Effect Of Surface Groove Filling And Combined Regulating Methods On Tribological Behavior

Energy conservation and environmental protection is a trending development in every aspect of today’s society.In mechanical systems,most physical processes like energy exchange,motion and signal transmission are realized through surface contact.However,solid mechanical surface contact inevitably leads to two troublesome problems which have hunted people for centuries,i.e.,friction and wear.The friction generated at the contact interface can cause severe material loss,component failure and energy dissipation,resulting in incalculable indirect economic loss every year.Moreover,frictional contacts generally cause another unwanted observation-friction-induced vibration and noise.This phenomenon is widely observed in mechanical systems with relative motions,such as vehicle brake systems,gear systems,guide rail,pin connections,artificial joints,et al.It can not only cause noise emissions,but also can reduce machining accuracy,accelerate parts fatigue,reduce machine life,and even lead to serious accidents.In reality,tribological problems has been a vicious circle.Up to now,friction and wear and friction-induced vibration and noise have become a typical research field of tribology,in which many significant research results have been achieved.In the author’s opinion,an in-depth study of the tribological behavior at the contact interface（wear and friction-induced vibration and noise）from the perspective of how interfacial characteristics affect tribological properties is meaningful,and which can simultaneously solve practical engineering problems and promote sustainable development in mechanical engineering field.With the continuous deepening of tribology research and the increasingly higher requirements on the tribological behaviors at the contact interface of mechanical parts,new breakthroughs have been made in the ways of regulating and improving the interfacial properties.As an effective interfacial control method,surface texturing（surface modification）has been used to study the relationship between interfacial properties and friction-induced vibration and noise,and some surface texture structures that can effectively reduce the friction-induced vibration and noise are fabricated and correspondingly the surface modification mechanisms have been revealed.However,compared with the researches on surface texturing in the field of friction and lubrication,few researches have explored the relationship between surface texturing and FIVN;Meanwhile,the influence mechanism of the surface texturing on the interfacial tribology behavior is rather complicated and there is still a huge lack of knowledge about it,it is hence of great significance to further optimize the tribological behavior of the interface with the help of surface"modification"method,aiming at further revealing how the surface texture characteristics affect the interfacial tribology behavior and guiding the design of surface textures to meet practical engineering problems.In this paper,the author is enlightened from surface"modification"design strategy.By filling the surface grooves with additive materials or combining damping components with surface texture,the author explored a series of new ways to modify the contact interface.Experimental and theoretical studies were carried out to investigate the performance of different surface modification methods affecting the interfacial tribology behaviors.The main conclusions of this work are summarized as follows:（1）To explore the influence of wear properties and its rheology on interfacial tribological behavior,a certain size groove is fabricated on a surface of compacted graphite iron,then pure phenolic resin and phenolic resin with Mo S₂ additives were respectively filled into the surface groove to obtain a surface with time-varying contact characteristic,which aimed at changing the interfacial contact characteristics and introducing different wear ingredients to the interface.Then tribological tests of the prepared sample surfaces against a ball sample were carried out under reciprocating working conditions.The prepared surfaces then undergo reciprocating testing in a ball-on-flat set-up.The friction-induced vibration and noise（FIVN）at the different stages of the experiment process and the corresponding wear morphology/topography were analyzed.Based on the relationship between the evolution of the FIVN and the characteristics of wear morphology,the influence mechanism of wear debris and its rheology on wear,interfacial interaction and FIVN was investigated.The results show that the generation and evolution of FIVN are directly related to the dynamical interfacial characteristics（Adhesion,detachment,ploughing）.The interfacial interaction resulted in dynamical interfacial characteristics cause fluctuation of the friction force and eventually leads to the generation of FIVN.The friction debris generated from the fillers was found to have a significant effect on the interfacial dynamic characteristics and the interfacial interaction,if their joint effect on the fluctuation of the friction force can be weakened,then the purpose of FIVN reduction can be achieved.The time-varying contact characteristic surface filled with phenolic resin containing Mo S₂ additive can not only exhibit better interfacial wear performances and FIVN suppression,but also show mild fluctuations in the friction force as the filler contributed to alleviate the collision between the ball and the groove edge.Therefore,a reasonable filler can effectively improve the wear state and form better interfacial properties,which helped to suppress the generation of FIVN.（2）In view of the important influence of the properties and rheology of wear debris on the interfacial tribological behavior,the surface optimization design method which can better serve the engineering practice is explored.A surface groove is fabricated on a forged steel sample,in which gray iron（HT300）possessing similar hardness to the substrate material was filled.In view of the damping properties of HT300,another two kinds of time-varying contact characteristics surfaces,which were grooved forged steel sample filled with Mn-Cu alloy and Mn-Cu damping alloy respectively,were designed to distinguish the role of interfacial wear and material damping properties influencing FIVN.By comparing the test results of the four kinds of surfaces（Smooth forged steel surface,grooved forged steel filled with HT300,grooved forge steel filled with Mn-Cu alloy and Mn-Cu damping alloy）,the differences of the friction-induced noise,friction-induced vibration and wear morphology between different surfaces were analyzed.The influence of time-varying contact surface on the interfacial tribological behavior was systematically discussed.The results showed that the FIVN caused by the instability of the friction system were mainly attributed to the interfacial interactions of adhesion tearing and ploughing in the friction process.It was also suggested that the damping properties of the filling material had little influence on FIVN.The time-varying contact characteristics surface filled with HT300alleviated the interfacial wear,weakened the interfacial interactions,which effectively strengthened the stability of the friction system and suppressed the FIVN generation.On the contrary,the surface sample filled with and Mn-Cu damping alloy showed aggravated interfacial wear situation,the instability of the friction system was easier to be triggered,which led to strong FIVN.（3）Based on the results of the second part,A certain size of grooves were fabricated on the surface of al friction block,which was then filled with gray cast iron HT300 to obtain a special surface possessing different contact characteristics.The aim of this part was to verify if the basic research in the second part can meet the requirements in face-to-face contact circumstances.The tribology behaviors of the three kinds of block samples（untreated friction block,grooved friction block;grooved friction block filled with gray cast iron HT300）were investigated under face-to-face contact mode.Combined with the experimental results and the finite element analysis,the influence of different contact characteristics of friction blocks on the interfacial tribology behavior was discussed.The experimental results and finite element analysis showed that the friction blocks with different contact characteristics had different wear characteristics,which consequently resulted in different FIVN performance.In particular,the"new"debris generated in the friction process when the surface grooves were filled with HT300,which can contribute to effectively adjust the interface wear state,reduce contact stress concentration,increase the adhesion degree at the friction contact interface and stabilize the contact state at the interface.Therefore,the HT300 filled friction block behaved the best FIVN performance among the three different friction blocks.（4）In order to investigate the effect of the adhesion degree of friction interface on tribological behavior,three different interface adjusting strategies were studied in this part,i.e.,direct modification through surface texturing,indirect modification through damping components and composite modification strategy by combining damping components and surface texturing.Hence,three different friction blocks were designed,the first one contained a grooved friction block sample.The second one had a damping component on the back plate of the friction block but the contact surface was smooth.And the third one contained both grooved surface and damping component.Based on tribology test,friction interface pressure test and finite element analysis,the mechanisms of the three different modification methods and the untreated friction block were comprehensively studied both experimentally and numerically.The experimental results and finite element analysis showed that the adhesion degree of friction interface had an important effect on the interfacial tribological behavior.Compared with the friction system without any surface modification,the damping element installed on the back of the friction block or the grooves processed on the surface of the friction block can make the contact area extend from the inner-leading edge to the outer-trailing edge of the contact interface instead of being concentrated at the inner-leading leading edge,therefore the interfacial contact state was improved and the surface wear was alleviated,interfacial interactions was weaken,making the friction system stay in a stable state.When damping element combined with surface grooves,it suggested that the interfacial modification effect was more evident than any of the single strategy.A further improved contact behavior at the interface was observed,therefore,the friction system with composite modification strategy had a greater potential to be stable and produce less FIVN in the friction process.