טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMizrachi Shai
SubjectExperimental Characterization of Transient Temperature
Changes during Dynamic Loading by Means of
Infrared Sensing
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Daniel Rittel


Abstract

During dynamic loading, a significant temperature rise takes place in the specimen due to the conversion of plastic work into heat. For this purpose an infrared optical temperature measuring system was built

The thermoplastic coupling was studied by calculating bdiff and bint. bdiff is the ratio of thermal energy rate to the plastic work rate. bint is the ratio of thermal/mechanical energy. The optical system is set to work with Split Hopkinson Pressure Bar . Both cylindrical specimens and SCS of Aluminum 2024-T4 and pure Iron (a) were used in this study.

The results of the calibration of the system showed that in Aluminum 2024-T4 the change of the specimen diameter and the change of the surface roughness during deformation had a significant influence on the calibration curve.

SCS and cylindrical specimens of Al2024-T4 showed some differences in material thermo-mechanical behaviors. The SCS specimen tended to initiate localized deformation at an earlier stage than the cylindrical specimen. The SCS specimen failure occurred at strain of ε≈0.35 while in cylindrical specimen it occurred at strain of ε≈0.7. In addition we saw shear bands formed in the gauge section of SCS in most of the experiments while in cylindrical specimen the event was not observed.

For pure Fe specimens, bdiff and bint were found to be around 0.5 using cylindrical samples. This observation matched the results of a series of experiments that was done at Caltech, USA.