scholarly journals Analysis of Contact Mechanical Characteristics of Flexible Parts in Harmonic Gear Reducer

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Fanjie Li ◽  
Xiaopeng Li ◽  
Yajing Guo ◽  
Dongyang Shang
Keyword(s):  
Mechanical Characteristics ◽  
Angular Displacement ◽  
Excitation Frequency ◽  
Element Model ◽  
Industrial Robots ◽  
Axial Distance ◽  
Axial Vibration ◽  
Cylinder Length ◽  
Flexible Parts ◽  
Contact Mechanical

Harmonic gear reducer is widely used in industrial robots, aerospace, optics, and other high-end fields. The failure of harmonic gear reducer is mainly caused by the damage of flexible bearing and flexspline of thin-walled vulnerable components. To study the contact mechanical characteristics of flexible components such as flexible bearing and flexspline in harmonic gear reducer, the contact mechanical model of flexible bearing, vibration differential equation of flexspline, and finite element model of each component in harmonic gear reducer were established. Based on the established model of harmonic gear reducer, the influence of the length of flexspline cylinder and the thickness of cylinder bottom on the stress of flexspline is discussed, respectively, and the motion characteristics of flexible bearing are studied. At the same time, the spatial distribution of the displacement of the flexspline and the axial vibration response of the flexspline are studied. The correctness of the model established in this paper is verified by experiments. The results show that the increase of cylinder length can improve the stress of flexspline in harmonic gear reducer; the wall thickness of cylinder bottom mainly affects the stress at the bottom of flexspline but has little effect on the stress of gear ring and smooth cylinder. Along the axis direction of the flexspline, the radial displacement, circumferential displacement, and angular displacement increase linearly with the increase of the axial distance between the cylinder and the bottom. When the excitation frequency is high, the vibration mode of flexspline shell is mainly axial vibration. The research results will provide a theoretical reference for the optimal design of harmonic gear reducer and improving the service life of flexible parts.

scholarly journals Mechanical Characteristics of Ballast Bed under Dynamic Stabilization Operation Based on Discrete Element and Experimental Approaches

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Lihua Wang ◽  
Zemin Zhao ◽  
Jiongli Wang ◽  
Xianzeng Li ◽  
Yayu Huang ◽  
...  
Keyword(s):  
Mechanical Characteristics ◽  
Simulation Analysis ◽  
Excitation Frequency ◽  
Three Dimensional ◽  
Element Model ◽  
Discrete Element ◽  
Stable Operation ◽  
Simulation Test ◽  
Lateral Resistance ◽  
Experimental Approaches

To study the mechanical characteristics of ballasted bed under dynamic stability, a three-dimensional discrete element model of ballasted bed with 1000 mm × 700 mm × 550 mm is established based on the discrete element method. Meanwhile, a simulation test bench with the same size is built for simulation analysis and experimental research. The variation law and trend of settlement, lateral resistance, and compactness of ballasted bed under different excitation frequencies are analyzed comprehensively. The results show that when the excitation frequency is constant, the lateral resistance of sleeper, the settlement of sleeper, and the compactness of track bed under sleeper increase first and then tend to be stable. With the increase in horizontal excitation frequency, lateral resistance of ballast bed, sleeper settlement, and compactness first increase and then decrease after stable operation. The values of these parameters are maximized when the excitation frequency is 36 Hz which is the relative optimal horizontal excitation frequency of this model.

scholarly journals Research on the longitudinal mechanical behaviours of subway turnouts of large slope under train braking force

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110283
Author(s):  
Zhiping Zeng ◽  
Ji Hu ◽  
Chunyu Tian ◽  
Ping Li ◽  
Xiangdong Huang ◽  
...  
Keyword(s):  
Finite Element ◽  
Temperature Change ◽  
Mechanical Characteristics ◽  
Element Model ◽  
Longitudinal Displacement ◽  
Longitudinal Deformation ◽  
Longitudinal Stiffness ◽  
Mechanical Behaviours ◽  
Longitudinal Resistance ◽  
Safety And Stability

To study subway turnouts’ adaptability to steep gradients, a finite element model of a metro No. 9 simple turnout was established. The main works include: (1) The train’s most unfavourable loading condition was modelled. (2) The turnout’s longitudinal displacement and stress were analysed with different gradients under the train braking load, temperature change load and a combination of the two, to determine the structure’s safety and stability under the most unfavourable working conditions. (3) The turnout structure’s cumulative longitudinal deformation under reciprocating load was studied. Both a fastener longitudinal resistance-displacement experiment under reciprocating load and a numerical simulation of No. 9 turnout modelled by the finite element modelling software, ANSYS, were carried out to study the gradient’s influence on the turnout’s longitudinal mechanical characteristics. (1) The turnout’s longitudinal displacement and stress increase linearly with an increase in gradient and temperature change, both of which are unfavourable to the turnout structure. As the gradient increases from 0‰ to 30‰, the longitudinal stress and displacement increase by more than 10%. (2) The turnout’s rail strength and displacement on a 30‰ slope under the most unfavourable load conditions are within the specification limitations. (3) Under reciprocating load, the fastener longitudinal stiffness decreases and the maximum and residual longitudinal displacement of the switch rail increase; an increased gradient intensifies these effects on the turnout.

Modal Analysis of Axial Vibration of Long Pipeline Delivering Coal Slime in Power Plant

2015 ◽  
Vol 740 ◽  
pp. 112-115
Author(s):  
Qing Wei Shi ◽  
Ya Yun Liu ◽  
Xing Lu Liu ◽  
Xue Di Hao
Keyword(s):  
Finite Element ◽  
Power Plant ◽  
Modal Analysis ◽  
Element Model ◽  
Vibration Characteristics ◽  
Axial Vibration ◽  
Coal Slime ◽  
Pipeline Vibration ◽  
The Finite Element Model ◽  
Intense Vibration

Aiming at the problem of intense vibration of the long pipeline delivering coal slime in the power plant, the finite element model of pipeline is established and modal analysis is carried out by ANSYS. The natural frequency and vibration characteristics of axial vibration are obtained. The vibration characteristics are studied and different pipe segments that produce bigger vibration very easily in operation are determined. Theoretical guidance about pipeline vibration under the external load for further analysis is provided.

scholarly journals Calculation of Reasonable Tension Value for Longitudinal Connecting Reinforcement of CRTSII Slab Ballastless Track

2018 ◽  
Vol 8 (11) ◽  
pp. 2139 ◽  
Author(s):  
Long Chen ◽  
Jinjie Chen ◽  
Jianxi Wang
Keyword(s):  
Prestressed Concrete ◽  
Crack Width ◽  
Mechanical Characteristics ◽  
Tensile Force ◽  
Three Dimensional ◽  
Element Model ◽  
Railway Track ◽  
Tension Force ◽  
Original Design ◽  
Ballastless Track

There is confusion in the original design concept for the tensioning of longitudinally connected reinforcement of the CRTSII (China Railway Track System) slab ballastless track. In order to clarify the effect of tension value of longitudinal reinforcement on the mechanical characteristics of the ballastless track, a three-dimensional finite element model, considering the nonlinear interaction between the track slab and cement-emulsified asphalt (CA) mortar of the CRTSII slab ballastless track, was established. The mechanical characteristics of the track structure under longitudinal tension load and temperature gradient load of the longitudinal joint were calculated. A method of applying prestress to post-pouring concrete was proposed according to the concept of prestress loss of pretensioning prestressed concrete, a reasonable tensile force value was proposed after the crack width, and the reinforcement stress of the ballastless track in the operation stage was checked and calculated according to the concrete design principle. When the tension force is greater than 300 kN, it is harmful to the bonding between the slab and mortar layer, which is prone to interlayer damage. In order to add prestress to concrete with wide joints to ensure the longitudinal stability of the ballastless track, and that the reinforcement stress and crack width meet design requirements, it is suggested that the tension force value should be 230 kN. Further, the temperature difference between reinforcement and concrete should be 30 °C before the initial curdle of wide joint concrete.

Optimization of pipeline system with multi-hoop supports for avoiding vibration, based on particle swarm algorithm

2020 ◽  
pp. 095440622094711 ◽  
Author(s):  
Xudong Liu ◽  
Wei Sun ◽  
Ye Gao ◽  
Hui Ma
Keyword(s):  
Excitation Frequency ◽  
Particle Swarm ◽  
Element Model ◽  
Optimization Method ◽  
Operational Reliability ◽  
Particle Swarm Algorithm ◽  
Pipeline System ◽  
Pipe System ◽  
Swarm Algorithm ◽  
Single Pipe

In the dynamics design of aero-engine pipeline systems, it is necessary to avoid the excitation frequency of the engine (mainly including the rotational frequencies of high pressure and low pressure rotor systems) to improve the operational reliability of the pipeline system. In this study, a single-pipe system with multi-hoop supports was chosen as the research object, and a method based on the particle swarm algorithm was developed to optimize the layout of the hoops for effectively avoiding vibration of the pipeline system. A finite element model (FEM) of the pipeline system was created and the group of spring elements with non-uniform distribution of stiffness values was used to simulate the hoop support for improving the analysis accuracy of the model in the modeling process. Taking the hoop position as design variable, an optimization model of the pipe hoop layout was established, which aims at avoiding one or two excitation frequencies at the same time. Furthermore, the calculation procedure of optimizing pipe hoop layout using the particle swarm algorithm was given. Finally, a case study was carried out, the rationality of the created FEM was validated by experiments, and the optimal layout of hoops was obtained using the proposed optimization method.

Simulation and Test Study on Dynamic Characteristic of Air Spring with Auxiliary Chamber

2013 ◽  
Vol 341-342 ◽  
pp. 391-394 ◽  
Author(s):  
Li Qing Sun ◽  
Zhong Xxing Li ◽  
Xu Feng Shen ◽  
Jia Yi Zhu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Dynamic Characteristic ◽  
Dynamic Characteristics ◽  
Excitation Frequency ◽  
Initial Pressure ◽  
Element Model ◽  
Air Spring ◽  
Chamber Volume ◽  
Lower Excitation

In order to improve dynamic characteristics of air spring with auxiliary chamber, finite element model of air spring R1A390-295 with auxiliary chamber connected with pipe is established,and through analysis to the dynamic characteristics of the model, influence discipline of sitffness characteristics to air spring with different pipe, different auxiliary chamber or different initial pressure are analysed under different excitation. The result show that:minor dynamic sitffness is obtained by using larger pipe or under lower excitation frequency,and as volume of auxiliary chamber increases, the spring dynamic sitffness will decrease accordingly and its amplitude tends to gentle,and influence for decreasing the spring dynamic sitffness is not obvious by continuing to increase the auxiliary chamber volume; the spring dynamic sitffness will increases as initial pressure increases. The validity of Finite element model is verified through dynamic characteristic test .

scholarly journals A new joint friction model for parameter identification and sensor-less hand guiding in industrial robots

2020 ◽  
Vol 47 (6) ◽  
pp. 847-857
Author(s):  
Guanghui Liu ◽  
Qiang Li ◽  
Lijin Fang ◽  
Bing Han ◽  
Hualiang Zhang
Keyword(s):  
Industrial Robot ◽  
Angular Displacement ◽  
Weighted Least Squares ◽  
Friction Model ◽  
Industrial Robots ◽  
Model Parameters ◽  
Dynamic Parameters ◽  
Content Type ◽  
Joint Friction ◽  
Six Dof

Purpose The purpose of this paper is to propose a new joint friction model, which can accurately model the real friction, especially in cases with sudden changes in the motion direction. The identification and sensor-less control algorithm are investigated to verify the validity of this model. Design/methodology/approach The proposed friction model is nonlinear and it considers the angular displacement and angular velocity of the joint as a secondary compensation for identification. In the present study, the authors design a pipeline – including a manually designed excitation trajectory, a weighted least squares algorithm for identifying the dynamic parameters and a hand guiding controller for the arm’s direct teaching. Findings Compared with the conventional joint friction model, the proposed method can effectively predict friction factors during the dynamic motion of the arm. Then friction parameters are quantitatively obtained and compared with the proposed friction model and the conventional friction model indirectly. It is found that the average root mean square error of predicted six joints in the proposed method decreases by more than 54%. The arm’s force control with the full torque using the estimated dynamic parameters is qualitatively studied. It is concluded that a light-weight industrial robot can be dragged smoothly by the hand guiding. Practical implications In the present study, a systematic pipeline is proposed for identifying and controlling an industrial arm. The whole procedure has been verified in a commercial six DOF industrial arm. Based on the conducted experiment, it is found that the proposed approach is more accurate in comparison with conventional methods. A hand-guiding demo also illustrates that the proposed approach can provide the industrial arm with the full torque compensation. This essential functionality is widely required in many industrial arms such as kinaesthetic teaching. Originality/value First, a new friction model is proposed. Based on this model, identifying the dynamic parameter is carried out to obtain a set of model parameters of an industrial arm. Finally, a smooth hand guiding control is demonstrated based on the proposed dynamic model.

Modeling Method of Assembled Structure Coupling the Characteristics of the Joints

2012 ◽  
Vol 468-471 ◽  
pp. 2141-2148
Author(s):  
Tie Neng Guo ◽  
Xue Li Yu ◽  
Fu Ping Li ◽  
Li Gang Cai ◽  
Ya Hui Cui
Keyword(s):  
Mechanical Properties ◽  
Mechanical Characteristics ◽  
Element Model ◽  
Experimental Investigations ◽  
Beam Elements ◽  
Joint Characteristics ◽  
Proposed Model ◽  
Mechanics Analysis ◽  
Stiffness And Damping ◽  
The Finite Element Model

Mechanical properties of the joints have impacted on the whole mechanical characteristics. Coupling the joint characteristics in the modeling of the machine tool is an important problem in machine mechanics analysis. In order to solve the joint modellings in the assembled structure, this paper presents a new method to creat beam elements between two symmetrical nodes on the contact surface of the joint. The stiffness and damping matrices of the elements are valuated according to the characteristics of the joint. To validate the accuracy of the proposed method, the modeling of an assembled structure with and without the joints is obtained and some corresponding experimental investigations are implemented. The error between the simulated and experimental results of the finite element model is less than 8.8%, while the error of the contact model often used in the existing literatures is one times bigger than the proposed model.

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