A study of normal stiffness model of joint interfaces based on fractal theory

2015 ◽  
pp. 151-156
Keyword(s):  
Fractal Theory ◽  
Normal Stiffness ◽  
Stiffness Model

A normal contact stiffness model of machined joint surfaces considering elastic, elasto-plastic and plastic factors

2019 ◽  
Vol 234 (7) ◽  
pp. 1007-1016 ◽  
Author(s):  
Yongquan Zhang ◽  
Hong Lu ◽  
Xinbao Zhang ◽  
He Ling ◽  
Wei Fan ◽  
...  
Keyword(s):  
Surface Topography ◽  
Contact Stiffness ◽  
Fractal Theory ◽  
Fractal Model ◽  
Single Pair ◽  
Machined Surface ◽  
Normal Contact ◽  
Joint Surfaces ◽  
Stiffness Model ◽  
Normal Contact Stiffness

Considering the rough surface as a fractal model makes the research of contact parameters more practical. In the fractal model of the machined surface, the parameters describing the surface topography are independent of the measurement resolution. Based on the elastic, elasto-plastic and plastic deformations of a single pair of contact asperities, a normal contact stiffness model using the fractal model for surface topography description is proposed in this paper. The specimens machined by milling and grinding methods are used to verify the proposed contact stiffness model based on the fractal theory. The experimental and theoretical results indicate that the proposed contact stiffness model is appropriate for the machined joint surfaces.

Torsional Stiffness Model of an Industrial Robotic Joint Using Fractal Theory

2019 ◽  
Author(s):  
Jingjing Xu ◽  
Zhifeng Liu ◽  
Yongsheng Zhao ◽  
Qiang Cheng ◽  
Yanhu Pei ◽  
...  
Keyword(s):  
Prediction Accuracy ◽  
Fractal Theory ◽  
Great Influence ◽  
Joint Stiffness ◽  
Equilibrium Analysis ◽  
Torsional Stiffness ◽  
Tangential Stiffness ◽  
Proposed Model ◽  
Stiffness Model ◽  
Rv Reducer

Abstract It is known that mechanical connections have great influence on the dynamic characteristic of the assembly. In existing methods, the torsional stiffness of the robotic joint is calculated only considering the stiffness of components of the system, which largely reduces the prediction accuracy of the joint stiffness. In the paper, to predict the joint stiffness more accurately, a model is proposed considering influences of the stiffness of all connections existed in a joint system. The normal and tangential stiffness of the contact surface of each connection are calculated by combining the equilibrium analysis of the force and the fractal theory. Then the total stiffness of one robotic joint can be modelled by putting the torsional stiffness of all connections and that of the RV reducer and gear pair in parallel. To verify the proposed model, its simulation result is compared to the stiffness based on the previous technique without considering the influence of connections. The comparison result shows that the proposed model can improve the stiffness-prediction accuracy. This study can be extended to the stiffness modeling of other joint systems and provides a theoretical basis for the dynamic analysis of the robotic system.

A stiffness model for bolted joints considering asperity interactions of rough surface contact

2021 ◽  
pp. 1-20
Author(s):  
Hua Zhou ◽  
Xinhua Long ◽  
Guang Meng ◽  
Xianbo Liu
Keyword(s):  
Contact Stiffness ◽  
Classical Model ◽  
Surface Profile ◽  
Bolted Joints ◽  
Normal Stiffness ◽  
Proposed Model ◽  
Stiffness Model ◽  
Fractal Roughness ◽  
Rough Surface Contact ◽  
Stiffness Loss

Abstract A revised fractal contact model considering asperity interactions is proposed. The displacement of mean of asperity heights is used to represent the effects of the asperity interactions. Then the critical contact area will be dependent on the contact load and the contact stiffness will be an integral whose integrand is an implicit expression. The fractal dimension and the fractal roughness are obtained by the measurement of surface profile to calculate the theoretical contact stiffness. The measurement of deformation is conducted to obtain the actual contact stiffness for verification, the results show that the proposed model is closer to the experimental results than other models without considering asperity interactions. Once the contact stiffness is determined, a new total normal stiffness model for bolted joints considering the contact of two rough surfaces is also proposed. Since the contact stiffness is dependent on the clamped force, the total normal stiffness for bolted joints is calculated iteratively at given initial preload and external separating force. Different from the classical model, the total normal stiffness for bolted joint decreases with the external separating force increases, and this stiffness loss will become larger with initial preload decreases. In this sense, the proposed total normal stiffness model is a way to determine the suitable initial preload for different sizes of bolts when the stiffness loss is restricted to a certain range.

scholarly journals The Normal Dynamic Stiffness Model of Joint Interfaces Based on Fractal Theory

2019 ◽  
Vol 267 ◽  
pp. 032055
Author(s):  
Wenwei Liu ◽  
Yuanhang Wang ◽  
Xiaobing Li ◽  
Jianfeng Yang ◽  
Chengju Dong
Keyword(s):  
Dynamic Stiffness ◽  
Fractal Theory ◽  
Stiffness Model

A Contact Stiffness Model of Machined Plane Joint Based on Fractal Theory

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Shuyun Jiang ◽  
Yunjian Zheng ◽  
Hua Zhu
Keyword(s):  
Contact Stiffness ◽  
Fractal Theory ◽  
Fractal Model ◽  
Experimental Results ◽  
Size Dependent ◽  
Contact Loads ◽  
Proposed Model ◽  
Stiffness Model ◽  
Surface Profiles ◽  
Plane Joint

A general contact stiffness model is proposed in this paper to study the contacts between rough surfaces of machined plane joints. The proposed model uses fractal geometry for surface topography description, elastic-plastic deformation of contacting asperities, and size-dependent contact stiffness of microcontacts, where the contact stiffness is derived from Hertz contact theory. Three cast iron specimens are produced from different machining methods (milling, grinding, and scraping), and their rough surface profiles are extracted. The structure function method was used to calculate each profile’s fractal dimension and scale coefficient. Both theoretical analysis and experimental results of contact stiffness are obtained for these specimens under different contact loads. The comparison between the theoretical contact stiffness and the experimental results at the interface indicates that the present fractal model for the contact stiffness is appropriate and the theoretical contact stiffness is consistent with the experimental data.

A stiffness model of a joint surface with inclination based on fractal theory

2020 ◽  
Vol 62 ◽  
pp. 47-61 ◽  
Author(s):  
Zhifeng Liu ◽  
Kai Jiang ◽  
Caixia Zhang ◽  
Yongsheng Zhao ◽  
Yang Tian
Keyword(s):  
Fractal Theory ◽  
Joint Surface ◽  
Stiffness Model
Sign in / Sign up

Export Citation Format

Share Document