Uniaxial Mechanical Stress Research Articles

The effect of uniaxial mechanical stress on electronic and dynamic properties of silicon

The effect of uniaxial mechanical stress on electronic and dynamic properties of silicon

ODF-based model considering compressive stress for modeling the magnetic properties of Grain-oriented electrical steels

Grain-oriented electrical steels (GOES) are widely used in the manufacturing of high efficiency energy conversion systems thanks to their excellent magnetic properties along the rolling direction. Nevertheless, on the one hand, GOES exhibit strong magnetic anisotropy, resulting in distinct magnetic properties regarding the direction of the applied magnetic field to the rolling direction. On the other hand, GOES undergoes changes in their magnetic properties due to the industrial manufacturing process and mechanical constraints during operation. In general, stress, and particularly compressive stress, deteriorates magnetic properties. This paper deals with the modeling of the magnetic behavior of GOES under compressive stress. The orientation distribution function (ODF) based approach recently applied to describe the B-H first magnetization curves of a conventional GOES without stress as well as under applied uniaxial mechanical tensile stress is extended to account for the effect of compressive stress, with different considerations of modeling. The magnetic properties and the sensitivity of the ODF-based model to the magnetization direction as well as to the applied compressive stress are analyzed. Oscillation issues inherent to the ODF-based model are also discussed.

Environmental cell for USANS/SANS studies with aggressive fluids at high pressures and temperatures

The new (Ultra) Small Angle Neutron (USANS/SANS) cell provides in-situ monitoring capability of the evolving microstructure and physical properties of a wide range of natural and artificial materials. This modular, portable compact environmental cell is designed for thermal, mechanical and chemical loading measurements compatible with all neutron and X-ray-based research facilities worldwide that is fine-tuned to a specific beamline. A seamless integration of time-lapse structural information, on scales ranging from the sub-nano to the micrometre has been demonstrated in a series of USANS/SANS experiments performed on rock samples subjected to hydrostatic and uniaxial load, reactive fluid flow and elevated temperatures. The modular design of the cell allows optimisation for specific applications, ranging from cryogenic to temperatures over 500 °C, with plans for further extensions of this range in the future. Uniaxial mechanical stress up to 1000 bar, and sample surrounding fluid/gas pressure of up to 1000 bar in the constant pressure or constant flow rate mode can be applied independently to the sample during data acquisition. Due to the modular design, components such as windows, seals and pistons can be interchanged optimising the cell for use with chemically aggressive (including ultra-supercritical) fluids. This development supports research initiatives in geology, energy and minerals, resource engineering, civil engineering, material sciences, biotechnology, and medical sciences. The cell is also extendable for use in neutron diffraction and tomographic experiments.

Comparative study of mechanical stress-induced flat-band voltage change in MOS capacitor and threshold voltage change in MOSFET fabricated on 4H-SiC (0001)

The impact of mechanical uniaxial stress on electrical characteristics of 4H-SiC (0001) n-type MOSFET (n-MOSFET) was systematically investigated by a mechanical 4-point bending method. Expected variation of field-effect mobility with stress was observed and for the first time, a direct relationship between uniaxial stress and significant change in threshold voltage (V th) on lateral SiC MOSFET was investigated systematically. The observed change of V th was as large as 40 mV with a stress of 170 MPa. By comparing with flat-band voltage (V fb), it was concluded that a change in V th mainly consists of change in V fb on n-MOS capacitor with mechanical stress. Even though the possible origins of such V fb change with stress are not clarified yet, they were suggested to be either the change in band alignment or the change in fixed charge density induced by electronic structure change.

Uniaxial compressive mechanical properties and stress–strain model for roller-compacted concrete with initial damage subjected to freeze–thaw cycles

Roller compacted concrete (RCC) often remains in a damage state as a result of improper vibrating compaction control, which makes it more susceptible to the action of freezethaw (FT) cycles in cold regions and thus results in the degradation of mechanical behaviors. In this paper, the influences of initial damage and FT cycles on the physical and mechanical behaviors of RCC were systematically examined through physical tests, including FT cycle tests, pore structure tests and uniaxial compressive tests. An in situ vibrating compaction procedure was employed in the experiment to accurately replicate the field compaction process for RCC under laboratory conditions, and the dynamic elasticity modulus (DEM) was adopted as the non-destructive testing (NDT) index to quantify the initial damage caused by improper RCC construction control. The results indicated that the higher values of initial damage and FT cycles exhibited a greater influence on the frost resistance and pore structure distribution. Remarkable attenuation of compressive strength and elastic modulus and an increase in peak strain were observed to occur in RCC when the initial damage degree exceeded 0.1 and the number of FT cycles exceeded 75. Finally, the uniaxial compressive stressstrain model was established through segmented linear regression analysis based on the Weibull-Lognormal model. The proposed model was validated to be effective and reasonable in predicting the mechanical properties of RCC under the combined effects of initial damage and FT cycles.

Covalent Immobilization of Collagen Type I to a Polydimethylsiloxane Surface for Preventing Cell Detachment by Retaining Collagen Molecules under Uniaxial Cyclic Mechanical Stretching Stress.

Surface modification of polydimethylsiloxane (PDMS) with an extracellular matrix (ECM) is useful for enhancing stable cell attachment. However, few studies have investigated the correlation between the stability of deposited ECM and cell behavior on the PDMS surfaces in external stretched cell culture systems. Herein, covalent collagen type I (Col)-immobilized PDMS surfaces were fabricated using 3-aminopropyl-trimethoxysilane, glutaraldehyde, and Col molecules. The immobilized collagen molecules on the PDMS surface were more stable and uniform than the physisorbed collagen. The cells stably adhered to the Col-immobilized surface and proliferated even under uniaxial cyclic mechanical stretching stress (UnCyMSt), whereas the cells gradually detached from the Col-physisorbed PDMS surface, accompanied by a decrease in the number of deposited collagen molecules. Moreover, the immobilization of collagen molecules enhanced cell alignment under the UnCyMSt. This study reveals that cell adhesion, proliferation, and alignment under the UnCyMSt can be attributed to the retention of collagen molecules on the PDMS surface.

Study of magnetoelastic demagnetization of locally magnetized steel

To improve the accuracy of determining mechanical stresses in steel by the method of magnetoelastic demagnetization (magnetoelastic memory), the magnetoelastic sensitivity of the material to elastic stresses is additionally measured by applying or removing an additional load of a known value. We present the results of studying the magnetoelastic demagnetization of locally magnetized steel by varying stresses of the uniaxial tension or compression against a background of the base load. The magnetoelastic sensitivity of the steel in a loaded state to variable stresses has been assessed. It is shown that the determination of the magnetoelastic sensitivity of the steel to variable loads makes it possible to improve the accuracy of estimating base stresses in the steel structure using magnetoelastic methods. It is revealed that a decrease in the strength of the magnetic scattering field of the local residual magnetization (LRM) of the steel after variable loading (or unloading) exponentially depends on the magnitude of the base stresses. The possibility of controlling the uniaxial mechanical stresses in steel structures in the magnetoelastic memory mode which is based on the dependence of the strength of magnetic scattering field of the local residual magnetization of the steel on the uniaxial stresses is shown. A method for monitoring uniaxial stresses in the elements of steel structures by the method of magnetoelastic memory is proposed using the measured magnetoelastic sensitivity of the material. The results obtained can be used in the development of a method for monitoring the stress-strain state of steel structures during operation under the simultaneous effect of static and dynamic loads.

Comparison of the domain structure reaction of various ferromagnetic microparticles under uniaxial mechanical stress

The results of studying the changes in the domain structure of a planar square microparticle with size 7.5 x 7.5 x 0.04 μm under uniaxial mechanical stress is presented. Microparticles were made from the following materials: permalloy (18% Fe, 82% Ni), permendur (50% Co, 50% Fe), halfenol (16% Ga, 84% Fe), Ni, terfenol (Tb0.3Dy0.7Fe1.92). The conclusions about the promising of using these materials for fabrication microsensors for stress detection and for fabrication straintronic devices for processing and storing information were made. Keywords: magnetoelastic effect, magnetic force microscopy, planar ferromagnetic particles, domain structure.

Сравнение реакции доменной структуры различных ферромагнитных микрочастиц на действие одноосного механического напряжения

There is presented results studying of changes of the domain structure of a planar square microparticle with dimensions 7.5 × 7.5 × 0.04 μm under uniaxial mechanical stress. Microparticles were made from following materials: permalloy (18% Fe, 82% Ni), permendur (50% Co, 50% Fe), halfenol (16% Ga, 84% Fe), Ni, terfenol (Tb0.3Dy0.7Fe1.92). It was concluded about promising of using these materials for creating microsensors of mechanical stress and for creating straintronic devices for processing and storing information.

Inverse identification of pipeline steel mechanical state by means of coupled magnetic measurements and artificial neural networks

Artificial neural networks are widely used to develop models able to predict properties of interest by learning and establishing relationships between inputs and outputs of a system. It is particularly relevant for the inversion process in the framework of Non-Destructive Testing (NDT) involving strongly non-linear and non-monotonic behavior and/or saturations. The case-study considered in this work is a magnetic material subjected to uniaxial mechanical stress, plastic strain and magnetic field. An Artificial Neural Networks (ANN) model is proposed to predict the corresponding remanent magnetization, coercive field and the maximum magnetization as target properties. A series of experimental data made of various magneto-mechanical measurements are used to train, evaluate and validate the ANN model. The proposed model suitably predicts the magnetic properties of a second specimen of the material in the same magnetic field, plastic strain and stress ranges as the first specimen. An inverse ANN is then proposed to evaluate the mechanical loading and the plastic strain from the magnetic signature. Unique and accurate solutions are found that proves the relevance of machine learning approach in such NDT application.

Microscopic Simulation of the RF Performance of SiGe HBTs With Additional Uniaxial Mechanical Stress

A very detailed investigation of high-speed silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) showed an underestimation of the measured peak cutoff frequency by simulations with a hydrodynamic (HD) model. It was speculated that this might be due to a breakdown of the HD approximation or unknown additional mechanical stress. We repeated those simulations with the more fundamental Boltzmann transport equation (BTE) based on the same device model (doping profiles, 2-D geometry, parasitics, and so on) and obtained almost similar results showing that this failure was not due to a breakdown of the HD approximation. Since additional uniaxial stress along the direction of the lateral base has been shown to increase the cutoff frequency, we investigated this effect. We found by 2-D device simulations that the increase in the peak cutoff frequency is rather small, and at high stress levels, it even decreases, if the uniaxial stress is applied homogenously. This is due to the reduction of the conductivity of the highly doped collector layer by the stress. If the stress is limited to the intrinsic transistor, the increase in the cutoff frequency is monotonic with growing stress. On the other hand, the collector current for a given base–emitter voltage also increases with stress leading to an overestimation of the collector current compared with the measurements. If this increase is corrected by a slight decrease in the germanium profile, the gain in the peak cutoff frequency is lost. Thus, the underestimation of the peak cutoff frequency cannot be explained by an additional homogeneous uniaxial stress in the intrinsic transistor.

The stability of 3D skyrmions under mechanical stress studied via Monte Carlo calculations

Using Monte Carlo (MC) simulations, we study the skyrmion stability/instability as a response to uniaxial mechanical stresses. Skyrmions emerge in chiral magnetic materials as a stable spin configuration under external magnetic field B→ with the competition of ferromagnetic interaction and Dzyaloshinskii–Moriya interaction (DMI) at low temperature T. Skyrmion configurations are also known to be stable (unstable) under a compressive stress applied parallel (perpendicular) to B→. To understand the origin of such experimentally confirmed stability/instability, we use the Finsler geometry modeling technique with a new degree of freedom for strains, which plays an essential role in DMI being anisotropic. We find from MC data that the area of the skyrmion state on the B−T phase diagram increases (decreases) depending on the direction of applied stresses, in agreement with reported experimental results. This change in the area of the skyrmion state indicates that skyrmions become more (less) stable if the tensile strain direction is parallel (perpendicular) to B→. From the numerical data in this paper, we find that the so-called magneto-elastic effect is suitably implemented in the effective DMI theory with the strain degree of freedom without complex magneto-elastic coupling terms for chiral magnetic materials. This result confirms that experimentally-observed skyrmion stability and instability are caused by DMI anisotropy.

An Extension of the Vector-Play Model to the Case of Magneto-Elastic Loadings

The influence of mechanical stress on the magnetic hysteretic behavior is modeled through the association of a reversible simplified multiscale approach, and a macroscopic energy-based magnetic hysteresis model in a vector-play form. A phenomenological description of the dissipation parameters under mechanical stress is proposed. The non-monotonic effect of tensile stress on the magnetic permeability is modeled using a second-order development in the magneto-elastic energy. Material parameters for both reversible and irreversible behavior are identified from experimental characterization under mechanical stress performed on a DC04 electrical steel. The experimental tests include anhysteretic and hysteretic measurements. Modeling results of the anhysteretic magnetic permeability, the coercive field, and the remanent induction under several levels of peak magnetic field and uniaxial mechanical stress are satisfactorily compared with those obtained experimentally. The model is shown to reasonably predict the hysteresis losses under tensile and compressive stress, as well as the response of the material under a complex magnetic field waveform with harmonic content.

Determination of the steel axial stresses in memory mode by the exponential law of magnetoelastic demagnetization

Magnetic and magnetoelastic methods of stress control are based on changes in the magnetic parameters of steel upon deformation. However, the magnetic properties of different steel grades, and even of the same grade in different heats may differ noticeably. The inhomogeneity of the magnetic and magnetoelastic properties of steel attributed to variations in the chemical composition, as well as in the modes of rolling and heating during manufacture affects the accuracy of stress control being a common disadvantage of magnetoelastic methods used for monitoring the stress-strain state of steel structures. The goal of the study is to consider the possibility of monitoring uniaxial mechanical stresses in steel structures in the «magnetoelastic memory» mode, based on H(σ) dependence of the strength of magnetic field of scattering local remanent magnetization of steel on the uniaxial stresses. The exponential function is shown to provide a satisfactory description of the experimental dependence of the strength of the magnetic field of scattering of the permanently magnetized 17G1S and 15KhSND steels on the stresses induced in steels by tension, compression, and impact. To improve the accuracy of the control, we propose to introduce the magnetoelastic sensitivity of steel (MSS) into the accepted form of the exponential dependence H(σ). A way to MSS determination not only on laboratory samples under ideal conditions, but directly on the construction under control (which reduces the errors of the control attributed to variations in the magnetic and magnetoelastic properties of steels) is considered. To implement the proposed procedure, prototypes of the devices for static and dynamic local loading of metal structure elements have been developed and manufactured. The devices have undergone a pilot test when monitoring the stress-strain state of the load-bearing beams of an automobile overpass. Using the developed devices, a local dosed loading with a hemispherical indenter was carried out through shock or static loading of a pre-magnetized region of the structure resulted in a decrease in the intensity of the magnetic field of scattering. A procedure for monitoring uniaxial stresses in steel structure elements by the method of magnetoelastic «memory» is proposed taking into account the measured magnetoelastic sensitivity of their material.

3‐D base force element method on meso‐damage analysis for recycled concrete

AbstractThe 3‐D base force element method (BFEM) for damage problems is proposed, which is applied to analyze the damage mechanism of recycled aggregate concrete (RAC). A piecewise curve damage constitutive model is given to simulate the constitutive relationships of RAC phases. A spatial random aggregate model of RAC is proposed. 3‐D numerical simulations of RAC under uniaxial mechanical stress are carried out. The macroscopic stress–strain relationship and failure process of RAC under uniaxial stress based on the 3‐D BFEM are obtained. The numerical results show a good consistency with the experimental results. This illustrates that the numerical simulation can reflect the nonlinearity deformation, stress redistribution, and crack propagation process of RAC. In addition, the influence of recycled aggregate replacement percentage on strength and elastic modulus is investigated. The results show that the content proportion of recycled aggregate has a great effect on RAC, which have to be considered in the analysis and the application of RAC.

Specificity of the electrophysical properties of elastically deformed p-type germanium

The influence of directional elastic compression deformation on the electrophysical properties of p-type germanium single crystals was investigated. The dependences of the Hall coefficient on the magnetic field strength on samples of different crystallographic orientations in the absence and in the presence of uniaxial mechanical stress were measured at two temperatures (room temperature and liquid nitrogen temperature). On the same samples, the tensoresistance and longitudinal tensomagnetoresistance were studied in a wide range of mechanical stresses (0≤X≤1GPa). The presence of anisotropy of galvanomagnetic effects in p-Ge was revealed both in the absence of deformation and under very strong mechanical loads. Experiments on measuring the longitudinal tensomagnetoresistance make it possible to conclude that the isoenergetic surfaces in p-Ge, which arise as a result of directional elastic compression deformation, cannot be considered as perfect ellipsoids of revolution, at least in the investigated X range.

INVESTIGATING THE IMPACT OF AN EXTERNAL INFLUENCE ON THE DYNAMIC BEHAVIOR OF DISLOCATIONS IN SILICON CRYSTALS

The results of studying of the influence of a constant magnetic field on the dynamic behavior of dislocations in the crystalline block of an interferometer subsequently subjected to uniaxial mechanical tensile stress along the crystallographic axis of silicon are presented. The periodicity of the dilatation moire image after these influences, the average means free path of a dislocation in a crystal (block), the amount of slip, the average density of dislocations along the slip line, the relative deformation, and Young's modulus are calculated. To study the effect of a stable magnetic field on the dynamic behavior of dislocations in silicon crystals, a special three-block X-ray interferometer was fabricated in one of the blocks, and dislocations were introduced using the technique proposed by us. The experiments were carried out for various values of the magnetic field induction and mechanical stress. It is shown that the sequential action of these external influences leads to an increase in the starting stress, a decrease in the velocity of dislocation movement, a delay in the onset of dislocation movement, and the appearance of a hardening phenomenon. Experiments show that the displacement mobility characteristics are especially sensitive when the modulus of the magnetic induction vector reaches a certain threshold value for a given sample. It was shown that, in a sample containing silicon dislocations, the magnetic memory that appears after storage in a magnetic field is short-lived. It is found that the speed of movement of a dislocation in a magnetic field processed by a magnetic field, "then" subjected to mechanical stress (stretching), changes, but in practice the energy of its activation does not change. A theoretical analysis of the above experimental results is carried out, their scientific substantiation is given, all the factors associated with the phenomena observed in experiments are revealed.

X-ray Interferometric Study of the Effect of a Constant Magnetic Field on the Dynamic Behavior of Dislocations in Silicon Crystals

The results of studying the influence of a constant magnetic field on the dynamic behavior of dislocations in the crystal block of an interferometer, which is in a magnetic field and subsequently subjected to uniaxial mechanical tensile stress along the crystal axis [1 $$\bar {1}$$ 0], are presented. It is experimentally proved that in silicon crystals that have undergone preliminary magnetic treatment, a hardening effect is observed. The magnetic memory that appears in silicon samples with dislocations after exposure to a magnetic field is shown to be short term.

Thermally Induced Magnetoelastic Effect in Planar CoNi Microparticles on Lithium Niobate

The temperature effect on the magnetization distribution in planar CoNi microparticles deposited on hexagonal single‐crystal lithium niobate has been studied. The transition of the magnetization distribution of such microparticles from multidomain to quasiuniform state by changing the substrate temperature has been demonstrated. It is established that the transition into the quasiuniform state occurs upon heating/cooling of the sample with respect to the deposition temperature of the microparticles. This is due to the noticeable difference in the thermal expansion coefficients along various crystallographic axes of lithium niobate. The uniaxial mechanical stresses are induced in the CoNi microparticles deposited on the crystal at the thermal change in the crystal size. The stresses induced in this manner are determined. In addition, this makes it possible to reduce the external magnetic field required for magnetization switching up to two times.

Mobility enhancement by mechanical uniaxial stress on 4H-SiC (0001) lateral metal-oxide-semiconductor field-effect-transistor

We investigated the impact of the mechanical uniaxial strain on the inversion channel mobility of lateral n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) on 4H-SiC(0001). We used custom-designed bend-holders to apply a tensile and compressive stress to the chip after MOSFET fabrication. The behavior of mobility with the two different channel directions and was investigated on the bend directions and with the tensile and compressive stress. We found that the inversion channel mobility effectively increases with the uniaxial compressive stress of the perpendicular configuration which is the drain current flow perpendicular to the bend direction. From the temperature dependence of mobility, we deduced that the enhancement of mobility is attributed to the reduction of the effective mass in 4H-SiC by introduced stress.