Mechanics of Cutting
Mahfudz Al Huda Magister Teknik Mesin Univ. Pancasila, 2010 1
cos
sin ,
sin1
costan ratio, Cutting
c
o
t
tr
α-r
αr
45
2245
tan
:sprediction angleShear
Velocities, Vc V sin
cos
r = cutting ratio
t0 = depth of cut, mm
tc = the chip thickness, mm
= shear angle,
= rake angle,
= coefficient of friction
= friction angle,
V = cutting speed, m/min
Vc = the velocity of the chip, m/min
Cutting Mechanisms
Mahfudz Al Huda Magister Teknik Mesin Univ. Pancasila, 2010 2
Asumsi-2 dlm membahas cutting mechanism:
•Proses pemotongan adl orthogonal cutting.
•Tool Speed, VT = 0
•Workpiece Speed = Cutting Speed = V
•Benda kerja terpotong krn terjadi deformasi plastis berupa slip
pd bidang geser (shear plane) akibat tekanan geser (shear stress).
•Slip terjadi secara teratur pd lapisan tipis geram dg tebal X dan
bergeser sejauh S, maka regangan geser (shear strain):
dimana : shear angle, : rake angle.
•Chip speed VC, dan Shear speed VS:
•Shear strain speed:
•Cutting ratio:
t1 & t2: tebal geram sebelum dan sesudah dipotong
•Cutting force R:
FH & FV: gaya potong horizontal & vertical, dpt diperoleh dg
mengukur gaya tsb menggunakan strain gauge atau tool
dynamometer.
Tool
Tool
Workpiece
Workpiece
Cutting Mechanisms
Mahfudz Al Huda Magister Teknik Mesin Univ. Pancasila, 2010 3
•Koefisien gesek (friction coefficient) pd rake face:
: friction angle, F& N: gaya gesek & gaya normal pd rake face.
•Gaya-gaya pd bidang geser (shear plane):
FS & FN: gaya geser (shear force) & normal pd shear plane.
•Sudut geser (shear angle) :
shg sudut geser dpt dihitung dg mengukur tebal geram sebelum dan sesudah pemotongan dan rake angle.
•Gaya-gaya pada rake face:
•Tegangan geser (shear strain) pd shear plane:
dimana AS: luas bidang geser, b: cutting width, S & S: tegangan geser (shear stress) & tegangan normal
(normal stress) pd bidang geser.
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