Modeling Of Material Behavior Research Articles

Trajectory generation for adhesive dispensing robots by modeling of material behavior

It is difficult for robots to manipulate flexible objects, and adhesive dispensing is one such task. In this task, the adhesive material is pulled by a dispensing robot, which is problematic to predict. In this paper, we propose an analysis-based and a learning-based model to predict the behavior of the adhesive material, and a method to explore the robot trajectory. While analysis-based models consider physical behavior and require less training data, they are limited to specific physical behaviors. Learning-based models, on the other hand, can model many physical behaviors, but require a lot of training data. Finally, we use the predictions of these models to perform experiments and evaluate the differences between the target adhesive trajectory and the actual application results.

Thermodynamically Consistent Evolution Equations in Continuum Mechanics

This paper addresses the modelling of material behaviour in terms of differential (or rate) equations. To comply with the objectivity principle, recourse is made to invariant fields in the Lagrangian description or to objective time derivatives in the Eulerian description. The thermodynamic consistency is investigated in terms of the Clausius–Duhem inequality with two unusual features. Firstly, the (non-negative) entropy production is viewed as a constitutive function per se. Secondly, the inequality is viewed as a constraint on the pertinent fields and it is solved by using a representation formula, which allows for the the admissibility of a class of models. For definiteness, models of heat conduction are established, within Lagrangian descriptions, while models of the Navier–Stokes–Voigt fluid are investigated within Eulerian descriptions. In connection with thermo-viscous fluids, evolution equations are investigated within the Eulerian description. It is shown that the thermodynamic consistency is compatible with both objective and non-objective evolution equations.

Determination of Dynamic Stresses and Displacements under the Action of an Impact Load on a Two-Layer Structure during the Indentation Process

Introduction. Numerous researchers of the reliability of building structures pay attention to hardness, an important characteristic of the structural material. It is determined by indentation — pressing the tip of the tool into the surface. The advantages of dynamic indentation methods and the distribution of stress intensity on the surface and inside the sample are investigated. However, the condition of layered materials on impact has been poorly studied. The objective of the presented work is to consider indentation for a two-layer sample and determine the sensitivity of the top layer to the strength of the substrate. This will allow us to identify significant characteristics of the strength properties of homogeneous and heterogeneous structures.Materials and Methods. An elastoplastic model of material behavior and a shock indentation scheme were used, which took into account the masses of the indenter and the striker coupled by linear springs. The surface of the indenter was conical, the opening angle was 120°. The impact was simulated in the MATLAB system. Finite element model in Ansys APDL was used to verify the data and analyze the results of the experiment. Traditional models of elasticity theory were used for calculations. The behavior of the material in the zone of plastic deformation was described using the options of multilinear isotropic hardening and the von Mises plasticity criterion.Results. The results of comparing three versions of varying the level of yield strength in the bottom layer are presented: when the yield strength in the bottom layer is half as high as the top one, equal to it, and twice as high. Displacements at different observation points for samples with a top layer of 2 mm and 1 mm were analyzed. In the first case, under horizontal shear, the displacement indices inside the sample did not change if the yield strength level was twice lower or higher than in the top one. If these indicators were equal, the difference became noticeable. In the second case (layer 1 mm), the difference in displacement was visible at all observation points. Thus, it can be reasonably concluded that a structure with a smaller top layer is more sensitive to impact. In the course of the research, it became known that vibrations associated with the transition to the plasticity zone occurred in the 2 mm zone, and elastic damping vibrations occurred below this zone. We solved the classification problem for the top layer of the material with changing characteristics of the base. The indicator for comparison was the Brinell hardness (HB) in the range of 200–600. The results were processed using a neural network and visualized in the form of graphs. The accuracy of its calculations was 98%.Discussion and Conclusion. To determine the strength properties of homogeneous structures, it is sufficient to characterize the speed of displacement inside the sample. For an inhomogeneous structure, additional parameters should be introduced — displacements on the surface and inside the sample at fixed observation points. An integrated approach to determining the strength properties of an inhomogeneous structure improves the accuracy of calculations, and the use of neural networks increases their speed.

Multiphysics modeling and simulation of monolayer flow and die swelling in industrial tube extrusion process

AbstractIn a regular extrusion process for thermoplastic specimen, the material behavior in dies and its rheological properties have a major influence on the mechanical properties and the quality of the extruded product. This study outlines the multiphysical model, which has been adapted to address the specific issues associated with polyamide 12 polymer extrusion. A series of numerical simulations, based on the modeling of material behavior, have been conducted using the computational code Comsol Multiphysics®. These simulations have been applied to the study of polymer melt flows through an industrial extrusion die. The objective of this study is to analyze the influence of the imposed extrusion parameters on the physical field distribution and the material displacement within the die. The die swell at the exit of the extrusion die has been investigated as a function of the imposed pressure. The progression of the polymer flow front inside the extrusion tool and the swelling rates have been analyzed. In particular, the phenomenon of delayed swelling at high pressure has been highlighted at high pressure.Highlights Polymer swelling at industrial extrusion die exit is investigated. Polymer melt extrusion within industrial extrusion tool is numerically simulated. Flow front progression and extrudate swell are analyzed. Effect of extrusion pressure on instabilities and die swell is highlighted.

A covariant formulation for finite strain modelling of orthotropic elasticity and orthotropic plasticity with plasticity-induced evolution of orthotropy: Application to natural fibres

We introduce a rate-independent model for orthotropic elastic and orthotropic plastic material behaviour in a hyper-elasto-plastic framework at finite strains. The model is based on the postulate of covariance and does not rely on a multiplicative decomposition of the deformation gradient. Furthermore, a plastic-deformation-induced evolution of orthotropy is considered, similar to the notion of plastic spin. We propose that the orthotropic strain energy function and the orthotropic yield criterion are guided by identical structural tensors that evolve with plasticity. The modelled material behaviour is significant for natural fibres such as flax, hemp, or pulp fibres. Our formulation has three findings. Firstly, the covariant formulation of plasticity provides rate equations for the plastic variables and the structural tensors suitable for reproducing stress–strain diagrams of natural fibres. Secondly, the introduction of plastic-deformation-induced evolution of orthotropy in the proposed covariant setting results in a non-associative plasticity algorithm. Thirdly, the covariant setting allows the incorporation of suitable constitutive equations for the structural tensors to evolve orthotropy. The latter successfully models the stiffness increase in stress–strain diagrams of cyclic tensile tests of natural fibres.

Post-fire structural material behaviour of high- and ultra-high-strength steels – Experimental study and aids for assessment for further use and potential reuse after fires

A thorough understanding and realistic modelling of the essential post-fire material behaviour is crucial for a safe assessment of the residual structural performance of steel components and the reliable further usage of steel structures after fires. This paper presents a comprehensive experimental study of the constitutive material behaviour after heating-cooling cycles of two quenched and tempered high-strength steels (S690QL, S960QL) as well as two thermomechanically rolled steels (S960M, S1100M). The results are compared to both the behaviour of grade S355J2+N mild steels and a comprehensive database of existing post-fire tests. Except for high- and ultra-high-strength steels, which are exposed to very high temperatures above the A1-phase-transformation-temperature during fires, the assumption of reversibility of the mechanical properties for structural designs of steel structures has been confirmed. At high and very high steel temperatures, the microstructure changes and the strength properties after fire are significantly lower than those of virgin high-strength steel specimens. The study thus provides the basis for reliable structural designs and future normative guidance of the post-fire structural steel designs.

Exploring shear nonlinearity of plain-woven composites at various temperatures based on machine learning

Plain-woven composites are extensively utilized across various fields; however, it exhibits significant shear nonlinearity, especially at high temperatures. This study aims to propose a machine learning (ML) based constitutive model using Gaussian Process Regression (GPR), which is able to effectively characterize the shear nonlinearity of plain-woven composites at different temperatures. The shear nonlinearity of T800 carbon fiber-reinforced epoxy-based plain-woven composites are investigated by carrying out in-plane shear experiments, and the data sets considering temperature effects are established accordingly. Compared with traditional constitutive models, the proposed ML-based model excels in predicting shear nonlinearity, even at temperatures not included in the training set. The integration of this ML-based constitutive model into the finite element (FE) simulation framework achieves high consistency between simulation and experimental results, thereby validating the significant application of ML in complex material behavior modeling and FE analysis.

Modelling of material behavior for additively manufactured 17-4 PH stainless steel produced by fused filament fabrication

This paper proposes a model to predict the tensile characteristics of metal fused filament fabricated (MFFF) components. The proposed model consists of mathematical, experimental, and finite element (FE) models. The mathematical model was constructed based on the composite laminate theory and was combined with experiments for basic layup of 0° and 90° raster angle to describe the behavior of MFFF parts. The FE model was built to simulate the behavior of MFFF parts in a virtual environment and its validity was verified using independent experiments for a more common layup of +45°/−45°.

The Effect of Oil Contaminated on Collapse Pattern in Gypseous Soil Using Particle Image Velocimetry and Simulation

Gypseous soil covers approximately 30% of Iraqi lands and is widely used in geotechnical and construction engineering as it is. The demand for residential complexes has increased, so one of the significant challenges in studying gypsum soil due to its unique behavior is understanding its interaction with foundations, such as strip and square footing. This is because there is a lack of experiments that provide total displacement diagrams or failure envelopes, which are well-considered for non-problematic soil. The aim is to address a comprehensive understanding of the micromechanical properties of dry, saturated, and treated gypseous sandy soils and to analyze the interaction of strip base with this type of soil using particle image velocimetry (PIV) measurement and Plaxis 3D simulation. The results showed that high-resolution digital cameras captured soil deformation using PIV, displacement fields, and velocity vectors were generated, which helped identify different sand movement zones. Further, PIV showed punching and general shear failure in uncontaminated and soaked contaminated gypsum soils, respectively. Moreover, the Plaxis results corresponded well with the PIV, as material behavior models are essentially simplified representations of the actual behavior of footing and soil. Understanding soil deformation behavior is crucial for accurate engineering calculations and designs, making these findings valuable for geotechnical and construction engineering applications. Doi: 10.28991/CEJ-2024-010-07-016 Full Text: PDF

Influence of specimen width on the elongation-to-fracture in cyclic-bending-under-tension of commercially pure titanium sheets

In recent publications, we have shown that repeated bending and unbending during tension can significantly increase the percent elongation-to-fracture (ETF) of metallic sheets. A custom-built machine for cyclic bending under tension (CBT) testing was designed and used to test several sheet metals. In particular, the improvements in ETF using CBT were over 3× relative to simple tension (ST) for commercially pure titanium (cp-Ti) sheets. The present paper evaluates the influence of specimen width on the achieved ETF in CBT of cp-Ti sheets. To facilitate the study, the CBT machine was furnished with wide grips to enable processing of sheets in addition to testing narrow strips. The ETF was observed to reduce with the sheet width. To rationalize the observations, the strain rate-independent plasticity theory of von Mises (J2) with isotropic expansion of yield surfaces of cp-Ti was used in finite elements (FE) to perform a set of simulations. To facilitate the FE simulations of the CBT process stretching the sheets of cp-Ti far beyond the point of maximum uniform strain in ST, the post-necking hardening behavior was inferred along RD, TD, and 45 sheet directions using an established methodology combining ST tests, CBT tests, and modeling material behavior during CBT. Simulated geometries and mechanical fields were found to be in good agreement with corresponding measurements for every specimen width. While predicted axial strains were similar for every width, the strain path shifted from uniaxial tension for the narrow specimen toward plane-strain tension for the wider specimens. As such, as plane-strain tension was approached via progressively wider specimens, the width strains reduced, while the thinning strains increased. The increase in the thinning strain was established as the primary reason for the reduced ETF with increasing sheet width. Experimental and FE simulation results along with the insights into the influence of specimen width on the ETF in CBT of cp-Ti are presented and discussed.

Methods for characterization and continuum modeling of inhomogeneous properties of paper and paperboard materials: A review

The potential of paper and paperboard as fiber-based materials capable of replacing conventional polymer-based materials has been widely investigated and evaluated. Due to paper’s limited extensibility and inherent heterogeneity, local structural variations lead to unpredictable local mechanical behavior and instability during processing, such as mechanical forming. To gain a deeper understanding of the impact of mechanical behavior and heterogeneity on the paper forming process, the Finite Element Method (FEM) coupled with continuum modeling is being explored as a potential approach to enhance comprehension. To achieve this goal, utilizing experimentally derived material parameters alongside stochastic finite element methods allows for more precise modeling of material behavior, considering the local material properties. This work first introduces the approach of modeling heterogeneity or local material structure within continuum models, such as the Stochastic Finite Element Method (SFEM). A fundamental challenge lies in accurately measuring these local material properties. Experimental investigations are being conducted to numerically simulate mechanical behavior. An overview is provided of experimental methods for material characterization, as found in literature, with a specific focus on measuring local mechanical material structure. By doing so, it enables the characterization of the global material structure and mechanical behavior of paper and paperboard.

Automated segmentation of large image datasets using artificial intelligence for microstructure characterisation and damage analysis

Many properties of commonly used materials are driven by their microstructure, which can be influenced by the composition and manufacturing processes. To optimise future materials, understanding the microstructure is critically important. Here, we present two novel approaches based on artificial intelligence that allow the segmentation of the phases of a microstructure for which simple numerical approaches, such as thresholding, are not applicable: One is based on the nnU-Net neural network, and the other on generative adversarial networks (GAN).Using scanning electron microscopy images collected from large areas (∼1 mm2) of dual-phase steels as a case study, we demonstrate how both methods effectively segment intricate microstructural details, including martensite, ferrite, and damage sites, for subsequent analysis.Either method shows substantial generalizability across a range of image sizes and conditions, including heat-treated microstructures with different phase configurations. The nnU-Net excels in mapping large image areas. Conversely, the GAN-based method performs reliably on smaller images, providing greater step-by-step control and flexibility over the segmentation process.This study highlights the benefits of segmented microstructural data for various purposes, such as calculating phase fractions, modelling material behaviour through finite element simulation, and conducting geometrical analyses of damage sites and the local properties of their surrounding microstructure.

Insight into single-helix intelligent shape memory polymer cables: modeling and optimization under finite sliding contact

This pioneering study focuses on the finite element analysis (FEA) of thermomechanical properties of shape memory polymer (SMP) wire ropes and their components under both small- and finite-sliding contact deformation. To validate the FEA, we need to validate both geometric modeling and non-linear material behavior. Owing to intricate geometry, as well as excessive wire interactions in the structure, this part is studied by simulating a 1 × 37 steel wire rope and then comparing it with existing experimental data. To evaluate the response of non-linear material behavior, we employ the available numerical results to model the thermomechanical property of an SMP rectangular bar under a uniaxial test and then verify both constrained and unconstrained recovery behavior. After rigorous validation, two configurations of 1 × 7 and 1 × 27 SMP cables are modeled based on the thermo-visco-hyperelastic constitutive framework for acrylate polymer systems. Upon exerting an axially tensile load on these 1 × 7 and 1 × 27 SMP wire ropes, the response of force and shape recovery, as well as the normal and shear stress distributions, are measured under constrained and unconstrained conditions. For a deeper physical understanding, the influences of different temperature rates (5 and 1 °C min−1), inter-wire sliding frictional coefficient (0.1–0.6), and multiple-shape programming on the stress-strain-temperature relations of these SMP cables are also investigated. Furthermore, based on optimizing two cable factors of diameter and helix angle, and using the design of experiments method, the specific energy of a 1 × 6 SMP cable is maximized. Under different thermomechanical loadings, this study tries to cast light on the remarkable features and possible potential applications of these newly developed SMP actuators which may foster unparalleled advancements in various industries.

Nonlinear electro-elastic finite element analysis with neural network constitutive models

In the present work, the applicability of physics-augmented neural network (PANN) constitutive models for complex electro-elastic finite element analysis is demonstrated. For the investigations, PANN models for electro-elastic material behavior at finite deformations are calibrated to different synthetically generated datasets describing the constitutive response of dielectric elastomers. These include an analytical isotropic potential, a homogenised rank-one laminate, and a homogenised metamaterial with a spherical inclusion. Subsequently, boundary value problems inspired by engineering applications of composite electro-elastic materials are considered. Scenarios with large electrically induced deformations and instabilities are particularly challenging and thus necessitate extensive investigations of the PANN constitutive models in the context of finite element analyses. First of all, an excellent prediction quality of the model is required for very general load cases occurring in the simulation. Furthermore, simulation of large deformations and instabilities poses challenges on the stability of the numerical solver, which is closely related to the constitutive model. In all cases studied, the PANN models yield excellent prediction qualities and a stable numerical behavior even in highly nonlinear scenarios. This can be traced back to the PANN models excellent performance in learning both the first and second derivatives of the ground truth electro-elastic potentials, even though it is only calibrated on the first derivatives. Overall, this work demonstrates the applicability of PANN constitutive models for the efficient and robust simulation of engineering applications of composite electro-elastic materials.

An efficient method for multiscale modelling of the mechanical properties of additively manufactured parts with site-specific microstructures

The ability to modulate microstructures at different locations within a part (i.e., site-specific microstructures) can lead to tailored properties and enhanced performance. However, it remains challenging to efficiently model the mechanical response of such materials due to the need for extensive multiscale analysis. To address this issue, we demonstrate through microstructure-based finite element simulations, that the mechanical properties of a randomly distributed two-phase microstructure are primarily dependent on the phase fraction. Therefore, by establishing a mathematical relationship between the phase fraction and mechanical properties, the local material properties can be efficiently calculated from the local microstructure. Later, these site-specific properties were incorporated into a finite element structure to predict the global mechanical properties of the sample part. To validate the effectiveness of the proposed method, low alloy steel with site-specific microstructures was fabricated using binder jet additive manufacturing by depositing varying concentrations of carbon binder at different locations inside the part. We observed a strong agreement between the experimental and simulation stress-strain responses of the steel samples. This method can potentially pave the way for the development of a non-destructive qualification method for additively manufactured parts, as well as provide an efficient approach to multiscale modeling of material behavior, which may help accelerate the design and innovation of novel material systems.

LOW-CYCLE FATIGUE OF STRUCTURES WITH STRESS CONCENTRATORS

The results of experimental and theoretical studies of structures with stress concentrators under cyclic loads are presented. The studies were carried out on cylindrical samples with a V-shaped annular recess under mild cyclic loading. The tests were carried out on samples of the BrH08-Sh alloy with a cyclic change in the tensile load from 0 to 10.8 kN. Under such loading, the material in the recess area undergoes cyclic elastoplastic deformation, which leads to destruction as a result of low-cycle fatigue. For mathematical modeling of the elastic-plastic behavior and destruction of structures with stress concentrators, a variant of the theory of plasticity based on the theory of flow under combined hardening is used. In the chosen plasticity model, a memory surface is introduced that separates the processes of monotonous and cyclic loading. This separation makes it possible to take into account various features of isotropic and anisotropic hardening of the material. Anisotropic hardening is represented as a sum of microstresses of three different types, which make it possible to describe the effects of landing and stepping of the elastic-plastic hysteresis loop. The plasticity model makes it possible to assess the damaged state of a material based on the kinetic equation of damage accumulation based on the energy principle (the operation of microstresses in the field of plastic deformations). The material behavior model is embedded in the finite element software package SIMULIA Abaqus. The results of calculations and experiments on the magnitude of axial deformation, the average axial deformation on the surface of the recess and the number of cycles to failure are compared. It is found that in a design with a recess with a radius of 1 mm, a soft asymmetric loading with a unilateral accumulation of deformation (ratcheting) is realized in the concentration zone.

Two-parameter models of brittle materials behavior under uniaxial compression

Numerical and analytical models are widely presented in the literature. In this report, analytical models of only one class are considered, the first of which is the Furamura model. Models of this class do not require a large amount of input data; in addition, their mathematical description does not contain complex equations. The researchers initially used these models to analyze the behavior of concrete at high temperatures. The current scope of these models covers applied analysis of the behavior of rocks, frozen soils, and other materials, including their behavior on the downward branch under controlled deformation. The purpose of this report is to discuss not only the positive characteristics of the models of the class under consideration, but also to draw the readers' attention to the limitations in the use of the models, which will contribute to their improvement and effective application for sustainable development.

Assessment of the Influence of Protective Polymer Coating on Panda Fiber Performance Based on the Results of Multivariant Numerical Simulation.

This article considers the deformation behavior of Panda optical fiber using different models of material behavior for the tasks of predicting residual stresses after drawing when cooling from 2000 °C to room temperature (23 °C) and indenting the fiber into an aluminum half-space at different parameters. These studies were conducted for single- and double-layer protective coatings (PCs), at different values of external load and thickness of single-layer PC. This paper determined the fields of residual stresses in the fiber formed during the drawing process. They are taken into account in modeling the fiber performance in the further process of this research. This article investigated two variants of PC behavior. The influence of behavior models and the number of covering layers on the deformation of the "fiber-half-space" system was analyzed. This paper establishes qualitative and quantitative regularities of the influence of the external load magnitude and relaxation properties of PCs on the deformation and optical characteristics of Panda optical fiber.

Calibrating DC01 Material Properties for Finite Element Analysis with Abaqus and Isight

Abstract This article explores the process of calibrating the properties of DC01 materials for finite element analysis using ABAQUS and Isight. Precise calibration of yield strength and tensile strength is crucial for accurately modeling material behavior under various loading conditions. The article details the sample preparation process, deformation measurements, and tensile tests to obtain experimental data. These data are then used to calibrate the DC01 material model in ABAQUS with the assistance of Isight, ensuring that the simulations accurately reflect real-world behavior. The results indicate the success of the calibration, facilitating the design and testing of products in a predictive virtual environment. Precise calibration is essential for predicting material behavior in real-world conditions and minimizing the risk of implementation failures.

Phase equilibrium in canonical cubic structure I (sI) and II (sII) and hexagonal (sH) gas hydrate solid solutions

Canonical clathrate or gas hydrates of structure I, II and H are the main interest of engineers and scientists in a variety of technological fields including flow assurance in hydrocarbon pipelines and processing facilities, natural gas recovery from the earth's hydrates, CO2 capture and storage, methane and H2 storage etc. Clathrate hydrate systems exhibit a variety of phase equilibria and the knowledge of the relevant phase diagrams is necessary for the design of relevant processes and facilities. In this work, the various types of canonical hydrate phase equilibria of interest, models of material behaviour for phases encountered in gas hydrate systems and computational methods of phase equilibria are discussed. The term model refers to thermodynamic models for the calculation of fugacities or activity coefficients. The term method refers to hydrate equilibrium computational procedures based on combinations of the hydrate statistical thermodynamics van der Waals and Platteuw (vPW) or its improved versions with various fluid phase thermodynamic models such as equations of state and activity coefficient models. Our discussion and presentation follows a deductive approach to distinguish it from other works that are a collection of all computational methods to calculate hydrate equilibria and which often use the terms method and model interchangeably. Original references are cited as well as the current status and recent advances and challenges are considered. The advent of machine learning techniques for gas hydrate and thermodynamic calculations is also discussed.