411 research outputs found
Test Bed for Quantitative NDE
The ARPA/AFML Interdisciplinary Program for Quantitative Flaw Definition has demonstrated a number of new techniques for quantitatively sizing flaws, as are reported elsewhere in these proceedings. The next step required in the transfer of this technology to the production line is the assembly and demonstration of these techniques in a single, integrated measurement system. The technical plan of a recently initiated test bed program, which will serve this function, is described here
Dependence of the Accuracy of the Born Inversion on Noise and Bandwidth
The Born Inversions are a set of techniques for reconstructing the shape of a flaw based on the scattering of ultrasound from the flaw. One technique is the one-dimensional Born Inversion, which estimates the radius of a flaw in one direction based on one pulse-echo (i.e., backscattering) measurement in that direction. The robustness of this technique with respect to limitations on the available bandwidth and with respect to the presence of noise in the data have been investigated. The Born Inversion requires a bandwidth sufficient to include at least the range 0.5 \u3c ka \u3c 2 to give accurate estimates. The estimates continue to be accurate even when the amount of noise energy is comparable to the amount of flaw signal energy in the measurement
Test Bed for Quantitative NDE
The ARPA/AFML Interdisciplinary Program for Quantitative Flaw Definition has demonstrated a number of new techniques for quantitatively sizing flaws, as are reported elsewhere in these proceedings. This paper describes the progress that has been made during the past year on a test bed program to assemble and demonstrate these techniques in a single integrated measurement system that will extend them from the idealized geometries that have been considered thus far to geometries that are a better approximation to those that are found in real parts. The basic system consists of a Data General Eclipse S/200 Minicomputer, a multiaxis microprocessor controller, a Biomation A/D converter, an immersion tank, and a contour following system with six degrees of freedom. The operation of the mechanical system with regard to its accuracy and repeatability will be described. In addition, a review of the conceptual design of the test bed system and experimental results for a number of different flaw geometries will be included. The Test Bed includes a piezoelectric array transducer and associated electronics. The array system will be used both for the imaging of flaws and the gathering of scattering data to use in other flaw characterization algorithms. The success of this portion of the program depends to a large extent on the availability of a suitable array transducer. Some difficulty has been met in obtaining such a transducer and the system design has been slightly modified as a result. The modified system will be described along with a review of the electronic system and an update on its current status. The extended data gathering capability of the system has been demonstrated with several diffusion bonded samples containing spherical and spheroidal voids. The noise associated with these signals is chiefly due. to the grain scattering and varies in amplitude over a wide range. The effects of this noise on the accuracy of the Inverse Born Approximation has been analyzed and the results will be summarized
Test Bed for Quantitative NDE
The ARPA/AFML Interdisciplinary Program for Quantitative Flaw Definition has demonstrated a number of new techniques for quantitatively sizing flaws, as are reported elsewhere in these proceedings. This paper describes a test bed program to assemble and demonstrate these techniques in a single integrated measurement system that will extend them from the idealized geometries that have been considered thus far to geometries that are a better approximation to those that are found in real parts. Included are discussions of the conceptual design of the system, the detailed design and construction of specific modules, and preliminary experimental results. The basic system consists of a Data General Eclipse S/200 minicomputer, a multi-axis microprocessor controller, a Biomation A/D converter, an immersion tank, and a contour following system with six degrees of freedom. A detailed description of the operation of the various components of the system will be given. Included are discussions of the conceptual design of the system, detailed design and construction of specific modules, and preliminary experimental results
The Atacama Cosmology Telescope: Two-Season ACTPol Spectra and Parameters
We present the temperature and polarization angular power spectra measured by
the Atacama Cosmology Telescope Polarimeter (ACTPol). We analyze night-time
data collected during 2013-14 using two detector arrays at 149 GHz, from 548
deg of sky on the celestial equator. We use these spectra, and the spectra
measured with the MBAC camera on ACT from 2008-10, in combination with Planck
and WMAP data to estimate cosmological parameters from the temperature,
polarization, and temperature-polarization cross-correlations. We find the new
ACTPol data to be consistent with the LCDM model. The ACTPol
temperature-polarization cross-spectrum now provides stronger constraints on
multiple parameters than the ACTPol temperature spectrum, including the baryon
density, the acoustic peak angular scale, and the derived Hubble constant.
Adding the new data to planck temperature data tightens the limits on damping
tail parameters, for example reducing the joint uncertainty on the number of
neutrino species and the primordial helium fraction by 20%.Comment: 23 pages, 25 figure
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