MIET1068 - Mechanical Design 2
Lectorial Questions
Notes for Questions 01
• For thin walled shells assume the same failure criteria as AS1210 (Tresca)
• Be aware of units, and be consistent! (N, mm, MPa or N, m, Pa)
• 1bar = 105 Pa
Question 01-1
A thin-walled circular cylinder of internal diameter 10m is subjected to a maximum internal pressure of 50bar. Determine its wall thickness, if ηC = 0.8 and ηL = 0.4. Assume that the maximum permissible stress is 300MPa.
Question 01-2
Design a 120mm tank gun barrel to hold expanding gas pressure of 50MPa. A high-quality 10Mn carbon steel is to be used for construction with a factor of safety of 2 .5 against any yielding in the cylinder and a factor of safety of 3 .2 against ultimate collapse. The yield stress of the material is 520MPa.
Question 01-3
Design the wall thickness for an aircraft fuselage of internal diameter 6m, subjected to an internal pressure of 0.5bar. Assume that ηL = 0.48, ηC = 0.5 and σy = 200MPa.
Question 01-4
Assuming that a submarine pressure hull of external diameter 12m, and wall thickness 5cm, can be designed using internal pressure theory, and neglecting failure due to buckling, determine its permissible diving depth for a safety factor of 2. Assume that the density of seawater = 1020kg/m3 , g = 9.81m/s2 , ηL = 0.48, ηC = 0.5 and the yield stress of the material of construction is 400MPa.