Laser-Induced Spall Of Aluminum And Aluminum Alloys At High Strain Rates

We conducted laser-induced spall experiments aimed at studying how a material's microstructure affects the tensile fracture characteristics at high strain rates (> 10(6) s(-1)). We used the Z-Beamlet Laser at Sandia National Laboratory to drive shocks and to measure the spall strength of aluminum targets with various microstructures. The targets were recrystallized, high-purity aluminum (Al-HP RX), recrystallized aluminum + 3 wt.% magnesium (Al-3Mg RX), and cold-worked aluminum + 3 wt.% magnesium (Al-3Mg CW). The Al-3Mg RX and Al-3Mg CW are used to explore the roles that solid-solution alloying and cold-work strengthening play in the spall process. Using a line-VISAR (Velocity Interferometer System for Any Reflector) and analysis of recovered samples, we were able to measure spall strength and determine failure morphology in these targets. We find that the spall strength is highest for Al-HP RX. Analysis reveals that material grain size plays a vital role in the fracture morphology and spall strength results.Mechanical Engineerin

Relationship between Rheological Behaviour and Final Structure of Al

Using rheological parameters of ceramic suspensions, it is possible to taylor the structure of the ceramic foams produced by replica. This method consists in the impregnation of a polymeric flexible template (polyurethane foam) with a ceramic suspension (slurry) containing the appropriate additives, followed by burning out organic compounds and additives and sintering the ceramic structure. In this work, ceramic foams were produced by the replica method from Al2O3 and 3% Y2O3-ZrO2. Rheological parameters of the ceramic suspensions were investigated to improve the mechanical performance of final structures. Different types and quantities of raw materials were combined in order to select the formulations for ceramic foams. The parameters that have a significant influence on the process are the binder type and the amount of solids. Significant changes on the hysteresis area of the suspensions resulted in a lower density of macrodefects in the material. Likewise, when the shear rate viscosity is enhanced, the thickness of the struts increased proportionally. Lastly, when the hysteresis area magnitude and the ceramic thickness increased, the material with higher uniformity was internally densified, and the stress concentration of the internal defects was smoothe

Effects of Increasing Levels of Copper from Either CuSO4 or Combinations of CuSO4 and a Cu-Amino Acid Complex on Growth Performance, Carcass Characteristics, and Economics of Finishing Pigs

A total of 1,089 pigs (PIC 280 ×1050; initially 82.2 lb) were used in a 105-d experiment to determine the effects of increasing added Cu from either CuSO4 alone or a 50/50 blend of CuSO4 and Cu-AA (Availa®-Cu, Zinpro Corporation, Eden Prairie, MN) on growth performance, carcass characteristics, and economics of finishing pigs. All 6 dietary treatments contained 17 ppm Cu from CuSO4 from the trace mineral premix. Additional treatment diets contained added CuSO4 to provide 70 and 130 ppm total Cu or a 50/50 blend of added Cu from CuSO4 and Cu-AA to provide 70, 100, and 130 ppm total Cu. There were 25 or 26 pigs per pen and 7 replicate pens per treatment.Overall, added Cu above 17 ppm did not influence ADG; however, pigs fed 70 and 130 ppm added Cu from the 50/50 blend of CuSO4 and Cu-AA had decreased (P = 0.045) ADFI and improved feed efficiency (P = 0.048) compared with those fed 70 and 130 ppm of added Cu from CuSO4 only. Similar to the F/G response, pigs fed diets that contained CuSO4 alone had poorer (P = 0.030) carcass F/G than those fed added Cu from the 50/50 blend of CuSO4 and Cu-AA. Neither Cu source nor level influenced economics.In conclusion, these data suggest pigs fed diets that contained added Cu from CuSO4 alone consume more feed but have poorer feed efficiency which translates into poorer carcass F/G compared to those fed a 50/50 blend of CuSO4 and Cu-AA. Copper level did not impact growth performance. Based on our study, it appears that the 50/50 blend of CuSO4/Cu-AA optimized feed efficiency and carcass feed efficiency of pigs marketed on a constant time basis

Turning Points in Containment of Lawrence Livermore National Laboratory Underground Nuclear Tests

Sometime in 1987 Billy Hudson, a long-time LLNL Containment Scientist and the Task Leader for Containment Diagnostics, put together a presentation entitled ''Turning Points in Containment''. This presentation identifies challenges, lessons learned, and changes made in containment practice over a 20-year period, from 1967-1987. Besides providing a significant historical summary, the presentation is valuable as we maintain a position of readiness 14 years after the last underground nuclear detonation. It is particularly valuable to personnel who are new to the program and have no first-hand experience in implementing underground nuclear test containment for actual tests. We now view this material as a unique containment summary with timeless importance. We envision this report to be particularly useful to new Containment Program members and anyone interested in the history of underground nuclear test containment practices. We believe that the Barnwell test, detonated in 1989, would have been added to this summary if Billy Hudson had the opportunity to update the presentation. We have chosen to add a few slides to the end of the original presentation to describe the issues and lessons learned from Barnwell

Upgrade of the Glasgow photon tagging spectrometer for Mainz MAMI-C

The Glasgow photon tagging spectrometer at Mainz has been upgraded so that it can be used with the 1500 MeV electron beam now available from the Mainz microtron MAMI-C. The changes made and the resulting properties of the spectrometer are discussed.Comment: 20 pages, 12 figure

Photoproduction of pi0-mesons from nuclei

Photoproduction of neutral pions from nuclei (carbon, calcium, niobium, lead) has been studied for incident photon energies from 200 MeV to 800 MeV with the TAPS detector using the Glasgow photon tagging spectrometer at the Mainz MAMI accelerator. Data were obtained for the inclusive photoproduction of neutral pions and the partial channels of quasifree single pi0, double pi0, and pi0pi+/- photoproduction. They have been analyzed in terms of the in-medium behavior of nucleon resonances and the pion - nucleus interaction. They are compared to earlier measurements from the deuteron and to the predictions of a Boltzmann-Uehling-Uhlenbeck (BUU) transport model for photon induced pion production from nuclei.Comment: 15 pages, 22 figures, accepted for publication in EPJ

Aplicação de nitrogênio a taxa variável em cultura de trigo: estudo de caso na Unidade Piloto de Agricultura de Precisão de Não-Me-Toque, RS.

O uso de sensores ópticos ativos como ferramenta para a definição da dose de nitrogênio a ser aplicada em cobertura na cultura do trigo é tecnologia disponível e em uso no Brasil. Com o objetivo de realizar o manejo sitio específico da adubação nitrogenada em cobertura na cultura do trigo utilizando-se sensor óptico ativo, foi realizado um estudo de caso na Unidade Piloto da Rede de AP em Não-Me-Toque, RS, na safra 2012. No momento da aplicação de nitrogênio em cobertura, a área foi dividida em dois talhões: um com aplicação a taxa fixa e outro a taxa variável. Foi utilizado equipamento comercial dotado de sensor óptico ativo para aplicação em taxa variável. A área foi monitorada antes e depois da aplicação de nitrogênio por meio de GreenSeeker®. Os resultados indicaram que o equipamento utilizado apresenta agilidade e flexibilidade na variação da dose de nitrogênio aplicada, configurando-se como uma ferramenta importante para o manejo sítio específico em trigo. Entretanto, há oportunidade para melhoria na estratégia de aplicação de N a taxa variável. Outros fatores, além da leitura de NDVI, podem ser levados em consideração para a aplicação em taxa variável. É necessário, por exemplo, considerar a 'dose máxima' para cada cultivar em função da resposta no rendimento de grãos e suscetibilidade ao acamamento