Evolutive Laws and Constitutive Relations in Nonlocal Viscoplasticity

2012 ◽  
Vol 152-154 ◽  
pp. 990-996 ◽  
Author(s):  
Fabio de Angelis
Keyword(s):  
Constitutive Relations ◽  
Material Model ◽  
Standard Material ◽  
Viscoplastic Model ◽  
Proposed Model

In the present work the evolutive laws and the constitutive relations for a model of nonlocal viscoplasticity are analyzed. Nonlocal dissipative variables and suitable regularization operators are adopted. The proposed model is developed within the framework of the generalized standard material model. Suitable forms of the elastic and dissipative viscoplastic potentials are defined and the associated constitutive relations are specialized. The evolutive laws for the proposed nonlocal viscoplastic model are presented in a general form which can be suitably specialized in order to include different models of nonlocal viscoplasticity.

A Consistent Formulation of Constitutive Relations for a Model of Nonlocal Viscoplasticity

2012 ◽  
Vol 217-219 ◽  
pp. 2367-2372 ◽  
Author(s):  
Fabio de Angelis ◽  
Donato Cancellara
Keyword(s):  
Constitutive Relations ◽  
Standard Material ◽  
Proposed Model ◽  
Hardening Rules ◽  
Consistent Formulation

Constitutive relations are presented for a model of nonlocal viscoplasticity within a variationally consistent suitable setting. The appropriate elastic and dissipative potentials are introduced within a generalized standard material framework. A formulation of variationally consistent constitutive relations is accordingly presented for a model of nonlocal viscoplasticity. The evolutive equations are illustrated for the proposed model in a general form which is able to include different models of nonlocal viscoplasticity and different hardening rules.

scholarly journals Flexural behavior of composite structural insulated panels with magnesium oxide board facings

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
Łukasz Smakosz ◽  
Ireneusz Kreja ◽  
Zbigniew Pozorski
Keyword(s):  
Magnesium Oxide ◽  
Material Model ◽  
Expanded Polystyrene ◽  
Flexural Behavior ◽  
Joint Analysis ◽  
Model Parameters ◽  
Fe Model ◽  
Computational Results ◽  
Four Point Bending ◽  
Proposed Model

Abstract The current report is devoted to the flexural analysis of a composite structural insulated panel (CSIP) with magnesium oxide board facings and expanded polystyrene (EPS) core, that was recently introduced to the building industry. An advanced nonlinear FE model was created in the ABAQUS environment, able to simulate the CSIP’s flexural behavior in great detail. An original custom code procedure was developed, which allowed to include material bimodularity to significantly improve the accuracy of computational results and failure mode predictions. Material model parameters describing the nonlinear range were identified in a joint analysis of laboratory tests and their numerical simulations performed on CSIP beams of three different lengths subjected to three- and four-point bending. The model was validated by confronting computational results with experimental results for natural scale panels; a good correlation between the two results proved that the proposed model could effectively support the CSIP design process.

scholarly journals Identification of Fractional Damping Parameters in Structural Dynamics Using Polynomial Chaos Expansion

2021 ◽  
Vol 2 (4) ◽  
pp. 956-975
Author(s):  
Marcel S. Prem ◽  
Michael Klanner ◽  
Katrin Ellermann
Keyword(s):  
Polynomial Chaos ◽  
Constitutive Relations ◽  
Computational Cost ◽  
Material Model ◽  
Polynomial Chaos Expansion ◽  
Computational Technique ◽  
Chaos Expansion ◽  
Material Damping ◽  
Fractional Damping ◽  
Assembly Technique

In order to analyze the dynamics of a structural problem accurately, a precise model of the structure, including an appropriate material description, is required. An important step within the modeling process is the correct determination of the model input parameters, e.g., loading conditions or material parameters. An accurate description of the damping characteristics is a complicated task, since many different effects have to be considered. An efficient approach to model the material damping is the introduction of fractional derivatives in the constitutive relations of the material, since only a small number of parameters is required to represent the real damping behavior. In this paper, a novel method to determine the damping parameters of viscoelastic materials described by the so-called fractional Zener material model is proposed. The damping parameters are estimated by matching the Frequency Response Functions (FRF) of a virtual model, describing a beam-like structure, with experimental vibration data. Since this process is generally time-consuming, a surrogate modeling technique, named Polynomial Chaos Expansion (PCE), is combined with a semi-analytical computational technique, called the Numerical Assembly Technique (NAT), to reduce the computational cost. The presented approach is applied to an artificial material with well defined parameters to show the accuracy and efficiency of the method. Additionally, vibration measurements are used to estimate the damping parameters of an aluminium rotor with low material damping, which can also be described by the fractional damping model.

scholarly journals A Dynamic Cavity Expansion Model for Rigid Projectile Penetration into Concrete considering the Compressibility and Nonlinear Constitutive Relations

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Fei Gao ◽  
Zhen Wang ◽  
Zhu Wen ◽  
Yuguo Ji
Keyword(s):  
Yield Criterion ◽  
Constitutive Relations ◽  
Cavity Expansion ◽  
Depth Of Penetration ◽  
Proposed Model ◽  
Rigid Projectile ◽  
Calculation Results ◽  
Expansion Model ◽  
Constitutive Parameters ◽  
Nonlinear Constitutive Relations

The P-α equation of state (EOS) and a nonlinear yield criterion are utilized to characterize the dynamic constitutive behavior of concrete targets subjected to projectile normal penetration. A dynamic cavity expansion model considering the compressibility and nonlinear constitutive relations for concrete material is developed. Then, a theoretical model to calculate the depth of penetration (DOP) for rigid projectile is established. Furthermore, the proposed model is validated based on the available test data as well as the calculation results by the linear compressible EOS and linear yield criterion. This study shows that the proposed model derived using the P-α EOS and nonlinear yield criterion can effectively reflect the plastic mechanical properties of concrete and is also suitable for predicting the DOP of concrete targets. In addition, the influence law of concrete constitutive parameters such as the cohesion strength, shear strength, internal friction coefficient, and elastic limit pressure on the DOP is revealed.

On Identification of Material Models When Nonrepeatability of Test Data is Present: Application to Textile Composites

2004 ◽  
Vol 126 (4) ◽  
pp. 443-449 ◽  
Author(s):  
Abbas S. Milani ◽  
James A. Nemes
Keyword(s):  
Test Data ◽  
Standard Form ◽  
Model Identification ◽  
Material Model ◽  
Textile Composites ◽  
Nonlinear Material ◽  
Standard Material ◽  
Identification Process ◽  
Qualitative And Quantitative ◽  
Space Transformation

Engineering test data occasionally violate assumptions underlying standard material model identification. Consequently, one has to apply appropriate remedies with respect to each violation to enhance the reliability of identified material parameters. This paper generalizes the use of the signal-to-noise weighting scheme when heteroscedasticity of test data are suspected. Different mathematical and practical aspects of the approach are discussed. Additionally, the ensuing weighted identification process is simplified to an equivalent standard form by means of a space transformation. Finally, the approach is applied to the identification of a nonlinear material model for textile composites, on both qualitative and quantitative levels.

Physics-Based Modeling for Lap-Type Joints Based on the Iwan Model

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Wanglong Zhan ◽  
Ping Huang
Keyword(s):  
Distribution Function ◽  
Constitutive Relations ◽  
Hysteresis Loops ◽  
Experimental Results ◽  
Bolted Joints ◽  
Height Distribution ◽  
Proposed Model ◽  
Contact Situation ◽  
Rough Surface Contact ◽  
Nonlinear Constitutive Relation

This study proposed a physics-based heuristic modeling for the nonlinear constitutive relation of bolted joints based on the Iwan model accompanying with the rough surface contact theory. The approach led to an Iwan distribution function which possesses the tribology-related features of the contact interface. In particular, the break-free force distribution function of the Jenkins elements could be expressed in terms of height distribution of surface asperities. The model considered the contribution of elastically, elasto-plastically as well as plastically deformed asperities to the total tangential loads. Following this, constitutive relations for lap-type bolted joints and the corresponding backbone curves, hysteresis loops, and energy dissipation per cycle were obtained. A model application was implemented and the results were compared with the published experimental results. The proposed model agrees very well with the experimental results when the contact parameters met the actual contact situation. The obtained results indicated that the model can be used to study the tangential behaviors of rough surfaces.

Implosion Analysis of Concrete Cylindrical Vessels

1979 ◽  
Vol 101 (1) ◽  
pp. 98-102
Author(s):  
H. Suzuki ◽  
W. F. Chen ◽  
T. Y. Chang
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Fracture Behavior ◽  
Constitutive Relations ◽  
Analysis Procedure ◽  
Material Behavior ◽  
Ultimate State ◽  
Element Analysis ◽  
Proposed Model ◽  
Effect Of Hydrostatic Pressure

Concrete constitutive relations which can simulate the overall material behavior up to and including its ultimate state under general triaxial loading conditions have been developed. The proposed constitutive relations include: 1) plastic deformation considering the effect of hydrostatic pressure, 2) a dual criterion predicting the fracture of concrete in terms of either stresses or strains, and 3) post-fracture behavior of concrete. Corresponding to the constitutive model, a finite element analysis procedure has also been utilized. Based on the proposed model, implosion pressures and load-deformation responses of several concrete vessels were obtained. The numerical results correlate quite well with the experimental data when the dual criterion was used.

scholarly journals Nonlinear Material Model for Quasi-Unidirectional Woven Composite Accounting for Viscoelastic, Viscous Deformation, and Stiffness Reduction

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 903 ◽  
Author(s):  
Zhanyu Zhai ◽  
Bingyan Jiang ◽  
Dietmar Drummer
Keyword(s):  
Material Model ◽  
Tensile Tests ◽  
Experimental Results ◽  
Nonlinear Material ◽  
Weibull Function ◽  
Viscous Deformation ◽  
Stiffness Reduction ◽  
Viscoelastic Strain ◽  
Proposed Model ◽  
The Individual

To clarify the individual contribution of viscoelastic and viscous deformation to the global nonlinear response of composites, multilevel cyclic loading-unloading recovery tensile tests were carried out. The experimental results show that there is a linear relationship between the viscous strain and viscoelastic strain of composites, regardless of the off-axis angle or loading stress level. On the basis of experimental results, a coupled damage-plasticity constitutive model was proposed. In this model, the plasticity theory was adopted to assess the evolution of viscous strains. The viscoelastic strain was represented as a linear function of viscous strains. Moreover, the Weibull function of the effective stress was introduced to evaluate the damage variables in terms of stiffness reduction. The tensile stress-strain curves, predicted by the proposed model, showed a good agreement with experimental results.

scholarly journals A Simplified Approach for the Hydro-Forming Process of Bi-Metallic Composite Pipe

2017 ◽  
Vol 62 (2) ◽  
pp. 879-883 ◽  
Author(s):  
M. Zheng ◽  
H. Gao ◽  
H. Teng ◽  
J. Hu ◽  
Z. Tian ◽  
...  
Keyword(s):  
Residual Stress ◽  
Plastic Material ◽  
Material Model ◽  
Forming Process ◽  
Simplified Approach ◽  
Metallic Composite ◽  
Perfectly Plastic ◽  
Proposed Model ◽  
Composite Pipe ◽  
Elastic Perfectly Plastic

AbstractIn this article, it aims to propose effective approaches for hydro-forming process of bi-metallic composite pipe by assuming plane strain and elastic-perfectly plastic material model. It derives expressions for predicting hydro-forming pressure and residual stress of the forming process of bi-metallic composite pipe. Test data from available experiments is employed to check the model and formulas. It shows the reliability of the proposed model and formulas impersonally.

scholarly journals NUMERICAL MODELLING OF BIRD STRIKE ON A ROTATING ENGINE BLADES BASED ON VARIATIONS OF POROSITY DENSITY

2022 ◽  
Vol 23 (1) ◽  
pp. 412-423
Author(s):  
Sharis-Shazzali Shahimi ◽  
Nur Azam Abdullah ◽  
Ameen Topa ◽  
Meftah Hrairi ◽  
Ahmad Faris Ismail
Keyword(s):  
Numerical Modelling ◽  
Structural Integrity ◽  
Constitutive Relations ◽  
Material Model ◽  
Initial Stresses ◽  
Model Parameters ◽  
Bird Strike ◽  
Elastic Plastic ◽  
Engine Blade ◽  
The Impact

A numerical investigation is conducted on a rotating engine blade subjected to a bird strike impact. The bird strike is numerically modelled as a cylindrical gelatine with hemispherical ends to simulate impact on a rotating engine blade. Numerical modelling of a rotating engine blade has shown that bird strikes can severely damage an engine blade, especially as the engine blade rotates, as the rotation causes initial stresses on the root of the engine blade. This paper presents a numerical modelling of the engine blades subjected to bird strike with porosity implemented on the engine blades to investigate further damage assessment due to this porosity effect. As porosity influences the decibel levels on a propeller blade or engine blade, the damage due to bird strikes can investigate the compromise this effect has on the structural integrity of the engine blades. This paper utilizes a bird strike simulation through an LS-Dyna Pre-post software. The numerical constitutive relations are keyed into the keyword manager where the bird’s SPH density, a 10 ms simulation time, and bird velocity of 100 m/s are all set. The blade rotates counter-clockwise at 200 rad/s with a tetrahedron mesh. The porous regions or voids along the blade are featured as 5 mm diameter voids, each spaced 5 mm apart. The bird is modelled as an Elastic-Plastic-Hydrodynamic material model to analyze the bird’s fluid behavior through a polynomial equation of state. To simulate the fluid structure interaction, the blade is modelled with Johnson-Cook Material model parameters of aluminium where the damage of the impact can be observed. The observations presented are compared to previous study of a bird strike impact on non-porous engine blades. ABSTRAK: Penyelidikan berangka telah dijalankan ke atas bilah enjin berputar tertakluk kepada impak pelanggaran burung. Pelanggaran burung tersebut telah dimodelkan secara berangka sebagai silinder gelatin dengan hujungnya berbentuk hemisfera demi mensimulasikan impaknya ke atas bilah enjin yang berputar. Pemodelan berangka bilah-bilah enjin yang berputar tersebut menunjukkan bahawa pelanggaran burung mampu menyebabkan kerosakan teruk terhadap bilah enjin terutamanya apabila bilah enjin sedang berputar oleh sebab putaran menghasilkan tekanan asal di pangkal bilah enjin. Kajian ini mengetengahkan pemodelan berangka ke atas bilah-bilah enjin tertakluk kepada pelanggaran burung terhadap bilah-bilah enjin yg mempunyai keliangan demi menyelidik dan menilai kerosakan kesan daripada keliangan tersebut. Keliangan juga mempengaruhi tahap-tahap desibel ke atas bilah kipas ataupun bilah enjin, kerosakan hasil serangan burung boleh menterjemah tahap ketahanan struktur integriti bagi bilah-bilah enjin tersebut. Penyelidikan ini mengguna pakai perisian “LS-Dyna Pre-post” untuk simulasi pelanggaran burung. Hubungan konstitutif berangka telah dimasukkan sebagai kata kunci di mana ketumpatan SPH burung, masa simulasi 10ms, dan halaju burung ditetapkan kepada 100 m/s. Bilah tersebut berputar pada 200 rad/s arah lawan jam dengan jejaring tetrahedron. Kawasan berliang atau kosong di sepanjang bilah ditetapkan diameternya kepada 5 mm, dan dijarakkan 5 mm di antara satu sama lain. Burung pula dimodelkan sebagai material “Elastic-Plastic-Hydrodynamic” untuk mengkaji sifat bendalir burung melalui persamaan polinomial. Demi mensimulasi interaksi struktur bendalir, bilah tersebut dimodelkan sebagai parameter aluminium material “Johnson Cook” di mana kerosakan daripada impak tersebut dapat diteliti. Penelitian-penelitian tersebut dibandingkan dengan kajian terdahulu ke atas serangan burung terhadap bilah-bilah enjin tidak berliang.

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