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[Display omitted] Plant leaves have to deal with various environmental influences. While the mechanical properties of petiole and lamina are generally well studied, only few studies focused on the properties of the transition zone joining petiole and lamina. Especially in peltate leaves, characterised by the attachment of the petiole to the abaxial side of the lamina, the 3D leaf architecture imposes specific mechanical stresses on the petiole and petiole-lamina transition zone. Several principles of internal anatomical organisation have been identified. Since the mechanical characterisation of the transition zone by direct measurements is difficult, we explored the mechanical properties and load-bearing mechanisms by finite-element simulations. We simulate the petiole-lamina transition zone with five different fibre models that were abstracted from CT data. For comparison, three different load cases were defined and tested in the simulation. In the proposed model, the fibres are represented in a smeared sense, where we considered transverse isotropic behavior in elements containing fibres. In a pre-processing step, we determined the fibre content, direction, and dispersion and fed them into our model. The simulations show that initially, matrix and fibres carry the load together. After relaxation of the stresses in the matrix, the fibres carry most of the load. Load dissipation and stiffness differ according to fibre arrangement and depend, among other things, on orientation and cross-linking of the fibres and fibre amount. Even though the presented method is a simplified approach, it is able to show the different load-bearing capacities of the presented fibre arrangements. In plant leaves, the petiole-lamina transition zone is an important structural element facilitating water and nutrient transport, as well as load dissipation from the lamina into the petiole. Especially in peltate leaves, the 3D leaf architecture imposes specific mechanical stresses on the petiole-lamina transition zone. This study aims at investigating its mechanical behavior using finite-element simulations. The proposed continuum mechanical anisotropic viscoelastic material model is able to simulate the transition zone under different loads while also considering different fibre arrangements. The simulations highlight the load-bearing mechanisms of different fibre organisations, show the mechanical significance of the petiole-lamina transition zone and can be used in the design of a future biomimetic junction in construction. [ABSTRACT FROM AUTHOR]

This article explores the use of 3D printers in chemistry education, highlighting their value as a tool for creating laboratory materials, models, and training materials. It emphasizes that 3D printing can be done easily and inexpensively, even without knowledge of CAD programs. The article provides examples and basic information on using 3D printers in the chemistry classroom, including the potential for creating microscale experiments and educational materials. It emphasizes the cost-effectiveness and accessibility of 3D printing technology for educational purposes and provides references to additional resources on the topic. [Extracted from the article]

Introduction. In recent decades, numerical methods for calculating concrete and reinforced concrete structures have developed significantly, taking into account the physically nonlinear behavior of the material. Such methods, in comparison with analytical ones, make it possible to describe the work of the material more accurately and reflect the main features of its stress–strain state. This makes it possible to perform more cost-effective and, in some cases, more reliable design solutions. Concept of the limit surface plays an important role in numerical methods. Limit surface, which is expressed by a condition (strength criterion), separates the elastic and plastic region of the material. Strength criteria must correspond to experimental data, provide a mathematically stable unique solution, and also have a set of parameters that can be easily determined from empirically based expressions or test data. The history of creation and improvement of concrete limit surfaces includes dozens of domestic and foreign works, many of which do not meet these requirements. The purpose of the current work is a comparative analysis of the most common strength criteria of concrete.Materials and methods. This study is based on the analytical generalization and systematization of the data received form domestic and foreign sources.Results. A detailed analysis of the most common domestic and foreign concrete limit surfaces was carried out.Conclusions. According to the analysis results, the comparison of the concrete limit surfaces was performed.

Fastened joints still represent the most common method for joining components within the aerospace industry. For fastened joints that experience high cyclical stresses, the application of the Split Sleeve Cold Expansion (SsCxTM) process has proven to be highly effective in extending the total fatigue life. This paper provides experimental strain measurements from around holes subjected to the SsCxTM process. Measurements on aluminum alloy coupons were taken using strain gauges and fiber optic strain sensors, with those measurements being used to validate the results from a three-dimensional (3D) digital image correlation (DIC) system. These validated experimental results were then compared to three separate finite-element analysis (FEA) process simulations each performed using one of three different material hardening models, Chaboche, kinematic and isotropic hardening. A finite-element leveling process was then used to compare the FEA results to the DIC measurements to highlight which hardening model provided the best correspondence to the DIC measurements. Although all hardening models provided reasonable similarity to the DIC results, for this particular aluminum alloy, an isotropic hardening model provided the best results. [ABSTRACT FROM AUTHOR]

In the case of solid slabs made of reinforced concrete that are usually subjected to bending, large areas of the structure are stressed well below their load-bearing capacity. Contrary to this are shell structures, which can bridge large spans with little material if designed according to the force flow. To improve the efficiency of ceiling slabs, we want to utilize the shell load-bearing behavior on a smaller scale by resolving the solid interior accordingly. In order to study a wide range of such constructions virtually, a parametric multi-objective simulation environment is being developed in an ongoing research project. The basic analysis approaches that were implemented are presented in this paper. The basic workflow, the used programs and material models, and their calibration on the tests on textile-reinforced concrete (TRC) samples are described.

The alternating active-phase algorithm (AAPA) is widely recognized as being efficient for multi-material topology optimization. It has the advantages of easy implementation and broad applicability, but faces shortcomings, such as a uniform punishment intensity for all elements, excessive gray elements, and slow optimization convergence. To overcome these shortcomings, proposed here is an enhanced AAPA (EAAPA), the core ideas of which are as follows. (1) A new equal-scale Heaviside projection function (EHPF) is proposed, with the scale factor introduced to adjust the physical density adaptively to overcome the challenges of the invariance of the density sum and the uniqueness of projecting faced by the traditional Heaviside projection function. This adaptation reduces the number of gray elements and accelerates the convergence. (2) An innovative solid isotropic material with exponential sigmoid function (SIMESF) is constructed, with a penalty threshold and a steepness factor introduced to divide different penalty intensity regions and control their transition steepness. This improves the applicability and flexibility of the interpolation model, addressing the issue of a single punishment intensity in the solid isotropic material with penalization. The parameter values of the SIMESF model are explored via the design of a bridge, and the performances of AAPA and EAAPA are evaluated via the designs of simply supported and cantilever beams. The results show clearly that EAAPA has significant advantages in terms of optimization effectiveness and convergence speed. [ABSTRACT FROM AUTHOR]

This research explores the dynamic responses of reinforced concrete (RC) slabs under high-velocity impacts. The study utilizes advanced numerical simulations to investigate the effects of varied impact loading and slab depths, unveiling complex rate-dependent behaviors (i.e., impact forces, reactions, accelerations, and displacements) across a diverse range of velocities. The alignment of simulation results with experimental data validates the robustness and accuracy of the employed approach. Additionally, an analytical model predicting the load-carrying capacity and deflection of these slabs under high-velocity loads is proposed. The results indicated that higher loading rates correlate with increased forces and damage until perforation. Analytical models exhibit strong performance within a ±10% error margin, and response surface analysis quantifies the impactor velocity's influence on load for a constant thickness. Overall, this investigation sheds light on the dynamic complexities of RC slabs subjected to high-velocity impacts, providing valuable insights for structural design considerations. [ABSTRACT FROM AUTHOR]

In the case of solid slabs made of reinforced concrete that are usually subjected to bending, large areas of the structure are stressed well below their load-bearing capacity. Contrary to this are shell structures, which can bridge large spans with little material if designed according to the force flow. To improve the efficiency of ceiling slabs, we want to utilize the shell load-bearing behavior on a smaller scale by resolving the solid interior accordingly. In order to study a wide range of such constructions virtually, a parametric multi-objective simulation environment is being developed in an ongoing research project. The basic analysis approaches that were implemented are presented in this paper. The basic workflow, the used programs and material models, and their calibration on the tests on textile-reinforced concrete (TRC) samples are described. [ABSTRACT FROM AUTHOR]

In the case of solid slabs made from reinforced concrete that are usually subjected to bending, large areas of the structure are stressed well below their load-bearing capacity or remain stress-free. Contrary to this are shell structures, which can bridge large spans with little material if designed well. To improve the efficiency of ceiling slabs, we want to utilize the shell load-bearing behaviour on a smaller scale by dissolving the solid interior accordingly. In order to be able to study a wide range of such constructions virtually, a parametric multi-objective simulation environment is to be developed in an ongoing research project, the basic analysis approaches of which are presented in this paper. In addition to the basic workflow and the programs used, the material models for TRC material compared and their calibration are described on the basis of tests on textile reinforced concrete (TRC) samples. Various material models were implemented within the commercially available software RFEM (Version 5.19). Laboratory tests on two different geometry solutions of TRC structures served to verify the models. The structures were selected in a way that differentiates between the bending and membrane actions to indicate the application fields for various approaches in the numerical modelling of TRC structures. [ABSTRACT FROM AUTHOR]

Finite element analysis (FEA) was used in this research to determine the dynamic behaviour of thermally modified Norway spruce (Picea abies Karst.). Damped modal analysis was selected for this purpose. Data obtained from non-destructive experimental work and from the literature provided input for modal analysis. The material characteristics were optimised and validated by experimental measurement; then the validated material model was mathematically described and FEA was applied. This work resulted in a generally validated material model of modified spruce based on material constants at various modification temperatures and humidities. Good agreement with a relative error of up to 7.1% was found between the numerical model and the experimental data. It was found that thermal modification caused an increase in resonance frequencies and higher humidity caused a decrease. The data provided and the model could prove useful for the non-destructive evaluation of thermally modified spruce and for predicting the behaviour of materials used in making musical instruments. [ABSTRACT FROM AUTHOR]

When a vehicle leaves the road, crash barriers stop it and prevent significant damage to the vehicle, its environment, and the occupants. Typically, such protection systems are made of simple steel, but fiber-reinforced composites can efficiently absorb and dissipate the impact energy at high-risk locations. In order to design such protective systems, material parameters under dynamic loading are necessary. Here, split Hopkinson pressure bar tests with unidirectional glass-fiber-reinforced epoxy of 58% glass fiber content are performed. The elastic response at strain rates between 300/s and 700/s in the loading direction parallel and perpendicular to the fiber is determined. From the measured data, a model of the time dependence of the elastic modulus is derived to enable the design engineer to lay out protective systems made of such GFRPs. [ABSTRACT FROM AUTHOR]

Laminated glass interlayer materials polyvinyl butyral (PVB) and SentryGlas® (SG, kuraray, Houstan, TX, USA) exhibit thermal viscoelastic behavior under dynamic tensile loading. Significant temperature and strain rate effects on the behavior of these interlayer materials pose a challenge for accurately modeling the dynamic response of laminated glass. Many researchers have simplified their approaches by modeling the response of the interlayer material using a bilinear approximation or established hyperelastic models. However, temperature and strain rate effects can be captured using the three-network viscoplastic (TNV) model. Therefore, the objective of this study is to calibrate material models for the thermal viscoelastic dynamic responses of PVB and SG interlayer materials. Uniaxial tensile tests were performed at strain rates of 2, 20, and 45 s−1 and temperatures of 0, 23, and 60 °C, and material models were calibrated using the experimental data. Finite element analysis using the calibrated material models successfully predicted the dynamic responses of PVB and SG under the experimental test conditions within a 10% error margin. This suggests that the calibrated models using the TNV model represent significant improvements over existing approaches to modeling the dynamic response of laminated glass. Similar procedures can be applied to other thermoplastics, laying the groundwork for establishing a standard calibration guide.

In this paper, the modified Ramberg-Osgood constitutive equations for calculating the stress-strain of steel at elevated temperatures using the parameters determined based on the transient state tensile test results achieved at the Helsinki University of Technology are verified. This is done by numerically comparing the global and local buckling capacities of I-shaped steel members incorporating the modified Ramberg-Osgood model along with the material model given in the fire section of Eurocode EN1993-1-2. For this purpose, a numerical model using the ABAQUS software was developed. Then, nonlinear analyses with imperfections (GMNIA) were performed to compare the buckling capacities of the steel columns and beams of four different hot-rolled cross-sections (IPE160, IPE180, HE100B, HE500B), made of steel grade S355, at three different temperatures (400°C, 500°C, 600°C). The results showed that adopting the modified Ramberg-Osgood model can lead to the same buckling capacities resulting when using the EN1993-1-2 material model for steel temperatures of less than 400°C. However, adopting this model for 600°C overestimates the buckling capacities in most cases.

Abstract Lightweight construction in modern car design leads to an increased usage of various aluminium semi-finished products. Besides sheet material, aluminium extrusion profiles are frequently used due to their high stiffness and variety of possible cross-sections. However, similar to sheet material, aluminium profiles exhibit limited formability in comparison to mild steel materials. One possibility to increase the forming limits of precipitation hardened aluminium alloys is the so-called Tailored Heat Treatment technology. By a local short-term heat treatment, the material is softened and the material flow can be controlled to reduce stresses in critical forming zones. The purposeful definition of the heat treatment zones is mandatory to improve the forming results. Therefore, numerical methods are necessary. In this investigation, a numerical process chain is presented. It combines the thermo-mechanical simulation of a local laser heat treatment with a subsequent bending process of the heat-treated profile using the alloy EN AW-6082. The temperature distribution, mechanical properties, and finally, the bending result of the numerical model are validated by experimental tests.

Appropriate material model will provide more accurate predictions for the mechanical response and damage mode of concrete structures, and thus developing a material model that is more consistent with the dynamic behavior of concrete has an important significance to obtain better numerical results. In this paper, an improved damage-plasticity material model for concrete is presented to predict its mechanical response subjected to dynamic loading. Based on the current extent of damage, the failure strength surface is modified through linearly interpolating between the maximum and yield strength surfaces or the maximum and residual strength surfaces. The shear, compacted and tensile damage are separately defined, and a unified hardening/softening function associated with the shear and compacted damage is introduced as the prediction of strain hardening and softening behaviors under compression. The Lode angle effect is considered for describing the reduction of shear strength on the compressive meridian, and the strain rate effect is considered by the radial enhancement method. The calibration method of material parameters is suggested according to the existing experimental data and empirical equations. The feasibility and accuracy of this improved concrete model are verified by the single element validation, and its performance improvement is discussed by comparing with the popular material models for concrete. The experiments and numerical simulations of split Hopkinson pressure bar (SHPB) are conducted for concrete and cement to further verify the validity and accuracy of this improved concrete model.

Cutting simulation is a crucial tool that enables engineers and operators to optimize machining processes virtually, before producing physical parts. The accuracy of these simulations relies heavily on validated models, encompassing both friction and material parameters. The prevalent technique for calibrating material models in cutting simulations is the inverse method. This state-of-the-art approach indirectly determines model parameters by comparing simulated outcomes with experimental data. However, the manual calibration process can be complex and time-consuming due to the intricacies of numerical simulation setups and the abundance of material model parameters. To address these challenges, this paper presents a novel fully-automated calibration approach utilizing multi-objective optimization algorithms. This approach integrates a modular design, simplifying the calibration process and enabling automatic calibration of any model parameters within cutting simulations. The approach has been successfully applied to calibrate the model parameters of AISI 1045 and X30CrMoN15-1 materials. Moreover, through a comparison of various optimization algorithms, this paper underscores the efficiency of the swarm optimizer in calibrating model parameters, particularly in scenarios with restricted computational resources. [ABSTRACT FROM AUTHOR]

Abstract This study leveraged milling steel fibers to enhance the flexural capacity of ultra-high-performance concrete (UHPC). We assessed UHPC's flexural performance, measuring compressive strength and flowability, considering three fiber types: milling, straight, and a hybrid. UHPC with milling fibers displayed superior compressive strength and flowability compared to straight fiber. Milling fibers consistently enhanced UHPC’s flexural capacity by over 120%, with a flowability reduction below 15%. Hybrid fiber demonstrated a balanced and commendable performance. Data-driven and theoretical flexural models were developed for UHPC with both fibers. the Gaussian process regression data-driven model outperformed the other 18 models, with an error below 3.5%. [ABSTRACT FROM AUTHOR]

The application of Polymethylmethacrylate (PMMA) can be traced back decades ago, which is widely utilized in aerospace, submarine, aquarium, detector, and biomedicine, and now is gradually utilized in civil engineering structures such as large space structures and decorative structures. Due to the different processing methods and service conditions, whether the existing research is applicate to constructional PMMA remains to be explored. The fire resistance of PMMA is poor, and the mechanical properties decline sharply with increasing temperature. Additionally, the description of stress–strain curves is the foundation of engineering application for a material. Therefore, a series of mechanical property tests of constructional PMMA under a quasi-static state were carried out herein, investigating the stress–strain curves and hardness at elevated temperatures and postfire conditions. Scanning electron microscopy (SEM) images were utilized for fractographic analysis at elevated temperatures. The effects of different tensile rates, thicknesses, and adhesive joints were explored. The test results indicated that 80°C was a boundary temperature, because the elastic modulus, peak strength, and yield strength decreased slowly below 80°C and sharply over 80°C due to the softening of PMMA. When the temperature reached 80°C, the peak strength dropped to approximately half of that of room temperature, and the ductility of the specimen increased significantly. To promote the application of constructional PMMA and provide guidance for engineers, a material model from 20°C to 100°C, where the buildings often encountered, was proposed. The mechanical properties, especially the stress–strain curves, of constructional PMMA at elevated temperatures and postfire conditions were comprehensively analyzed, and design suggestions were given. [ABSTRACT FROM AUTHOR]

In the case of solid slabs made from reinforced concrete that are usually subjected to bending, large areas of the structure are stressed well below their load-bearing capacity or remain stress-free. Contrary to this are shell structures, which can bridge large spans with little material if designed well. To improve the efficiency of ceiling slabs, we want to utilize the shell load-bearing behaviour on a smaller scale by dissolving the solid interior accordingly. In order to be able to study a wide range of such constructions virtually, a parametric multi-objective simulation environment is to be developed in an ongoing research project, the basic analysis approaches of which are presented in this paper. In addition to the basic workflow and the programs used, the material models for TRC material compared and their calibration are described on the basis of tests on textile reinforced concrete (TRC) samples. Various material models were implemented within the commercially available software RFEM (Version 5.19). Laboratory tests on two different geometry solutions of TRC structures served to verify the models. The structures were selected in a way that differentiates between the bending and membrane actions to indicate the application fields for various approaches in the numerical modelling of TRC structures.

Caloric cooling systems are potentially more efficient than systems based on vapour compression. Electrocaloric cooling systems use a phase transformation from the paraelectric to the ferroelectric state by applying or removing an electric field to pump heat. Lead scandium tantalate (PST) materials show a first-order phase transition and are one of the most promising candidates for electrocaloric cooling. To model caloric cooling systems, accurate and thermodynamically consistent material models are required. In this study, we use a phenomenological model based on an analytical equation for the specific heat capacity to describe the material behaviour of bulk PST material. This model is fitted to the experimental data, showing a very good agreement. Based on this model, essential material properties such as the adiabatic temperature change and isothermal entropy change of this material can be calculated. [ABSTRACT FROM AUTHOR]

Bi-axial state is the dominant stress state experienced by the sheet metal during various forming processes, which requires a thorough understanding and modelling for process designs. In this paper, effects of equal bi-axial stress-state on the hot deformation behavior of titanium alloys are thoroughly investigated using hot bulging tests, and is further compared to the uniaxial stress state. Firstly, a specific hot bulging test device enabling a uniform temperature field and constant control of strain rate was established, using which, systematic hot bulging tests at various temperatures (750–850 °C) and strain rates (0.001–0.1 s−1) of the near-alpha phase TA32 sheets were conducted to determine the hot equal bi-axial bulging behavior. Based on the testing data of force and geometry variations of bulged domes, the equivalent stress–strain curves were calculated. Secondly, a plane-stress visco-plastic plane-stress model of near-alpha TA32 sheets was developed for the first time, enabling both the uniaxial and biaxial flow behavior and forming limits to be precisely predicted. The prediction accuracies for uniaxial and biaxial cases are 93.5% and 89%, respectively. In the end, the uniform deformation resulting from the strain and strain rate hardening was determined, which contributes to the understanding of the stress-state effect on hardening preliminarily. The plane stress visco-plastic model provides an efficient and reliable material model for finite element (FE) simulations of hot forming titanium alloy sheets. [ABSTRACT FROM AUTHOR]

An approach to the design justification of turbine blocks with steel-lined reinforced concrete spiral case of high-head hydraulic power plants is proposed. The approach is based on domestic and foreign experience in numerical and experimental studies of such structures. The approach is demonstrated by analyzing the stress-strain state of the turbine blocks of the Rogun HPP. Recommendations on further improvement of the approach are formulated. [ABSTRACT FROM AUTHOR]

Under the bending load generated by automobile collision, the composite safety components should have the ability to resist deformation and dissipate crashworthiness energy. In order to determine the mechanical parameters of the progressive damage material model of a woven carbon fiber composite thin-walled beam in the three-point bending condition, the mechanical properties test of the woven carbon fiber composite material and the three-point bending experiment of square tubes made by this material were carried out, thus got the basic mechanical parameters, bending failure history and force-deformation characteristics. Then the effects of the non-test parameter in the progressive damage material model on the simulation results were analyzed and the effectiveness of the multilayer shell modeling method were discussed. By comparing with the experimental results, the non-experimental parameters and effective simulation modeling methods for the progressive damage model of composite materials were gotten. The obtained material properties can be used for the crashworthiness simulation analysis of this material structure in similar working conditions.

There is a growing need to develop accurate nonlinear viscoelastic material models and tools that could describe the complex nonlinear behavior of being developed composite material systems at their simulations at high loads and temperatures or to move the industry towards more sustainable bio-based alternatives. Developing such models in 3D formulation for materials with changing material state due to physical aging, change of crystallinity or degree of cure is also imperative since the loading is mostly multiaxial in real-live applications and manufacturing processes. The present paper contains the derivation of two material models with varying complexity and accuracy. The incremental procedure for implementation of the nonlinear viscoelastic material model within the numerical analysis was presented. Two relatively simple simulations with the incremental methodology developed were performed, namely triaxial mechanical loading and thermal stress development during the manufacturing process. The results obtained showed significant differences between stresses calculated using 1D and 3D simulations. Significantly higher stresses obtained in 3D simulations demonstrated the necessity of 3D models. [ABSTRACT FROM AUTHOR]

Soft tissue material properties are vital to human body models that evaluate interactions between the human body and its environment. Such models evaluate internal stress/strain responses in soft tissues to investigate issues like pressure injuries. Numerous constitutive models and parameters have been used to represent mechanical behavior of soft tissues in biomechanical models under quasi-static loading. However, researchers reported that generic material properties cannot accurately represent specific target populations due to large inter-individual variability. Two challenges that exist are experimental mechanical characterization and constitutive modeling of biological soft tissues and personalization of constitutive parameters using non-invasive, non-destructive bedside testing methods. It is imperative to understand the scope and appropriate applications for reported material properties. Thus, the goal of this paper was to compile studies from which soft tissue material properties were obtained and categorize them by source of tissue samples, methods used to quantify deformation, and material models used to describe tissues. The collected studies displayed wide ranges of material properties, and factors that affected the properties included whether tissue samples were in vivo or ex vivo , from humans or animals, the body region tested, body position during in vivo studies, deformation measurements, and material models used to describe tissues. Because of the factors that affected reported material properties, it is clear that much progress has been made in understanding soft tissue responses to loading, yet there is a need to broaden the scope of reported soft tissue material properties and better match reported properties to appropriate human body models. • Soft tissue properties were collected from animals and humans, in-vivo and ex-vivo. • Sample source, body region and position, and testing conditions affected properties. • Models and tissue properties should match to ensure realistic approximations. • Guidelines for reporting uncertainty in models depend on material characterization. • Growing efforts in personalized soft tissue properties may reduce uncertainty. [ABSTRACT FROM AUTHOR]

A material testing apparatus for measuring the biaxial deformation behavior of a polymer tube is developed to quantitatively evaluate the deformation behavior of polymeric materials. The testing apparatus can apply axial force and internal pressure to a tubular specimen. A noncontact strain measurement system, where the biaxial strain components and the radius of curvature in the axial direction of the specimen are continuously measured to control the stress path applied to the specimen, is also developed. Thermoplastic elastomer tubes with an outer diameter of 15 mm and a thickness of 2 mm are used as test samples. The samples are subjected to linear stress paths with stress ratios of σ ϕ : σ θ = 1 : 0 , 4 : 1 , 2 : 1 , 4 : 3 , 1 : 1 , 3 : 4 , 1 : 2 , 1 : 4 , and 0:1, where σ ϕ and σ θ are the axial and circumferential stress components, respectively, applied to the center of the bulging specimen. Biaxial stress–strain curves are measured for each linear stress path at a nearly constant logarithmic strain rate of 1 × 10–3 s−1. The contours of equal plastic work plotted in the σ ϕ - σ θ stress space show significant anisotropy of the test material. A material model for accurately reproducing both the work-hardening behavior and deformation behavior of the test samples is proposed. [ABSTRACT FROM AUTHOR]

Testing full-scale structures in the laboratory is not always doable nor financially feasible, especially for large structures. Therefore, these structures are often modeled with Finite Element Analysis (FEA) software and packages, such as Abaqus, to understand their actual behaviors under special simulated loading and material-behavioral considerations. This study developed a material model that simulates load-induced cracking in reinforced concrete (RC) elements in the FEA of structures. The simulation of complete stress–strain concrete behavior under tension and compression (including damage characteristics) requires the application of numerical material models, potentially producing the stress–strain curves. These models include strain-softening regimes that presuppose the use of ultimate compressive concrete strength and that can be practically implemented for existing or future RC structures. The method presented in this study is valuable because it assesses existing RC structures when detailed test results are not available. However, the implemented numerical models were slightly altered in order to compare them with the damaged plasticity models available in the research literature. These are mainly the smeared crack concrete model, the brittle crack concrete model, and the concrete damaged plasticity model, which are all typically suitable for RC elements. The methodologies proposed here provide accurate and realistic modeling of the plastic damage of RC members. Although numerically extensive and very time-consuming, it is demonstrated that the material and damage modeling presented in this paper can be used to accurately represent the behavior of actual structural members tested in research laboratories. This suggests that it is applicable to structures for which experimental tests or monitoring data are not available. [ABSTRACT FROM AUTHOR]

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Tests of dry clay were carried out in a uniaxial stress state using the experimental setup which implements the split Hopkinson pressure bar method. Based on the results of these experiments, the compressive strength of clay was determined as an important element of S.S. Grigoryan's model of the soil medium. In addition, the parameters of this model are determined from the results of experiments using the modified Kolsky method with a sample enclosed in a rigid cage. To verify the model of the soil medium, special experiments were carried out on the penetration of striker with conical tips into dry clay in a reversed settings. Using this identified model in the LS-Dyna software package, numerical simulation of penetration into clay was carried out under conditions similar to those carried out the reversed experiments. Comparison of the results of physical and numerical experiments showed their satisfactory agreement at a dry friction coefficient of 0.5. [ABSTRACT FROM AUTHOR]

Stephania japonica is a slender climbing plant with peltate, triangular-ovate leaves. Not many research efforts have been devoted to investigate the anatomy and the mechanical properties of this type of leaf shape. In this study, displacement driven tensile tests with three cycles on different displacement levels are performed on petioles, venation and intercostal areas of the Stephania japonica leaves. Furthermore, compression tests in longitudinal direction are performed on petioles. The mechanical experiments are combined with light microscopy and X-ray tomography. The experiments show, that these plant organs and tissues behave in the finite strain range in a viscoelastic manner. Based on the results of the light microscopy and X-ray tomography, the plant tissue can be considered as a matrix material reinforced by fibers. Therefore, a continuum mechanical anisotropic viscoelastic material model at finite deformations is proposed to model such behavior. The anisotropy is specified as the so-called transverse isotropy, where the behavior in the plane perpendicular to the fibers is assumed to be isotropic. The model is obtained by postulating a Helmholtz free energy, which is split additively into an elastic and an inelastic part. Both parts of the energy depend on structural tensors to account for the transversely isotropic material behavior. The evolution equations for the internal variables, e.g. inelastic deformations, are chosen in a physically meaningful way that always fulfills the second law of thermodynamics. The proposed model is calibrated against experimental data, and the material parameters are identified. The model can be used for finite element simulations of this type of leaf shape, which is left open for the future work. [ABSTRACT FROM AUTHOR]

The need for higher capacity battery cells has increased significantly during the past years. Therefore, the subject of this study is to investigate the behavior of high performance 21700 Lithium-Ion cylindric battery cells under several abuse conditions, represented by high mechanical loads with different velocities and states of charge (SoC), and to develop a finite element analysis (FEA) model, using the OpenRadioss' explicit solver capabilities. The present study is focused on the investigation of the behavior of these cells under high mechanical loads with different loading velocities and different states of charge. The aim of the study is to provide a tool to predict the point of an internal short circuit in FEA, with a very good approximation. Experiments were completed using a hydraulic flat-compression test, set up at four different states of charge, 40%, 60%, 80% and 100%, and three different loading velocities of 10 mms−1, 100 mms−1 and 1000 mms−1. A homogenized FEA model is developed to predict the internal damage of the separator, which can lead to a short circuit with a possible thermal runaway under abusive load conditions. The present model, in combination with well identified material and fracture parameters, succeeded in the prediction of the mechanical behavior at various states of charge and mechanical loading conditions; it can also be used for further crashworthiness analysis within a full-car FEA model. This accurate cell model will be the first building block to optimize the protective structures of batteries in electric vehicles, and reduce their weight through a deeper understanding of their overall behavior during the different crash cases. [ABSTRACT FROM AUTHOR]

The topic of this paper is experimental and numerical analysis of the impact strength of unreinforced concrete slabs. Impact strength of concrete is significant in case of some accidental loads during exploitation. Impact strength can be determined experimentally, using Drop-weight test, Charpy test, Projectile impact test, Explosive test, etc. In this research, a numerical model for determining the impact strength of concrete slabs based on Finite element method (FEM) and high-end engineering software has been proposed. Modelling approach to this problem was applying the Explicit dynamics FEM analysis. Thereat, two different existing material models for concrete were enforced: Concrete damage plasticity model – CDP (implemented in ABAQUS/Explicit software), and the Riedel-Hiermaier-Thoma model – RHT (implemented in ANSYS Workbench software). Analysis parameters for both material models, necessary as input data, have been determined through a series of FEM analyses and validated by performed experiments, using drop-weight test. Results of the numerical analyses have been compared with the experimental ones, as well as mutually. Advantages and drawbacks of both material models are highlighted, as well as the reliability of the proposed numerical models. The proposed numerical FE models, confirmed by experiments, can be successfully used for determining impact strength of concrete slabs in further research. [ABSTRACT FROM AUTHOR]

The reliability of numerical simulations of the structural response of nonhomogeneous materials to high velocity loadings is highly dependent on the used material model and parameters. For nonhomogeneous materials, such as fibres, reinforced concrete is widely used for the Winfrith model, but the question of appropriate material parameters for Ultra-High Performance Fibre Reinforcement Concrete (UHPFRC) under high velocity loadings is still open. The article deals with possible method of inverse identification of material parameters of a UHPFRC slab under blast loading for a Winfrith material model. Possible application is in the field of numerical simulation of protective or critical infrastructure response to blast loading. Experimental measurement of the time–deflection curve through laser scanning using the triangulation method gave us input data for an inverse identification phase conducted in Optislang software. Obtained material parameters from a given range are optimized for blast loading and their Pearson's correlation coefficient provides us information about their significance for simulation. [ABSTRACT FROM AUTHOR]

Models for the elastic material properties of wood aim to predict the mechanical response of wooden structures to external loading. Traditionally, the variability of these properties in trees is described by a taxonomy of growth defects that is typically based on visual indicators in the material. This includes curvature, knots, and spiral grain models. Existing meso- and macro-scale models fail to describe the uncertainty connected to the local heterogeneity of the material. In this paper, we propose a novel meso-scale model that describes the natural variability of Norway spruce morphology and material properties based on random field theory. Our approach removes the need for a taxonomy of growth defects and enables uncertainty quantification of the stiffness and density in a straightforward fashion using simulations. This may enhance confidence for stiffness-graded applications, where the dynamic resonant behavior of wood structures is relevant and growth anomalies are present. Further, our stochastic models can generate images that realistically mimic wood patterns, which is relevant for applications like synthetic wood panels and flooring. [Display omitted] • Validated meso-scale material model for wood using fiber direction and density. • Stochastic model for natural growth features: spiral grain, taper, and curvature. • Probabilistic model for branch knot distribution in the growth direction. • Generation of images that mimic real wood annual ring patterns. [ABSTRACT FROM AUTHOR]