Project 4: Unixial material response of Zr under dynamic tension
Adviser(s): John Lambros (Professor, Aerospace Engineering)
Project description: Most materials exhibit a significant mechanical property dependence on strain rate (and
temperature). To thoroughly understand material response one needs to investigate, usually
experimentally, its uniaxial stress-strain behavior over several orders of magnitude of strain rate.
Figure 1 shows the compressive stress strain
response rate dependence for zirconium (Zr),
an hcp metal. A number of specialized devices
are needed to span such a large strain rate
regime. The data in Figure 1 have been
obtained using two different types of servohydraulic
load frames and a split Hopkinson
pressure bar (a device designed to probe
material response in the strain rate range of 100
to 10,000 /s).
A second aspect affecting material response is the loading type – compression vs. tension. To date we have studied in detail the response of Zr to compressive loads. However, because of the intricacies of the hcp crystal structure, and the consequent importance of twinning in addition to dislocation slip as a deformation mechanism, the response of Zr in tension is expected to be very different than that in compression. The goal of the present project is to generate a similar dataset as that in Figure 1, but for tensile loading of Zr. To produce dynamic tensile loading we have a tensile split Hopkinson bar.
Student background and expected research activities:
This project will initially involve setting up and calibrating the device, and then performing a series of dynamic (and separately quasi-static) tensile uniaxial loading experiments on Zr.
This project is mainly experimental in nature. A background, and strong interest, in strength of
materials and/or bending theory is needed. Laboratory and/or programming experience is a plus,
although not required. Students after at least their junior year in college would be suitable.
Fig. 1.Compressive response of Zr over
a range of strain rate.
