One-Dimensional Strain Initiated by Rapid Compaction of a Heterogenous Granular Mixture Consisting of Cu, Fe, SiO2, C, MoS2, and Sn
Date of Award
Master of Science (MS)
The dynamic compaction of metal powders is of great interest to the metallurgical and military communities. The compaction of a heterogeneous granular mixture consisting of copper, iron, silica, graphite, molybdenum-disulde, and tin predominately used in aviation break-pad creation is presented. The initial density of the material was on average 2.756 g/cm3 . The research also required developing a working projectile velocity measurement system and a proper target assembly for pressure measurements. Manganin gages were used to record the shock wave transit time and the pressure of the transmitted waveform into the powder mixture. An impedance matching technique was utilized to determine the particle velocity at the powder-impact plate interface and the shock velocity was determined from the measured data. The shock velocity and particle velocity were plotted to develop a linear equation of state, Us = SUp + C0. The linear equation of state was determined to have a Hugoniot slope of S = 0.3949 ± 1.2869 and a bulk sound speed of C0 = 0.552 ± 0.188(m/s). The equation of state was then employed in bulk one-dimensional computer simulations to compare to the waveform obtained from the pressure measurement system. The post-impact samples were investigated using a scanning electron microscope and electron dispersive spectroscopy to compare the microstructure of the dynamically compacted samples to the commercially manufactured pressed and sintered sample. The bulk scale simulations proved to recreate the pressure waveform from the pressure measurement system. It was also found that the dynamically compressed samples had minimal evidence of sintered grains, but had significant lateral fractures resulting from release.