Study on modified differential transform method for free vibration analysis of uniform Euler-Bernoulli beam

Zhifeng Liu,Yunyao Yin,Feng Wang,Yongsheng Zhao,Ligang Cai 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

A simulation method called modified differential transform is studied to solve the free vibration problems of uniform Euler-Bernoulli beam. First of all, the modified differential transform method is derived. Secondly, the modified differential transformation is applied to uniform Euler-Bernoulli beam freefree vibration. And then a set of differential equations are established. Through algebraic operations on these equations, we can get any natural frequency and normalized mode shape. Thirdly, the FEM is applied to obtain the numerical solutions. Finally, mode experimental method (MEM) is conducted to obtain experimental data for analysis by signal processing with LMS Test.lab Vibration testing and analysis system. Experimental data and simulation results are illustrated to be in comparison with the analytical solutions. The results show that the modified differential transform method can achieve good results in predicting the solution of such problems.

Design Method of Active Disassembly Structure Triggered by Temperature-Pressure Coupling

Zhifeng Liu,Yifei Zhan,Huanbo Cheng,Xinyu Li,Shaobo Pan 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

Active disassembly products often use active disassembly structures triggered by single temperature or pressure field as reversible joints. These structures can be triggered automatically in extreme or accidental circumstances, thus causing the low reliability of products. For improving the reliability of active disassembly products, working mechanisms of active disassembly structure triggered by temperature-pressure coupling is presented in this article. Through analyzing some typical active disassembly structures, this article presents the design criteria and methods of active disassembly structure triggered by temperature-pressure coupling. The feasibility of these design methods is proved by a case analysis. The results of research shows that the reliability of active disassembly structures triggered by temperature-pressure coupling is improved greatly, which can lay the foundation for the industrial applications of active disassembly methods.

Study on modified differential transform method for free vibration analysis of uniform Euler-Bernoulli beam

Liu, Zhifeng,Yin, Yunyao,Wang, Feng,Zhao, Yongsheng,Cai, Ligang Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

A simulation method called modified differential transform is studied to solve the free vibration problems of uniform Euler-Bernoulli beam. First of all, the modified differential transform method is derived. Secondly, the modified differential transformation is applied to uniform Euler-Bernoulli beam free-free vibration. And then a set of differential equations are established. Through algebraic operations on these equations, we can get any natural frequency and normalized mode shape. Thirdly, the FEM is applied to obtain the numerical solutions. Finally, mode experimental method (MEM) is conducted to obtain experimental data for analysis by signal processing with LMS Test.lab Vibration testing and analysis system. Experimental data and simulation results are illustrated to be in comparison with the analytical solutions. The results show that the modified differential transform method can achieve good results in predicting the solution of such problems.

Experimental studies on torsional stiffness of cycloid gear based on machining parameters of tooth surfaces

Zhifeng Liu,Tao Zhang,Yida Wang,Congbin Yang,Yongsheng Zhao 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.6

Estimating the torsional stiffness has always been the primary issue in analyzing the dynamic characteristics of cycloid gears. The traditional method of obtaining torsional rigidity involves calculating the ratio of the input torque and rotation angle, treating the deformation of cycloid gear as a black box. In order to thoroughly understand the rotation angle caused by the local contact deformation of each cycloid pin gear, a Majumdar–Bhushan contact model and the finite element method are combined to express the normal contact stiffness. By multiplying the normal contact stiffness of each pin gear and the arm of normal contact force, the torsional stiffness of the cycloidal pin wheel system can be calculated. Experiments are conducted to establish the relationship between the torsional stiffness and roughness parameters of the machined tooth surface. The effect of input torque on the torsional stiffness has also been analyzed. This study formulates a relationship between the torsional stiffness and surface characteristics of cycloid gears, which can help improve their design and manufacture in the future.

Protective role of endothelial calpain knockout in lipopolysaccharide-induced acute kidney injury via attenuation of the p38-iNOS pathway and NO/ROS production

Zhifeng Liu,Jingjing Ji,Dong Zheng,Lei Su,Tianqing Peng,Jing Tang 생화학분자생물학회 2020 Experimental and molecular medicine Vol.52 No.-

To explore the role of calpain and its signaling pathway in lipopolysaccharide (LPS)-induced acute kidney injury (AKI), animal models of endotoxemia were established by administration of LPS to mice with endothelial-specific Capn4 knockout (TEK/Capn4−/−), mice with calpastatin (an endogenous calpain inhibitor) overexpression (TgCAST) and mice with myeloid-specific Capn4 knockout (LYZ/Capn4−/−). Mouse pulmonary microvascular endothelial cells (PMECs) were used as a model of the microvascular endothelium and were stimulated with LPS. Renal function, renal inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) expression, cellular apoptosis, plasma and renal levels of NO and reactive oxygen species (ROS), and phosphorylation of mitogenactivated protein kinase (MAPK) family members (p38, ERK1/2, and JNK1/2) were examined. Moreover, a calpain inhibitor, calpastatin overexpression adenoviruses and MAPK inhibitors were used. Significant renal dysfunction was induced by LPS stimulation, and recovery was observed in TEK/Capn4−/− and Tg-CAST mice but not in LYZ/ Capn4−/− mice. Endothelial Capn4 knockout also abrogated the LPS-induced increases in renal iNOS expression, caspase-3 activity and apoptosis and plasma and renal NO and ROS levels but did not obviously affect renal eNOS expression. Moreover, LPS increased both calpain and caspase-3 activity, and only the expression of iNOS in PMECs was accompanied by increased phosphorylation of p38 and JNK. Inhibiting calpain activity or p38 phosphorylation alleviated the increased iNOS expression, NO/ROS production, and cellular apoptosis induced by LPS. These results suggest that endothelial calpain plays a protective role in LPS-induced AKI by inhibiting p38 phosphorylation, thus attenuating iNOS expression and further decreasing NO and ROS overproduction-induced endothelial apoptosis.

Trajectory Planning with Minimum Synthesis Error for Industrial Robots Using Screw Theory

Zhifeng Liu,Jingjing Xu,Qiang Cheng,Yongsheng Zhao,Yanhu Pei,Congbin Yang 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.2

This work aims to propose a trajectory planning technique to minimize the end-effector synthesis error for industrial robots, while obtaining a stable movement. With ER3A-C60 robot as a research subject, the kinematic and dynamic models are established by using screw theory and Kane equations, and based on that, the end-effector synthesis error is modeled by considering the effects of interpolation algorithm and flexibilities of all joints. The septic polynomial is used to interpolate the via points in each joint space to obtain a stable movement. Finally, the PSO algorithm with suitable parameters is applied to find the minimum synthesis error under kinematic and dynamic constraints. The results show that the optimal synthesis error decreases by 88.94% compared with the initial one, the angular parameters are all far less than the limitations of joints and the optimal movement has a high stability, and this optimal trajectory has better overall performance than that based on the previous technique (with the minimum total motion time). The main contribution is that the proposed trajectory planning technique can significantly improve the tracking precision of the end effector while controlling the motion time within a given span under the requirements of continuous path control.

Timoshenko beam-based stability and natural frequency analysis for heavy load mechanical spindles

Zhifeng Liu,Shiming Ma,Ligang Cai,Tieneng Guo,Yongsheng Zhao 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.11

The heavy load mechanical spindle is an important functional component in a 5-axis computer numerical control (CNC) machine tool,which is used to process large and complex free-form surfaces. It is necessary to obtain the natural frequency and analyze the spindle stability for improving the machining precision. In this paper, Timoshenko beam theory is introduced to model the mechanical spindle shaft, where the centrifugal force and gyroscopic effects are considered. Stability of the heavy load mechanical spindle shaft is analyzed,and the buckling load of the spindle shaft is obtained under different rotational speeds. The natural frequency of spindle is investigated in a freedom and restraint state, respectively. Comparing the proposed method with the simplified hollow cylinder and shaft prototype in the freedom state, the results show that they are highly correlated with experimental results. For the restraint state, the axial load, rotational speed, gyroscopic effect, and centrifugal force are discussed, and all of these parameters affect the natural frequency. The proposed modeling approach can be used for spindle design and optimization in a given machining process and can be easily extended to other spindle design.

CFRP Reclamation and Remanufacturing Based on a Closed-loop Recycling Process for Carbon Fibers Using Supercritical N-butanol

Weihao Liu,Haihong Huang,Huanbo Cheng,Zhifeng Liu 한국섬유공학회 2020 Fibers and polymers Vol.21 No.3

This study presents a closed-loop recycling process for carbon fibers using supercritical n-butanol. In thereclamation process, to achieve the highest composite recovery efficiency, the degradation of the carbon fiber-reinforcedepoxy resin composites was conducted at various experimental feedstock ratios (ratio of composite waste to n-butanol), thenthe reclaimed carbon fiber (RCF) was characterized using various methods to develop an understanding of the changes in theproperties and morphologies. In the remanufacturing process, in order to evaluate the reusability of the RCFs and thefeasibility of the closed-loop recycling process for carbon fibers, the RCFs were mixed with new epoxy resin andpolypropylene to remanufacture the composites, and then the mechanical properties of remanufacture composites weretested. The results show that, under an optimized process, the maximum recovery efficiency (feedstock ratio) of thecomposite was 0.1 g/ml. The impact of reclamation process on RCF lies in the degradation of tensile properties and theremoval of sizing agent, which leads the change of the interfacial bonding strength between RCF and new resin, andeventually results in an impact on the performance of remanufacture composites. Compared with the virgin carbon fiberreinforcedcomposites, the improvement in the RCF-reinforced polypropylene properties and insubstantial variations in thetensile properties of the RCF validate the potential of the closed-loop recycling process for carbon fibers.

TiO2 Nanotubes/Nanoparticles Composite Film with Higher Light Harvesting and Electron Transfer for Dye-Sensitized Solar Cells

Chengcheng Liu,Zhifeng Liu,Lei E,Yabin Li,Jianhua Han,Yun Wang,Zhichao Liu,Jing Ya,Xuhuang Chen 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.5

TiO2 nanotubes with an inner diameter of 4-6 nm were synthesized by hydrothermal treatment method. TiO2nanotubes/nanoparticles composite films were fabricated as a dye-sensitized solar cells work electrode using TiO2 nanotubes and TiO2 nanoparticles as precursor. The structure of composite films has a remarkable influence on the final performance of the cell due to high surface area, fast electron transfer, enhanced light-scattering and light-harvesting, simultaneously. I-V characteristic measurement indicates an enhanced efficiency by 27%as compared to TiO2 nanotubes film.

Decentralized Constrained Tracking Control for Interconnected Nonlinear Systems with Interconnection and Input Delays

Zhifeng Gao,Donghao Liu,Moshu Qian 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.4

In this paper, a novel decentralized control approach is studied for interconnected nonlinear systems with unknown interconnection delays, uncertain input delays, and asymmetric full state dynamic constraints. The broad learning system (BLS) is introduced to approximate the unstructured uncertainties and a nonlinear observer is designed to identify the unmeasurable states. To guarantee the normal operation of the considered state constraints systems without any feasibility conditions, a unified barrier function (UBF) is developed. By utilized the commandfiltered backstepping control technique, a decentralized constrained tracking control scheme is proposed. It is proved that all signals of the closed-loop stability and tracking performance could be guaranteed by the proposed control method and asymmetric full states dynamic constraints are not violated. Numerical simulation results are given to demonstrate the effectiveness of the proposed control method.