Tutorial_3 Failure of Materials in Service

KQA7007 Failure of Materials in Service KXGB6301/KXGM6310 Fatigue Failure and Failure Analysis Department of Mechanical Engineering, University of Malaya

Instructor: Assoc. Prof. Dr. Andri Andriyana

AL 3: Fracture of Cracked Members

Contents Problem 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

2

KQA7007 Failure of Materials in Service KXGB6301/KXGM6310 Fatigue Failure and Failure Analysis

AL 3: Fracture of Cracked Members

Problem 1 A cylindrical pressure vessel has an inner diameter of 150 mm and a wall thickness of 5 mm. It contains a pressure of 20 MPa. To ensure safety during the service, the following requirements are imposed in the pressure vessel design: 1. The safety factor against yielding must be at least 2 according to the maximum shear stress criterion (Tresca criterion). 2. The leak-before-break criterion must be met with a safety factor of at least 9 on the crack length. For this design, two materials are investigated: Material Metal A Metal B

σy (MPa) 1740 760

√ KIC (MPa· m) 65 187

Of the two metals above, which one is the suitable candidate with respect to the above requirements? Justify your choice. Assume geometrical factor Y = 1.

Assoc. Prof. Dr. A. Andriyana

Page 2 of 2