ENGINEERING QUESTIONS

ENGINEERING QUESTIONS

  • In closed- die forging process, what are the function of flush? In general, what will happen if there is too little or too much flush?

 

  • During sheet metal forming processes, i.e. bending and deep drawing, the springback is often seen and it needs to be considered in designing the tools and the processes. Please describe the concept of springback, and explain the reasons of causing springback? How will the springback affect the stresses in the part?

 

  • What is heat affected zone (HAZ) in welding process? Please describe it and drew a schematic figure of the HAZ. Sometimes high cycle fatigue cracks initiate in the neighbor out side the HAZ, what can be the cause?

 

  • Work hardening during rolling processes affects the anisotropy of the rolled products. In general, what is the difference of the anisotropy severity between hot rolled and cold rolled products? Please explain why?

 

  • Please briefly describe the friction welding process. Is friction welding fusion welding or solid state welding process? What are its advantages and drawbacks?

 

  • Please briefly describe the sand casting and investment casting processes?

 

  • What is the physical meaning of Taguchi Loss Function? (the equation is given below)

Loss cost= K [(Y – T)]^2 +α^2]

 

Replacement cost

Where K= —————————

(LSL – T)^2

 

  • During a flat rolling process, what are the reasons of causing poor flatness of rolled metal sheets? Please explain two methods for improved flatness of the rolled metal sheets.

 

  • What are the three phases at the liquid and solid interface during an immersion oil quenching process? How will the three phases affect the cooling severity?
  • During an open-die forging (upsetting) process of a cylindrical billet, please explain why does the obtained part geometry have a barrel shape? How to reduce the severity of the barrel shape (more straight)?

 

  • Please explain why is the workpiece surface temperature higher during a grinding process than that of a lathe or milling machining process? Please explain through the cutting tool geometry aspect.

 

 

  • Using a lath machining process as an example, heat is generated from the plastic deformation of the chip and the friction between the workpiece and the cutter. The cutter contact with workpiece, and heat flux flows into the cutter. The temperature change in the cutter generates internal stresses, which may cause stress fatigue. Please explain how will the thermal conductivity, specific heat, and coefficient of thermal expansion of the cutter material affect the stress magnitude in the cutter caused by the heat flux mentioned above?

 

  • In a closed-die forging process, what are the function of a flash?
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