Material Parameters Of Model Research Articles

Simulation analysis of cutting process for Inconel718 nickel-based superalloy

As a difficult-to-machine material, Inconel718 nickel-based superalloy is widely used in aerospace, ocean navigation, and large-scale manufacturing of machines. In this paper, based on ABAQUS software, the continuous milling process of Inconel718 is simulated and analyzed, and related issues are discussed, including model establishment, material parameters, and meshing techniques during milling. The simulation results revealed that the heat generated during the milling process increases continuously with the increase in rotational speed. A majority of the generated heat is transferred to the chips and the workpiece, and a minor part is transferred to the tool. During the milling process, the temperature distribution on the cutting tool changes in a gradient, and the temperature of the tool is lower than that of the workpiece. Furthermore, it is observed that the cutting parameters that have the strongest influence on the cutting force and cutting temperature are feed per tooth and spindle speed, respectively. Therefore, in actual processing, speed and feed per tooth can be controlled to get better processing efficiency. Compared to the previous studies, it is concluded that three-dimensional simulation analysis of difficult-to-machine materials can reduce unnecessary wastage of resources and can provide better guidance for actual production and efficient milling.

Laboratory Investigation and Numerical Modelling of Concrete Reinforced with Recycled Steel Fibers.

In the last decades, fiber reinforced concrete have emerged as the possible key to revolutionize civil engineering. Among different types of fibers employed in concrete technology to date, the application of recycled steel fibers produced from end-of-life car tires appears to be a viable approach towards environmentally friendly construction. In this study, we demonstrate the laboratory research and numerical analysis of concrete reinforced with waste steel fibers recovered during the recycling process of end-of-life car tires. Concrete mixes with the following fiber contents: 0.5%, 0.75%, 1.0%, 1.25%, and 1.5% per volume were prepared and then tested in three-point bending conditions. The laboratory investigation revealed highly boosted properties of concrete under flexure. We further performed the finite element method (FEM) analysis of 2D models using Atena software in order to develop a material model allowing the numerical modelling of recycled steel fibers reinforced concrete (RSFRC) behavior. The parameters of RSFRC material model have been modified using the inverse analysis until matching the experimental performance of the material. The results, being in good agreement with the laboratory investigation, have indicated a high potential of RSFRC for real scale construction applications.

Improvement of the Inverse Finite Element Analysis Approach for Tensile and Toughness Predictions by Means of Small Punch Technique

Abstract This paper focuses on the inverse finite element analysis (FEA) to calculate the small punch technique (SPT) tests and the prediction of the tensile and fracture toughness behavior. For the description of the SPT tests via FEA, the hardening rule of Ramberg–Osgood (RO) and the damage model of Gursson–Tvergaard–Needleman (GTN) were used. The inverse FEA optimization process cannot provide a unique solution for the 12 parameters included in the material model. This results from a dependency between some parameters, which leads to the same solution in the optimization. Hence, a novel description of the dependent parameters was developed and implemented within the optimization process. Therefore, an enhanced inverse FEA approach was proposed, which provides a fast converging solution for determination of the material model parameters. Within this study, the forged turbine shaft material EN: 27NiCrMoV15-6 was investigated. For comparison purpose, SPT tests as well as tensile tests and fracture toughness tests were carried out. In the case of the tensile properties, the test and simulation show coincidence in the curve and the characteristic values. For the toughness behavior, the characteristic value of the test was met by the simulation.

Testing the State of Internal Load and Strength of the Facade Mesh Wire Subjected to the Corrugation Process

Abstract The article presents an example of a structural solution of a mesh facade installed on a public building. The types of loads that can affect the structure of such a mesh have been characterized. The course of the wire shaping process used to produce the described mesh was reported. A finite element method (FEM) model was developed to simulate mechanical phenomena occurring during the technological process of crimping stainless-steel wire. Material model parameters have been defined. The developed model was verified in production conditions. Relations between wire-forming loads and tensile limit loads, as well as the distribution of equivalent tensile stress forced by the crimping process and internal stresses after crimping, were determined. The description of the technological process was presented in a form of a graph. The work contains the results of strength tests of wire materials and shaping tools.

Local Stress–Strain Estimation for Tenon Joint Structure under Multiaxial Cyclic Loading at Non-isothermal High Temperature

In this paper, a method based on the improved effective stress concentration factor is proposed to estimate the local stress–strain for tenon joint structure under multiaxial cyclic loading at non-isothermal high temperature. In order to consider the effect of changing temperature on material properties, the impact caused by temperature on the stress–strain response needs to be introduced to the parameters of material constitutive model. So that, each material parameter in viscoplastic constitutive model is expressed as a function of temperature. In addition, the computing method of the effective stress concentration factor is improved so as to solve the problem of the overestimation for local stress–strain of tenon joint structure in the Neuber rule. Moreover, the proposed notch correction method is coupled with the Chaboche unified viscoplastic constitutive model to estimate the local stress–strain of tenon joint structure at non-isothermal high-temperature condition. To verify the reliability of the proposed method, the calculation results are compared with the nonlinear finite element analysis results under various loading paths at non-isothermal high-temperature condition. The results showed that the proposed method can accurately estimate the notch stress and strain under multiaxial thermo-mechanical cyclic loading.

Considering multiple process observables to determine material model parameters for FE-cutting simulations

Analyzing the chip formation process by means of the finite element method (FEM) is an established procedure to understand the cutting process. For a realistic simulation, different input models are required, among which the material model is crucial. To determine the underlying material model parameters, inverse methods have found an increasing acceptance within the last decade. The calculated model parameters exhibit good validity within the domain of investigation, but suffer from their non-uniqueness. To overcome the drawback of the non-uniqueness, the literature suggests either to enlarge the domain of experimental investigations or to use more process observables as validation parameters. This paper presents a novel approach merging both suggestions: a fully automatized procedure in conjunction with the use of multiple process observables is utilized to investigate the non-uniqueness of material model parameters for the domain of cutting simulations. The underlying approach is two-fold: Firstly, the accuracy of the evaluated process observables from FE simulations is enhanced by establishing an automatized routine. Secondly, the number of process observables that are considered in the inverse approach is increased. For this purpose, the cutting force, cutting normal force, chip temperature, chip thickness, and chip radius are taken into account. It was shown that multiple parameter sets of the material model can result in almost identical simulation results in terms of the simulated process observables and the local material loads.

Fiber Bragg Sensors Embedded in Cast Aluminum Parts: Axial Strain and Temperature Response.

In this study, the response of fiber Bragg gratings (FBGs) embedded in cast aluminum parts under thermal and mechanical load were investigated. Several types of FBGs in different types of fibers were used in order to verify general applicability. To monitor a temperature-induced strain, an embedded regenerated FBG (RFBG) in a cast part was placed in a climatic chamber and heated up to 120 within several cycles. The results show good agreement with a theoretical model, which consists of a shrink-fit model and temperature-dependent material parameters. Several cast parts with different types of FBGs were machined into tensile test specimens and tensile tests were executed. For the tensile tests, a cyclic procedure was chosen, which allowed us to distinguish between the elastic and plastic deformation of the specimen. An analytical model, which described the elastic part of the tensile test, was introduced and showed good agreement with the measurements. Embedded FBGs - integrated during the casting process - showed under all mechanical and thermal load conditions no hysteresis, a reproducible sensor response, and a high reliable operation, which is very important to create metallic smart structures and packaged fiber optic sensors for harsh environments.

Viscoelastic model to capture residual stresses in heat cured dissimilar adhesive bonded joints

The thermal loading during the curing process of an adhesive-bonded joint induces residual stresses in the joint, thereby affecting its performance. The problem becomes worse in the case of a multi-material joint involving varying coefficients of thermal expansion (CTE) for different parts. A novel approach was developed to model the properties of automotive grade structural adhesives during the heat curing process. The material model was divided into two components: curing kinetics model and viscoelastic mechanical model. The models were calibrated using experimental data from Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) tests performed on an epoxy-based single-component adhesive. The calibrated material model parameters were fed into a finite element simulation and the prediction results were compared to a unique set of experiments utilizing two substrate combinations of adhesive-bonded single lap shear joints. An excellent agreement between the simulated and experimental results (displacement across the bond, force applied by the adhesive) was achieved. The modeling results give a better understanding of the residual stresses and agree with the experimental trend on the effect of bondline thickness on the joint.

Integrated Prognosis for Wind Turbine Gearbox Condition-Based Maintenance Considering Time-Varying Load and Crack Initiation Time Uncertainty

Maintenance management in wind energy industry has great impact on the overall wind power cost. Maintenance services are either supported by wind turbine manufacturers within warranty period, or managed by wind farm owners. With condition-based maintenance (CBM) strategy, maintenance activities are scheduled based on the predicted health conditions of wind turbine components, and accurate prognostics methods are critical for effective CBM. The reported studies on integrated health prognostics considered the uncertainty in crack initiation time (CIT) uncertainty, but did not incorporate time-varying loading conditions, which could also have a significant impact on future health condition and remaining useful life (RUL) prediction. Constant loads were generally used to approximate the actual time-varying loading conditions. In this paper, an integrated prognostics method is proposed for wind turbine gearboxes considering both time-varying loading conditions and CIT uncertainty. As new condition monitoring observations are available, the distributions of both material model parameter and CIT are updated via Bayesian inference, and the failure time prediction is updated accordingly. An example is provided to demonstrate that the proposed time-varying load approach presents more benefits considering the uncertainty of CIT, with significant accuracy improvement comparing to the constant-load approach.

A Rate-dependent Continuum Damage Model for Dynamic Shear Debonding of CFRP-concrete Interface

Dynamic shear debonding behaviour in fibre reinforced polymer (FRP) strengthened concrete structures has been studied by some researchers through experiments and finite element (FE) simulations. However, there is still a lack of a continuum damage model to simulate dynamic debonding behaviour of CFRP-concrete interface using a method derived from nonlinear fracture mechanics (NLFM). To gain deeper insight into the dynamic fracture mechanics of carbon fibre reinforced polymer (CFRP)-concrete interface, a novel continuum damage model was proposed in this paper. Model analyses and regression test data were used to formulate the relationship between model coefficients and material parameters of tested specimens in literature. It was found that the dynamic enhancing effect on interfacial bond properties became more significant when a specimen has a larger CFRP load capacity or a lower concrete load capacity. The proposed damage model was verified through comparing numerical predictions of load-displacement curve and CFRP strain distribution along the bond length with published test results. Finally, based on a comparison with experimental study of specimens using basalt FRP and glass FRP, the proposed model was also found to be applicable to different types of FRP.

On the Application of the Particle Swarm Optimization to the Inverse Determination of Material Model Parameters for Cutting Simulations

The manufacturing industry is confronted with increasing demands for digitalization. To realize a digital twin of the cutting process, an increase of the model reliability of the virtual representation becomes necessary. Thereby, different models are required to represent the experimental behavior of the workpiece material or frictional interactions. One of the most utilized material models is the Johnson–Cook material model. The material model parameters are determined either by conventional or by non-conventional material tests, or inversely from the cutting process. However, the inverse parameter determination, where the model parameters are iteratively modified until a sufficient agreement between experimental and numerical results is reached, is not robust and requires a high number of iterations. In this paper, an approach for the inverse determination of material model parameters based on the Particle Swarm Optimization (PSO) is presented. The approach was investigated by the inverse re-identification of an initial parameter set. The conducted investigations showed that a material model parameter set can be determined within a small number of iterations. Thereby, the determined material model parameters resulted in deviations of approximately 1% in comparison to their target values. It was shown that the PSO is suitable for the inverse material parameter determination from cutting simulations.

On Attempting to Create a Virtual Laboratory for Application-Oriented Microstructural Optimization of Multi-Phase Materials

Physics-based and phenomenological crystal plasticity numerical simulations provide an opportunity to develop microstructurally informed models for multi-phase material. The Düsseldorf Advanced Material Simulation Kit (DAMASK) has been developed as a flexible tool for modeling and studying the several deformation mechanisms of such materials at the microscopic and macroscopic scales. In the recent past, several methodologies and techniques were developed for obtaining or constructing microstructural details and calibrating the physics-based model parameters for single-phase and multi-phase materials. Combining and standardizing the devised methods with an appropriate database can help establish a virtual laboratory to analyze the effect of microstructural attributes on the mechanical behavior of multi-phase materials. This article deals with the comprehensive background of the developed techniques and methods for the multi-phase materials class by the current research group. The combinations of different experimental and numerical techniques to validate results are explained along with the advantages and limitations. The ideas of combining the different available tools and the associated challenges are discussed. The article presents some recent work related to the phase parameters identification of the multi-phase materials and detailed insight into the obtained results.

Dynamic responses of highway bridge subjected to heavy truck impact

This study aims to numerically analyze the dynamic responses and damage/failure of bridge substructure during the vehicle-pier collisions, by employing the refined finite element (FE) models of a heavy truck and a simply-supported prototype highway bridge. Firstly, the adopted numerical algorithm and material model parameters to capture both the flexural and shear failures are validated through the simulations of two lateral flexible impactor crash tests. Then, the full-scale FE model of a typical four-span reinforced concrete (RC) bridge with two-pier bents is established, and a high-fidelity heavy truck FE model established previously is improved and further certified by comparisons with the eccentric and aligned full-scale crash test data. Furthermore, a series of numerical simulations are conducted to examine the heavy truck collision process and analyze the failure modes of bridge structure, as well as the parametric influences, including truck mass, impact velocity, and impact angle. Finally, the linear relationships of initial engine momentum, maximal vehicular impact force, 25-ms moving average, sectional force, and lateral displacement are proposed. It indicates that, (i) compared with the *MAT_CONCRETE_DAMAGE_REL3 and *MAT_WINFRITH_CONCRETE, *MAT_ CSCM_CONCRETE can well depict the flexural and shear failure modes of the pier subjected to heavy truck impact in actual accidents; (ii) the ultimate failure of the impacted pier is mainly caused by the impact of the cargo rather than the engine in the heavy truck; (iii) the impact angle significantly amplifies the possibilities of the T-girder falling off and the failure of bent cap, increasing the potential risk of overall collapse of the bridge superstructure.

Shear wave speeds in nearly-incompressible fibrous materials with two fiber families.

An analytical and numerical investigation of shear wave behavior in nearly-incompressible soft materials with two fiber families was performed, focusing on the effects of material parameters and imposed pre-deformations on wave speed. This theoretical study is motivated by the emerging ability to image shear waves in soft biological tissues by magnetic resonance elastography (MRE). In MRE, the relationships between wave behavior and mechanical properties can be used to characterize tissue properties non-invasively. We demonstrate these principles in two material models, each with two fiber families. One model is a nearly-incompressible linear elastic model that exhibits both shear and tensile anisotropy; the other is a two-fiber-family version of the widely-used Holzapfel-Gasser-Ogden (HGO) model, which is nonlinear. Shear waves can be used to probe nonlinear material behavior using infinitesimal dynamic deformations superimposed on larger, quasi-static "pre-deformations." In this study, closed-form expressions for shear wave speeds in the HGO model are obtained in terms of the model parameters and imposed pre-deformations. Analytical expressions for wave speeds are confirmed by finite element simulations of shear waves with various polarizations and propagation directions. These studies support the feasibility of estimating the parameters of an HGO material model noninvasively from measured shear wave speeds.

Bayesian parameter and joint probability distribution estimation for a hysteretic constitutive model of reinforcing steel

With the structural design paradigm shift since the early 2000′s from the traditional approach to performance-based design (PBD), there has been a growing need for reliable nonlinear finite element (FE) models that can accurately predict the response of structures when subjected to extreme loads, such as earthquakes. In the case of reinforced concrete (RC) structures, a proper representation of the hysteretic nonlinear behavior of reinforcing steel becomes crucial in order to carry out nonlinear time history analyses. The Giuffrè-Menegotto-Pinto (GMP) uniaxial steel constitutive law has been widely used by researchers and practitioners to model reinforcing steel bars. Despite the widespread in its implementation, a limited number of studies have proposed well-calibrated parameter values for this model. In addition, low identifiability of its governing parameters and the high cost of generating reliable experimental data have prevented a thorough probabilistic characterization of the GMP model parameters. Usually, only default parameter values from the early development of the model tend to be used. This paper uses experimental data from cyclic tests conducted on 36 reinforcing steel coupons manufactured in accordance to ASTM A615 and A706 Grade 60 reinforcing steel and proposes a joint probability density function (PDF) for the most influential parameters of the GMP material model. First, a local sensitivity analysis (LSA) is conducted to provide insight into the influence of each parameter in the model response. Also, global sensitivity analysis (GSA) is used to have a deep understanding of the composition of the variability in the model response due to parameter uncertainty and the level of interactions among parameters. The Bayesian approach is combined with the information obtained from GSA and LSA as input, to estimate model parameters and quantify the estimation uncertainties and propagate them to the material stress response. Uncertainty in model predictions obtained with the proposed PDF is assessed, and the impact of considering parameter correlations on the material response is investigated.

Parameters Identification of the Anand Material Model for 3D Printed Structures.

Currently, there is an increasing use of machine parts manufactured using 3D printing technology. For the numerical prediction of the behavior of such printed parts, it is necessary to choose a suitable material model and the corresponding material parameters. This paper focuses on the determination of material parameters of the Anand material model for acrylonitrile butadiene styrene (ABS-M30) material. Material parameters were determined using the genetic algorithm (GA) method using finite element method (FEM) calculations. The FEM simulations were subsequently adjusted to experimental tests carried out to achieve the possible best agreement. Several experimental tensile and indentation tests were performed. The tests were set up in such a way that the relaxation and creep behaviors were at least partially captured. Experimental tests were performed at temperatures of 23 °C, 44 °C, 60 °C, and 80 °C. The results obtained suggest that the Anand material model can also be used for ABS-M30 plastic material, but only if the goal is not to detect anisotropic behavior. Future work will focus on the search for a suitable material model that would be able to capture the anisotropic behavior of printed plastic materials.

A fast calibration approach of modified Chaboche hardening rule for low yield point steel, mild steel and high strength steels

Chaboche model has gained prominent utilization in numerical simulation on cyclic behaviors of metal structure. However, the calibration of its material parameter may produce considerable cost. A simplified calibration way is of great importance to ease its application. To this end, a re-evaluation on chaboche model material parameters and simulated elastic-plastic laws was conducted regarding various steel grades. Futhermore, the characterisitcs of isotropic softening was coupled with the present model hardening rule. The kinematic rule was correlated with cumulative plastic strain. The modified model was then calibrated and validated base upon the coupon test result on 41 batches of steels, whose yield stress ranges from 100 MPa to 890 MPa. The calibrated material parameter were then correlated with corresponding monotonic mechanical properties. Accordingly, a simplified calibration procedure, based upon which the material parameters of modifed Chaboche model can be fastly estimated by yield strength and yield ratio, was constructed. As for low yield point steels, mild steels and high strength steels, this calibration method can ease the calibration of modified Chaboche model considerably.

FEM Simulation of High Speed Impact Behaviour of Additively Manufactured AlSi10Mg Alloy

The present work investigates impact behaviour of additively manufactured AlSi10Mg alloy and ballistic limit of projectiles using FEM simulations. Tensile tests, dynamic tests and elevated temperature tensile tests simulations were performed on smooth and notched specimens to calculate Johnson–Cook material and damage model parameters, which are subsequenty given as inputs for impact simulation. The relationship between residual velocity versus initial projectile velocity is expressed using Jonas–Lambert’s model for calculating ballistic limit. The effects of projectile velocity, its shape, thickness and material property of AlSi10Mg on ballistic limit were thoroughly investigated. C3D8R elements are used to discretize the target plate and mesh transition zone was created in impact region. Johnson–Cook elasto-viscoplastic model was employed to study the ballistic resistance behaviour of AlSi10Mg alloy. Fracture energy value of 43.6 kN/m for AlSi10Mg alloy is used to initiate the damage in target plate. All FE simulations were performed by using ABAQUS/Explicit. It is observed that ballistic impact on 3D printed AlSi10Mg has shown plugging and petaling failure when hemispherical projectile was used while plugging failure in the case of blunt projectiles. The ballistic limit of hemispherical projectiles is found to be higher (311 m/s, 400 m/s) compared to the blunt projectiles (216.5 m/s, 245 m/s). The impact velocity to completely penerate 6 mm thick target plate is relatively higher as compared to 3 mm thick target plate for both projectiles.

Discrete element model calibration for industrial raw material simulations

The use of computational fluid dynamics in continuous operation industries have become more prominent in recent times. Proposed system improvements through geometric changes or control strategies can be evaluated within a relatively shorter timeframe. Applications for discrete element methods (DEMs) in real life simulations, however, require validated material-calibration-methods. In this paper, the V-model methodology in combination with direct and bulk calibration approaches were followed to determine material model parameters, to simulate real life occurrences. For the bulk calibration approach a test rig with a containment hopper, deflection plate and settling zone was used. Screened material drains from the hopper, interacts with the deflection plate, and then settles at the material angle of repose. A high-speed camera captured material interaction with the rig, where footage was used during simulation validation. The direct measuring approach was used to determine particle size, shape and density, while confirming friction and restitution coefficients determined in the bulk calibration method. The test was repeated and validated for various geometrical changes. Three categories of validation were established, namely particle speed assessment, -trajectory assessment and -plate interaction assessment. In conclusion, the combination of direct and bulk calibration approaches was significant in calibrating the required material model parameters.

Feasibility Study of a Combined Tension-Torsion Hopkinson Bar

The increasing interest to improve the description of the plastic behavior and the fracture prediction for ductile materials under complex loading conditions conducted the researchers to overcome the J2 plasticity theory. To do this more sophisticated plasticity model base on ductile damage have been implemented. Material model parameters must be identified by means of proper testing and calibration procedures requiring different loading conditions. Different types of tests must be performed, imposing multiaxial stress paths to the specimens. Tensile tests on smooth and round notched bars, plane strain tests, torsion tests, compression and combined tension–torsion tests on hollow and solid cylindrical bars must be executed. While multiple works are present in literature for model assessment and validation in quasi-static conditions, nothing can be found at high strain rate in biaxial conditions (tension-torsion). Biaxial tests in dynamic conditions are very difficult to carry out especially if you are interested to register the entire story of stress and strain. In this work, analytical and numerical study to evaluate the feasibility to carry out dynamic tension, dynamic torsion, dynamic torsion-static tension/compression and dynamic tension–dynamic torsion tests is discussed. The tests will be performed using a properly designed Split Hopkinson Bar.