Materials Science: 10 Things Every Engineer Should Know: Thing 5

In a laboratory creep experiment at 1,000 °C, a steady-state creep rate of 5 x 10-1 % per hour is obtained for a metal alloy. The activation for creep in this system is known to be 200 kJ/mol. We can then predict that the creep rate at a service temperature of 600 °C will be ______________. (We can assume the stress on the sample in the laboratory experiment is the same as at the service temperature.)

8.68

A powerful use of the Arrhenius relationship is to measure creep data at low temperatures and then extrapolate the data to high temperatures, allowing us to predict the performance there.

False

We added comments about polymers because their weak, secondary bonding between long chain molecules causes them to exhibit creep deformation at relatively low temperatures.

True

In the simplest sense, the creep test is essentially a tensile test done at a high temperature under ____________ load.

a fixed

For high temperature creep deformation in ceramic materials, a common mechanism is ______________.

grain boundary sliding

"Creep" deformation describes the behavior of materials being used at high temperatures under high pressures over _____________ time periods.

long

A linear portion of the strain versus time plot corresponds to the ______________ stage of the overall creep curve.

secondary

The strain rate in the ______________ stage of the creep test is analyzed using the Arrhenius equation, analogous to our previous discussion of the diffusion coefficient.

secondary