scholarly journals Modeling of Creep Behavior of an Argillaceous Rock by Numerical Homogenization Method

2018 ◽  
Author(s):  
Hachimi Dahhaoui ◽  
Naïma Belayachi ◽  
Abdeldjalil Zadjaoui
Keyword(s):  
Creep Behavior ◽  
Volume Fraction ◽  
Micromechanical Model ◽  
Mineralogical Composition ◽  
Homogenization Method ◽  
Creep Model ◽  
Numerical Homogenization ◽  
Simulation Accuracy ◽  
Argillaceous Rock ◽  
Nonlinear Viscosity

This paper is devoted to modeling the creep behavior of argillaceous rock and a comparison with experimental and numerical results from literature. The proposed time dependent modeling is based on a numerical homogenization method, matrix-inclusion material microstructure and a creep micromechanical model. The nonlinear viscosity of the argillaceous matrix is described by the creep model “Modified Time Hardening”, while classical linear elasticity is applied for the calcite and quartz inclusions. The simulation accuracy was analyzed under single and multistage creep test. A satisfactory agreement between the simulation and the experimental results are obtained by assuming the main mineral phases of the Callovo-Oxfordian argillite.  It was found that better agreements could be obtained when the multi-scale modeling is performed on sample with a given mineralogical composition and much more precisely volume fraction. The results show how numerical homogenization method is capable of effectively modelling macroscopic creep deformation.

scholarly journals An Intrinsic Material Tailoring Approach for Functionally Graded Axisymmetric Hollow Bodies Under Plane Elasticity

2021 ◽  
Author(s):  
Hassan Mohamed Abdelalim Abdalla ◽  
Daniele Casagrande
Keyword(s):  
Optimization Problem ◽  
Volume Fraction ◽  
Minimum Principle ◽  
Equivalent Stress ◽  
Micromechanical Model ◽  
Plane Elasticity ◽  
Functionally Graded ◽  
Pontryagin Minimum Principle ◽  
Volume Fractions ◽  
Material Tailoring

AbstractOne of the main requirements in the design of structures made of functionally graded materials is their best response when used in an actual environment. This optimum behaviour may be achieved by searching for the optimal variation of the mechanical and physical properties along which the material compositionally grades. In the works available in the literature, the solution of such an optimization problem usually is obtained by searching for the values of the so called heterogeneity factors (characterizing the expression of the property variations) such that an objective function is minimized. Results, however, do not necessarily guarantee realistic structures and may give rise to unfeasible volume fractions if mapped into a micromechanical model. This paper is motivated by the confidence that a more intrinsic optimization problem should a priori consist in the search for the constituents’ volume fractions rather than tuning parameters for prefixed classes of property variations. Obtaining a solution for such a class of problem requires tools borrowed from dynamic optimization theory. More precisely, herein the so-called Pontryagin Minimum Principle is used, which leads to unexpected results in terms of the derivative of constituents’ volume fractions, regardless of the involved micromechanical model. In particular, along this line of investigation, the optimization problem for axisymmetric bodies subject to internal pressure and for which plane elasticity holds is formulated and analytically solved. The material is assumed to be functionally graded in the radial direction and the goal is to find the gradation that minimizes the maximum equivalent stress. A numerical example on internally pressurized functionally graded cylinders is also performed. The corresponding solution is found to perform better than volume fraction profiles commonly employed in the literature.

scholarly journals A Phenomenological Primary–Secondary–Tertiary Creep Model for Polymer-Bonded Composite Materials

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2353
Author(s):  
Xiaochang Duan ◽  
Hongwei Yuan ◽  
Wei Tang ◽  
Jingjing He ◽  
Xuefei Guan
Keyword(s):  
Composite Materials ◽  
Creep Behavior ◽  
Reference Model ◽  
Creep Model ◽  
Creep Process ◽  
Validation Dataset ◽  
Testing Conditions ◽  
Proposed Model ◽  
Testing Data ◽  
Bonded Composite

This study develops a unified phenomenological creep model for polymer-bonded composite materials, allowing for predicting the creep behavior in the three creep stages, namely the primary, the secondary, and the tertiary stages under sustained compressive stresses. Creep testing is performed using material specimens under several conditions with a temperature range of 20 °C–50 °C and a compressive stress range of 15 MPa–25 MPa. The testing data reveal that the strain rate–time response exhibits the transient, steady, and unstable stages under each of the testing conditions. A rational function-based creep rate equation is proposed to describe the full creep behavior under each of the testing conditions. By further correlating the resulting model parameters with temperature and stress and developing a Larson–Miller parameter-based rupture time prediction model, a unified phenomenological model is established. An independent validation dataset and third-party testing data are used to verify the effectiveness and accuracy of the proposed model. The performance of the proposed model is compared with that of an existing reference model. The verification and comparison results show that the model can describe all the three stages of the creep process, and the proposed model outperforms the reference model by yielding 28.5% smaller root mean squared errors on average.

Characterization of the vibration, stability and static responses of graphene-reinforced sandwich plates under mechanical and thermal loadings using the refined shear deformation plate theory

2021 ◽  
pp. 109963622199386
Author(s):  
Hessameddin Yaghoobi ◽  
Farid Taheri
Keyword(s):  
Shear Deformation ◽  
Volume Fraction ◽  
Plate Theory ◽  
Micromechanical Model ◽  
Sheet Thickness ◽  
Analytical Investigation ◽  
Sandwich Plates ◽  
Simply Supported ◽  
Vibration Stability ◽  
Shear Deformation Plate Theory

An analytical investigation was carried out to assess the free vibration, buckling and deformation responses of simply-supported sandwich plates. The plates constructed with graphene-reinforced polymer composite (GRPC) face sheets and are subjected to mechanical and thermal loadings while being simply-supported or resting on different types of elastic foundation. The temperature-dependent material properties of the face sheets are estimated by employing the modified Halpin-Tsai micromechanical model. The governing differential equations of the system are established based on the refined shear deformation plate theory and solved analytically using the Navier method. The validation of the formulation is carried out through comparisons of the calculated natural frequencies, thermal buckling capacities and maximum deflections of the sandwich plates with those evaluated by the available solutions in the literature. Numerical case studies are considered to examine the influences of the core to face sheet thickness ratio, temperature variation, Winkler- and Pasternak-types foundation, as well as the volume fraction of graphene on the response of the plates. It will be explicitly demonstrated that the vibration, stability and deflection responses of the sandwich plates become significantly affected by the aforementioned parameters.

An Experimental Study on the Effect of Prior Plastic Straining on Creep Behavior of 304 Stainless Steel

1993 ◽  
Vol 115 (2) ◽  
pp. 200-203 ◽  
Author(s):  
Z. Xia ◽  
F. Ellyin
Keyword(s):  
Stainless Steel ◽  
Plastic Strain ◽  
Strain Rate ◽  
Creep Behavior ◽  
Test Procedure ◽  
Constant Strain Rate ◽  
304 Stainless Steel ◽  
Creep Model ◽  
Plastic Strain Rate ◽  
Creep Tests

Constant strain-rate plastic straining followed by creep tests were conducted to investigate the effect of prior plastic straining on the subsequent creep behavior of 304 stainless steel at room temperature. The effects of plastic strain and plastic strain-rate were delineated by a specially designed test procedure, and it is found that both factors have a strong influence on the subsequent creep deformation. A creep model combining the two factors is then developed. The predictions of the model are in good agreement with the test results.

Transformation Textures in Unstable Austenitic Steel

2002 ◽  
Vol 125 (1) ◽  
pp. 12-17 ◽  
Author(s):  
R. Kubler ◽  
M. Berveiller ◽  
M. Cherkaoui ◽  
K. Inal
Keyword(s):  
Martensitic Transformation ◽  
Volume Fraction ◽  
Micromechanical Model ◽  
Slip Rate ◽  
Transformation Strain ◽  
Dislocation Motion ◽  
Lattice Spin ◽  
Two Phases ◽  
The One ◽  
Elastic Plastic Materials

During the martensitic transformation in elastic-plastic materials, the local transformation strain as well as the plastic flow inside austenite are strongly related with the crystallographic orientation of the austenitic lattice. Two mechanisms involved in these materials, i.e., plasticity by dislocation motion and martensitic phase formation are coupled through kinematical constraints so that the lattice spin of the austenitic grains is different from the one due to classical slip. In this work, the lattice spin ω˙eA of the austenitic grains is related with the slip rate on the slip systems of the two phases, γ˙A and γ˙M, the evolution of the martensite volume fraction f˙ and the overall rotation rate Ω˙ of the grains. This new relation is integrated in a micromechanical model developed for unstable austenite in order to predict the evolution of the austenite texture during TRansformation Induced Plasticity (TRIP). Results for the evolution of the lattice orientation during martensitic transformation are compared with experimental data obtained by X-ray diffraction on a 304 AISI steel.

scholarly journals Influence of polyvinyl alcohol fiber and fly ash content on compressive creep properties of high ductility cementitious composites

2021 ◽  
Vol 272 ◽  
pp. 02014
Author(s):  
Bo Chen ◽  
Liping Guo ◽  
Lihui Zhang ◽  
Wenxiao Zhang ◽  
Yin Bai ◽  
...  
Keyword(s):  
Fly Ash ◽  
Polyvinyl Alcohol ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Ash Content ◽  
Creep Model ◽  
High Ductility ◽  
Fiber Volume ◽  
Leading Role ◽  
Pva Fiber

The influence of polyvinyl alcohol (PVA) fiber volume fraction and fly ash content on the creep behavior of high ductility cementitious composites (HDCC) under compression was investigated. For this investigation, the creep behavior of four HDCC groups with cube compressive strength of 30–50 MPa, PVA fiber volume fraction of 1.5% and 2.0%, and fly ash content of 60% and 80% at 7 d and 28 d loading periods, respectively, were evaluated. A compressive creep model, which reflects the loading age and holding time, was established. The results revealed that when the load was applied at 7 d and 28 d, and then maintained for 245 d, the specific creep of HDCC ranged from 95×10-6/ MPa to 165×10-6/ MPa and from 59×10-6/ MPa to 135 × 10−6/ MPa, respectively. The corresponding creep coefficients ranged from 1.48 to 2.25 and from 1.10 to 1.94, respectively. The PVA fiber volume fraction and fly ash content were the main factors affecting the specific creep of HDCC, which increased with increasing fiber fraction and fly ash content. Under short-term loading, the fiber volume fraction played a leading role in the specific creep, and the fly ash content played the leading role during long-term loading. Furthermore, the specific creep and creep coefficient decreased significantly with increasing loading age. The classical creep model described by a power exponent function is suitable for HDCC.

Creep Responses of Smart Sandwich Composites at Multiple Length Scales: Experiments and Modeling

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Anaïs Farrugia ◽  
Charles Winkelmann ◽  
Valeria La Saponara ◽  
Jeong Sik Kim ◽  
Anastasia H. Muliana
Keyword(s):  
Creep Behavior ◽  
Composite Structures ◽  
Effective Properties ◽  
Micromechanical Model ◽  
Foam Core ◽  
Sandwich Beams ◽  
Fiber Reinforced ◽  
Polymer Foam ◽  
Creep Tests ◽  
Unique Challenge

In service, composite structures present the unique challenge of damage detection and repair. Piezoelectric ceramic, such as lead zirconate titanate (PZT), is often used for detecting damage in composites. This paper investigates the effect of embedded PZT crystals on the overall creep behavior of sandwich beams comprising of glass fiber reinforced polymer laminated skins and polymer foam core, which could potentially be used as a damage-detecting smart structure. Uniaxial quasi-static and creep tests were performed on the glass/epoxy laminated composites having several fiber orientations, 0 deg, 45 deg, and 90 deg, to calibrate the elastic and viscoelastic properties of the fibers and matrix. Three-point bending creep tests at elevated temperature (80°C) were then carried out for a number of control sandwich beams (no PZT crystal) and conditioned sandwich beams (with PZT crystals embedded in the center of one facesheet). Lateral deflection of the sandwich beams was monitored for more than 60 h. The model presented in this paper is composed by two parts: (a) a simplified micromechanical model of unidirectional fiber reinforced composites used to obtain effective properties and overall creep response of the laminated skins and (b) a finite element method to simulate the overall creep behavior of the sandwich beams with embedded PZT crystals. The simplified micromechanical model is implemented in the material integration points within the laminated skin elements. Fibers are modeled as linear elastic, while a linearized viscoelastic material model is used for the epoxy matrix and foam core. Numerical results on the creep deflection of the smart sandwich beams show good correlations with the experimental creep deflection at 80°C, thus proving that this model, although currently based on material properties reported at room temperature, is promising to obtain a reasonable prediction for the creep of a smart sandwich structure at high temperatures.

scholarly journals Study of primary creep behavior of clayey soils in landslide area : suction effect

2018 ◽  
Vol 149 ◽  
pp. 02027
Author(s):  
Dahhaoui Hachimi ◽  
Belayachi Naima ◽  
Zadjaoui Abdeldjalil
Keyword(s):  
Creep Behavior ◽  
Unsaturated Soils ◽  
Primary Creep ◽  
Creep Model ◽  
Clayey Soils ◽  
Landslide Area ◽  
Deviator Stress ◽  
Landslide Process ◽  
The University

Creep behavior of clayey soils plays an extremely important role in the landslide process. The soils that make up these sliding zones are often in unsaturated state. This point indicates the need to take into account the suction effect as hydric parameter on the long-term deformation of clayey soils. In this paper, a primary creep model named Modified Time Hardening (MTH) for unsaturated soils with different matric suction has been built. Based on the literature tests results[1][2], parameters C1 and C2 of the model have relations with suction and deviator stress level respectively. The primary creep strainwill be able to demonstrate unsaturated effect of the soils. comparison between the calculated results and the literature tests results shows a good coherence. The work underway at the university of Orleans will show later the relevance of model used in the present work.

scholarly journals Nonlinear Viscoelastic–Plastic Creep Model Based on Coal Multistage Creep Tests and Experimental Validation

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3468 ◽  
Author(s):  
Junxiang Zhang ◽  
Bo Li ◽  
Conghui Zhang ◽  
Peng Li
Keyword(s):  
Creep Behavior ◽  
Physical Property ◽  
Creep Model ◽  
Creep Process ◽  
Creep Tests ◽  
Model Based ◽  
Nonlinear Viscoelastic ◽  
Improved Model ◽  
And Control ◽  
Plastic Creep

The development of fractures, which determine the complexity of coal creep characteristics, is the main physical property of coal relative to other rocks. This study conducted a series of multistage creep tests to investigate the creep behavior of coal under different stress levels. A negative elastic modulus and a non-Newtonian component were introduced into the classical Nishihara model based on the theoretical analysis of the experimental results to propose a nonlinear viscoelastic–plastic creep model for describing the non-decay creep behavior of coal. The validity of the model was verified by experimental data. The results show that this improved model can preferably exhibit decelerating, steady state, and accelerating creep behavior during the non-decay creep process. The fitting accuracy of the improved model was significantly higher than that of the classical Nishihara model. Given that acceleration creep is a critical stage in predicting the instability and failure of coal, its successful description using this improved model is crucial for the prevention and control of coal dynamic disasters.

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