16.8 mm, which was 41.8% larger than that of the cast-in-situ utility tunnel. The bearing capacities of the ordinary concrete utility tunnel and full lightweight concrete utility tunnel after the fire loss were 27% and 16.8%, respectively. The full lightweight concrete utility tunnel exhibited good ductility and fire resistance and high collapse resistance.

关键词： full lightweight concrete     construction methods     temperature response     structural response     fire test    

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Calculation method of load distribution on pipe threaded connections under tension load

Shoujun CHEN, Lianxin GAO, Qi AN

《机械工程前沿（英文）》 2011年 第6卷 第2期   页码 241-248 doi: 10.1007/s11465-011-0219-x

摘要：

This paper presents a new calculation method that can calculate the load distribution on pipe threaded connections under tension load. On the basis of elastic mechanics, the new method was developed by analyzing each thread tooth, and a new deformation and covariant equation by making a mechanics analysis on each thread tooth was obtained. Compared with the traditional method proposed by the previous references, the new deformation and covariant equation could be used to describe the relation between the previous and the next thread tooth. By applying the new method on the sample of P-110S pipe threaded connection, the obtained results show that the load on thread tooth mainly concentrates on the four or five threads engaged and the middle teeth were not utilized well to bear the loads. The model offers a new way to calculate the loads carried on the thread teeth under tension load.

关键词： load distribution     calculation method     pipe threaded connections     tension load    

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标题 作者 时间 类型 操作

Recent development in low-constraint fracture toughness testing for structural integrity assessment of pipelines

Jidong KANG, James A. GIANETTO, William R. TYSON

期刊论文

Identify the contribution of vehicle non-exhaust emissions: a single particle aerosol mass spectrometertest case at typical road environment

期刊论文

Numerical analysis of bearing behaviors of single batter piles under horizontal loads in various directions

期刊论文

Progressive failure analysis of notched composite plate by utilizing macro mechanics approach

期刊论文

Behavior of dam concrete under biaxial compression-tension and triaxial compression-compression-tension

WANG Huailiang, SONG Yupu

期刊论文

A new method of studying collapsibility of loess

Yuanqing ZHU , Zhenghan CHEN ,

期刊论文

Concepts and implementation of strain-based criteria in design codes for steel structures

Reidar BJORHOVDE

期刊论文

Evaluation of regenerative braking based on single-pedal control for electric vehicles

Wei LIU, Xintian LIU, Yansong WANG, Hongzhong QI

期刊论文

Seismic stability of earth slopes with tension crack

Yundong ZHOU, Fei ZHANG, Jingquan Wang, Yufeng GAO, Guangyu DAI

期刊论文

Release of elements from municipal solid waste incineration fly ash

Wei WANG, Lei ZHENG, Feng WANG, Xiao WAN, Keqing YIN, Xingbao GAO

期刊论文

Surface tension of liquid metal: role, mechanism and application

Xi ZHAO, Shuo XU, Jing LIU

期刊论文

Correlation between tension softening relation and crack extension resistance in concrete

Xiufang ZHANG , Shilang XU ,

期刊论文

Edge preparation methods for cutting tools: a review

期刊论文

Temperature and structural responses of a single-section utility tunnel throughout fire exposure

Yanmin YANG; Ying XIONG; Yongqing LI; Xiangkun MENG; Peng WANG; Tianyuan CAI

期刊论文

Calculation method of load distribution on pipe threaded connections under tension load

Shoujun CHEN, Lianxin GAO, Qi AN

期刊论文