Experimental Compression Data Research Articles

An Interactive Fluid–Solid Approach for Numerical Modeling of Composite Metal Foam Behavior under Compression

Composite metal foams (CMF) are renowned for their high strength‐to‐density ratio, high stiffness, and energy absorption capabilities. Homogenized finite element models of CMF have been numerically solved to understand the mechanical behavior of the material under a variety of external loading conditions. This work aims to pioneer a comprehensive finite element model for steel–steel composite metal foam by incorporating the interactions between embedded stainless‐steel hollow spheres with entrapped air inside stainless‐steel matrix. The material behavior of hollow spheres, surrounding matrix, and air are modeled using Johnson–Cook (JC) plasticity, Deshpande–Fleck (D–F) foam, and linear polynomial equation of state in LS DYNA. Further, the finite element model utilizes a combination of Lagrangian solid elements and meshfree smooth particles hydrodynamics with appropriate contacts to effectively model the interaction of entrapped air within stainless‐steel hollow spheres with surrounding metallic spheres and matrix. The strain rate and the crosshead velocity of 65 s−1 and 2.4765 m s−1 are used for quasistatic compression analysis. Finally, the results obtained from the computational model are compared and validated using previously reported experimental quasistatic compression data. The numerical model corroborates stress–strain response of CMF with 5.6% error for plateau stresses average within 25% and 30% strain.

Influence of hot forging on grain formation in Al0.35CoCrFeNi high-entropy alloy: numerical simulation, microstructure and mechanical properties

One-step (F100) and three-step (F30-60-40) hot forging of Al0.35CoCrFeNi alloy was investigated to achieve a uniform equiaxed grain structure. In the as-cast and forged state, only a single-phase face-centered cubic structure was observed. The formation of twins, recrystallized and partially recrystallized grains in the volume of the samples was observed depending on used forging process. To predict uniform grain-size formation numerical simulation of the hot-forging process was used. The numerical model was calibrated and validated by means of measured compression experimental data of as-cast Al0.35CoCrFeNi alloy before forging. Thermal analysis using finite element analysis was used to simulate cooling of sample during the relocation from the furnace on the lower die. Simulations were run under different thermo-mechanical conditions and the regions for the formation of dynamically recrystallized grains were predicted. Room temperature mechanical properties were evaluated after F100 and F30-60-40 hot-forging process. The F30-60-40 hot forging optimized the grain size, which was evident in the very small dispersion of the room temperature mechanical properties in tension. Elongation after F30-60-40 hot forging increased by 17%. The correlation between temperature, equivalent stress, equivalent plastic strain, microstructure, tensile properties, and strain-hardening behavior is discussed.

Concurrent predictions of tension, compression, and shear characteristics of epoxy using three-network viscoplastic model

Epoxy resin controls the mechanical behavior of fiber-reinforced epoxy composites, which are extensively deployed in the aerospace and automotive industries. For numerical simulations to accurately predict the mechanical deformations of these components under multi-axial loading, matrix characteristics must account for tension, compression, and shear loads at varying strain rates. The existing literature lacks a comprehensive approach to predicting the experimental outcomes across all three loading conditions in a polymer matrix simultaneously using a unified set of viscoelastic or viscoplastic model parameters. In this study, the Three-Network (TN) viscoplastic model was successfully applied to concurrently predict the tension, compression, and shear experimental data of an epoxy resin, published by Littel et al. ( Journal of Aerospace Engg., 2008). The elastic modulus, strain softening-hardening response after yield for tension-compression deformation, and post-yield stress saturation under shear deformation are all accurately predicted by the model at different rates of loading conditions. The predicted and simulated results matched well when the TN viscoplastic model predicted parameters were employed as material property in Abaqus (a commercial finite element software) to simulate the deformation modes. This integrated approach highlights the potential of the TN model in enabling precise predictions for epoxy-based composites, which is crucial for optimizing their performance and reliability in aerospace engineering.

农业车辆作业后不同深度的土壤应力分析

In modern agriculture, with the development and widespread use of agricultural mechanization, mechanical compaction of soils has become a growing problem, resulting in soil degradation in the field. Based on the Boussinesq solution, the soil stress formula for the circular load area is derived, and MATLAB is used to simulate the stress-strain relationship of the soil at different depths. The results show that under the same load conditions, as the soil depth increases, the soil stress gradually decreases, with the most significant stress change occurring at 0.2 m depth. Soil compression experiments conducted using a consolidation instrument revealed that the soil void ratio dropped rapidly under loading of 50-200 kPa, and the decline slowed after 400 kPa. When the soil void ratio decreases to 0.2-0.4, the soil stress changes tend to stabilize. Comparison between the theoretical formula and the compression experimental data indicates that the soil stress gradually decreases as the thickness of the soil layer increases and the pressure load increases, verifying the linear relationship predicted by the theoretical formula.

A three-dimensional viscoelastic–viscoplastic and viscodamage constitutive model for unidirectional fibre-reinforced polymer laminates

A novel 3D viscoelastic–viscoplastic and viscodamage constitutive model is proposed to predict the viscous effects due to dynamic loading conditions of unidirectional carbon fibre-reinforced polymer laminates at the meso-scale level. The present model is developed under continuum damage mechanics and the thermodynamics of irreversible processes framework. The viscoelastic response is modelled using the generalised Maxwell model, while an overstress model is employed to address the viscoplastic strain. The onset of the viscodamage mechanisms is based on experimental expressions, and their propagation is defined as a function of the corresponding fracture toughness. The mechanical response of the present constitutive model under pure longitudinal shear loading conditions at different strain rates is presented. The higher the strain rate is, the stiffer the responses in the viscoelastic and viscoplastic regions are. Additionally, the onset of viscodamage increases with higher strain rates. Off-axis compressive experimental data at two different strain rates are employed to demonstrate the capabilities of the present model with good predictions being obtained.

Enhanced mechanical properties of magnesium alloy reinforced by layered Ti3AlC2 MAX phase fabricated by SPS at a near solidus temperature

Powder metallurgy stands out as a highly promising and versatile method for manufacturing particle-reinforced metal matrix composite (MMCs) as compared to other fabrication processes. This method ensures excellent binding between the matrix and reinforcement, uniform microstructure, and effectively prevents the formation of undesirable phases. In this study, magnesium alloy (AZ91) metal matrix composites (MMCs) reinforced with 0–30 vol% of Ti3AlC2 MAX phase were prepared by Spark Plasma Sintering (SPS) from powders at temperature close to the solidus. Ti3AlC2 is a member of the MAX phases which are known for their layered structure, machinability and being ternary carbides. The latter was synthetized from pure components (Ti, TiC and Al) using insulated SPS technology at high temperature. Sintered composites reached quasi-full density, as measured by Archimedes’ method. Their microstructure has been assessed by SEM and X-ray diffraction (XRD) respectively. Mechanical properties in relationship with the microstructure of all composites were carefully investigated. The experimental compressive tests data were extracted to obtain true strain-true stress curves. Vickers hardness (HV1), ultimate compressive strength (UCS) and conventional yield strength (0.2%YCS) increase with an increasing fraction of Ti3AlC2 in the composites and compare favorably with literature. SEM observations of fracture surfaces after compression tests seem to show that cracks initiate in both Ti3AlC2 clusters and α-Mg/MAX interfaces.

Expanding the Pressure Frontier in Grüneisen Parameter Measurement: Study of Sodium Chloride.

The Grüneisen parameter (γ) is crucial for determining many thermal properties, including the anharmonic effect, thermostatistics, and equation of state of materials. However, the isentropic adiabatic compression conditions required to measure the Grüneisen parameter under high pressure are difficult to achieve. Thus, direct experimental Grüneisen parameter data in a wide range of pressures is sparse. In this work, we developed a new device that can apply pressure (up to tens of GPa) with an extremely short time of about 0.5ms, confidently achieving isentropic adiabatic compression. Then, we applied our new technique to sodium chloride and measured its Grüneisen parameter, which conforms to previous theoretical predictions. According to our obtained sodium chloride Grüneisen parameters, the calculated Hugoniot curve of the NaCl B1 phase appears up to 20GPa and 960K, which compares very well with the shock compression experimental data by Fritz etal. and other calculation works. Our results suggest that this new method can reliably measure the Grüneisen parameter of even more materials, which is significant for researching the equation of state in substances.

A novel viscoelastic fractional damage model of thermosetting polymers for dynamic responses

Thermosets-polymeric materials play a key role in the modern plastics and polymers composites, which are increasingly used in the areas subject to dynamic loading condition. The materials will experience an amount of micro-damage under such circumstances, while the damage softening behaviors cannot be well captured by viscoelastic or elasto-viscoplastic constitutive models. In this paper, a viscoelastic fractional damage model depended on strain rate is formulated to depict the dynamic responses of thermosetting polymers. A dynamic damage evolution law related to strain and strain rate is developed by means of the fractional calculus. The relationship between fractional order and damage evolution for materials is theoretically investigated. It is observed that the fractional order can be able to characterize the intensity of damage evolution, and the variation of order function is in line with the evolution with damage of material properties. The model applicability is verified by the compressive loading experimental data under different strain rates and temperatures of thermosets. The influences of temperatures on the proposed model and the damage evolution are analyzed by the fitting results. Furthermore, a corresponding thermo-viscoelastic model is developed by considering the temperature effect, of which the predictive ability is tested and the comparisons with the existing model are also presented. The results indicate the proposed model can better capture the stress-strain responses over a wider range of strain.

Improvement of Analytical Model for Oblique Cutting—Part I: Identification of Mechanical Characteristics of Machined Material

Analytical cutting models have recently become quite widespread due to the simplicity and rapidity of calculations as well as the stability of the solutions. This paper considers a procedure for determining the mechanical properties of machined material based on parameters for the analytical model of oblique cutting for a certain range of changes in cutting modes and inclination angles of the tool cutting edge. The model is based on the energy method of determining the main cutting process characteristics using the extreme assumptions of continuum mechanics. It is proposed to determine the parameters characterizing the mechanical properties of the processed material using the Johnson–Cook constitutive equation in two stages: preliminary determination of the constitutive equation parameters based on the results of mechanical compression specimen tests and experimental data of the oblique cutting process, and specifying the generalized values of the constitutive equation parameters using the inverse method through the finite element cutting model. The adequacy of the applied analytical cutting model is confirmed by comparing the kinetic characteristic values calculated using the analytical model of oblique cutting with the application of the specified parameters of the constitutive equation and the measured values of the kinetic characteristics. The deviation between the calculated and measured values of the cutting force components when changing the cutting depth (undeformed chip thickness) does not exceed 15%. The difference between the calculated and measured values of the cutting force components when the cutting speed is changed is about 20%.

Effect of graphene oxide on cement mortar under quasi-static and dynamic loading

Cement composites are the most widely used construction material in the world; however, research on their resistance to high strain loads is lacking. This study investigated the effect of graphene oxide (GO) on the static and dynamic mechanical properties and microstructure of cement mortar. Dynamic tests were performed using a split Hopkinson pressure bar apparatus at strain rates up to approximately 290 s−1. The mechanical behaviors of mortar specimens infused with 0.005 and 0.01 wt% GO (weight% of GO to cement) were compared against control specimens made with ordinary Portland cement. Enhancement in the strength of cement composites was evident in both compression and split-tension when GO was added in specific doses, particularly at higher strain rates. Correlation between the dynamic increase factor and the applied strain rate is found based on the compressive and split-tensile experimental data of tested mortar specimens. The findings of this study highlight the great potential of GO for improving the performance of cement composites under high strain rate loading.

Radial compression pressure estimation of carcass layers in unbonded flexible pipes based on neural networks

Radial pressure resistance is a key factor in the design of unbonded flexible pipe carcass layers because it directly affects the safe installation and use of marine flexible pipes. It is challenging to evaluate the performance of radial compression because the carcass layer, which is a large-angle helical winding structure in innermost flexible pipes with a special-shaped cross section, experiences numerous contact frictions under radial pressure. In this study, a radial pressure estimation approach based on neural networks is proposed to address the aforementioned issues. This study explores the nonlinear relationship between the limited structural responses (circumferential strain) and the overall load (radial compression pressure) from the radial compression experimental data and estimates the radial compression pressure of carcass layers. The input variables are the structural strains, and the output variable is the radial pressure. Furthermore, some examples are used to test the generalization of the method, including robustness and understanding, considering the geometric characteristics of the carcass layer. The results demonstrate that the method can accurately predict the radial pressure applied to the carcass layer and provide a theoretical framework for the design of unbonded flexible pipes in deep-sea environments.

Ti-6Al-4V to over 1.2 TPa: Shock Hugoniot experiments, ab initio calculations, and a broad-range multiphase equation of state

Titanium alloys are used in a large array of applications. In this work we focus our attention on the most used alloy, Ti-6Al-4V (Ti64), which has excellent mechanical and biocompatibility properties with applications in aerospace, defense, biomedical, and other fields. Here we present high-fidelity experimental shock compression data measured on Sandia's Z machine. We extend the principal shock Hugoniot for Ti64 to more than threefold compression, up to over 1.2 TPa. We use the data to validate our ab initio molecular dynamics simulations and to develop a highly reliable, multiphase equation of state (EOS) for Ti64, spanning a broad range of temperature and pressures. The first-principles simulations show very good agreement with Z data and with previous three-stage gas gun data from Sandia's STAR facility. The resulting principal Hugoniot and the broad-range EOS and phase diagram up to 10 TPa and ${10}^{5}$ K are suitable for use in shock experiments and in hydrodynamic simulations. The high-precision experimental results and high-fidelity simulations demonstrate that the Hugoniot of the Ti64 alloy is stiffer than that of pure Ti and reveal that Ti64 melts on the Hugoniot at a significantly lower pressure and temperature than previously modeled.

Shock compression of poly(methyl methacrylate) PMMA in the 1000 GPa regime: Z machine experiments

Hydrocarbon polymers are used in a wide variety of practical applications. In the field of dynamic compression at extreme pressures, these polymers are used at several high energy density (HED) experimental facilities. One of the most common polymers is poly(methyl methacrylate) or PMMA, also called Plexiglass® or Lucite®. Here, we present high-fidelity, hundreds of GPa range experimental shock compression data measured on Sandia’s Z machine. We extend the principal shock Hugoniot for PMMA to more than threefold compression up to 650 GPa and re-shock Hugoniot states up to 1020 GPa in an off-Hugoniot regime, where experimental data are even sparser. These data can be used to put additional constraints on tabular equation of state (EOS) models. The present results provide clear evidence for the need to re-examine the existing tabular EOS models for PMMA above ∼120 GPa as well as perhaps revisit EOSs of similar hydrocarbon polymers commonly used in HED experiments investigating dynamic compression, hydrodynamics, or inertial confinement fusion.

Ensemble Machine-Learning-Based Prediction Models for the Compressive Strength of Recycled Powder Mortar.

Recycled powder (RP) serves as a potential and prospective substitute for cementitious materials in concrete. The compressive strength of RP mortar is a pivotal factor affecting the mechanical properties of RP concrete. The application of machine learning (ML) approaches in the engineering problems, particularly for predicting the mechanical properties of construction materials, leads to high prediction accuracy and low experimental costs. In this study, 204 groups of RP mortar compression experimental data are collected from the literature to establish a dataset for ML, including 163 groups in the training set and 41 groups in the test set. Four ensemble ML models, namely eXtreme Gradient-Boosting (XGBoost), Random Forest (RF), Light Gradient-Boosting Machine (LightGBM) and Adaptive Boosting (AdaBoost), were selected to predict the compressive strength of RP mortar. The comparative results demonstrate that XGBoost has the highest prediction accuracy when the a10-index, MAE, RMSE and R2 of the training set are 0.926, 1.596, 2.155 and 0.950 and the a10-index, MAE, RMSE and R2 of the test set are 0.659, 3.182, 4.285 and 0.842, respectively. SHapley Additive exPlanation (SHAP) is adopted to interpret the prediction process of XGBoost and explain the influence of influencing factors on the compressive strength of RP mortar. According to the importance of influencing factors, the order is the mass replacement rate of RP, the size of RP, the kind of RP and the water binder ratio of RP. The compressive strength of RP mortar decreases with the increase in the RP mass replacement rate. The compressive strength of RBP mortar is slightly higher than that of RCP mortar. Machine learning technologies will benefit the construction industry by facilitating the rapid and cost-effective evaluation of RP material properties.

Compression Relaxation of Multi-Structure Polymer Composites in Penetrating Liquid Medium.

Multi-structural polymer composites are widely used in the mechanical engineering, automotive, aviation and oil refining industries, as well as in the printing industry as a shock-absorbing deckle on the offset cylinders of printing machines. During offset printing, composites come into contact with inks and washing solutions, the components of which penetrate the material and cause the polymers to swell. This process degrades the print quality, and for this reason the study of its features is relevant. The prerequisites for this work are the study of the fundamental laws of diffusion and sorption of liquids by polymers with different micro- and macro-structures in different physical states and in different forms (e.g., films, sheets, fibers and fabrics). The combination of polymer materials in the composition of multi-structural fabric blankets makes it possible to obtain materials with unique mechanical properties and high resistance to liquid penetrating media and to use them in high-tech processes of multi-color printing with high resolution and color rendering. This article reports for the first time the kinetics and thermodynamics results obtained from the swelling of multi-structural polymeric blankets in solvents used in printing, and the effect of sorption of different polar liquids on the viscoelastic strain under compression during the operation of the damping systems of printing machines. Using mathematical models of activated liquid diffusion in polymers and deformation of a viscoelastic body, the swelling rate constants, solvent diffusion coefficients (the kinetic characteristics of the swelling process) and Flory−Huggins parameters (the thermodynamic characteristics of the interaction of the solvent with the composite) for composite−solvent systems with several chemical composition variants were determined. The elastic modulus and the viscosity coefficient of the composite under liquid saturation were calculated based on the experimental cyclic compression data. The range of change in the compression and restoration times of the polymeric blankets (0.09 s ÷ 0.78 s) was determined. It was shown that the composite swelled to a limited extent in all the studied liquids. All solvents used were thermodynamically poor (χ > 0.5). It has been established that rubber−fabric blankets coated with nitrile rubber are the least resistant to the action of dichloroethane, and that blankets with layers of polyolefins are not resistant to ethyl acetate. Water significantly affects the physicochemical properties of rubber−fabric blankets with a large proportion of cotton fabric layers. The data obtained can serve as a basis for optimizing the compositions of inks and cleaning solutions, as well as a theoretical basis for the thermodynamics of composite−solvent systems.

Viscoelastic-viscoplastic damage analysis of transversely isotropic soft soils

Soft soils show noticeable creep, damage and transversely isotropic properties. An incremental three-dimensional Nishihara model is proposed to present the stress-strain relationship of soft soils in this paper. The Drucker-Prager yield criterion of the transversely isotropic media, the transversely isotropic flexibility matrix, and the damage law to Nishihara's constitutive model are applied to construct the transversely isotropic viscoelastic-viscoplastic damage constitutive equation of the soil. Afterwards, the constitutive model is implemented by applying a stress return mapping algorithm. We verified the proposed model by comparing the results calculated by ABAQUS with triaxial compression experimental data from Hong Kong marine deposits (HKMD) and Shanghai soft clay. Finally, based on the proposed model, we present several numerical examples to investigate the influences of damage parameters on the time-dependent behaviors of saturated soft clay.

Hyperelastic Properties of Bamboo Cellulosic Fibre-Reinforced Silicone Rubber Biocomposites via Compression Test.

Materials that exhibit highly nonlinear behaviour are intricate to study. This is due to their physical properties, as they possess a very large deformation. Silicone rubber is among the materials that can be classified as possessing such characteristics, despite their being soft and frequently applied in medical applications. Due to their low mechanical properties, however, it is believed that a filler addition could enhance them. This study, therefore, aims to investigate the effect of the addition of bamboo cellulosic filler to silicone rubber in terms of its compressive properties in order to quantify its material constants using the hyperelastic theory, specifically the Neo-Hookean and Mooney–Rivlin models. The specimens’ compressive properties were also compared between specimens immersed in seawater and those not immersed in seawater. The findings showed that the compressive properties, stiffness, and compressive strength of the bamboo cellulosic fibre reinforced the silicone rubber biocomposites, improved with higher bamboo filler addition. Specimens immersed in seawater showed that they can withstand a compressive load of up to 83.16 kPa in comparison to specimens not immersed in seawater (up to 79.8 kPa). Using the hyperelastic constitutive models, the Mooney–Rivlin model displayed the most accurate performance curve fit with the experimental compression data with an R2 of up to 0.9999. The material constant values also revealed that the specimens immersed in seawater improved in stiffness property, as the C1 material constant values are higher than for the specimens not immersed in seawater. From these findings, this study has shown that bamboo cellulosic filler added into silicone rubber enhances the material’s compressive properties and that the rubber further improves with immersion in seawater. Thus, these findings contribute significantly towards knowledge of bamboo cellulosic fibre–reinforced silicone rubber biocomposite materials.

Quantification of Non-conventional Brick’s Characteristic Compressive Strength

Abstract Now-a-days researches are concentrating on the utilization of waste materials in construction industry. Fly ash is one of the waste originated from industrial, is the main concern in the present study for brick manufacturing. As fly-ash is a by-product, its properties may vary from source to source resulting variation in strength of the brick. To confirming this, the main focus of the present study was to fabricate a hydraulically operated semi-automatic brick pressing machine followed by preparation of fly ash brick using that and study on the variation of brick strength. Later on, a statistical analysis is conducted based on the experimental compressive strength data for the fly ash bricks. The normal distribution curves are plotted followed by the estimating the constraints of normal distribution, which is the most common adopted distribution function in concrete. From the analysis, the characteristic compressive strength at 95% probability level is obtained as 3.46 and 5.42MPa respectively for the bricks (M1 and M2 type).

Modified Deshpande–Fleck Model considering a Variable Plasticity Poisson’s Ratio and a Variable Ellipticity

It is controversial whether the plastic Poisson’s ratio and ellipticity are invariable in the Deshpande–Fleck model, which describes the constitutive behavior of foam materials. In this paper, the Deshpande–Fleck model is modified by a variable plasticity Poisson’s ratio and a variable ellipticity based on a nonassociated flow rule. The plasticity Poisson’s ratio is measured by in situ digital image correlation (DIC) technology during the uniaxial compression experiment of aluminum foam. The ellipticity is then determined through the experimental data of uniaxial compression and hydrostatic compression. Both the plastic Poisson’s ratio and the ellipticity vary with the strain. The Hanssen model fitted with uniaxial compression experimental data is used to provide the hardening law for the modified Deshpande–Fleck model. The modified Deshpande–Fleck model is realized by the subroutine VUMAT in ABAQUS/Explicit. There is good agreement between the experimental results and the prediction results of the modified Deshpande–Fleck model under multiaxial compression conditions. Furthermore, the influence mechanism of the plastic Poisson’s ratio and ellipticity on the modified Deshpande–Fleck model are investigated. The results prove that it is necessary to consider both the variable plastic Poisson’s ratio and the variable ellipticity in order to improve the prediction accuracy of the modified Deshpande–Fleck model.

Impact of the Loading Conditions and the Building Directions on the Mechanical Behavior of Biomedical β-Titanium Alloy Produced In Situ by Laser-Based Powder Bed Fusion.

In order to simulate micromachining of Ti-Nb medical devices produced in situ by selective laser melting, it is necessary to use constitutive models that allow one to reproduce accurately the material behavior under extreme loading conditions. The identification of these models is often performed using experimental tension or compression data. In this work, compression tests are conducted to investigate the impact of the loading conditions and the laser-based powder bed fusion (LB-PBF) building directions on the mechanical behavior of -Ti42Nb alloy. Compression tests are performed under two strain rates (1 s and 10 s) and four temperatures (298 K, 673 K, 873 K and 1073 K). Two LB-PBF building directions are used for manufacturing the compression specimens. Therefore, different metallographic analyses (i.e., optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), electron backscatter diffraction (EBSD) and X-ray diffraction) have been carried out on the deformed specimens to gain insight into the impact of the loading conditions on microstucture alterations. According to the results, whatever the loading conditions are, specimens manufactured with a building direction of 45 exhibit higher flow stress than those produced with a building direction of 90, highlighting the anisotropy of the as-LB-PBFed alloy. Additionally, the deformed alloy exhibits at room temperature a yielding strength of 1180 ± 40 MPa and a micro-hardness of 310 ± 7 HV. Experimental observations demonstrated two strain localization modes: a highly deformed region corresponding to the localization of the plastic deformation in the central region of specimens and perpendicular to the compression direction and an adiabatic shear band oriented with an angle of ±45 with respect to same direction.