Compression Characteristics Research Articles

Design and Energy Absorption Study of an Asymmetric Windmill‐Style Negative Poisson's Ratio Honeycomb Structures

The negative Poisson's ratio (NPR) structure, as one of the representatives of advanced lightweight honeycomb materials, has good application prospects in aerospace, vehicles, biomedical, and other fields due to its unique deformation mechanism and huge energy absorption potential. In this article, a 2D asymmetric windmill‐style composite honeycomb (AWH) with NPR effects is presented and its compression properties are systematically assessed using both axial compression experiments and simulations. Through the experimental results, the accuracy and applicability of the finite‐element model are verified, indicating that the shape of the rotating arrangement and the stable internal design of the triangle make it have significantly higher energy absorption capacity than traditional symmetric reentrant honeycomb structures. In addition, the influence of the height, width, and cell spacing of asymmetric unit cell indentation points on the compression characteristics of AWH under axial quasi‐static compression conditions is further analyzed through orthogonal simulation experiments. In this study, a certain theoretical basis for the design and energy absorption application of NPR materials is provided, indicating that AWH has excellent mechanical properties and broad application prospects.

Exploring the compression and adsorption characteristics of anthracite nanopores in N2/CO2: A new perspective from synchrotron radiation SAXS

Exploring the compression and adsorption characteristics of anthracite nanopores in N2/CO2: A new perspective from synchrotron radiation SAXS

Pore–Water Salinity Effect on the Compression and Hydraulic Characteristics of Saturated Saline Soils

Pore–Water Salinity Effect on the Compression and Hydraulic Characteristics of Saturated Saline Soils

Axial compressive characteristics and crashworthiness of damaged composites/metal hybrid structures by acoustic emission, infrared thermography and micro-CT

Axial compressive characteristics and crashworthiness of damaged composites/metal hybrid structures by acoustic emission, infrared thermography and micro-CT

Investigation on structure stability and damage mechanism of cemented paste backfill under the coupling effect of water-static load

Cemented paste backfill (CPB) is easy to withstand the coupling effect of the mining operation equipment's crushing, water immersion, forming all kinds of intrinsic or extrinsic defects affecting its load-bearing capacity. In this paper, the initial immersion age and immersion time were used as variables, the damage and uniaxial compression characteristics of CPB under the coupling effect of water-static load were explored. Results show that the damage of water-immersed CPB under static load are mainly affected by water lubrication and pore water pressure and it improves the plastic deformation of CPB and weakens the energy storage capacity. When the initial immersion age was 3d, the effect is more significant. Water immersion increases the rate of damage with strain before peak strain and decreases the rate of damage with strain after peak strain. The strength of CPB varies from 0.3MPa to 0.8MPa at the same initial immersion age. The damage constitutive model of CPB under water-static load coupling is established, and the damage mechanism is revealed. Compared with the immersion time, reducing the initial immersion age is the key factor to improve the structure stability of CPB.

Preliminary Investigations on Strength Properties of Concrete Using Addition of Alccofine

This study presents preliminary investigations on the strength properties of concrete using addition of Alccofine. Concrete mixtures were prepared with varying percentages of Alccofine ranging from 0% to 20% and tested for compression strength and splitting tensile strength after 7, 14 & 28 days of curing. During the first week of curing (7 days), the concrete gains initial strength. Extending the curing period to 14 days allows for further hydration and strength development in the concrete. The 28-days of curing period is a critical milestone in concrete curing, as it represents the standard duration for assessing the concrete's compressive strength characteristics. The optimum percentage of Alccofine was arrived at15%. Exceeding the optimum percentage of Alccofine (20%) can lead to an adverse effect on strength due to potential issues like excessive pozzolanic reactions or changes in the concrete's microstructure. This information will help in determining the optimal proportion of Alccofine for achieving the desired strength and performance characteristics in the concrete mixtures.

Impact of material characteristics of cloth on the gripping force and performance of finger grippers

With the rising demand for automation and robotization in the textile industry, a variety of gripping solutions for textile materials has been developed in recent years. The increase in finger grippers is noticeable, however, a difference in the applicability and the holding force of finger grippers can be observed. Understanding the correlation between characteristics of the picked up textile materials, the style, coating and material of the gripper and the repeatability of the pick up process and the gripping force is crucial for their successful industrial integration. In this paper, the correlations between the properties of the different textiles and the gripping performance of a finger gripper are investigated. Bending stiffness, lateral compressibility, friction parameters and other textile characteristics are compared to the gripping force of the gripper with the selected textiles. The most important parameters are selected by principal component analysis and investigated for correlation.

Influence of fines content on the compression characteristics of calcareous sand and the related meso-mechanism

Influence of fines content on the compression characteristics of calcareous sand and the related meso-mechanism

Structural Analysis and Processing Characterization of Chitins Extracted from Different Sources.

The characteristics of three different types of chitin extracted from commonly used seafood organisms; namely crabs, shrimps, and squids were investigated. X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) were employed to analyze these chitins' polymorphic structure and morphology. Bulk and tapped density measurements, along with Kawakita analysis, were used to assess the flowability and compression behaviour of the chitin powders. Chitin extracted from crabs and shrimp exhibited the α-polymorphic form, while chitin from squid showed the β-polymorphic form. SEM images of the two forms revealed distinct differences in chitin layer arrangement, with the α-form appearing more compact due to the anti-parallel alignment of its polymer chains. Both bulk and tapped density measurements and the calculated Hausner ratio (HR) and Carr Index (CI) indicated poor flowability for these chitins. However, Kawakita's analysis of compression and compaction properties demonstrated that both polymorphs are compressible, though they differ in their extent of compaction. Regardless of their source, chitin compacts exhibited high crushing strength. Based on the observed morphology, flowability, and compression characteristics, a blend of α- and β-polymorphic chitin could be an effective excipient for pharmaceutical solid dosage forms.

Experimental study on aeration characteristics of plunging wave impact on a vertical cylinder

The impact force exerted by plunging breakers on structures is most pronounced, with the impact pressure being most sensitive to the changes in air entrainment, posing a threat to the structural safety of offshore wind turbines. However, the current explanations of the high impact force mechanisms in plunging waves are relatively superficial, and the relationship between the air entrainment motion and pressure oscillations remains unclear. According to the experimentally obtained pressure characteristics and the formation of entrapped air, this paper systematically divides the process of plunging wave impact on a vertical cylinder into three stages: breaking wave crest impact, entrained air cavity impact, and plume impact. Employing a bubble image velocimetry platform to visualize flow field characteristics and quantify turbulence intensity, we investigated the connection between gas motion and impact loads. The results indicate that the conversion of gas energy is closely related to the load characteristics, with the maximum impact force occurring near the peak of the energy gradient. The gas movement significantly influences pressure oscillations, which are positively correlated with the gas's physical compression and expansion characteristics. This study has uncovered new insights into the phenomenon of plunging waves impacting wind turbine towers and has enhanced the understanding of its load characteristics.

Dynamic compression mechanical behaviour and ignition characteristics of aluminium-containing PBX explosives with different densities

Abstract Due to the limitations of the processing technology, there are inevitably some differences in the explosive charge density, so that the material exhibits different mechanical behaviour and ignition characteristics, affecting the safe use of explosives. In order to study the dynamic compressive mechanical behaviour and ignition characteristics of an aluminium-containing PBX explosive with different densities, the samples with different densities were loaded quasi-statically and dynamically using electronic universal testing machine, split Hopkinson pressure bar and drop-weight loading device. The compressive stress-strain curves at different strain rates and the critical ignition height were obtained. A viscoelastic statistical cracking principal model (Visco-SCRAM) subroutine was written to analyse the internal mechanical response of aluminium-containing PBX explosives of different densities under drop hammer impact loading. The results show that the aluminium-containing PBX explosive has a pronounced strain rate sensitivity and density dependence, with the modulus of elasticity and peak stress increasing with increasing density and strain rate. Sample average density of 1.65, 1.70 and 1.74 g/cm3 the maximum stress of the explosive unresponsive and the fall height of 2500mm, more than 1000MPa; 2200mm, more than 825MPa; 2400mm, more than 907MPa, respectively. With the increase of the average density of the charge, the maximum stress and fall height of the unreacted explosives showed a tendency of decreasing and then increasing. Comprehensive analysis of test and numerical calculation results, the main influences on the ignition characteristics of low and high density samples are initial damage to the charge and mechanical properties, respectively.

Структурa і властивості матеріалів Fe—Al—Ga в області концентрацій, збагачених залізом

The structure and mechanical properties of materials of the Fe—Al—Ga system (in the concentration range of 78—82% (wt.) Fe), obtained by sintering at 1150 oC in Ar medium for 1 hour, were studied. The starting materials were mixtures of Fe, Al powders and crushed Fe—Ga ligature alloy of equiatomic composition. Seven mixtures were produced, of which two mixtures had a binare compo¬sition (% (wt.)): Fe—17,5Al and Fe—21,4Ga; and all the others were three-component, with gradual substitution of Al for Ga. The phase composition of the samples was studied by the methods of X-ray diffraction and local X-ray microspectral analyses. To determine the mechanical characteristics, the Brinell method was used, microdurometric studies were carried out, and mechanical tests of the samples were carried out under conditions of uniaxial compression. The effect of Al on the change in the porosity of Fe—Al—Ga ternary alloys and the maximum manifestation of the “swelling” effect for Fe—Al composition samples was established. It is shown that the main phase of the obtained materials is a solid solution based on Fe, in which Al and Ga are dissolved in the appropriate proportions. In the Fe—Al samples and in the samples of the ternary composition, there are local separations of phases containing, in addition to the main metals, carbon and oxygen in significant quantities. In the structure of Fe—Ga samples, carbon is not detected, and oxygen is present in a small amount. The results of the mechanical compression tests showed that the Fe—21,4Ga composition samples, like the pure Fe samples, are quite plastic and do not break up to a degree of compression of 75—82%. For materials with binary composition with Ga, an increase in the elastic range was recorded compared to pure Fe, and the replacement of a small proportion of Ga with Al (up to 2% by weight) in the material composition contributes to its strengthening. Keywords: Fe, Al, Ga, microstructure, phase formation, microhardness, mechanical compression characteristics.

Uniaxial Compressive Failure Characteristics and Fractal Analysis of Mud–Sand Composite Rock Samples Based on Acoustic Emission Tests

In order to study the influence of rock combination types on their mechanical properties and failure characteristics, uniaxial compression tests of single rock samples and combined rock samples were conducted. Acoustic emission (AE) signals during the test process were collected, and the differences in AE signals of single rock samples and combined rock samples were studied based on the fractal theory. The results showed that the peak strength, elastic modulus, peak strain, and failure degree of the combined rock samples are all between those of the two single rock samples. The AE ringing count gradually increases with the loading process and suddenly increases to the maximum when the rock sample fails. During this process, the phase trajectory volume corresponding to the ringing count shows an evolution law of first decreasing and then increasing, while the correlation dimension corresponding to the ringing count signal shows an overall evolution law of first increasing and then decreasing. The results indicate that the phase trajectory volume, correlation dimension, and crack changes have a consistent dynamic change. Therefore, the phase trajectory and correlation dimension are effective tools to describe the pore change characteristics of rock combinations.

Isotropic compression and triaxial shear characteristics of coral sand under high confining pressure and related particle breakage

Isotropic compression and triaxial shear characteristics of coral sand under high confining pressure and related particle breakage

Triaxial compression and shear strength characteristics of two-stage concrete: an experimental study

The research necessity stems from the need to understand and evaluate the performance of Two-Stage Concrete (TSC) under triaxial compression conditions, as prior studies have predominantly focused on uniaxial and biaxial testing of conventional concrete (CC). This study represents the first comprehensive investigation into the triaxial compressive strength and related mechanical properties of TSC, addressing a critical gap in the existing body of literature. Three different mixtures were prepared, including one CC and two TSC variants with varying cement content. The results and behavior of these mixtures were compared to assess their performance. Findings reveal that TSC, particularly those types with finer aggregates, demonstrates superior shear strength, achieving up to 52.4 MPa under dry conditions, in contrast to the 48.38 MPa observed in CC. Furthermore, TSC exhibits remarkable stress tolerance, withstanding up to 82.04 MPa, significantly outperforming CC, which withstands only 69.61 MPa under similar conditions. This behavior can be attributed to the higher coarse aggregate content, the increased interaction and contact points between coarse aggregates, the improved bonding between them, and the inherent properties of the grout. TSC also maintains a higher modulus of elasticity and internal friction angles, indicating superior deformation behavior and shear resistance. Additionally, TSC shows greater resilience to moisture, suggesting its potential suitability for use in variable moisture environments. These properties highlight the strength of TSC for high-load applications and its suitability for infrastructure prone to environmental fluctuations.

Dynamic strength criterion of concrete utilizing dynamic coordinates

AbstractThe effects of strain rate on the strength of concrete should be considered when analyzing the dynamic responses of concrete structures subjected to earthquakes or explosions. This paper shows that the effect of strain rate on strength characteristics can be attributed to an increase in cohesion. Notably, the effects of friction, hydrostatic pressure, and intermediate principal stress tend to remain rate‐independent under the appropriate reference system. Consequently, a dynamic coordinate system is established to account for the effects of strain rate on isotropic tensile strength. In this dynamic coordinate system, the strength envelopes for concrete closely resemble those in quasi‐static conditions under varying strain rates, as defined in the unified strength criterion. Using this proposed dynamic strength criterion, this paper explores the dynamic characteristics of different stress paths, including uniaxial, biaxial, and triaxial compression and tension. The predictions, both in terms of tendencies and magnitudes, are consistent with test results. The proposed method enables the extension of most strength criteria to dynamic scenarios by introducing two additional parameters with clear physical interpretations. This advancement enhances the current understanding of dynamic strength characteristics and provides a theoretical foundation for dynamic response analysis.

An Empirical Investigation of Static Compression Tests on Mortar Composite Materials with Different Proportions of Fly Ash

The engineering of composite mortar materials presents substantial economic advantages and significant potential for advancement in the construction sector, particularly through applications such as plant vases, coral transplant media, seawalls, wall decorations, bricks, paving blocks, and acoustic panels. The use of fly ash, an industrial byproduct, can facilitate the production of high-quality materials in alignment with the government’s circular economy initiatives. This study employs a mortar mixture with a 1:1 ratio combined with varying compositions of fly ash at 10%, 30%, and 50%, utilizing an experimental testing approach that includes a static load compression test. The purpose of the compression testing apparatus is to ascertain the compressive strength characteristics and the mass percentage of the materials. The findings revealed that the maximum compressive strength achieved with 10% fly ash was 34.07 MPa; however, variations in the fly ash composition led to a reduction in the material's toughness properties by 10.42% and 16.53%, respectively. The recorded compressive strength values comply with the quality standards set forth in SNI 03-0691-1996 for paving blocks classified as type B quality. Furthermore, the variations in composition positively influenced the mass percentage, with considerable increases of 66.67% and 45.33% corresponding to the differing fly ash compositions.

Comparative Study on the Impact of Various Non-Metallic Fibres on High-Performance Concrete Properties

The performance of high-performance concrete has been enhanced in the present study by incorporating non-metallic fibres without altering the binder content. The impact of these fibres on high-performance concrete flexural and compression characteristics and the arrangement of fibres within the composite were systematically analysed. Unlike conventional practices, the authors of the research introduce various non-metallic fibres, including alkali-resistant glass fibres, carbon microfibers, three types of polypropylene microfibers, and one type of polyvinyl alcohol fibre while maintaining an equal amount of binder. The research aims to comprehensively evaluate the fibre’s influence on cement composite properties. Various types of non-metallic fibres, highlighting differences in diameters and their physical-mechanical properties with a constant amount by volume, have been considered in the research. Alkali-resistant glass and carbon fibres exhibit low values of residual post-cracking force but polyvinyl alcohol fibres demonstrate the best post-cracking behaviour, with a residual post-cracking force value. This detailed examination of fibre distribution and composition sheds light on the nuanced effects on fresh and hardened concrete properties. Notably, this work diverges from existing research by maintaining a constant binder amount and considering the quantitative distribution of fibres in a unit volume of the cement matrix, along with their aspect ratio. These findings provide valuable insights for selecting the most suitable non-metallic fibres for enhancing high-performance concrete properties.

Anatomical Characteristics of Cervicomedullary Compression on MRI Scans in Children with Achondroplasia.

This retrospective study assessed anatomical characteristics of cervicomedullary compression in children with achondroplasia. Twelve anatomical parameters were analyzed (foramen magnum diameter and area; myelon area; clivus length; tentorium and occipital angles; brainstem volume outside the posterior fossa; and posterior fossa, cerebellum, supratentorial ventricular system, intracranial cerebrospinal fluid, and fourth ventricle volumes) from sagittal and transversal T1- and T2-weighted magnetic resonance imaging (MRI) scans from 37 children with achondroplasia aged ≤ 4 years (median [range] 0.8 [0.1-3.6] years) and compared with scans from 37 children without achondroplasia (median age 1.5 [0-3.9] years). Mann-Whitney U testing was used for between-group comparisons. Foramen magnum diameter and area were significantly smaller in children with achondroplasia compared with the reference group (mean 10.0 vs. 16.1 mm [p < 0.001] and 109.0 vs. 160.8 mm2 [p = 0.005], respectively). The tentorial angle was also steeper in children with achondroplasia (mean 47.6 vs. 38.1 degrees; p < 0.001), while the clivus was significantly shorter (mean 23.5 vs. 30.3 mm; p < 0.001). Significant differences were also observed in myelon area, occipital angle, fourth ventricle, intracranial cerebrospinal fluid and supratentorial ventricular volumes, and the volume of brainstem protruding beyond the posterior fossa (all p < 0.05). MRI analysis of brain structures may provide a standardized value to indicate decompression surgery in children with achondroplasia.

Ultrastrong SiC/LDHs biomass aerogel with exceptional fire safety behavior

Assembled Silicon Carbide/Layered Metal Hydroxides (SiCm/LDHs) in macroscopic biomass aerogels have challenges such as weak interfacial interactions, which degrade the mechanical properties. We successfully synthesized silicon carbide/cobalt-aluminum layered double hydroxide/magnesium hydroxide (MOH) ternary composites with high aspect ratios to improve the flame retardant and smoke suppression properties of polyvinyl alcohol (PVA)/sodium alginate (SA) biomass aerogel (PS). The inclusion of SiCm/LDH/MOH (2 wt%) greatly intensified the charring effect of PS, leading to a notable suppression of flame combustion and a reduction in smoke production. Specifically, the peak heat release rate (pHRR) and total smoke release (TSR) were decreased by 18.4% and 30.5%, respectively, in comparison to pure PS. The compressive characteristics of PS aerogels were notably enhanced through the incorporation of SiCm/LDH/MOH, particularly PS-S/L/M−4%, which exhibited a 220.4% increase compared to pure PS. The favorable formation of multiple hydrogen bonds and interconnected interfacial structures in ternary composites thus synergistically contributes to the achievement of superior mechanical and flame retardant properties. Our work offers a brighter future for the green manufacturing of biomass aerogels reinforced with SiCm/LDHs.