Besides being the topic of lab instructor Dr. Jessica TerBush’s PhD thesis, creep is time-dependent and important to understand when materials are used at temperatures over 50% of their melting point. You don’t want your car engine deforming as you drive down the highway, or your jet engine falling apart mid-flight, after all! In this lab, samples of aluminum are placed inside a furnace and weights are suspended from the bottom of the sample. Tests are done under two conditions, three tests at constant load/stress and three tests at constant temperature. Using the calculated creep rates, students are able to determine the stress exponent and activation energy from the Mukherjee-Bird-Dorn equation, which also allows them to comment on what the active mechanism may be.
- Constant-load creep frame consisting of a clamshell furnace, stainless steel sample fixtures and an aluminum weight hanger
- Linear variable differential transducer (LVDT) to measure displacement
- Various weights
- Water basin for quenching samples
- Analytical balance
- Micrometer head for calibration
- 1100 Aluminum samples, machined into “dogbone” specimens