Compressive Mechanical Properties Research Articles

Effects of post-processing curing parameters and gamma irradiation on the mechanical properties of medical graded vat photopolymerization parts

Purpose This paper aims to investigate the influence of post-curing temperature, post-curing time and gamma ray irradiation dose upon the tensile and compressive mechanical properties of the medical graded vat photopolymerization parts. Design/methodology/approach Medical graded vat photopolymerization specimens, made from photopolymer resin, were fabricated using bottom-up vat photopolymerization machine. Tensile and compressive tests were conducted to assess the mechanical properties. The specimens were categorized into uncured and post-curing groups. Temperature post-processing and/or gamma irradiation exposure were for post-curing specimens. The post-curing parameters considered included temperature levels of 50°C, 60°C and 70°C, with 1, 2, 3 and 4 h periods. For the gamma irradiation, the exposure doses were 25, 50, 75 and 100 kGy. Findings Post-curing improved the mechanical properties of medical graded vat photopolymerization parts for both tensile and compressive specimens. Post-curing temperature greater than 50°C or a prolonged post-curing period of more than 1 h made insignificant changes or deterioration in mechanical properties. The optimal post-curing condition was therefore a 50°C post-curing temperature with 1 h post-curing time. Exposure to gamma ray improved the compressive mechanical properties, but deteriorated tensile mechanical properties. Higher gamma irradiation doses could decrease the mechanical properties and also make the part more brittle, especially for doses more than 25 kGy. Originality/value The obtained results would be beneficial to the medical device manufacturer who fabricated the invasive temporary contact personalized surgical instruments by vat photopolymerization technique. In addition, it also raised awareness in excessive gamma sterilization in the medical graded vat photopolymerization parts.

Experimental Investigation of Compressive Concrete with Different Immersion Times and Its Stochastic Damage Model

Continuous large amounts of precipitation can lead to a rapid increase in the water content of concrete in village building foundations, which can adversely affect the mechanical properties, such as the compressive strength of concrete. There are few experimental studies on the compressive stochastic mechanical properties of concrete in the wet state after considering different soaking times (different water contents and saturations), but there is no corresponding stochastic damage principal structure model. In this study, the mechanical properties of concrete under different immersion times were tested to obtain the mechanical properties of the concrete degradation law, and the random damage intrinsic model of wet concrete was established. The results of this paper were compared with the classical test results from the literature to verify the validity of the model. The results show that the proposed stochastic damage model is able to consider both the effects of the saturation and the damage behavior of wet concrete under compression, which is beneficial to the structural design and maintenance protection of village buildings in areas with abundant precipitation.

Assessment of Mechanical Properties in Compression of Swine and Simulation of Bone Screw Loosening

Assessment of Mechanical Properties in Compression of Swine and Simulation of Bone Screw Loosening

Compressive Mechanical Properties and Water Absorption of Glass fiber-reinforced Plastics Pipes Aged in Caspian SeaWater

Compressive Mechanical Properties and Water Absorption of Glass fiber-reinforced Plastics Pipes Aged in Caspian SeaWater

Experimental study of the degradation of HDPE packaging under accelerated thermal aging

In this work, accelerated thermal aging at different temperatures was performed on high-density polyethylene (HDPE) bottles and specimens for food packaging. The degradation of HDPE was followed macroscopically by tensile and compression tests to evaluate the decrease in mechanical properties. The data obtained from these tests are used to calculate a new static damage law and the life fraction of this polymer. A prediction of the lifetime of HDPE was determined by thermogravimetric analysis (TGA) in dynamic mode. The evolution of the crystallinity rate during accelerated thermal aging was carried out using FOURIER transform infrared spectrometry (FTIR). The results obtained show a remarkable degradation of the mechanical properties in traction and compression by calculation of the static damage, and the physical and chemical properties by the analysis of the rate of crystallinity as well as the prediction by the law of Arrhenius.

Mechanical properties of uniaxial compression of total tailings paste under lateral restraint effect

After the filling of paste into the mined-out area, significant disparities are evident between the mechanical characteristics and the unconfined conditions, primarily caused by the lateral extrusion of the surrounding rock. To research the mechanical properties of paste under the influence of lateral restraint effect, a device was developed to apply lateral pressure to the paste. This was then combined with an existing uniaxial press machine to carry out uniaxial compression testing of the paste subject to lateral restraint effect. The device was used to carry out uniaxial compression tests under different curing ages and dry and wet conditions under the lateral restraint effect, and compared with the unconfined condition. The study revealed a considerable increase in the paste's strength caused by the lateral restraint effect, resulting in a growth rate ranging from 12.35% to 64.51%. The mathematical model of lateral stress and strength was established, and it was found that the two showed a significant quadratic function relationship. By acquiring the stress-strain data of the loading process, the evolution characteristics of the stress-strain curve of the paste under the influence of the lateral restraint effect are revealed, and the change rule of the elastic modulus is explored. Under the influence of the lateral restraint effect, the growth rate reaches 1.93% to 64.04%. When comparing the crack propagation characteristics of the paste with and without the influence of the lateral restraint effect, it was observed that the failure mode of the paste under uniaxial compression shifts from tensile failure to shear failure. Finally, this paper proposes the strength design method for backfill with considerations to the lateral restraint effect. The reliability of the suggested method is established through actual sampling results in the mine. The research findings hold significant guiding value for the secure and efficient extraction of paste backfill mines.

Fracture behaviour assessment of high-performance fibre-reinforced concrete at high strain rates using interpretable modelling approaches

High-performance fibre-reinforced concrete (HPFRC), a type of cementitious composite material known for its exceptional mechanical performance, has widespread applications in structures exposed to severe dynamic loading conditions. However, understanding nonlinear HPFRC fracture behaviour, particularly under high strain rates, remains challenging given the complexities of assessment procedures and cost-intensive nature of experiments. This study presents an interpretable framework for modelling and analysing HPFRC fracture strength at high strain rates. A wide range of machine learning methods, including ensemble techniques, were employed to capture multivariate effects of eight essential input features (e.g., mortar compressive strength, fibre physical and mechanical properties, cross-sectional area, and strain rate) on fracture strength response. To assess the derived models, a novel evaluation procedure was proposed involving a data-based analysis, employing established metrics (i.e., coefficient of determination, root mean squared error, and mean absolute error via K-fold cross-validation) and a domain experts-involved evaluation utilising global sensitivity analysis to discern first-order and higher-order interactions among input factors. The proposed approach efficiently yielded both quantitative and qualitative insights into crucial input factors governing HPFRC fracture strength with limited experimental data. The obtained findings highlight the significance of multivariate effects, such as the interaction between strain rate and fibre tensile strength, and between fibre volume and fibre diameter, on fracture behaviour. The proposed interpretable framework aims to provide a powerful tool for proactive material failure analysis by understanding fracture behaviour and identifying potential weak and strong interactions among input factors of HPFRC-based samples. Moreover, the utilisation of the proposed approach enables researchers and civil engineers to efficiently focus on the most critical input parameters during the early design stage and ensuring the structural integrity and safety of HPFRC-based constructions.

Study on mechanical properties and acoustic emission characteristics of deep diorite under uniaxial compression

The research object is diorite in the Lingbei TBM section of the Hanjiang-To-Weihe River Qinling tunnel, with a buried depth of over 1 km. Using MTS-2000 microcomputer-controlled electro-hydraulic servo universal testing machine and DS5-16b acoustic emission (AE) monitoring system, uniaxial compression and acoustic emission monitoring tests were carried out on rock samples, to study the uniaxial compression mechanical properties and acoustic emission characteristics of the deep diorite. The results of the study indicate that: (1) During uniaxial compression, diorite undergoes four stages: initial compaction, elasticity, yield and failure, in which the curve of the initial compaction stage is significantly smoother. The uniaxial compressive strength is 41.95 MPã102.42 MPa, with an average of 74.07 Mpa; The axial peak strain ranges from 1 % to 1.4 %, and the failure mode belongs to brittle ductile splitting failure. (2) The cumulative ringing count and energy showed a very slow increase trend during the calm period; After entering a surge period (with the appearance of Kaiser points), both show a significant transition state; During the slow increase period, the overall growth rate of the two slowed down and remained almost silent. (3) On the basis of the analysis of RA-AF values during the deformation and rupture process of diorite, it can be seen that the damage type of diorite is tensile damage by the significant low RA value and high AF value characteristics, which coincides with the actual damage fracture characteristics of the rocks in the sample. (4) During the compaction stage, there are few acoustic emission location points, which correspond to low energy and are mainly distributed at the higher and lower ends of the sample; After entering the elasticity stage, the number of positioning points significantly increases and gradually expands towards the middle; Near Kaiser point, the number of location points and corresponding energy are both in a sharp increase state, and this trend is in good agreement with the changes in the ringing count-time and energy-time curves. (5) The damage time mainly starts at the end of the calm period, and the pattern of change in the damage curve coincides with the localization point and energy evolution. The results of the research can be used as a referential basis for the development of the excavation, protection and other construction plans for the Lingbei TBM section of the Hanjiang-To-Weihe River Qinling tunnel or similar surrounding rock tunnels, as well as for further conducting triaxial unloading tests on diorite.

A natural multifunction and multiscale hierarchical matrix as a drug-eluting scaffold for biomedical applications.

Sea urchin spines are biogenic single crystals of magnesium calcite that are stiff, strong, damage tolerant and light and have a bicontinuous porous structure. Here, we showed that the removal of their intraskeletal organic matrix materials did not affect the compressive mechanical properties and generated an open porosity. This matrix was able to adsorb and release oxytetracycline, a broad-spectrum antibiotic. The drug-loaded sea urchin matrix induced bacterial cell death after 4 and 8 hours of incubation of both Gram-negative E. coli and Gram-positive S. aureus strains and this process induces an inhibition of bacterial cell adhesion. In conclusion, this study shows that thermally treated sea urchin spines are a compressive resistant and lightweight matrix able to load drugs and with potential use in spine fusion, a challenging application that requires withstanding high compressive loading.

牛粪压缩和应力松弛特性及其本构模型构建研究

In order to study the mechanical properties of compression and stress relaxation of manure under drainage conditions, the experiment was carried out with cattle manure as the object, and the constitutive models were improved to describe the stress-strain curves of compression and stress relaxation. The defined constitutive model was determined by parameter identification, and the influence laws of moisture content and filling mass on the compression and relaxation process were investigated. The results show that the improved Nishihara model and the five-component generalized Maxwell model can better describe the compression and stress relaxation properties of cattle manure, and the coefficients of determination of the parameters of the fitted intrinsic model are all greater than 0.9, with high fitting accuracy. The compression process was divided into three stages: exhaust, drainage, and viscoelastic-plastic deformation. The stress decay rate tended to change quickly and then slowly, and there was a negative correlation between the compressed mass, moisture content, and stress decay rate. Duncan's mean comparisons revealed that the differences in elastic modulus between different moisture content / compressed mass groups in the parameters of the cattle manure compression principal model were all significant (P<0.05). The differences in elastic modulus and coefficient of viscous attenuation between different moisture content groups in the parameters of the stress relaxation model were all significant. The study's results can provide the theoretical basis for the study and simulation of CM's compression and dewatering mechanism and provide support for the solid-liquid separator for livestock and poultry manure.

Experimental study of uniaxial compressive mechanical properties of rough jointed rock masses based on 3D printing

Abstract Roughness and inclination are important factors affecting the strength and deformation properties of jointed rock masses. Serrated joint specimens with varying joint roughness coefficient (JRC) and inclination angle were manufactured by 3D printing technique and cement mortar material. Then, uniaxial compression tests were performed for serrated joint specimens. The results show that when inclination angle equals 0° or 90°, the stress–strain curves of serrated joint specimens with various JRC values are basically the same and display a similar variation trend as that of the complete specimen, hence JRC presents a very little impact. When inclination angle varies from 30° to 60°, the stress–strain curves display a significant difference for various JRC values. Both the compressive strength and peak strain increase with the JRC value. With the increase in JRC value, the stress–strain curve exhibits a stress drop point, and with the further increase in JRC value, the stress drop point obviously delays or disappears directly. Variation in uniaxial compressive strength and deformation modulus with inclination angle is approximately U-shape for serrated joint specimens and displays typical anisotropic characteristics. Due to the variation in inclination angles and JRC values, failure modes of serrated joint specimens under uniaxial compression varies from splitting tensile or shear slip failure to compound tensile and shear failure. Rough serrated joint has a strengthening effect on the resistance ability to vertical load, and large roughness can effectively slow down the shear slip failure of jointed rock masses.

Effect of thermal modification on axial compression properties and hardness of laminated bamboo

Vacuum thermal modification is an environmentally friendly method to improve the durability and reduce insect infestation of bamboo, which has the advantages of preventing deformation, preventing oxidation of the bamboo surface, and uniformity of thermal conductivity compared to previous studies that used mediums such as nitrogen, air, or oil for heating. This study thermally modified laminated bamboo materials for 1 to 5 h under vacuum conditions ranging from 170 to 230 °C and evaluated their microstructure, surface hardness, water absorption, and axial compression mechanical properties. The results showed that compared with untreated laminated bamboo timber, the colour gradually deepened as the temperature and time of heat treatment increased, while the equilibrium moisture content of heat-treated laminated bamboo timber was reduced by about 4–27% and the density by about 11–18%. This phenomenon indicates that the cell walls of laminated bamboo become denser with increasing temperature, which leads to a significant decrease in the hygroscopicity of laminated bamboo. The dimensional stability of the material was improved. Regarding the macroscopic axial compression test, the results showed that the thermal modification treatment significantly increased the axial compression strength of laminated bamboo, and this improvement in mechanical properties was inversely related to the heat treatment temperature. In addition, through the nanoindentation test, we found that the laminated bamboo's surface hardness and modulus of elasticity showed an inflexion point when the treatment temperature reached 210 °C, indicating that the material properties changed significantly in this temperature range. Investigating the response mechanism between the temperature and time of vacuum thermal heat treatment and the mechanical properties of bamboo will contribute to the development or optimization of the thermal modification process, leading to materials with excellent properties and broadening the application areas.

Compression of additively manufactured PLA for biomedical applications: Effects of test conditions on properties of solid samples

Understanding the mechanical behaviour of additively manufactured (AM) biomedical polymeric devices under various loading regimes is important for tailoring their design to specific applications. This paper presents the results of an experimental study of compressive mechanical properties of AM cubic samples of biocompatible polylactic acid (PLA) manufactured with fused filament fabrication. The measured elastic modulus and ultimate compression strength were compared and analysed for varying testing parameters, such as strain rate and contact friction, for samples with different characteristic sizes. The changes in density of the samples were also assessed for evaluation of the extent of material compaction after deformation. Surface morphology of specimens was examined before and after compression tests using scanning electron and optical microscopy. Different types of defects induced by the manufacturing process and caused by the subsequent compressive deformation were studied and compared. The obtained results are useful for design and optimization of small-size biomedical devices, which require precise control of their structural morphology and mechanical behaviour.

CDEM-Based Numerical Simulation of Uniaxial Compressive Mechanical Properties of Rocks

Understanding the mechanical properties of rock is of great significance for the development of unconventional reservoirs. However, a large number of bedding makes the mechanical laws of rock unclear. To investigate the effect of bedding properties on the uniaxial mechanical properties of rock, the coal model containing bedding is developed based on the continuous–discontinuous method, and the effect of bedding angle, bedding strength, bedding number, and loading rate on the uniaxial mechanical properties of rock is investigated. The failure morphology, stress–strain evolution, peak stress, and fracture degrees are analyzed and discussed in detail. The reliability of the numerical model in this paper has been verified by comparison with the indoor experiments. The results show that when the bedding angle is 0°, the peak stress of the rock is maximum, 8.16 MPa, and when the bedding angle is 90°, the fracture degree of the rock is maximum, 3.74%. For the different bedding strengths, the peak stress first decreases linearly with the decrease of the bedding strength. The peak stress barely varies when the bedding strength is less than 0.5 MPa. The fracture degree of the rock shows a nonlinear increase with the increase in bedding strength. For different bedding numbers, the activation of the bedding is not related to the bedding number. The loading speed also has a great influence on the mechanical properties of rock. With the increase in loading rate, the difficulty of bedding activation gradually increases, and the complexity of fractures gradually increases. This study aims to further improve the understanding of the effect of bedding properties on the uniaxial mechanical properties of rock.

Ignition and energy release characteristics of energetic high-entropy alloy HfZrTiTa0.2Al0.8 under dynamic loading

Steel-like density HfZrTiTa0.2Al0.8 high entropy alloy (HEA) with a density of 7.78 g/cm3 is designed and fabricated as a novel energetic structural material (ESM). The microstructure, thermal analysis, compressive mechanical properties, ignition and energy release under dynamic loading are systemically investigated. The experimental results show that the HfZrTiTa0.2Al0.8 HEA has a single BCC solid solution structure, and spinodal decomposition with elements segregation in the nanoscale is observed. Thermal analysis shows the HEA keeps stable in the Ar atmosphere and the oxidizing reaction occurs in the Air atmosphere. The mechanical properties show brittle characteristics with maximum strength with 1520 MPa and fracture strain 0.07 and strain rate effect from 0.001s−1 to 3000s−1 is observed. Under high strain rate loading, the fracture-induced spark is observed, which is caused by an oxidizing reaction due to the rise. By direct ballistic test, the energy release velocity threshold is measured as 980 m/s, and the energy release intensity is more violent in higher velocity impact conditions. Moreover, the impact reaction degree is increased with increasing fragmentation degree and adiabatic temperature rise induced by impact. The designed HEA-ESM is a promising candidate that simultaneously possesses both high strength, high reactive heat and excellent energetic characteristics in the application field of high-strength ESM fragment.

Compressive mechanical properties of cottonseed

Understanding cottonseeds’ basic physical parameters and compressive mechanical properties is necessary in seed cotton packing and cottonseed processing. In this study, the basic physical parameters of three cottonseed varieties (Huiyuan 720, Xinluzao 61, and Xinluzao 74) under different moisture contents (6%, 9%, 12%, and 15%) were measured. These parameters include 1000-grain weight, triaxial dimension, and sphericity. The effects of different moisture, varieties, and compression orientation (horizontal and vertical) on the compressive mechanical properties of the cottonseed were studied, and the variance analysis of the experimental data showed that the triaxial dimension, 1000-grain weight, arithmetic mean diameter, and geometric mean diameter of cottonseeds of the same variety increased with an increase in moisture content. Extremely significant differences (p < 0.01) were found in the physical parameters among different varieties. The main factors affecting crushing force and apparent elastic modulus are moisture content, variety, and compression orientation. For deformation, the main factors are moisture content, compression orientation, and variety. Moreover, compression orientation, moisture content, and variety are the main factors affecting failure energy. The results obtained that the crushing force and apparent elastic modulus decreased, deformation increased, and failure energy decreased first and then increased with the increase in moisture content under the same cottonseed variety. The results also provided the basic physical parameters for the design parameter optimization of seed cotton harvesting and processing machinery.

Development of photocrosslinkable bioinks with improved electromechanical properties for 3D bioprinting of cardiac BioRings

Three-dimensional (3D) bioprinting is an advanced fabrication technique to build biomimetic constructs for different biomedical applications. Here, we developed composite bioinks based on photocrosslinkable natural polymers, gelatin methacryloyl (GelMA) and alginate methacrylate (AlgMA), and electroconductive reduced graphene oxide (rGO) nanomaterials. The photocrosslinked hydrogels indicated interconnected porous microarchitecture with detectable rGO nanosheets on the pore walls. The addition of AlgMA and rGO to GelMA bioinks significantly enhanced tensile and compressive mechanical properties, improved the rheological properties and printability of inks, and controlled the degradation profile of the constructs. The optimization was done based on the suitable electromechanical properties for cardiac tissue engineering applications. The ring-shaped cardiac constructs were further 3D bioprinted with different cardiac cell types (neonatal rat cardiomyocytes, cardiac fibroblasts, and HL-1 cells). The optimized bioink supported a high level of cardiac cell viability, proliferation, spreading, elongation, and alignment with functional hallmarks (e.g., calcium transient and cellular spontaneous beating). Proof-of-concept validation was demonstrated for utilizing this platform as a 3D bioprinted heart-on-a-chip model with automated high-throughput in the 12-well plates. The developed bioprinted cardiac model could be used for different applications, including drug screening and disease modeling.

Effects of dynamic velocity on the dynamic compressive mechanical properties and energy evolution of coal specimens

ABSTRACT Dynamic compressive parameters of coal specimens were driven not only by impact velocities, but also by preloaded confining pressure, and impact loading methods. This paper investigates the influences of dynamic parameters based on the split Hopkinson pressure bar (SHPB) experimental data obtained from the dynamic compressive impact tests on 12 coal specimens under four different impact velocity. The analysis of the experimental results confirmed that with an increase of dynamic velocity, and then the dynamic compressive strength is constantly increases. When the dynamic velocity is 8.10 m/s, and then reacheed the maximum dynamic strength of 25.11 MPa of the coal specimen. Furthermore, the dynamic velocity of 8.10 m/s was defined as the threshold value of the dynamic strength increased. The greater of dynamic velocity, the higher degree of fragmentation of the coal specimens. The transmitted energy, reflected energy, and absorbed energy of coal specimens shows a directly proportional relationship with the incident energy. The results highlight the first and second dynamic deformation moduli can clearly explained the deformation laws of elastic and plastic stages of the coal specimens. It is also found that the maximum of strain rate is 177.28 s−1 and the maximum ultimate strain is 2.47 × 10−2of the coal specimens. The research results were beneficial to supplement the coal-rock dynamics theory, thus also providing a direction for safety and effective mining and crushing in coal mines.

The Laser Selective Sintering Controlled Forming of Flexible TPMS Structures.

Sports equipment crafted from flexible mechanical metamaterials offers advantages due to its lightweight, comfort, and energy absorption, enhancing athletes' well-being and optimizing their competitive performance. The utilization of metamaterials in sports gear like insoles, protective equipment, and helmets has garnered increasing attention. In comparison to traditional truss and honeycomb metamaterials, the triply periodic minimal surface lattice structure stands out due to its parametric design capabilities, enabling controllable performance. Furthermore, the use of flexible materials empowers this structure to endure significant deformation while boasting a higher energy absorption capacity. Consequently, this study first introduces a parametric method based on the modeling equation of the triply periodic minimal surface structure and homogenization theory simulation. Experimental results demonstrate the efficacy of this method in designing triply periodic minimal surface lattice structures with a controllable and adjustable elastic modulus. Subsequently, the uniform flexible triply periodic minimal surface lattice structure is fabricated using laser selective sintering thermoplastic polyurethane technology. Compression tests and finite element simulations analyze the hyperelastic response characteristics, including the element type, deformation behavior, elastic modulus, and energy absorption performance, elucidating the stress-strain curve of the flexible lattice structure. Upon analyzing the compressive mechanical properties of the uniform flexible triply periodic minimal surface structure, it is evident that the structure's geometric shape and volume fraction predominantly influence its mechanical properties. Consequently, we delve into the advantages of gradient and hybrid lattice structure designs concerning their elasticity, energy absorption, and shock absorption.

Constitutive Model and Impact Induced Fragmentation of W-Zr Alloy

In this paper, two types of W-Zr alloy with different proportions were prepared. The dynamic and quasi-static compression mechanical properties of Zr-25%W alloy and Zr-50%W alloy at various strain rates were obtained. The results showed that the tungsten component could improve the mechanical strength of the alloy, while the zirconium component could significantly improve the plasticity of the alloy. The JC constitutive models of two types of W-Zr alloys and the KHL constitutive model of Zr-25%W alloy were proposed. The fitting parameters of JC model and KHL model were determined by the dynamic and quad-static compression tests. Dynamic impact tests of two types of W-Zr alloys were carried out in argon atmosphere at various velocities. The power law distribution theory for brittle materials could also describe the high-speed impact of W-Zr alloy.