Upload
lijo621
View
1.065
Download
2
Tags:
Embed Size (px)
DESCRIPTION
lijo's
Citation preview
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