Effect Of Uniaxial Stress Research Articles

Effect of compressive stress on power loss of Mn–Zn ferrite for high-frequency applications

In this work, the low-power-loss Mn–Zn ferrite was prepared by the traditional ceramic sintering process. This sample shows the good wide-temperature stability of power loss (Pcv). In the whole measurement temperature range of 25 - 120 °C, Pcvs maintain less than 100, 682, and 1455 kW/m3 at 100 kHz/100 mT, 500 kHz/100 mT and 800 kHz/100 mT, respectively. The effect of uniaxial compressive stress on power loss at 100, 500 and 800 kHz was investigated. Stress has greater impact on Pcv at high frequencies and Pcv increases remarkably. To clarify the mechanism of stress on power loss, Pcv was divided into three parts including hysteresis loss (Phv), eddy current loss (Pev) and residual loss (Prv), and the effect of stress on each part of loss was discussed. At the low frequency of 100 kHz, Pcv is mainly contributed by Phv. The applied stress leads the local anisotropic stress and makes domain wall displacement more difficult, which is the reason of the increase of Phv. When frequency increases to 500 and 800 kHz, Pev and Prv become more important. The compressive stress is in favour of electron transfer between Fe3+ and Fe2+ in grains and electron tunnelling effect at grain boundaries, which leads to the decrease of resistivity. This is the origin of enhanced Pev under the compressive stress. The enhanced Prv is related to the enhanced electronic diffusion under the compressive stress. The clarification of the mechanism of stress on power loss is beneficial to develop new soft ferrite materials with low stress sensitivity for high-frequency applications.

Experimental characterization of the effect of uniaxial stress on magnetization and iron losses of electrical steel sheets cut by punching process

The effect of uniaxial stress on iron losses of M400-50A grade non-oriented electrical steel sheets cut by punching process is experimentally studied. Samples cut along the rolling and transverse directions and having different number of cutting edges are used for this purpose. Measurements are carried out in the range of 10–100 Hz frequency of sinusoidal excitations at different magnetization levels under varying uniaxial stress by using a single sheet tester. The iron losses are obtained from the measurements and comparative analyses are made for different cases. The study shows that the effect of stress on the iron losses of the punched samples varies depending on the degradation level that the samples have after the cutting process. By considering this varying effect, when the combined effect of stress and punching is analyzed, it is observed that the iron losses increased up to 55.2% under compressive stress. It is also observed that the increase in the losses due to the effect of cutting can be recovered by applying tensile stress.

Multifractal properties of the molybdenum ribbon surface at mechanical loading

The effect of uniaxial tensile stress on the atomic structure and relief of the subsurface layer of molybdenum ribbons has been studied. The destruction of the Mo (100) face with the formation of crystallites was revealed near the crack tip. At the same time, the block structures are found to rotate both in the lateral plane and in its perpendicular plane. The surface layer structure in the lateral plane of the ribbon is fragmented into sections, which is associated with the surface relief at different scales. With a help of the concept of multifractal formalism, the spectra of singularities of the initial, loaded and ruptured surface are calculated. It is found that the width of the singularity spectrum, can serve as an indication of the forthcoming rupture.. Keywords: molybdenum ribbon, mechanical load, annealing, destruction of material, block structures, surface, multifractal formalism.

Мультифрактальные свойства поверхности тонких фольг молибдена при механическом нагружении

The effect of uniaxial tensile stress on the atomic structure and relief of the subsurface layer of molybdenum ribbons has been studied. The destruction of the Mo (100) face with the formation of crystallites was revealed near mouth of the crack. At the same time, the block structures are found to rotate both in the lateral plane and in its perpendicular plane. The surface layer structure in the lateral plane of the ribbon is fragmented into sections, which is associated with the surface relief at different scales. With a help of the concept of multifractal formalism, the spectra of singularities of the initial, loaded and ruptured surface are calculated. It is found that the width of the singularity spectrum, can serve as an indication of the forthcoming rupture.

Effect of uniaxial elastic stress on corrosion of X80 pipeline steel in an acidic soil solution containing sulfate-reducing bacteria trapped under disbonded coating

The effect of elastic stress on corrosion of X80 steel in an acidic soil solution containing sulfate-reducing bacteria (SRB) trapped under a simulated disbonded coating was investigated. The SRB numbers at the coating holiday after 14 days were approximately 106 cells/mL, and they were higher than those in the simulated disbonded coating region. The stressed coupons underwent more severe SRB corrosion and pitting at the same locations under the simulated disbonded coating due to the mechanochemical effect. These results indicated that the pitting process was affected by the applied elastic stress in the X80 steel.

Pressure-Induced Enhancement of Thermoelectric Performance in Rubrene.

In this work, the thermoelectric performance of a typical small-molecule organic semiconductor rubrene under different hydrostatic pressures was studied by first-principles calculation and molecular dynamics simulation. The ZT value of rubrene can reach 1.6 at 400 K due to an unprecedented increase in hole mobility under hydrostatic pressure. The underlying mechanism is ascribed to the suppression of low-frequency phonons (which weakens electron-phonon scattering) and the increase in the intermolecular electronic coupling. The effect of uniaxial stress has also been investigated to confirm this conclusion. Our results provide meaningful insights to understand the relationship between thermoelectric properties and hydrostatic pressure in organic semiconductors.

Effect of uniaxial stress on bursting energy absorption of paper

The overall usefulness of the bursting energy absorption (BEA) was studied for a better analysis of paper strength properties. Additionally, the changes of the BEA during more complex deformations of paper products, e.g., preliminary or simultaneous tensile and burst, were determined. For the purpose of the research, an experimental setup was designed. The results showed that the correlation between BEA and bursting strength was linear, but the proportionality strongly depended on paper grade. Thus, a more accurate method to characterize the bursting resistance (BR) of paper was proposed. The BR parameter is described by the three following parameters: average bursting strength, average bursting energy absorption, and the slope of the fitted linear regression curve (relationship between the bursting energy absorption and the bursting strength). This method revealed new mechanical behaviors of papers related to their preloading.

Stability of plane Couette flow past an initially stressed solid

In this paper, we carry out linear stability analysis of a coupled solid–fluid system in a plane Couette flow past an initially stressed neo-Hookean solid at creeping flow limit (Re=0) and arbitrary Reynolds number (Re), as well as for different solid thicknesses. In biological and engineering systems, we often encounter flows past initially stressed deformable solids. For these cases, initial strain or initial stress appears as an additional symmetry representing tensor in the constitutive relation. Consequently, initial stress induces anisotropy (transverse isotropy in the present case) and affects material properties. We employ a hyperelastic model for the initially stressed deformable solid to study the effects of both uni-axial and equi-biaxial initial stresses on flow instability. This study also presents a case where anisotropy in the solid interferes with the stability of the solid–fluid coupled system. In contrast with the previous formulations with two or three state Eulerian–Lagrangian formulations, the present formulation requires four configurations for the initially stressed solid, viz. stress-free, initially stressed, deformed, and the perturbed state. This formulation applies to any fluid–solid coupled problems where the solid contains initial/residual stress. Our results show that initial tensile stress stabilizes the flow, while compressive initial stress destabilizes the same. Fortuitously, this observation of coupled fluid–solid stability is in agreement with the stability of solid column-like structures, where compressive axial stress leads to buckling. We report similar results for uni-axial and equi-biaxial initial stress, for different wave modes at creeping flow limit and their extensions at higher Re, and various solid thicknesses. Two modes of instability, viz., short-wave and finite-wave modes present in the creeping-flow limit are significantly affected by tensile/compressive initial stress for both uni-axial and equi-biaxial cases. For uni-axial tensile initial stress, the finite-wave mode does not extend to high Re. Instead of them, we observe multiple upstream modes to become unstable for higher Re, which show the wall mode scaling as O(Re−1/3). These upstream modes are not observed for stress-free solid. This behavior is triggered by the additional coupling terms between initial stress and perturbed variable in the governing equations of initially stressed solids. However, for the equi-biaxial case, the finite-wave mode does extend to higher Re to show wall mode scaling. This mode further stabilizes/destabilizes depending on the tensile/compressive nature of the initial stress present in the solid.

Hysteresis characteristics of oxidation-thermodynamic for residual coal in goaf under uniaxial stress

During coal-mining processes underground, the coal spontaneous combustion caused by air leakage of narrow coal pillars and residual coal in goaf under pressure not only threatens the safety of mining of coal resources, but also leads to serious casualties. Therefore, the research of multi-field coupling for broken coal could be helpful to reveal the spontaneous combustion law of narrow coal pillars and residual coal in goaf and find the key for coal-fire prevention and control. Therefore, the uniaxial compression equipped with a temperature-programmed device is applied to conduct stress-heating tests on five types of coal particle sizes. Moreover, based on the Hertz contact deformation principle under the three-particle model, the thermodynamic hysteresis characteristics of broken coal under uniaxial stresses are theoretically analyzed. The results are shown as follows: (i) Uniaxial stress leads to significant hysteresis effects on the critical temperature of coal spontaneous combustion, heating rate, Graham’s Ratio-R2 temperature coefficient and pyrolysis temperature. (ii) As the particle radius increases, the growth rate of the exothermic intensity is suppressed, while it has no inhibitory effect on the critical temperature of the minimum exothermic intensity. (iii) The extreme point for the limit parameter of coal spontaneous combustion and the critical temperature shows the same corresponding hysteresis under uniaxial stress. The particle size ratio changes the limit parameter of coal spontaneous combustion obviously, and coal with a large particle size would reduce the risk of spontaneous combustion. (iv) The stress–strain curves and the stress-porosity curves are divided into stages, and it is found that the critical uniaxial stress of the porosity and strain of each coal sample is up to 4 MPa. Moreover, the temperature is the main reason for the hysteresis of permeability. The stress sensitivity of permeability declines with the effective stress rising, increases with the temperature going up, and decreases with the coal particle size reducing. (v) The hysteresis effect of uniaxial stress on coal spontaneous combustion first increases, then decreases, and finally increases.

Coupling Raman, Brillouin and Nd3+ Photo Luminescence Spectroscopy to Distinguish the Effect of Uniaxial Stress from Cooling Rate on Soda-Lime Silicate Glass.

Evolution of spectroscopic properties of a soda–lime silicate glass with different thermal history and under applied uniaxial stress was investigated using Raman and Brillouin spectroscopies as well as Nd3+ photoluminescence techniques. Samples of soda–lime silicate with a cooling rate from 6 × 10−4 to 650 K/min were prepared either by controlled cooling from the melt using a differential scanning calorimeter or by a conventional annealing procedure. Uniaxial stress effects in a range from 0 to −1.3 GPa were investigated in situ by compression of the glass cylinders. The spectroscopic observations of rearrangements in the network structure were related to the set cooling rates or the applied uniaxial stress to calculate an interrelated set of calibrations. Comparing the results from Raman and Brillouin spectroscopy with Nd3+ photoluminescence analysis, we find a linear dependence that can be used to identify uniaxial stress and cooling rate in any given combination concurrently. The interrelated calibrations and linear dependence models are established and evaluated, and equations relating the change of glass network due to effects of cooling rate or uniaxial stress are given.

Large response of charge stripes to uniaxial stress in La1.475Nd0.4Sr0.125CuO4

The La-based '214' cuprates host several symmetry breaking phases including superconductivity, charge and spin order in the form of stripes, and a structural othorhombic-to-tetragonal phase transition. Therefore, these materials are an ideal system to study the effects of uniaxial stress onto the various correlations that pervade the cuprate phase diagram. We report resonant x-ray scattering experiments on $\textrm{La}_{1.475}\textrm{Nd}_{0.4}\textrm{Sr}_{0.125}\textrm{Cu}\textrm{O}_{4}$ (LNSCO-125) that reveal a significant response of charge stripes to uniaxial tensile-stress of $\sim$ 0.1 GPa. These effects include a reduction of the onset temperature of stripes by $\sim$ 50 K, a 29 K reduction of the low-temperature orthorhombic-to-tetragonal transition, competition between charge order and superconductivity, and a preference for stripes to form along the direction of applied stress. Altogether, we observe a dramatic response of the electronic properties of LNSCO-125 to a modest amount of uniaxial stress.

Effect of uniaxial stress on energy harvesting, storage and electrocaloric performance of BZT ceramics

In this work, a systematic approach of waste (thermal/mechanical) energy harvesting and storage potential is studied in Ba0.85Zr0.15TiO3 (BZT) ceramics. The effect of stress on energy storage density (harvesting/storage) and electrocaloric performance is also studied. For this purpose, polarization–electric field hysteresis loops were recorded at various temperatures and uniaxial compressive stress. The Olsen cycle and electro-mechanical cycle are used for direct waste heat or mechanical energy to electrical energy conversion. A thermal energy-harvesting density of 42 kJ/m3 per cycle was obtained when the Olsen cycle was operated between 296–343 K and 0.25–1.5 MV/m. The electro-mechanical cycle-based energy harvesting is estimated as 78 kJ/m3 under the applied stress of 5–160 MPa and the electric field of 0.25–1.5 MV/m. The energy storage density is found as 39 kJ/m3 at zero stress field and 343 K, which increases to 53 kJ/m3 under the biased stress of 80 MPa in a wide operating temperature range of 296–328 K. It is observed that the high energy storage is a result of the reduction of the hysteresis loss. The electrocaloric temperature is found as 0.16 K and 0.18 K under the 0 and 80 MPa stress fields, respectively. Overall, the reported findings will enrich our understanding of the stress effect on BZT materials, which offers high performance for energy harvesting and storage-based applications. Moreover, this work can be also helpful in improving the energy storage density and electrocaloric effect via stress confinement.

Fatigue crack growth behavior of Ti-6Al-4V alloy fabricated via laser metal deposition: Effects of building orientation and heat treatment

This work studied the effect of building orientations and post-process heat treatments on the fatigue crack growth behavior of Ti-6Al-4V manufactured by laser metal deposition. The fatigue crack growth rate experiments were carried out in three sampling directions (YZ, ZY, XY) in order to evaluate the anisotropy. In addition, the heat-treated samples (YZ, ZY, XY) were used for comparison, which were heat-treated under the vacuum at 900 ℃ for 2 h followed by air cooling and 550 ℃ for 4 h followed by air cooling. The results showed that the ∆KT values before and after heat treatment were 13.6 and 15 MPa∙m1/2, respectively. In the hypo-transitional region, the effect of columnar grains orientation and uniaxial residual stress led to anisotropy in fatigue crack growth rate for as-built specimens. This effect is significantly attenuated after the post-process heat treatment. The coarsened α laths effectively changed the crack propagation behavior and improve the fatigue crack growth resistance of the material. In the hyper-transitional region, the fatigue crack growth was controlled by the inherent fatigue crack growth resistance rather than the microstructure, resulting in negligible differences in all fatigue crack growth rate curves.

Modulation of Landau levels and de Haas-van Alphen oscillation in magnetized graphene by uniaxial tensile strain/ stress

The strain engineering technique allows us to alter the electronic properties of graphene in various ways. Within the continuum approximation, the influences of strain result in the appearance of a pseudo-gauge field and modulated Fermi velocity. In this study, we investigate theoretically the effect of linear uniaxial tensile strain and/or stress, which makes the Fermi velocity anisotropic, on a magnetized graphene sheet in the presence of an applied electrostatic voltage. More specifically, we analyze the consequences of the anisotropic nature of the Fermi velocity on the structure Landau levels and de Haas-van Alphen (dHvA) quantum oscillation in the magnetized graphene sheet. The effect of the direction of the applied strain has also been discussed.

Effect of uniaxial stress on the electronic band structure of NbP

The Weyl semimetal NbP exhibits a very small Fermi surface consisting of two electron and two hole pockets, whose fourfold degeneracy in $k$ space is tied to the rotational symmetry of the underlying tetragonal crystal lattice. By applying uniaxial stress, the crystal symmetry can be reduced, which successively leads to a degeneracy lifting of the Fermi-surface pockets. This is reflected by a splitting of the Shubnikov-de Haas frequencies when the magnetic field is aligned along the $c$ axis of the tetragonal lattice. In this study, we present the measurement of Shubnikov-de Haas oscillations of single-crystalline NbP samples under uniaxial tension, combined with state-of-the-art calculations of the electronic band structure. Our results show qualitative agreement between calculated and experimentally determined Shubnikov-de Haas frequencies, demonstrating the robustness of the band-structure calculations upon introducing strain. Furthermore, we predict a significant shift of the Weyl points with increasing uniaxial tension, allowing for an effective tuning to the Fermi level at only 0.8% of strain along the $a$ axis.

Stress-modulated optimization of polymorphic phase transition in Li-doped (K,Na)NbO3

The effect of uniaxial compressive stress on the crystal structure of a 6 mol. % Li-doped (K,Na)NbO3 (LKNN6a) ceramic was investigated using in situ synchrotron X-ray diffraction, revealing the stress-induced relative change in monoclinic Pm and tetragonal P4mm phases. As such, stress-induced phase transformations, in addition to the lattice deformation and domain switching, are the contributing factors for the observed macroscopic mechanical behavior of LKNN6a. The in situ stress-dependent diffraction data also demonstrates a method to mechanically modulate the polymorphic phase transition temperature (TPPT) to a higher temperature, as observed by the temperature-dependent permittivity measurements under a constant bias stress. The external uniaxial compressive stress increases the stability of the lower symmetry monoclinic phase, shifting TPPT to a higher temperature by 60 °C for the maximum uniaxial compressive stress of 300 MPa in the studied composition. Importantly, the stress-induced stabilization of the room-temperature ferroelectric phase can be useful to optimize the phase transition region, as well as increase the temperature stability of lead-free KNN.

Effects of uniaxial compressive stress on the electrocaloric effect of ferroelectric ceramics

The effects of uniaxial compressive stress on the electrocaloric effect (ECE) of ferroelectric ceramics are studied by Landau–Ginzburg–Devonshire (LGD) thermodynamic approach, direct method, and indirect techniques. Soft lead zirconate titanate ceramics is used as a model material. The direct measurement results are given by an infrared camera combined with a set of specially designed testing setup. It is demonstrated that ECE can be significantly tuned by uniaxial compressive stress. The direct measurement results are essentially in agreement with the LGD theory calculated results, while significant discrepancies between direct and indirect methods are observed. These results are explained by the complex domain switching and possible phase transition behavior under the coupled thermo-electro-mechanical field. In addition, with compressive stress of 50 MPa, direct measurement shows that an improvement of ~ 66.7% in cooling capacity can be achieved at 375 K, which demonstrates that the application of compressive stress is an effective approach for enhancing ECE in ferroelectric ceramics. Our results not only provide insights into the effects of uniaxial compressive stress on ECE, but also offer more opportunities for the design of electrocaloric materials and devices.

Effects of Uniaxial Stress Along Different Directions on Alternating Magnetic Properties of Silicon Steel Sheets

Extensive research has shown that silicon steel sheets in electrical machines and power transformers are usually working under compressive or tensile stress, which affects both magnetic properties of silicon steel sheets and performance of electromagnetic devices. In this article, a magnetic property measurement system considering the stress effect has been developed and constructed based on the large cross-shaped single-sheet tester (LCSST). The uniformity of the stress distribution for LCSST is verified by the finite-element method. The B-H magnetic property of a specimen of non-oriented silicon steel 50JN470 in the direction of applied stress is measured by the proposed LCSST, and the results are in good agreement with those measured by the rectangle single-sheet tester (RSST) made by the Brockhaus Company. The RSST, however, cannot measure the effects of uniaxial stress on the magnetic properties. This article presents and analyzes the extensive experimental results of magnetic properties with uniaxial stress applied along both transverse and rolling directions ranging from 7 MPa compressive stress to 7 MPa tensile stress.

Nematic and time-reversal breaking superconductivities coexisting with quadrupole order in a Γ3 system

We discuss superconductivity in a model on a cubic lattice for a $\Gamma_3$ non-Kramers system. In previous studies, it is revealed that $d$-wave superconductivity with $E_g$ symmetry occurs in a wide parameter range in a $\Gamma_3$ system. Such anisotropic superconductivity can break the cubic symmetry of the lattice. In a $\Gamma_3$ system, the quadrupole degrees of freedom are active and the effect of the cubic symmetry breaking should be important. Here, we investigate the coexisting states of the $d$-wave superconductivity and quadrupole order by a mean-field theory. In particular, we discuss possible competition and cooperation between the superconductivity and quadrupole order depending on types of them. We find nematic superconductivity breaking the cubic symmetry and coexisting with quadrupole order. In the present model, we also find $d+id$ superconductivity, which breaks time-reversal symmetry but retains the cubic symmetry. We also discuss the effects of uniaxial stress on these superconducting states.

Experimental investigation of ASR-affected concrete – The influence of uniaxial loading on the evolution of mechanical properties, expansion and damage indices

The alkali silica reaction (ASR) in concrete causes internal localized swelling and micro cracking, which result in expansion and correlated deterioration of the concrete material. The stress state of the concrete is known to affect expansion due to ASR, with an anisotropic stress state giving rise to anisotropic expansion. Similarly, the orientation and extent of micro cracking have a directional effect on the concrete mechanical behaviour. This research studied the effect of sustained uniaxial compressive stress on the evolution of the mechanical behaviour of concrete in compression. Concrete cubes of 230 mm side length were uniaxially restrained and stored in accelerated conditions, with cores drilled in two directions for mechanical tests: a cyclic test in compression, i.e. a stiffness damage test (SDT) and a complete stress-strain test. A clear directional dependency of the mechanical characteristics was found. Furthermore, the results indicate that reduction in modulus of elasticity is well correlated with the expansion in the test direction. On the other hand, the damage indices obtained from the SDT merely relate to the expansion, which puts in question the SDT’s ability to predict ASR expansion in stressed concrete and therefore in concrete structures.