1. Rocket motor cases may be fabricated as thin walled tubesfrom:
a) Low alloy steel of proof stress 1200 MPa and GC =24 kJ/m measured in sheet of an appropriate thickness, or
b) Maraging steel of proof stress 1800 MPa and GC =24 kJ/m
In a particular application the design code specifies that thedesign stress is StressY/1.5 where Y
is the proof stress. Calculate the minimum defect size
required to give brittle fracture in service for the twomaterials. Comment
on your result. You may take Young’s modulus to be 200 GPa inboth cases.
2)If the fracture stress of a large sheet of
maraging
steel containing a central
crack of length 40 mm is 480 MPa, calculate the fracture stressof a similar
sheet containing a crack of length 100 mm.
