Compressive Deformation Research Articles

High-performance anisotropic Sm2Co17/Fe(Co) bulk nanocomposite magnets fabricated by two-step high-pressure thermal compression deformation

In the realm of Sm2Co17 nanocomposite magnetic materials, it remains a challenge to fabricate anisotropic magnets by forming nanocrystalline Sm2Co17 phases with strong texture, alongside soft phases of small size and high soft phase content. In this paper, we present a novel approach for fabricating anisotropic Sm2Co17/Fe(Co) nanocomposite bulk magnets with a prominent (00 l) texture of the Sm2Co17 phase, the 25 wt% content of the Fe(Co) phase, and a refined grain size of 25 nm. This fabrication is achieved using a two-step high-pressure thermal compression (HPTC) deformation process. The fabricated magnets exhibit a maximum energy product [(BH)max] of 20.0 MGOe with a pronounced magnetic anisotropy (Br///Br⊥ = 1.23). This result is 53 % higher than the previously reported largest value [(BH)max = 13.1 MGOe] for Sm2Co17-based nanocomposites. The magnets also exhibit a low remanence temperature coefficient (α = −0.014 %/°C) and a low coercivity temperature coefficient (β = −0.23 %/°C), demonstrating exceptional thermal stability. Our findings may improve the fabrication of anisotropic bulk Sm2Co17 nanostructure magnets for practical applications.

Exploring the ultramicropore structure evolution and the methane adsorption of tectonically deformed coals in molecular terms

The mechanical deformation of coals occurring extensively during the geological period (tectonically deformed coals) can directly alter their pore structures and then the storage of coalbed methane. This study in-situ investigated the effects of different mechanical deformations on the ultramicropore structure and the methane adsorption of coal molecules using molecular simulations. The results show that the shear deformation (< 0.23 GPa) of coals was much easier than the compression (~ 20 GPa). Further, the shear deformation can increase the void fraction (200%) and the surface area (30%) of coal molecules, comparing to the reduction of them by the compressive deformation. Accordingly, compression is not benefited to the methane storage (only remaining 14-22% adsorption amount). While, the shear deformation of coals can increase the methane adsorption amount (reaching 42–50 mmol/g). The ~ 7.5 Å is a key pore size to evaluate the effect of the shear deformation on the methane adsorption amount. Also, the adsorption sites for methane depends on the deformation mode of coals (compression: heteroatoms; shear: C atoms). Overall, the strained Wiser (bituminous, medium-rank) coal shows relatively superiority in the methane storage, while the methane adsorption of Wender (lignite, low-rank) coal is much more sensitive to the mechanical strain.

Experimental and model evaluation of cyclic compressive performance for RAC-filled BFRP tube composite columns

The mechanical properties of recycled aggregate concrete (RAC) can be significantly enhanced in RAC-filled fiber-reinforced-polymer (FRP) tube composite columns. However, the cyclic compressive behavior of this type of composite columns has been scarcely studied. In this study, a series of cyclic axial compressive tests were conducted on RAC-filled basalt-FRP (BFRP) tube composite columns, and the effects of confinement level (number of BFRP layers) and RA replacement ratio were investigated. The test results indicate that, compared to RAC columns, the compressive capacity and deformability of RAC-filled BFRP tube composite columns increased significantly under cyclic loading. The compressive strength and ultimate strain of BFRP-confined RAC reached 1.42-3.98 times and 2.88-21.53 times those of unconfined RAC, respectively. The compressive strength and ultimate strain under cyclic loading were generally close to those under monotonic loading, with the compressive strength ratios averaging 1.052 and the ultimate strain ratios averaging 1.031. The enhancement efficiency of BFRP confinement increased progressively with increasing confinement level and/or RA replacement ratio. The envelope curves of the cyclic stress-strain curves resembled the stress-strain curves under monotonic loading. The reloading modulus (Ere) and residual modulus (Eun,0) continuously decreased as the unloading strain (εun) increased, while the plastic strain (εpl) increased almost linearly with εun. The values of Ere, Eun,0 and εpl were affected by the confinement level and RA replacement ratio. Finally, typical theoretical models for FRP-confined concrete were used to evaluate the cyclic stress-strain curves of RAC-filled BFRP tube composite columns.

Superflexible Carbon Nanofibers for Multidimensional Complex Deformation Sensing in Soft Robots.

Soft robots can make complex motions or deformations due to their infinite freedom, which poses great challenges for monitoring their motion and position. While previous investigations of flexible sensing either focused on stretchable or compression deformations in one or two directions, the complex multidimensional deformations that occur on the surfaces of soft robots have been frequently overlooked. In this work, inspired by spider silk, superflexible carbon nanofibers with a bundled structure were biomimetically designed and fabricated using electrospinning technology and carbonization treatment. The fabricated fibers can be microscopically folded at 180° and can sustain multidimensional shrinkage deformation without microstructural damage during 200,000 times of repeated folding. In addition, the fibers process ultrasmall bending resistance that is two orders of magnitude lower than that of A4 paper and commercial conductive fibers, demonstrating excellent flexibility that is ideal for fabricating sensors in soft robots. Combining the study of origami techniques and mechanical simulations, the bending resistance of the fibers was found to have a step change in response to different deformation angles and radii. As a demonstration, a sensor based on this flexible carbon nanofiber successfully monitors the irregular shrinkage deformation of soft parts, showing great potential in applications of grasping, recognition, and perception. This work sheds light on the design of ultraflexible conductive carbon materials and provides an avenue for the extreme shape-morphing monitoring of soft robots.

Geological and Geomorphological Characterization of the Anthropogenic Landslide of Pie de la Cuesta in the Vitor Valley, Arequipa, Peru

This study presents the geological and geomorphological characterization of the Pie de la Cuesta landslide, a large (&gt;60 ha) slow-moving (up 4.5 m/month) landslide in Southern Peru. The landslide has been active since 1975 and underwent a significant re-activation in 2016; the mass movement has caused the loss of property and agricultural land and it is currently moving, causing further damage to property and land. We use a combination of historical aerial photographs, satellite images and field work to characterize the landslide’s geology and geomorphology. The landslide is affecting the slope of the Vitor Valley, constituted by a coarsening upward sedimentary sequence transitioning from layers of mudstone and gypsum at the base, to sandstone and conglomerate at the top with a significant ignimbrite layer interbedded within conglomerates near the top of the sequence. The landslide is triggered by an irrigation system that provides up to 10 L/s of water infiltrating the landslide mass. This water forms two groundwater levels at lithological transitions between conglomerates and mudstones, defining the main failure planes. The landslide is characterized by three main structural domains defined by extension, translation and compression deformation regimes. The extensional zone, near the top of the slope, is defined by a main horst–graben structure that transitions into the translation zone defined by toppling and disaggregating blocks that eventually become earth flows that characterize the compressional zone at the front of the landslides, defined by thrusting structures covering the agricultural land at the valley floor. The deformation rates range from 8 cm/month at the top of the slope to 4.5 m/month within the earth flows. As of May 2023, 22.7 ha of potential agricultural land has been buried.

Investigation on the failure mechanism of friction-based self-centering timber beam-column joint considering bolt bearing effect: Experimental study and theoretical analyses

For friction-based self-centering timber structures, the bearing between friction bolts and the edge of holes is inevitable, due to machining inaccuracies and significant deformations at the beam-column joints. However, this issue has yet to be addressed in existing research. A limit state investigation was conducted on these friction-based self-centering timber beam-column joints under extensive deformation to analyze the failure mechanism and the loss of pretension force throughout the loading process. The influence of bolt bearing behavior on the residual deformation, loading capacity, energy dissipation capacity, and stiffness of the joint was studied. Finally, a theoretical prediction model considering single bolt and multi bolts bearing was proposed incorporating theoretical analysis and experimental results. The results indicate that the damage of the joint is concentrated on the compression deformation at the edge of bolt holes in friction pads and timber beams. The joint ultimately fails due to the end face of the column being crushed by the anchor used to fix post-tensioned (PT) strands. The joint exhibits good hysteresis characteristics within a 4 % drift and still demonstrates good recoverability within a 6 % drift. The loss rate of pretension force is below 15 % when the drift is lower than 4 %, but it increases significantly after the drift exceeds 5 %. When the drift is less than 4 %, the joints primarily exhibit single bolt bearing mode, resulting in only a slight increase in stiffness for the joints. When the drift exceeds 8 %, the joints primarily exhibit a multi bolt bearing mode, resulting in a maximum increase of approximately 64.5 % in joint stiffness. The theoretical bolt bearing model derived can better predict the position of bolts bearing the edge of holes and the damage state of friction-based self-centering timber beam-column joints.

Microstructure and dynamic deformation mechanism of laser powder bed fusion of 316L-containing Ti–6Al–4V with dual-phase heterostructure

In this paper, 316L-containing Ti–6Al–4V alloy was fabricated by laser powder bed fusion (LPBF) through mixing Ti–6Al–4V and 4.5 wt% 316L powders, and the dynamic compressive mechanical properties and deformation mechanism at different strain rates were studied. The results show that the volume fraction of β phase sharply increases from 1.8% (in TC4) to 61.4% (in HST), and micro- and submicron-sized grains coexist in the HST alloy, producing heterostructure in the form of bimodal grain size distribution. The presence of the heterostructure led to superior heterogeneous deformation induced stress, thus facilitating the additional strain hardening and deformation coordinating ability, thus made the HST alloy achieved ultimate compressive stress of ∼1750 MPa and fracture strain of ∼17%, showing excellent comprehensive mechanical properties. Under quasi-static load, the deformation mode of HST alloy is mainly attributed to progressive deformation-induced martensitic transformation. However, at high strain rates, the impact loading inhibited the activation of progressive DIMT, and thus the deformation mode changed to combination of dislocation slipping and deformation twinning.

Study on the evolution rules of coal deformation and failure characteristics caused by multiple mining disturbances

During coal mining operations, the coal will be deformed and damaged due to multiple mining disturbances (MMD), often resulting in disasters, like rock burst. To understand the evolution rules of coal deformation under MMD and its final fracture characteristics after impact dynamic load loading, reduce the adverse effects of mining disturbances, and improve disaster prevention and control capabilities, quasi-static uniaxial cyclic loading-unloading (L-U) and dynamic axial compression tests were conducted on large-sized coal-like samples. During the tests, three-dimensional (3D) laser scanning and acoustic emission (AE) monitoring technology were utilized to accurately capture the full-field deformation and AE response data, facilitating a systematic analysis of deformation and fracture characteristics. The results show that: (1) Under the cyclic L-U effect induced by MMD, each loading cycle causes compression deformation with partial recovery during unloading, presenting an overall “wavy” variation trend. (2) The maximum load is the most critical factor affecting the damaged coal deformation, with smaller load resulting in less overall sample deformation. (3) After the impact dynamic loading, the damaged samples suffered large-scale impact splitting failure, with the compressive-shear layer failure mainly occurred inside the holes. (4) Lower loading during cyclic L-U process correlate with reduced damage degree, and smaller debris particles with a higher fractal dimension when impact failure occurs, indicating a more severe impact failure. (5) With multiple cycles of L-U, the cracks inside the sample gradually extend and expand from around the hole to the outside. The greater the load and the number of cycles, the more serious the crack damage will be. (6) In the practical mining process, it is crucial to reinforce roadway interiors while minimizing low-loading cyclic disturbances induced by MMD. The study has obtained the deformation evolution rules and failure characteristics of coal under MMD, providing a theoretical basis for the prevention and control of corresponding engineering disasters.

Experimental study on the compression and shear deformation evolution of coal pillar dam samples

To understand the mechanical properties and deformation failure patterns of coal pillar dams in gently inclined coal seam mine underground reservoirs, compression-shear coupling tests with variable angles were conducted on coal pillar dam samples under different saturation states. The digital image correlation (DIC) technique was utilized to obtain the deformation patterns of the displacement field throughout the compression-shear failure process of the samples. Numerical simulations were used to perform a comparative analysis and validation of the experimental results. The results indicated that the load-bearing capacity of the coal pillar dam samples decreased by 12.8–17.4% under water-saturated conditions. For every 5° increase in the inclination angle, the load-bearing capacity of the coal pillar dam samples decreased by an average of 3.53%. The normal stress and shear stress on the shear surface of the saturated samples were both lower than those of the natural samples, and both exhibited a linear variation with increasing inclination angle. The deformation evolution of the coal pillar dam samples under different test conditions exhibited similarity. The initial positive and negative displacement extremities in the horizontal direction were located at the lower right and upper left corners of the samples, respectively. Ultimately, the displacement field of the samples showed a pattern of smaller displacements at the top and larger displacements at the bottom, with negative values at the top and positive values at the bottom, distributed along the direction of the sample’s bedding. The saturated state and the increase in inclination both had a weakening effect on the load-bearing performance of the samples but had a relatively small impact on the differences in the displacement field deformation patterns. The research results can provide a reference for the study of the stability of coal pillar dams under similar conditions.

Extended influence coefficient method for meshing stiffness evaluation of spur gears considering rotor flexibility

Rotor-supported gears are applied in transmission systems, and the rotor flexiblility leads to the misalignment of the gear pair with multiple degrees of freedom, which ultimately leads to the decrease of meshing stiffness. To evaluate the meshing stiffness of rotor-supported gears, the extended influence coefficient method (EICM) is proposed in this paper. Firstly, the gear contact position adjustment under misalignment condition is carried out. Then, the extended influence coefficients of bending, shearing, axial compression, Hertzian contact and fillet foundation deformation of gears are derived to obtain the extended influence coefficient matrix. Afterward, the load-deformation equations under different contact states are obtained, and the meshing stiffness is calculated. Subsequently, a cantilever rotor-gear coupling dynamic model is established by the rigid body element-extended influence coefficient method (RBE-EICM), and the dynamic meshing stiffness considering rotor flexibility is obtained. The accuracy of EICM and RBE-EICM is verified by comparison with finite element method, literature methods and experimental data, respectively. Finally, the effects of supporting layout, input torque and rotor diameter on the dynamic characteristics of cantilever rotor-supported gears are discussed.

The Influence of the Degree of Tension and Compression of Copper on the Indentation Size Effect (ISE)

The present work deals with the relationship between the degree of cold plastic deformation (up to 55.3% in the neck area in the tensile test and up to 66.6% in the compression test) and the parameters of the Indentation Size Effect (ISE). The tested material consists of 97% wrought copper. The Hanemann tester (Carl Zeiss, Jena, Germany) was used to measure micro-hardness. The loads applied during the micro-hardness test were between 0.09807 N and 0.9807 N. The influence of the load on the degree of the micro-hardness and simultaneously on the ISE, expressed by the Meyer’s index n, was significant. The influence of load on the ISE parameters was also evaluated using the Meyer’s index n, the PSR method, and the Hays–Kendall approach. For the undeformed sample, the Meyer’s index was close to 2, with the increase in the degree of tensile and compressive deformation increasing its “reverse” character (n &gt; 2).

Compressive Mechanical Properties and Energy Absorption of Cubic Spherical Hollow Cellular Material Based on the Rod and Curved Surface Structure

Cellular materials, such as lattices and honeycombs, were widely used for structural protection owing to their excellent mechanical properties. By combining the excellent characteristics of lattice and honeycomb curved surface structures, this study designed a cell called Cubic Spherical Hollow (CSH), which had the advantages of orthogonal isotropy and better spatial connectivity. Inspired by the micro-structural arrangement of bamboo fiber and conch shell, we designed the new CSH cellular materials through the interlayer offset strategy. Then, the effects of interlayer offset on the mechanical properties and compression deformation behavior were explored experimentally and simulatively. Compared with other cellular materials, CSH cellular materials exhibited excellent mechanical properties with higher specific strength and specific modulus. The arrangement offsets of the CSH cells between different layers led to a change in the deformation mechanism from a rod’s compressive mode to a combination of a rod’s compressive mode and curved surface’s bending mode. The initial peak stress and plateau stress decreased with the increased arrangement offsets of the CSH since the extruded protrusions of the structure filled the holes and reduced the lateral expansion behavior of the material in the pressurized environment. This phenomenon also reduced the transverse expansion and prevented the sudden change in stress in the constrained space, indicating that the structural deformation was stable and had excellent cushioning and energy absorption properties. In this study, the cellular material design strategy opens a new avenue for energy absorption.

Compressive behaviors and deformation mechanism of carbon fiber reinforced epoxy composites: A microscopic and molecular dynamics perspective

AbstractInvestigating the macro‐mechanical properties of polymer composites at the nanoscale is a challenging topic. Here we report the compressive performances of carbon fiber‐reinforced epoxy composites using molecular dynamics (MD) simulations. The evolution of microstructure and microscopic energy, including free volume, radius of gyration, dihedral angle, potential energy, and interaction energy, has been investigated to characterize compressive behaviors at the nanoscale. Molecular chains gradually bend, and the movement space of the molecular chains decreases during compression loading. The radius of gyration and dihedral angle are deformed into a state of irreversible plasticity to accommodate the microstructural transformation. The interaction energy increases and subsequently declines as the carbon fiber/epoxy interface gets closer, reflecting the transition of the internal structure. The inhomogeneity and interfacial concentration distribution of stress, and local molecular stiffness under various strains have been obtained to reveal the nanoscopic mechanism of epoxy failure and interface delamination during compression. This study reveals the compression behaviors and deformation mechanism of carbon fiber‐reinforced epoxy composites at the molecular level, providing directions and possibilities for molecular design and structural optimization of composites.Highlights The nanoscopic compression deformation of CFRP composites is studied. Microstructural evolution and conformation transformation are revealed. The evolution and transition of microscopic energy are analyzed. Micro‐mechanism of epoxy deformation and interface delamination is elucidated.

Large deformation of variable thickness woven composite preforms considering interlayer difference. Application: Forming simulation of a blade preform

The main objective of this work was to investigate the interlayer difference of 3D orthogonal woven fabrics (3DOWFs) during deformation. Tensile, shear, and compression tests were performed on two types of 3DOWFs with different layer numbers. To determine the variations in the deformation behavior within the fabric, a layer decomposition method was developed. This process involved the decomposition of the fabric into two layers, the inner layer and the outer layer, depending on the difference in structural features of the yarn. Then the deformation characteristics of the inner layer and outer layer were derived based on their series or parallel relationship in the load path. The results indicate that there are noticeable variations in the deformation characteristics among the layers of 3DOWF, which are associated with the interwoven structure of the yarns. In particular, in compression deformation, the difference in yarn structure causes the initial stage (Compressive strain &lt;0.2) of fabric compression deformation to be mostly attributed to the compression of the outer layer. Subsequently, the deformations of the inner layer and outer layer gradually tend to balance. Based on a simple anisotropic hyperelasticity model, the interlayer differences were considered in the blade preform simulation. The simulation result shows a good agreement with the preforming results. The results show that the interlayer difference has a significant impact on the deformation of the blade preform, particularly in the posterior edge region, which is not strongly compressed.

Study on the Consolidation Characteristics of Slurry-like Mud Treated by Flocculation-Solidification-High-Pressure Filtration Combined Method.

The disposal and reutilization of the enormous amounts of slurry-like mud (MS) dredged from navigation channel construction, ecological dredging, and other construction activities have been receiving increasing attention. In this paper, a flocculation-solidification-high-pressure filtration combined method (FSHCM) is used to treat MS, and the consolidation characteristics of The SHCM-treated MS are studied by conducting a series of one-dimensional consolidation compression tests. Various parameters, including the dosage of the curing agent, initial water content, and dry weight of the MS, are systematically analyzed to evaluate their influence on the consolidation behavior. The experimental results demonstrate that higher curing agent and initial water contents enhance the structural yield stress and compressive resistance, while increased dry weight decreases the structural yield stress but increases the compressive strain and void ratio. As the curing age increases, the ability of the FSHCM-treated MS to resist compressive deformation is further enhanced. In addition, the compressibility of the mud cake samples changes significantly at the yield point. This study has practical guiding significance for the optimal design and long-term application of FSHCM-treated MS.

Synergistic effect of B and Y on the corrosion of S31254 super austenitic stainless steel under stress

The corrosion behavior of S31254 microalloying with B and Y was investigated after experiencing the tensile and compressive deformation. After three-point bending deformation test, the local misorientation and plastic deformation caused by tensile deformation were larger than compressive deformation. The synergistic effect of B and Y reduced local residual stress of samples after both tensile deformation and compressive deformation. Electrochemical test showed that the synergistic effect of B and Y enhanced corrosion resistance more effectively than microalloying with B alone. In the immersion corrosion test, the tensile region showed higher stress corrosion sensitivity due to the higher plastic deformation than that in compressive region. The 50B+50Y sample exhibited better corrosion resistance than 50B sample and 0B sample in the tensile region with low plastic deformation. With the decrease of tensile deformation, the synergistic effect of B and Y on reducing the corrosion sensitivity was more obviously than B alone.

Selective laser melting fabrication of body-temperature shape memory NiTi alloy for 4D-printed orthopedic implants

ABSTRACT SLM fabrication of NiTi alloy is receiving increasing attention. However, the relatively high austenite transformation finish (Af) temperature is the main problem for biomedical applications. In this study, it was found that phase transformation temperature (PTT) increased with increasing laser power, decreasing scanning speed, and decreasing hatch spacing. The combination of PPs with an energy density of less than 75 J/mm³ is expected to yield the Af temperature below 37 °C. P = 80 W, v = 600 mm/s, and h = 70 μm were identified as the optimal combination because of a good tensile strength of 612 MPa and a peak shape recovery rate of 96.94%. Biocompatibility assessment showed that SLM-NiTi porous scaffolds supported pre-osteoblast survival and proliferation. A patient-specific mesh-like supporting prosthesis was designed to show the prospect of 4D-printed orthopedics implant. In clinical application, SLM-NiTi prosthesis could reduce bony window and facilitate easier insertion through compressive deformation.

Noncircular Slip Surface Search on Slopes Based on Minimum Potential Energy Method and Improved SA Algorithm

ABSTRACTThe limit equilibrium method has been widely used in the study of searching the slip surface of slopes. However, the method ignores the deformation characteristics of the rock mass and assumes that the shape of the slip surface is circular, which is quite different from the actual situation of the slope. For this reason, this paper proposes a fast search method for noncircular slip surface considering the deformation characteristics of the rock mass. The method is able to calculate the compression and shear deformation energies stored in the slip surface, as well as the virtual displacement generated by the slide mass when the slope is in a critical equilibrium state. The direction of motion of the slide mass is further calculated from the magnitude of the virtual displacement. In addition, this paper improves the generation of new solutions in the simulated annealing (SA) algorithm for the structural characteristics of the slip surface of the slope, thus achieving a fast search of the slip surface. Finally, the method of this paper is compared with the test question of ACADS and the simulation results of the finite difference method (FDM) to verify the effectiveness of the method of this paper.

High Work Hardening Index of Fe35Ni35Cr20Mn10 High-Entropy Alloy during Compression Deformation

High Work Hardening Index of Fe35Ni35Cr20Mn10 High-Entropy Alloy during Compression Deformation

Composite Fiber Wrapping Techniques for Enhanced Concrete Mechanics

This study systematically investigates the enhancement effects of different fiber-reinforced polymer (FRP) materials on the axial compressive performance of concrete. Through experimental evaluations of single-layer, double-layer, and composite FRP reinforcement techniques, the impact of various FRP materials and their combinations on concrete’s axial compressive strength and deformation characteristics was assessed. The results indicate that single-layer CFRP reinforcement significantly improves concrete axial compressive strength and stiffness, while double-layer CFRP further optimizes stress distribution and load-bearing capacity. Among the composite FRP reinforcements, the combination with CFRP as the outer layer demonstrated superior performance in enhancing the overall structural integrity. Additionally, numerical analyses of the mechanical behavior of the reinforced structures were conducted using ABAQUS 2023HF2 finite element software, which validated the experimental findings and elucidated the mechanisms by which FRP influences the internal stress field of concrete. This research provides theoretical support and empirical data for the optimized design and practical application of FRP reinforcement technologies in engineering.