scholarly journals Modelling of High Velocity Impact on Concrete Structures Using a Rate-Dependent Plastic-Damage Microplane Approach at Finite Strains

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5165
Author(s):  
Bobby Rio Indriyantho ◽  
Imadeddin Zreid ◽  
Robert Fleischhauer ◽  
Michael Kaliske
Keyword(s):  
Yield Function ◽  
Nonlinear Behaviour ◽  
Rate Dependency ◽  
Microplane Model ◽  
Rate Dependent ◽  
Plastic Damage ◽  
Proposed Model ◽  
Concrete Materials ◽  
Element Erosion ◽  
Gradient Enhancement

Concrete is known as a quasi-brittle material and the microplane model has been proven to be a powerful method to describe its constitutive features. For some dynamic cases, however, numerous microplane models used successfully at small strains are not sufficient to predict the nonlinear behaviour of damaged concrete due to large deformations. In this contribution at hand, a combined plasticity-damage microplane model extended to the finite strain framework is formulated and regularised using implicit gradient enhancement to achieve mesh insensitivity and to obtain more stable finite element solutions. A modified smooth three surface Drucker–Prager yield function with caps is introduced within the compression-tension split. Moreover, a viscoplastic consistency formulation is implemented to deliver rate dependency at dynamic cases. In case of penetration into concrete materials, the proposed model is equipped with an element erosion procedure to yield a better approximation of crack patterns. Numerical examples on impact cases are performed to challenge the capability of the newly proposed model to existing experimental data.

scholarly journals A Coupled Plastic Damage Model for Concrete considering the Effect of Damage on Plastic Flow

2015 ◽  
Vol 2015 ◽  
pp. 1-13
Author(s):  
Feng Zhou ◽  
Guangxu Cheng
Keyword(s):  
Damage Model ◽  
Compressive Loading ◽  
Plain Concrete ◽  
Yield Function ◽  
Reduction Factor ◽  
Loading History ◽  
Plastic Yield ◽  
Plastic Damage ◽  
Compliance Tensor ◽  
Proposed Model

A coupled plastic damage model with two damage scalars is proposed to describe the nonlinear features of concrete. The constitutive formulations are developed by assuming that damage can be represented effectively in the material compliance tensor. Damage evolution law and plastic damage coupling are described using the framework of irreversible thermodynamics. The plasticity part is developed without using the effective stress concept. A plastic yield function based on the true stress is adopted with two hardening functions, one for tensile loading history and the other for compressive loading history. To couple the damage to the plasticity, the damage parameters are introduced into the plastic yield function by considering a reduction of the plastic hardening rate. The specific reduction factor is then deduced from the compliance tensor of the damaged material. Finally, the proposed model is applied to plain concrete. Comparison between the experimental data and the numerical simulations shows that the proposed model is able to describe the main features of the mechanical performances observed in concrete material under uniaxial, biaxial, and cyclic loadings.

STOCHASTIC VISCOUS-DAMAGE CONSTITUTIVE MODEL FOR CONCRETE

2013 ◽  
Vol 07 (03) ◽  
pp. 1350027
Author(s):  
JIE LI ◽  
QIAOPING HUANG
Keyword(s):  
Damage Model ◽  
Damage Mechanism ◽  
Failure Behavior ◽  
Strain Rates ◽  
Rate Dependency ◽  
Rate Dependent ◽  
Proposed Model ◽  
Model Predictions ◽  
Damage Constitutive Model ◽  
Stochastic Damage

A new rate-dependent stochastic damage model for the dynamic modeling of concrete is presented in the paper. This model is formulated on the basis of the stochastic damage model, from which, the static stochastic evolution of damage is strictly derived. Then, rate dependency of concrete is included by means of viscous-damage mechanism. The model predictions are tested against experimental results on concrete specimens that cover different strain rates. The results demonstrate the proposed model may predict dynamic failure behavior of concrete quite well.

Modeling the Rate Dependent Hysteretic Dynamics of Magnetostrictive Transducers

2014 ◽  
Vol 529 ◽  
pp. 312-316
Author(s):  
Xiu Quan Du ◽  
Lin Xiang Wang ◽  
Zhi Feng Tang ◽  
Fu Zai Lv
Keyword(s):  
Numerical Experiments ◽  
Hysteresis Loops ◽  
Phenomenological Theory ◽  
Rate Dependency ◽  
Differential Model ◽  
One Dimensional ◽  
Rate Dependent ◽  
Proposed Model ◽  
Parameter Values ◽  
Magnetostrictive Transducer

In the current paper, the rate dependent hysteretic dynamics of a magnetostrictive transducer is investigated by using a coupled nonlinear macroscopic differential model. The transducer is modeled as a one-dimensional magnetostrictive structure based on the Landau phenomenological theory of phase transition. The hysteresis loops and butterfly-shaped behaviors in the magnetic and mechanical fields are both successfully modeled with estimated model parameter values. The capability of the proposed model for capturing the driving rate dependency is illustrated by numerical experiments.

scholarly journals Heart Rate Dependency and Inter-Lead Variability of the T Peak – T End Intervals

2020 ◽  
Vol 11 ◽  
Author(s):  
Irena Andršová ◽  
Katerina Hnatkova ◽  
Martina Šišáková ◽  
Ondřej Toman ◽  
Peter Smetana ◽  
...  
Keyword(s):  
Heart Rate ◽  
Three Dimensional ◽  
Rate Dependency ◽  
Rate Dependent ◽  
Heart Rate Correction ◽  
Ecg Leads ◽  
Relationship Of ◽  
The Relationship ◽  
Vector Magnitude

The electrocardiographic (ECG) assessment of the T peak–T end (Tpe) intervals has been used in many clinical studies, but several related physiological aspects have not been reported. Specifically, the sources of the Tpe differences between different ECG leads have not been systematically researched, the relationship of Tpe duration to underlying heart rate has not been firmly established, and little is known about the mutual correspondence of Tpe intervals measured in different ECG leads. This study evaluated 796,620 10-s 12-lead ECGs obtained from long-term Holters recorded in 639 healthy subjects (311 female) aged 33.8 ± 9.4 years. For each ECG, transformation to orthogonal XYZ lead was used to measure Tpe in the orthogonal vector magnitude (used as a reference for lead-to-lead comparisons) and to construct a three-dimensional T wave loop. The loop roundness was expressed by a ratio between its circumference and length. These ratios were significantly related to the standard deviation of Tpe durations in different ECG leads. At the underlying heart rate of 60 beats per minute, Tpe intervals were shorter in female than in male individuals (82.5 ± 5.6 vs 90.0 ± 6.5 ms, p < 0.0001). When studying linear slopes between Tpe intervals measured in different leads and the underlying heart rate, we found only minimal heart rate dependency, which was not systematic across the ECG leads and/or across the population. For any ECG lead, positive Tpe/RR slope was found in some subjects (e.g., 79 and 25% of subjects for V2 and V4 measurements, respectively) and a negative Tpe/RR slope in other subjects (e.g., 40 and 65% for V6 and V5, respectively). The steepest positive and negative Tpe/RR slopes were found for measurements in lead V2 and V4, respectively. In all leads, the Tpe/RR slope values were close to zero, indicating, on average, Tpe changes well below 2 ms for RR interval changes of 100 ms. On average, longest Tpe intervals were measured in lead V2, the shortest in lead III. The study concludes that the Tpe intervals measured in different leads cannot be combined. Irrespective of the measured ECG lead, the Tpe interval is not systematically heart rate dependent, and no heart rate correction should be used in clinical Tpe investigations.

A coupled elastoplastic anisotropic damage model for rock materials

2020 ◽  
Vol 29 (8) ◽  
pp. 1222-1245
Author(s):  
Susheng Wang ◽  
Weiya Xu
Keyword(s):  
Coupling Effect ◽  
Damage Model ◽  
Coupled Model ◽  
Yield Function ◽  
Anisotropic Damage ◽  
Mapping Algorithm ◽  
Rock Materials ◽  
Return Mapping ◽  
Brittle Ductile Transition ◽  
Proposed Model

In this study, a rigorous constitutive model within the framework of thermodynamics is formulated to describe the coupling process between irreversible deformation and anisotropic damage of rock materials. The coupling effect is reflected based on the “two-surface” formulation. The plastic response is described by a yield function while the anisotropic damage is defined by a novel exponential damage criterion. In the proposed model, another feature lies in introducing parameters β and k in the proposed model to capture strain hardening/softening behaviors and brittle–ductile transition. The computational formulation scheme for the coupled model is deduced in detail by using return mapping algorithm. The validity of the coupled model is compared with the numerical simulation results and the experimental curves of the fine-grained sandstone, Beishan granite, and Jinping marble. The results indicate that the model can take into account the nonlinear mechanical behaviors of rock: coupling anisotropic damage and plasticity as well as brittle-ductile transition behaviors. Without loss of generality, the coupled model is versatile to describe the mechanical characteristics of rock materials.

A Thermoelastic-Viscoplastic Model With a Rate-Dependent Yield Strength

1982 ◽  
Vol 49 (2) ◽  
pp. 305-311 ◽  
Author(s):  
M. B. Rubin
Keyword(s):  
Yield Strength ◽  
Second Law Of Thermodynamics ◽  
Yield Function ◽  
Viscoplastic Material ◽  
Rate Dependent ◽  
Recent Developments ◽  
Constitutive Response ◽  
Temperature Rate ◽  
The Moment ◽  
Energy Equations

General nonlinear constitutive equations for a thermoelastic-viscoplastic material that exhibits a rate-dependent yield strength are developed by assuming that the yield function depends explicitly on the total strain rate and temperature rate. Following recent developments in continuum thermodynamics restrictions on the constitutive response functions are imposed to ensure that the moment of momentum and energy equations are identically satisfied and that various statements of the second law of thermodynamics are satisfied for all thermodynamical processes. A particular constitutive equation for a thermoelastic-viscoplastic material is proposed, and an analytical example is considered that examines the rate-dependent plastic response to a deformation history that includes segments of loading, unloading, and reloading, each occurring at varying strain rates.

scholarly journals Research on Strain Rate-Dependent Tsai-Hill Strength Criterion for Ethylene Propylene Diene Monomer Film

2015 ◽  
Vol 9 (1) ◽  
pp. 102-106
Author(s):  
Xu Jinsheng ◽  
Yu Jiaquan ◽  
Chen Xiong ◽  
Niu Ranming ◽  
Jia Deng
Keyword(s):  
Engineering Application ◽  
Single Layer ◽  
Strength Criterion ◽  
Insulation Material ◽  
Rate Dependency ◽  
Solid Rocket Motor ◽  
Rate Dependent ◽  
Hill Criterion ◽  
Special Factor ◽  
Solid Rocket

EPDM film is an innovative insulation material used in the Solid Rocket Motor. İt is a kind of unidirectional single layer fiber-reinforced composite plate. To analyze its mechanical behavior uniaxial tests with different loading directions and rates were performed. The test results indicated that the EPDM film is anisotropic and its mechanical properties are obviously rate-dependent. To create a rate-dependent anisotropic strength criterion, two methods were adopted to extend the Tsai-Hill strength criterion; the first was to substitute all the strength components in the Tsai-Hill criterion with the fitted rate-dependent ones, the second was to introduce a special factor named the rate-dependency factor R(ε) into the criterion. The second method is simpler in form and more suitable for an engineering application. The two rate-dependent criteria were examined by comparing the predicted results with the experimental ones, and the results showed good agreement which verified that the strength criteria were able to reveal the anisotropic rate-dependent properties of the EPDM film.

Viscoelastic-viscoplastic combined constitutive model for glassy amorphous polymers under loading/unloading/no-load states

2020 ◽  
Vol 37 (5) ◽  
pp. 1703-1735
Author(s):  
Seishiro Matsubara ◽  
Kenjiro Terada ◽  
Ryusei Maeda ◽  
Takaya Kobayashi ◽  
Masanobu Murata ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Deformation Rate ◽  
Amorphous Polymers ◽  
Elastic Behavior ◽  
Content Type ◽  
Rate Dependent ◽  
Proposed Model ◽  
Wide Range ◽  
In Series ◽  
Rheology Model

Purpose This study aims to propose a novel viscoelastic–viscoplastic combined constitutive model for glassy amorphous polymers within the framework of thermodynamics at finite strain that is capable of capturing their rate-dependent inelastic mechanical behavior in wide ranges of deformation rate and amount. Design/methodology/approach The rheology model whose viscoelastic and viscoplastic elements are connected in series is set in accordance with the multi-mechanism theory. Then, the constitutive functions are formulated on the basis of the multiplicative decomposition of the deformation gradient implicated by the rheology model within the framework of thermodynamics. Dynamic mechanical analysis (DMA) and loading/unloading/no-load tests for polycarbonate (PC) are conducted to identify the material parameters and demonstrate the capability of the proposed model. Findings The performance was validated in comparison with the series of the test results with different rates and amounts of deformation before unloading together. It has been confirmed that the proposed model can accommodate various material behaviors empirically observed, such as rate-dependent elasticity, elastic hysteresis, strain softening, orientation hardening and strain recovery. Originality/value This paper presents a novel rheological constitutive model in which the viscoelastic element connected in series with the viscoplastic one exclusively represents the elastic behavior, and each material response is formulated according to the multiplicatively decomposed deformation gradients. In particular, the yield strength followed by the isotropic hardening reflects the relaxation characteristics in the viscoelastic constitutive functions so that the glass transition temperature could be variant within the wide range of deformation rate. Consequently, the model enables us to properly represent the loading process up to large deformation regime followed by unloading and no-load processes.

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