Uniaxial Components Research Articles

Compressive mechanical behavior and failure of the pig bone rib and correlation to its morphological characteristics

The mechanical and failure properties of bones are well documented from a structural perspective. By contrast, less is known about those properties from the material and microstructural point of view. This study combines mechanical compression of pig bone rib slices, comprising both cortical and trabecular components, together with digital image correlation records. For monotonic loading, the three classical phases of the bone response, namely elastic, plateau/softening, and hardening are observed. The first phase is characterized by a uniform state of deformation which becomes heterogeneous in the following phases, through the appearance of well-defined domains. Failure is initiated in the trabecular bone at the interfaces between those domains, where the prevailing heterogeneous deformation indicates the operation of shear or uniaxial strain components. From a microstructural point of view, using micro-CT (computed tomography) it was noticed that sub-regions with relatively combined low BV/TV (bone material volume divided by total volume) and anisotropy, whose structure is oriented perpendicularly to the loading direction, are prone to failure at the interface between heterogeneously deforming domains. A globally similar behavior is reported for aluminum foams without cortical components.Repeated loading cycles reveal a previously un-noticed response of the bone, consisting of elastic shakedown without ratcheting, with diminishing hysteretic load-displacement loops, which indicate that most of the damage is achieved during the first loading cycle.The observations reported in this paper are believed to provide important physical evidence to be included in numerical models at the verification and/or validation stages.

Complex Strain Scapes in Reconstructed Transition-Metal Dichalcogenide Moiré Superlattices.

We investigate the intrinsic strain associated with the coupling of twisted MoS2/MoSe2 heterobilayers by combining experiments and molecular dynamics simulations. Our study reveals that small twist angles (between 0 and 2°) give rise to considerable atomic reconstructions, large moiré periodicities, and high levels of local strain (with an average value of ∼1%). Moreover, the formation of moiré superlattices is assisted by specific reconstructions of stacking domains. This process leads to a complex strain distribution characterized by a combined deformation state of uniaxial, biaxial, and shear components. Lattice reconstruction is hindered with larger twist angles (>10°) that produce moiré patterns of small periodicity and negligible strains. Polarization-dependent Raman experiments also evidence the presence of an intricate strain distribution in heterobilayers with near-0° twist angles through the splitting of the E2g1 mode of the top (MoS2) layer due to atomic reconstruction. Detailed analyses of moiré patterns measured by AFM unveil varying degrees of anisotropy in the moiré superlattices due to the heterostrain induced during the stacking of monolayers.

Mechanical Properties of Prismatic Li-Ion Batteries—Electrodes, Cells, and Stacks

Abstract Mechanical abusive loadings, as an inevitable consequence of road accidents, can damage the embedded energy storage system in an electric vehicle and deform its constitutive parts, e.g., the lithium-ion batteries. Therefore, to study the mechanical responses of these batteries and avoid expensive testing equipment and rigorous safety percussions, researchers are propelled toward utilizing numerical models. Computationally cost-efficient homogenized finite element models that represent the whole battery in the form of a uniform medium are the most feasible solution, especially in large-scale battery stacks simulations. Compared to the other form factors of the batteries, prismatic cells have been understudied even though they have higher packaging efficiency, by making optimal use of space. In this article, a comprehensive homogenization and failure calibration method was developed for these prismatic cells. The homogenization was done through extensive uniaxial components tests of the jellyroll and the shell casing. In addition, biaxial tensile tests and simulations were used to calibrate strain-based failure criteria for the components. The calibrated homogenized model is validated in various punch loading scenarios and used in the characterization of the load–displacement responses and failure modes of the stacked cell configurations. In the stacked simulations, due to the cushion-like behavior of the other cells, the failure happens in higher values of displacement compared to a single cell. However, the normalized intrusion percentages for the battery stacks are lower compared to a single battery cell. This emphasizes the importance of the safety assessment of an electric vehicle based on the failure analysis of the battery stacks rather than a single cell. This goal would be feasible through simulations of only homogenized cell models in the stacked configurations, which are elaborated in this article for prismatic cells.

A Magnetic Field Imaging System Based on TMR Sensors for Banknote Recognition

The high sensitivity and MEMS-compatible process of tunneling magnetoresistance (TMR) sensors provide great opportunities to develop high-resolution magnetic field detection and imaging systems. In this work, we designed a magnetic field imaging (MFI) system based on TMR sensors to detect the uniaxial magnetic field components of banknotes including US dollars (USD) and Chinese Yuan (CNY), which clearly reveals the distribution of magnetic anti-counterfeiting markers inside the banknotes. Measurement results of the USD show that the magnetic ink signal is around μT level, and the person portraits on banknotes can be revealed by the sensor signals. The testing results of the CNY banknotes indicate magnetic color-shifting ink images, as well as a clear magnetic anti-counterfeiting thread. Different from the traditional optical detection, magnetic detection provides unique signals and identification methods. With a satisfactory recognition rate, the proposed MFI system based on TMR sensors demonstrates its promising potential forgery detection and denomination identification of banknotes.

Dynamic magnetic properties of amorphous Fe80B20 thin films and their relation to interfaces

We present a ferromagnetic resonance study of the dynamic properties of a set of amorphous Fe-B films deposited on Corning Glass® and MgO (001) substrates, either with or without capping. We show that the in plane anisotropy of the MgO grown films contains both uniaxial and biaxial components whereas it is just uniaxial for those grown on glass. The angular dependence of the linewidth strongly differs in terms of symmetry and magnitude depending on the substrate and capping. We discuss the role of the interfaces on the magnetization damping and the generation of the anisotropy. We obtained values of the intrinsic damping parameters comparable to the lowest ones reported for amorphous films of similar compositions.

Dynamic characterization of multi-component sensors for force and moment

Abstract. An improved set-up for the characterization of multi-component sensors for force and moment is presented. It aims at calibrating such sensors under continuous sinusoidal excitation. Special focus is put on the design of load masses and adapting elements to activate uniaxial force and moment components where possible. To identify the motion and acceleration of the load mass with 6 degrees of freedom, a photogrammetric measurement system is implemented in the existing set-up. Using the set-up described, different experiments are performed to analyse a commercial multi-component sensor and perform a parameter identification for its force components.

Use of Triaxial Accelerometry During the Dance Aerobic Fitness Test: Considerations for Unit Positioning and Implications for Injury Risk and Performance.

Injury incidence in dance is high, in large part due to the frequency of repetitive and complex movements that require the lower limb to absorb and utilize extreme forces. The aim of this study was to quantify the biomechanical demands of the Dance Aerobic Fitness Test (DAFT) via triaxial accelerometry and utilize it to compare loading at the cervical spine and distal aspect of the lower limb. University dancers (N = 26; age: 20.0 ± 1.5 years; height: 1.61 ± 0.08 m; body mass: 58.40 ± 6.20 kg) completed two trials (one familiarization and one experimental) of the DAFT, consisting of five incremental levels of dance performance. Micromechanical electrical systems (MEMS) accelerometry was used to calculate total accumulated PlayerLoad (PLTotal) and it's uniaxial (anteroposterior [PLAP], mediolateral [PLML], and vertical [PLV]) components for each level. MEMS units were positioned at cervical vertebra 7 (C7) and the center of gastrocnemius (LL). There was a significant main effect for each level, with loading increasing in relation to exercise duration. There was also a significant main effect for anatomical placement, with higher PLTotal (C7 = 41.05 ± 7.31 au; LL = 132.58 ± 35.70), PLAP (C7 = 12.96 ± 2.89 au; LL = 47.16 ± 13.18 au), and PLML (C7 = 10.68 ± 2.15; LL = 46.29 ± 12.62 au) at LL when compared to C7, with the converse relationship for PLV (LL = 20.05 ± 3.41 au; C7 = 44.89 ± 11.22 au). Significant interactions were displayed for all PL metrics. It is concluded that triaxial PlayerLoad was sensitive enough to detect increased loading associated with increases in exercise intensity, while lower limb accelerometer placement detected higher loading in all planes. The specificity in anatomical placement has practical implications, with lower limb accelerometry recommended to assess movement strategies in that location.

Blocking temperature of interacting magnetic nanoparticles with uniaxial and cubic anisotropies from Monte Carlo simulations

The low temperature behavior of densely packed interacting spherical single domain nanoparticles (MNP) is investigated by Monte Carlo simulations in the framework of an effective one spin model. The particles are distributed through a hard sphere like distribution with periodic boundary conditions and interact through the dipole dipole interaction (DDI) with an anisotropy energy including both cubic and uniaxial symmetry components. The cubic component is shown to play a sizable role on the value of the blocking temperature Tb only when the MNP easy axes are parallel to the cubic easy direction ([111] direction for a negative cubic anisotropy constant). The nature of the collective low temperature state, either ferromagnetic or spin glass like, is found to depend on the ratio of the anisotropy to the dipolar energies characterizing partly the disorder in the system.

Strain and carrier transport along dislocations

AbstractA significant increase of the drain current is verified if defined numbers and types of dislocations are present in the channel of MOSFETs. For pMOSFETs, analysed here, an enhancement by a factor of eight exists if mixed dislocations are placed in the channel. The drain current increase is caused by higher concentration and higher mobility of holes on dislocations. It is shown that cores of mixed dislocations possess uniaxial compressive strain components in the order of ε ≅ –0.1 which are significantly higher than in the strain field surrounding a dislocation. The exceptional high uniaxial strain results in dramatic alterations of the silicon band structure. Upward shifts of the upper valence bands appear forming a quantum wire. The generation of the quantum wire forces hole confinement along dislocations and generates a one‐dimensional hole gas (1DHG). Confinement and energy quantization are assumed to be most important for the increased carrier transport along dislocations. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Reexamination of the mean-field phase diagram of biaxial nematic liquid crystals: Insights from Monte Carlo studies.

Investigations of the phase diagram of biaxial liquid-crystal systems through analyses of general Hamiltonian models within the simplifications of mean-field theory (MFT), as well as by computer simulations based on microscopic models, are directed toward an appreciation of the role of the underlying molecular-level interactions to facilitate its spontaneous condensation into a nematic phase with biaxial symmetry. Continuing experimental challenges in realizing such a system unambiguously, despite encouraging predictions from MFT, for example, are requiring more versatile simulational methodologies capable of providing insights into possible hindering barriers within the system, typically gleaned through its free-energy dependences on relevant observables as the system is driven through the transitions. The recent paper from this group [Kamala Latha et al., Phys. Rev. E 89, 050501(R) (2014)], summarizing the outcome of detailed Monte Carlo simulations carried out employing an entropic sampling technique, suggested a qualitative modification of the MFT phase diagram as the Hamiltonian is asymptotically driven toward the so-called partly repulsive regions. It was argued that the degree of (cross) coupling between the uniaxial and biaxial tensor components of neighboring molecules plays a crucial role in facilitating a ready condensation of the biaxial phase, suggesting that this could be a plausible factor in explaining the experimental difficulties. In this paper, we elaborate this point further, providing additional evidence from curious variations of free-energy profiles with respect to the relevant orientational order parameters, at different temperatures bracketing the phase transitions.

Effect of magnetic anisotropy on spin-dependent thermoelectric effects in nanoscopic systems

Conventional and spin-related thermoelectric effects in electronic transport through a nanoscopic system exhibiting magnetic anisotropy $-$with both uniaxial and transverse components$-$ are studied theoretically in the linear response regime. In particular, a magnetic tunnel junction with a large-spin impurity $-$either a magnetic atom or a magnetic molecule$-$ embedded in the barrier is considered as an example. Owing to magnetic interaction with the impurity, conduction electrons traversing the junction can scatter on the impurity, which effectively can lead to angular momentum and energy exchange between the electrons and the impurity. As we show, such processes have a profound effect on the thermoelectric response of the system. Specifically, we present a detailed analysis of charge, spin and thermal conductance, together with the Seebeck and spin Seebeck coefficients (thermopowers). Since the scattering mechanism also involves processes when electrons are inelastically scattered back to the same electrode, one can expect the flow of spin and energy also in the absence of charge transport through the junction. This, in turn, results in a finite spin thermopower, and the magnetic anisotropy plays a key role for this effect to occur.

A complete description of polarization and transmission of nonnormal incident rays in a uniaxial birefringent plate with arbitrary optic axis

A complete description of polarization and transmission of light in a uniaxial birefringent plate with arbitrary crystal axis direction is detailedly presented. A general case with nonnormal incidence in spatial domain is considered. The universal theoretical model is build up by referring to all the impact factors including the incident angle, the incident wavelength, the azimuth angle, and the optical axis direction of crystal plate. The simulated results show that the ordinary ray and extraordinary ray in birefringent crystal have unique polarization direction and distinct energy transmission property, respectively. The explicit representation in this paper allows a comprehensive analysis and determination for the polarization performance and transmission characteristics of light in various uniaxial birefringent components, and especially it is simple and clear in physical picture.

Automation of flexible components virtual prototyping: methodology, tools and validation

3D CAD systems are powerful tools for modelling rigid bodies but they are not adequate in order to model flexible material components, especially if a realistic simulation of physical behaviour is required as in virtual prototyping. This paper describes the methodology used to develop a knowledge-based system in order to automatically create virtual prototypes of uniaxial flexible components like cables, pipes and wires. The method has been translated in an operative design software system for metallic-reinforced elastomer hoses. The resulting VP tool integrates the 3D CAD technology and suitable structural simulation methods. The robustness of software system has been verified and errors are assessed. A dedicated experimental set-up has been realised in order to compare the virtual results with the real component behaviour. The system has been applied in the design of multifunctional agricultural machines showing reduction of physical prototypes and the lead-time due.

High sensitivity of O17 NMR to p-d hybridization in transition metal perovskites: First principles calculations of large anisotropic chemical shielding

A first principles embedded cluster approach is used to calculate O chemical shielding tensors, σ̂, in prototypical transition metal oxide ABO3 perovskite crystals. Our principal findings are (1) a large anisotropy of σ̂ between deshielded σx≃σy and shielded σz components (z along the Ti–O bond); (2) a nearly linear variation, across all the systems studied, of the isotropic σiso and uniaxial σax components, as a function of the B-O-B bond asymmetry. We show that the anisotropy and linear variation arise from large paramagnetic contributions to σx and σy due to virtual transitions between O(2p) and unoccupied B(nd) states. The calculated isotropic δiso and uniaxial δax chemical shifts are in good agreement with recent BaTiO3 and SrTiO3 single crystal O17 NMR measurements. In PbTiO3 and PbZrO3, calculated δiso are also in good agreement with NMR powder spectrum measurements. In PbZrO3, δiso calculations of the five chemically distinct sites indicate a correction of the experimental assignments. The strong dependence of σ̂ on covalent O(2p)-B(nd) interactions seen in our calculations indicates that O17 NMR spectroscopy, coupled with first principles calculations, can be an especially useful tool to study the local structure in complex perovskite alloys.

Detailed transport investigation of the magnetic anisotropy of (Ga,Mn)As

This paper discusses transport methods for the investigation of the (Ga,Mn)As magnetic anisotropy. Typical magnetoresistance behaviour for different anisotropy types is discussed, focusing on an in depth discussion of the anisotropy fingerprint technique and extending it to layers with primarily uniaxial magnetic anisotropy. We find that in all (Ga,Mn)As films studied, three anisotropy components are always present. The primary biaxial along ([100] and [010]) along with both uniaxial components along the and [010] crystal directions which are often reported separately. Various fingerprints of typical (Ga,Mn)As transport samples at 4 K are included to illustrate the variation of the relative strength of these anisotropy terms. We further investigate the temperature dependence of the magnetic anisotropy and the domain wall nucleation energy with the help of the fingerprint method.

Magnetocrystalline anisotropy and magnetization reversal inGa1−xMnxPsynthesized by ion implantation and pulsed-laser melting

We report the observation of ferromagnetic resonance (FMR) and the determination of the magnetocrystalline anisotropy in (100)-oriented single-crystalline thin film samples of ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{P}$ with $x=0.042$. The contributions to the magnetic anisotropy were determined by measuring the angular and the temperature dependencies of the FMR resonance fields and by superconducting quantum interference device magnetometry. The largest contribution to the anisotropy is a uniaxial component perpendicular to the film plane; however, a negative contribution from cubic anisotropy is also found. Additional in-plane uniaxial components are observed at low temperatures, which lift the degeneracy between the in-plane [011] and $[01\overline{1}]$ directions as well as between the in-plane [010] and [001] directions. Near $T=5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the easy magnetization axis is close to the in-plane $[01\overline{1}]$ direction. All anisotropy parameters decrease with increasing temperature and disappear above the Curie temperature ${T}_{C}$. A consistent picture of the magnetic anisotropy of ferromagnetic ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{P}$ emerges from the FMR and magnetometry data. The latter can be successfully modeled when both coherent magnetization rotation and magnetic domain nucleation are considered.

22.1: Wide Field of View Compensation Scheme for Cube Polarizing Beam Splitters

AbstractA novel compensation scheme for correcting geometrical depolarization affects in cube polarizing beamsplitters is presented. The low cost, oblique, uniaxial birefringent components used can significantly improve system performance, e.g. the contrast of LCoS projection systems. The scheme is generally applicable to all mirror‐like beamsplitting elements whose performance can be improved by minimizing geometric polarization mixing.

Modal transmission-line theory of three-dimensional periodic structures with arbitrary lattice configurations.

The scattering of waves by multilayered periodic structures is formulated in three-dimensional space by using Fourier expansions for both the basic lattice and its associated reciprocal lattice. The fields in each layer are then expressed in terms of characteristic modes, and the complete solution is found rigorously by using a transmission-line representation to address the pertinent boundary-value problems. Such an approach can treat periodic arbitrary lattices containing arbitrarily shaped dielectric components, which may generally be absorbing and have biaxial properties along directions that are parallel or perpendicular to the layers. We illustrate the present approach by comparing our numerical results with data reported in the past for simple structures. In addition, we provide new results for more complex configurations, which include multiple periodic regions that contain absorbing uniaxial components with several possible canonic shapes and high dielectric constants.

Relation between exchange anisotropy and magnetization reversal asymmetry inFe/MnF2bilayers

The angular dependence of the magnetic anisotropy of exchange biased $\mathrm{Fe}/{\mathrm{MnF}}_{2}$ bilayers was measured. Below the N\'eel temperature of the antiferromagnetic ${\mathrm{MnF}}_{2}$ layer, an exchange anisotropy is observed which consists of unidirectional, uniaxial, threefold and fourfold symmetry components. The threefold exchange anisotropy term is responsible for the asymmetric magnetization reversal process recently observed in this system.

Effect of gauge length on uniaxial deformation-energy components of copper and brass sheets

Deformation-energy components of copper and brass sheets have been studied by the uniaxial tensile testing of different test pieces having various gauge lengths. The total energy required to tear the specimens was assumed to be composed of elastic, uniform plastic and tearing or post-uniform deformation regimes. The total and elastic energy values were obtained directly from the load–extension curves for each specimen. Tearing and uniform plastic energy values were calculated by plotting the total energy divided by the specimen cross-sectional area against the initial gauge length of the specimens. In this plot, a straight line is obtained the slope of which gives the summation of the elastic and plastic energy per unit volume and its intercept gives the value of tearing energy. The results indicate that while the elastic and plastic energy ratios increased with increasing gauge length the tearing energy ratios showed a decreasing trend. The experimental energy ratios have been compared with theoretical ones obtained from the basic equations of uniaxial deformation.