The incorporation of yield surface distortion into a unified constitutive model,part 2: Predictive capabilities

Summary The MATMOD-4V-DISTORTION model has been derived [1] with the intent of improving the MATMOD-4V model by adding the capability to predict distortions of small strain offset yield surfaces. This model is compared against a variety of experimental data to verify its behavior. Model simulations are compared with experimental data for proportional and nonproportional prestress histories and the effect of yield definition is also investigated. Finally, the same model which predicts a flattening of the yield surface in space is used to predict a rotation of the yield surface in ₁-₂ coordinates.With 9 Figures     

On the concept of relative and plastic spins and its implications to large deformation theories. Part II: Anisotropic hardening plasticity

Summary By resorting to both microscopic and macroscopic considerations, including the concept of single slip, dislocation stress, and a scale invariance argument we show that the notion and formalism of the relative spin introduced in Part I reduces to that of plastic spin previously recognized in the literature. The central feature of this reduction is the possibility of obtaining physically based constitutive equations for the plastic spin along with appropriate evolution equations for the dislocation or back stress. When these constitutive models are incorporated in the analysis of existing data on tension-torsion tests, we find satisfactory agreement between theory and experiment. In particular, a theoretical interpretation of the torsionally induced axial strain, as observed for example by Swift, Bailey et al., Hart and Chang, and others, is provided. Moreover, the recent experiments of Montheillet et al. on torsionally induced axial stresses are discussed in the light of the presently proposed models of large inelastic deformation inelasticity accounting for anisotropy and texture effects.

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With 12 Figures     

Considerations on speed selection and risk homeostasis in driving

Risk-taking behavior by drivers is put within the context of a general model of utility maximization by speed choice. It is shown that so-called "risk homeostasis" is possible only under very restrictive conditions. Under more general conditions, risk compensation can occur; that is, the safety effects expected from engineering measures will be discounted to a considerable degree by shifts in behavior.     

A simplified approach to the thermal behaviour of electrolytic Dewar cell calorimeters

A simplified approach, based on the concept of an overall heat loss coefficient, is described for the estimation of time-variant temperature profiles. The computation of the loss coefficient from experimental temperature maxima under programmed power input is also discussed.     

Don't let safety happen by accident

Get ready to update and improve your company's safety program. On pages 24-38, you'll find a comprehensive guide to safe industry practices to enhance your operation and help you stay in compliance with OSHA regulations such as the General Duty Clause and the Right-to-Know law. Achieving a safe, healthy, productive, and profitable business doesn't happen by accident. It takes upper-management commitment to improve equipment, procedures, and employee training. Managers have a personal and a legal responsibility for employees' safety on the job. Don't delay safety improvements!     

Collagen and its rational content in meat products: Part 1. Analytical studies

Computer-assisted simulation has been used to study the effect of collagen content on the biological value of meat proteins. It has been shown that an increase in the collagen content from 2·5% to 15-20% of the total amount of proteins contained in minced meat tangibly enhances protein utilization for tissue synthesis. Hence, the above collagen content in meat products heightens their nutritional and biological value and renders them more suited for human metabolism.     

Chord intercepts in a two-dimensional cell growth model

A foil of polypropylene is heat-treated in such a manner that a growing 2D cell-model is formed. A Rosiwal's line is placed into the totally primarily crystallized foil. The nucleus-coordinates of grains intercepting Rosiwal's line are measured. From these effective nuclei we determine at fraction transformedF = 1/4, 1/2 and 3/4 the distributions of grain-lengths and melt-lengths. Further we determine properties which are derived from the chord intercepts at a given F. Experimentally we find that the values (Poisson distribution of nuclei, chord intercepts, etc.) are in good agreement with the growing 2D cell-model.     

Vapor pressure measurements of para-hydrogen adsorbed on exfoliated graphite

Monolayer isotherms were measured for 15, 18, and 20 K for para-hydrogen adsorbed on exfoliated graphite foam, and for the second, third, and fourth layers in the temperature interval of 8 to 20 K, using the standard volumetric method. From the data, the isosteric heat of adsorption, molar entropies and internal energies were obtained as a function of coverage. The values for coverages above the third layer were compared to those at the p-H₂ bulk triple point, showing that, within our experimental uncertainty, the results are closer to the values of bulk solid para-hydrogen. Critical temperatures for the second and third layers and the triple point temperature for the second layer, were determined, yielding values of T_c2 = (10.0±0.1) K, T_c3 = (11.0±0.5) K and T_t2 = (6.5±0.1) K respectively. Features occurring along the monolayer coverages are compared to transitions which occur in the para-hydrogen phase diagrams adsorbed on graphite, obtained from heat capacity measurements by other authors. From the isotherms, compressibilities were calculated as a function of coverage for several temperatures. Whenever possible the obtained results were compared to existing data in the literature.     

Spin waves in spin-polarized gases in the Knudsen regime

Boundary conditions are discussed for spin dynamics equations in dilute spin-polarized quantum gases. The bulk equations have the macroscopic hydrodynamic form even when mean free paths of the particles are large, and the main question is whether a supplementary hydrodynamic boundary condition is valid. Different boundary processes are considered including spin-conserving and non-conserving reflections, slip, formation of adsorbed surface layers, etc. The macroscopic boundary condition fails in the cases of very effective surface processes with violation of time-reversal symmetry (e.g. spin-lattice relaxation) or very high surface-induced diffusion rates. Otherwise, the surface processes are described by a simple boundary condition or by -type singularities in bulk equations. The meaning of different macroscopic parameters is clarified. The formation of dense adsorbed boundary layers changes the frequency shifts and linewidths of spin-wave resonances because of effective exchanges between surface and bulk particles and strong interactions within the boundary layers. Here the broadening of resonances is explained not only by additional surface dissipation (diffusion), but also by dephasing processes originating from a renormalization of the molecular field in the boundary layers. The results explain recent experiments by the Cornell group.