Non-contact optical three dimensional liner metrology
We optically captured the "as-built" liner geometry of NTLX (near term liner experiments) for Shiva Star using ultra-precision ranging lasers. We subsequently verified the resulting digitized geometry against the 3D CAD model of the part. The results confirmed that the Liner contours are within designed tolerances but revealed subtle fabrication artifacts that would typically go undetected. These features included centimeters long waviness and saddle and bulge regions of 1 micron or less in magnitude. The laser technology typically provided 10 micron spatial resolution with /spl plusmn/12 nanometer ranging precision. Atlas liners in the future may have to be diamond turned and will have the centimeter wavelength and 100 angstrom amplitude requirements. The advantages of using laser technology are (1) it avoids surface damage that may occur with conventional contact probes and (2) dramatically improves spatial resolution over CMM, capacitance and inductance type probes. Our work is the result of a perceived future need to develop precision, non-contact, liner inspection techniques to verify geometry, characterize machining artifacts and map wall thickness on delicate diamond turned surfaces. Capturing "as-built" geometry in a non-contact way coupled with part-to-CAD verification software tools creates a new metrology competency for MST-7.
Laser Contouring Method for Wall Thickness Metrology on OMEGA Shock Breakout Targets
The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory will attempt to achieve thermonuclear ignition of deuterium-tritium in approximately ten years. Ignition will be achieved by using the 1.8 MJ, 192 laser beam NIF to compress spherical targets containing deuterium-tritium fuel. An important physics issue that is being studied in experiments at the OMEGA laser facility at the University of Rochester is the manner in which laser-induced shocks propagate through target materials, and how target materials absorb and respond to xray radiation pulses. The Omega laser is presently the world most powerful laser with 30KJand 60 laser beams. At Los Alamos we are fabricating targets for these experiments. The metrology of these targets is a critical issue. In this paper, the unique advantages of measuring targets assembled in their ready-to fire physics targets, using dual, active confocal, lasers is described.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME