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Physically based constitutive model for body centered cubic metals with applications to iron / Amin Almasri in Journal of engineering mechanics, Vol. 134 N° 7 (Juillet 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.521-529 Titre : Physically based constitutive model for body centered cubic metals with applications to iron Type de document : texte imprimé Auteurs : Amin Almasri, Auteur ; George Z. Voyiadjis, Auteur Année de publication : 2010 Article en page(s) : pp.521-529 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Constitute  models  Strain  rate  Temperature  Iron. Résumé : A constitutive model is developed in this work to describe the mechanical behavior of body centered cubic metals under a wide range of strain rates and temperatures. The model is based on macromechanical state variables such as stress, strain, and material constants that include threshold and transition temperature as well as micromechanical terms such as mobile dislocation density and burgers vector. The principle of the activation energy and its dependence on temperature, strain rate, and stress is the key point in this proposed model. The model is used to simulate the experimental behavior of pure iron at various temperatures and strain rates in order to obtain the different model parameters. The model shows good capability in capturing the coupling between strain rate and temperature, plastic strain and strain rate, and plastic strain and temperature. The model is used to characterize the hardness of iron at low and high strain rates for a representative strain of 8%. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p521_s1?isAuthorized=no [article] Physically based constitutive model for body centered cubic metals with applications to iron [texte imprimé] / Amin Almasri, Auteur ; George Z. Voyiadjis, Auteur . - 2010 . - pp.521-529. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.521-529 Mots-clés : Constitute  models  Strain  rate  Temperature  Iron. Résumé : A constitutive model is developed in this work to describe the mechanical behavior of body centered cubic metals under a wide range of strain rates and temperatures. The model is based on macromechanical state variables such as stress, strain, and material constants that include threshold and transition temperature as well as micromechanical terms such as mobile dislocation density and burgers vector. The principle of the activation energy and its dependence on temperature, strain rate, and stress is the key point in this proposed model. The model is used to simulate the experimental behavior of pure iron at various temperatures and strain rates in order to obtain the different model parameters. The model shows good capability in capturing the coupling between strain rate and temperature, plastic strain and strain rate, and plastic strain and temperature. The model is used to characterize the hardness of iron at low and high strain rates for a representative strain of 8%. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p521_s1?isAuthorized=no

Nonlinear response analysis considering dynamic stiffness with both frequency and strain dependencies / Naohiro Nakamura in Journal of engineering mechanics, Vol. 134 N° 7 (Juillet 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.530-541 Titre : Nonlinear response analysis considering dynamic stiffness with both frequency and strain dependencies Type de document : texte imprimé Auteurs : Naohiro Nakamura, Auteur Année de publication : 2010 Article en page(s) : pp.530-541 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Stiffness  Nonlinear  response  Strain  Earthquakes. Résumé : The time domain evaluation of the frequency-dependent dynamic stiffness was studied and some transform methods are being proposed. In this paper, the nonlinear response analysis method of the dynamic stiffness with both frequency and strain dependency was studied. First, the frequency-dependent complex stiffness was calculated at each strain level, and then they were transformed to the impulse response in the time domain. The characteristics of the complex stiffness and the impulse response of both two-layered soil and viscoelastic dampers were investigated. Then, the nonlinear time-history response analysis method considering both dependencies using the impulse response of each strain level was proposed. The earthquake response analysis of a structure on the two-layered soil was carried out as an example. The efficiency of the method was confirmed through these investigations. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p530_s1?isAuthorized=no [article] Nonlinear response analysis considering dynamic stiffness with both frequency and strain dependencies [texte imprimé] / Naohiro Nakamura, Auteur . - 2010 . - pp.530-541. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.530-541 Mots-clés : Stiffness  Nonlinear  response  Strain  Earthquakes. Résumé : The time domain evaluation of the frequency-dependent dynamic stiffness was studied and some transform methods are being proposed. In this paper, the nonlinear response analysis method of the dynamic stiffness with both frequency and strain dependency was studied. First, the frequency-dependent complex stiffness was calculated at each strain level, and then they were transformed to the impulse response in the time domain. The characteristics of the complex stiffness and the impulse response of both two-layered soil and viscoelastic dampers were investigated. Then, the nonlinear time-history response analysis method considering both dependencies using the impulse response of each strain level was proposed. The earthquake response analysis of a structure on the two-layered soil was carried out as an example. The efficiency of the method was confirmed through these investigations. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p530_s1?isAuthorized=no

Dynamic stress concentrations in lined twin tunnels within fluid-saturated soil / Seyyed M. Hasheminejad in Journal of engineering mechanics, Vol. 134 N° 7 (Juillet 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.542-554 Titre : Dynamic stress concentrations in lined twin tunnels within fluid-saturated soil Type de document : texte imprimé Auteurs : Seyyed M. Hasheminejad, Auteur ; Reza Avazmohammadi, Auteur Année de publication : 2010 Article en page(s) : pp.542-554 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Stress  Tunnels  Saturated  soils  Three-dimensional  models. Résumé : An exact analysis for three-dimensional dynamic interaction of monochromatic seismic plane waves with two lined circular parallel tunnels within a boundless fluid-saturated porous elastic medium is presented. The novel features of Biot dynamic theory of poroelasticity along with the appropriate wave field expansions, the pertinent boundary conditions, and the translational addition theorems for cylindrical wave functions are employed to obtain a closed-form solution in the form of infinite series. The analytical results are illustrated with numerical examples in which two identical tunnels, lined with concrete and embedded within water-saturated soils of distinct frame properties (i.e., soft or stiff soils), are insonified by plane fast compressional or shear waves at end-on incidence. The basic dynamic field quantities such as the hoop and axial stress amplitudes are evaluated and discussed for representative values of the parameters characterizing the system. The effects of formation material type, angle of incidence, incident wave frequency, and the proximity of the two tunnels on the liner stresses are examined. Particular attention is paid to the influence of bonding and drainage conditions at the liner/soil interface on the dynamic stress concentrations. Limiting cases are considered and good agreement with the solutions available in the literature is obtained. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p542_s1?isAuthorized=no [article] Dynamic stress concentrations in lined twin tunnels within fluid-saturated soil [texte imprimé] / Seyyed M. Hasheminejad, Auteur ; Reza Avazmohammadi, Auteur . - 2010 . - pp.542-554. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.542-554 Mots-clés : Stress  Tunnels  Saturated  soils  Three-dimensional  models. Résumé : An exact analysis for three-dimensional dynamic interaction of monochromatic seismic plane waves with two lined circular parallel tunnels within a boundless fluid-saturated porous elastic medium is presented. The novel features of Biot dynamic theory of poroelasticity along with the appropriate wave field expansions, the pertinent boundary conditions, and the translational addition theorems for cylindrical wave functions are employed to obtain a closed-form solution in the form of infinite series. The analytical results are illustrated with numerical examples in which two identical tunnels, lined with concrete and embedded within water-saturated soils of distinct frame properties (i.e., soft or stiff soils), are insonified by plane fast compressional or shear waves at end-on incidence. The basic dynamic field quantities such as the hoop and axial stress amplitudes are evaluated and discussed for representative values of the parameters characterizing the system. The effects of formation material type, angle of incidence, incident wave frequency, and the proximity of the two tunnels on the liner stresses are examined. Particular attention is paid to the influence of bonding and drainage conditions at the liner/soil interface on the dynamic stress concentrations. Limiting cases are considered and good agreement with the solutions available in the literature is obtained. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p542_s1?isAuthorized=no

Combination resonance instability of curved panels with cutout subjected to nonuniform loading with damping / Ratnakar. S. Udar in Journal of engineering mechanics, Vol. 134 N° 7 (Juillet 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.555-566 Titre : Combination resonance instability of curved panels with cutout subjected to nonuniform loading with damping Type de document : texte imprimé Auteurs : Ratnakar. S. Udar, Auteur ; P. K. Datta, Auteur Année de publication : 2010 Article en page(s) : pp.555-566 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Damping  Resonance  Vibration  Panels. Résumé : The dynamic instability of doubly curved panels with a centrally located circular cutout, subjected to nonuniform compressive in-plane harmonic edge loading is investigated. The present work deals with the problem of the occurrence of combination resonances in contrast to single (mode) resonances in parametrically excited doubly curved panels with a central circular cutout. The method of multiple scales is used to obtain analytical expressions for the single (mode) and combination resonance instability regions. It is shown that other cases of the combination resonance can be of major importance and yield a significantly enlarged instability region in comparison to the principal instability region. The effects of nonuniform edge loading, centrally located circular cutout, damping, the static, and dynamic load factors on dynamic instability behavior of simply supported doubly curved panels are studied. The results show that under localized edge loading, combination resonance zones are as important as single (mode) resonance zones. The effects of damping show that there is a finite critical value of the dynamic load factor for each instability region below which doubly curved panels cannot become dynamically unstable. A central circular cutout has the destabilizing effect on the dynamic stability behavior of doubly curved panels subjected to nonuniform edge loading. This example of simultaneous excitation of two modes, each oscillating steadily at its own natural frequency, may be of considerable interest in vibration testing of actual structures. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p555_s1?isAuthorized=no [article] Combination resonance instability of curved panels with cutout subjected to nonuniform loading with damping [texte imprimé] / Ratnakar. S. Udar, Auteur ; P. K. Datta, Auteur . - 2010 . - pp.555-566. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.555-566 Mots-clés : Damping  Resonance  Vibration  Panels. Résumé : The dynamic instability of doubly curved panels with a centrally located circular cutout, subjected to nonuniform compressive in-plane harmonic edge loading is investigated. The present work deals with the problem of the occurrence of combination resonances in contrast to single (mode) resonances in parametrically excited doubly curved panels with a central circular cutout. The method of multiple scales is used to obtain analytical expressions for the single (mode) and combination resonance instability regions. It is shown that other cases of the combination resonance can be of major importance and yield a significantly enlarged instability region in comparison to the principal instability region. The effects of nonuniform edge loading, centrally located circular cutout, damping, the static, and dynamic load factors on dynamic instability behavior of simply supported doubly curved panels are studied. The results show that under localized edge loading, combination resonance zones are as important as single (mode) resonance zones. The effects of damping show that there is a finite critical value of the dynamic load factor for each instability region below which doubly curved panels cannot become dynamically unstable. A central circular cutout has the destabilizing effect on the dynamic stability behavior of doubly curved panels subjected to nonuniform edge loading. This example of simultaneous excitation of two modes, each oscillating steadily at its own natural frequency, may be of considerable interest in vibration testing of actual structures. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p555_s1?isAuthorized=no

Detection of stiffness reductions in concrete decks with arbitrary damage shapes using incomplete dynamic measurements / Sang-Youl Lee in Journal of engineering mechanics, Vol. 134 N° 7 (Juillet 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.567-577 Titre : Detection of stiffness reductions in concrete decks with arbitrary damage shapes using incomplete dynamic measurements Type de document : texte imprimé Auteurs : Sang-Youl Lee, Auteur ; Taehyo Park, Auteur ; Voyiadjis, George Z., Auteur Année de publication : 2010 Article en page(s) : pp.567-577 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Damage  Dynamic  response  Finite  element  method  Measurement  Stiffness  Decks  Concrete. Résumé : A new refined nondestructive evaluation technique for concrete decks with arbitrary damage shapes is presented, and its utility in detecting the location and extent of the damage using only a single dynamic measurement signal is demonstrated. Six unknown parameters are considered to determine the damage distribution, which is a modified form of the bivariate Gaussian distribution function. Using a combination of the combined finite-element method (FEM) and the advanced uniform microgenetic algorithm, the various influences of different measurement locations on the damage detection are studied. In addition, the effect of noise is simulated in order to study the influence of the measurement errors and the uncertainty of the method. The sample studies demonstrate the excellence of the proposed method from the standpoints of its computation efficiency as well as its ability to investigate the complex distribution of an arbitrary stiffness reduction. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p567_s1?isAuthorized=no [article] Detection of stiffness reductions in concrete decks with arbitrary damage shapes using incomplete dynamic measurements [texte imprimé] / Sang-Youl Lee, Auteur ; Taehyo Park, Auteur ; Voyiadjis, George Z., Auteur . - 2010 . - pp.567-577. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.567-577 Mots-clés : Damage  Dynamic  response  Finite  element  method  Measurement  Stiffness  Decks  Concrete. Résumé : A new refined nondestructive evaluation technique for concrete decks with arbitrary damage shapes is presented, and its utility in detecting the location and extent of the damage using only a single dynamic measurement signal is demonstrated. Six unknown parameters are considered to determine the damage distribution, which is a modified form of the bivariate Gaussian distribution function. Using a combination of the combined finite-element method (FEM) and the advanced uniform microgenetic algorithm, the various influences of different measurement locations on the damage detection are studied. In addition, the effect of noise is simulated in order to study the influence of the measurement errors and the uncertainty of the method. The sample studies demonstrate the excellence of the proposed method from the standpoints of its computation efficiency as well as its ability to investigate the complex distribution of an arbitrary stiffness reduction. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p567_s1?isAuthorized=no

Cohesive interface modeling of debonding failure in FRP strengthened beams / Rabinovitch, Oded in Journal of engineering mechanics, Vol. 134 N° 7 (Juillet 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.579-588 Titre : Cohesive interface modeling of debonding failure in FRP strengthened beams Type de document : texte imprimé Auteurs : Rabinovitch, Oded, Auteur Année de publication : 2010 Article en page(s) : pp.579-588 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Composite  materials  Nonlinear  analysis  Fiber  reinforced  polymers  Bonding  Beams. Résumé : A theoretical model that incorporates the concept of the cohesive interface approach for the debonding analysis of reinforced concrete beams strengthened with externally bonded fiber reinforced polymer (FRP) strips is presented. The cohesive interface concept is adopted for modeling of the debonding process near the critical adhesive-concrete interface, whereas the adhesive layer itself is modeled as a two-dimensional elastic medium. Thus, the stress and deformation fields within the adhesive layer, the coupling between the shear and normal stresses and, especially, their influence on the tractions across the cohesive interface are taken into account. The nonlinear relations between the tractions and the displacement jumps across the cohesive interface are derived using a potential function and account for the peeling effects and for the coupling between the shear-slip and the peeling-separation laws. Numerical results that examine the capabilities of the model, provide insight into the stability characteristics of the debonding mechanism, and highlight some aspects of the debonding problem are presented. A summary and conclusions close the paper. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p578_s1?isAuthorized=no [article] Cohesive interface modeling of debonding failure in FRP strengthened beams [texte imprimé] / Rabinovitch, Oded, Auteur . - 2010 . - pp.579-588. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.579-588 Mots-clés : Composite  materials  Nonlinear  analysis  Fiber  reinforced  polymers  Bonding  Beams. Résumé : A theoretical model that incorporates the concept of the cohesive interface approach for the debonding analysis of reinforced concrete beams strengthened with externally bonded fiber reinforced polymer (FRP) strips is presented. The cohesive interface concept is adopted for modeling of the debonding process near the critical adhesive-concrete interface, whereas the adhesive layer itself is modeled as a two-dimensional elastic medium. Thus, the stress and deformation fields within the adhesive layer, the coupling between the shear and normal stresses and, especially, their influence on the tractions across the cohesive interface are taken into account. The nonlinear relations between the tractions and the displacement jumps across the cohesive interface are derived using a potential function and account for the peeling effects and for the coupling between the shear-slip and the peeling-separation laws. Numerical results that examine the capabilities of the model, provide insight into the stability characteristics of the debonding mechanism, and highlight some aspects of the debonding problem are presented. A summary and conclusions close the paper. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p578_s1?isAuthorized=no

Are deicing salts necessary to promote scaling in concrete? / Antonin Fabbri in Journal of engineering mechanics, Vol. 134 N° 7 (Juillet 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.589-598 Titre : Are deicing salts necessary to promote scaling in concrete? Type de document : texte imprimé Auteurs : Antonin Fabbri, Auteur ; Olivier Coussy, Auteur ; Teddy Fen-Chong, Auteur Année de publication : 2010 Article en page(s) : pp.589-598 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Coupling  Durability  Pressures  Thermoelasticity  Spalling. Résumé : The main purpose of the present study is to investigate the role of the material parameters such as permeability, thermal diffusivity, and pore size distribution on the mechanical behavior of cementitious structures submitted to frost action, such as surface scaling. An experimental device, in which a cement paste specimen is exposed to freezing-thawing cycles under a thermal gradient, has been developed. The experimental results show that under high thermal gradient (up to 1.5°C/mm), skin damage can occur without a saline layer in contact with the frozen surface. This can be explained and quantified in the framework of poromechanics. The model is based on the coupling between liquid-ice crystal thermodynamic equilibrium, liquid water transport, thermal conduction, and elastic properties of the different phases that form the saturated porous material. It eventually predicts that a less permeable sample is more susceptible to damage by surface defacement, which explains the observed experimental result. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p589_s1?isAuthorized=no [article] Are deicing salts necessary to promote scaling in concrete? [texte imprimé] / Antonin Fabbri, Auteur ; Olivier Coussy, Auteur ; Teddy Fen-Chong, Auteur . - 2010 . - pp.589-598. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.589-598 Mots-clés : Coupling  Durability  Pressures  Thermoelasticity  Spalling. Résumé : The main purpose of the present study is to investigate the role of the material parameters such as permeability, thermal diffusivity, and pore size distribution on the mechanical behavior of cementitious structures submitted to frost action, such as surface scaling. An experimental device, in which a cement paste specimen is exposed to freezing-thawing cycles under a thermal gradient, has been developed. The experimental results show that under high thermal gradient (up to 1.5°C/mm), skin damage can occur without a saline layer in contact with the frozen surface. This can be explained and quantified in the framework of poromechanics. The model is based on the coupling between liquid-ice crystal thermodynamic equilibrium, liquid water transport, thermal conduction, and elastic properties of the different phases that form the saturated porous material. It eventually predicts that a less permeable sample is more susceptible to damage by surface defacement, which explains the observed experimental result. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p589_s1?isAuthorized=no

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