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Characterization and modeling of ductile damage in structural steel at low and intermediate strain rates / Farid H. Abed in Journal of engineering mechanics, Vol. 138 N° 9 (Septembre 2012) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 138 N° 9 (Septembre 2012) . - pp.1186–1194. Titre : Characterization and modeling of ductile damage in structural steel at low and intermediate strain rates Type de document : texte imprimé Auteurs : Farid H. Abed, Auteur ; Adil K. Al-Tamimi, Auteur ; Reem M. Al-Himairee, Auteur Année de publication : 2012 Article en page(s) : pp.1186–1194. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : CDM  Strain  rate  Ductile  damage  Steel  SEM Résumé : In this research, the concept of continuum damage mechanics (CDM) was implemented to evaluate damage initiation and evolution in structural steel rebars at low and intermediate loading rates. The work was divided into experimental and theoretical phases to evaluate the ductile damage behavior. The experimental part involved uniaxial tensile tests for steel bars at the ambient temperature over a range of strain rates between 3.0×10−4 and 0.1 s−1. Scanning electron microscopy (SEM), coupled with image processing techniques, was utilized to characterize the damage at several loading stages. The theoretical part of this paper introduced a new energy-based isotropic damage model capable of capturing the evolution of damage throughout the deformation process. The proposed damage model was verified via comparisons with the present SEM results and with other data available in the literature. The comparisons showed good agreement, and results from both approaches indicated that cracks and voids intensified significantly with the increase of plastic strain and strain rates. Results proved that the new procedure was satisfactory for damage characterization and offered good simplifications. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000415 [article] Characterization and modeling of ductile damage in structural steel at low and intermediate strain rates [texte imprimé] / Farid H. Abed, Auteur ; Adil K. Al-Tamimi, Auteur ; Reem M. Al-Himairee, Auteur . - 2012 . - pp.1186–1194. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 9 (Septembre 2012) . - pp.1186–1194. Mots-clés : CDM  Strain  rate  Ductile  damage  Steel  SEM Résumé : In this research, the concept of continuum damage mechanics (CDM) was implemented to evaluate damage initiation and evolution in structural steel rebars at low and intermediate loading rates. The work was divided into experimental and theoretical phases to evaluate the ductile damage behavior. The experimental part involved uniaxial tensile tests for steel bars at the ambient temperature over a range of strain rates between 3.0×10−4 and 0.1 s−1. Scanning electron microscopy (SEM), coupled with image processing techniques, was utilized to characterize the damage at several loading stages. The theoretical part of this paper introduced a new energy-based isotropic damage model capable of capturing the evolution of damage throughout the deformation process. The proposed damage model was verified via comparisons with the present SEM results and with other data available in the literature. The comparisons showed good agreement, and results from both approaches indicated that cracks and voids intensified significantly with the increase of plastic strain and strain rates. Results proved that the new procedure was satisfactory for damage characterization and offered good simplifications. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000415

Experimental investigation of the Axial capacity of inelastically pretwisted steel bars / Samer A. Barakat in Journal of engineering mechanics, Vol. 136 N° 8 (Août 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 8 (Août 2010) . - pp. 1028-1035 Titre : Experimental investigation of the Axial capacity of inelastically pretwisted steel bars Type de document : texte imprimé Auteurs : Samer A. Barakat, Auteur ; Farid H. Abed, Auteur Article en page(s) : pp. 1028-1035 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Inelasticity  Steel  Bars  Critical  loads  Experimentation  Regression  analysis. Résumé : An experimental investigation on the axial load capacity of fixed-end pretwisted steel bars of rectangular solid cross sections is described in this paper. The fixed-end bar test conducted in this study includes bars with both ends griped and embedded in cylindrical slips. More than 200 specimens are considered in this study containing bars with four different cross sections, widths of 20 mm or 30 mm and thicknesses of 3 mm or 6 mm, and three different lengths of 300, 400, and 500 mm. The samples are twisted beyond their elastic limit using torque machine and then subjected to axial load using a compression MTS machine. A set of twisting angles ranges between 0 and 225° is considered for each length. Three samples are tested for each angle then the average of the results is calculated. It is proven experimentally that the permanent twists have influenced the axial strength and the static performance of the pretwisted bars. This improvement is supported by the considerable increase in the critical buckling loads of the bars for certain angles of twists. Multiple regression analysis (MRA) is also conducted using the experimental results to develop mathematical models capable of predicting the critical loads of the tested bars. Results indicate that, with a minimal processing of data, MRA could predict well the critical loads of the pretwisted bars within 99% confidence interval. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Experimental investigation of the Axial capacity of inelastically pretwisted steel bars [texte imprimé] / Samer A. Barakat, Auteur ; Farid H. Abed, Auteur . - pp. 1028-1035. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 8 (Août 2010) . - pp. 1028-1035 Mots-clés : Inelasticity  Steel  Bars  Critical  loads  Experimentation  Regression  analysis. Résumé : An experimental investigation on the axial load capacity of fixed-end pretwisted steel bars of rectangular solid cross sections is described in this paper. The fixed-end bar test conducted in this study includes bars with both ends griped and embedded in cylindrical slips. More than 200 specimens are considered in this study containing bars with four different cross sections, widths of 20 mm or 30 mm and thicknesses of 3 mm or 6 mm, and three different lengths of 300, 400, and 500 mm. The samples are twisted beyond their elastic limit using torque machine and then subjected to axial load using a compression MTS machine. A set of twisting angles ranges between 0 and 225° is considered for each length. Three samples are tested for each angle then the average of the results is calculated. It is proven experimentally that the permanent twists have influenced the axial strength and the static performance of the pretwisted bars. This improvement is supported by the considerable increase in the critical buckling loads of the bars for certain angles of twists. Multiple regression analysis (MRA) is also conducted using the experimental results to develop mathematical models capable of predicting the critical loads of the tested bars. Results indicate that, with a minimal processing of data, MRA could predict well the critical loads of the pretwisted bars within 99% confidence interval. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]