Uniaxial Deformation Research Articles

Structural aspects of stress-induced magnetic anisotropy in Fe-based nanocrystalline alloy

This work is focused on the quantitative description of structural anisotropy in the Fe73.6Cu1Nb3Si15.5B6.9 alloy induced in the process of nanocrystallization during tensile annealing. Structural changes induced by annealing under uniaxial tensile deformation were investigated using X-ray diffraction. It was shown that Fe3Si nanocrystalline grains growing in the tensile direction have a higher value of the lattice spacing. An opposite behavior is seen in transversal direction. The difference between the value of the lattice strain determined in the longitudinal and transverse directions is proportional to the magnitude of the tensile stress applied and represents a quantitative parameter determining the degree of stress induced anisotropy (SIA). Strain pole figure (SPF) measurements provide evidence that the SIA is uniaxial, and its main axis is aligned along tensile direction. Quantitative comparison of the SPFs shows that the strain partitioning among different Bragg reflections is not even and {400} family of planes exhibits the highest magnitude of the SIA. Furthermore, it was found that the magnitude of the SIA for a given set of Bragg reflections {hkl} is inversely proportional to its Young’s modulus Ehkl.

Extra-High Mechanical and Phononic Anisotropy in Black Phosphorus Blisters.

Strain is an effective strategy to modulate the electrical, optical, and optoelectronic properties of 2D materials. Conventional circular blisters could generate a biaxial stretching of 2D membranes with notable strain gradients along the hoop direction. However, such a deformation mode cannot be utilized to investigate mechanical responses of in-plane anisotropic 2D materials, for example, black phosphorus (BP), due to its crystallographic orientation dependence. Here, a novel rectangular-shaped bulge device is developed to uniaxially stretch the membrane, and further provide a promising platform to detect orientation-dependent mechanical and optical properties of anisotropic 2D materials. Impressively, the derived anisotropic ratio of Young's modulus of BP flakes is much higher than the values obtained via the nanoindentation method. The extra-high strain-dependent phononic anisotropy in Raman modes along different crystalline orientations is also observed. The designed rectangular budge device expands the uniaxial deformation methods available, allowing to explore the mechanical, and strain-dependent physical properties of other anisotropic 2D materials more broadly.

Automated segmentation and prediction of intervertebral disc morphology and uniaxial deformations from MRI

ObjectiveThe measurement of in vivo intervertebral disc (IVD) mechanics may be used to understand the etiology of IVD degeneration and low back pain (LBP). To this end, our lab has developed methods to measure IVD morphology and uniaxial compressive deformation (% change in IVD height) resulting from dynamic activity, in vivo, using magnetic resonance images (MRI). However, due to the time-intensive nature of manual image segmentation, we sought to validate an image segmentation algorithm that could accurately and reliably reproduce models of in vivo tissue mechanics. DesignTherefore, we developed and evaluated two commonly employed deep learning architectures (2D and 3D U-Net) for the segmentation of IVDs from MRI. The performance of these models was evaluated for morphological accuracy by comparing predicted IVD segmentations (Dice similarity coefficient, mDSC; average surface distance, ASD) to manual (ground truth) measures. Likewise, functional reliability and precision were assessed by evaluating the intraclass correlation coefficient (ICC) and standard error of measurement (SEm) of predicted and manually derived deformation measures. ResultsPeak model performance was obtained using the 3D U-net architecture, yielding a maximum mDSC ​= ​0.9824 and component-wise ASDx ​= ​0.0683 ​mm; ASDy ​= ​0.0335 ​mm; ASDz ​= ​0.0329 ​mm. Functional model performance demonstrated excellent reliability ICC ​= ​0.926 and precision SEm ​= ​0.42%. ConclusionsThis study demonstrated that a deep learning framework can precisely and reliably automate measures of IVD function, drastically improving the throughput of these time-intensive methods.

Experimental Study on the Mechanical Properties and Acoustic Emission Characteristics of Different Bedding High-Rank Coals.

Bedding has an important influence on the macroscopic and microscopic mechanical properties of coal, and the mechanical properties of coal and rock mass and acoustic emission characteristics are very important for rock burst monitoring and warning. In order to explore the influence of different beddings on the mechanical properties and acoustic emission characteristics of high-rank coal, using the RMT-150B electrohydraulic servo rock mechanics test system and the DS5 acoustic emission analyzer, the uniaxial compression and acoustic emission characteristics of high-rank coals with different beddings (parallel bedding 0°, oblique bedding 30, 45, 60°, and vertical bedding 90°) were investigated. The results show that the uniaxial compressive strength and deformation modulus of vertical stratified coal samples are the largest, which are 28.924 MPa and 2.95 GPa, while the average values of uniaxial compressive strength and deformation modulus of oblique stratified coal samples are the smallest, which are 10.91 MPa and 1.776 GPa, respectively. With the increase of the bedding angle, the uniaxial compressive strength of high-rank coal decreases first and then increases. The stress-strain process of coal varies greatly with different high stratification grades (parallel bedding 0°, oblique bedding 30°, 45°, 60° and vertical bedding 90°). The loading times of parallel, oblique, and vertical beddings are 700, 450, 370, 550, and 600 s, and the acoustic emission mutation point values are 495, 449, 350, 300, and 410 s. The mutation point value can be used as precursor information to judge the failure of high-rank coal in different beddings. Research results to find the high-rank coal destruction instability prediction method and the index provide a basis; further damage to the acoustic emission testing high order coal provides reference significance; and the use of acoustic emission in the monitoring and early warning of percussive ground pressure, the bedding surface of coal, and the actual stress on site should be considered.

Solitary wave-based site-specific bone quality assessment: A numerical study of the proximal femur

We examine numerically the feasibility of using a relatively new solitary wave-based non-destructive test (NDT) method for site-specific bone quality assessment. Towards this end, we present numerical predictions of the effective elastic modulus of trabecular bone in the proximal femur using highly nonlinear solitary waves (HNSWs) propagating in a one-dimensional chain of spherical steel particles. A computational bone reconstruction technique, enabled through topology optimization, is developed to generate high-resolution finite-element models representing the complex architecture of the trabecular network in the femoral neck region of the proximal femur. The reconstructed bone microstructure models are then used as the inspection medium in a virtual NDT setup in the form of a hybrid discrete-element/finite-element (DE/FE) model, capable of simulating the propagation of HNSWs in the granular chain and their interaction with the bone microstructures. By inserting a face sheet between the granular chain and the porous trabecular bone model, our calculations evince that dynamic loading by the incident solitary wave results in nearly uniaxial deformation of the bone microstructure (rather than localized contact indentations), and this is shown to enhance the accuracy and reliability of the solitary wave-based prediction of the bone’s effective elastic modulus. Using the delay of the primary reflected solitary wave in the estimation of the elastic modulus of bone, we are able to estimate the effective elastic moduli of the porous bone models with adequate accuracy. Based on these numerical findings, we believe that solitary wave-based non-destructive evaluation of computationally reconstructed artificial bone models could form the baseline for advanced bone quality assessment tools.

Mechanical Properties of the Pt-CNT Composite under Uniaxial Deformation: Tension and Compression.

Composite materials are gaining increasing attention from researchers worldwide due to their ability to offer tailored properties for various technical challenges. One of these promising fields is metal matrix composites, including carbon-reinforced metals and alloys. These materials allow for the reduction of density while simultaneously enhancing their functional properties. This study is focused on the Pt-CNT composite, its mechanical characteristics, and structural features under uniaxial deformation depending on temperature and mass fractions of carbon nanotube (CNT). The mechanical behavior of platinum reinforced with carbon nanotubes of diameters varying in the interval 6.62-16.55 Å under uniaxial tension and compression deformation has been studied by the molecular dynamics method. Simulations for tensile and compression deformations have been done for all specimens at different temperatures (viz. 300 K, 500 K, 700 K, 900 K, 1100 K, and 1500 K). The calculated mechanical characteristics allow us to conclude that, compared to pure platinum, the Young's modulus increased by about 60%. The results indicate that yield and tensile strength values decreases with increase in temperature for all simulation blocks. This increase was due to the inherent high axial rigidity of CNTs. In this work, these characteristics are calculated for the first time for Pt-CNT. It can be concluded that CNTs can be an effective reinforcing material for composites based on a metal matrix under tensile strain.

Acoustic Emission Behavior of TATB Based PBX during Uniaxial Compression Deformation

In order to study the feasibility of acoustic emission technology for the damage and fracture monitoring of TATB-based PBX materials and components, the acoustic emission characteristics of notched and unnotched specimens under uniaxial compression were studied. The results of uniaxial compression and step-cycle compression experiments of unnotched specimens showed that there were few AE hits with low amplitude under low strain stage and many AE hits were generated when the specimen failed. In addition, the Kaiser effect is applicable at the low load stage. In addition, there were less AE hits in initial loading stage for the specimen with notches, which may be caused by machining force. However, very strong AE hits were generated in the specimen with notches before macroscopic fracture occurred. Acoustic emission technology can be used to determine whether macroscopic cracks were generated in TATB-based PBX structures in the experiment.

LAP2β transmits force to upregulate genes via chromatin domain stretching but not compression.

There is increasing evidence that force impacts almost every aspect of cells and tissues in physiology and disease including gene regulation. However, the molecular pathway of force transmission from the nuclear lamina to the chromatin remain largely elusive. Here we employ two different approaches of a local stress on cell apical surface via an RGD (Arg-Gly-Asp)-coated magnetic bead and whole cell deformation at cell basal surface via uniaxial or biaxial deformation of a fibronectin-coated flexible polydimethylsiloxane substrate. We find that nuclear protein LAP2β mediates force transmission from the nuclear lamina to the chromatin. Knocking down LAP2β increases spontaneous movements of the chromatin by reducing tethering of the chromatin and substantially inhibits the magnetic bead-stress or the substrate-deformation induced chromatin domain stretching and the ensuing dihydrofolate reductase (DHFR) gene upregulation. Analysis of DHFR gene-containing chromatin domain alignments along or perpendicular to the direction of the stretching/compressing reveals that the chromatin domain must be stretched and not compressed in order for the gene to be rapidly upregulated. Together these results suggest that external-load induced rapid transcription upregulation originates from chromatin domain stretching but not compressing and depends on the molecular force transmission pathway of LAP2β. STATEMENT OF SIGNIFICANCE: How force regulates gene expression has been elusive. Here we show that the orientation of the chromatin domain relative to the stress direction is crucial in determining if the chromatin domain will be stretched or compressed in response to a cell surface loading. We also show that nuclear protein Lap2b is a critical molecule that mediates force transmission from the nuclear laminar to the chromatin to regulate gene transcription. This study reveals the molecular force transmission pathway for force-induced gene regulation.

Understanding the effect of deformation combined with heat treatment on age hardening of Al–Zn–Mg–Cu alloy AA7075

Al–Zn–Mg–Cu alloys obtain their exceptional high strength predominately relying on precipitation. Deformation can influence the evolution of precipitation and may potentially provide additional strength through work hardening. In this study, the coupling of dislocation and precipitation strengthening to achieve unique property combinations with strengths greater than those due to heat treatment alone was investigated on pre-aged AA7075 subject to a pre-age, deform, post-age cycle. The evolution of precipitates and mechanical properties were characterised to understand the contribution of each mechanism to the final strength. Small angle X-ray scattering (SAXS) was used to monitor the precipitate evolution during post-ageing, with the support from transmission electron microscopy (TEM) and isothermal calorimetry. The results revealed that uni-axial deformation to 10% strain had negligible effects on pre-existing precipitates but introduced sufficient dislocations to enable significant work hardening, which resulted in strengths greater than those obtained with a T6 heat treatment but with a sacrifice in further strain to failure. Post-ageing at 120 °C was found being effective on partially recovering dislocations and promoting precipitation strengthening. A simple model was applied to demonstrate that the time required to reach peak strength is determined by the competing effects of the enhanced kinetics of precipitation and dislocation recovery. The acceleration effect of prior deformation on the growth of precipitation during post-ageing is consistent with the expected effect of dislocations acting as the fast diffusion paths.

Cold uniaxial deformation of powder materials based on Ti‒B/Ti‒Al‒Nb‒Mo‒B

Cold uniaxial deformation of powder materials based on Ti‒B/Ti‒Al‒Nb‒Mo‒B

Energy harvesting by piezoelectric polyvinylidene fluoride/zinc oxide/carbon nanotubes composite under cyclic uniaxial tensile deformation

AbstractIn this study, polyvinylidene fluoride (PVDF)/zinc oxide (ZnO)/carbon nanotubes (CNT) nano‐reinforced composites were fabricated by solution casting method. Addition of ZnO and CNTs nanoparticles enhances the electroactive polar β‐phase of PVDF nanocomposites. Formation of β‐phase in the composites were examined by Fourier transform infrared spectroscopy and X‐ray diffraction analysis. Piezoelectric properties were investigated by applying uniaxial cyclic tensile deformation with the help of mechanical tensile tester device. The maximum generated voltage peak of 1.32 V was observed in the case of the nano‐reinforced composite having 15% ZnO, with maximum current of 0.61 μA and power of 0.66 μW. The fabricated PVDF/ZnO/CNTs nano‐reinforced composites can be a good candidate for human motion‐based energy harvesting applications during walking, running and so forth in which uniaxial deformation occurs.

Uniaxial compression deformation and fracture mechanism of cold metal transfer (CMT) arc additive Mg–Gd–Y–Zn–Zr alloy

Mg–Gd–Y–Zn–Zr alloy were fabricated using the cold metal transfer (CMT) arc additive technology. The deformation mechanism and fracture characteristics of the Mg–Gd–Y–Zn–Zr alloy under uniaxial compression were studied by numerical simulation and experiment. The results revealed that the unique delamination and solidification characteristics of CMT and the Marangoni effect of the molten pool promoted the continuous distribution of β-Mg24(Gd, Y)5, at the grain boundary of the α-Mg matrix. Compared with the longitudinal section, the cross section had a uniform grain size distribution, and more dense and regular dimples were formed after the fracture. The Vickers hardness of the cross section was higher than that of the longitudinal section before and after compression. The compressive strength of the cross section was 426.12 MPa, and the fracture elongation was 20.25%, which was 10.14% higher than that of the longitudinal section. This was attributed to the equiaxed and eutectic structure with the uniform cross-section distribution. β-Mg24 (Gd, Y)5 played a better role in fine grain strengthening and precipitation strengthening than the irregularly distributed longitudinal section. The prediction of the fracture tendency of the Mg–Gd–Y–Zn–Zr alloy by using the finite element method was in agreement with the experimental results of uniaxial compression. The concentration of stress and strain at the shear site was the direct cause of fracture. Further, the obvious ‘cleavage step'and ‘tongue-like patterns'existed in the fracture morphology, which proved that the Mg–Gd–Y–Zn–Zr alloy formed by CMT had certain brittleness, and the fracture type was transgranular fracture.

First-principles calculation of the electronic, optical, and photo-electrochemical properties of CaM2S4 (M = Sc, Y) compounds

The orthorhombic CaM2S4 (M = Sc, Y) structures were investigated in the present work by first-principles calculations. CaM2S4 (M = Sc, Y) compounds are found to be mechanically stable with the anisotropic elastic constants that make them to be stable with respect to uniaxial deformation (Young’s moduli are 73.724 and 57.441 GPa for CaSc2S4 and CaY2S4, respectively) but easy to be undergone to shear deformation (Poisson’s ratios are 0.352 and 0.371 for CaSc2S4 and CaY2S4, respectively). Due to their relatively small direct energy band gaps (1.89 eV for CaSc2S4 and 2.26 eV for CaY2S4), the two compounds are intriguing candidates for long-wave transparency applications. The high hybridization degree of Ca-d, Y/Sc-d and S-p orbitals results in a wide energy range between the valence highest band and the conduction lowest band enabling these compounds to interact actively with visible and ultra-violet waves. The high absorption rate of 12–18 × 105 cm−1 and good hole-electron separation make CaM2S4 (M = Sc, Y) compounds to consider them good candidates for optoelectronic materials. Moreover, CaM2S4 (M = Sc, Y) compounds show good ability in the process of photo-driven photocatalyst water splitting.

Uniaxial deformation of nanowires in 16 refractory multi-principal element alloys

Metallic nanowires are widely employed as small-scale structural materials due to their characteristically small volume and high strength compared with their bulk counterparts. Nowadays, the mechanical properties of nanowires in pure metals are well understood with the help of experiments and simulations. However, the deformation of nanowires in metallic alloys remains elusive. In recent years, a new class of alloys called refractory multi-principal element alloys (RMPEAs) emerged. RMPEAs are alloys that form solid solution phases and consist of three or more principal elements, most of which are refractory metals. In this paper, we perform atomistic simulations to investigate the uniaxial deformation of nanowires in 16 body-centered cubic RMPEAs. For each RMPEA, three nanowires consisting of atoms randomly distributed in three different ways are used. The main finding is that dislocation slips on {110} planes and twinning on {112} planes, respectively, control the compressive and tensile plastic deformation of the nanowires. To provide references, we also study the deformation of nanowires in natural and A-atom potential-based artificial pure metals. Results show that the deformation of RMPEA nanowires cannot be predicted by simply extrapolating from those of pure metal nanowires, highlighting the significance of directly simulating RMPEAs using multiple random atomic structures. It is also found that RMPEAs possess a reduced tension-compression asymmetry compared with pure metals, regardless of the underlying plastic deformation mechanism.

Tensoelectric properties irradiated by the fast electrons n-Ge single crystals

Tensoelectric properties of the uniaxially deformed along the crystallographic direction [100] n-Ge single crystals, irradiated by the flows of electrons , , and , with the energy of , were investigated. Mechanisms of changes in resistivity and mobility of current carriers under the uniaxial deformation for the studied n-Ge single crystals based on the measurements of tenso-Hall effect and infrared Fourier spectroscopy were established.The presence of tensoresistance for n-Ge single crystals, irradiated by the flow of the electrons , is associated with changes under the uniaxial pressure of electron concentration in the conduction band and holes in the valence band due to a decrease of the ionization energy of the deep level of the radiation defects which belongs to the complexes , at the uniaxial deformation. A significant increase of the effective mobility of carriers current in uniaxially deformed single crystals n-Ge is primarily related to the deforming redistribution of electrons between the branch of ‘light’ holes and the level . For single crystals n-Ge irradiated by the flows of electrons , which lead to the n-p conversion of the conductivity type of germanium, significant tensoresistance is observed only at the pressures . In this case, the resistivity of n-Ge decreases both due to an increase in the concentration of holes and their mobility under the deformation. Mobility of holes does not depend on deformation for uniaxial pressures , and a slight decrease in the resistivity of the researched single crystals n-Ge is caused by an increase in their concentration. Radiation-induced tensosensitivity at the room temperature for single crystals n-Ge can be used in technologies for creating uniaxial pressure sensors based on germanium. Obtained radiation effect of a significant increase in the mobility of current carriers for the uniaxially deformed n-Ge single crystals can find its practical application in the creation of ‘germanium’ channels of n-MOSFET and p-MOSFET transistors.

An investigation of slip transmission during uniaxial tensile deformation of a coarse-grained copper via EBSD characterization and crystal plasticity modelling

This study explores the phenomenon of slip transmission across grain boundaries in coarse-grained copper. The associated effects on the deformation gradient are also investigated, using both experiment and simulation. An in-situ tensile test of a fully annealed copper specimen was conducted first using a scanning electron microscope (SEM). The deformation gradient and geometrically necessary dislocation (GND) maps at selected tensile strain values were obtained and characterized by electron backscatter diffraction (EBSD). In addition, a physically based strain gradient crystal plasticity finite element method model has been developed to simulate the early stage of tensile deformation behaviour of copper. In this model, slip transmission across the grain boundary is either allowed or blocked, depending on the alignment of adjacent grains. Slip transmission is allowed at grain boundaries between suitably aligned grains according to the Luster-Morris factor, residual Burgers vector is applied to consider the slip misalignment at GB region, and dislocation accumulation at grain boundaries is included following the Kocks-Mecking law. It was found that dislocation pile-up, lattice rotation and stress concentration were much higher near the impenetrable grain boundaries than at the penetrable ones. Due to the slip transmissions across grain boundaries, the stress and strain concentrations can be partially relaxed, and the slip transmission induced relaxation is associated with the number of active slip systems and shear strain on the best aligned slip systems. This study provides an effective strategy to investigate the early stage of plastic deformation, and a good agreement between experimental observations and simulation results has been achieved.

Identify the causes of coating dusting when stamping hot-dip galvanised sheet metal parts

Dusting the zinc coating when stamping car bodies results in coagulated dust particles (lumps) that are imprinted on the bodywork surface. A visual check is always carried out after the last stamping operation to prevent such a defect. If a defect is detected, the entire stamping line is stopped and the die is cleaned or, even worse, replaced. In order to clarify the causes of dusting, the chemical composition X-ray microanalysis of dusting particles was performed, 3D dimensions of these particles were determined and they were compared with the rough surface dimensions of the automotive sheet. It is shown that the hypothesis about occurrence of dusting particles as a consequence of shearing roughness of the zinc coating during stamping should be considered unlikely. Another mechanism for dusting zinc coating was considered. A study of surface roughness formation during uniaxial deformation showed that these pro-cesses of bare metal and zinc-coated metal differ significantly. These differences can provoke another type of zinc coating failure as a process of loosening the metal-zinc coating boundary, which has not been considered so far. This type of fracture can be avoided if the discussed experimental dependences of micro topographic characteristics on elongation in the coating and in the substrate lack such radical difference

In situ visualization of the tensile deformation mechanism of bacterial cellulose network

Bacterial cellulose (BC) pellicles are strong hydrogels composed of nanofibril networks. These hydrogels are considered attractive materials for synthetic biology, in which biological systems or modules are designed with user-defined functions. To develop BC-based materials with tailored mechanical properties, elucidation of the tensile deformation mechanism is essential. Therefore, in this study, BC hydrogels were fluorescently labeled, and the fiber network under tensile deformation was observed in situ using a device for simultaneous confocal laser scanning microscopy and uniaxial tensile deformation. As a result, strain-dependent deformation modes were identified and the generation of stress paths (stress-loaded fiber segments) during deformation was visualized. Furthermore, characteristic relaxation spectra of the nanofiber network were obtained from stress-relaxation measurements, revealing the existence of a first-order relaxation mode at approximately 1 s and higher-order relaxation modes over a long time period of 102–105 s. On this basis, we proposed a tensile deformation model of the BC hydrogel characterized by rearrangements of fiber segments accompanied by cleavage of cross-links. This model is expected to facilitate synthetic biology using BC hydrogels.

Microstructure and Macroscopic Characteristics of Powder Superalloy under Different Plastic Deformation Process Parameters

Through the uniaxial compression deformation test, this work focuses on analyzing the microstructure evolution of the alloy in the two stages of dynamic softening and strain hardening in the true stress-true strain curve during hot deformation, including grain size, local misorientation and The interaction of its relative mobility, and through the grain boundary orientation difference and grain orientation, explained the dynamic softening mechanism and strain hardening phenomenon, so as to find the microstructure-determining characteristic parameters of the dynamic recrystallization nucleation and core growth of the alloy and its evolution.

Influence of Deformation Rate on Nucleation and Growth of Recrystallized Grains during Hot Deformation of Nickel-Based Powder Superalloys

High temperature uniaxial compression deformation test was carried out on nickel-based powder superalloy FGH96 alloy by thermal processing simulation test machine, and the relationship between grain boundary characteristics and nucleation mechanism of recrystallized grains, growth characteristics of recrystallized cores and related dynamic softening mechanisms was studied. According to the correlation and evolution law of grains, combined with the change trend of grain orientation during the deformation process, the recrystallization behavior characteristics of the grains with special orientation generated during the deformation process were analyzed. When the deformation temperature is 1070 °C, the evolution rules of the substructure grain boundaries with an orientation difference of less than 10° are different under different deformation rate conditions, which indicates that the dynamic softening mechanism of FGH96 alloy is slightly different with the increase of deformation rate. There are different. With the increase of the deformation rate, the nucleation mechanism induced by Σ3 twinning gradually replaced the nucleation mechanism of continuous subgrain rotation and coarsening, and the grain growth rate gradually slowed down.