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Tmr01 2010 03_fundamentals_of_machining_tambahan

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Tmr01 2010 03_fundamentals_of_machining_tambahan

  1. 1. Mechanics of Cutting Mahfudz Al Huda Magister Teknik Mesin Univ. Pancasila, 2010 1          cos sin , 1 sin cos Cutting ratio, tan c o t t r -r α r α                  45 2 2 45 tan Shear angle predictions : 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
  2. 2. 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
  3. 3. 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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