Cutting temperature

Cutting Temperature

Dr Jose Mathew

Sources of heat generation in cutting

Distribution of heat

Effects of High Temperature

On Tool:Rapid Tool wearPlastic deformation of edgeThermal flaking and deformationBUE formation

Effects of High Temperature

On Workpiece:*Thermal distortion and dimesionalinaccuracy*Surface damage by oxidation, corrosion, burning, etc.*Thermal micro cracks and residual stresses> Hot machining

Purpose of measuring temp.

Assessment of machinabilityDesign and selection of cutting toolsHelps to proper selection of toolsProper selection of cutting fluidsAnalysis of temp distribution

θs : average shear zone temperature θi : average (and maximum) temperature

at the chip-tool interface θf : temperature at the work-tool interface (tool fθavg : average cutting temperature

Important parameters for temperature

Measurement of Temperature

* Analytical* Experimental

Analytical methodW=Wp+Ws ( W –total heat generated)Ws =FVc=FrVWp=FcV-FrVƟp =(1-ß)Wp / (ƿcVt1w)-ß fraction of primary heat which goes to the workpiece- ƿ density of the material

- c sp. Heat of the material- t1, w Uncut thickness, width of cut

� is a function of shear angle Φand non dimesional quantity ƏƏ= ƿcVt1/kk-thermal conductivity of the material

�ß =0.15 ln (27.5/ Ə tan Φ)

ƟS + 1.13√[ (Ət2/l)(Ws/ƿcvwt1)]l - length of contact bet.tool and chip

Ɵs av = Ws/ƿcvwt1

l/t2 = [1+tan (Φ -α )]

Ɵs=1.13 √(1/ƿcvt1k[1+tan (Φ -α )] (Ws/w)

Ɵ= Ɵ0+ Ɵp +ƟS

Experimental methods

Tool work thermocouple method

Moving thermocouple

Embedded thermocouple

Compound rake used to measure the cutting temperature along the rake face

Measuring temperature at shear plane and tool flank by photocell technique

Temperature distribution at the tool tip detected by infra ray technique

Role of variation of the various machining parameters on cutting temperature