BACKWARD ANGLE STRUCTURE IN THE 20Ne+28Si QUASIELASTIC SCATTERING

New data for the quasielastic scattering of 20 Ne from a 28 Si target at incident energies of 42.5 MeV and 52.3 MeV and for the 28 Si (20 Ne , 24 Mg )24 Mg , 28 Si (20 Ne , 16 O )32S and 28 Si (20 Ne , 12 C )36 Ar transfer reactions at 52.3 MeV are reported. Oscillations are observed in the backward angle quasielastic scattering data at 52.3 MeV and the 28 Si (20 Ne , 12 C )36 Ar transfer cross-sections are of the same magnitude as those for single-α stripping. Coupled reaction channels (CRC) calculations are unable to describe either the quasielastic or the 28 Si (20 Ne , 12 C )36 Ar transfer data assuming a sequential α transfer process with α-particle form factors from the literature. The addition of direct 8 Be cluster transfer can provide a reasonable description of both data sets, but only with much larger spectroscopic factors than suggested by simple structure calculations or the large 8 Be emission thresholds of 20 Ne , 28 Si and 36 Ar , suggesting that the observed structure is of resonance-like origin. An optical model analysis of the quasielastic scattering data is also reported.

Research on the Vibration Tapping Performance of Particle Reinforced Aluminum Matrix Composites

The vibration tapping technology has been employed with success on some difficult-to-machine material such as titanium alloy, hardened steel and so on. However, there are very few studies on the application of the torsion vibration tapping in particle reinforced aluminum. The tapping performance of small size thread holes in particle reinforced aluminum matrix composites Al2O3p/Al and SiCp/Al during common tapping and low-frequency vibration tapping using high speed steal(HSS) machine-used taps is researched experimentally in this work. The influence of vibration parameters, e.g. cutting speed V, net forward angle of each stroke LT and times of repeat cutting Q on tapping torque, tool wear, tool life and quality of thread holes is investigated during the experimentation. The results show that the common vibration tapping with small amplitude, relatively high frequency and a lot of repeat cutting times suit to tap the Al2O3p/Al, whereas the step vibration tapping with large amplitude, relatively low frequency and a few repeat cutting times suit to tap the SiCp/Al due to difference performance of the two kinds of material. The influence of Q and LT on the quality of thread holes, tapping torque and tool life is sensitive on the Al2O3p/Al, whereas the influence of V and Q on the quality of thread holes, tool wear and tool life is sensitive on the SiCp/Al. Furthermore, the optimum vibration parameter in the Al2O3p/Al by dry cutting is cutting speed of 400r/min, net forward angle of each stroke of 1.5°, backward angle of each stroke of 45°. The optimum vibration parameter in SiCp/Al by dry cutting is cutting speed of 220r/min, net forward angle of each stroke of 420°, backward angle of each stroke of 430°. From the test results and micrographs, it was observed that the particle could be fractured on the surface finish on tapping processing. The proper vibration tapping parameter can void the adhesion in the tap flute, decrease the tapping torque, improve the quality of thread hole and prolong the tap life.