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Bending and rotational behaviour of semi-continuous composite beams

WANG Jingfeng, LI Guoqiang

《结构与土木工程前沿(英文)》 2008年 第2卷 第2期   页码 116-122 doi: 10.1007/s11709-008-0015-9

摘要: Stresses and deflections were measured in various semi-continuous composite beams. The bending and rotational capacities of the composite connections were measured in terms of beam curvatures and deflections by using two full-scale semi-rigid composite frames with monotonic loadings. The effect of semi-rigid connections on the performance of composite beams with various loadings was compared with predictions and codes. The tests show that the semi-continuous composite beams are more economic and effective than the simple or continuous composite beams. The semi-rigid connections affect the bending capacities and beam deflections, so the connection behavior should be considered in the design of composite beams. Yielding analysis of the steel beam bottom flange has some influence on the deflection calculation of composite beams.

关键词: rotational     effective     deflection calculation     semi-continuous composite     full-scale semi-rigid    

Implementation of total Lagrangian formulation for the elasto-plastic analysis of plane steel frames exposed to fire

Bing XIA, Yuching WU, Zhanfei HUANG

《结构与土木工程前沿(英文)》 2012年 第6卷 第3期   页码 257-266 doi: 10.1007/s11709-012-0163-9

摘要: In this paper, the co-rotational total Lagrangian forms of finite element formulations are derived to perform elasto-plastic analysis for plane steel frames that either experience increasing external loading at ambient temperature or constant external loading at elevated temperatures. Geometric nonlinearities and thermal-expansion effects are considered. A series of programs were developed based on these formulations. To verify the accuracy and efficiency of the nonlinear finite element programs, numerical benchmark tests were performed, and the results from these tests are in a good agreement with the literature. The effects of the nonlinear terms of the stiffness matrices on the computational results were investigated in detail. It was also demonstrated that the influence of geometric nonlinearities on the incremental steps of the finite element analysis for plane steel frames in the presence of fire is limited.

关键词: co-rotational     total Lagrangian     geometrical nonlinearity     fire     elasto-plastic    

properties of friction stir welded aluminum alloy joints based on axial force, traverse speed, and rotational

Biranchi PANDA,A. GARG,Zhang JIAN,Akbar HEIDARZADEH,Liang GAO

《机械工程前沿(英文)》 2016年 第11卷 第3期   页码 289-298 doi: 10.1007/s11465-016-0393-y

摘要:

Friction stir welding (FSW) process has gained attention in recent years because of its advantages over the conventional fusion welding process. These advantages include the absence of heat formation in the affected zone and the absence of large distortion, porosity, oxidation, and cracking. Experimental investigations are necessary to understand the physical behavior that causes the high tensile strength of welded joints of different metals and alloys. Existing literature indicates that tensile properties exhibit strong dependence on the rotational speed, traverse speed, and axial force of the tool that was used. Therefore, this study introduces the experimental procedure for measuring tensile properties, namely, ultimate tensile strength (UTS) and tensile elongation of the welded AA 7020 Al alloy. Experimental findings suggest that a welded part with high UTS can be achieved at a lower heat input compared with the high heat input condition. A numerical approach based on genetic programming is employed to produce the functional relationships between tensile properties and the three inputs (rotational speed, traverse speed, and axial force) of the FSW process. The formulated models were validated based on the experimental data, using the statistical metrics. The effect of the three inputs on the tensile properties was investigated using 2D and 3D analyses. A high UTS was achieved, including a rotational speed of 1050 r/min and traverse speed of 95 mm/min. The results also indicate that 8 kN axial force should be set prior to the FSW process.

关键词: tensile properties     ultimate tensile strength     tensile elongation     friction stir welding     tool rotational speed     genetic programming     welding speed    

Design and analysis of a class of redundant collaborative manipulators with 2-dimension large rotational

Xiaodong JIN, Yuefa FANG, Dan ZHANG, Xueling LUO

《机械工程前沿(英文)》 2020年 第15卷 第1期   页码 66-80 doi: 10.1007/s11465-019-0570-x

摘要: The parallel spindle heads with high rotational capability are demanded in the area of multi-axis machine tools and 3D printers. This paper focuses on designing a class of 2R1T (R: Rotation; T: Translation) parallel spindle heads and the corresponding collaborative 5-axis manipulators with 2-dimension (2D) large rotational angles. In order to construct 2D rotational degrees of freedom (DOF), a platform with 2-dimension revolute joints is proposed first. Based on the constraint screw theory, the feasible limbs that can be connected in the platform are synthesized. In order to provide constant rotational axis for the platform, a class of redundant limbs are designed. A class of redundant 2R1T parallel spindle heads is obtained by connecting the redundant limbs with the platform and the redundant characteristics are verified by the modified Grübler-Kutzbach criterion. The corresponding 5-axis collaborative manipulators are presented by constructing a 2-DOF series translational bottom moving platform. The inverse kinematics and the orientation workspace as well as the decoupling characteristics of this type of 2R1T parallel spindle heads are analyzed. The results show that these manipulators have large 2D rotational angles than the traditional A3/Z3 heads and can be potentially used in the application of multi-axis machine tools and the 3D printers.

关键词: parallel mechanism     redundant mechanism     large rotational angles     machine tools     2R1T spindle head     collaborative manipulator    

Soft curvature sensors for measuring the rotational angles of mechanical fingers

Haixiao LIU, Li LI, Zhikang OUYANG, Wei SUN

《机械工程前沿(英文)》 2020年 第15卷 第4期   页码 610-621 doi: 10.1007/s11465-020-0596-0

摘要: The design, fabrication, and testing of soft sensors that measure elastomer curvature and mechanical finger bending are described in this study. The base of the soft sensors is polydimethylsiloxane (PDMS), which is a translucent elastomer. The main body of the soft sensors consists of three layers of silicone rubber plate, and the sensing element is a microchannel filled with gallium-indium-tin (Ga-In-Sn) alloy, which is embedded in the elastomer. First, the working principle of soft sensors is investigated, and their structure is designed. Second, the relationship between curvature and resistance is determined. Third, several sensors with different specifications are built in accordance with the structural design. Experiments show that the sensors exhibit high accuracy when the curvature changes within a certain range. Lastly, the soft sensors are applied to the measurement of mechanical finger bending. Experiments show that soft curvature sensors can effectively reflect mechanical finger bending and can be used to measure the bending of mechanical fingers with high sensitivity within a certain working range.

关键词: soft sensor     Ga-In-Sn alloy     strain sensing     curvature sensing     mechanical finger bending    

一种新型转子式陀螺的分辨率为0.47″的转子微偏转角度检测方法 Article

Hai LI, Xiao-wei LIU, Rui WENG, Hai-feng ZHANG

《信息与电子工程前沿(英文)》 2017年 第18卷 第5期   页码 591-598 doi: 10.1631/FITEE.1500454

摘要: 差分电容检测被广泛应用于振动陀螺仪质量块的位移测量,然而由于结构、理论以及接口电路等因素的限制其在转子式陀螺所需的转子偏转角度检测方面还尚未取得较高分辨率。本文提出了一种差分电容检测结构,用以测量一种新型转子式陀螺转子的偏转角度。本文建立了结构电容与转子偏转角度之间关系的数学模型,分析了差分电容与结构参数之间的关系,并获得了初步优化的尺寸参数。设计了一款低噪声读出接口电路将差分电容的变化转换为电压信号。对陀螺仪的转台测试结果表明,该角度检测结构的最小可分辨的偏转角度小于0.47″(0.00013°),三次多项式补偿后检测结构的非线性可达0.33%,并可进一步提高。结果表明该检测结构和电路有助于实现该陀螺仪的高精度。

关键词: 微角度检测;差分电容结构;转子式陀螺    

Development of an analytical model to estimate the churning losses in high-speed axial piston pumps

《机械工程前沿(英文)》 2022年 第17卷 第2期 doi: 10.1007/s11465-021-0671-1

摘要: The axial piston pumps in aerospace applications are often characterized by high-speed rotation to achieve great power density. However, their internal rotating parts are fully immersed in the casing oil during operation, leading to considerable churning losses (more than 10% of total power losses) at high rotational speeds. The churning losses deserve much attention at the design stage of high-speed axial piston pumps, but accurate analytical models are not available to estimate the drag torque associated with the churning losses. In this paper, we derive the analytical expressions of the drag torque acting on the key rotating parts immersed in oil, including the cylinder block and the multiple pistons in a circular array. The calculated drag torque agrees well with the experimental data over a wide range of rotational speeds from 1500 to 12000 r/min. The presented analytical model provides practical guidelines for reducing the churning losses in high-speed axial piston pumps or motors.

关键词: axial piston pump     rotating parts     high rotational speed     churning losses     drag torque    

Scrutiny of non-linear differential equations Euler-Bernoulli beam with large rotational deviation by

M. R. AKBARI,M. NIMAFAR,D. D. GANJI,M. M. AKBARZADE

《机械工程前沿(英文)》 2014年 第9卷 第4期   页码 402-408 doi: 10.1007/s11465-014-0316-8

摘要:

The kinematic assumptions upon which the Euler-Bernoulli beam theory is founded allow it to be extended to more advanced analysis. Simple superposition allows for three-dimensional transverse loading. Using alternative constitutive equations can allow for viscoelastic or plastic beam deformation. Euler-Bernoulli beam theory can also be extended to the analysis of curved beams, beam buckling, composite beams and geometrically nonlinear beam deflection. In this study, solving the nonlinear differential equation governing the calculation of the large rotation deviation of the beam (or column) has been discussed. Previously to calculate the rotational deviation of the beam, the assumption is made that the angular deviation of the beam is small. By considering the small slope in the linearization of the governing differential equation, the solving is easy. The result of this simplification in some cases will lead to an excessive error. In this paper nonlinear differential equations governing on this system are solved analytically by Akbari-Ganji’s method (AGM). Moreover, in AGM by solving a set of algebraic equations, complicated nonlinear equations can easily be solved and without any mathematical operations such as integration solving. The solution of the problem can be obtained very simply and easily. Furthermore, to enhance the accuracy of the results, the Taylor expansion is not needed in most cases via AGM manner. Also, comparisons are made between AGM and numerical method (Runge-Kutta 4th). The results reveal that this method is very effective and simple, and can be applied for other nonlinear problems.

关键词: AGM     critical load of columns     large deformations of beam     nonlinear differential equation    

Vibratory behaviors of Jeffcott system on cylindrical roller bearings

Hao WU, Jianwen WANG, Qi AN

《机械工程前沿(英文)》 2009年 第4卷 第3期   页码 305-309 doi: 10.1007/s11465-009-0036-7

摘要: A Jeffcott rotor system of cylindrical roller bearings is studied in detail. Its critical speed is calculated by a new calculation method with roller bearing stiffness and damping. The influences of bearing parameters, such as the roller length, rotor mass, distance between the bearings and the kinematics viscosity of oil on the system critical speed are numerically studied, and the influences of an oil film and damping on the critical speed are also studied. Regular curves of the relationship between the geometric parameters and the system critical speed are obtained. The results show that with increasing roller length and radial load, the critical speed increases; and with increasing rotor mass and the distance between the bearings and the kinematics viscosity, the critical speed decreases. This means that an oil film will decrease the critical rotational speed of the rotor system.

关键词: roller bearing     bearing-rotor system     design value     critical rotational speed    

CO, N, and CO/N mixed gas injection for enhanced shale gas recovery and CO geological storage

《能源前沿(英文)》 2023年 第17卷 第3期   页码 428-445 doi: 10.1007/s11708-023-0865-9

摘要: In this work, using fractured shale cores, isothermal adsorption experiments and core flooding tests were conducted to investigate the performance of injecting different gases to enhance shale gas recovery and CO2 geological storage efficiency under real reservoir conditions. The adsorption process of shale to different gases was in agreement with the extended-Langmuir model, and the adsorption capacity of CO2 was the largest, followed by CH4, and that of N2 was the smallest of the three pure gases. In addition, when the CO2 concentration in the mixed gas exceeded 50%, the adsorption capacity of the mixed gas was greater than that of CH4, and had a strong competitive adsorption effect. For the core flooding tests, pure gas injection showed that the breakthrough time of CO2 was longer than that of N2, and the CH4 recovery factor at the breakthrough time (RCH4) was also higher than that of N2. The RCH4 of CO2 gas injection was approximately 44.09%, while the RCH4 of N2 was only 31.63%. For CO2/N2 mixed gas injection, with the increase of CO2 concentration, the RCH4 increased, and the RCH4 for mixed gas CO2/N2 = 8:2 was close to that of pure CO2, about 40.24%. Moreover, the breakthrough time of N2 in mixed gas was not much different from that when pure N2 was injected, while the breakthrough time of CO2 was prolonged, which indicated that with the increase of N2 concentration in the mixed gas, the breakthrough time of CO2 could be extended. Furthermore, an abnormal surge of N2 concentration in the produced gas was observed after N2 breakthrough. In regards to CO2 storage efficiency (Sstorage-CO2), as the CO2 concentration increased, Sstorage-CO2 also increased. The Sstorage-CO2 of the pure CO2 gas injection was about 35.96%, while for mixed gas CO2/N2 = 8:2, Sstorage-CO2 was about 32.28%.

关键词: shale gas     gas injection     competitive adsorption     enhanced shale gas recovery     CO2 geological storage    

CO2 methanation and co-methanation of CO and CO2 over Mn-promoted Ni/Al2

Kechao Zhao,Zhenhua Li,Li Bian

《化学科学与工程前沿(英文)》 2016年 第10卷 第2期   页码 273-280 doi: 10.1007/s11705-016-1563-5

摘要: A series of Mn-promoted 15 wt-% Ni/Al O catalysts were prepared by an incipient wetness impregnation method. The effect of the Mn content on the activity of the Ni/Al O catalysts for CO methanation and the co-methanation of CO and CO in a fixed-bed reactor was investigated. The catalysts were characterized by N physisorption, hydrogen temperature-programmed reduction and desorption, carbon dioxide temperature-programmed desorption, X-ray diffraction and high-resolution transmission electron microscopy. The presence of Mn increased the number of CO adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support. The Mn-promoted 15 wt-% Ni/Al O catalysts had improved CO methanation activity especially at low temperatures (250 to 400 °C). The Mn content was varied from 0.86% to 2.54% and the best CO conversion was achieved with the 1.71Mn-Ni/Al O catalyst. The co-methanation tests on the 1.71Mn-Ni/Al O catalyst indicated that adding Mn markedly enhanced the CO methanation activity especially at low temperatures but it had little influence on the CO methanation performance. CO methanation was more sensitive to the reaction temperature and the space velocity than the CO methanation in the co-methanation process.

关键词: Mn promotion     nickel catalysts     CO2 methanation     co-methanation of CO and CO2    

An investigation of the CHOH and CO selectivity of CO hydrogenation over Cu–Ce–Zr catalysts

《化学科学与工程前沿(英文)》 2022年 第16卷 第6期   页码 950-962 doi: 10.1007/s11705-022-2162-2

摘要: A series of Cu–Ce–Zr catalysts with different Ce contents are applied to the hydrogenation of CO2 to CO/CH3OH products. The Cu–Ce–Zr catalyst with 2 wt% Ce loading shows higher CO selectivity (SCO = 0.0%–87.8%) from 200–300 °C, while the Cu–Ce–Zr catalyst with 8 wt% Ce loading presents higher CO2 conversion ( XCO2 = 5.4%–15.6%) and CH3OH selectivity ( SCH3OH = 97.8%–40.6%). The number of hydroxyl groups and solid solution nature play a significant role in changing the reaction pathway. The solid solution enhances the CO2 adsorption ability. At the CO2 adsorption step, a larger number of hydroxyl groups over the Cu–Ce–Zr catalyst with 8 wt% Ce loading leads to the production of H-containing adsorption species. At the CO2 hydrogenation step, a larger number of hydroxyl groups assists in encouraging the further hydrogenation of intermediate species to CH3OH and improving the hydrogenation rate. Hence, the Cu–Ce–Zr catalyst with 8 wt% Ce loading favors CH3OH selectivity and CO2 activation, while CO is preferred on the Cu–Ce–Zr catalyst with 2 wt% Ce loading, a smaller number of hydroxyl groups and a solid solution nature. Additionally, high-pressure in situ diffuse reflectance infrared Fourier transform spectroscopy shows that CO is produced from formate decomposition and that both monodentate formate and bidentate formate are active intermediate species of CO2 hydrogenation to CH3OH.

关键词: CO2 hydrogenation     Cu–Ce–Zr     hydroxyls     CO/CH3OH selectivity    

Conversion of CO into CO by high active and stable PdNi nanoparticles supported on a metal-organic framework

《化学科学与工程前沿(英文)》 2022年 第16卷 第7期   页码 1139-1148 doi: 10.1007/s11705-021-2111-5

摘要: The solubility of Pd(NO3)2 in water is moderate whereas it is completely soluble in diluted HNO3 solution. Pd/MIL-101(Cr) and Pd/MIL-101-NH2(Cr) were synthesized by aqueous solution of Pd(NO3)2 and Pd(NO3)2 solution in dilute HNO3 and used for CO oxidation reaction. The catalysts synthesized with Pd(NO3)2 solution in dilute HNO3 showed lower activity. The aqueous solution of Pd(NO3)2 was used for synthesis of mono-metal Ni, Pd and bimetallic PdNi nanoparticles with various molar ratios supported on MOF. Pd70Ni30/MIL-101(Cr) catalyst showed higher activity than monometallic counterparts and Pd+ Ni physical mixture due to the strong synergistic effect of PdNi nanoparticles, high distribution of PdNi nanoparticles, and lower dissociation and desorption barriers. Comparison of the catalysts synthesized by MIL-101(Cr) and MIL-101-NH2(Cr) as the supports of metals showed that Pd/MIL-101-NH2(Cr) outperforms Pd/MIL-101-(Cr) because of the higher electron density of Pd resulting from the electron donor ability of the NH2 functional group. However, the same activities were observed for Pd70Ni30/MIL-101(Cr) and Pd70Ni30/MIL-101-NH2(Cr), which is due to a less uniform distribution of Pd nanoparticles in Pd70Ni30/MIL-101-NH2(Cr) originated from amorphization of MIL-101-NH2(Cr) structure during the reduction process. In contrast, Pd70Ni30/MIL-101(Cr) revealed the stable structure and activity during reduction and CO oxidation for a long time.

关键词: CO oxidation     heterogeneous catalysis     metal-organic framework     NH2 functional group     PdNi    

Reduction potential of the energy penalty for CO capture in CCS

《能源前沿(英文)》 2023年 第17卷 第3期   页码 390-399 doi: 10.1007/s11708-023-0864-x

摘要: CO2 capture and storage (CCS) has been acknowledged as an essential part of a portfolio of technologies that are required to achieve cost-effective long-term CO2 mitigation. However, the development progress of CCS technologies is far behind the targets set by roadmaps, and engineering practices do not lead to commercial deployment. One of the crucial reasons for this delay lies in the unaffordable penalty caused by CO2 capture, even though the technology has been commonly recognized as achievable. From the aspects of separation and capture technology innovation, the potential and promising direction for solving this problem were analyzed, and correspondingly, the possible path for deployment of CCS in China was discussed. Under the carbon neutral target recently proposed by the Chinese government, the role of CCS and the key milestones for deployment were indicated.

关键词: CO2 capture and storage (CCS)     CO2 separation     energy penalty    

A coal-fired power plant integrated with biomass co-firing and CO capture for zero carbon emission

《能源前沿(英文)》 2022年 第16卷 第2期   页码 307-320 doi: 10.1007/s11708-021-0790-8

摘要: A promising scheme for coal-fired power plants in which biomass co-firing and carbon dioxide capture technologies are adopted and the low-temperature waste heat from the CO2 capture process is recycled to heat the condensed water to achieve zero carbon emission is proposed in this paper. Based on a 660 MW supercritical coal-fired power plant, the thermal performance, emission performance, and economic performance of the proposed scheme are evaluated. In addition, a sensitivity analysis is conducted to show the effects of several key parameters on the performance of the proposed system. The results show that when the biomass mass mixing ratio is 15.40% and the CO2 capture rate is 90%, the CO2 emission of the coal-fired power plant can reach zero, indicating that the technical route proposed in this paper can indeed achieve zero carbon emission in coal-fired power plants. The net thermal efficiency decreases by 10.31%, due to the huge energy consumption of the CO2 capture unit. Besides, the cost of electricity (COE) and the cost of CO2 avoided (COA) of the proposed system are 80.37 $/MWh and 41.63 $/tCO2, respectively. The sensitivity analysis demonstrates that with the energy consumption of the reboiler decreasing from 3.22 GJ/tCO2 to 2.40 GJ/ tCO2, the efficiency penalty is reduced to 8.67%. This paper may provide reference for promoting the early realization of carbon neutrality in the power generation industry.

关键词: coal-fired power plant     biomass co-firing     CO2 capture     zero carbon emission     performance evaluation    

标题 作者 时间 类型 操作

Bending and rotational behaviour of semi-continuous composite beams

WANG Jingfeng, LI Guoqiang

期刊论文

Implementation of total Lagrangian formulation for the elasto-plastic analysis of plane steel frames exposed to fire

Bing XIA, Yuching WU, Zhanfei HUANG

期刊论文

properties of friction stir welded aluminum alloy joints based on axial force, traverse speed, and rotational

Biranchi PANDA,A. GARG,Zhang JIAN,Akbar HEIDARZADEH,Liang GAO

期刊论文

Design and analysis of a class of redundant collaborative manipulators with 2-dimension large rotational

Xiaodong JIN, Yuefa FANG, Dan ZHANG, Xueling LUO

期刊论文

Soft curvature sensors for measuring the rotational angles of mechanical fingers

Haixiao LIU, Li LI, Zhikang OUYANG, Wei SUN

期刊论文

一种新型转子式陀螺的分辨率为0.47″的转子微偏转角度检测方法

Hai LI, Xiao-wei LIU, Rui WENG, Hai-feng ZHANG

期刊论文

Development of an analytical model to estimate the churning losses in high-speed axial piston pumps

期刊论文

Scrutiny of non-linear differential equations Euler-Bernoulli beam with large rotational deviation by

M. R. AKBARI,M. NIMAFAR,D. D. GANJI,M. M. AKBARZADE

期刊论文

Vibratory behaviors of Jeffcott system on cylindrical roller bearings

Hao WU, Jianwen WANG, Qi AN

期刊论文

CO, N, and CO/N mixed gas injection for enhanced shale gas recovery and CO geological storage

期刊论文

CO2 methanation and co-methanation of CO and CO2 over Mn-promoted Ni/Al2

Kechao Zhao,Zhenhua Li,Li Bian

期刊论文

An investigation of the CHOH and CO selectivity of CO hydrogenation over Cu–Ce–Zr catalysts

期刊论文

Conversion of CO into CO by high active and stable PdNi nanoparticles supported on a metal-organic framework

期刊论文

Reduction potential of the energy penalty for CO capture in CCS

期刊论文

A coal-fired power plant integrated with biomass co-firing and CO capture for zero carbon emission

期刊论文