30 Which one of the following statements is correct A Activa

30. Which one of the following statements is correct? A. Activation energy is higher in grain boundary diffusion compared to that of volume diffusion B. Activation energy is higher in surface diffusion compared to that of volume diffusion c. Activation energy is higher in grain boundary diffusion compared to that of surface diffusion D. Activation energy is lowest in surface diffusion diffusion followed by grain boundary diffusion and volume diffusion. Given the following data from a tensile test answer questions 31-36 The following data were collected from a 20 mm diameter test specimen of a ductile cast iron (ee 40.00 mm): Load Displacement Engineering Engineering True True Suess (mm) Stress (MPa) strain MPa) 0.0000 25,000 0.0185 50,000 0.0370 75.000 0.0555 90,000 0.200 105,000 0.60 120.000 1.56 131.000 4.00 0000 0006 Strain (mm/mml 125.000 7.52 After fracture, the total length was 47 42 mm and the diameter was 18.35 mm. 31. Yield strength of the magnesium sample is A. 85 MPa C. 240 MPa D. 300 MPa B. 186 MPa 32. Modulus of Elasticity of the magnesium sample is A. 44.8 GPa B. 172 GPa C. 235 GPa D. 100 GPa 33. Percentage of Elongation of the magnesium sample is A 18.55% D. 4.3% B.14.3% 34. Percentage of Reduction in Area of the magnesium sample is B 15.8% C 18.7% D. 4.3% 35. Ultimate tensile strength of the magnesium sample is

Solution

30.B

31.B

32.A

33.D

34.C

35.B

36.A

37.D

38.C

39.C

40.A