Predictions of total deformations in Jebba main dam by finite element analysis technique

Author(s):  
BU Anyata ◽  
SO Osuji
1981 ◽  
Vol 18 (01) ◽  
pp. 51-68
Author(s):  
Donald Liu ◽  
Abram Bakker

Local structural problems in ships are generally the result of stress concentrations in structural details. The intent of this paper is to show that costly repairs and lay-up time of a vessel can often be prevented, if these problem areas are recognized and investigated in the design stages. Such investigations can be performed for minimal labor and computer costs by using finite-element analysis techniques. Practical procedures for analyzing structural details are presented, including discussions of the results and the analysis costs expended. It is shown that the application of the finite-element analysis technique can be economically employed in the investigation of structural details.


Author(s):  
Siva C. Chaduvula ◽  
Mikhail J. Atallah ◽  
Jitesh H. Panchal

Designers need a way to overcome information-related risks, including information leakage and misuse by their own collaborators during collaborative product realization. Existing cryptographic techniques aimed at overcoming these information-related risks are computationally expensive and impractical even for moderate problem sizes, and legal approaches such as nondisclosure agreements are not effective. The computational practicality problem is particularly pronounced for computational techniques, such as the finite element analysis (FEA). In this paper, we propose a technique that enables designers to perform simulations, such as FEA computations, without the need for revealing their information to anyone, including their design collaborators. We present a new approach, the secure finite element analysis approach, which enables designers to perform FEA without having to reveal structural/material information to their counterparts even though the computed answer depends on all the collaborators' confidential information. We build secure finite element analysis (sFEA) using computationally efficient protocols implementing a secure codesign (SCD) framework. One of our findings is that the direct implementation of using SCD framework (termed as naïve sFEA) suffers from lack of scalability. To overcome these limitations, we propose hybrid sFEA that implements performance improvement strategies. We document and discuss the experiments we conducted to determine the computational overhead imposed by both naïve and hybrid sFEA. The results indicate that the computational burden imposed by hybrid sFEA makes it challenging for large-scale FEA—our scheme significantly increases the problem sizes that can be handled when compared to implementations using previous algorithms and protocols, but large enough problem sizes will swamp our scheme as well (in some sense this is unavoidable because of the cubic nature of the FEA time complexity).


Author(s):  
Avinash Shaw ◽  
Heramb Mahajan ◽  
Tasnim Hassan

Abstract Printed Circuit Heat Exchangers (PCHEs) have high thermal efficiency because of the numerous minuscule channels. These minuscule channels result in a high thermal exchange area per unit volume, making PCHE a top contender for an intermediate heat exchanger in high-temperature reactors. Thousands of minuscule channels make finite element analysis of the PCHE computationally infeasible. A two-dimensional analysis is usually performed for the PCHE core, which cannot simulate the local channel level responses reasonably because of the absence of global constraint influence. At present, there is no analysis technique available in the ASME Code or literature that is computationally efficient and suitable for engineers to estimate PCHE local responses. A novel but practical two-step analysis framework is proposed for performing PCHE analysis. In the first step, the channeled core is replaced by orthotropic solids with similar stiffness to simulate the global thermomechanical elastic responses of the PCHE. In the second step, local submodel analysis with detailed channel geometry and loading is performed using the elastic-perfectly plastic material model. The proposed two-step analysis technique provides a unique capability to estimate the channel corner responses to be used for PCHE performance assessment. This study first developed a methodology for calculating the elastic orthotropic properties of the PCHE core. Next, the two-step analysis is performed for a realistic size PCHE core, and different issues observed in the results are scrutinized and resolved. Finally, a practical finite element analysis framework for PCHEs in high-temperature nuclear service is recommended.


1993 ◽  
Vol 115 (1) ◽  
pp. 102-109 ◽  
Author(s):  
S. A. Majlessi ◽  
D. Lee

The process of square-cup drawing is modeled employing a simplified finite element analysis technique. In order to make the algorithm computationally efficient, the deformation (total strain) theory of plasticity is adopted. The solution scheme is comprised of specifying a mesh of two-dimensional finite elements with membrane properties over the deformed configuration of the final part geometry. The initial positions of these elements are then computed by minimization of the potential energy, and therefore the strain distributions are determined. In order to verify predictions made by the finite element analysis method, a drawing apparatus is built and various drawing experiments are carried out. A number of circular and square cups are drawn and strain distributions measured. It is observed that there is generally a good agreement between computed and measured results for both axisymmetric and nonaxisymmetric cases.


2005 ◽  
Vol 488-489 ◽  
pp. 457-460 ◽  
Author(s):  
Jong Kwan Hwang ◽  
Keun Yong Sohn ◽  
Dae Min Kang ◽  
Young Su Shin

In this paper, the distribution of temperatures on specimen and the variations in punch forces on friction coefficients during press forging of AZ31 sheets have been analyzed by Finite Element Analysis technique. Results show that the top of rib and boss areas showed lower temperatures than other areas because of the heat dissipation to air by radiation. The foot regions of the rib and boss showed greater temperature rise due to greater plastic flow. The applied punch force significantly increased at 473K or lower temperatures indicating the forming temperature of AZ31 sheet should not lower than 473K. The friction condition of the punch influenced more significantly on the materials flow pattern compared to those of the die. Using a lubricant on the contact area between the punch and specimen would effectively reduce the punch force and enhance the forming capability.


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