Investigation of Cable Insulation and Mechanical Properties of Niobium-Tin Composite

As a part of the Fermilab high field Nb{sub 3}Sn dipole development program, various issues of magnet technology are being investigated. In cable insulation development, S-2 fiber glass sleeve and a new ceramic insulation developed by Composite Technology Development Inc. (CTD) were studied as a possible candidates. For each type of insulation, Nb{sub 3}Sn ten-stack samples were reacted and then vacuum impregnated with epoxy. Measurements of modulus of elasticity and Poisson�s ratio under compression were made at room temperature and at 4.2 K. For comparison, an epoxy impregnated NbTi composite was also tested

The Effect of a Laser Beam on Chip Formation during Machining of Ti6Al4V Alloy

The effect of the laser beam on chip formation when machining Ti6Al4V alloy has been investigated at different cutting speeds and laser powers. The characteristics of the segmented chip produced by laser-assisted machining (LAM) in terms of the tooth depth and tooth spacing were strongly dependent on the cutting speed and laser power. Two types of segmented chip formation processes were observed, one at low and the other at high cutting speeds with a continuous chip occurring between these two types of segmented chips. The critical cutting speed at which the transition from the sharp, segmented chip to the continuous chip occurred increased with laser power. To obtain the continuous chip, plastic deformation at the shear zone to match the deformation strain introduced by the cutting tool is required. This can be achieved by laser heating the material in front of the cutting tool. A physical model is proposed to explain qualitatively the chip segmentation in conventional machining and the continuous chip transition at high cutting speed with the application of a laser beam