Modeling and validation of residual stress distribution in an HSLA-100 disk

The residual stress distribution in a GTA spot we 100 steel disk was analyzed using thermomechanically uncoupled and semi-coupled finite element (FE) formulations and measured with the neutron diffraction technique. The computations used temperature-dependent the and mechanical properties of the base metal. The thermal analysis was based on the heat conduction formulation with the Gaussian heat input from the arc. The semi-coupled approach is an effective alternative to the fully coupled approach in which the incompatibility in the thermal and mechanical time increments often leads to numerical convergence difficulties. Convergence was achieved in the semi-coupled approach where a larger time increment for temperature calculation was automatically divided into some sub-intervals for the thermal stress calculation. The temperature, deformation configurations, and state variables were updated at the end of the temperature increment. The predictions from the FE models are in very good agreement with the neutron measurement results in the far heat-affected zone (HAZ) and in the base metal. Both models over-predicted the residual stress field in the fusion zone and near HAZ as measured by the neutron diffraction method. The discrepancy could be attributed to the changes in microstructures and material properties in the HAZ and fusion zone due to phase transformations during the welding thermal cycle. The formation of cracks in the fusion zone is another factor that possibly contributes to the lower measured residual stress values

Magnetic trapping of ultracold neutrons

Three-dimensional magnetic confinement of neutrons is reported. Neutrons are loaded into an Ioffe-type superconducting magnetic trap through inelastic scattering of cold neutrons with 4He. Scattered neutrons with sufficiently low energy and in the appropriate spin state are confined by the magnetic field until they decay. The electron resulting from neutron decay produces scintillations in the liquid helium bath that results in a pulse of extreme ultraviolet light. This light is frequency downconverted to the visible and detected. Results are presented in which 500 +/- 155 neutrons are magnetically trapped in each loading cycle, consistent with theoretical predictions. The lifetime of the observed signal, 660 s +290/-170 s, is consistent with the neutron beta-decay lifetime.Comment: 17 pages, 18 figures, accepted for publication in Physical Review

Polycapillary optics based neutron focusing for small sample neutron crystallography.

This work presents preliminary measurements designed to explore a new approach to neutron diffraction that is somewhat analogous to the pseudo-Laue technique, except that instead of using a broad energy (wavelength) bandwidth it uses a broad angular bandwidth. We have used a polycapillary focusing optic to focus neutrons from a monochromatic beam (using the BT-8 spectrometer on the NIST research reactor) and from a polychromatic beam at a pulsed spallation source (the Intense Pulsed Neutron Source, IPNS at Argonne National Laboratory) into a small, intense spot and have carried out preliminary diffraction measurements. Using the single crystal diffraction (SCD) facility on IPNS, diffraction of a 3{sup o} convergent beam from an alpha quartz crystal showed six diffraction beams in the 1-5{angstrom} wavelength bandwidth transmitted by the optic. The diffraction spots showed an intensity gain of 5.8 {+-} 0.9 compared to a direct beam diffracting from the same sample volume as that illuminated by the convergent beam

Comparison of biogas yield from three types of silage: maize, lucerne and grass silage

W pracy przedstawiono wyniki analiz fizykochemicznych oraz fermentacji beztlenowej trzech popularnych kiszonek rolniczych, a dokładnie kiszonki z kukurydzy, lucerny i traw. Kiszonki poddano fermentacji w formie rozdrobnionej i nierozdrobnionej. Istotne jest, ze fermentacja prowadzona była zgodnie z niemiecką normą DIN 38414-S8. W ten sposób określono potencjał biogazowy trzech wspomnianych kiszonek. Wskazano także trudności jakie mogą się pojawić przy stosowaniu jednej z kiszonek do produkcji biogazu.The study presents the results of physical and chemical analysis and anaerobic digestion of three common agricultural silages, particularly maize silage, lucerne and grass silage. The silage was subjected to fermentation in a fragmented and a non-fragmented form. It is essential that the fermentation process was carried out according to a German standard DIN 38414-S8. Biogas potential of the said silage was determined in this way. Difficulties, which may occur during the use of one of the silages for biogas production, were determined

LOW FREQUENCY MOTIONS OF H2OH_{2}O MOLECULES IN WATER, ICE AND CRYSTALLINE SALTS.

The authors are guests at the Army Materials Research Agency, Watertown these equilibria can be shifted by changes in temperature, solvent, or substituent groups on the ligand. The spectroscopic and laser implications of these effects will be discussed., Massachusetts.Author Institution: U. S. Army Materials Research AgencyThe motions of $H_{2}O$ molecules in water, ice or crystalline salts, in a frequency range between 20 and $1000 cm^{-1}$ can be detected by studying the energy distribution, after single scattering events, of a beam of low energy incident neutrons (0.005 eV or $40 cm^{-1}$). In the present experiment neutrons gain energy from transitions occurring between thermally populated energy levels corresponding to a given motion in the sample. All possible librational and translational motions are expected to be observed for each species of $H_{2}O$ molecule in the sample. A systematic investigation was undertaken to study the effects of the degree of coordination and the strength of hydrogen bonding on the frequencies of molecular motion of $H_{2}O$ molecules in various configurations. Due to the short interaction time between neutrons and nuclei ($10^{-12}$ sec), the spectra of water and ice are similar, the differences in the frequencies of the peaks being attributed to changes in the degree and strength of bondings of $H_{2}O$ molecules in both samples. In ice, an assignment of the peaks in the neutron spectrum below $200 cm^{-1}$ was attempted in terms of the calculated optical (nine) and acoustical (three) translational modes of vibration. In water the existence of ``clusters'' containing several species of $H_{2}O$ molecules should be considered in the interpretation of the spectrum. The three librational modes were found to be better resolved in the neutron spectrum obtained from an $H_{2}O-D_{2}O$ mixture than in the case of pure water. The neutron spectra of $(KCOO)_{2} H_{2}O, LiSO_{4} H_{2}O, Ba (C10_{3})_{2}\cdot H_{2}O, KF\cdot 2H_{2}O, CuSO_{4}\cdot 5H_{2}O$ and of a series of chloride hexahydrates (Ba, Sr, Ca, Mg, Al, Cr, Ni, Co) and $FeCl_{2}\cdot 4H_{2}O$ will be presented together with tentative frequency assignments for the various molecular motions of $H_{2}O$, taking into account the crystal structures of these materials and the results of Raman and infrared studies

NEUTRON INELASTIC SCATTERING FROM SOLID HCl

$^{1}$K. Shimaoka, et al., J. Phys. Soc. Japan 27, 1078 (1969). $^{2}$S. F. Trevino, Applied Spectroscopy 22, 659 (1968). Gault, Trevino and Prask were guests at AMMRC, Watertown, Mass. 02172. Gault was an NRC-FRL Postdoctoral Research Associate.""Author Institution: Explosives Laboratory, Feltman Research LaboratoriesHigh resolution neutron inelastic scattering spectra in the region below $250 cm^{-1}$ have been obtained from solid HCl at temperatures corresponding to the low temperature ferroelectric phase, the high temperature disordered phase and the recently $reported^{1}$ (120$^\circ K$--98.4$^\circ K$) intermediate phase. These data were obtained utilizing a time-of-flight spectrometer with a crystal monochromator. The resolution of this instrument is sufficient to enable previously unresolved structure to be observed. The low temperature phase data are compared to cross-sections calculated by using a full lattice dynamical $model^{2}$ and good agreement is obtained