Effect of Tangential Velocity Rise on Tool Wear in Machining
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Questions and Answers

What effect does tangential velocity rise have on friction power?

  • Decreases friction power
  • Halts friction power entirely
  • Has no effect on friction power
  • Leads to a rise in friction power (correct)

    • Why does the tool rake face soften, wear, and break under high pressure and temperature?

  • Because of increased temperature rise (correct)
  • Due to decreased tangential velocity
  • No correlation with pressure or temperature
  • Due to decreased temperature rise

    • What helps manufacturing engineers seek a compromise between productivity and temperature rise?

  • Decreasing cutting speed
  • Increasing cutting speed (correct)
  • Using low heat-resistant tool materials
  • Utilizing high friction angle

    • How does the frictional force change with a decrease in the friction angle?

    <p>Frictional force decreases</p> Signup and view all the answers

    What is needed to guard against critical diffusion or melting temperature limits at the tool-chip interface?

    <p>Tool geometry improvements</p> Signup and view all the answers

    What is the main purpose of seeking heat-resistant tool materials for manufacturing engineers?

    <p>To preserve hardness at elevated temperatures</p> Signup and view all the answers

    What is the formula for the shear plane temperature?

    <p>𝑇𝑠𝑝 = 𝐹𝑠𝑠𝑝𝑉𝑠𝑝 𝑚̇𝑐𝑝𝑐 + 𝑇𝑎</p> Signup and view all the answers

    What does the power term 𝑃𝑟𝑓 represent in the context of the cutting process?

    <p>Friction power dissipated at the chip-rake face interface</p> Signup and view all the answers

    How is the impulsive force 𝐹𝑖𝑚 calculated along the shear plane?

    <p>𝐹𝑖𝑚 = 𝑚̇𝑐𝑝 [𝑉𝑐ℎ cos(𝜑𝑟𝑓 + 90 − 𝜑𝑠𝑝 ) + 𝑉𝑡 cos(𝜑𝑠𝑝 )]</p> Signup and view all the answers

    What is the power term 𝑃𝑚𝑐 related to in the cutting process?

    <p>Power consumed in plastic deformation and friction</p> Signup and view all the answers

    In the equation 𝑃𝑠𝑚 ≈ 𝜌𝑤ℎ𝑉𝑜∆T, what does ∆T represent?

    <p>Average temperature rise in the chip</p> Signup and view all the answers

    Based on the text, how are different materials compared in terms of their resistance to cutting force?

    <p>By using the specific energy requirements</p> Signup and view all the answers

    What does the shear plane area formula represent in manufacturing science and engineering?

    <p>The area of the material being sheared away from the workpiece</p> Signup and view all the answers

    In the context of manufacturing science and engineering, what is the significance of shear stress?

    <p>It quantifies the force required to shear the material from the workpiece</p> Signup and view all the answers

    How does shear velocity contribute to the cutting process in manufacturing?

    <p>It adds vectorially with the chip velocity to balance the cutting velocity</p> Signup and view all the answers

    What does the constant normal stress indicate in manufacturing science and engineering?

    <p>The stress acting perpendicular to the shear plane during cutting</p> Signup and view all the answers

    How is chip compression ratio indirectly affected by the shear plane area?

    <p>It increases as the shear plane area decreases</p> Signup and view all the answers

    What is the result of the shearing process described in the text?

    <p>Plastic deformation of the material</p> Signup and view all the answers

    How is shear displacement of planes ahead of the shear plane caused?

    <p>By shear stress</p> Signup and view all the answers

    What is the relationship between shear strain rate and the time interval of shear process?

    <p>Directly proportional</p> Signup and view all the answers

    How is shear strain rate calculated based on the text?

    <p>𝛾̇𝑠 = tan(𝛾𝑠) / ∆𝑡</p> Signup and view all the answers

    What is the overall effect of plane strain conditions on the material within triangles?

    <p>Material gets displaced</p> Signup and view all the answers

    How does shear velocity impact shear stress according to the text?

    <p>Shear velocity increases shear stress</p> Signup and view all the answers

    What is the expression for the shear force on the shear plane according to the text?

    <p>𝐹𝑡 sin(𝜑𝑠𝑝 ) + 𝐹𝑓 cos(𝜑𝑠𝑝 )</p> Signup and view all the answers

    How is the normal force on the shear plane calculated based on the provided information?

    <p>𝐹𝑐 sin(𝜑𝑠𝑝 + 𝜑𝑐𝑡 ) sin(𝜑𝑠𝑝)</p> Signup and view all the answers

    In the context of cutting, what does the shear velocity relate to?

    <p>Shear stress</p> Signup and view all the answers

    What does the formula 𝐹𝑜 [ tan(ɸₖ) − sin(ɸₛ) ] represent according to the text?

    <p>Shear force</p> Signup and view all the answers

    How is the shear plane area calculated based on the information provided?

    <p>[ tan(ɸₖ) − sin(ɸₛ) ] / 𝐹ₒ = 𝐴</p> Signup and view all the answers

    What is the expression for the chip compression ratio based on the content provided?

    <p>[ tan(ɸₖ) − sin(ɸₛ) ] / 𝐹ₒ = 𝐴</p> Signup and view all the answers

    What are some of the performance issues associated with a machined surface with poor texture?

    <p>Increased wear of sliding parts and reduced corrosion resistance</p> Signup and view all the answers

    What is primarily concerned with the effects of a manufacturing process below the visible surface of a machined part?

    <p>Surface integrity</p> Signup and view all the answers

    Which zone experiences mechanical, metallurgical, chemical, thermal, and electrical alterations in metal cutting processes?

    <p>Shear zone</p> Signup and view all the answers

    Where does the instantaneous shear plane lie in metal cutting processes?

    <p>Between the chip and the workpiece</p> Signup and view all the answers

    What happens to most of the temperature rise generated during metal cutting according to equation (2.38)?

    <p>The chip absorbs most of the heat</p> Signup and view all the answers

    What is one consequence of undesirable levels of heat generation and cutting forces in machining processes?

    <p>Distorting residual stress</p> Signup and view all the answers

    Study Notes

    Temperature at the Shear Plane

    • The temperature at the shear plane can be calculated using the equation: 𝑇𝑠𝑝 = 𝐹𝑠𝑠𝑝 𝑉𝑠𝑝 𝑚̇𝑐𝑝𝑐 + 𝑇𝑎
    • The friction power dissipated at the chip-rake face interface is given by: 𝑃𝑟𝑓 = 𝐹𝑓𝑟𝑓 𝑉𝑐ℎ
    • The heat generation rate at the chip-rake face interface is: 𝑃𝑟𝑓 = 𝑚̇𝑐𝑝 𝑐∆𝑇𝑐ℎ

    Power Consumption in Cutting Process

    • The total power drawn from the spindle motor for the cutting process is: 𝑃𝑠𝑚 = 𝐹𝑡 𝑉𝑡 = 𝑃𝑠𝑝 + 𝑃𝑟𝑓 + 𝑃𝑚𝑠 + 𝑃𝑚𝑐
    • The power terms 𝑃𝑚𝑠 and 𝑃𝑚𝑐 are negligible, so 𝑃𝑠𝑚 ≈ 𝑃𝑠𝑝 + 𝑃𝑟𝑓
    • The equation for 𝑃𝑠𝑚 can be rewritten as: 𝑃𝑠𝑚 ≈ 𝜌𝑤ℎ𝑉𝑡 𝑐[(𝑇𝑠𝑝 − 𝑇𝑎) + ∆𝑇𝑐ℎ]

    Tool Life and Surface Integrity

    • The tool life is jeopardized by undesirable levels of heat generation and cutting forces
    • Instantaneous shear plane lies in the boundary between the chip and the workpiece and becomes part of the chip just after the instant
    • The friction power 𝑃𝑟𝑓 is converted to thermal energy, causing the temperature of the tool and chip to rise
    • The overall effect of the shearing process is that the material that would have been within the triangle 𝑂𝐵𝐵 ′1 is recreated within the triangle 𝑂′ 𝐵 ′2 𝐵 ′4 as a result of plane strain conditions

    Shear Strain and Shear Plane Area

    • The shear strain is given by: 𝛾𝑠 = 𝛾𝑠 = 1 ̂ ′2 tan(𝜑𝑠𝑝) cos(𝜑𝑟𝑓) sin(𝜑𝑠𝑝) cos(𝜑𝑠𝑝 − 𝜑𝑟𝑓)
    • The shear plane area is given by: ℎ 𝐴𝑠𝑝 = sin(𝜑𝑠𝑝) 𝑤
    • The shear stress (assumed constant over the shear plane) is given by: 𝜏𝑠𝑠𝑝 = 𝐹𝑠𝑠𝑝 sin(𝜑𝑠𝑝) = 𝐴𝑠𝑝 ℎ𝑤 𝐹𝑠𝑠𝑝

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    Description

    Understand how an increase in tangential velocity leads to a rise in friction power, resulting in higher temperatures that can soften and weaken the tool's rake face. Learn about the potential consequences of accelerated wear, breakage, and material diffusion in cutting tools during machining processes.

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