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Tribological study on the surface modification of metal-on-polymer bioimplants

《机械工程前沿（英文）》 2022年 第17卷 第2期 doi: 10.1007/s11465-022-0682-6

摘要： The tribological performance of artificial joints is regarded as the main factor of the lifespan of implanted prostheses. The relationship between surface roughness and coefficient of friction (COF) under dry and lubricated conditions is studied. Results show that under dry test, friction coefficient is not reduced all the time with a decrease in surface roughness. On the contrary, a threshold of roughness value is observed, and frictional force increases again below this value. This critical value lies between 40 and 100 nm in Sa (roughness). This phenomenon is due to the transfer of friction mechanisms from abrasion to adhesion. Under wet test, COF always decreases with reduction in surface roughness. This result is mainly attributed to the existence of a thin layer of lubricant film that prevents the intimate contact of two articulating surfaces, thus greatly alleviating adhesion friction. Furthermore, surface texturing technology is successful in improving the corresponding tribological performance by decreasing friction force and mitigating surface deterioration. The even-distribution mode of texturing patterns is most suitable for artificial joints. By obtaining the optimal surface roughness and applying texturing technology, the tribological performance of polymer-based bioimplants can be greatly enhanced.

关键词： artificial joints     surface roughness     friction     surface texturing    

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Design and simulation of a cable-pulley-based transmission for artificial ankle joints

Huaxin LIU,Marco CECCARELLI,Qiang HUANG

《机械工程前沿（英文）》 2016年 第11卷 第2期   页码 170-183 doi: 10.1007/s11465-016-0383-0

摘要：

In this paper, a mechanical transmission based on cable pulley is proposed for human-like actuation in the artificial ankle joints of human-scale. The anatomy articular characteristics of the human ankle is discussed for proper biomimetic inspiration in designing an accurate, efficient, and robust motion control of artificial ankle joint devices. The design procedure is presented through the inclusion of conceptual considerations and design details for an interactive solution of the transmission system. A mechanical design is elaborated for the ankle joint angular with pitch motion. A multi-body dynamic simulation model is elaborated accordingly and evaluated numerically in the ADAMS environment. Results of the numerical simulations are discussed to evaluate the dynamic performance of the proposed design solution and to investigate the feasibility of the proposed design in future applications for humanoid robots.

关键词： biomimetic designs     ankle joints     cable-pulley transmissions     multi-body dynamic simulation     numerical characterization    

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Conceptual design of compliant translational joints for high-precision applications

Guangbo HAO,Haiyang LI,Xiuyun HE,Xianwen KONG

《机械工程前沿（英文）》 2014年 第9卷 第4期   页码 331-343 doi: 10.1007/s11465-014-0321-y

摘要：

Compliant translational joints (CTJs) have been extensively used in precision engineering and microelectromechanical systems (MEMS). There is an increasing need for designing higher-performance CTJs. This paper deals with the conceptual design of CTJs via three approaches: parallelogram based method, straight-line motion mechanism based method and combination based method. Typical emerging CTJ designs are reviewed by explaining their design principles and qualitatively analyzing their characteristics. New CTJs are proposed using three approaches, including an asymmetric double parallelogram mechanism with slaving mechanism, several compact and symmetric double parallelogram mechanisms with slaving mechanisms and a general CTJ using the center drift compensation and a CTJ using Roberts linkage and several combination designs. This paper provides an overview of the current advances/progresses of CTJ designs and lays the foundation for further optimization, quantitative analysis and characteristic comparisons.

关键词： compliant mechanisms     translational joints     conceptual design     parallelogram     straight-line motion     combination method    

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Discontinuous mechanical behaviors of existing shield tunnel with stiffness reduction at longitudinal joints

《结构与土木工程前沿（英文）》 2023年 第17卷 第1期   页码 37-52 doi: 10.1007/s11709-022-0920-3

摘要： An analytical model is proposed to estimate the discontinuous mechanical behavior of an existing shield tunnel above a new tunnel. The existing shield tunnel is regarded as a Timoshenko beam with longitudinal joints. The opening and relative dislocation of the longitudinal joints can be calculated using Dirac delta functions. Compared with other approaches, our method yields results that are consistent with centrifugation test data. The effects of the stiffness reduction at the longitudinal joints (α and β), the shearing stiffness of the Timoshenko beam GA, and different additional pressure profiles on the responses of the shield tunnel are investigated. The results indicate that our proposed method is suitable for simulating the discontinuous mechanical behaviors of existing shield tunnels with longitudinal joints. The deformation and internal forces decrease as α, β, and GA increase. The bending moment and shear force are discontinuous despite slight discontinuities in the deflection, opening, and dislocation. The deflection curve is consistent with the additional pressure profile. Extensive opening, dislocation, and internal forces are induced at the location of mutation pressures. In addition, the joints allow rigid structures to behave flexibly in general, as well as allow flexible structures to exhibit locally rigid characteristics. Owing to the discontinuous characteristics, the internal forces and their abrupt changes at vulnerable sections must be monitored to ensure the structural safety of existing shield tunnels.

关键词： tunnel–soil interaction     discontinuous analysis     longitudinal joints     existing shield tunnel     Timoshenko beam     Dirac delta function    

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Seismic behavior experimental study of frame joints with special-shaped column and dispersed steel bar

Shuchun LI, Bo DIAO, Youpo SU,

《结构与土木工程前沿（英文）》 2009年 第3卷 第4期   页码 378-383 doi: 10.1007/s11709-009-0064-8

摘要： To overcome the problem that steel bars are put too close at a flame joint with special-shaped beam and column, mechanical performance of three groups of six RC flame joints with special-shaped (L, T and+) column and dispersed-steel bars-beam on the top floor under cyclic loads were studied. Experimental comparison was conducted between special-shaped (L, T and+) column and normal beams. The cracking load, yielding load, ultimate bearing capacity, failure patterns, and hysteretic properties at joint core area were investigated. The seismic behaviors of the joints with different proportions of dispersed-steel-bar beams were analyzed. The results of experimental analysis indicate that the mechanical and seismic behaviors of frame joints with T-shaped and+-shaped column are nearly not changed when suitable proportion steel bars are dispersed to flange plane. Stiffness degeneration of flame joint with L-shaped column is rather serious due to concrete damage stiffness. Theoretical result indicates that distributing area of the dispersed steel-bar beams in the flange plate should be strictly controlled to avoid anchor destroy.

关键词： beam with dispersed steel bar     flame joints with special-shaped beam and column     seismic behavior     scale of dispersed steel bars    

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Experimental and numerical analysis of beam to column joints in steel structures

Gholamreza ABDOLLAHZADEH, Seyed Mostafa SHABANIAN

《结构与土木工程前沿（英文）》 2018年 第12卷 第4期   页码 642-661 doi: 10.1007/s11709-017-0457-z

摘要： The behaviors such as extreme non-elastic response, constant changes in roughness and resistance, as well as formability under extreme loads such as earthquakes are the primary challenges in the modeling of beam-to-column connections. In this research, two modeling methods including mechanical and neural network methods have been presented in order to model the complex hysteresis behavior of beam-to-column connections with flange plate. First, the component-based mechanical model will be introduced in which every source of transformation has been shown only with geometrical and material properties. This is followed by the investigation of a neural network method for direct extraction of information out of experimental data. For the validation of behavioral curves as well as training of the neural network, the experiments were carried out on samples with real dimensions of beam-to-column connections with flange plate in the laboratory. At the end, the combinational modeling framework is presented. The comparisons reveal that the combinational modeling is able to display the complex narrowed hysteresis behavior of the beam-to-column connections with flange plate. This model has also been successfully employed for the prediction of the behavior of a newly designed connection.

关键词： beam to column connections     experiments     component method     neural network model     combinational modeling    

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Weakening behavior of waterproof performance in joints of shield tunnels under adjacent constructions

《结构与土木工程前沿（英文）》   页码 884-900 doi: 10.1007/s11709-022-0912-3

摘要： Groundwater leakage in shield tunnels poses a threat to the safety and durability of tunnel structures. Disturbance of adjacent constructions during the operation of shield tunnels frequently occurs in China, leading to deformation of tunnel lining and leakage in joints. Understanding the impact of adjacent constructions on the waterproofing performance of the lining is critical for the protection of shield tunnels. In this study, the weakening behavior of waterproof performance was investigated in the joints of shield tunnels under transverse deformation induced by adjacent construction. First, the relationship between the joint opening and transverse deformation under three typical adjacent constructions (upper loading, upper excavation, and side excavation) was investigated via elaborate numerical simulations. Subsequently, the evolution of the waterproof performance of a common gasket with a joint opening was examined by establishing a coupled Eulerian–Lagrangian model of joint seepage, and a formula describing the relationship between waterproof performance and joint opening was proposed. Finally, the weakening law of waterproofing performance was investigated based on the results of the aforementioned studies. It was determined that the joints with the greatest decline in waterproof performance were located at the tunnel shoulder in the upper loading case, tunnel crown in the upper excavation case, and tunnel shoulder in the side excavation case. When the waterproof performance of these joints decreased to 50% and 30%, the transverse deformations were 60 and 90 mm under upper loading, 90 and 140 mm under upper excavation, and 45 and 70 mm under side excavation, respectively. The results provide a straightforward reference for setting a controlled deformation standard considering the waterproof performance.

关键词： shield tunnel     waterproof performance     horizontal transverse deformation     joint opening     weakening behavior    

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Large-scale model test study on the water pressure resistance of construction joints of karst tunnel

《结构与土木工程前沿（英文）》   页码 1249-1263 doi: 10.1007/s11709-023-0974-x

摘要： Model tests and numerical calculations were adopted based on the New Yuanliangshan tunnel project to investigate the water pressure resistance of lining construction joints in high-pressure and water-rich karst tunnels. A large-scale model test was designed and conducted, innovatively transforming the external water pressure of the lining construction joint into internal water pressure. The effects of the embedded position and waterstop type on the water pressure resistance of the construction joint were analyzed, and the reliability of the model test was verified via numerical calculations. The results show that using waterstops can significantly improve the water pressure resistance of lining construction joints. The water pressure resistance of the lining construction joint is positively correlated with the lining thickness and embedded depth of the waterstop. In addition, the type of waterstop significantly influences the water pressure resistance of lining construction joints. The test results show that the water pressure resistance of the embedded transverse reinforced waterstop is similar to that of the steel plate waterstop, and both have more advantages than the rubber waterstop. The water pressure resistance of the construction joint determined via numerical calculations is similar to the model test results, indicating that the model test results have high accuracy and reliability. This study provides a reference for similar projects and has wide applications.

关键词： karst tunnel     lining construction joint     water pressure resistance     large-scale model test     numerical calculations    

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Numerical analysis of aluminum alloy reticulated shells with gusset joints under fire conditions

《结构与土木工程前沿（英文）》 2023年 第17卷 第3期   页码 448-466 doi: 10.1007/s11709-022-0910-5

摘要： In this study, a numerical analysis was conducted on aluminum alloy reticulated shells (AARSs) with gusset joints under fire conditions. First, a thermal-structural coupled analysis model of AARSs considering joint semi-rigidity was proposed and validated against room-temperature and fire tests. The proposed model can also be adopted to analyze the fire response of other reticulated structures with semi-rigid joints. Second, a parametric analysis was conducted based on the numerical model to explore the buckling behavior of K6 AARS with gusset joints under fire conditions. The results indicated that the span, height-to-span ratio, height of the supporting structure, and fire power influence the reduction factor of the buckling capacity of AARSs under fire conditions. In contrast, the reduction factor is independent of the number of element divisions, number of rings, span-to-thickness ratio, and support condition. Subsequently, practical design formulae for predicting the reduction factor of the buckling capacity of K6 AARSs were derived based on numerical analysis results and machine learning techniques to provide a rapid evaluation method. Finally, further numerical analyses were conducted to propose practical design suggestions, including the conditions of ignoring the ultimate bearing capacity analysis of K6 AARS and ignoring the radiative heat flux.

关键词： aluminum alloy reticulated shell     gusset joint     numerical analysis     fire resistance    

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Effect of strata restraint on seismic performance of prefabricated sidewall joints in fabricated subway

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 763-779 doi: 10.1007/s11709-023-0917-6

摘要： A disadvantage of the conventional quasi-static test method is that it does not consider the soil restraint effect. A new method to test the seismic performance of prefabricated specimens for underground assembled structures is proposed, which can realistically reflect the strata restraint effect on the underground structure. Laboratory work combined with finite element (FE) analysis is performed in this study. Three full-scale sidewall specimens with different joint forms are designed and fabricated. Indices related to the seismic performance and damage modes are analyzed comprehensively to reveal the mechanism of the strata restraint effect on the prefabricated sidewall components. Test results show that the strata restraint effect effectively improves the energy dissipation capacity, load-bearing capacity, and the recoverability of the internal deformation of the precast sidewall components. However, the strata restraint effect reduces the ductility of the precast sidewall components and aggravates the shear and bending deformations in the core region of the connection joints. Additionally, the strata restraint effect significantly affects the seismic performance and damage mode of the prefabricated sidewall components. An FE model that can be used to conduct a seismic performance study of prefabricated specimens for underground assembled structures is proposed, and its feasibility is verified via comparison with test data.

关键词： underground structures     precast sidewall specimen     seismic test method     bearing capacity     energy dissipation capacity     plastic deformation    

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Assessment of bridge expansion joints using long-term displacement measurement under changing environmental

Youliang DING, Aiqun LI

《结构与土木工程前沿（英文）》 2011年 第5卷 第3期   页码 374-380 doi: 10.1007/s11709-011-0122-x

摘要： This paper addresses the problem of condition assessment of bridge expansion joints using long-term measurement data under changing environmental conditions. The effects of temperature, traffic loading and wind on the expansion joint displacements are analyzed and interpreted, which reveal that measured displacements are observed to increase with an increase in temperature and to decrease with increased traffic loading, while the correlation between displacement and wind speed is very weak. Two regression models are developed to simulate the varying displacements under the changes in temperature and traffic loadings. Based on these models, the effects of the environmental conditions are removed to obtain the normalized displacement. Statistical process control using mean value control charts is further used to detect damage to the bridge expansion joints. The results reveal that the proposed method had a good capability for detecting the damage-induced 1.0% variances of the annual changes in the expansion joint displacements.

关键词： structural health monitoring     displacement     expansion joint     temperature effect     wind effect     traffic loading     statistical process control     suspension bridge    

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Brazing of ceramic-to-ceramic and ceramic-to-metal joints in air

Kirsten BOBZIN, Thomas SCHLAEFER, Lidong ZHAO, Nils KOPP, Arne SCHLEGEL

《机械工程前沿（英文）》 2010年 第5卷 第2期   页码 125-129 doi: 10.1007/s11465-010-0007-z

摘要： Reactive air brazing (RAB) is an emerging technology for the production of ceramic-to-ceramic and ceramic-to-metal joints. In this study, RAB was investigated with respect to the potential applications for solid oxide fuel cells (SOFCs) as one example of use. It was found that alumina could be well brazed by RAB with AgCu and AgCuTi brazes. Both braze composition and brazing temperature influenced significantly the wetting behavior and their mechanism of wetting. AgCu and AgCuTi braze alloys could also be used to produce brazed joints with the SOFC materials ceramic yttria stabilized zirconia and steel X1CrTiLa22. However, CuO reacts with the steel, forming a brittle oxide layer on the steel surface, which is undesirable for SOFC applications. The first trials with Ag0.5Al showed a promising solution.

关键词： reactive air brazing (RAB)     X1CrTiLa22     Al2O3     yttria stabilized zirconia (YSZ)     solid oxide fuel cell (SOFC)    

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Investigation of the interior RC beam-column joints under monotonic antisymmetrical load

Fei GAO, Zhiqiang TANG, Biao HU, Junbo CHEN, Hongping ZHU, Jian MA

《结构与土木工程前沿（英文）》 2019年 第13卷 第6期   页码 1474-1494 doi: 10.1007/s11709-019-0572-0

摘要： The paper presents numerical findings of reinforced concrete interior beam-column joints under monotonic antisymmetrical load. The finite element models considered compression and tension damage were calibrated by test results in terms of the load-displacement, failure modes, and strains of longitudinal steel. The emphasis was put on studying the effects of hoop reinforcement ratio in joint core and the axial compression ratio on the responses of the joints. The results show that, in addition to the truss and strut-and-tie mechanisms, the confinement mechanism also existed in the joint core. A certain amount of stirrup is not only able to enhance the confinement in joint core, undertake a part of shear force and thus to increase the shear capacity, prevent the outward buckling of steel bars in column, improve the stress distribution in joint core, delay cracking and restrain the propagation of cracks, but also to increase the yield load, decrease the yield displacement of beam and improve the joint ductility. However, excessive horizontal stirrups contribute little to the joint performance. In a certain range, larger axial compression ratio is beneficial for the joint mechanical behavior, while it is negative when axial compression ratio is too large.

关键词： RC beam-column joint     reinforcement ratio in joint core     axial compression ratio     finite element     test    

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K型钢管混凝土节点疲劳性能试验研究

钟新谷,杨胜,石卫华

《中国工程科学》 2011年 第13卷 第9期   页码 97-100

摘要：

以湘潭四大桥桁架拱为工程背景，进行了三种规格的K型钢管混凝土节点的疲劳试验，基于热点应力计算了K型钢管混凝土节点的疲劳荷载幅值，表明热点应力法能够较好地评估钢管混凝土节点的疲劳寿命；试验表明K型钢管混凝土节点的疲劳性能明显优于K型钢管节点。在此基础上初步提出了K型钢管混凝土节点的S—N曲线，对建立K型钢管混凝土节点疲劳寿命设计准则具有一定的参考意义。

关键词： K型钢管混凝土节点     疲劳性能     S—N曲线    

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A toughness based deformation limit for X- and K-joints under brace axial tension

Bo GU,Xudong QIAN,Aziz AHMED

《结构与土木工程前沿（英文）》 2016年 第10卷 第3期   页码 345-362 doi: 10.1007/s11709-016-0333-2

摘要： This study reports a deformation limit for the initiation of ductile fracture failure in fatigue-cracked circular hollow section (CHS) X- and K-joints subjected to brace axial tension. The proposed approach sets the deformation limit as the numerically computed crack driving force in a fatigue crack at the hot-spot location in the tubular joint reaches the material fracture toughness measured from standard fracture specimens. The calibration of the numerical procedure predicates on reported numerical computations on the crack driving force and previously published verification study against large-scale CHS X-joints with fatigue generated surface cracks. The development of the deformation limit includes a normalization procedure, which covers a wide range of the geometric parameters and material toughness levels. The lower-bound deformation limits thus developed follow a linear relationship with respect to the crack-depth ratio for both X- and K-joints. Comparison of the predicated deformation limit against experimental on cracked tubular X- and K-joints demonstrates the conservative nature of the proposed deformation limit. The proposed deformation limit, when extrapolated to a zero crack depth, provides an estimate on the deformation limits for intact X- and K-joints under brace axial loads.

关键词： circular hollow section (CHS)     tubular joint     fracture failure     deformation limit     J-integral    

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标题 作者 时间 类型 操作

Tribological study on the surface modification of metal-on-polymer bioimplants

期刊论文

Design and simulation of a cable-pulley-based transmission for artificial ankle joints

Huaxin LIU,Marco CECCARELLI,Qiang HUANG

期刊论文

Conceptual design of compliant translational joints for high-precision applications

Guangbo HAO,Haiyang LI,Xiuyun HE,Xianwen KONG

期刊论文

Discontinuous mechanical behaviors of existing shield tunnel with stiffness reduction at longitudinal joints

期刊论文

Seismic behavior experimental study of frame joints with special-shaped column and dispersed steel bar

Shuchun LI, Bo DIAO, Youpo SU,

期刊论文

Experimental and numerical analysis of beam to column joints in steel structures

Gholamreza ABDOLLAHZADEH, Seyed Mostafa SHABANIAN

期刊论文

Weakening behavior of waterproof performance in joints of shield tunnels under adjacent constructions

期刊论文

Large-scale model test study on the water pressure resistance of construction joints of karst tunnel

期刊论文

Numerical analysis of aluminum alloy reticulated shells with gusset joints under fire conditions

期刊论文

Effect of strata restraint on seismic performance of prefabricated sidewall joints in fabricated subway

期刊论文

Assessment of bridge expansion joints using long-term displacement measurement under changing environmental

Youliang DING, Aiqun LI

期刊论文

Brazing of ceramic-to-ceramic and ceramic-to-metal joints in air

Kirsten BOBZIN, Thomas SCHLAEFER, Lidong ZHAO, Nils KOPP, Arne SCHLEGEL

期刊论文

Investigation of the interior RC beam-column joints under monotonic antisymmetrical load

Fei GAO, Zhiqiang TANG, Biao HU, Junbo CHEN, Hongping ZHU, Jian MA

期刊论文

K型钢管混凝土节点疲劳性能试验研究

钟新谷,杨胜,石卫华

期刊论文

A toughness based deformation limit for X- and K-joints under brace axial tension

Bo GU,Xudong QIAN,Aziz AHMED

期刊论文