3. Assume the activation energy for the creep of Al2O3 is 425kJ/mol. (a) Predict the creep rate, &, for Al2O3 at 1000°C and 1800 psi applied stress. (See Table 6.12 for data at 1300°C and 1800psi.) (b) Calculate the lifetime of an furnace tube at 1000°C and 1800 psi if 1% total strain is permissible. ( = 2.7x10-6/hr for Al2O3 at 1300°C and 1800psi.)

A hypothetical metal alloy has a grain diameter of 2.4 × 10-2 mm. After a heat treatment at 575°C for 500 min, the grain diameter has increased to 5.6 × 10-2 mm. Compute the time required for a specimen of this same material (i.e., do = 2.4 × 10-² mm) to achieve a grain diameter of 5.5 x 10-2 mm while being heated at 575°C. Assume the n grain diameter exponent has a value of 2.2. i min

Ordinary sheets of borosilicate glass are tested in bending, and are found to fracture at an average stress of 72 MPa. After thermal tempering, the stress at failure increases by 90%. What are the sign and magnitude of the stress induced in the glass by the tempering operation?

(a) An AISI steel plate has width W = 30 cm and a central crack with size of 3 mm. The plate is under a uniform stress. Find the maximum value of the stress is KIc = 50 MPa m1/2. (b) If the part has to operate at a stress of 1,500 MPa, compute the maximum crack size that the plate can have.

Problem#3: You need to design a metallic glass for use in industry. The glass transition temperature of the metallic glass is 250°C. While in use, the sample will be subjected to a permanent tensile stress for tuse=6 years and at a temperature of Tuse=230°C. You need to do the necessary creep experiment in the lab to predict the performance of this material by applying the same stress at different temperature and different time. The creep test will be carried out for tiab=6 hours. At what temperature, Tlab, can this test be performed in the lab under the same tensile stress? [Hint: Use WLF and VFT equations for two cases: 1) Tref=Tg =250 °C and 2) Tr=260 °C.]

A 3105 aluminum plate is reduced from 4.38 cm to 2.88 cm. Determine the final properties of the plate. See attached figure

A copper sample exhibits work-hardening described by where σ0 = 50 MPa, n = 0.5, K = 500 MPa. Calculate the temperature rise when the sample is deformed up to a strain of 0.2. Assume that the conversion factor is 1.0, and given: density = 8.9 g/cm3; heat capacity = 360 J/kg K

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.).

Derive an equation that shows the change in strain over time using the Maxwell Viscoelastic Model. It should look linear.