Simulation of the Long Term Behavior of Polymers on the Basis of Short Term Data

The mechanical long term behavior of polymers is usually determined by long term creep experiments up to 10.000 h which are very time and cost consuming. Therefore these data are often not available for the engineer. But even if long term data is available FEA-tools used in industrial practice usually can not sufficiently represent the nonlinear time, temperature and load-dependency of the mechanical long term behaviour. Hence the dimensioning of polymer parts is still a rather difficult engineering task. As a consequence of this, additional time consuming and expensive component tests in combination with several iterations are often necessary to design a polymer part for long term behaviour. This paper develops a method for the modeling of the load and temperature-dependent mechanical behaviour of polymers over a wide time, load and temperature range by means of finite element analysis. The method includes a material model as well as the determination of material parameters to calibrate the model. As a special feature of this method the model is calibrated by using creep data generated from short term experiments. The procedure improves the simulation of the long term behaviour of plastic-components and reduces the experimental effort significantly. The simulation results are finally validated by creep experiments performed on an example part

Exploring the North Atlantic Ocean on floppy disks

Data from four floppy disks found in the zip fileA selection of hydrographic station data in the Atlantic between 8°S and 70°N is packed on four 5 1/4" floppy disks. Sample utility programs for reading and plotting the data are also on the disks. We present this computer atlas in preliminary form for use by students and professionals, in the belief that easy access to this valuable historical data will be educational and stimulating.Funding was provided by the Office of Naval Research under contract Number N00014-84-C-0134, and the National Science Foundation through grant Number OCE86-13810

On the nature of estuarine circulation : part I (chapters 3 and 4)

The reader will quickly see that the subject matter of Chapter 3 is confined to the hydraulics of sharply stratified media, whereas real estuaries are always more or less diffusely stratified. What is more, no discussion is made of the order of magnitude of the friction terms. In ordinary single layer flow (such as in rivers) engineers already have crude approximations of the friction terms (Chezy and Manning formulas), but we do not have even these approximations for two layer flow. For this reason the differential equations of gradually varied flow of two layers are for the most part left unintegrated and all that is demonstrated is the qualitative aspects of the flow. In the case of entrainment of water from one layer into another we can only perform integrations of the equations when the amount of entrainment is known, whereas in real estuaries we do not have a priori knowledge of this amount. The reader will see, therefore, that the subject matter of Chapter 3 is really very incomplete, leaving undetermined all the constants which depend upon turbulent mixing, upon the frictional stresses on the bottom, and the free surface and the walls, and upon the amount of entrainment. The contents of Chapter 4 are somewhat different. First of all, they contain summaries of several of these papers have proceeded on the basis of hypotheses already published papers on the mixing in estuaries. Most about the nature of the mixing process. The applicability of these hypotheses appears to be restricted to only certain estuaries, and it must be admitted that more work has been done that involves guessing what the mixing processes in an estuary might be, than has been done in trying to find out what the mixing processes in an estuary actually are. As incomplete as the subject matter of Chapter 4 is, it is hoped that it will suggest which of the possible mixing processes in estuaries may be important in any particular one which is the subject of study, and that it will also suggest the type of observations which will be most desirable in studying a particular estuary. For example: in an unstratified estuary it seems that a more or less uniform spacing of stations up and down the estuary is desirable; but in an estuary which appears to be subject to the constraint of overmixing (Section 4.51) the location of stations should be largely confined to control sections.Office of Naval Research under Contract No. N6onr-27701 (NR-083-004)

Origin of the Mediterranean outflow

Toe origin of the Mediterranean outflow is one of oceanography\u27s oldest problems. In this work, the flow of western Mediterranean deep water up and over the sill at Gibraltar is investigated from hydrographic observations and current measurements. The deep water is found to flow westward along the Moroccan continental slope in the western Mediterranean or Alboran Sea and to rise as it approaches the Strait of Gibraltar...

A Contribution to Predict the Structural Dynamics of Mounted Short Glass Fiber Reinforced Thermoplastic Components

At the state of art, current simulative methods modelling joint properties as fixed interaction between components or concentrate on the characterization of the joint stiffness and damping of coupled metallic structures. In the current work, the developed thin layer interaction (TLI) method was applied to study the influence of the joint stiffness and damping of plastic components coupled with metallic structures. The joint stiffness and damping of different coupled metallic-plastic joint structures was characterized experimentally and was used to fill the reduced transverse shear stiffness and damping tensors of the numerical TLI model. The TLI model was used to determine the structural dynamics behavior of a short glass fiber reinforced plastic engine bracket mounted to a steel block. The comparison of experimental and simulative results shows a better correlation under the usage of the TLI model compared to a fixed modeled joint behavior. As result, the TLI model allows a better prediction of the structural dynamics of coupled plastic components. Further researches focus on the accurate experimental estimation of the boundary conditions regarding excitation and mounting of the plastic components. Thus, a more realistic modelling of the numerical joint boundary conditions is possible for an improved simulation of the structural dynamics of plastic components

Barotropic response to cooling

Also published as: Journal of Geophysical Research 85 (1980): 6661-6666Imposed horizontal density differences in a nonrotating fluid generate vertical circulation which has vanishing vertically integrated transports. When the system is rotating, geostrophic velocities can balance the density differences and the vertically integrated transports need not vanish locally. In a two-layer fluid, fin ite amplitude disturbances lead to barotropic flows that have the same direction as the velocity in the layer that thickens as a result of the disturbance. Specific calculations are carried out for the geostrophic adjustment model in situations that approximate those in which 18° water is formed south of the Gulf Stream. The upper layer transport that results from sudden cooling (as simulated by density differences that are initially unbalanced geostrophically) is in the same direction as the Gulf Stream transport and comparable to it in magnitude. A lower level transport of the same magnitude flows in the opposite direction with a maximum value about an internal radius of deformation to the right of that of the upper layer. The barotropic transport is about 1/ 5 as large and flows downstream in the Gulf Stream and upstream to the right of the Gulf Stream.Prepared for the Office of Naval Research under Contract N00014-79-C-0671 and for the National Science Foundation under Grants OCE 77-19451 and OCE 78-18460

Spatial and Temporal Scales of Sverdrup Balance

Sverdrup balance underlies much of the theory of ocean circulation and provides a potential tool for describing the interior ocean transport from only the wind stress. Using both a model state estimate and an eddy-permitting coupled climate model, this study assesses to what extent and over what spatial and temporal scales Sverdrup balance describes the meridional transport. The authors find that Sverdrup balance holds to first order in the interior subtropical ocean when considered at spatial scales greater than approximately 5°. Outside the subtropics, in western boundary currents and at short spatial scales, significant departures occur due to failures in both the assumptions that there is a level of no motion at some depth and that the vorticity equation is linear. Despite the ocean transport adjustment occurring on time scales consistent with the basin-crossing times for Rossby waves, as predicted by theory, Sverdrup balance gives a useful measure of the subtropical circulation after only a few years. This is because the interannual transport variability is small compared to the mean transports. The vorticity input to the deep ocean by the interaction between deep currents and topography is found to be very large in both models. These deep transports, however, are separated from upper-layer transports that are in Sverdrup balance when considered over large scales

BMI and EAT-26, predictors for low BMD?

The primary purpose of this study was to characterize bone mineral density (BMD) in healthy adult females in the Southern United States. A secondary purpose was to determine to what extent age, race, body mass index (BMI), and disordered eating contribute to BMD status. Age ranged from 25 to 50 years (39.8 ± 8.5). Race was classified into Caucasian or non-Caucasian. BMI was 28.97 ± 7.85 (kg/m2). The Eating Attitudes Test (EAT-26) was used to identify disordered eating characteristics. The Alara MetriScan was used to assess BMD values. Regression results showed that the linear combination of three independent variables—age, race, and BMI—predicted 34.5% of the variance in BMD, R2 = .345, R2 adj = .334, F(3, 170) = 29.87, p < .001. The strongest predictor of low BMD was Caucasian race