a Figure 1 shows four distinct fracture surface micrographs taken at different magnifications Discuss the most likely fa

[answerhappygod]

A Figure 1 Shows Four Distinct Fracture Surface Micrographs Taken At Different Magnifications Discuss The Most Likely Fa 1 (68.23 KiB) Viewed 55 times

A Figure 1 Shows Four Distinct Fracture Surface Micrographs Taken At Different Magnifications Discuss The Most Likely Fa 2 (65.42 KiB) Viewed 55 times

A Figure 1 Shows Four Distinct Fracture Surface Micrographs Taken At Different Magnifications Discuss The Most Likely Fa 3 (37.61 KiB) Viewed 55 times

a Figure 1 shows four distinct fracture surface micrographs taken at different magnifications Discuss the most likely failure mechanism in each case (6 marks) 50 m 5 um (b) 20 m 1000 m (C), (0) Figure 1 Scanning electron micrographs of fracture surfaces for Question 1 Suggest with justification which fracture surface among those shown in Figure 1 would be most likely observed in the failure of a ceramic material, (2 marks) Figure 2 (reproduced from Figure 2.40 in Block 2 Part 2) shows the fatigue-crack growth rate for a metallic material. From the graph, estimate the number of cycles it would take to propagate a crack from 3.5mm to 4.2 mm in length for a stress intensity range ak of 30 MPa vm. (4 marks)

10-2 10-2 Region 1 ko da slow crack growth ep d =CAK *****? 104 measured crack growth rate N/mm per cycle 10-5 AK Region 2 power law behaviour Region 3 rapid, unstable crack growth 10 2 10- - 8 10 20 30 40 50 60 80 100 stress intensity factor range SE/MPa Vm Figure 2 Fatigue-crack growth rate for a metallic material for Question 1(6) it. When collecting data to construct a graph such as the one shown in Figure 2. explain why it is important to accurately measure the length of the growing crack (4 marks) c. A thin-walled steel cylindrical pressure vessel with a radius of 10 m and a wall thickness of 40 mm is designed to carry an intemal pressure of 10 MPa. The steel has a fracture toughness of 95 MPaNm and a yield strength of 520 MPa For this material take the exponent in the Paris relationship to be m = 3 and the coefficient to be C= 10-11 Answer the following questions, stating dearty now you obtained each answer. You will need to use the K-calculator and "Fatigue calculator spreadsheets on the DVD or module website. You may wish to consider including copies of the completed spreadsheet calculations in your answers What is the maximum crack length through the wait that the vessel can tolerate when operating at the maximum internal pressure to give a reserve factor of 2.0 on the load? (You will need to use the K-calculator as in Block 2 Part 1. modelling the crack using the Plate in tension-through-thickness edge crack geometry)

llOn inspecting the vessel, a welding defect in the shape of a through-thickness edge crack is discovered and is measured to be 3 mm long. Determine how many pressurising cycles it will take for the crack to grow to the size determined in part) If the vessel is regularly cycled to 80% of its maximum internal pressure (You will need to use the 'Fatigue calculator Use a crack-growth increment of 0.01) (5 marks) i. When the crack has grown to 50 mm the vessel is accidentally subjected to 100 overload cycles equal to 500 MPa. Again using the 'Fatigue calculator determine what length the crack will grow to during these overload cycles. What is the percentage reduction in life due to these overload cycles as compared to the life found in part ()? (5 marks)