Calculate the activation energy in j/mol for the creep of an alloy having the steady state creep behavior shown below. Use the data taken at stress level 300MPa and the temperature of 650C and 730C. Assume the stress component n is independent of the temperature.

In a laboratory creep experiment at 1273K, a steady-state creep rate of 5 ××10-1 %, per hour is obtained in a metal alloy. The creep mechanism for this alloy is known to be dislocation climb with an activation energy of 200 kJ>mol. Predict the service temperature in (°C) for a creep rate of 8.68 ×10-5 %, per hour. (Assume that the laboratory experiment duplicated the service stress.)

Using the equation Kica, plot the fracture stress (MPa) for aluminum alloy 7075-T651 versus surface crack size a (mm) for a values from 0.2 mm to 2.0 mm. What is the minimum size surface crack that will cause catastrophic failure?

The yield strength for an alloy that has an average grain diameter of 4.6 x 10-2 mm is 105 MPa. At a grain diameter of 7.7 × 103 mm, the yield strength increases to 248 MPa. At what grain diameter, in mm, will the yield strength be 234 MPa? d = i mm

Calculate the activation energy in J/mol for creep for an alloy having the steady state creep behavior shown in the figure. Use the data taken at stress level of 300MPa and temperature of 650C and 730C. Assume that the stress component n is independent of the temperature.

Suppose that a wing component on an aircraft is fabri- cated from an aluminum alloy that has a plane-strain fracture toughness of 26.0 MPa Vm (23.7 ksi Vin.). It has been determined that fracture results at a stress of 112 MPa (16,240 psi) when the maximum internal crack length is 8.6 mm (0.34 in.). For this same component and alloy, compute the stress level at which fracture will occur for a critical internal crack length of 6.0 mm (0.24 in.).