ME364_cutting_mechanics - Valery Marinov, Manufacturing...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Mechanics of Machining 67 Valery Marinov, Manufacturing Technology 5.2 MECHANICS OF MACHINING Plastic deformation in cutting The cutting itself is a process of extensive plastic deformation to form a chip that is removed afterward. The basic mechanism of chip formation is essentially the same for all machining operations. Assuming that the cutting action is continuous, we can develop so-called continuous model of cutting process shown in the ±gure: Cutting speed V Cutting speed, V Direction of primary motion shear plane h ch h D b D % # ! "# ! $ # tool face s e a r + f i c t o n workpiece chip cut tool (a) (b) (c) (a) Chip formation in metal cutting is accompanied by substantial shear and frictional deformations in the shear plane and along the tool face; (b) Schematic illustration of the two-dimensional cutting process (also called orthogonal cutting ), h D and b D are the thickness of cut and width of cut respectively, h ch is the chip thickness , γ o is the tool orthogonal rake angle, and Φ is the shear plane angle ; (c) Cutting with positive and negative rake angles. Note the change in the shear plane angle and chip thickness. Cutting is performed with a cutting tool moving at a cutting speed V in the direction of primary motion. The cutting tool is inclined at the rake angle γ o . The rake angle can be positive, zero, or negative, typically taking values from +15 o to -6 o . The rake angle in²uences signi±cantly the process of plastic deformation in cutting and therefore the chip thickness, cutting forces and temperatures. The tool is set to remove a cut with thickness h D and width b D . In the simplest model of orthogonal cutting shown in the ±gure, the plastic deformation takes place by shearing in a single shear plane inclined at the angle Φ ( shear plane angle ). The produced chip has a thickness of h ch ( chip thickness ), width b D and moves at speed V ch ( chip speed ). The chip thickness compression ratio Λ h is de±ned by Λ h = h ch /h D Chip thickness is always bigger than thickness of cut, therefore Λ h is always >1. The value of chip thickness compression ratio gives a valuable information about the rate of plastic deformation in the
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

ME364_cutting_mechanics - Valery Marinov, Manufacturing...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online