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疲劳 8

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催化裂化 2

桥面铺装 2

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Hierarchical approach for fatigue cracking performance evaluation in asphalt pavements

Ibrahim ONIFADE, Yared DINEGDAE, Björn BIRGISSON

《结构与土木工程前沿(英文)》 2017年 第11卷 第3期   页码 257-269 doi: 10.1007/s11709-017-0410-1

摘要: In this paper, a hierarchical approach is proposed for the evaluation of fatigue cracking in asphalt concrete pavements considering three different levels of complexities in the representation of the material behaviour, design parameters characterization and the determination of the pavement response as well as damage computation. Based on the developed hierarchical approach, three damage computation levels are identified and proposed. The levels of fatigue damage analysis provides pavement engineers a variety of tools that can be used for pavement analysis depending on the availability of data, required level of prediction accuracy and computational power at their disposal. The hierarchical approach also provides a systematic approach for the understanding of the fundamental mechanisms of pavement deterioration, the elimination of the empiricism associated with pavement design today and the transition towards the use of sound principles of mechanics in pavement analysis and design.

关键词: fatigue cracking     energy based     crack initiation     mechanistic approach     pavement analysis    

A dimensional analysis on asphalt binder fracture and fatigue cracking

Qian ZHAO, Zhoujing YE

《结构与土木工程前沿(英文)》 2018年 第12卷 第2期   页码 201-206 doi: 10.1007/s11709-017-0402-1

摘要: Fracture and fatigue cracking in asphalt binder are two of most serious problems for pavement engineers. In this paper, we present a new comprehensive approach, which consists both of dimensional analysis using Buckingham Theorem and -integral analysis based on classic fracture mechanics, to evaluate the fracture and fatigue on asphalt binder. It is discovered that the dimensional analysis could provide a new perspective to analyze the asphalt fracture and fatigue cracking mechanism.

关键词: Dimensional analysis     asphalt     fracture     fatigue cracking    

Cracking evolution behaviors of lightweight materials based on

Y. Luo, S. C. Wu, Y. N. Hu, Y. N. Fu

《机械工程前沿(英文)》 2018年 第13卷 第4期   页码 461-481 doi: 10.1007/s11465-018-0481-2

摘要:

Damage accumulation and failure behaviors are crucial concerns during the design and service of a critical component, leading researchers and engineers to thoroughly identifying the crack evolution. Third-generation synchrotron radiation X-ray computed microtomography can be used to detect the inner damage evolution of a large-density material or component. This paper provides a brief review of studying the crack initiation and propagation inside lightweight materials with advanced synchrotron three-dimensional (3D) X-ray imaging, such as aluminum materials. Various damage modes under both static and dynamic loading are elucidated for pure aluminum, aluminum alloy matrix, aluminum alloy metal matrix composite, and aluminum alloy welded joint. For aluminum alloy matrix, metallurgical defects (porosity, void, inclusion, precipitate, etc.) or artificial defects (notch, scratch, pit, etc.) strongly affect the crack initiation and propagation. For aluminum alloy metal matrix composites, the fracture occurs either from the particle debonding or voids at the particle/matrix interface, and the void evolution is closely related with fatigued cycles. For the hybrid laser welded aluminum alloy, fatigue cracks usually initiate from gas pores located at the surface or sub-surface and gradually propagate to a quarter ellipse or a typical semi-ellipse profile.

关键词: fatigue crack initiation and growth     fatigue damage mechanism     damage tolerance     defect characterization     laser welded aluminum alloys    

Innovative steel-UHPC composite bridge girders for long-span bridges

Xudong SHAO, Lu DENG, Junhui CAO

《结构与土木工程前沿(英文)》 2019年 第13卷 第4期   页码 981-989 doi: 10.1007/s11709-019-0531-9

摘要: Steel and steel-concrete composite girders are two types of girders commonly used for long-span bridges. However, practice has shown that the two types of girders have some drawbacks. For steel girders, the orthotropic steel deck (OSD) is vulnerable to fatigue cracking and the asphalt overlay is susceptible to damage such as rutting and pot holes. While for steel-concrete composite girders, the concrete deck is generally thick and heavy, and the deck is prone to cracking because of its low tensile strength and high creep. Thus, to improve the serviceability and durability of girders for long-span bridges, three new types of steel-UHPC lightweight composite bridge girders are proposed, where UHPC denotes ultra-high performance concrete. The first two types consist of an OSD and a thin UHPC layer while the third type consists of a steel beam and a UHPC waffle deck. Due to excellent mechanical behaviors and impressive durability of UHPC, the steel-UHPC composite girders have the advantages of light weight, high strength, low creep coefficient, low risk of cracking, and excellent durability, making them competitive alternatives for long-span bridges. To date, the proposed steel-UHPC composite girders have been applied to 14 real bridges in China. It is expected that the application of the new steel-UHPC composite girders on long-span bridges will have a promising future.

关键词: steel-UHPC composite bridge girder     long-span bridge     orthotropic steel deck     fatigue cracking     durability    

Effects of microfine aggregate in manufactured sand on bleeding and plastic shrinkage cracking of concrete

Branavan ARULMOLY; Chaminda KONTHESINGHA; Anura NANAYAKKARA

《结构与土木工程前沿(英文)》 2022年 第16卷 第11期   页码 1453-1473 doi: 10.1007/s11709-022-0877-2

摘要: Construction industries have started to utilize manufactured sand (MS) as an effective alternative for river sand in concrete. High-grade parent rocks are crushed to obtain MS, which also produces a considerable amount of microfine aggregate (MFA). The higher percentage of MFA could lead to both positive and negative effects on the performance of cement-based mixes. This research was done to examine the influence of varying MFA levels, specifically 0%, 3%, 6%, 9%, and 12% (by weight) as the partial replacements of MS on bleeding and plastic shrinkage cracking of concrete. In addition to the varying MFA levels, some concrete mixes also included fly ash (FA) and superplasticizer to investigate the effect of free-water content in the mixes. The bleeding test data were taken as on-site measurements, while the cracks from the plastic shrinkage cracking test were evaluated using an image processing technique. The results concluded that the MFA replacements and the effective water-to-cement ratio have a significant effect on the selected concrete properties. With the increasing replacement levels, cumulative bleeding and crack initiation life gradually decreased, while a progressive increase was observed for crack width, crack length, and crack area.

关键词: manufactured sand     fresh concrete     microfines     admixtures     shrinkage     cracking    

FUNCTIONAL GAIN OF FRUIT NETTED-CRACKING IN AN INTROGRESSION LINE OF TOMATO WITH HIGHER EXPRESSION OF

《农业科学与工程前沿(英文)》 2021年 第8卷 第2期

摘要:

Fruit cracking is a major disorder that affects the integrity of fruit and reduces the commercial value of tomato and other fleshy fruit. Here, we have found a novel fruit ‘netted-cracking’ (FNC) phenotype in tomato introgression line IL4-4 which is present in neither the donor parent (LA0716) nor the receptor parent (M82). An F2 population was generated by crossing IL4-4 with M82 to genetically characterize the FNC gene and this showed that a single dominant gene determined fruit netted-cracking. Further map-based cloning narrowed down the FNC locus to a 230 kb region on chromosome 4. Sequencing and annotation analysis show that FNC(Solyc04 g082540) was the most likely candidate gene. Functional characterization of FNC by overexpressing FNCAC and FNCIL4-4resulted in the fruit netted-cracking phenotype, suggesting that the FNC transcript level results in the functional gain of fruit netted-cracking. These findings were further confirmed by FNC ortholog in netted-cracking pepper and melon, indicating a common regulatory mechanism in different plant species. Furthermore, cytoplasm and nucleus-localized FNC indicates increased expression of genes involved in suberin, lignin, lipid transport and cell wall metabolism. These findings provide novel genetic insights into fruit netted-cracking and offer a way to promote molecular improvement toward cracking resistant cultivars.

 

关键词: fine mapping / fruit netted-cracking / introgression line / transcript level    

Theoretical study on the confine-stiffening effect and fractal cracking of square concrete filled steel

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1317-1336 doi: 10.1007/s11709-021-0763-3

摘要: Tension stress in steel-concrete composite is widely observed in engineering design. Based on an experimental program on tension performance of three square concrete-filled tubes (SCFT), the tension theory of SCFT is proposed using a mechanics-based approach. The tension stiffening effect, the confining strengthening effect and the confining stiffening effect, observed in tests of SCFTs are included in the developed tension theory model. Subsequently, simplified constitutive models of steel and concrete are proposed for the axial tension performance of SCFT. Based on the MSC.MARC software, a special fiber beam-column element is proposed to include the confining effect of SCFTs under tension and verified. The proposed analytical theory, effective formulas, and equivalent constitutive laws are extensively verified against three available tests reported in the literature on both global level (e.g., load-displacement curves) and strain level. The experimental verification proves the accuracy of the proposed theory and formulations in simulating the performance of SCFT members under tension with the capability to accurately predict the tensile strength and stiffness enhancements and realistically simulate the fractal cracking phenomenon.

关键词: square concrete filled tubes     confine-stiffening     confine-strengthening     fractal cracking     fracture    

Assessment of fatigue life of remanufactured impeller based on FEA

Lei XU,Huajun CAO,Hailong LIU,Yubo ZHANG

《机械工程前沿(英文)》 2016年 第11卷 第3期   页码 219-226 doi: 10.1007/s11465-016-0394-x

摘要:

Predicting the fatigue life of remanufactured centrifugal compressor impellers is a critical problem. In this paper, the S-N curve data were obtained by combining experimentation and theory deduction. The load spectrum was compiled by the rain-flow counting method based on the comprehensive consideration of the centrifugal force, residual stress, and aerodynamic loads in the repair region. A fatigue life simulation model was built, and fatigue life was analyzed based on the fatigue cumulative damage rule. Although incapable of providing a high-precision prediction, the simulation results were useful for the analysis of fatigue life impact factors and fatigue fracture areas. Results showed that the load amplitude greatly affected fatigue life, the impeller was protected from running at over-speed, and the predicted fatigue life was satisfied within the next service cycle safely at the rated speed.

关键词: remanufactured impeller     fatigue life     impeller failures     finite element analysis (FEA)    

南京长江第四大桥钢桥面铺装疲劳性能试验研究

詹俞,李国芬,王宏畅

《中国工程科学》 2013年 第15卷 第8期   页码 75-78

摘要:

结合南京长江第四大桥钢桥面铺装实体工程,开展铺装层混合料20 ℃疲劳性能试验。为了使试验结果能够更真实地反映主桥铺装的实际情况,直接采用主桥铺装使用的混合料成型试件,其中,带钢板复合梁试件为施工现场摊铺、碾压成型。室内试验对铺装结构单层采用劈裂疲劳试验,选择0.2、0.3、0.4、0.5、0.6这5个等级的应力水平,对组合结构采用带钢板复合梁疲劳试验,荷载水平为6 kN、7 kN、8 kN,并通过回归分析得到疲劳方程。

关键词: 道路工程     钢桥面铺装     疲劳性能     劈裂疲劳     疲劳方程    

Contact fatigue life prediction of a bevel gear under spectrum loading

Pan JIA, Huaiju LIU, Caichao ZHU, Wei WU, Guocheng LU

《机械工程前沿(英文)》 2020年 第15卷 第1期   页码 123-132 doi: 10.1007/s11465-019-0556-8

摘要: Rolling contact fatigue (RCF) issues, such as pitting, might occur on bevel gears because load fluctuation induces considerable subsurface stress amplitudes. Such issues can dramatically affect the service life of associated machines. An accurate geometry model of a hypoid gear utilized in the main reducer of a heavy-duty vehicle is developed in this study with the commercial gear design software MASTA. Multiaxial stress–strain states are simulated with the finite element method, and the RCF life is predicted using the Brown–Miller–Morrow fatigue criterion. The patterns of fatigue life on the tooth surface are simulated under various loading levels, and the RCF curve is numerically generated. Moreover, a typical torque–time history on the driven axle is described, followed by the construction of program load spectrum with the rain flow method and the Goodman mean stress equation. The effects of various fatigue damage accumulation rules on fatigue life are compared and discussed in detail. Predicted results reveal that the Miner linear rule provides the most optimistic result among the three selected rules, and the Manson bilinear rule produces the most conservative result.

关键词: bevel gear     rolling contact fatigue (RCF)     multiaxial fatigue criterion     load spectrum     damage accumulation rule    

Enhancing fatigue life of cylinder-crown integrated structure by optimizing dimension

Weiwei ZHANG,Xiaosong WANG,Zhongren WANG,Shijian YUAN

《机械工程前沿(英文)》 2015年 第10卷 第1期   页码 102-110 doi: 10.1007/s11465-015-0329-y

摘要:

Cylinder-crown integrated hydraulic press (CCIHP) is a new press structure. The hemispherical hydraulic cylinder also functions as a main portion of crown, which has lower weight and higher section modulus compared with the conventional hydraulic cylinder and press crown. As a result, the material strength capacity is better utilized. During the engineering design of cylinder-crown integrated structure, in order to increase the fatigue life, structural optimization on the basis of the adaptive macro genetic algorithms (AMGA) is first conducted to both reduce weight and decrease peak stress. It is shown that the magnitude of the maximum principal stress is decreased by 28.6%, and simultaneously the total weight is reduced by 4.4%. Subsequently, strain-controlled fatigue test is carried out, and the stress-strain hysteresis loops and cyclic hardening curve are obtained. Based on linear fit, the fatigue properties are calculated and used for the fatigue life prediction. It is shown that the predicted fatigue life is significantly increased from 157000 to 1070000 cycles after structural optimization. Finally, according to the optimization design, a 6300 kN CCIHP has been manufactured, and priority application has been also suggested.

关键词: cylinder-crown integrated hydraulic press (CCIHP)     adaptive macro genetic algorithms (AMGA)     strain-controlled fatigue test    

腐蚀环境下飞机结构疲劳寿命的分析方法

穆志韬

《中国工程科学》 2002年 第4卷 第3期   页码 68-72

摘要:

依据海军现役飞机的腐蚀环境特点及结构件腐蚀损伤深度拟合规律,采用应力场强法和局部应力应变法分别对疲劳缺口系数Kf及疲劳寿命计算模型进行了分析,提出了一种腐蚀环境下飞机结构疲劳寿命的评定方法。该方法以室温大气环境下的寿命评定结论为依据,考虑了结构件腐蚀损伤后潮湿空气、盐雾、盐雾+SO2等环境介质对疲劳寿命的影响,并结合国产某型飞机机翼前梁缘条腐蚀损伤部位的疲劳寿命及剩余寿命估算实例进行了分析。

关键词: 飞机结构     疲劳寿命     腐蚀环境     疲劳缺口系数    

Influence of surface cracking, anchor head profile, and anchor head size on cast-in headed anchors in

《结构与土木工程前沿(英文)》   页码 1163-1187 doi: 10.1007/s11709-023-0987-5

摘要: In this study, the concrete cone capacity, concrete cone angle, and load–displacement response of cast-in headed anchors in geopolymer concrete are explored using numerical analyses. The concrete damaged plasticity (CDP) model in ABAQUS is used to simulate the behavior of concrete substrates. The tensile behavior of anchors in geopolymer concrete is compared with that in normal concrete as well as that predicted by the linear fracture mechanics (LFM) and concrete capacity design (CCD) models. The results show that the capacity of the anchors in geopolymer concrete is 30%–40% lower than that in normal concrete. The results also indicate that the CCD model overestimates the capacity of the anchors in geopolymer concrete, whereas the LFM model provides a much more conservative prediction. The extent of the difference between the predictions by the numerical analysis and those of the above prediction models depends on the effective embedment depth of the anchor and the anchor head size. The influence of concrete surface cracking on the capacity of the anchor is shown to depend on the location of the crack and the effective embedment depth. The influence of the anchor head profile on the tensile capacity of the anchors is found to be insignificant.

关键词: cast-in anchor     concrete cone capacity     geopolymer concrete     head size     surface crack     anchor profile    

Investigation of fatigue resistance of fillet-welded tube connection details for sign support structures

Hyungjoo CHOI, Husam NAJM

《结构与土木工程前沿(英文)》 2020年 第14卷 第1期   页码 199-214 doi: 10.1007/s11709-019-0592-9

摘要: Stiffened and unstiffened fillet-welded tube-to-transverse plate connection details are widely used for mast-arm and base-plate connections for highway sign structures. However, due to repetitive wind loads, cyclic fatigue stresses are induced and they are the primary source of failure in welded connections at these locations. The resistance of fatigue critical details has been an on-going research topic because of limited experimental results and the variability in existing fatigue testing results. The main objective of this study is to evaluate fatigue resistance of fillet-welded tube connection details by utilizing the advanced fatigue tool in ANSYS Workbench platform. Finite Element (FE) models development and model validation using existing test data was presented. The resulting fatigue resistance from FE analysis was expressed in terms of fatigue life, fatigue damage, and fatigue safety factor to determine the fatigue performance of fillet-welded connections. Existing fatigue test data was grouped to perform a synthetic analysis and then analysis results were provided to determine input data and fatigue limit for the fatigue module. The local stress level at fatigue critical locations was evaluated using a static FE model for different number of stiffeners and boundary conditions. The results of this investigation provides fatigue resistance of fillet-welded connection details in the form of fatigue life, fatigue damage and safety factor for various connection parameters and structural conditions.

关键词: fatigue     weld connections     base plate     fillet welds    

催化裂解架起了炼油与化工之间的桥梁

李再婷

《中国工程科学》 1999年 第1卷 第2期   页码 67-71

摘要:

催化裂解是以石油中的重油为原料,用催化方法生产丙烯等基本有机化工原料的技术。在世界上我国首先研究开发了此新工艺及催化剂,并于1990年成功进行了工业示范。迄今,国内外已有七套应用该技术的工业装置建成并投产。生产的丙烯等化工原料已分别用来合成了高质量的聚丙烯、聚乙烯及丙烯腈等化学品。目前催化裂解已可应用更重质的原料,如常压渣油,并开发出能适合不同原料的多种催化剂。文中重点介绍了应用该技术在泰国建成的一套催化裂解装置的生产情况。

关键词: 催化裂解     石油化学工业     丙烯     异丁烯    

标题 作者 时间 类型 操作

Hierarchical approach for fatigue cracking performance evaluation in asphalt pavements

Ibrahim ONIFADE, Yared DINEGDAE, Björn BIRGISSON

期刊论文

A dimensional analysis on asphalt binder fracture and fatigue cracking

Qian ZHAO, Zhoujing YE

期刊论文

Cracking evolution behaviors of lightweight materials based on

Y. Luo, S. C. Wu, Y. N. Hu, Y. N. Fu

期刊论文

Innovative steel-UHPC composite bridge girders for long-span bridges

Xudong SHAO, Lu DENG, Junhui CAO

期刊论文

Effects of microfine aggregate in manufactured sand on bleeding and plastic shrinkage cracking of concrete

Branavan ARULMOLY; Chaminda KONTHESINGHA; Anura NANAYAKKARA

期刊论文

FUNCTIONAL GAIN OF FRUIT NETTED-CRACKING IN AN INTROGRESSION LINE OF TOMATO WITH HIGHER EXPRESSION OF

期刊论文

Theoretical study on the confine-stiffening effect and fractal cracking of square concrete filled steel

期刊论文

Assessment of fatigue life of remanufactured impeller based on FEA

Lei XU,Huajun CAO,Hailong LIU,Yubo ZHANG

期刊论文

南京长江第四大桥钢桥面铺装疲劳性能试验研究

詹俞,李国芬,王宏畅

期刊论文

Contact fatigue life prediction of a bevel gear under spectrum loading

Pan JIA, Huaiju LIU, Caichao ZHU, Wei WU, Guocheng LU

期刊论文

Enhancing fatigue life of cylinder-crown integrated structure by optimizing dimension

Weiwei ZHANG,Xiaosong WANG,Zhongren WANG,Shijian YUAN

期刊论文

腐蚀环境下飞机结构疲劳寿命的分析方法

穆志韬

期刊论文

Influence of surface cracking, anchor head profile, and anchor head size on cast-in headed anchors in

期刊论文

Investigation of fatigue resistance of fillet-welded tube connection details for sign support structures

Hyungjoo CHOI, Husam NAJM

期刊论文

催化裂解架起了炼油与化工之间的桥梁

李再婷

期刊论文