scholarly journals Nonlinear behavior of disk spring with complex contact state

2021 ◽  
Vol 104 (4) ◽  
pp. 003685042110523
Author(s):  
Renzhen Chen ◽  
Xiaopeng Li ◽  
Zemin Yang ◽  
Jinchi Xu ◽  
Hexu Yang
Keyword(s):  
Dynamic Models ◽  
Contact Stiffness ◽  
Nonlinear Behavior ◽  
Friction Model ◽  
Contact Theory ◽  
Static Properties ◽  
Nonlinear Contact ◽  
Disk Spring ◽  
Linear Friction ◽  
Nonlinear Static

Disk springs are widely used as preload and isolation due to their unique mechanical properties. In the prior research, the effect of linear friction on the disk spring was considered, but contact stiffness, another nonlinear contact factor, is ignored. Accordingly, in this paper, the asymmetric displacements of the contact edges are first derived, and the accurate friction dissipations are obtained, as a way to evaluate the effect of friction on the system. Then the velocity of the edges was obtained to establish a dynamic friction model. Meanwhile, the contact displacement and contact stiffness of the edge are obtained by fractal contact theory. Then the nonlinear static and dynamic models of disk spring with friction and contact stiffness are established by the energy method. The load–deflection relationship, stiffness, and hysteresis of disk spring are studied with different contact states. The results show that the model considering contact stiffness and asymmetric friction dissipation can effectively evaluate the static properties of the disk spring. Friction reinforces the nonlinear behavior of the system, while contact stiffness weakens the nonlinearity of the system. And due to the influence of nonlinear contact factors, the transmissibility curves produce multiple resonance peaks.

A novel nonlinear contact stiffness model of concrete–steel joint based on the fractal contact theory

2018 ◽  
Vol 94 (1) ◽  
pp. 151-164 ◽  
Author(s):  
Yongsheng Zhao ◽  
Hongchao Wu ◽  
Zhifeng Liu ◽  
Qiang Cheng ◽  
Congbin Yang
Keyword(s):  
Contact Stiffness ◽  
Contact Theory ◽  
Steel Joint ◽  
Stiffness Model ◽  
Nonlinear Contact

The elastic contact influences on passive walking gaits

Robotica ◽  
2010 ◽  
Vol 29 (5) ◽  
pp. 787-796 ◽  
Author(s):  
Feng Qi ◽  
Tianshu Wang ◽  
Junfeng Li
Keyword(s):  
Coulomb Friction ◽  
Dynamic Models ◽  
Contact Stiffness ◽  
Contact Forces ◽  
Hertz Contact ◽  
Walking Gait ◽  
Routes To Chaos ◽  
Coulomb Friction Law ◽  
Contact Parameters ◽  
Passive Model

SUMMARYThis paper presents a new planar passive dynamic model with contact between the feet and the ground. The Hertz contact law and the approximate Coulomb friction law were introduced into this human-like model. In contrast to McGeer's passive dynamic models, contact stiffness, contact damping, and coefficients of friction were added to characterize the walking model. Through numerical simulation, stable period-one gait and period-two gait cycles were found, and the contact forces were derived from the results. After investigating the effects of the contact parameters on walking gaits, we found that changes in contact stiffness led to changes in the global characteristics of the walking gait, but not in contact damping. The coefficients of friction related to whether the model could walk or not. For the simulation of the routes to chaos, we found that a small contact stiffness value will lead to a delayed point of bifurcation, meaning that a less rigid surface is easier for a passive model to walk on. The effects of contact damping and friction coefficients on routes to chaos were quite small.

Nonlinear effect of tooth-slot transition on axial vibration, contact state and speed fluctuation in traveling wave ultrasonic motor

2017 ◽  
Vol 232 (19) ◽  
pp. 3424-3438 ◽  
Author(s):  
Dongsheng Zhang ◽  
Shiyu Wang
Keyword(s):  
Traveling Wave ◽  
Contact Stiffness ◽  
Nonlinear Phenomena ◽  
Axial Vibration ◽  
Contact State ◽  
State Response ◽  
Nonlinear Contact ◽  
Speed Fluctuation ◽  
Transition Force ◽  
Insight Into

The tooth-slot transition creates an axial excitation on traveling wave ultrasonic motors. It induces a rotor’s axial rigid vibration, which in turn affects the contact state and arouses speed fluctuation. To gain an insight into this problem, this work examines the relationships between the tooth-slot transition, axial vibration, nonlinear contact, and speed fluctuation. An analytical model governing rotor’s vibration is developed, where the transition force, nonlinear contact stiffness, and pre-pressure are included. The contact stiffness is demonstrated to decrease with an increase in stator’s vibration amplitude and it is approximated by polynomial fitting such that the nonlinear problem can be analytically solved. The primary, 1/2 subharmonic, and 2/1 superharmonic resonances are analyzed to determine the amplitude–frequency response and steady-state response. Nonlinear phenomena regarding the three types of resonances are identified. The interaction between the transition force, axial vibration, contact stiffness and speed fluctuation is investigated through a new contact model. The results imply that the rotor vibration induces rotating acceleration and leads to speed fluctuation. In addition, the rotor speed fluctuates in a similar fashion with the axial vibration.

scholarly journals Contact mechanics for soft robotic fingers: modeling and experimentation

Robotica ◽  
2012 ◽  
Vol 31 (4) ◽  
pp. 599-609 ◽  
Author(s):  
Sadeq H. Bakhy ◽  
Shaker S. Hassan ◽  
Somer M. Nacy ◽  
K. Dermitzakis ◽  
Alejandro Hernandez Arieta
Keyword(s):  
New York ◽  
Contact Mechanics ◽  
Weighted Least Squares ◽  
Theory Of Elasticity ◽  
Contact Theory ◽  
Nonlinear Contact ◽  
Different Types ◽  
Least Squares Curve Fitting ◽  
Almost All ◽  
Power Law Equation

SUMMARYHuman fingers possess mechanical characteristics, which enable them to manipulate objects. In robotics, the study of soft fingertip materials for manipulation has been going on for a while; however, almost all previous researches have been carried on hemispherical shapes whereas this study concentrates on the use of hemicylindrical shapes. These shapes were found to be more resistant to elastic deformations for the same materials. The purpose of this work is to generate a modified nonlinear contact-mechanics theory for modeling soft fingertips, which is proposed as a power-law equation. The contact area of a hemicylindrical soft fingertip is proportional to the normal force raised to the power of γcy, which ranges from 0 to 1/2. Subsuming the Timoshenko and Goodier (S. P. Timoshenko and J. N. Goodier, Theory of Elasticity, 3rd ed. (McGraw-Hill, New York, 1970) pp. 414–420) linear contact theory for cylinders confirms the proposed power equation. We applied a weighted least-squares curve fitting to analyze the experimental data for different types of silicone (RTV 23, RTV 1701, and RTV 240). Our experimental results supported the proposed theoretical prediction. Results for human fingers and hemispherical soft fingers were also compared.

Ciliary Vibration Drive Mechanism for Active Scope Cameras

2008 ◽  
Vol 20 (3) ◽  
pp. 490-499 ◽  
Author(s):  
Masashi Konyo ◽  
◽  
Kazuya Isaki ◽  
Kazunari Hatazaki ◽  
Satoshi Tadokoro ◽  
...  
Keyword(s):  
Dynamic Models ◽  
Friction Model ◽  
Activation Mechanism ◽  
Physical Factors ◽  
Stick Slip ◽  
Drive Mechanism ◽  
Inclined Angle ◽  
Optimal Driving ◽  
Flexible Cables ◽  
Physical Phenomena

The active scope camera we proposed has active mobility using a ciliary vibration drive mechanism for long flexible cables. The physical details have yet to be clarified. We determined it based on detailed physical phenomena to design an optimal ciliary vibration drive. We discuss the reasons for design efficiency based on the analysis of dynamic models of ciliary parts, focusing on (1) the characteristic vibration of the cilia and (2) stick-slip contact. We constructed a pseudo linear spring model and a stick-slip friction model to evaluate these phenomena. We determined optimal driving vibration frequencies and the inclined angle of cilia through experiments and analysis. Qualitative comparisons with the dynamic models and the results of experiments indicated the effective physical factors of the activation mechanism. A prototype of the active scope camera showed good performance in practical rescue activities.

Comparison of Initial and Improved Hertz-Damp Model for Structural Pounding Simulation

2011 ◽  
Vol 243-249 ◽  
pp. 686-690 ◽  
Author(s):  
Yong Qiang Yang ◽  
Li Li Xie
Keyword(s):  
Contact Stiffness ◽  
Superposition Method ◽  
Restitution Coefficient ◽  
Initial Model ◽  
Collision System ◽  
Structural Pounding ◽  
Mode Superposition Method ◽  
Nonlinear Contact ◽  
Simulation Results ◽  
Improved Model

In order to compare the initial and improved Hertz-damp model, the dynamic equations of collision system were established based on Hertz-damp model and mode superposition method. Hertz-damp model can account for the influence of the nonlinear contact stiffness as well as the energy loss during structural pounding. The results analysis show that the initial model have the same simulation results with the improved model initial model when the restitution coefficient or the contact stiffness large enough. For typical concrete structural pounding, the initial model is available.

scholarly journals A Bifurcation Analysis and Sensitivity Study of Brake Creep Groan

2021 ◽  
Vol 31 (16) ◽  
Author(s):  
Shaun Smith ◽  
James Knowles ◽  
Byron Mason ◽  
Sean Biggs
Keyword(s):  
Periodic Orbits ◽  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Period Doubling ◽  
Nonlinear Behavior ◽  
Sensitivity Study ◽  
Friction Model ◽  
Model Parameters ◽  
Period Doubling Bifurcations ◽  
Simple Models

Creep groan is the undesirable vibration observed in the brake pad and disc as brakes are applied during low-speed driving. The presence of friction leads to nonlinear behavior even in simple models of this phenomenon. This paper uses tools from bifurcation theory to investigate creep groan behavior in a nonlinear 3-degrees-of-freedom mathematical model. Three areas of operational interest are identified, replicating results from previous studies: region 1 contains repelling equilibria and attracting periodic orbits (creep groan); region 2 contains both attracting equilibria and periodic orbits (creep groan and no creep groan, depending on initial conditions); region 3 contains attracting equilibria (no creep groan). The influence of several friction model parameters on these regions is presented, which identify that the transition between static and dynamic friction regimes has a large influence on the existence of creep groan. Additional investigations discover the presence of several bifurcations previously unknown to exist in this model, including Hopf, torus and period-doubling bifurcations. This insight provides valuable novel information about the nature of creep groan and indicates that complex behavior can be discovered and explored in relatively simple models.

Investigation of normal and tangential contact stiffness considering surface asperity interaction

2019 ◽  
Vol 72 (3) ◽  
pp. 379-388
Author(s):  
Hongping Yang ◽  
Xiaowei Che ◽  
Cheng Yang
Keyword(s):  
Contact Mechanics ◽  
Fractal Geometry ◽  
Contact Stiffness ◽  
Contact Theory ◽  
Normal Contact ◽  
Tangential Contact ◽  
Content Type ◽  
Elastic Plastic ◽  
Stiffness Model ◽  
The Relationship

Purpose This paper aims to propose a normal and tangential contact stiffness model to investigate the contact characteristics between rough surfaces of machined joints based on fractal geometry and contact mechanics theory considering surface asperities interaction. Design/methodology/approach The fractal geometry theory describes surface topography and Hertz contact theory derives the asperities elastic, elastic-plastic and plastic contact deformation. The joint normal and tangential contact stiffness are obtained. The experiment method for normal and tangential contact stiffness are introduced. Findings The relationship between dimensionless normal contact load and dimensionless normal and tangential contact stiffness are analyzed in different plasticity index. The results show that they are nonlinear relationships. The normal and tangential contact stiffness are obtained based on theoretical and experimental methods for milling and grinding machined specimens. The results indicate that the present model for the normal and tangential contact stiffness are consistent with experimental data, respectively. Originality/value The normal and tangential contact stiffness models are constructed by using the fractal geometry and the contact mechanics theory considering surface asperities interaction, which includes fully elastic, elastic-plastic and fully plastic contacts deformation. The present method can generate a more reliable calculation result as compared with the contact model no-considering asperities interaction.

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