<p>In this dissertation, we first used
high-speed X-ray phase contrast imaging and infrared thermal imaging techniques
to study the formation processes of adiabatic shear bands in aluminum 7075-T6
and 6061-T6 alloys. A modified compression Kolsky bar setup was developed to
apply the dynamic loading. A flat hat-shaped specimen design was adopted for
generating the shear bands at the designated locations. Experimental results
show that 7075-T6 exhibits less ductility and a narrower shear band than
6061-T6. Maximum temperatures of 720 K and 770 K were locally determined within
the shear band zones for 7075-T6 and 6061-T6 respectively. This local high
temperature zone and the resulting thermal instability were found to relate to
the shear band formation in these aluminum alloys. Secondly, a high-speed laser
phosphorescence thermal imaging technique is developed and integrated with the
compression Kolsky bar setup. The temperature field measurement during dynamic
loading are performed at 100 – 200 kHz frame rate with a spatial resolution of
13 µm/pixel. The
dynamic compression of copper shows 312 K temperature rise among the material
surface. Experiments with thermocouple are also conducted and the results
verifies the laser measurement. In the dynamic shear of aluminums, the
temperature evolution during adiabatic shear band formation was observed and
the results are compared with infrared measurements. The shear band was found
forming at approximately 400 K and 440 K for 7075-T6 and 6061-T6, respectively,
while the maximum temperature is measured as 650 K for 7075-T6 and 800 K for
6061-T6. Although the maximum temperature agrees with the infrared results, thermal
softening is not considered as the main cause of the ASB formation due to the
low temperature when the shear band forms.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/10711244 |
| Date | 22 November 2019 |
| Creators | Yizhou Nie (7909019) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Dynamic_Deformation_and_Temperature_Field_Measurement_of_Metallic_Materials/10711244 |
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