The mechanisms and applications of friction energy dissipation

About 30%of the world's primary energy consumption is in friction.The economic losses caused by friction energy dissipation and wear account for about 2%-7%of its gross domestic product(GDP)for different countries every year.The key to reducing energy consumption is to control the way of energy dissipation in the friction process.However,due to many various factors affecting friction and the lack of efficient detection methods,the energy dissipation mechanism in friction is still a challenging problem.Here,we firstly introduce the classical microscopic mechanism of friction energy dissipation,including phonon dissipation,electron dissipation,and non-contact friction energy dissipation.Then,we attempt to summarize the ultrafast friction energy dissipation and introduce the high-resolution friction energy dissipation detection system,since the origin of friction energy dissipation is essentially related to the ultrafast dynamics of excited electrons and phonons.Finally,the application of friction energy dissipation in representative high-end equipment is discussed,and the potential economic saving is predicted.

Prediction of electrical contact endurance subject to micro-slip wear using friction energy dissipation approach

Fretting wear is a common cause of failure of an electrical contact(EC). In this study, we analyzed in detail the failure of EC induced especially by sliding using the representative electrical terminals. Furthermore, combining the friction energy dissipation theory, we proposed a prediction model to evaluate the electrical connector endurance(ECE) based on the contact stress and geometrical changes during the wear process obtained from a numerical model. The study helps establish that the friction energy dissipation theory is a powerful tool to analyze a contact failure due to wear. The proposed model proves to be effective in predicting the ECE for all considered cases such as micro-slip amplitude, contact force, overturning angle, superficial layer thickness, and friction/wear coefficients.

Influence of contact curvature on frictional energy dissipation under varying tangential loads

This study investigates the effect of contact surface curvatures on the friction response under varying tangential loadings using a finite element(FE)model.The results showed that the geometry of the surface influences the contact force at the interface and reduces the friction effect through an unsteady distribution of the contact force.The relationship between the friction effect,excitation,and contact surface shape was also examined,revealing a linear inverse relationship between the friction and curvature.The findings provide a comprehensive understanding of the frictional interactions between elastic bodies and highlight the role of curvature as a design parameter for regulating the friction effect.

Research of a Response Precise Algorithm on a System with a Pseudo-viscous Frictional Energy Dissipator

The pseudo-viscous frictional energy dissipator（PVFED） is a new energy dissipator. This dissipator can be widely used in engineering for not only the friction is in direct ratio to velocity, but also the problem of viscous energy dissipator mucilage easily leaked has been overcome. The problem of how to get response of the PVFED sys- tem need to be solved before this dissipator can be used widely in engineering. The response calculation methods of the PVFED system on sina load was researched. Wilson-θ,Newmark-β and a precise integration algorithm was used separately to solve the system response and the calculation result in a different time step was compared. It was found from comparison that three calculation results were almost equivalent in a small time step. Calculation precision of Newmark-β and Wilson-θ was reduced and high calculation precision of a precise integration algorithm was kept in a large time step. The results show that it is an effective way to solve the response of a PVFED system by a precise integration method.

Experimental study of friction dissipators for seismic protection of building structures

This paper presents the results from unidirectional shaking table tests of two reduced scale steel models of a building frame, with one and two floors, respectively. These frames incorporate friction dissipators at every floor. The inputs are sine-dwells and artificial and registered earthquakes. This study is part of a larger research project aiming to assess the seismic efficiency of friction dissipators by means of an integrated numerical and experimental approach. Inside this framework, the main objectives of these experiments are to： （i） collect a wide range of results to calibrate a numerical model derived within the project, （ii） clarify some of the most controversial issues about friction dissipators （including behavior for inputs containing pulses, capacity to reduce resonance peaks, introduction of high frequencies in the response, and self- generated eccentricities）, （iii） better understand their dynamic behavior, （iv） provide insight on the feasibility and reliability of using simple friction dissipators for seismic protection of building structures and （v） characterize the hysteretic behavior of these devices. Most of these objectives are satisfactorily reached and relevant conclusions are stated.

Impact of Friction Stir Welding (FSW) Process Parameters on Thermal Modeling and Heat Generation of Aluminum Alloy Joints

Friction stir welding （FSW） is a solid-state joining process, where joint properties largely depend on the amount of heat generation during the welding process. The objective of this paper was to develop a numerical thermomechanical model for FSW of aluminum--copper alloy AA2219 and analyze heat generation during the welding process. The thermomechanical model has been developed utilizing ANSYS APDL. The model was verified by comparing simulated temperature profile of three different weld schedules （i.e., different combinations of weld parameters in real weld situations） from simulation with experimental results. Furthermore, the verified model was used to analyze the effect of different weld parameters on heat generation. Among all the weld parameters, the effect of rotational speed on heat generation is the highest.