Relative Orientation Research Articles

Biceps femoris muscle-tendon strain during an entire overground sprint acceleration: a biomechanical explanation for hamstring injuries in the acceleration phase

ABSTRACT The objectives of this study were to analyse the peak muscle-tendon (MT) strain of the hamstring during an entire acceleration sprint overground and examine their relationship with relative joint angles and segment orientation in the sagittal plane, which are the direct causes of MT strain. Kinematic data were recorded using a 3D inertial motion capture system in 21 male semi-professional soccer players during 40-metre overground sprint. Scaled musculoskeletal models were used to estimate peak MT strain in the hamstring over 16 steps. Biceps femoris long head (BFLH) exhibited the largest peaks in MT strain compared to semitendinosus (ST) and semimembranosus (SM) muscles across all the steps, with its overall strain decreased as the number of steps and maximum speed increased. Hip flexion angle was found to be a strong predictor (p < 0.001) of joint angles, being the orientation of the pelvis in the sagittal plane of the segment with the greatest influence (p < 0.001) on the peak MT strain of BFLH during sprinting. The current study provides a biomechanical explanation for the high proportion of hamstring injuries in the acceleration phase of sprinting.

AlN and Nb(C,N) Composite Precipitation Behaviors and Their Effects on Austenite Grain Growth in SCr420H High‐Temperature Carburized Gear Steel

The effects of nitrogen (N) and niobium (Nb) contents on the precipitation behaviors of AlN, Nb(C,N), and AlN‐Nb(C,N) precipitates and austenite grain growth during the pseudo‐carburizing process are investigated for the carburized steel SCr420H. The results indicate that an increase of N content from 0.011% to 0.019% leads to the emergence of fine and uniform austenite grain structure in the sample while being held at 930 °C for 6 h, which is attributed to a notable rise in the number density of AlN and a decrease in the coarsening rate of AlN. In the steel containing 0.023% Nb, the composite precipitates AlN‐Nb(C,N) play a primary role in the pinning effect on austenite grains growth. The isolated Nb(C,N) and AlN precipitates have minor pinning effects due to their very low volume fractions. Nb(C,N) cap forming on AlN substrate obeys the Shoji–Nishiyama orientation relationship. The favorable lattice matching between AlN and Nb(C,N) and accelerated coarsening rate of Nb(C,N) cap decrease hindrances to the nucleation, growth, and coarsening of Nb(C,N) on AlN substrate. Meanwhile, these simultaneous effects also suppress the same processes for the isolated Nb(C,N) in the matrix.

Direct observation and characterization of a novel long period stacking ordered phase in GH4169 alloy

As is widely recognized, the Long Period Stacking Ordered (LPSO) phase is an important strengthening phase in the rare earth magnesium alloys. The LPSO phase not only enhances the strength of the alloy, but also improves its plasticity, thereby effectively addressing the strength-ductility trade-off phenomenon. Therefore, the preparation of metallic materials containing LPSO phase provides a new idea for designing a new generation of high-strength and high-toughness alloys. In present study, A novel nano-sized LPSO phase is observed and characterized for the first time in GH4169 nickel-based alloy. The results show that the stacking sequence of the LPSO phase is ABCBCBA, which indicates that this LPSO phase has a 6H structure. Meanwhile, the orientation relationships between LPSO phase and the Ni matrix are (11–1)γ//(0006)LPSO and [011]γ//[2-1-10]LPSO.

Simultaneous Calibration of Multiple Cameras and Generation of Omnidirectional Images

Abstract. Omnidirectional images are increasingly being used in various areas, such as urban mapping, virtual reality, agriculture, and robotics. These images can be generated by different acquisition systems, including multi-camera systems, which can acquire higher-resolution images. Stitching techniques are often used and can be suitable for non-metric applications, but rigorous photogrammetric processing is recommended when having more accurate requirements. The main challenges related to this kind of product are the system calibration and the generation of the final omnidirectional images. When using multi-camera systems, the displacement of the cameras' perspective centres can affect the generation of the omnidirectional images and the resulting accuracy. A common approach to minimising the resulting parallax error is to establish a value for the projection cylinder radius as close as possible to the object's depth. This work proposes a highly accurate simultaneous calibration technique for multiple camera systems using self-calibrating bundle adjustment with constraints of stability of the relative orientation parameters. These parameters are later used to generate a projecting cylindrical surface, maintaining the original camera perspective centres and relative orientation angles. The experiments show that using constraints improved both the calibration results and the final omnidirectional images. Residual mismatches between points in overlapping areas are subpixel.

Expanded Stability of Layered SnSe-PbSe Alloys and Evidence of Displacive Phase Transformation from Rocksalt in Heteroepitaxial Thin Films.

Bulk PbSnSe has a two-phase region, or miscibility gap, as the crystal changes from a van der Waals-bonded orthorhombic 2D layered structure in SnSe-rich compositions to the related 3D-bonded rocksalt structure in PbSe-rich compositions. This structural transition drives a large contrast in the electrical, optical, and thermal properties. We realize low temperature direct growth of epitaxial PbSnSe thin films on GaAs via molecular beam epitaxy using an in situ PbSe surface treatment and show a significantly reduced two-phase region by stabilizing the Pnma layered structure out to Pb0.45Sn0.55Se, beyond the bulk limit around Pb0.25Sn0.75Se at low temperatures. Pushing further, we directly access metastable two-phase films of layered and rocksalt grains that are nearly identical in composition around Pb0.50Sn0.50Se and entirely circumvent the miscibility gap. We present microstructural and compositional evidence for an incomplete displacive transformation from a rocksalt to layered structure in these films, which we speculate occurs during the sample cooling to room temperature after synthesis. In situ temperature-cycling experiments on a Pb0.58Sn0.42Se rocksalt film reproduce characteristic attributes of a displacive transition and show a modulation in electronic properties. We find well-defined orientation relationships between the phases formed and reveal unconventional strain relief mechanisms involved in the crystal structure transformation using transmission electron microscopy. Overall, our work adds a scalable thin film integration route to harness the dramatic contrast in material properties in PbSnSe across a potentially ultrafast crystalline-crystalline structural transition.

Investigation on the correlation between grain boundary character distribution and precipitate behavior in T91 ferritic/martensitic steel

In the present study, the relationship between microstructure, grain boundary character distribution (GBCD) and precipitate behavior in T91 steel was investigated via a series of thermomechanical treatments (TMTs). The experimental results revealed that subjecting the steel to cold-rolling (CR) with a deformation of 15–30% followed by tempering at 750 °C for 1 h caused the microstructure of T91 steel to transition from the typical lath martensite structure to a uniform polygonal ferrite, resulting in a change in the GBCD. Specifically, the proportion of random grain boundaries for the ferritic structure was significantly higher than that for the martensitic structure. The M23C6 carbide appeared as irregular polygons and precipitated within the ferrite grains, while it exhibited a rod-like shape and precipitated at the martensitic boundaries. Additionally, the orientation relationship (OR) between M23C6 carbide and the adjoining matrix transformed from the double Kurdjumov-Sachs (DKS) relation to (112) M23C6 // (110) ferrite and 201¯M23C6 // [012] ferrite. The change of OR resulted in a higher coarsening rate of M23C6 carbides precipitated in ferrite compared to those precipitated at martensitic boundaries.

Effects of 1:5H-type Cu-rich phase around grain boundary on cell boundary phase and squareness of the demagnetization curve in sintered Sm2Co17-type magnets

The unique cellular structure of Sm2Co17-type magnets is responsible for their outstanding magnetic properties. However, the cell boundary phase around grain boundaries is few, and cannot form a complete cellular structure. This study explores the microstructure and microchemistry of the grain interiors and grain boundary regions in both the solid solution precursor and the final magnet. The Cu-rich phase precipitates around grain boundaries in the solid solution precursor, and it remains present in the final magnet. The Cu-rich phase is not present as a standalone grain boundary phase, rather, it possesses a hexagonal CaCu5-type crystal structure and demonstrates a coherent orientation relationship with the surrounding matrix. The Cu-rich phase inhibits cellular structure formation nearby, while boosting Cu content in the cell boundary phase at the grain boundary regions in the final magnet. The formation of a Cu-rich phase around the grain boundary increases the heterogeneity of the domain wall pinning field in the final magnet, becoming an unfavorable factor for the improvement of the squareness of the demagnetization curve. These discoveries enhance our comprehension of the precipitated phase surrounding the grain boundary and its impact on the cellular structure and magnetic characteristics of the magnet.

Stability, Chemical Bonding, and Electron Lone Pair Localization in AsN at High Pressure by Density Functional Theory Calculations.

The covalent bonding framework of crystalline single-bonded cubic AsN, recently synthesized under high pressure and high temperature conditions in a laser-heated diamond anvil cell, is here studied by means of density functional theory calculations and compared to single crystal X-ray diffraction data. The precise localization of the nonbonding electron lone pairs and the determination of their distances and orientations are related to the presence of characteristic structural motifs and space regions of the unit cell dominated by repulsive electronic interactions, with the relative orientation of the electron lone pairs playing a key role in minimizing the energy of the structure. We find that the vibrational modes associated with the expression of the lone pairs are strongly localized, an observation that may have implications for the thermal conductivity of the compound. The results indicate the thermodynamic stability of the experimentally observed structure of AsN above ∼17 GPa, provide a detailed insight into the nature of the chemical bonding network underlying the formation of this compound, and open new perspectives to the design and high pressure synthesis of new pnictogen-based advanced materials for potential applications of energetic and technological relevance.

Unzipping hBN with ultrashort mid-infrared pulses.

Manipulating the nanostructure of materials is critical for numerous applications in electronics, magnetics, and photonics. However, conventional methods such as lithography and laser writing require cleanroom facilities or leave residue. We describe an approach to creating atomically sharp line defects in hexagonal boron nitride (hBN) at room temperature by direct optical phonon excitation with a mid-infrared pulsed laser from free space. We term this phenomenon "unzipping" to describe the rapid formation and growth of a crack tens of nanometers wide from a point within the laser-driven region. Formation of these features is attributed to the large atomic displacement and high local bond strain produced by strongly driving the crystal at a natural resonance. This process occurs only via coherent phonon excitation and is highly sensitive to the relative orientation of the crystal axes and the laser polarization. Its cleanliness, directionality, and sharpness enable applications such as polariton cavities, phonon-wave coupling, and in situ flake cleaving.

In-situ EBSD analysis of hydride phase transformation and its effect on micromechanical behavior in Zircaloy-4 under uniaxial tensile loading

In this work, hydrogen charged Zircaloy-4 has been investigated under an in-situ electron backscatter diffraction during tensile loading. Aim were, first, to distinguish the hydride phase type and its spatial distribution, second to determine hydride phase transformation (HPT) and orientation relationship (OR) subjected to uniaxial tensile condition, and third to correlate the hydrides evolution and their effect on the micromechanical behavior, such as slip mode activation and lattice rotation, of Zircaloy-4. Apart from the applied stress, the analysis reveals that hydride reorientation is strongly related to temperature and loading mode. We noted that deformation induced δ-ZrH1.5 transformed to γ-ZrH and ε-ZrH2, and the former follows the confirmed OR {0001}α//{111}δ/γ with <11 2‾ 0>α//<110>δ/γ, while the latter's OR changed to {10 1‾ 0}α//{121}ε with <11 2‾ 0>α//<100>ε after HPT. The coexistence of δ-ZrH1.5 and γ-ZrH or ε-ZrH2 is observed, and the main corresponding OR is {111}δ//{111}γ with <121>δ//<121>γ, and {100}δ//{110}ε with <110>δ//<100>ε, respectively. The characterized microstructure and the measured lattice rotation results indicate that HPT delayed cracking in hydride and promoted deformation in parent grains. As the strain increases, the maintenance of hydride-matrix (H-M) coherent interfaces restricts further lattice rotation. HPT accelerates the hydride decomposition ascribed to the intensification of hydrogen diffusion under stress, and the hydride and the H-M interfaces act as priority sites for initiating microcracks. The sequence of HPT depends on the possibility of activated slip mode among grains. These findings contribute to developing the understanding of the HPT and hydrogen embrittlement.

Development of novel carbon-free cobalt-free iron-based hardfacing alloys with a hard π-ferrosilicide phase

Recently, iron-based alloys with a π-ferrosilicide phase have emerged as potential alternatives to cobalt-based hardfacing alloys. Here, we present the development of two π-ferrosilicide containing alloys: one with a ferritic matrix and the other with a ferritic-austenitic matrix. In the as-cast condition, both alloys revealed fine Ni- and Si-rich coherent cubic shaped D03 precipitates in the BCC matrix. The π-ferrosilicide phase was found to have an orientation relationship with the ferrite phase, nucleating within ferrite matrix and from ferrite grain boundaries. In contrast to carbide-strengthened hardfacing Fe-alloys, here the dissolution of the π-ferrosilicide phase at 1200°C enables easy thermomechanical processing of these alloys, which results in refinement of the π-ferrosilicide and additional formation of χ-phase precipitates in the ferrite. Nano-scratch tests provided evidence of a resilient silicide-ferrite interface, likely to due to it possessing some coherency. Both alloys also displayed compressive strengths approaching 2 GPa and ductility in compression of approximately 25%. The combination of processability and attractive mechanical properties suggests that these alloys have the potential to serve as alternatives to carbide-reinforced hardfacing Fe-alloys.

A new compact symmetric shear diamond anvil cell for in situ high-pressure-torsion studies.

In situ studies under severe plastic deformation at high pressures, employing shear diamond anvil cells, have recently gained much interest in the high-pressure community owing to their potential applications in material processing methods, mechanochemistry, and geophysics. These studies, combined with multi-scale computational simulations, provide important insights into the transient hierarchical microstructural evolution, structural phase transitions, and orientation relationship between parent and daughter phases and help establish the kinetics of strain-induced phase transitions under severe plastic deformation. The existing SDACs are mostly used in axial x-ray diffraction geometry due to geometrical constraints providing less reliable information about stress states and texture. Their asymmetric design also poses serious limitations to high-pressure shear studies on single crystals. To overcome these limitations, a new compact symmetric shear diamond anvil cell has been designed and developed for in situ high-pressure torsion studies on materials. The symmetric angular opening and short working distance in this new design help obtain a more reliable crystallographic orientation distribution function and lattice strain states up to a large Q range. Here, we present the advantages of the symmetric design with a few demonstrative studies.

Enhanced heterogeneous nucleation in Al alloys by melt ultrasonic treatment

The mechanisms of grain refinement in the A1050 alloy through melt ultrasonic treatment (UT) and isothermal holding were investigated. The results showed that UT resulted in considerable grain refinement, with refining efficiency tending to stabilize after 15min of holdings. Meanwhile, it was found that UT breaks down natural oxide films into fine γ-Al2O3 particles with {111} or {110} exposed surfaces. The well-defined cube-on-cube orientation relationships between γ-Al2O3 and α-Al verify that γ-Al2O3 dispersoids can act as potent substrates for the nucleation of α-Al grains. Based on experimental observations and theoretic calculations, enhanced heterogeneous nucleation in A1050 alloys can be attributed to the high potency of γ-Al2O3 particles with atomic misfits of ~2% on all exposed surfaces and their increased number density induced by the synergistic effects of cavitation and acoustic streaming.

Emergent Correlated Phases in Rhombohedral Trilayer Graphene Induced by Proximity Spin-Orbit and Exchange Coupling.

The impact of proximity-induced spin-orbit and exchange coupling on the correlated phase diagram of rhombohedral trilayer graphene (RTG) is investigated theoretically. By employing abinitio-fitted effective models of RTG encapsulated by transition metal dichalcogenides (spin-orbit proximity effect) and ferromagnetic Cr_{2}Ge_{2}Te_{6} (exchange proximity effect), we incorporate the Coulomb interactions within the random-phase approximation to explore potential correlated phases at different displacement fields and doping. We find a rich spectrum of spin-valley resolved Stoner and intervalley coherence instabilities induced by the spin-orbit proximity effects, such as the emergence of a spin-valley-coherent phase due to the presence of valley-Zeeman coupling. Similarly, proximity exchange removes the phase degeneracies by biasing the spin direction, enabling a magnetocorrelation effect-strong sensitivity of the correlated phases to the relative magnetization orientations (parallel or antiparallel) of the encapsulating ferromagnetic layers.

Epitaxial growth of gehlenite in CaO-MgO-Al2O3-SiO2 based glass ceramic induced by Nb2O5 addition

In this study, the crystallization behavior of a CaO-MgO-Al2O3-SiO2 based glass ceramics with Nb2O5 addition was investigated by using DSC, XRD and TEM techniques. It was found that three crystalline phases, namely, CaNb2O6, diopside and Gehlenite (Ca2Al2SiO7), were formed from the glass matrix during the crystallization heat treatment. The CaNb2O6 phase was the first to precipitate from the glass matrix at around 850°C, acting as a nucleating agent that facilitated the formation of Gehlenite (Ca2Al2SiO7) at 900-950°C. The TEM observation revealed a consistent orientation relationship between the CaNb2O6 and the Gehlenite (Ca2Al2SiO7) phases, indicating that CaNb2O6 could induce the epitaxial growth of Gehlenite (Ca2Al2SiO7). This result provides a new insight into the preparation of Gehlenite epitaxial films and glass ceramics.

Phase formation and elemental transport in the vacuum diffusion bonding between CoCrFe0.2NiMn and CoCrFe16NiMn multicomponent alloys

To efficiently explore the influence of Fe content on the phase stability of the multicomponent CoCrFexNiMn (hereafter abbreviated as Fex) alloys. A diffusion layer with continuous, concentration gradient of Fe element is created based on diffusion couple technique. The microstructure and element distribution of the diffusion bonded layer between Fe0.2 and Fe16 alloys are analyzed. A new layer of FCC and HCP solid solution phases generates in the diffusion zone, which is consistent with the prediction of parametric approach and phase diagram calculation. As diffusion proceeds, the FCC phase is transformed from the BCC phase with the decreasing of Fe content and the HCP phase might be the transitional phase during this transition. The newly formed FCC and HCP phases are shown specific orientation relationships with the BCC phase. Elemental analysis indicated that the diffusion rate of the alloy components in the FCC phase is Cr > Mn > Co > Ni. The large concentration gradient in the diffuse interface and grain boundaries diffusion of BCC phase promoted the Fe diffusion, causing the BCC phase to transform into FCC phase.

Achieving highly variable mechanical behaviors in TiBw/TA15(Si) composite by microstructure manipulation

Discontinuously reinforced titanium matrix composites (DRTMCs) are competitive candidates for aero-space applications. However, the high processing temperature of DRTMCs often yields fully lamellar microstructures, making their properties hard to be tailored by heat treatment. In our previous work, a TiBw/TA15(Si) composite with fine microstructure was fabricated, showing a good potential for microstructure and mechanical properties manipulation. In the present work, heat treatments of different conditions were conducted to this TiBw/TA15(Si) composite. Controllable microstructures from bimodal to fully laminated, and varied mechanical properties, with the ultimate strength ranging from 1136 MPa to 1347 MPa and the elongation ranging from 6.7% to 12.9%, were obtained. The softening induced by microstructure coarsening was balanced by the strengthening of the lath microstructure, and the deformation behaviors of heat-treated composites were determined to be influenced by the strain softening and the constraint of Burgers orientation relationship in the lath microstructure. The present work provided an insight into the deformation and strengthening mechanism of TiBw/TA15(Si) composite, and revealed the possibility of DRTMCs to fulfill the requirements from different service conditions without changing the chemical composition and fabrication procedures.

Microstructures and mechanical properties of TiAl matrix composites with multi-precipitates quasi-continuous network reinforced structures

A novel quasi-continuous network reinforced structure that consists of borides and carbides in B4C/TiAl matrix composites was innovatively designed for the strengthening at high temperatures. Simultaneously, impacts of such reinforced structures on microstructures and mechanical properties of the composites have been unveiled. TiAl matrix units in B4C/TiAl composites are duplex microstructures which are composed of (α2+γ) colonies and γ grains. The ascent of B4C contents triggers off the formation of network reinforced structures in the layers of TiAl matrix units. With B4C contents increasing to 0.1wt.%, elasticity modulus and ultimate compressive strengths of B4C/TiAl composites are upgraded from 10.944GPa and 723.10MPa to 16.052GPa and 774.611MPa. As B4C contents reach at 5.0wt.%, elasticity modulus and ultimate compressive strengths further soar to 17.244GPa and 799.19MPa. Borides and carbides within the quasi-continuous network reinforced structures are unfolded as stripe and needle shaped TiB with B27 structure and Ti2AlC particles with MAX structure. Parts of Ti2AlC particles take TiB as cores to nucleate and grow. Moreover, TiC phases usually act as the cores for the nucleation of Ti2AlC particles. The orientation relationships of such reinforcements represent as [011]TiC//[010]TiB, (1-11)[011]TiC//(0006) [-2110]Ti2AlC, [100]TiB//[0001]Ti2AlC, [010]TiB//[-2110]Ti2AlC and [001]TiB//[01-10]Ti2AlC. The fractures of TiB are usually along or perpendicular to [010]TiB direction. Meanwhile, the fracture surfaces of TiB are always parallel to (100)TiB or (010)TiB planes. Additionally, dislocations slip through Ti2AlC particles and lead to separation and sliding of staking planes (0001)Ti2AlC within Ti2AlC lattices. TiB and Ti2AlC with alternative distribution can stabilize the network reinforced structures and upgrade properties of B4C/TiAl composites.

Effect of applied stress on bainite transformation, microstructure, and properties of 15CrMo steel

The effect of external stress on the isothermal bainite transformation kinetics and microstructure of 15CrMo steel was studied using dilatometer, optical microscopes (OM), electron back-scatter diffraction (EBSD), scanning electron microscopes (SEM) and X-ray diffraction (XRD). The results show that the additional mechanical driving force provided by the external stress promotes the transformation of bainite, resulting an increase volume fraction of bainite-ferrite (BF) and causing the BF laths to become slender. The application of external stress can also induce selective orientation during the bainite transformation process, and the orientation relationship between the prior austenite and the BF under stress is closer to the Kurdjumov-Sachs (K-S) relationship. There is also an incomplete transformation of bainite transformation under stress. At the same time, the Vickers hardness of 15CrMo steel would increase after applying external stress. The mechanical driving forces calculations demonstrate that when tensile stress and compressive stress are of similar magnitudes, they provide comparable mechanical driving forces. As a result, they exert similar effects on the kinetics of bainite transformation, leading to no discernible differences in the resulting bainite microstructure.

Assessing multiple values of nature in National Biodiversity Strategies and Action Plans

Abstract Around the world, people express a variety of values of nature based on how they relate and interact with it. These values of nature, broadly classified as instrumental, intrinsic, and relational values, underlie environmental policy and decision‐making processes. In this paper, our aim was to assess the values of nature that are expressed in national environmental policy documents. We assessed the National Biodiversity Strategies and Action Plans (NBSAPs), the key national policy framework for biodiversity conservation, from 11 countries, representing the five regional United Nations groups. We used qualitative content analysis to identify the value orientation of the statements in the NBSAPs and the main themes under each. Across the 11 NBSAPs, unspecified value orientation statements were the most common (40%), followed by instrumental (38%), intrinsic (14%) and relational (9%) value orientation statements. We identified the main themes in the instrumental value orientation statements as follows: (1) sustainability, (2) natural resources and (3) ecosystem services. The main themes present in the intrinsic value orientation statements were as follows: (1) recognizing intrinsic value, (2) endangered species and habitats, (3) conservation programmes and (4) threats to nature. Relational value orientation statements referenced as follows: (1) duty and responsibility to protect nature, (2) values expressed for nature, (3) national pride and heritage, (4) Indigenous peoples and local community's (IP&amp;LCs) relationships with nature, (5) protecting nature for future generations and (6) equity in the use and access of nature. Our findings indicate that NBSAPs respond to the directive of the Convention on Biological Diversity. They are primarily based on the instrumental values of nature, only rarely considering other ways in which nature is valuable to people. This can reinforce unjust outcomes for human well‐being since environmental policies may not reflect the diverse ways in which nature and biodiversity matter to the population. In an increasingly interconnected world, environmental policies are called on to incorporate multiple values to achieve positive outcomes for both human well‐being and biodiversity conservation. Read the free Plain Language Summary for this article on the Journal blog.