Papers by Keyword: Damage Model

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Authors: Ai Min Deng, Lian Meng Gou, Dao Yuan Xu
Abstract: Taking into account the initial damage and the accumulation of damage of concrete, Mazars damage model was modified. Based on the modified Mazars damage model, combined with finite element software ANSYS, the fracture failure process of the three-point bending notched beam of concrete was simulated. The initiation load Pini and maximum load Pmax of the three-point bending beam were determined with the damage criterion, and the full relation curve of the load P versus the loading point displacement Δ of the fracture failure process of the three-point bending beam was obtained. The results show that the method of numerical simulation of concrete fracture failure process is feasible, and based on the initiation load of the crack determined by numerical simulation, the initiation toughness of the beam can be easily calculated, and the problem of calculation of the initiation toughness caused by the initiation load can not be accurately determined in the actual experiment is resolved.
Authors: Bin Liu, Quan Sheng Liu
Abstract: Based on the stress characteristics of freeze shinking shaft lining at construction and operation stages, it is set up that The anisotropic damage model including initial damage, which suit to make Damage and Fracture Mechanics analysis for the shaft lining. A 3 dimensional anisotropic damage program is compiled using FEPG software, which take the following factors into consideration: temperature, conduction conditions, concrete facture energy and its aggregate gradation. Take the liangbosi mine shaft lining for example, its damage evolutionary process under complicated stresses such as permanence field stress, the gravity and vertical additional stress changed with time is obtained. It is discussed that the facture’s position and its development process, and the mechanical mechanics of the shaft lining structure failure.
Authors: Mitsuru Ohata, Takuya Fukahori, Fumiyoshi Minami
Abstract: This study pays attention to reveal the material properties that control resistance curve for ductile crack growth (CTOD-R curve) on the basis of the mechanism for ductile crack growth, so that the R-curve could be numerically predicted only from those properties. The crack growth tests using 3-point bend specimens with fatigue pre-crack were conducted for two steels that have different ductile crack growth resistance with almost the same CTOD level for crack initiation, whereas both steels have the same “Mechanical properties” in terms of strength and work hardenability. The observation of crack growth behaviors provided that different mechanisms between ductile crack initiations from fatigue pre-crack and subsequent growth process could be applied. It was found that two “Mechanical properties” associated with ductile damage of steel could mainly influence CTOD-R curve; one is a resistance of ductile crack initiation estimated with critical local strain for ductile cracking from the surface of notched specimen, and the other one is a dependence of stress triaxiality on ductility obtained with circumferentially notched round-bar specimens. The damage model for numerically simulating the R-curve was proposed taking the two “ductile properties” into account, where ductile crack initiation from crack-tip was in accordance with critical local strain based criterion, and subsequent crack growth GTN (Gurson-Tvergaard-Needleman) based triaxiality dependent damage criterion. The proposed model accurately predicted the measured R-curve for the two steels used with the same “strength properties” through ductile crack initiation to growth.
Authors: Shu Xin Liu, Chang Wu Liu, Yaming Kang, Duo Yang
Abstract: Rock strength is closely related to composition and internal structure of water-bearing rock. By using scanning electron microscopy, This paper analyses limestone composition and micro-structural damage mechanisms in the water physical and chemical effects. Besides, By combining with triaxial compression test according to natural state and saturated state of rock samples, and by applying mohr-coulomb strength criterion based on the basic concepts of damage mechanics, The paper obtains the quantitative expression of micro-structural damage by using statistical methods. Finally, The paper establishes the relationship between compressive strength and micro-structural damage and discusses evolution laws of micro-structural damage in limestone under complex stress state, The results show that degree of micro-structural damage increase as the water affection, further more, The correlations between micro structural damage and the compressive strength of water-bearing limestone shows a nonlinear relationship according to different confining pressure.
Authors: Jun Yuan, Hong Xu, Yong Zhong Ni
Abstract: In the traditional Norton-Bailey model, the stress exponent is a constant value when the temperature keeps constant, But for some materials, this situation can’t be suitable. Based on the analysis of the experimental data, a secondary creep constitutive model which can be used in the stress exponent changing situation has been proposed. By introducing Kachanov-Rabotnov damage equation, the modified creep model has been established for P92 steel at 610°C and 670°C, which can describe the second and tertiary stage. And the method to determine creep parameters of tertiary stage has been derived. The new model was embedded into ANSYS interface program, and used for calculating the creep life of P92 steel. The results show that the model is in agreement with the experimental data.
Authors: Shan Suo Zheng, Pi Ji Hou, Bin Wang, Lei Li, Zhi Qiang Li
Abstract: In this paper, the damage performance of 13 SRHSHPC frame columns are tested and analyzed under low cycle loading. The effect of concrete strength, axial compression ratio and shear span ratio on the damage of SRHSHPC frame columns is discussed, and then the experimental result is quantified with damage index. Based on existing seismic damage models, a new seismic damage model is put forward for SRHSHPC frame columns by a nonlinear combination of deformation and accumulative dissipation.
Authors: Jésica Moreno-Puchalt, Adolfo Alonso-Durá, Verónica Llopis-Pulido, Ana Almerich-Chulia
Abstract: The structural system in Gothic architecture of Central Europe is characterized by the vaults supported on pillars and the dematerialization of walls to introduce into the Temple the maximum light possible. However the “Mediterranean Gothic” structure of the churches is formed by two sets of diaphragm walls breaking with the traditional gothic canons. The study carried out explains the reasons for these differences from an exhaustive structural analysis of Santa Catalina’s church of Valencia under seismic effects. Two methods for analyzing have been used for simulating the seismic effects: the pushover analysis and the nonlinear dynamic analysis in time-history. The non-linear damage model method with its evolution under static and dynamic loads was applied in both cases. The study has been extended up to five different simulations of the same Finite Element model, depending on the constructive elements that made up the wall structural system and two return periods of 475 and 950 years. The methods used gave a good correspondence in their results which make them two complementary methods according to the proposed objectives. The results show that the Santa Catalina’s church offers an optimal seismic response as a consequence of its structural system stiffness.
Authors: Ya Zhi Li, Kai Da Zhang, Bo Ping Zhang
Authors: M.M. Mohammadi, M.H. Sadeghi
Abstract: The outer race of a constant velocity (CV) joint is an important automotive component that is difficult to be forged because its shape is very complicated and the required precision is high. Since traditional cold forging methods are not always capable of producing complexly shaped parts, such parts are often made by processes, which require intense machining operations at relatively high costs. Thus near net shape forging is an attractive option for producing of outer race. Actual problems in final ironing sequence are prevention of ductile fracture and surface defects in final product and true formation of internal ball grooves of the workpiece. In this study Cockroft&Latham failure criterion was applied to final ironing sequence. Finally physical modeling is down using lead. In order to investigate the flow of the billet material during forging, the experimentally obtained section profile of internal grooves as measured by a CMM is compared with simulation based profile.
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