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.

On Modeling the Mechanical Behavior of Amorphous Polymers for the Micro-Hot-Embossing of Microfluidic Devices

2008 ◽  
Author(s):  
Vikas Srivastava ◽  
Lallit Anand
Keyword(s):  
Three Dimensional ◽  
Amorphous Polymers ◽  
Hot Embossing ◽  
Compression Tests ◽  
Predictive Capability ◽  
Finite Element Program ◽  
Rate Dependent ◽  
Wide Range ◽  
Element Program ◽  
Simple Compression

In this paper, a brief summary of some of our recent work [1, 2] is presented, with the goal of developing an engineering science-based process-simulation capability for micro-hot-embossing of amorphous polymers. To achieve this goal: (i) a three-dimensional thermo-mechanically-coupled large deformation constitutive theory has been developed to model the temperature and rate-dependent elastic-viscoplastic response of amorphous polymers; (ii) the material parameters in the theory were calibrated by using new experimental data from a suite of simple compression tests on Zeonex-690R (cyclo-olefin polymer), that covers a wide range of temperatures and strain rates; (iii) the constitutive model was implemented in the finite element program ABAQUS/Explicit; and (iv) the predictive capability of the numerical simulation procedures were validated by comparing results from the simulation of a representative micro-hot-embossing process against corresponding results from a physical experiment.

An equivalent stress method to account for local buckling in beam finite elements subjected to fire

2019 ◽  
Vol 10 (3) ◽  
pp. 340-353 ◽  
Author(s):  
Chrysanthos Maraveas ◽  
Thomas Gernay ◽  
Jean-Marc Franssen
Keyword(s):  
Finite Elements ◽  
Constitutive Model ◽  
Yield Stress ◽  
Equivalent Stress ◽  
Local Buckling ◽  
Bernoulli Beam ◽  
Content Type ◽  
Model Based ◽  
Proposed Model ◽  
Practical Implications

Purpose The purpose of this paper is to present an improved temperature-dependent constitutive model for steel that accounts for local instabilities of slender plates using an effective stress-based method. This model can be easily implemented for use with Bernoulli beam finite elements (FEs) in the fire situation. Design/methodology/approach The constitutive model is derived by calibration on parametric numerical analysis on isolated plates subject to buckling at different elevated temperatures. The model is implemented in the FE software SAFIR and validation is performed against experimental and shell element analysis results. Findings A constitutive model based on an equivalent stress method is proposed as an efficient way to consider local buckling in steel members exposed to fire. The proposed stress–strain–temperature relationship is asymmetric and is modified in compression only, by reducing the proportional limit, the yield stress and the strain at yield stress. The reduction of these parameters depends on the plate’s boundary conditions, slenderness and temperature. The validation of the proposed model shows good agreement over a range of profile dimensions, temperatures and steel grades. Research limitations/implications The model is still giving conservative results for large compressive load eccentricities. An enhanced model is under development to improve the predictive capability under large eccentricities. Practical implications The proposed model, easily implemented into any finite element software, allows using fibre type (Bernoulli) beam FEs for modelling structures made of slender sections. This has major practical implications as beam elements are the workhorse used for simulating the behaviour of structures in fire. This model, thus makes it possible to simulate large structures with slender steel sections at a limited computational cost. Originality/value The paper presents a novel steel constitutive model based on an innovative approach to capture local buckling at the material level using an equivalent stress approach. The theoretical development, validation and perspectives for future improvements are presented.

Volume–mass unsaturated soil constitutive model for drying–wetting under isotropic loading–unloading conditions

2011 ◽  
Vol 48 (2) ◽  
pp. 280-313 ◽  
Author(s):  
Hung Q. Pham ◽  
Delwyn G. Fredlund
Keyword(s):  
Constitutive Model ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Research Literature ◽  
Degree Of Saturation ◽  
Soil Conditions ◽  
Constitutive Relationships ◽  
Proposed Model ◽  
Wide Range

A rigorous volume–mass constitutive model is proposed for the representation of drying–wetting under isotropic loading–unloading conditions for unsaturated soils. The proposed model utilizes concepts arising from soil physics and geotechnical engineering research and requires readily obtainable soils data for soil properties. The model can be used to predict void ratio and water content constitutive relationships (and therefore degree of saturation) for a wide range of unsaturated soils. Various stress paths (i.e., loading–unloading and drying–wetting) can be simulated, and hysteresis associated with the soil-water characteristic curve is taken into account. Two closed-form equations for the volume–mass constitutive relationships are presented for soils starting from slurry conditions. A number of test results (i.e., from experimental programs reported in the research literature) were used during the verification of the proposed volume–mass constitutive model. The volume–mass constitutive model captures key unsaturated soil conditions such as air-entry value, water-entry value, and residual conditions. The proposed model appears to satisfactorily predict unsaturated soil behavior for soils ranging from low compressible sands to high compressible clays.

A Phenomenological Constitutive Model Constructed for PC/ABS Blends

2006 ◽  
Vol 306-308 ◽  
pp. 989-994 ◽  
Author(s):  
M. Nizar Machmud ◽  
Masaki Omiya ◽  
Hirotsugu Inoue ◽  
Kikuo Kishimoto
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Constitutive Models ◽  
Strain Rates ◽  
Strain Behavior ◽  
Tension Tests ◽  
Proposed Model ◽  
Wide Range ◽  
Different Temperatures ◽  
Prediction Evaluation

Based on previous available constitutive models, a phenomenological constitutive model has been constructed and is proposed to describe the strain, strain rate and temperature dependentdeformation behavior of PC/ABS blends. In this paper, four quasi-static uniaxial tension tests of a specimen tested at different strain rates and temperatures were used to identify the constitutive model constants. By using the proposed constitutive model, predicting the stress-strain behavior of the PC/ABS blend tested at certain strain rate and different temperatures compares well to the behavior exhibited from the tests. From comparison between the DSGZ and the proposed models, proposed model shows a better prediction. Evaluation of the proposed constitutive model was also presented and it has revealed that the proposed model might have a potential to be used for predicting a wide range of temperatures and high strain rates behavior of PC/ABS blends.

Consumer satisfaction in performing arts: an empirical investigation into Romanian theatres

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Claudia Maria Cacovean ◽  
Alessandro M. Peluso ◽  
Ioan Plăiaș
Keyword(s):  
Performing Arts ◽  
Consumer Satisfaction ◽  
Current Knowledge ◽  
Consumer Involvement ◽  
Communist Country ◽  
Perceived Benefits ◽  
Content Type ◽  
Future Studies ◽  
Proposed Model ◽  
Wide Range

PurposeThe aim of the study is to explore the chain of relationships between service attributes, consumers' perceived benefits, fulfilment of personal goals, satisfaction judgements and future intentions.Design/methodology/approachThis research proposes and implements a model of consumer satisfaction in the performing arts. The model is based on means-end chain theory and incorporates consumer involvement as a moderator. The paper is a quantitative study using a questionnaire administered in Romanian theatres, the country chosen because of its post-communist profile.FindingsA partial least squares structural equation modelling analysis revealed that both core and peripheral attributes' evaluations were positively related to perceived benefits, which in turn were positively related to goal fulfilment. Acting as a mediator, goal fulfilment predicts satisfaction, which positively influences a series of intentions regarding supportive behaviours such as recommendation, donation, subscribing and repurchasing. Consumer involvement partially moderates the relationships within the proposed model.Research limitations/implicationsThe limitations of this research offer opportunities for future studies. First, as this study was conducted in Romania, the obtained results are not easily generalisable to other geographical or cultural contexts. Second, future studies could extend the proposed model to include other constructs that may be connected to satisfaction in performing arts. They could also apply the model (or an extended alternative) to adjacent fields such as opera, or live jazz, in order to explore whether the patterns of results which emerged here hold in other situations.Practical implicationsFrom a practical perspective, the research has implications for performing arts managers by offering actions to improve cultural consumption. First, the results support the idea that satisfaction is a key construct to investigate, even in the field of performing arts, as it can predict future positive intentions. Thus, arts managers should strive to maximise consumer satisfaction. From a marketing perspective, consumer satisfaction could be increased by improving core and peripheral service attributes, but especially the latter. The research provides means for audience segmentation in terms of consumer goals, benefits, and involvement. Arts managers should devote special attention to increasing consumer involvement in services provided.Social implicationsThe research provides a different view on the performing arts evaluation considering the theatregoers' perceptions. This type of evaluation is useful to understand the specificities of the audiences and to respond to their needs accordingly, contributing from a social point of view to audience development and making arts accessible to a wide range of people in a variety of ways: physically, geographically, socially and psychologically.Originality/valueThis research explores a new model of customer satisfaction in performing arts in a post-communist country, such as Romania, and the findings have implications at both theoretical and practical level. From a theoretical perspective, it contributes to a better understanding of the cognitive and emotional processes underlying the formation of satisfaction judgements in performing arts. The obtained findings are particularly useful for expanding current knowledge of how consumers think and behave with respect to performing arts. From a practical perspective, the findings have implications for arts managers deciding how to develop marketing strategies aimed at increasing satisfaction, and the consequential supportive behaviours towards performing arts.

A Rate-Dependent Inelastic Constitutive Model—Part I: Elastic-Plastic Flow

1991 ◽  
Vol 113 (3) ◽  
pp. 314-323 ◽  
Author(s):  
F. Ellyin ◽  
Z. Xia
Keyword(s):  
Constitutive Model ◽  
Plastic Flow ◽  
Inelastic Deformation ◽  
Experimental Results ◽  
Elastic Plastic ◽  
Rate Dependent ◽  
Wide Range ◽  
Strain Stress ◽  
Standard Tests ◽  
Inelastic Processes

In this part a rate-dependent elastic-plastic constitutive model is presented which is an extension of our earlier rate-indpendent model. The effect of prior creep on the subsequent inelastic deformation is also included. The model can be used to predict inelastic processes with variable strain (stress) rates. It is shown, through comparison with the experimental results, that most of the rate-effect features of the material response can be simulated by the model. Despite the wide range of application, the model is relatively simple and incorporated a few material constants which could be easily determined from standard tests.

Goal programming optimization model under uncertainty and the critical areas characterization in humanitarian logistics management

2019 ◽  
Vol 9 (1) ◽  
pp. 82-107 ◽  
Author(s):  
Mario Chong ◽  
Juan G. Lazo Lazo ◽  
Maria Cristina Pereda ◽  
Juan Manuel Machuca De Pina
Keyword(s):  
Decision Making ◽  
Disaster Management ◽  
Low Income ◽  
Point Of View ◽  
Decision Makers ◽  
Humanitarian Crisis ◽  
Content Type ◽  
Critical Areas ◽  
Proposed Model ◽  
Wide Range

Purpose The purpose of this paper is to improve disaster management models, have an optimal distribution of assets, reduce human suffering in a crisis and find a good solution for warehouse locations, distribution points, inventory levels and costs, considering the uncertainty of a wide range of variables, to serve as a support model for decision making in real situations. Design/methodology/approach A model is developed based on the recent models. It includes structured and non-structured data (historical knowledge) from a humanitarian perspective. This model considers the uncertainty in a landslide and flood area and it is applied in a representative Peruvian city. Findings The proposed model can be used to determine humanitarian aid supply and its distribution with uncertainty, regarding the affected population and its resilience. This model presents a different point of view from the efficiency of the logistics perspective, to identify the level of trust between all the stakeholders (public, private and academic). The finding provides a new insight in disaster management to cover the gap between applied research and human behavior in crisis. Research limitations/implications In this study the access of reliable information is limited. Practical implications This paper provides an operation model with uncertainty in a humanitarian crisis and a decision-making tool with some recommendation for further public policies. Originality/value This study presents a model for decision makers in a low-income zone and highlights the importance of preparedness in the humanitarian system. This paper expands the discussion of how the mathematical models and human behaviors interact with different perspectives in a humanitarian crisis.

Improved analytical approach for studying the effect of diode power detector modelling on six-port communication receiver performance

2019 ◽  
Vol 39 (2) ◽  
pp. 317-331
Author(s):  
Mehran Hazer Sahlabadi ◽  
Abdolali Abdipour ◽  
Abbas Mohammadi
Keyword(s):  
Analytical Approach ◽  
Input Power ◽  
Design System ◽  
Error Vector Magnitude ◽  
Content Type ◽  
Hardware Impairments ◽  
Proposed Model ◽  
Wide Range ◽  
Power Detector ◽  
Receiver Performance

Purpose The purpose of this paper is to study the effect of diode power detector modelling on six-port communication receiver performance. Design/methodology/approach Based on proposed and conventional squared diode model, six-port receiver’s demodulation and its error vector magnitude (EVM) performance due to hardware impairments are studied. Through considering both the models, the accuracy of proposed power detector model is compared to the squared model, and then both results are validated with envelope simulation (ENV) in advanced design system (ADS). Findings Comparing the numerical results with envelope simulation results proved that the proposed model is much more accurate than the conventional squared model for a wide range of input power levels. Originality/value Studying the receiver’s performance numerically, by considering the new proposed analytical approach for diode power detectors which is more accurate than the conventional squared model.

Investigation on the elasto-plastic constitutive equation of parts fabricated by fused deposition modeling

2019 ◽  
Vol 25 (3) ◽  
pp. 592-601 ◽  
Author(s):  
Yang Xia ◽  
Ke Xu ◽  
Guojun Zheng ◽  
Rui Zou ◽  
Baojun Li ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Constitutive Model ◽  
Yield Point ◽  
Fused Deposition Modeling ◽  
Constitutive Behavior ◽  
Elastic Behavior ◽  
Hill Model ◽  
Content Type ◽  
Fused Deposition ◽  
Deposition Modeling

Purpose The strength of printed parts by application of fused deposition modeling (FDM) has been broadly studied through experimental methods. However, constitutive behaviors of the printed parts in theory are still unclear. Therefore, this paper aims to focus on building an elasto-plastic model of the printed parts to reveal the constitutive behavior. Design/methodology/approach An elasto-plastic constitutive model that considers anisotropic characteristics is proposed. Tensile tests are performed for parameter identification by using different samples with varying printing angles. Finally, the constitutive model is completed and applied to the numerical analysis of a tensile procedure. Findings The experimental study indicated that the anisotropic characteristics are significant for elastic modulus and strength of printed parts. The polar anisotropic model is suitable for describing the anisotropic behavior of parts during the elastic deformation. The Hill model is suitable to describe the yield property. The elastic modulus and yield point of parts printed in any specific orientation can be calculated using the proposed constitutive model. Originality/value A theoretical model has been developed to describe the constitutive behavior of FDM printed part. This model can precisely describe the elastic behavior and yield point of parts printed with various orientations. This model can be applied to the finite element simulation of printed structures.

A Nonlinear Visco-Hyper Elastic Constitutive Model for Modeling Behavior of Polyurea at Large Deformations

2019 ◽  
Author(s):  
Shank S. Kulkarni ◽  
Alireza Tabarraei
Keyword(s):  
Experimental Data ◽  
Constitutive Model ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Strain Rates ◽  
Strain Behavior ◽  
Strain And Strain Rate ◽  
Proposed Model ◽  
Wide Range ◽  
Hyper Elastic

Abstract The fantastic properties of polyurea such as flexibility, durability, and chemical resistance have brought it a wide range of application in various industries. Effective prediction of the response of polyurea under different loading and environmental conditions necessitates the development of an accurate constitutive model. Similar to most polymers, the behavior of polyurea depends on both the strain and strain rate. Therefore, the constitutive model should be able to capture both these effects on the response of polyurea. To achieve this objective, in this paper, a nonlinear visco-hyper elastic constitutive model is developed by the superposition of a hyperelastic and a viscoelastic model. The proposed constitutive model can capture the behavior of polyurea under compressive as well as tensile loading conditions at various strain rates. Four parameter Ogden model is used to model the hyperelastic behavior of polyurea. The viscoelastic behavior is modeled using a three-parameter standard linear solid (SLS) model. The material parameters of the model are found by curve fitting of the proposed model to the experimental data. Comparison of the proposed model and the experimental data shows that the proposed model can closely reproduce the stress-strain behavior of polyurea under a wide range of strain rates (−6500 to 294 /s).

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