Cost-Effective Machining of Granite by Reducing Tribological Interactions

In order to implement cost-effective machining of gr anite materials with diamond impregnated tools, we should realize low tool w ear, low energy consumption, and high cutting efficiency, while the accuracy of the workpiece surfaces are maintained to be satisfactory. It is understood that the main factors affecting the tool wear, the energy, and the efficiency during the machining process are related to the tribological interactions that occur at the interface between the diamond tool surface and the workpiece. Based on this consideration, we propose a new machining method to machine granite materia ls to achieve improved cost effectiveness. In the proposed method, the tribologi cal interactions are maintained to a minimum. Based on the analyses of the experimental results, the following conclusions can be drawn: The wear performance is greatly dependent on the machining parameters and their combination. Therefore, optimum machining parameters must be set up at first in order to optimize the tribological characteristics of segments and thereby sawbl ade performance. These may be realized by balancing the energy expended by frict ion and the mechanical load on diamond crystal. The geometry and structure of diamond segments are another important criterion f or the diamond saw blade. Using a seven-layer structure for multi-blades sawin g and applying segments with side slots for trimming application had greatly red uced the frictions in the sawing processes. The wetting and bonding between diamonds and matrix alloys have been considered as the prerequisite for high wear performance of the segments. Diamonds coated w ith Ti-Cr alloy by a unique technique can effectively improve its wetting c apability and provide more storage space for debris, thereby reducing friction i nteractions.

Interactive mechanism and friction modelling of transient tribological phenomena in metal forming processes: A review

The accurate representation of tribological boundary conditions at the tool–workpiece interface is crucial for analysis and optimization of formability,material flow,and surface quality of components during metal forming processes.It has been found that these tribological conditions vary spatially and historically with process parameters and contact conditions.These time-dependent tribological behaviours are also known as transient tribological phenomena,which are widely observed during forming processes and many other manufacturing application scenarios.However,constant friction values are usually assigned to represent complex and dynamic interfacial conditions,which would introduce deviations in the relevant predictions.In this paper,transient tribological phenomena and the contemporary understanding of the interaction between friction and wear are reviewed,and it has been found that these phenomena are induced by the transitions of friction mechanisms and highly dependent on complex loading conditions at the interface.Friction modelling techniques for transient behaviours for metal forming applications are also reviewed.To accurately describe the evolutionary friction values and corresponding wear during forming,the advanced interactive friction modelling has been established for different application scenarios,including lubricated condition,dry sliding condition(metal-on-metal contact),and coated system.

Experimental and modelling study of interaction between friction and galling under contact load change conditions

The galling process remains one of the least understood phenomena in metal forming.The transfer of material from a work-piece onto the tool surface can cause an evolutionary increase in friction coefficient(COF)and thus the use of a constant COF in finite element(FE)simulations leads to progressively inaccurate results.For an aluminium work-piece,material transfer,which has history and pressure dependency,is determined by a dynamic balance between the generation and ejection of wear particles acting as a‘third body’abrasive element at the contact interface.To address this dynamic interactive phenomenon,pin-on-disc tests between AA6082 and G3500 were performed under step load change conditions.The COF evolutions,morphologies of the transfer layer and its cross-section were studied.It has been found that contact load change will disequilibrate and rebuild the dynamic balance and high load will increase the generation and ejection rate of third body and vice versa.Moreover,based on the experimental results,an interactive model was developed and presented to simulate the dynamic formation process of the aluminium third body layer under load change conditions,enabling multi-cycle simulations to model the galling distribution and friction variation.

Experimental and modelling studies of the transient tribological behaviour of a two-phase lubricant under complex loading conditions

The transient tribological phenomenon and premature lubricant breakdown have been widely observed in metal forming,leading to excessive friction at the contact interfaces.In this research,the transient tribological behaviour of a two-phase lubricant were studied under complex loading conditions,featuring abrupt interfacial temperature,contact load,and sliding speed changes,thus representing the severe interfacial conditions observed in warm/hot metal forming applications.The strong experimental evidence indicates that the evolution of friction was attributed to the physical diminution and chemical decomposition effects.As such,a visco-mechanochemical interactive friction model was developed to accurately predict the transient tribological behaviour of the two-phase lubricant under complex loading conditions.The new friction model exhibited close agreements between the modelling and experimental results.