Problem 4: a) What are the principal stresses? Show your calculations and assumptions. b) Use the Leak Before Break--met

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Problem 4 A What Are The Principal Stresses Show Your Calculations And Assumptions B Use The Leak Before Break Met 1 (102.5 KiB) Viewed 9 times

Problem 4: a) What are the principal stresses? Show your calculations and assumptions. b) Use the Leak Before Break--methodology to evaluate safe operation (avoid unstable brittle fracture) of the following tank given two material options (plain carbon and high strength steel). Show your assumptions and calculations. c) Is it a fair assumption that the two steels have the same fracture toughness? Explain. d) What NDT-method has (most likely) been used to determine the dimensions of the crack? Explain. e) Given the initial crack dimensions are correct, design a pressure test to assess the materials fracture toughness. It is identified a crack on the inside in a pressure vessel, containing nitrogen at a pressure of 3 MPa. Dimensions of the vessel, shown in Figure 4: Diameter (D) is 2 m, cylindrical part is 4 m long, and wall thickness (t) is 10 mm. 2c t Figure 4: Pressure vessel Configuration of crack. The crack is surface penetrating on the inside and longitudinal (horizontal) in direction with a length (2c) of 18 mm and a depth (a) of 4 mm. The crack is evaluated to grow due fatigue given pressure cycles in the vessel. The crack length/depth-ratio is evaluated to be constant during the fatigue growth. Material options in vessel: 1. Plain carbon steel: oy = 270 MPa 2. High strength steel: oy = 360 MPa The fracture toughness Kic is 120 MPavm for both steels. Given: Use stress intensity factor for a semi-infinite body. Rapture of rest surface ligament gives a crack of depth (2a) equal to the length of the "not wall thickness penetrating crack". The Mises-stresses should not be larger than yield stress for the steel given Material and Safety class factors are both 1.