Material Model Research Articles

Compressing of experimental and simulated results of electron beam interaction with FFF-printed samples

One of the important parameters characterizing the interaction of electron beams with matter is the depth dose distribution. To develop a new approach for shaping electron beams using specially created materials suitable for the manufacture of complex 3D-printed devices, it is necessary to analyze the features of ionizing radiation propagation. In this work, numerical simulations and experimental studies of the interaction between electron beams and plastic materials weighted with metallic impurities of different concentrations, suitable for fabricating samples using the rapid prototyping method, were carried out. Sets of plates made from the investigated plastics were created using the fused filament fabrication (FFF) technique. Since the FFF sample fabrication process involves forming objects from a thermoplastic mass through layer-by-layer alignment, a distinctive feature of the printed samples is their lower actual density compared to the density of the material (filament) from which they are made. Taking this fact into account, the actual density of the polymer plates was calculated. Based on this data, numerical models of the plastic materials weighted with metallic impurities were developed, and virtual models of the experimental setup were created to calculate the electron beam depth dose distributions in the materials. In the next step of the investigation, experimental studies were performed using electron beams with energies of 6 and 10 MeV. Pre-calibrated GafChromic EBT3 dosimetry films were used as detectors to obtain the experimental data on the electron beam depth dose distributions in the materials under consideration. It was observed that with an increasing concentration of metal impurities in the plastic base, the depth dose distribution moves into smaller thicknesses. It was observed that the simulation and experimental results are in good agreement.

Measuring the viscoelastic relaxation function of cells with a time-dependent interpretation of the Hertz-Sneddon indentation model

The Hertz-Sneddon elastic indentation model is widely adopted in the biomechanical investigation of living cells and other soft materials using atomic force microscopy despite the explicit viscoelastic nature of these materials. In this work, we demonstrate that an exact analytical viscoelastic force model for power-law materials, can be interpreted as a time-dependent Hertz-Sneddon-like model. Characterizing fibroblasts (L929) and osteoblasts (OFCOLII) demonstrates the model's accuracy. Our results show that the difference between Young's modulus EY obtained by fitting force curves with the Hertz-Sneddon model and the effective Young's modulus derived from the viscoelastic force model is less than 3%, even when cells are probed at large forces where nonlinear deformation effects become significant. We also propose a measurement protocol that involves probing samples at different indentation speeds and forces, enabling the construction of the average viscoelastic relaxation function of samples by conveniently fitting the force curves with the Hertz-Sneddon model.

A novel non-linear peridynamic model for quasi-brittle materials under cyclic loading

In the present paper, a novel non-linear peridynamic (PD) model is proposed to numerically simulate the fatigue behaviour of quasi-brittle materials. The model implements a non-linear degradation law for the bonds, function of the number of loading cycles. More precisely, a calibration function and a calibration parameter are included in such a law. The novel PD model is applied to simulate cyclic three-point bending experimental tests performed on concrete notched beams (available in the literature). The results are presented in terms of fatigue lifetime, Paris law parameters and crack path.

Rapid Simulation of Electro-Chemo-Mechanical Deformation of Li-ion Batteries Based On Porous Electrode Theory

Lithium-ion batteries change their geometric dimensions during cycling as a macroscopic result of a series of microscale mechanisms, including but not limited to diffusion-induced expansion/shrinkage, gas evolution, growth of solid-electrolyte interphase, and particle cracking. Predicting the nonlinear dimensional changes with mathematical models is critical to the lifetime prediction, health management, and non-destructive assessment of batteries. In this study, we present an approach to implement an elastoplasticity model for powder materials into the porous electrode theory (PET). By decomposing the overall deformation into elastic, plastic, and diffusion-induced portions and using the powder plasticity model to describe the plastic portion, the model can capture the reversible thickness change caused by Li-ion (de-)intercalation as well as the irreversible thickness change due to the rearrangement and consolidation of particles. For real-world applications of the model to predict battery health and safety, the key lies in solving the mathematical equations rapidly. Here, we implemented the coupled model into the open-source software PETLION for millisecond-scale simulation. The computational model is parameterized using values gathered from literature, tested under varying conditions, briefly compared to real-world observations, and qualitatively analyzed to find parameter-output relations.

Testing the auto-regressive integrated moving average approach vs the support vector machines-based model for materials forecasting to reduce inventory

Testing the auto-regressive integrated moving average approach vs the support vector machines-based model for materials forecasting to reduce inventory

Estimation of inelastic heat fraction of Ti-6Al-4V alloy using inverse analysis

This work aims to determine the inelastic heat fraction of Ti-6Al-4V alloy by coupling the experimental and Finite Element Method (FEM) results by an inverse analysis approach. The inelastic heat fraction is a crucial factor in revealing information on the deformation mechanism and forms the basis of the microstructural evolution of a material. Hot compression tests on Ti-6Al-4V alloy at various temperatures and strain rates were carried out using the Gleeble thermo-mechanical simulator. An axisymmetric thermo-mechanical modelling was carried out using the FEM package i.e., ABAQUS. The work reveals that the inelastic heat fraction increases with an increase in strain rate and decreases with an increase in deformation temperature. The proposed method is capable of predicting the inelastic heat fraction of a material for a wide range of temperatures and strain rates. The FEM modelling and experimental results exhibit good agreement. The findings of this study can aid in more precise material modelling and contribute to the formation of a thermo-mechanical material database.

Investigation of the optimal cutting depth in small incision lenticule extraction based on a collagen fibril crimping constitutive model of the cornea

To investigate the optimal cutting depth (Cap) in small incision lenticule extraction from the perspective of corneal biomechanics, a three-dimensional finite element model of the cornea was established using a stromal sub-regional material model to simulate small incision lenticule extraction. The displacement difference PΔ at the central point of the posterior corneal surface before and after lenticule extraction, as well as the von Mises stress at four points of different thicknesses in the center of the cornea, were analyzed using the finite element model considering the hyperelastic property and the difference in stiffness between the anterior and posterior of the cornea. The numerical curves of PΔ-Cap and von Mises Stress-Cap relations at different diopters show that the displacement difference PΔ has a smallest value at the same diopter. In this case, the von Mises stress at four points with different thicknesses in the center of the cornea was also minimal. Which means that the optimal cutting depth exsisting in the cornea. Moreover, PΔ-Cap curves for different depth of stromal stiffness boundaries show that the optimal cap thickness would change with the depth of the stromal stiffness boundary. These results are of guiding significance for accurately formulating small incision lenticule extraction surgery plans and contribute to the advancement of research on the biomechanical properties of the cornea.

Strain rate and temperature rate behavior of ultra-high-strength 1770 steel: Base for transverse impact analysis

The investigation was motivated by the widespread use of ultra-high-strength steels in cable-stayed bridges and armor steel plates. These structures are exposed to elevated risks from extreme loads, including vehicle impacts and blast loadings. The study aimed to investigate the mechanical properties of 1770 steel for applications in extreme conditions. The strain rates and temperatures ranged from 0.00095 s−1 to 1303 s−1 and 20 °C–900 °C, respectively. Tensile tests were conducted at various strain rates using a Split Hopkinson Tension Bar for dynamic testing and a universal testing machine for quasi-static testing at room temperature (20 °C). Quasi-static tension at elevated temperatures was carried out using an electromechanical testing machine coupled with a heating device. A uniform temperature distribution inside the specimens was ensured by a 30-min holding time. The results of the tensile test indicate that the 1770 steel displays notable thermal softening effects and strain rate hardening that differ from mild steel. The standard Johnson-Cook (J-C) model was found to be inadequate in accurately predicting the strain rate effects of this specimen. To address this issue, the strain rate parameter C in the standard model was adjusted to create the modified J-C model, which demonstrated good agreement with the experimental results. To further demonstrate the modified model and the identified parameters, drop hammer impact tests and corresponding numerical simulations were conducted. The impact test and numerical simulation results showed good agreement in terms of deformation and contact force. The mechanical properties and the constitutive models can serve as a design reference for the ultra-high-strength 1770 steel in extreme envirnments, as well as a theoretical basis for fitting material models of similar ultra-high-strength steels.

Analysis of bullet impact test on aluminum alloy plates at varying thickness and velocities

Analysis of bullet impact test on aluminum alloy plates at varying thickness and velocities

Elasto-plastic simulation of hot shape rolling of steel by a meshless method

This paper describes the development of meshless simulation of thermomechanics of steel in a continuous hot rolling process using a novel meshless solution procedure. During the process, steel billets at high temperatures are transferred through multiple roll passes, each with a specific groove shape and roll gap. The major outcome of this simulation system is to design the rolling schedule and confirm whether the final shape is inside the acceptable range. For this purpose, a perpendicular 2D slice model approach is used to obtain fast and reasonably accurate simulation results. A return mapping algorithm solves the elasto-plastic material model with linear hardening to obtain displacements, strains and stresses. They are calculated by the local radial basis function collocation method (LRBFCM), which uses the local interpolation of the strong form of partial differential equations. The predefined slice positions are entered into the rolling system, and for each position, the slice contact line and amount of reduction are predicted and used as boundary conditions. Thermal and mechanical models are run sequentially, which is repeated until the final slice position reaches the exit from the last roll. The simulation system was validated with multiple rolling schedules provided by the industrial partner and was successfully used in the steel production plant afterwards. The meshless LRBFCM successfully solves a complex elasto-plastic large deformation problem of hot rolling for the first time.

On elastoplastic behavior of porous enamel–An indentation and numerical study

The micro/nano pores in natural mineralized tissues can, to a certain extent, affect their responses to mechanical loading but are generally ignored in existing indentation analysis. In this study, we first examined the void volume fraction of sound and caries lesion enamels through micro-computed tomography (micro-CT). A Berkovich indentation study was then carried out to characterize the effect of porous microstructure on the mechanical behavior of the human enamels. The indentation tests were also modeled using the nonlinear finite element analysis technique to simulate indentation load-displacement curves, which showed reasonable agreement with the experimental measurements. From the simulation results, the extent of densification in the plastic zone was identified and the corresponding stress and contact pressure evolutions were quantified. Further, a conventional elastic-perfectly plastic material model without considering micropores was also developed to investigate the compaction effect of the porous structure. The simulation results reveal that conventional elastic perfect-plastic constitutive models become less reliable to model the mechanical behavior of carious lesion enamel with increasing loss of mineral content as it underestimates the yield stress and plastic energy dissipation. This study divulges the importance of compaction of porous enamel structure beneath the indented area. Note that understanding the effect of porous microstructures on plastic behavior is vital as the involved inelastic deformation mechanism associated with irreversible processes, such as wear and localized microcracking, has a significant bearing on wear and fatigue behavior of enamel. Statement of significanceBased on micro-CT and nano-indentation characterization, a numerical model was developed aiming to precisely describe the deformation behavior of naturally porous enamel. Inelastic properties and energy dissipation characteristics of porous enamel were investigated in detail. This work demonstrated that the existence of micro-pores in White Spot Lesions (WSLs) contributes to mechanical stability, which can mitigate the reduction in Young's modulus and fracture toughness resulting from loss of mineral components. The knowledge gained from this study can be used to explain the mechanisms related to irreversible processes, such as contact induced cracking and wear, and strengthen understanding of the mechanical behavior of porous mineralized tissues.

Numerical study of the seepage behavior of droplets in porous materials

This article analyzes the spread and infiltration dynamic process of liquid droplets on the surface of porous materials and establishes a mathematical model of dynamic changes in droplets. To accurately describe the dynamic effects of droplet flow, a mathematical model of droplet dynamics was developed by applying the level-set method, and the seepage process of the droplets was also analyzed numerically. The effects of a series of control parameters on the droplet percolation process are analyzed, and the pore degree of porous materials performed a numerical study of the droplet deformation process. We observe the spread and infiltration process of liquid droplets in porous materials models. It was found that there is a competitive relationship between diffusion and penetration of droplets. The depth of penetration of droplets decreases with increasing viscosity and increases with increasing porosity. The results of the study help to understand the seepage behavior of the droplet on the surface of the porous material.

Simulating equal channel angular pressing of commercially pure aluminium using Johnson–Cook model

Optimizing the Equal Channel Angular Pressing (ECAP) process for a new material can be a complex endeavour, given the multiple variables such as Coefficient of Friction (COF), channel angle, temperature, etc. To address the need for a material model that can account for temperature-dependent plastic flow, the present study applies the Johnson-Cook plasticity model for simulating ECAP. The present study reports the effects of varying the channel angle (90°, 120°, 150°) and COF (ranging from 0 to 0.15) at room temperature. The results show that the channel angle plays a significant role in influencing the behaviour of the aluminium, with stress and strain exhibiting an inverse relationship with the channel angle. Additionally, the aluminium material experiences a maximum stress distribution and higher flow stress within the COF range of 0 to 0.15 for a channel angle of 90°, as compared to 120° and 150°. This behaviour can be attributed to the restriction of movement at higher COF values. Notably, a maximum shear stress of 56 MPa was observed when the channel angle was set to 90° with a COF of 0.15. Furthermore, across all simulations involving channel angles of 90°, 120°, and 150°, an increase in COF lead to a decrease in curvature. These simulated results are consistent with existing literature. Thus, the Johnson-Cook plasticity model, with appropriate modifications, serves as a viable approach for studying the ECAP process.

Using tensile and compressive stress superposition during incremental forming to manipulate martensitic transformation in SS304

Single point incremental forming (SPIF) is a flexible manufacturing process that has applications in industries ranging from biomedical to automotive. In addition to rapid prototyping, which requires easy adaptations in geometry or material for design changes, control of the final part properties is desired. One strategy that can be implemented is stress superposition, which is the application of additional stresses during an existing manufacturing process. Tensile and compressive stresses applied during SPIF showed significant effects on the resulting microstructure in stainless steel 304 truncated square pyramids. Specifically, the amount of martensitic transformation was increased through stress superposed incremental forming. Finite element analyses with advanced material modeling supported that the stress triaxiality had a larger effect than the Lode angle parameter on the phase transformation that occurred during deformation. By controlling the amount of tensile and compressive stresses superposed during incremental forming, the microstructure of the final component can be manipulated based on the intended application and desired final part properties.

Advances in Computational Methods for Modeling Photocatalytic Reactions: A Review of Recent Developments.

Photocatalysis is a fascinating process in which a photocatalyst plays a pivotal role in driving a chemical reaction when exposed to light. Its capacity to harness light energy triggers a cascade of reactions that lead to the formation of intermediate compounds, culminating in the desired final product(s). The essence of this process is the interaction between the photocatalyst's excited state and its specific interactions with reactants, resulting in the creation of intermediates. The process's appeal is further enhanced by its cyclic nature-the photocatalyst is rejuvenated after each cycle, ensuring ongoing and sustainable catalytic action. Nevertheless, comprehending the photocatalytic process through the modeling of photoactive materials and molecular devices demands advanced computational techniques founded on effective quantum chemistry methods, multiscale modeling, and machine learning. This review analyzes contemporary theoretical methods, spanning a range of lengths and accuracy scales, and assesses the strengths and limitations of these methods. It also explores the future challenges in modeling complex nano-photocatalysts, underscoring the necessity of integrating various methods hierarchically to optimize resource distribution across different scales. Additionally, the discussion includes the role of excited state chemistry, a crucial element in understanding photocatalysis.

Ductile Fracture of Titanium Alloys in the Dynamic Punch Test

Estimates of physical and mechanical characteristics of materials at high strain rates play a key role in enhancing the accuracy of prediction of the stress–strain state of structures operating in extreme conditions. This article presents the results of a combined experimental–numerical study on the mechanical response of a thin-sheet rolled Ti-5Al-2.5Sn alloy to dynamic penetration. A specimen of a titanium alloy plate underwent punching with a hemispherical indenter at loading rates of 10, 5, 1, and 0.5 m/s. The evolution of the rear surface of specimens and crack configuration during deformation were observed by means of high-speed photography. Numerical simulations were performed to evaluate stress distribution in a titanium plate under specified loading conditions. To describe the constitutive behavior and fracture of the Ti-5Al-2.5Sn alloy at moderate strain rates, a physical-based viscoplastic material model and damage nucleation and growth relations were adopted in the computational model. The results of simulations confirm a biaxial stress state in the center of specimens prior to fracture initiation. The crack shapes and plate deflections obtained in the calculations are similar to those observed in experiments during dynamic punching.

Experimental and numerical investigations on the acoustoelastic effect in hyperelastic waveguides

Guided ultrasonic wave based structural health monitoring has been of interest over decades. However, the influence of prestress states on the propagation of Lamb waves in thin-walled structures is not fully covered yet. So far experimental work presented in the literature only focuses on a few individual frequencies, which does not allow a comprehensive verification of the numerous numerical investigations. Furthermore, most work is based on the strain-energy density function by Murnaghan. To validate the common modeling approach and to investigate the suitability of other nonlinear strain-energy density functions, an extensive experimental and numerical investigation covering a large frequency range is presented here. The numerical simulation comprises the use of the Neo-Hooke as well as the Murnaghan material model. It is found that these two material models show qualitatively similar results. Furthermore, the comparison with the experimental results reveals that the Neo-Hooke material model reproduces the effect of prestress on the difference in the Lamb wave phase velocity very well in most cases. For the [Formula: see text] wave mode at higher frequencies, however, the sign of this difference is only correctly predicted by the Murnaghan model. In contrast to this, the Murnaghan material model fails to predict the sign change for the [Formula: see text] wave mode.

Dynamic mechanical behaviors of load-bearing battery structure upon low-velocity impact loading in electric vehicles

As the electrification trend of vehicles continues, new energy vehicles such as electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) are being equipped with new functional energy storage devices demanding a trade-off between electrical and mechanical property. Accordingly, composite-battery integrated structures which simultaneously carry mechanical resistance and energy-storage capacity, are being explored to offer great potential for the next generation of EVs or PHEVs. Herein, the dynamic responses and failure mechanisms of the integrated structure under the commonly occurring low-velocity impact events are studied both experimentally and numerically. A macro-scale finite element (FE) model was developed by implementing constitutive models of component materials, including lithium‐ion polymer (LiPo) battery cells, polymer foams, and carbon fiber-reinforced polymers (CFRP). The numerical method demonstrates good feasibility and accurately predicts impact behaviors, with the maximum error of the peak impact load not exceeding 8 %. The integrated structures are proven to reduce mechanical damage while maintaining mechanical and electrochemical performance within a range of impacts. The electrical and mechanical behaviors and their correlations were revealed. Sensitivity of the mechanical behaviors and electrical failure to battery arrangement were discussed as well as the structure design on energy absorption capacity. These results hold significant potential for the safety and lightweight design of energy storage composite structures incorporating lithium-ion batteries.

Design and Experimental Results Obtained with an Astragalus Digger Prototype

Traditional methods for harvesting medicinal materials with long roots, like Astragalus membranaceus, require extensive soil excavation, leading to problems like inefficient soil separation, low stemming rates, and blockages in conveyor chains. To address these challenges, this study introduces a prototype machine capable of digging, separating soil, crushing soil, and collecting the medicinal materials in one continuous process. The paper focuses on the machine’s design and working principle, with theoretical analysis and calculations for key components like the digging shovel, multi-stage conveyor, and soil-crushing device. Specific structural parameters were determined, and the screening efficiency of the roller screen was analyzed using EDEM 2020 software, comparing scenarios with and without rollers. A motion model for the medicinal materials during conveyance was established, allowing for the determination of optimal linear velocity and mounting angle for the conveyor. Additionally, a motion model for the second-stage conveyor chain and rear soil-crushing device was used to optimize their placement, ensuring efficient soil crushing without affecting the thrown Astragalus. Compared to traditional Chinese medicine diggers, this machine boasts superior resistance reduction and soil-crushing capabilities. Compared with traditional harvesters, the drag-reducing and soil-crushing device of this machine is more efficient, reducing the damage to Astragalus during the harvesting process, reducing the labor intensity of farmers, and improving the quality and efficiency of Astragalus harvesting. Field experiments have shown that when the operating speed of the prototype is 1.0 m/s and the roller-screen speed is 130~150 rpm, the operating performance is optimal, and comparative experiments can be conducted under the optimal parameters. From the experimental results, it can be seen that the improved equipment has increased the bright-stem rate by about 4%, the digging and loosening rate by 97.42%, and the damage rate by 2.44%. The equipment design meets the overall design requirements, and all experimental indicators meet national and industry standards. This provides a reference for the optimization and improvement of the soil-crushing device and the structure of the Astragalus membranaceus harvester.

Thermomechanical constitutive behaviour of 3D printed biomimetic polymer material under high strain rates

With the continuous technical breakthroughs of flexible electronics, materials with outstanding application potential are constantly being designed and optimized. Biomimetic polymer materials are particularly appealing due to their versatility and ease of fabrication, but their mechanical reliability, particularly their thermomechanical constitutive behaviour under extreme working loads, remains unclear. In this paper, the impact responses of a 3D printed biomimetic polymer material named “Tangoblack” are investigated under thermomechanical, focusing on the effect of strain rate. By adjusting the pressure of the gas gun in the split Hopkinson pressure bar, different strain rates are achieved, while the high temperature of the tested sample can be controlled using a heating furnace integrated into the experiment system. Materials for pulse shapers are carefully selected to ensure longer durations at nearly constant strain rates. The constitutive behaviour of the biomimetic polymer material is further investigated under a wide strain rate range from 958 s−1 to 2158 s−1 and three different temperatures (20 °C, 70 °C and 120 °C). The results demonstrate a significant dependence of the polymer material on both strain rate and temperature. A rapid increase in forming strain rate enhances the strain hardening process, while simultaneously revealing a substantial temperature softening effect. Then, an improved nonlinear thermoviscoelastic ZWT constitutive model is proposed utilizing the Vogel-Fulcher-Tammann equation and implemented as a user-defined material model in ABAQUS/Explicit. The proposed constitutive model is demonstrated to be distinctly advantageous, which suggests a novel pathway for describing the mechanical reliability of biomimetic polymer materials under extreme working conditions.