5. Combined Thermo-Mechanical Stress

Try these first

1. 1.

   Define thermal stress.

   Hint

   Think about what happens to materials as they heat up.

2. 2.

   What is total stress in a pressure vessel?

   Hint

   Consider what two types of stresses we discussed.

3. 3.

   What combined stresses must be considered in pressure vessel design?

   • Thermal Stress Only
   • Mechanical Stress Only
   • Both Thermal and Mechanical Stress

   Hint

   Think about what can happen when a vessel is heated and pressurized.

4. 4.

   True or False: Thermal stress can be calculated using σ_thermal = EαΔT.

   • True
   • False

   Hint

   Recall the variables involved in the thermal stress formula.

5. 5.

   A pressure vessel is subjected to 300°C with an internal pressure of 10 MPa. Calculate the thermal stress if E = 200 GPa and α = 18 × 10^-6 /°C. Assume ΔT = 300°C.

   Hint

   Break down the problem by calculating thermal stress separately first.

6. 6.

   Evaluate how increasing the internal temperature affects the safety of a pressure vessel designed to hold 15 MPa at 150°C. Discuss the design considerations needed for a rise to 300°C.

   Hint

   Think about how materials have limits and how increasing temperature affects material properties.