Compressive Loading Research Articles

Study on the mechanical behaviour of multicell T-shaped concrete-filled steel tubular short columns under axial and eccentric compression

To investigate the mechanical performance of multicell T-shaped concrete-filled steel tubular (MCT-CFST) columns, five short columns composed of a rectangular cell and two U-shaped cells were tested under axial and eccentric compression loads. For the axial compression samples, the steel tube surface underwent wave buckling, and local buckling failure occurred along the X-axis direction of the section. For the eccentric compression samples, overall bending occurred first; then, local buckling deformation occurred on the surface of the steel tube. Furthermore, a finite element model (FEM) of MCT-CFST short columns was established in ABAQUS software. The FEMs were validated by the test results to further investigate the influence of the construction parameters on the axial and eccentric compression performance of the MCT-CFST short columns. Finally, the EC4, GB 50936 and JGJ 138 specifications were selected to predict the load-carrying capacity of the MCT-CFST short columns under eccentric loading. Compared with GB 50936, JGJ138 and EC4 yield good predictions according to the test and simulation results.

FEA Modeling and Verification of Structural Property of Large Sandwich Composite Antenna Structure

The composite sandwich structure applied to the subject of this study is an effectively designed structure that enhances the specific stiffness of the panel. It features CFRP face sheets, which are strong under tensile and compressive loads, on both sides of an aluminum honeycomb core, a porous structure that is weak in tension and compression but strong in bending. The subject of this study weighs over 4 tons and possesses the largest weight and size among composite antenna structures in the country. Due to the lack of many references for large composite structures, accurate material properties are obtained through specimen tests, and the finite element analysis model is experimentally validated to ensure it accurately represents the actual structure. Finally, the structural robustness is verified through the structural analysis results of the validated model.

Experimental assessment of damage and microplastic release during cyclic loading of clear aligners.

The widespread adoption of clear aligners in orthodontic treatments in recent years has necessitated a more precise examination of the mechanical properties of the devices currently available in orthodontics. Recent studies indicate that aligners, when exposed to the forces exerted during swallowing, undergo fatigue-like phenomena, leading to chip formation and cracks. The cumulative damage results in a compromised fit between the tooth and aligner, which is crucial for the effective execution of orthodontic treatment. Additionally, the formation of chips poses a potential risk to patients, as there is a possibility of inadvertently ingesting microplastics that become detached from the aligner over time. This study attempts to assess the release of microplastics from the aligners subjected to cyclic compressive loading. Three different aligners (Essix Ace, Ghost Aligner and Invisalign) are tested to simulate swallowing conditions over the aligner usage period. The mechanical performance is studied in terms of the energy absorbed by the aligner, which shows that the Essix Ace has a stable energy absorption behaviour, while the energy absorbed by the Invisalign is significantly higher than their counterparts. Ghost Aligner did not perform well in the cyclic compression tests. The microplastics (MPs) released by the aligners are examined under an optical microscope. A dimensional analysis based on k-means image segmentation and edge detection algorithm is developed to analyse the MPs. The dimensional analysis of the MPs revealed that the ingestion of the MPs released by all the three aligners does not pose a health risk.

Dislocation plasticity in c$c$‐axis nanopillar compression of wurtzite ceramics: A study using neural network potentials

AbstractCeramics typically exhibit brittle characteristics at room temperature. However, under high compressive stress conditions, such as during nanoindentation or compression tests on nanopillars, these materials can reach the necessary shear stress for dislocation nucleation and glide before fracture occurs. This allows for the observation of plastic deformation through dislocations even at room temperature. Yet, detailed insights into their atomic‐scale dislocation plasticity remain scarce. This study employs atomistic simulations to explore the dislocation plasticity in ‐oriented nanopillars of wurtzite ceramics (i.e., GaN and ZnO) under uniaxial [0001] compression, utilizing a specially developed first‐principles neural network interatomic potential. We observed activation of and dislocations, corroborating experimental findings from in‐situ compression tests. Moreover, a wurtzite‐to‐hexagonal phase transformation begins at facet edges and extends inward, forming wedge‐shaped regions. As compression progresses, dislocations nucleate at the wurtzite‐hexagonal phase boundary and spread throughout the nanopillar, contributing to a rougher surface texture. These quantitative results offer new insights into the plastic deformation behaviors of nanopillars under compressive loading, highlighting the potential of dislocation engineering in these ceramics.

STUDYING THE STRUCTURAL BEHAVIOR OF BRICK WALLS STRENGTHENED BY DAMAGED TIRES STRIPS

The present study involves strengthening process applied upon brick walls to increase their ultimate load carrying capacity or improving their ductility behavior by using different types of strengthening materials. These materials include either traditional well-known materials or newly proposed materials. The traditional materials include steel wire mesh (SWM) and carbon fiber-reinforced polymer sheet (CFRPS) while the proposed materials include recycled damaged tire strips (DTS). The purpose of using such abundant and polluted material is to satisfy, respectively, the economic considerations and clean environment in the field of enhancing the structural behavior of brick walls. Eight brick walls models were constructed with dimensions of (1200×1200×240) mm, respectively represent width, height and thickness of each model to be tested by 45° compressive loading. Results exhibited that, the SWM increases the ultimate load carrying capacity for the strengthened models to 51.85% compared to the non-strengthened model when placed on one side of the model. Also, the use of CFRPS placed on one side and on both sides of the strengthened models increases the ultimate load capacity respectively to 18.2% and 385% compared to the non-strengthened model. The DTS material has no ability to increase the ultimate load capacity (-18.2 %) but it successfully converts the brittle behavior of the brick walls to a ductile one. It is recommended to use DTS to increase the ductility for brick walls that are likely be damaged or collapsed to avoid the sudden failure.

Nonlinear vibrations of graphene nanoplates with arbitrarily orientated crack located in magnetic field using nonlocal elasticity theory

PurposeThe study explores frequency curves and natural frequencies as functions of crack length, crack angle, magnetic field strength and small size effects under the three boundary conditions.Design/methodology/approachThis study investigates the nonlinear dynamics of a single-layered graphene nanoplate with an arbitrarily oriented crack under the influence of a magnetic field. The research focuses on three boundary conditions: simply supported, clamped and clamped-simply supported. The crack effect is modeled by incorporating membrane forces and additional flexural moments created by the crack into the equation of motion.FindingsResults reveal that increasing the crack length, small size effects and magnetic field intensity reduces the flexural stiffness of the nanoplate, increases the compressive load and lowers its natural frequency. Additionally, excessive magnetic field intensity may lead to static buckling. The critical dimensionless magnetic fields are found to be 33.6, 95.1 and 72.3 for All edges of the nanoplate are simply supported (SSSS), fully clamped edges (CCCC) and two opposite edges are clamped and the other are simply supported (CSCS) nanoplates, respectively. Furthermore, for SSSS and CCCC boundary conditions, an increase in the crack angle results in a softening behavior of the hard spring. In contrast, the SCSC boundary condition exhibits the opposite behavior. These findings emphasize the importance of considering the effects of angled cracks and electromagnetic loads in the analysis and design of graphene-based nanostructures.Originality/valueNovel equations are derived to account for the applied loads induced by the magnetic field. The nonlinear equation of motion is discretized using the Galerkin technique, and its analytical response is obtained via the multiple time-scales perturbation technique.

Load Deflection Analysis of Beam-Column using Total Potential Energy (TPE) Principle

A modified TPE approach to perform finite deflection analysis of slender beam-column elements has been developed. The proposed approach utilizes the energy principal method and takes into account the geometric nonlinearity including the effects of axial force on bending stiffness, the end moments on axial stiffness (bowing), and the initial imperfection. A new equation of the deformation curve that approaches to the exact solution is used in the strain-displacement relation to obtain a more accurate beam-column response. The derived formulation of displacement of the beam-column under axial compressive load with single curvature bowing is presented with initial imperfection and different end eccentricities. The Green strain tensor equation is developed to consider higher-order bowing term. Nonlinear analysis of central finite deflection is carried out using Newton-Raphson iteration that includes high order terms of total potential energy (TPE). The beam-column stability is verified by computing the hessian determinant of the total potential energy. The validity of the new approach is established by comparing the numerical results obtained using the proposed equations against data previously published in the literature. Outputs from the analysis indicate that the proposed approach is capable of capturing the deflection of the beam-column with enhanced accuracy, ranging from 8.5% for e = 0.025 and up to 23.5% when e = 0.125.

An investigation into instantaneously tuning the EMI shielding characteristics of CNT-based nanocomposite biofoams in the X-band range by strain loading

The electromagnetic interference (EMI) shielding of CNT-based nanocomposite biofoams is capable of being tailored instantaneously by mechanical loading. In contrast to tuning the EMI shielding via nanofillers or by decoration process, the strain-activated EMI tailoring characteristics possess enormous potential that still await to be explored. To reveal this tailoring mechanism, a multi-scale electro-magneto-mechanically coupled homogenization model is developed to tailor the EMI characteristics of CNT-based nanocomposite biofoams in the X-band range (8.2–12.4 GHz). In this development, the elastic moduli, complex conductivity, and complex permeability are all selected as the homogenization variables. Four categories of interface effects are considered, including imperfect interface bonding, electron tunneling, Maxwell-Wagner-Sillars polarization, and electron hopping. The predicted EMI tailoring characteristics are validated by the experiment of CNT/wheat flour nanocomposite biofoam over a wide range of stain loading. The effective EMI shielding behavior decreases with the compressive loading, but it increases with the tensile loading. It is found that a CNT content higher than the percolation threshold is necessary to tailor the EMI shielding behavior of this nanocomposite foam via strain loading. This study can provide innovative insights to tune the EMI shielding characteristics of CNT-based nanocomposite biofoams in X-band instantaneously.

A computational study on dynamic behavior of articular cartilage under cyclic compressive loading and magnetic field.

The dynamic behavior of articular cartilage (a soft porous biological tissue) with strain-dependent nonlinear permeability under cyclic compressive loading and magnetic field is investigated computationally. The compressive force is applied on top surface of the cylindrical plug of the tissue by means of a porous filter. The study of mechanical and deformational behavior of soft porous tissues such as articular cartilage under dynamic compressive loading and magnetic field is useful in understanding the underlying mechano-biological process that may lead to the development of a treatment and recovery protocol in a diseased state. In the present study, a linear biphasic mixture theory of porous media has been employed to derive the governing equations in terms of solid displacement and interstitial fluid pressure in the tissue. Exact solutions for the solid displacement, fluid pressure, and relative fluid velocity are provided for the constant permeability case which have also been used to validate the numerical method. On the other hand, the full nonlinear problem has been solved numerically using the method of lines and the outcomes are presented graphically to assess the effects of various emerging parameters. The results indicate that there is an increase in the solid dilatation due to application of magnetic field and this effect is more prominent at relatively high loading frequencies. In general, a repeated compressive force has generated an oscillating positive-negative hydrostatic pressure within the tissue, however, a strong magnetic field at comparatively high loading frequency enforces the tissue to have only the positive (supra-ambient) pressure. The outcomes have also revealed that the pattern of the dynamic behavior of the tissue is strongly dependent on the loading frequency. A considerable phase shift in the dilatation and fluid pressure has been noticed due to the loading frequency as well as magnetic effects. It has also been found that the permeability parameter has a minimal impact on the solid deformation and fluid pressure in all scenarios with a very small phase shift.

Multiscale modeling of oxidation-fatigue damage mechanisms under compressive dwell-fatigue loading conditions for nickel-based single-crystal superalloy

Multiscale modeling of oxidation-fatigue damage mechanisms under compressive dwell-fatigue loading conditions for nickel-based single-crystal superalloy

Local buckling behaviour of wire arc additively manufactured steel I-sections under axial compression and combined loading

Local buckling behaviour of wire arc additively manufactured steel I-sections under axial compression and combined loading

What about the mechanical behaviour and modelling of arteries in radial direction?

Understanding the physiological behaviour of arteries in the radial direction is crucial for establishing a reference point to detect and analyse pathological changes. In this study, the influence of the radial component of the aorta will be investigated by performing experimental tests on porcine aortic tissue in the three main directions of the aorta: circumferential, longitudinal and radial. The results obtained in all directions will be analysed and compared in order to contribute to a comprehensive understanding of the healthy behaviour of the vessel. Our results demonstrate that the aorta exhibits nonlinear behaviour under compression and tensile loading in the radial direction. Moreover, tissue stiffening progresses more prominently under compression compared to tensile loading. We have found that the tensile stiffness in the ATA is higher compared to the other two regions examined. The Neo-Hookean and Demiray models were selected to describe the isotropic contribution when fitting the uniaxial response of the circumferential and longitudinal samples using the GOH model. Neo-Hookean model fall short (R2=0.235) in accurately replicating the observed behaviour of the aorta in the radial direction and Demiray model showing better fitting results (R2=0.994).

Prediction of vertebral failure under general loadings of compression, flexion, extension, and side-bending.

Bone pathologies such as osteoporosis and metastasis can significantly compromise the load-bearing capacity of the spinal column, increasing the risk of vertebral fractures, some of which may occur during routine physical activities. Currently, there is no clinical tool that accurately assesses the risk of vertebral fractures associated with these activities in osteoporotic and metastatic spines. In this paper, we develop and validate a quantitative computed tomography-based finite element analysis (QCT/FEA) method to predict vertebral fractures under general load conditions that simulate flexion, extension, and side-bending movements, reflecting the body's activities under various scenarios. Initially, QCT/FEA models of cadaveric spine cohorts were developed. The accuracy and verification of the methodology involved comparing the fracture force outcomes to those experimentally observed and measured under pure compression loading scenarios. The findings revealed a strong correlation between experimentally measured failure loads and those estimated computationally (R2=0.96, p<0.001). For the selected vertebral specimens, we examined the effects of four distinct boundary conditions that replicate flexion, extension, left side-bending, and right side-bending loads. The results showed that spine bending load conditions led to over a 62% reduction in failure force outcomes compared to pure compression loading conditions (p≤0.0143). The study also demonstrated asymmetrical strain distribution patterns when the loading condition shifted from pure compression to spine bending, resulting in larger strain values on one side of the bone and consequently reducing the failure load. The results of this study suggest that QCT/FEA can be effectively used to analyze various boundary conditions resembling real-world physical activities, providing a valuable tool for assessing vertebral fracture risks.

Mechanical function of the annulus fibrosus is preserved following quasi-static compression resulting in endplate fracture.

Vertebral fractures in young populations are associated with intervertebral disc disorders later in life. However, damage to the annulus fibrosus has been observed in rapidly loaded spines even without the subsequent occurrence of a fracture. Therefore, it may not be the fracture event that compromises the disc, but rather the manner in which the disc is loaded. The purpose of this study was to quantify the mechanical properties of the annulus fibrosus following quasi-static compressive loading of the motion segment either to sub-fracture or fracture-inducing magnitude. Porcine cervical motion segments were axial compressed at 0.1mm/s, either until endplate fracture occurred ('fracture group'), or until segments reached 75% of average fracture stress as determined from the fracture group ('sub-fracture group'). An unloaded control group was also included. Post-loading, three samples of the annulus were excised. The first was mounted in a 180o peel test configuration in order to quantify lamellar adhesion. The other two samples were excised from the superficial and midspan region of the annulus and were exposed to uniaxial tension to 50% strain. Lamellar adhesion and tensile annulus mechanics did not differ between the fracture and sub-fracture group, nor between the unloaded controls. Given the lack of differences in annular mechanical properties across the three conditions, it was concluded that under very slow, quasi-static compressive loading conditions, the annulus appeared undamaged even in the group that sustained a fracture; this is likely because a significant viscoelastic response was not generated in the disc under these slow loading conditions.

Pultruded Glass Fiber–Reinforced Polymer Composites under Eccentric Compression Loading

Pultruded Glass Fiber–Reinforced Polymer Composites under Eccentric Compression Loading

Feasibility of a novel back support device to improve spine stability and muscular activity during trunk flexion: A prospective cross-sectional study with healthy controls and low back pain subjects - preliminary.

Low back pain is a prevalent global condition often challenging to address due to the absence of a definitive diagnosis in over 80% of cases. Manual lifting, common in many work environments, contributes to low back pain due to lumbar spine stresses, and existing assistive technologies like abdominal belts and exoskeletons have limitations in managing low back pain effectively. This paper presents a novel back support device designed to generate abdominal compression during flexion activities, potentially enhancing lumbar stability through increased intra-abdominal pressure. The study involved 14 participants with chronic non-specific low back pain and 18 gender-matched healthy controls doing controlled movement tests with and without the support device. Results suggest that the back support device increased intra-abdominal pressure in both groups during various functional tasks, more notably in active flexion and lifting tasks (up to +43%). The device also contributed to decreasing lumbar range of motion during guided flexion (-18 to -37%, except at the lumbosacral junction in the low back pain group), emphasizing its potential impact in limiting excessive spinal movement. Muscle activity assessments revealed decreased activation during active flexion and lifting movements while wearing the device, suggesting the possibility to assist trunk stabilization without the corresponding antagonistic muscle activation and associated compressive load on the spine. These effects could help workers to maintain their activities in the workplace and help workers suffering from low back pain to gradually reintegrate work or physical activities, contributing to better overall management of back health.

Combined Loading Effects on the Buckling Strength of Q690 Steel Tubes: An Experimental and Numerical Study

Abstract: This study investigates the stability and buckling behavior of Q690 high-strength steel cylindrical tubes subjected to combined axial compression and bending loads. Experimental testing on 27 specimens, combined with finite element analysis using ABAQUS, revealed critical insights into load-bearing capacity, deformation patterns, and failure modes. The study found that geometric imperfections, such as initial out-of-roundness and local dents, and residual stresses significantly influenced the buckling strength of the tubes, particularly those with high diameter-to-thickness ratios. Finite Element Analysis (FEA) effectively modeled the complex behavior, with deviations from experimental results ranging from 5.6% to 7.9%. Based on these findings, design recommendations, including optimized D/t and slenderness ratios, are proposed to enhance structural safety and efficiency. These results contribute to a better understanding of Q690 steel behavior and can inform the development of improved design codes for critical infrastructure applications

Numerical Investigation Into Mechanical Behavior of Metastable Olivine During Phase Transformation: Implications for Deep‐Focus Earthquakes

AbstractOne hypothesized mechanism that triggers deep‐focus earthquakes in oceanic subducting slabs below ∼300 km depth is transformational faulting due to the olivine‐to‐spinel phase transition. This study uses finite element modeling to investigate phase transformation‐induced stress redistribution and material weakening in olivine. A thermodynamically consistent constitutive model is developed to capture the evolution of phase transformation in olivine under different pressure and temperature conditions. The overall numerical model enables considering multiscale material features, including the polycrystalline structure, mesoscale heterogeneity, and various phases or variants of phases at the microscopic level, and accounts for viscoplastic behaviors with thermo‐mechanical coupling effects. The model is validated with several benchmarks, including a phase diagram of phase transformation from olivine to spinel. The validated model is used to study the interactive behaviors between defects (heterogeneity) and phase transformation. The simulation results reveal that spinel formation under pressure initiates near inclusions and along the grain boundaries, consistent with experimental observations. At lower temperatures, the transformation leads to the formation of thin conjugate bands of spinel diagonal to the compression loading direction. Local stress analysis along these bands also suggests the initiation of faulting. In contrast, the numerical results at higher transformation rates show that significant spinel formation occurs over a larger area at elevated temperatures, leading to ductile behavior, which agrees with experimental findings. Numerical simulation of multiple inclusions under confined pressure also shows the formation of a network of spinel bands resembling phase‐transformation patterns observed in the laboratory experiments. Additionally, stress softening patterns due to phase transformation are similar to experimental observations.

Perilaku Lentur Kolom yang Diretrofit Menggunakan Wire Mesh dan Self Compacting Concrete Akibat Beban Siklik

Results of experimental and analytical study of the flexural behavior of retrofitted columns using wiremesh and SCC concrete due to cyclic loading. The purpose of this study was to analyze the strength of the column retrofitted using wiremesh and SCC due to cyclic loading. The test object consisted of 3 columns with a size of 300x300 mm, consisting of a control column (KK), a total reinforcement column (KR-1) and a reinforcement column in the approximate plastic hinge region (KR-2). From the test results, the flexural strength of the reinforced column is higher than that of the unreinforced column. The rate of increase in strength of KR-1 compared to KK is 46.68% in compression and 37.87% in tension. The rate of increase in the strength of KR-2 compared to the compressive load of KK is 41.71%, and the tensile load is 32.35%.

Engineered ionic polymer metal composites (eIPMCs) under dynamic compression loading conditions: theory and experiments

Abstract Engineered Ionic Polymer Metal Composites (eIPMCs) represent the next generation of IPMCs, soft electro-chemo-mechanically coupled smart materials used as actuators and sensors. Recent studies indicate that eIPMC sensors, featuring unique microstructures at the interface between the ionic polymer membrane and the electrode, exhibit enhanced electrochemical behavior and sensitivity under compression, as compared to traditional IPMCs. However, a complete and experimentally-validated model of how eIPMCs behave under dynamic compression loads is currently missing. In this paper, we develop an analytical model for eIPMC sensors, elucidating the role of the engineered interface, modeled as a separate material layer with unique mechanical and electrochemical properties. Theoretical predictions focus on the mechanical-to-electrochemical transduction response under dynamic compressive loads. Experimental verification is conducted on conventional IPMC and novel eIPMC samples fabricated using the polymer abrading technique. Electrochemical impedance spectroscopy is performed to study the effect of the engineered interface on the electrochemical properties. Open-circuit voltage and short-circuit current are measured under external compressive loads in different loading scenarios to demonstrate sensing performance. Results show good qualitative agreement between experimental trends and model predictions. Experiments over the frequency range 1-18 Hz demonstrate an increase of 220-290% in open-circuit voltage and 17-166% in short-circuit current sensitivity for eIPMCs over IPMCs.