Effect Of Biaxial Stress Research Articles

The effects of biaxial stress on Barkhausen noise signals when the magnetic field is noncoaxial with the stress axes

The Barkhausen noise amplitude was measured under conditions of biaxial stress in steel pipe for the case of a magnetic field noncoaxial with the stress axes. The stress axes for stresses σ1 and σ2 were orthogonal to each other. In particular, σ1 was the axial stress and σ2 was the hoop stress. Various angles were used for the field direction, along with various stress magnitudes, both compressive and tensile. The stress σ2 was always tensile, but σ1 was both compressive and tensile. A model for this biaxial stress situation, based on the Sablik–Jiles magnetomechanical model, was formulated. Using a model for the Barkhausen noise deriving from the Alessandro et al. model, the Barkhausen noise power maximum amplitude was computed for various field angles and stresses σ1 and σ2. The numerical results from this model calculation agreed qualitatively with many features of the experimental results. Thus, one found both numerically and experimentally that with field direction at small angles from the σ1 axis, the Barkhausen noise amplitude increased as the stress σ1 was increased from negative to positive. At large angles (generally greater than 45°), the reverse was true and the Barkhausen noise amplitude decreased as stress σ1 was increased. Also, the curves for the various angles tended to intersect when σ1 was set equal to σ2. Differences between numerical and experimental results are discussed, and suggestions are made for further improvement of the modeling.

Crystalline Structure Around the Single Vacancy in Silicon: Formation Volume and Stress Effects

ABSTRACTThe crystalline structure surrounding a single neutral vacancy in silicon is investigated through extensive first-principles total-energy calculations. The results indicate the existence of two distinct distortions of the lattice around the vacancy with essentially the same formation energies at zero pressure, but, however, with different formation volumes. The effect of hydrostatic and biaxial stresses on the relative concentration of each distortion is discussed, suggesting experimental ways to investigate the crystalline structure around the single vacancy and its role as a mediator of atomic diffusion in silicon.

Crystalline Structure Around the Single Vacancy in Silicon: Formation Volume and Stress Effects

ABSTRACTThe crystalline structure surrounding a single neutral vacancy in silicon is investigated through extensive first-principles total-energy calculations. The results indicate the existence of two distinct distortions of the lattice around the vacancy with essentially the same formation energies at zero pressure, but, however, with different formation volumes. The effect of hydrostatic and biaxial stresses on the relative concentration of each distortion is discussed, suggesting experimental ways to investigate the crystalline structure around the single vacancy and its role as a mediator of atomic diffusion in silicon.

Pressure and Stress Effects on Diffusion in Si

The thermodynamics of diffusion under hydrostatic pressure and nonhydrostatic stress is presented for single crystals free of extended defects. The thermodynamic relationships obtained permit the direct comparison of hydrostatic and biaxial stress experiments and of atomistic calculations under hydrostatic stress for any proposed mechanism. Atomistic calculations of the volume changes upon point defect formation and migration, and experiments on the effects of pressure and stress on the diffusivity, are reviewed. For Sb in Si, using as input the results of ab initio calculations of the effect of hydrostatic pressure on diffusion by the vacancy mechanism, the thermodynamic relationships successfully account for the measured effect of biaxial stress on diffusion with no free parameters. For other cases, missing parameters are enumerated and experimental and calculational procedures outlined.

Magnetic flux leakage inspection of gas pipelines: the effects of biaxial stress. Topical report, April 1993–September 1995: Crouch, A.E.; Beissner, R.E.; Burkhardt, G.L.; Bruton, F.A.; Creek, E.A.; Grant, T.S. Southwest Research Institute, San Antonio, TX (United States), PB96- 175476/GAR, 84 pp. (Mar. 1996)

The project is a component of the GRI program, 'Characterization of Magnetic Flux Leakage (MFL) Indications Found During In-Line Inspection of Natural Gas Transmission Pipelines'. The objective of the greater project was to investigate the effects of pipeline parameters and MFL inspection variables on corrosion, defect characterization. The work of SwRI, the subject of this report, concerns the effect of biaxial pipe wall stress.

Magnetic flux leakage inspection of gas pipelines: the effects of biaxial stress: Crouch, A.E.; Beissner, R.E.; Burkhardt, G.L.; Creek, E.A.; Grant, T.S. Southwest Research Institute, San Antonio, TX (United States), Nondestructive Evaluation Science and Technology Div., PB-96-175476/XAB

Magnetic flux leakage inspection of gas pipelines: the effects of biaxial stress: Crouch, A.E.; Beissner, R.E.; Burkhardt, G.L.; Creek, E.A.; Grant, T.S. Southwest Research Institute, San Antonio, TX (United States), Nondestructive Evaluation Science and Technology Div., PB-96-175476/XAB

EFFECT OF BIAXIAL MEAN STRESS ON CYCLIC STRESS‐STRAIN RESPONSE AND BEHAVIOUR OF SHORT FATIGUE CRACKS IN A HIGH STRENGTH SPRING STEEL

Abstract— Biaxial fatigue tests were conducted on a high strength spring steel using hour‐glass shaped smooth specimens. Four types of loading system were employed, i.e. (a) fully reversed cyclic torsion, (b) uniaxial push—pull, (c) fully reversed torsion with a superimposed axial static tension or compression stress, and (d) uniaxial push—pull with a superimposed static torque, to evaluate the effects of mean stress on the cyclic stress—strain response and short fatigue crack growth behaviour. Experimental results indicate that a biaxial mean stress has no apparent influence on the stress—strain response in torsion, however a superimposed tensile mean stress was detrimental to torsional fatigue strength. Similarly a superimposed static shear stress reduced the push—pull fatigue lifetime. A compressive mean stress was seen to be beneficial to torsion fatigue life. The role of mean stress on fatigue lifetime, under mixed mode loading, was investigated through experimental observations and theoretical analyses of short crack initiation and propagation. Using a plastic replication technique the effects of biaxial mean stress on both Stage I (mode II) and Stage II (mode I) short cracks were evaluated and analysed in detail. A two stage biaxial short fatigue crack growth model incorporating the influence of mean stress was subsequently developed and applied to correlate data of crack growth rate and fatigue life.

The Effects of Film Thickness and Texture on the high and Low-Field stress Response of Lead Zirconate Titanate Thin Films

ABSTRACTLead zirconate titanate (PZT) thin films are currently employed in non-volatile ferroelectric memories (FRAM's) and are intended to be used as the active material in a number of microelectromechanical systems (MEMS). Several groups have reported that both the piezoelectric and dielectric characteristics of ferroelectric thin films improve with an increase of film thickness, though the reasons for those improvements are unclear. Previous investigations on the effects of biaxial mechanical stress indicate that non-180° domain wall motion is limited in PZT 52/48 films less than 0.5 μm thick. It is possible that some of the improvements of the dielectric and piezoelectric characteristics reported for thicker films (i.e. films thicker than 0.5 μm) are associated with an increase of extrinsic contributions to the properties. To evaluate domain wall mobility in thicker films, the high and low-field stress response of sol-gel PZT fabricated with either rapid thermal processing or conventional furnace annealing were investigated. Films with thicknesses ranging from 0.6 to 5.0 μm thick were measured as a function of applied biaxial stress (±110 MPa). It was found that for all films tested the changes of capacitance were on the order of 2–3%. High-field measurements showed: (1) the coercive field to be insensitive to applied stress, (2) remanent polarizations to decrease about 20% at the maximum applied tension, (3) remanent polarizations to increase less than 10% with applied compression, and (4) all changes to be reversible over the stress range investigated. These results suggest that extrinsic contributions are limited for the films tested.

The effects of compressive stresses on the abrasion of diamond coatings

The effects of high biaxial compressive stresses on the abrasion of diamond coatings by diamond particles were evaluated using an atomic force microscope (AFM). The specimens subjected to testing were diamond coatings deposited on cemented carbide substrates, receiving high biaxial stresses due to thermal expansion mismatch, and freestanding stress-free diamond coatings. It is shown that the highly stressed coatings obtain a smoother worn surface and a significantly lower wear rate as compared to the stress-free coatings. Thus, biaxial stresses increase the inherently high wear resistance of diamond coatings. The results agree with a previously proposed model for the effect of high biaxial compressive stress on the abrasion of brittle coatings.

The Effects of Biaxial Stress on the Ferroelectric Characteristics of PZT Thin Films

ABSTRACTThe design and implementation of microelectromechanical (MEMS) systems requires a sound understanding of the influence of film stress on both the ferroelectric and piezoelectric characteristics of thin films to be used for sensing and/or actuation. Experiments were conducted in which thin film samples of sol-gel derived PZT were subjected to applied biaxial stresses from -139 to 142 MPa. Films were characterized at known stress states (derived from known values of residual stress and large deflection plate theory) in terms of their ferroelectric polarization (saturated and remnant), dielectric constants, coercive field strengths, and tan δ. Results obtained indicate that domain wall motion in thin films contributes much less to the observed response than is typical for bulk PZT materials. Alternative mechanisms are proposed in an attempt to explain the discrepancies.

Biaxial stress effects on hysteresis and MIVC

Changes in the magnetic properties of a cruciform-shaped SAE-4130 steel specimen were measured under biaxial stress conditions. Compared to model predictions are the experimental remanence at various biaxial stresses and the magnetically induced velocity changes (MIVC) of ultrasonic shear and longitudinal waves propagated perpendicular to the stress plane.

Modeling the Effects of Biaxial Stress on Magnetic Properties of Steels with Application to Biaxial Stress Nde

This paper reviews recent work on the effect of biaxial stress on magnetic properties obtained from hysteresis loops. Both experimental and theoretical work are discussed. Biaxial stress measuremen...

Biaxial stress effects on magnetization perpendicular to the stress plane

Effects of biaxial stress in steel on magnetization in a direction normal to the stress plane were investigated both theoretically and experimentally. The two results, which agreed qualitatively, showed that the magnetization in the normal direction generally decreased with the absolute value of the sum of the two principal stresses. The implication to nondestructive measurements of biaxial stress is discussed.

Micromagnetic model for the influence of biaxial stress on hysteretic magnetic properties

A micromagnetic formulation has been developed for modeling the effect of biaxial stress on magnetoelastic processes in polycrystalline steels. In particular, the formulation employs the Schneider–Cannell–Watts model and involves substitution of an effective stress equal to one of the deviatoric (i.e., distortional) normal stress components, depending on whether the field is parallel to a tensile or compressive axis or to the third axis perpendicular to the plane of biaxial stress. Computer results are compared to experimental results on the effects of biaxial stress on magnetic properties in mild steel and in SAE-4130 steel. Good qualitative agreement is found in almost all cases, in that in going from one biaxial stress case to the next, the same kinds of changes are seen magnetically. It is also shown from the model and the data that a method can be formulated to nondestructively determine the difference in biaxial stresses.

Micromagnetic model for biaxial stress effects on magnetic properties

A micromagnetic formulation has been developed for modeling the effect of biaxial stress on magnetoelastic processes in polycrystalline steels. The formulation uses a modified version of the Kashiwaya model for the effect of biaxial stress on magnetic properties and combines it with the Schneider-Cannell-Watts model for magnetoelastic processes in steels. In particular, the model involves use of an effective stress equal to one of the deviatoric (i.e. distortional) normal stress components, depending on whether the field is parallel to a tensile or compressive axis or to the third axis perpendicular to the plane of biaxial stress. Computer results are compared to experimental results on the effects of biaxial stress on magnetic properties in mild steel and in SAE-4130 steel. Good qualitative agreement is found in almost all cases, in that in going from one biaxial stress case to the next, the same kinds of changes are seen magnetically.

Effect of Biaxial Stress on the Propagation of Mode I Small Surface Crack.

The crack propagation rate da/dN at the specimen surface or db/dN toward the inner direction perpendicular to the specimen surface and crack opening displacement COD of a mode I small surface crack in a round bar are examined under biaxial stresses by means of the combination of plane bending and cyclic torsion. When the stress intensity factor range ΔK* at the deepest point of the crack periphery is the same, db/dN increases with the decrease in biaxial stress ratio C. An analogous tendency is recognized in the relationship between da/dN and ΔK at the specimen surface. A unique relationship is obtained between da/dN and crack tip opening displacement CTOD in spite of C. Thus, it can be concluded that the main factor which controls da/dN is CTOD.

Effect of biaxial stress, on magnetoacoustic emission from nickel

Magnetoacoustic emission (MAE) measurements have been made on a cross-shaped nickel plate subjected to biaxial tensile and compressive stresses (or strains) in a magnetizing field applied parallel to one of the axes. The results indicate that MAE generally decreases with increasing compressive stress ( sigma /sub x/) normal to the direction of the applied field (H/sub y/) irrespective of the sign of the stress ( sigma /sub y/) parallel to the field. However, when sigma /sub y/ tensile, this decrease in the MAE is more rapid than with compressive sigma /sub y/. It is found that MAE varies more markedly when presented as a function of stress rather than of strain.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effect of Biaxial Stresses on the Threshold of Small Surface Crack Propagation.

In order to investigate the effect of biaxial stresses due to the combination of plane bending and cyclic torsion on the threshold of mode I small surface crack propagation, the relationship between the threshold stress and crack length under various biaxial stress ratios C was examined using a circular shaft made of carbon steel. The threshold stress intensity factor is constant above some crack length in each C, but becomes lower with the decrease in C. The length of the slipped regionγp at the crack tip on the threshold of crack propagation is nearly constant regardless of C. Therefore, if the threshold curve of crack propagation in C = 0 is determined experimentally, the threshold curves in other C can be deduced from the relationship betweenγp and C.

Effect of Biaxial Stress on Solid Phase Epitaxy of Silicon

ABSTRACTThe effect of biaxial stress on solid phase epitaxial growth (SPEG) rate of crystalline Si(100) into self-implanted amorphous surface layer has been measured. Biaxial stresses in the crystalline and amorphous phases were generated by bending the silicon wafer using the residual stresses in Ge films deposited on the back side of the wafer. Stresses were determined at SPEG temperatures by optical measurements of wafer bending curvatures. Tensile stresses up to 13 MPa in the crystalline phase and 34 MPa in the amorphous phasewere achieved during SPEG at 530ºC. An optical system based on the time-resolved reflectivity (TRR) technique was devised to measure the growth rates of two adjacent samples during a single SPEG run. This enables a direct comparison of the growth rates under different stress conditions without concern for run-to-run temperature variations. We found that the growth kinetics in all the samples were retarded as the c/a interface approached the free surface. However, the extent of this rateretardation was reducedin the stressed samples, leading to stress-enhanced growth kinetics. We speculate that the application of the biaxial tensile stresses might slow down the incorporation of hydrogen into the amorphous phase, a mechanism for the rate-retardation.

Biaxial stress effects on the TE/TM polarization switching of InGaAsP ridge-waveguide lasers

TE/TM (transverse electric/magnetic) polarization switching in ridge-waveguide InGaAsP lasers is analyzed with due considerations to biaxial stress effects on both the waveguiding and gain properties of the device. The conditions of switching for several models are established. In particular, the gain expression for uniaxial stress is extended to include biaxial stress, and the differences between the different models are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>