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Flashcards in Ur NAN Deck (11):
1

Name all the different types of chips that are produced in metal cutting and under what conditions they occur under.

Continuous chips

  • Ductile materials, high cutting speed, high rake angles
  • Deformation takes place in narrow shear zone
  • Can develop secondary shear zone due to high friction at the tool

 

BUE

  • Grows then breaks apart
  • Can be reduced by:
    • Higher cutting speeds
    • Decrease depth of cut
    • Increase rake angle
    • Use sharp tool
    • Use effective cutting fluid
    • Use lower chemical affinity cutting tool

 

Serrated Chips

  • Semi continuous chips with large zones of low shear strains and small zone of high shear strain

 

Discontinuous chips

  • Consists of segments that attached firmly or loosely to each other
  • Form under the following conditions:
    • Brittle workpiece materials
    • Materials with hard inclusions and impurities
    • Very low or very high cutting speeds
    • Large depths of cut
    • Low rake angles
    • Lack of an effective cutting fluid
    • Low stiffness of the machine tool

2

Draw and explain the different types of chip formation as the cutting speed increases

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3

What are the different tools to measure cutting forces?

Force transducer

Dynamometer

Load cell mounted on the cutting tool holder

Measure the current draw from the servo motors

4

Why do we want to avoid high cutting temperatures?

 

Affects the wear of the cutting tool. Cutting temperature is the primary factor affecting tool wear

 

Can induce thermal damage to the machined surface

 

Causes dimensional errors in the machined surface

 

5

What are the different types of cemented carbides

 

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6

Draw the graph of tool life vs cutting time for increasing cutting speeds

 

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7

Draw a graph showing how cobalt content affects hardness, compressive strength, transverse-rupture strength and wear of the tool.

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8

Draw the graph of how pearlite to ferrite % of a material affects the tool life with cutting speed.

 

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9

 Define Surface finish and surface finish integrity and give factors affecting SI.

  • SF (Surface finish) – geometric features of surfaces
  • SI (Surface integrity) – refers to properties such as fatigue life and corrosion resistance
  • Factors influencing SI:
    • Temperature
    • Residual stresses
    • Metallurgical transformations
    • Surface plastic deform, tearing and cracking
  • BUE has greatest influence on SF

10

 

Draw roughness and waviness on a surface of a work material

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11

What is the surface roughness equation?

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