problem in machining forces

problem in machining forces - F t F n F c F s Shear angle )...

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Dynamic Shear Stress Prof. Christopher Brown
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Analysis problem in machining Describe how to find the dynamic shear stress (Fs/As) from the power, cutting conditions and the chip thickness. Given or measured: t1 (feed), t2, power, speed, rake angle
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Shear angle - orthogonal Shear angle φ From Geometry: tanφ = r t cos α / (1- r t sin α) Chip thickness ratio r t = t 1 /t 2 Uncut chip thickness t 1 or depth of cut in orthogonal machining Vc – cutting velocity α Rake angle t 1 t 2
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Angles Rake α Shear φ Friction τ friction angle F t F n F c F s Forces (total P) Cutting Fc Thrust Ft Shear Fs Normal Fn (to Shear Plane) Friction F Normal N (to Rake Face) Machining forces
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Machining forces and Friction α sin cos c t F F F + = sin cos t c F F N - = φ sin cos t c s F F F - = cos sin t c n F F F + = Rake face Frictional force and normal force Shear plane forces F t F n F c F s N F = = τ μ tan tan tan t c c t F F F F - + = Tool workpiece friction coefficient µ
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Friction to shear angle 2 / 2 / 4 / α τ π φ + - = d/dφ(Fc=f(φ)) = 0 Orient the shear angle to minimize the cutting force Merchant Equation (in radians)
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Unformatted text preview: F t F n F c F s Shear angle ) cos( sin / ) cos(-+-= bA F C solution From t1 and t2 get the chip thickness ratio and calculate the shear angle tan = r t cos / (1- r t sin ) r t = t1/t2 From the power and the speed get the cutting force Fc Power = Fc speed From the shear angle and the rake angle get the friction angle From the friction angle calculate the friction coefficient 2 / 2 / 4 / +-= N F = = tan Cont. From the friction coefficient and the cutting force calculate the trust force from: Ft = ( Fc - Fc tan) /(1+ tan) tan tan t c c t F F F F-+ = Calculate Fs from: Calculate the dynamic shear stress Sd from Sd = Fs/As As = w t1/sin sin cos t c s F F F-=...
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This note was uploaded on 04/29/2008 for the course ME 1800 taught by Professor Brown during the Winter '08 term at WPI.

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problem in machining forces - F t F n F c F s Shear angle )...

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