Investigation Of The Fluid Behavior In Abrasive Wire Sawing

In recent years,with the rapid development of photovoltaic and optoelectronic industries,abrasive wire sawing technology has been widespread applications for slicing hard and brittle materials.In abrasive wire sawing,the significance of fluid should not be underestimated due to its main functions as follows: lubrication,cooling,chip removal,and carrying free abrasive particles for meterial removel.However,with the development trend in the industry such as the increase in material size,the reduction in the diameter of wire saws,the increase in sawing speed,and the replacement of single wire sawing by multi wire sawing,there appears larger sawing area,narrower sawing kerf,and more complicated sawing conditions,which poses entirely new challenges to the studty of fluid behavior in abrasive wire sawing.Aiming at the current challenges and problems,this paper investigate the fluid behavior on basis of two liquid supply methods: For the liquid supply mode in which the liquid flow is supplied to the sawing kerf,the spreading behavior of the liquid along the kerf and the liquid dynamic behavior in the sawing channel are studied;For the liquid supply mode in which the liquid flow is applied onto the wire and is brought into the sawing area by the moving wire,the liquid dynamic behavior under single-wire sawing and multi-wire sawing conditions is investigated respectively.The main work and important conclusions of the paper are as follows:(1)This paper bases on a method of numerical simulation in combined with experimental verification.The CFD softwares were used to establish the simulation physical models of the wire sawing under different conditions.These models fully considered the effects of multiple factors such as the flow state of the fluid,the surface tension and the contact angle of the fluid,etc.Based on the above models,the spreading behavior of liquid in the kerf and the liquid dynamic behavior in the sawing channel were successfully simulated.In addition,high-speed camera experiments were adopted to capture the liquid spreading behavior in the sawn kerf and the liquiddynamic behavior in the sawing channel under the actual processing state.There is a good agreement between simulation and experimental results,which confirms the correctness of the simulation model.(2)When the liquid enters the sawing area from the outside of the ingot along the kerf,the spreading behavior of the liquid in the kerf can be divided into three different regimes:(i)the liquid spreads up-down with an arc-shape spreading interface;(ii)the formation of the air chamber wrapped by the liquid layer surrounding the kerf;(iii)the liquid could not enter into the kerf.These three spreading regimes can be transformed with each other with changes in the kerf width,liquid viscosity,liquid surface tension,and inlet velocity.The main reason for the different spreading regimes of the liquid in the kerf is that the dominant force on the liquid in the saw gap is different under different conditions.(3)For the liquid supply mode in which the liquid flow is supplied to the sawing kerf,changes in factors such as wire speed,liquid viscosity,and surface tension will cause the liquid in the sawing channel to change from a relatively saturated and stable flow state to a unstable gas-liquid flow.More seriously,the sawing channel has almost no liquid and a large area of air layer appears there.The formation of the air entrainment phenomenon in the sawing channel is attribute to the contact angle between the liquid and the wire is greater than 180°,then the sawing wire brings the air into the sawing channel.(4)For the liquid supply mode in which the liquid flow is applied onto the wire,in both single-wire sawing and multi-wire sawing conditions,the contact area between the wire and the ingot in the sawing channel can be filled with liquid better.However,changes in wire speed and liquid properties can cause significant changes in the liquid state in the non-contact area of the sawing channel.The reduction of liquid viscosity and surface tension is conducive to the saturation and stability of the liquid in the sawing channel,meanwhile,it can make the pressure distribution in the sawing channel more stable.Compared to single-wire sawing,in multi-wire sawing,the liquid distribution in the sawing channel where the sawing wire is located in themiddle region is more saturated,which results in a more stable dynamic pressure distribution in the sawing channel arranged in the middle.(5)For the liquid supply mode in which the liquid flow is applied onto the wire net,in multi-wire sawing,the state of the liquid on the moving wire net can be divided into four categories:(i)There forms a uniform and stable liquid film on the moving wire net.(ii)There forms an unevenly unstable distributed and unstable liquid film on the moving wire net.(iii)The liquid flow cannot form a liquid film on the wire net,but a liquid layer with a relatively uniform thickness is formed on each wire.(iv)There forms liquid layer with non-uniform thickness on each single wire,and the local area of the wire cannot be completely wrapped.When the moving speed and the wire spacing of the wire net are small,it is easy to form a uniform liquid film on the wire net;Otherwise,it is difficult to form a liquid film.(6)Comparing with the two different liquid supply modes,it can be found that:under the liquid supply mode where the liquid is applied to the sawing wire,the liquid in the gap between the wire and the ingot is more likely to maintain a stable state,and the pressure distribution in the contact area is more stable;but in non-contact arae,the liquid state is relatively easy to fluctuate.Under the liquid supply mode where the liquid is applied to the kerf,the liquid pressure distribution in the non-contact area is basically stable;however,unstable liquid state easily occurs in the contact gap,and the pressure distribution fluctuates greatly.This paper provides a theoretical basis for deeply understanding of the wire saw sawing behavior,which has has practical guiding significance for optimizating the wire sawing process.