Papers by Keyword: Ductility

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Authors: Han Wang, Ming Hao Zhao, Ji Gao, Guang Yuan Wang
Abstract: Concrete is usually described as a three-phase material, where matrix, aggregate and interface zones are distinguished. The beam lattice model has been applied widely by many investigators to simulate fracture processes in concrete. Due to the extremely large computational effort, however, the beam lattice model faces practical difficulties. Moreover, real fracture processes are 3D and not 2D. In our investigation, a new 3D lattice called generalized beam (GB) lattice is developed to reduce computational effort. Numerical results obtained by the model are in agreement to what are observed in tests. The 3D effects of the particle content on the peak load and ductility are discussed as well as the 3D fracturing phenomenon.
Authors: Clark Hyland, W. George Ferguson
Abstract: A method for assessing likelihood of brittle fracture in cyclically loaded steel assemblies subjected to inelastic strains is proposed. The method proposed is based upon relationships between monotonic and cyclic endurance of steel specimens proposed by Kuwamura and Takagi, and analysis of crack tip opening displacement (CTOD), Charpy V-Notch (CVN) and tensile results of pre-strained, fatigue pre-cracked and side-grooved specimens of constructional steel. The proposed method allows the influence of displacement ductility classification (as used in seismic design of structures), notch geometry, and cyclic strain amplitude history on crack initiation to be incorporated into a single design analysis approach. Small scale CTOD testing of steel materials with various levels of pre-strain may be used to identify stress intensity and crack tip displacement at crack initiation for use in the analysis. The integration of a fracture mechanics based approach to analysing stress intensity in conjunction with assembly plastic deformation characteristics derived from finite element modeling offers the promise of an improved approach to steel assembly design for cyclic plastic endurance and should result in more reliable structures and reduced need for large scale testing. This has particular relevance to the structural design of seismic resisting steelwork assemblies which are expected to develop dependable ductile behaviour under high strain variable amplitude cyclic actions.
Authors: Kai Zhong Xie, Le Qin Qin, Wen Gao Lv
Abstract: Based on strength and ductility, the seismic capabilities of the chords of arch ribs, web members, horizontal integrations, suspenders and beams of suspenders of concrete filled steel tube (CFST) arch bridges are studied, then the seismic capability of the bridge is obtained. Firstly, the internal forces of the members are calculated respectively by finite element under the actions of gravity representative value and small earthquakes (0.05g). Then the ultimate bearing capacities, the ratio of ductility and the reduction coefficients of earthquake are obtained according to the failure modes. Finally, yield accelerations of ground movement are multiplied by the reduction coefficients of earthquake, which the resistance seismic capabilities of the members Ac are obtained. The seismic capability of bridge is the minimum Ac. Taking Nanning Yonghe Bridge that is a 346m CFST arch bridge as example, the seismic capability is evaluated that the bridge can resisted the earthquake which the acceleration of ground movement is respectively 0.677g. The results show that the method of seismic capability evaluation is a feasible and efficient method for seismic capability evaluation of CFST arch bridge.
Authors: Werner Menk
Abstract: Years ago, especially in Sweden, a new family of ductile iron materials was propagated: Solid solution strengthened ferritic ductile iron. Since the 2011 edition, three grades are integrated into the European Standard EN 1563: EN-GJS-450-18, EN-GJS-500-14 and EN-GJS-600-10. The introduction of these materials into the European standard generated a large interest of many engineers, which came to a real hype meanwhile. The reason is clear: While GJS-450-18 is not very different from the standard GJS-400-15, especially the grade EN-GJS-500-14 promises to have big advantages compared to the standard grade EN-GJS-500-7. Same tensile strength, from 320 MPA to 400 MPa raised 0.2%- proof strength and from 7% to 14 % doubled elongation after fracture are very interesting properties of course and the pure ferritic structure promises a better machinability furthermore. With the higher strength grade EN-GJS-600-10 very early sceptic comments raised, because the Silicon content to reach the required strength is such high, that the risk of an embrittlement of the ferrite even at room temperature and on a tensile test bar is high. But up to now, the grade EN-GJS-500-14 has the reputation to be a high strength and very high ductile material. So, a customer of us also substituted a part from steel to EN-GJS-500-14. All calculations showed a very good performance of the parts, but as soon as in serial production field damages occurred in a manner that the parts completely broke without advance warning. The investigation of the damages showed, that the parts are not only statically and cyclically loaded, but also by strikes. Deeper investigations about strike loads confirmed, that EN-GJS-500-14 is not really ductile under these conditions. The reflection to the philosophy we had with our SiboDur-700 concept, namely to combine a moderate solid solution strengthening with a moderate strengthening by pearlite with Copper, brought us to a new high strength high ductile material we call SiboDur-500. Same strength as EN-GJS-500-14, 10 % lower in 0.2%- proof stress, slightly lower in elongation after fracture, but double to more than four times energy consumption at strike loads depending om temperature!
Authors: Yue Ling Long, Jian Cai
Abstract: A new method based on material properties instead of experimental data was proposed to assess the ductility of concrete-filled steel box columns with binding bars and those without binding bars. Comparison between ductility coefficients based on experimental data and the calculated values by the proposed method shows good agreement.
Authors: Yue Ling Long, Jian Cai
Abstract: Ductility of six L-shaped concrete-filled steel columns with binding bars and one without binding bars were discussed based on the experimental study. A new method based on material properties instead of experimental data was proposed to estimate the ductility of six L-shaped concrete-filled steel columns with binding bars and one without binding bars. Comparison between ductility coefficients based on experimental data and the calculated values by the proposed method shows good agreement.
Authors: Maurizio Ferrante
Abstract: It is well known that the low ductility of nanostructured materials seriously impairs their commercial development. In its turn that mechanical property is associated to the work-hardening behaviour and the vast literature on this relationship is a measure of its importance. This paper presents a short review of the basic models of work-hardening, dealing initially with conventional “coarse” grain metals and alloys, then moving to the behaviour of sub-microcrystalline materials within the bounds of Al alloys and Equal Channel Angular Pressing. Finally, the interrelations of tensile properties, work-hardening behaviour and microstructure are illustrated by data obtained on a precipitation and a non-precipitation hardening Al alloys, namely Al-4%Cu and AA3004. Results show that low temperature aging results in higher strength and high work hardening rate, besides high ductility. The effects of precipitation and of annealing heat treatments are discussed.
Authors: Qiang Hu, Zhi Heng Deng, Zhen Zhong Pang, He Yong Lu
Abstract: A simplified seismic design model on steel truss coupling beam is suggested based on compatible distortion and balance conditions, considering second order effect and perfect plasticity. This model regards web members of the coupling beam as constraints, thus just the chord need be studied instead of the whole truss. End moments and end shears of chords and relations between distortions of components of the truss and displacement of the coupling beam are established. So curve of load-displacement, plasticity formation and development and influences of area of web members on ductility are convenient to obtain. Results show that this model is more convenient and accuracy than finite element method. Finally some valuable conclusions about influences of span-to-depth ratio and area of web member on ductility of the coupling beam are acquired to contribute to design.
Authors: Yan Wu, B.Y. Zong, M.T. Wang
Abstract: Abnormal grain growth was simulated by phase field model in order to find ways of producing scattered a few enormous grains in a nano-structural single phase AZ31 alloy to improve its ductility. It is shown that the abnormal grain growth is controlled by the three keys factors of interface energy, strain restored energy and interface mobility. Therefore, the microstructure with scattered a few enormous grains in the nano-structural matrix can be achieved after an annealing treatment if there is a small group of specially orientated nano-size grains in the original nao-structure with local low grain boundary energy or local high strain energy or local high interface mobility. The morphology of abnormal grains is also examined as function of annealing time to optimize the microstructure.
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