Internal Shear Stress Research Articles

The Stress-Magnetic Properties of Amorphous Magnetic Alloy

Effects of internal shear stress applied by torque on the magnetic properties of Fe-based amorphous alloys were studied under weak magnetic fields of less than 800 A/m, where strips were helically bonded onto the shaft so as to form an angle of 45° with respect to the thrust direction. It was found that the permeability of each amorphous alloy in different gluing conditions reached for each sample a constant value above a certain torque and these torque values depend on the internal compressive strain applied by gluing A magnetization process model is considered to explain the above-mentioned behavior and states that the compressive stress affects the restraint of magnetic domain wall displacement.

A stress induced ferroelastic phase in thiourea

Abstract Planar domain walls have been observed in the ferroelectric phase of thiourea (T < 169 K). Their origin has been attributed to a ferroelastic distortion towards a monoclinic phase belonging to the point group m. Such a phase might be stabilized by external or internal residual shear stresses in the presence of a polarization. This suggests that a coupling between the polarization P and the distortion exy exists in the expansion of the free energy. The spontaneous polarization vector within this monoclinic phase is not necessarily parallel to the domain walls, leading to electrostatic charges localized on them, as previously inferred from Raman experiments.

アモルファス磁性合金薄帯の応力‐磁気特性

Effects of internal shear stress applied by torque on the magnetic properties of Fe-base amorphous alloys were studied under weak magnetic fields of less than 800 A/m, where strips were helically bonded onto the shaft so as to form an angle of 45° with respect to the thrust direction. It was found that the permeability of each amorphous alloy in different bonding conditions had for each sample saturated values over certain torque and these torque values depended on the internal compressive strain applied by bonding. A magnetization process model is considered to explain the above-mentioned behavior, and states that the compressive strain affects the reduction of magnetic wall movement.

Shear stress variations in an estuary

Observations in 1929 of the tidal variation of surface gradients in the Tees estuary were combined with measurements of the velocity and density structure in 1975 to compute the internal and boundary shear stresses. Drag coefficients were generally higher on ebb than on flood tides and this inequality is explained using established boundary layer theory. The results suggest that the wide variation in drag coefficients in estuaries may depend, in addition to roughness changes, on the bed slope and the available kinetic energy of the mean flow.

II. Dynamic and crystallographic analysis

Abstract Dislocation transmission through a (122), ∑ = 9 boundary in Ge or Si is first studied from the crystallographic point of view. Grain-boundary structure alterations induced by transmission reactions suggested by experimental observations are investigated. The Burgers vectors of extrinsic grain-boundary dislocations and their associated steps are determined. A possible transmission process, which accounts for lattice dislocation dissociation, i.e. transmission of the leading Shockley partial without constriction, is discussed. The strain transmission is also examined using calculations of internal shear stresses exerted by dislocation pileups, in one crystal, at the interface, on all the second crystal's slip systems. Interpretation of the observed transmission reactions is attempted by combining the crystallographic and the dynamic criteria.

Two coplanar griffith cracks under shear loading in an infinitely long elastic layer

We consider the problem of determining the stress distribution in an infinitely long isotropic homogeneous elastic layer containing two coplanar Griffith cracks which are opened by internal shear stress acting along the lengths of the cracks. The faces of the layer are rigidly fixed. The cracks are located in the middle plane of the layer parallel to its faces. By the use of Fourier transforms we reduce the problem to solving a set of triple integral equations with a cosine kernel and a weight function. The triple integral equations are solved exactly. Closed form analytical expressions are derived for the stress intensity factors, shape of the deformed crack, and the crack energy. Solutions to some particular problems are derived as limiting cases. Numerical results are presented in the form of graphs.

The Metallurgy of Oxygen in Silicon

A review of some of the key issues involving the metallurgy of oxygen in silicon crystals demonstrates that it is a prototypical solid state materials system. The incorporation of oxygen into Czochralski-grown ingots from melt contact with silica crucibles is described in the context of the Si-SiO2 phase diagram. This paper reviews the techniques for characterizing oxygen in silicon, with an emphasis on secondary ion mass spectrometry (SIMS) and 18O isotope substitution. The intrinsic diffusivity and solubility of oxygen in silicon derived from these SIMS measurements are compared to similar results from other techniques, as well as to the related extrinsic behavior of oxygen. Aggregation phenomena involving oxygen, including thermal donor formation and precipitation, are also discussed. Finally, the topics of internal gettering, shear stress, and thermal oxidation are summarized.

On the influence of material properties on penetration of a thick elastic-plastic body

Within the frame-work of finite deformations of continuous media, the quasi-static deformations are considered that ensues upon applying internal pressure and axial shear stress, uniformly distributed along the surface of a cylindrical hole of infinitesimal initial radius in an elastic-plastic body of unbounded extent. With internal pressure only, also dynamic effects are taken into account. For each considered case of material and loading analytic expressions are given for the state of stress in the body and the amount of energy being dissipated in plastic working during the deformation process. The obtained results furnish the basis for a discussion of the influence of material parameters on the mechanical behavior of armor materials.

The Chemistry of Oxygen in Silicon

ABSTRACTSome of the key issues involving the chemistry of oxygen in silicon crystals are presented in this paper. The incorporation of oxygen into Czochralski-grown ingots from melt contact with silica crucibles is described in the context of the Si-SiO2 phase diagram. The techniques for characterizing oxygen in silicon are reviewed, with an emphasis on the use of secondary ion mass spectrometry (SIMS) and 18O isotope substitution. The intrinsic diffusivity and solubility of oxygen in silicon derived from these SIMS measurements are compared to similar results from other techniques as well as related extrinsic behavior of oxygen. Aggregation phenomena involving oxygen, including thermal donor formation and precipitation are discussed. Finally, the recent progress in understanding internal gettering and shear stress are summarized.

A comparison of some equations for the flexural vibration of damped sandwich beams

This paper compares the theories of flexural vibration of damped, three-layer sandwich beams as presented by Yan and Dowell, and by DiTaranto and Mead and Markus. Depending on the assumptions made about the internal shear stress distribution, the differential equation of transverse flexural displacement is either of fourth or sixth order. The inclusion of the effects of face-plate shear deformation and longitudinal inertia in the analysis yields a sixth order differential equation if the beam section is symmetric, and an eighth order equation if the section is unsymmetric. Flexural wave speeds and loss factors computed from the theories are presented and compared. The DiTaranto and Mead and Markus equations yield reliable values provided the flexural wavelength is greater than about four face-plate thicknesses. The Yan and Dowell equations yield reliable values only at much greater wavelengths or when the central layer in the sandwich is very thick.

Constitutive relationships and a failure criterion for concrete based on fundamental material properties

Synopsis The functional stress-strain relationships obtained by Kotsovos from his application of regression analysis to empirical data are used as the basis for a derivation of multiaxial constitutive relationships, for concrete subjected to compressive stresses, which distinguish between loading and unloading. A model is proposed in which internal cracking is accompanied by an internal transfer of energy from the deviatoric stress system to the spherical stress system, resulting in modified values of the effective internal spherical and shear stresses and of the shear strain. This transfer of energy is regarded as an irreversible process which can only take place during loading and internal crack propagation. The proposed failure criterion is that failure of the material takes place when, under any system of applied compressive stresses, the internal shear stress reaches a unique value equal to that which exists at failure in a uniaxially compressed solid cylindrical specimen of 100 mm diameter and250 mm length. For any other general compressive stress state which generates a modified octahedral shear stressless than this unique value, the concrete will retain its load-bearing capacity.

Mixed boundary value problem of an infinite thick elastic slab containing a flat annular crack under torsion

In the present paper we consider the problem of determining the stress distribution in an infinitely long isotropic, compressible, homogeneous elastic slab containing a flat annular crack which is opened by internal shear stress. The faces of the slab are assumed to be stress free and the crack is located in the middle plane of the slab. The problem is formulated in triple integral equations which reduce to an infinite system of simultaneous equations, which are solved numerically.

External crack in torsion in an infinite medium with a cylindrical inclusion

This paper deals with the stress distribution in an infinite homogeneous isotropic elastic medium with a cylindrical inclusion and an external crack opened by internal shear stress acting along the crack. The cylindrical inclusion is also assumed to be homogeneous isotropic and elastic. The problem is reduced to the solution of a Fredholm integral equation which is solved numerically. Closed form expression is obtained for the stress intensity factor and its numerical values are graphed to demonstrate the effect of the modulus of rigidity of the inclusion. The order of the stress singularity is obtained when crack touches the cylindrical inclusion.

Vertical Mixing in Stratified Tidal Flows

A set of mixing length functions based on an adaption of the theories of Prandtl, Rossby, Montgomery, and Ellison are presented as a means of calculating the internal shear stresses and vertical flux of solutes in gradually varying turbulent stratified tidal flows. Field observations, made in a straight canalized reach of an estuary, were used to determine the best-fit values of empirical coefficients in generalized relationships between the mixing lengths and gradient Richardson Number. The main purpose of the research was to improve the representation of vertical exchange processes in mathematical models of estuaries.

Liquid-Tissue Mechanics in Amphibian Gastrulation: Germ-Layer Assembly inRana Pipiens

During amphibian gastrulation, migrating subsurface germ layers may flow past one another like immiscible viscous liquids in response to tissue surface tension forces. We describe here two physical tests for liquid-tissue morphogenesis in cultured aggregates of subsurface ectoderm (E), mesoderm (M) and endoderm (N) excised from mid-yolk-plug Rana pipiens gastrulae. (i) Liquids are coherent substances in which subunits can slip past one another to relax internal shear stresses. We find, in cross-sections of cell aggregates fixed during compression, that cells within flattened aggregates are intially deformed, but do, as predicted, gradually reassume their original, undistorted shapes, (ii) Surface tensions (γ's) govern ordinary liquid-droplet spreading; e.g. , if equal-sized droplets A and B fuse in medium O, B spreads around A when γAO γBO. When pairs of subsurface aggregates are cultured together, N surrounds M and E, and M surrounds E. To see if γEO > γMO > γNO. we flatten aggregates with quartz fibers calibrated to measure the force of compression. As predicted, under the same flattening force, E aggregates are rounder than M aggregates, which are rounder than N aggregates. Furthermore, a second surface tension relationship can account for the autonomous involution of M between E and N; and these surface tension relationships can also explain the inversion of E, M and N by coated ectoderm to produce normal gastrular germ-layer arrangements. We conclude that, combined with active cell shape changes in solid-like surface cell layers and also with autonomous elongation of dorsal lip mesoderm, tissue surface tension control of liquid-tissue flow in subsurface germ layers is a key morphogenetic mechanism in amphibian gastrulation which might be regulated by changes in intercellular adhesiveness.

Two coplanar Griffith cracks in an infinite elastic layer under torsion

We consider the problem of determining the stress distribution in an infinitely long isotropic homogeneous elastic layer containing two coplanar Griffith cracks which are opened by internal shear stress acting along the lengths of the cracks. The faces of the layer are assumed to be stress free. The cracks are located in the middle plane of the layer parallel to its faces. By using Fourier transforms, we reduce the problem to the solution of a set of triple integral equations with a cosine kernel and a weight function. These equations are solved exactly by using finite Hilbert transform techniques. Finally we derive the closed form expressions for the stress intensity factors and the crack energy. Solutions to the following problems are derived as particular cases: (i) a single crack in an infinite layer under torsion, (ii) two coplanar cracks in an infinite space under torsion, (iii) a single crack in an infinite space under torsion.

Mean circulation in shallow seas

The mean circulation of shallow seas arises as the residue of chaotic first-order flow episodes created by winds, tides, and river inflow. The average effect of many such episodes is to generate an internal pressure and shear stress distribution which may differ significantly from a steady solution of the equations of motion. Within the coastal boundary layer (of about 10-km width), complex average effects of variable flow probably dominate. However, in mid-shelf regions of the Mid-Atlantic Bight, for example, classical steady state models adequately describe the main features of the mean circulation. The statistical effects of variable first-order flow even bring about some simplifications of the theory, i.e., linear internal and bottom friction laws and a decoupling of salt transport from the mean circulation. The mid-shelf circulation of the Mid-Atlantic Bight is thus found to consist of four additive components, each driven by offshore wind, longshore wind, longshore pressure gradient, and density contrasts caused by freshwater influx. The longshore pressure gradient enters the theory as a parameter necessary for describing the interaction of a portion of the continental shelf with the rest of the ocean. The pressure gradient driven flow component is responsible for some notable circulation features such as the line of divergence in bottom drift at about the 60-m isobath. The wind-driven and thermohaline flow components are familiar in character. Quantitatively, the four components together account satisfactorily for the observed mean shelf circulation.

Martian glaciation and the flow of solid CO 2

The flow law determined experimentally for solid CO 2 establishes that a hypothesis of glacial flow of CO 2 at the Martian poles is not physically unrealistic. Compression experiments carried out under 1 atm pressure and constant strain rate demonstrate that the strength of CO 2 near its sublimation point is considerably less than the strength of water ice near its melting point. The data fit a power law “creep” equation of the form ϵ ̇ = (4 × 10 6) σ 3.9 exp( −12 200 RT ) , where ϵ is compressive strain rate (sec −1), σ is compressive stress (bars), R is the gas constant in calories per mole, and T is absolute temperature. The exponent of σ of 3.9 contrasts with a value near 3.1 for water ice, and indicates that the strain rate is somewhat more sensitive to stress for CO 2 than for water. Likewise, the low activation energy for creep, 12 200 cal mole −1, illustrates that CO 2 is not highly sensitive to temperature and is thus likely to flow over a broad range of temperatures below its melting point. Strength values for CO 2 are of the order of one-tenth to one-third the strength of ice under equivalent conditions. A plausible glacial model for the Martian polar caps can be constructed and is helpful in explaining the unique character of the polar regions. CO 2-rich layers deposited near the pole would have flowed outward laterally to relieve high internal shear stresses. The topography of the polar caps, the uniform layering of the layered deposits, and the general extent of the polar “sediments” could all be explained using this model. Flow of CO 2 rather than water ice greatly reduces the problems with Martian glaciation. Nevertheless, problems do remain, in particular the large amounts of CO 2 necessary, the need to increase vapor pressure and temperature with depth in the polar deposits, and the lack of good observational evidence of flor features. Within the limits of the present knowledge of surface conditions of Mars, CO 2 glaciation appears to be a realistic alternate working hypothesis for the origin of the polar features.

Internal stresses in the α -α′ phase transition of coherent metal-hydrogen systems

In anα-α′ phase transition of the type discussed by Wagner and Horner, the smoothly varying hydrogen distribution generates coherency stresses in the metal crystal. The system is in a metastable state, which is expected to have a long lifetime if the internal stresses are smaller than some critical stress for destroying coherency. A comparison of the calculated internal shear stress with the experimental value of the critical shear stress for the onset of plastic deformation in a Nb crystal suggests that there may well be an appreciable region in which a coherent transition is experimentally observable.

DISSIPATION OF WAVE ENERGY DUE TO OPPOSING CURRENT

Energy dissipation and wave height attenuation were analysed theoretically for surface waves propagating against uniform flow. Energy dissipation was estimated from evaluation of work "by internal and boundary shear stresses. Experiments were conducted in a test flume of 20m long, 0.8m wide and 0.5m high. Results showed that tested values of rate of wave height attenuation were comparable with theoretical values.