Showing 3 results for Finite Element Analysis
M.farzin, M. Salmani-Tehrani and S.h. Hashemolhoseini,
Volume 21, Issue 1 (7-2002)
Abstract
In this study, "Buckling Limit of Strain" (B.L.S.) is introduced as one of the most important limiting factors in cold roll forming process. B.L.S. is calculated by the finite element procedure. Then for two particular processes with existing analysis and experimental results, B.L.S. has been determined and evaluated. LUSAS 12.3 is used for finite element analysis. The results show that when buckling of the sheet metal is the limiting factor, B.L.S. is in good agreement with practical limits. It has also been shown that flower pattern can be well predicted when B.L.S. is obtained and this idea is another new outcome from this study. Using this criterion to define and determine B.L.S. and to design the flower pattern is a new concept accomplished for the first time.
Keywords: Cold Roll-Forming, Nonlinear Finite Element Analysis, Local Buckling
H. Moslemi Naeini, M. Maerefat and M. Soltanpour,
Volume 22, Issue 1 (7-2003)
Abstract
In hot forming process, the workpiece undergoes plastic deformation at high temperature and the microstructure of the workpiece changes according to the plastic deformation. These changes affect the mechanical properties of workpiece. In order to optimize this process, both the plastic deformation of workpiece and its microstructural changes should be taken into consideration. Since material behaviors at elevated temperatures are usually rate-sensitive, the analysis of the hot forming processes requires a thermo-viscoplastic model. In this paper, by coupling the flow stress prediction model developed with finite element analysis of thermo-viscoplastic of the hot upsetting process, temperature, strain rate, flow stress distributions and geometry of the workpiece at each time step can be calculated. At each time step, the strain rate and temperature at each element are obtained. From these values and the history of deformation, the changes in microstructure and flow stress can be determined.
Keywords: Hot forming, Process, Finite element analysis, Flow stress, Microstructure, Hot upsetting process
A. F. Nateghi, A. Vasseghi, and V. L. Shahsavar,
Volume 25, Issue 1 (7-2006)
Abstract
Bridges are potentially one of the most seismically vulnerable structures in the highway system during earthquake
events. It is known that the seismic performance of transportation systems plays a key role in the post-earthquake emergency management. Hence, it is necessary to evaluate both physical and functional aspects of bridge structures. The physical aspects of the seismic performance of bridges are evaluated by seismic fragility functions or damage probability matrices of transportation facilities. The fragility curves represent the probability of structural damage due to various levels of ground shaking. The fragility curve describes a relationship between a ground motion and a level of damage.
In this paper, the fragility curves (F.C) are developed. The vulnerability of a railway prestreed concrete bridge is assessed using fragility curves derived from dynamic nonlinear finite element analysis. A software package is developed in MATLAB to study the results obtained. Modeling of the bridge using 3D nonlinear models and modeling of abutments, bearings, effect of falling of girder on its bearings, and nonlinear interaction of soil-structure are some of the advantages of this research compared to previous ones. Reliability curves developed in this study are unique in their own kind. The proposed method as well as the results are presented in the form of vulnerability and structural reliability relations based on two damage functions.
