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Information Technology
Abstract A crystalline FEM theory is applied to investigate the relationship of the crystal geometry to the progress of plastic deformation localization (P.D.L.) and irreversible slip generation (LS.G.), which are part of the fatigue crack initiation process, by calculating the cyclic deformation behavior of a FEM model of a f.c.c, crystal which reproduces the restriction caused by the neighboring grains. As results, the followings are found: 1) In the same manner as the results for f.c.c, single crystal analyzed in the previous reports, P.D.L. and |.S.G. in a grain whose deformation is restricted by the neighboring grains can be simulated by using the crystalline FEM theory developed by the authors. 21 Under the conditions chosen, P.D.L. and |.S.G. proceeds very rapidly only when all of the following conditions are satisfied: a) loading direction is planer or coplaner double slip direction; b) the slip directions of the primary and conjugate systems meet the free surface at the same angle; c) the slip planes of the two systems meet the free surface at the same angle. 3) Under the conditions chosen, the progress of P.D.L. and I.S.G. has a high sensitivity to the difference of the geometrical relation of the slip systems to the free surface. The sensitivity of the progress of P.D.L. and I.S.G. to the misalignment of the loading axis is lower than the one to the geometrical relation of the slip systems to the free surface. INTRODUCTION It is generally agreed that plastic strain localization and irreversible slip generation (we abbreviate these phenomena to "P.D.L." and "I.S.G.' in this report.) are part of the fatigue crack initiation process, and that in order to explain the process, it is necessary to examine the microscopic mechanisms of these two phenomena.
- Telecommunications (0.82)
- Information Technology > Networks (0.82)
- Government > Regional Government > North America Government > United States Government (0.82)
Statistical Extreme Wave Analysis of the Italian Sea Wave Measurement Network Data In the Period 1989-1999
Corsini, Stefano (Servizio Idrografico e Mareografico Nazionale) | Guiducci, Franco (Servizio Idrografico e Mareografico Nazionale) | Inghilesi, Roberto (Servizio Idrografico e Mareografico Nazionale)
Abstract The aim of the present work is to give a significant aid to maritime and offshore designers who operate in the Mediterranean Sea. Ten years of wave data, collected from 8 buoys of the SWaN (Sea Wave measurement Network - National Hydrological and Marine Survey or, in Italian, RON Rete Ondametrica Nazionale, Servizio ldrografico e Mareografico Nazionale), are analysed by means of the standard statistical methods recommended by the 1AHR - Working Group on extreme wave statistics. Climatological wave analyses are presented for the stations of La Spezia, Alghero, Ponza, Mazara (Tyrrenian Sea), Monopoli, Ortona (Adriatic Sea), Crotone and Catania (Ionian Sea). Main and secondary sectors, related to the directions of maximum observed significant waves, are bounded Hypothesis of data independence and stationarity are discussed," independent episodes are extracted from the 10 years long RON database in connection with the main Italian wave climatological features. The Weibull distribution function is fitted to data for all the main sectors. Statistical models are applied in order to obtain return values of significant wave heights corresponding to return periods ranging from 5 up to 50 years. Results are discussed and, in order to test the robustness of the analysis, return values for the 5 years return period are compared with the second observed maxima. Correlation between the standard error of the distribution estimate, obtained by means of Least Squares Method and the overall number of missing data, is shown and discussed. THE SEA WAVE MEASUREMENT NETWORK The Sea Wave Measurement Network (Swan), Rete Ondametrica Nazionale (ICON) in Italian language, operates since July 1989. The Swan data were supplied by the National Hydrological and Marine Survey to public and private bodies that used them in the maritime structure design, into climate studies, into wave-forecast analyses and validation.
- Europe > Italy (0.28)
- North America > United States (0.28)
- Telecommunications > Networks (0.40)
- Information Technology > Networks (0.40)