A Practical Method for the Rational Design of Ship Structures

1980 ◽  
Vol 24 (02) ◽  
pp. 101-113 ◽  
Author(s):  
Owen F. Hughes ◽  
Farrokh Mistree ◽  
Vedran Žanic
Keyword(s):  
Optimum Design ◽  
Rational Design ◽  
Cost Effective ◽  
Practical Method ◽  
General Purpose ◽  
Processing Unit ◽  
Ship Structures ◽  
Finite Element Program ◽  
Central Processing ◽  
Element Program

A practical, rationally based method is presented for the automated optimum design of ship structures. The method required the development of (a) a rapid, design-oriented finite-element program for the analysis of ship structures; (b) a comprehensive mathematical model for the evaluation of the capability of the structure; and (c) a cost-effective optimization algorithm for the solution of a large, highly constrained, nonlinear redesign problem. These developments have been incorporated into a program called SHIPOPT. The efficiency and robustness of the method is illustrated by using it to determine the optimum design of a complete cargo hold of a general-purpose cargo ship. The overall dimensions and the design loads are the same as those used in the design of the very successful SD14 series of ships. The redesign problem contains 94 variables, a nonlinear objective function, and over 500 constraints of which approximately half are non-linear. Program SHIPOPT required approximately eight minutes of central processing unit time on a CDC CYBER 171 to determine the optimum design.

Piping Vibration and Vibration Damage Prevention Through Screening of Dynamic Susceptibility

2017 ◽  
Author(s):  
Lingfu Zeng ◽  
Lennart G. Jansson ◽  
Alexander Börjesson
Keyword(s):  
Nuclear Power ◽  
Cost Effective ◽  
General Purpose ◽  
Vibration Monitoring ◽  
Piping System ◽  
Frequency Interval ◽  
Dynamic Susceptibility ◽  
Finite Element Program ◽  
Risk Levels ◽  
Element Program

This paper continues our recent discussion on piping vibration and practical measures for preventing vibration-related damage in nuclear power industries. Our emphasis is on an empirical approach, which attempts to estimate a so-called “dynamic susceptibility” at various locations in a piping system. This approach uses a dynamic susceptibility factor (DS), which is a quotient of the modal stress to the modal velocity, as an indicator of the risk levels of vibration to measure the vibration sensitivity for excitation sources in a given frequency interval of particular interest. In the present paper, Benchmark examples tested by the general purpose finite element program ANSYS, and commercial piping programs CAEPIPE and PIPESTRESS, are presented and the potential of using DS parameters as a screening tool for determining “potentially-large” alternating stresses is illustrated. It is demonstrated that, combined with knowledge of typical vibration sources, this is a practical and cost effective way for forming a base for the vibration control prior to installation and for the planning of post-installation vibration monitoring of a piping system under operation.

Nonlinear Response and Failure of Steel Elbows Under In-Plane Bending and Pressure

2003 ◽  
Vol 125 (4) ◽  
pp. 393-402 ◽  
Author(s):  
S. A. Karamanos ◽  
E. Giakoumatos ◽  
A. M. Gresnigt
Keyword(s):  
Finite Element ◽  
Local Buckling ◽  
Shell Element ◽  
General Purpose ◽  
Element Analysis ◽  
Cross Sectional ◽  
Finite Element Program ◽  
Special Cases ◽  
Element Program ◽  
Plane Bending

The paper investigates the response of elbows under in-plane bending and pressure, through nonlinear finite element tools, supported by experimental results from real-scale tests. The finite element analysis is mainly based on a nonlinear three-node “tube element,” capable of describing elbow deformation in a rigorous manner, considering geometric and material nonlinearities. Furthermore, a nonlinear shell element from a general-purpose finite element program is employed in some special cases. Numerical results are compared with experimental data from steel elbow specimens. The comparison allows the investigation of important issues regarding deformation and ultimate capacity of elbows, with emphasis on relatively thin-walled elbows. The results demonstrate the effects of pressure and the influence of straight pipe segments. Finally, using the numerical tools, failure of elbows under bending moments is examined (cross-sectional flattening or local buckling), and reference to experimental observations is made.

Numerical Implementation of a Multi-Physical Fields Coupling Constitute Model

2013 ◽  
Vol 457-458 ◽  
pp. 354-357
Author(s):  
Yu Jie Sun ◽  
Qing Chun Cui ◽  
Suo Huai Zhang ◽  
Li Jun Yan
Keyword(s):  
Material Properties ◽  
General Purpose ◽  
Computational Method ◽  
Numerical Implementation ◽  
Temperature Dependent ◽  
Working Process ◽  
Finite Element Program ◽  
Element Program ◽  
User Material Subroutine ◽  
Constitute Model

The objective of this paper provides a numerical implementation procedure of thermo-metallurgical-mechanical constitute equation based on additively decomposition of strain rate. Together with phase transformation kinetics, the macro material properties are determined by assigning temperature dependent material properties to each phase and by applying mixture rule to combine. Then the constitute equation is implemented into general purpose implicit finite element program via user material subroutine. The effectiveness of developed computational method is confirmed by a Satoh test simulation. Simulation of Satoh test demonstrates that transformation induce plasticity has significant effect of the evolution of residual stress and can not be neglected for alloy steel during hot working process.

Muscle and Tendon Tissues: Constitutive Modeling and Computational Issues

2011 ◽  
Vol 78 (4) ◽  
Author(s):  
L. A. Spyrou ◽  
N. Aravas
Keyword(s):  
Constitutive Model ◽  
Three Dimensional ◽  
General Purpose ◽  
Connective Tissues ◽  
Semitendinosus Muscle ◽  
Finite Element Program ◽  
Passive Behavior ◽  
Rate Dependent ◽  
Activation Level ◽  
Element Program

A three-dimensional constitutive model for muscle and tendon tissues is developed. Muscle and tendon are considered as composite materials that consist of fibers and the connective tissues and biofluids surrounding the fibers. The model is nonlinear, rate dependent, and anisotropic due to the presence of the fibers. Both the active and passive behaviors of the muscle are considered. The muscle fiber stress depends on the strain (length), strain-rate (velocity), and the activation level of the muscle, whereas the tendon fiber exhibits only passive behavior and the stress depends only on the strain. Multiple fiber directions are modeled via superposition. A methodology for the numerical implementation of the constitutive model in a general-purpose finite element program is developed. The current scheme is used for either static or dynamic analyses. The model is validated by studying the extension of a squid tentacle during a strike to catch prey. The behavior of parallel-fibered and pennate muscles, as well as the human semitendinosus muscle, is studied.

Quasi-Eulerian Finite Element Formulation for Fluid-Structure Interaction

1980 ◽  
Vol 102 (1) ◽  
pp. 62-69 ◽  
Author(s):  
T. Belytschko ◽  
J. M. Kennedy ◽  
D. F. Schoeberle
Keyword(s):  
Finite Element ◽  
Interaction Analysis ◽  
Fluid Structure Interaction ◽  
General Purpose ◽  
Element Formulation ◽  
Finite Element Program ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Eulerian Formulation ◽  
Element Program

A quasi-Eulerian formulation is developed for fluid-structure interaction analysis in which the fluid nodes are allowed to move independent of the material thus facilitating the treatment of problems with large structural motions. The governing equations are presented in general form and then specialized to two-dimensional plane and axisymmetric geometries. These elements have been incorporated in a general purpose transient finite element program and results are presented for two problems and compared to experimental results.

Elastic Analysis of Journal Bearings

Volume 1 ◽  
2004 ◽  
Author(s):  
M. M. Villar ◽  
M. M. Pe´rez
Keyword(s):  
Stress Distribution ◽  
General Purpose ◽  
Von Mises Stress ◽  
Elastic Analysis ◽  
Stress Distributions ◽  
Finite Element Program ◽  
Relative Significance ◽  
Element Program ◽  
Von Mises ◽  
Hoop Stresses

In this paper a numerical model is used to investigate the effect of the elasticity of the bearing in the pressure distribution in the lubricant and the stress distribution in the bearing. The lubricant film, as well as a bearing, including the lining and the backing of the insert, and the housing, are modeled using the general-purpose ANSYS®5.7 commercial Finite Element program. Results have been obtained for the pressure, radial displacement, hoop and von Mises stress distributions at the surface of the bearing, as well as for the shear stress distribution at the interface between the lining and the backing. A number of conclusions have been drawn regarding the relative significance of the steep pressure gradient at the end of the lubricated region on the hoop stresses that cause localized bending distortions at the surface of the lining. These localized bending distortions, in turn, are likely to cause fatigue failure of the lining.

scholarly journals Analysis of Fast Fourier Transformations algorithm for CUDA Architecture

2012 ◽  
Vol 53 ◽  
Author(s):  
Beatričė Andziulienė ◽  
Evaldas Žulkas ◽  
Audrius Kuprinavičius
Keyword(s):  
Graphics Processing Unit ◽  
General Purpose ◽  
Fast Fourier Transformation ◽  
Processing Unit ◽  
Data Allocation ◽  
Analysis Method ◽  
Central Processing ◽  
Execution Speed ◽  
Cuda Architecture ◽  
Graphics Processing

In this work Fast Fourier transformation algorithm for general purpose graphics processing unit processing (GPGPU) is discussed. Algorithm structure and individual stages performance were analysed. With performance analysis method algorithm distribution and data allocation possibilities were determined, depending on algorithm stages execution speed and algorithm structure. Ratio between CPU and GPU execution during Fast Fourier transform signal processing was determined using computer-generated data with frequency. When adopting CPU code for CUDA execution, it not becomes more complex, even if stream procesor parallelization and data transfering algorith stages are considered. But central processing unit serial execution).

Numerical analysis of face-shell bedded hollow masonry walls subject to concentrated loads

1995 ◽  
Vol 22 (4) ◽  
pp. 802-818 ◽  
Author(s):  
Ezzeldin Y. Sayed-Ahmed ◽  
Nigel G. Shrive
Keyword(s):  
Finite Element ◽  
Rational Design ◽  
Element Model ◽  
Masonry Walls ◽  
Concentrated Loads ◽  
Concentrated Load ◽  
Finite Element Program ◽  
Strength Enhancement ◽  
Element Program ◽  
Iterative Procedures

A nonlinear elastoplastic finite element model has been developed for face-shell bedded hollow masonry walls subject to in-plane concentrated loads. The model takes into account geometric and material nonlinearities as well as damage due to progressive cracking. Behaviour of the masonry components subject to compressive states of stress is modelled using the theory of plasticity, and cracking is modelled using both discrete and smeared cracking approaches. The model is generated on a SUN SPARC 10/31 workstation using the preprocessor of the finite element program ANSYS; the finite element solution is obtained using the ABAQUS program on the Fujitsu VPX 240/10 and IBM RS/6000 workstation. A brief summary of the numerical modelling and the iterative procedures is discussed. Results from simulated tests of seven-course high wallettes subject to concentrated loads are used to verify the behaviour of the numerical analyses. The methodology, when combined with substructuring, allows analysis of substantially larger walls than would more typical 3-D analyses. The model can be used to check existing design rules and develop more rational design methods for hollow masonry subject to concentrated load. Key words: masonry, hollow concrete masonry, finite element modelling, cracking, failure, strength enhancement factor, concentrated loads.

Derivatives of Buckling Loads and Vibration Frequencies With Respect to Stiffness and Initial Strain Parameters

1990 ◽  
Vol 57 (1) ◽  
pp. 18-24 ◽  
Author(s):  
Raphael T. Haftka ◽  
Gerald A. Cohen ◽  
Zenon Mro´z
Keyword(s):  
Virtual Work ◽  
Direct Method ◽  
General Purpose ◽  
Initial Strain ◽  
Nonlinear Structures ◽  
Vibration Frequencies ◽  
Finite Element Program ◽  
Buckling Loads ◽  
Element Program ◽  
Derivatives Of

A uniform variational approach to sensitivity analysis of vibration frequencies and bifurcation loads of nonlinear structures is developed. Two methods of calculating the sensitivities of bifurcation buckling loads and vibration frequencies of nonlinear structures, with respect to stiffness and initial strain parameters, are presented. A direct method requires calculation of derivatives of the prebuckling state with respect to these parameters. An adjoint method bypasses the need for these derivatives by using instead the strain field associated with the second-order post-buckling state. An operator notation is used and the derivation is based on the principle of virtual work. The derivative computations are easily implemented in structural analysis programs. This is demonstrated by examples using a general purpose, finite element program and a shell-of-revolution program.

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