• Computational Structural Engineering
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• v.12 no.3
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• pp.50-55
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• 1999

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.10a
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• pp.103-112
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• 1994

Various kinds of fatigue failures of ocean structures were reported and the importance of fatigue life estimation at the design state is significantly recognized and various kinds of analysis approaches have been discussed. In this paper characteristics of the simplified method proposed here and the spectral method are studied and the elements of the approach are discussed. The merits and demerits of the forementioned analysis schemes are studied and the relating parameters such as SCF and S-N curves are also investigated. The simplified fatigue analysis approach and tile spectral fatigue analysis technique is applied for the analysis of bracing members of typical semi-submersible drilling rig structure for the verification of the usage of two methods and the sensitivity study has been performed using the simplified method. The result from the spectral analysis give a more realistic picture of the fatigue life of the offshore structure considered here.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.265-270
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• 2007

According to previous research, welding-induced residual stresses in steel structures can significantly affect the fatigue behaviour. Usually, high tensile residual stresses up to the yield strength are conservatively assumed at the weld toes. This conservative assumption can result in misleading fatigue assessments. Thee welding-induced residual stresses need be known in advance for a reliable fatigue assessment, which becomes possible to an increasing extent by numerical welding simulation. In this study, a fatigue Analysis technique for steel structures with welding induced residual stress is presented. First, We calculate the history of temperature according with welding process. Secondly, residual stress with a welding thermal history was evaluated by non-linear thermal stress analysis and lastly, fatigue strength is estimated with modified Goodman equation which can consider the effect of mean stress level.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.10a
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• pp.29-32
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• 1991

It is well known that the fatigue damage process in composite materials is very complicated due to complex failure mechanisms that comprise debounding, matrix cracking, delamination and fiber splitting of laminates. Therefore, the residual strength, instead of a single dominant crack length, is chosen to describe the criticality of the damage accumulated in the sublaminate. In this study, two models for residual strength degradation established by Yang-Liu and Tanimoto-Ishikawa that are capable of predicting the statistical distribution of both fatigue life and residual strength have been investigated and compared. Statistical methodologies for fatigue life prediction of composite materials have frequently been adopted. However, these are usually based on a simplified probabilistic approach considering only the variation of fatigue test data. The main object of this work is to propose a fatigue reliability analysis model which accounts for the effect of all sources of variation such as fabrication and workmanship, error in the fatigue model, load itself, etc. The proposed model is examined using the previous experimental data of GFRP and it is shown that it can be practically applied for fatigue problems in composite materials.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.60-64
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• 2008

According to previous research, welding-induced stress in steel structures can significantly affect the fatigue behaviour; it produces initial damage of weldiug part of structure locally and residual stresses reduce the fatigue strength after welding precess. In this study, through continuum damage mechanics, we can estimate the weldiug damage using the stress and strain history during welding process and the effect of welding residual stress for assessment of fatigue life. The variation of welding-induced stresses and strains need be traced precisely in advance for a reliable weldiug damage assessment. In this study, a damage and fatigue analysis techniques for steel structures with welding-induced residual stress are presented. First, We calculate the history of temperature according with welding process. And residual stress with a welding thermal history was evaluated by non-linear thermal stress analysis. Secondly, welding damage and fatigue life are estimated with kinetic damage law.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.387-392
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• 2007

The loss of strength in an aircraft structure as a result of cyclic stress over a period of life time is an important phenomenon for aircraft analysis. Load/stress spectrum can be constructed from the occurrence frequency based on the load/stress histories during a service lifetime. In this paper, three types of fatigue spectrum was compared. The rainflow counting method was applied to concentrate the stress spectrum obtained from the flight loads recorder(FLDR). A fatigue analysis for different stress spectrum was performed by using LUSAS computer application.

• Korean Journal of Computational Design and Engineering
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• v.12 no.4
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• pp.308-320
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• 2007

A multi-agent and web based engineering framework concerning the automation of fatigue durability analysis for welded bogie frame of railway vehicles is presented. Mostly, this kind of design or analysis includes complex workflow, huge amounts of information processing, and problem solving. Macro programs of I-DEAS, APDL of ANSYS, and in-house fatigue code are utilized for parametric geometry representation, automatic mesh generation, static stress analysis, fatigue durability analysis, post-processing, and data sorting. The engineering framework is implemented on the JADE. Since every task requires a fairly complex process and specialized knowledge, the multi-agent based framework is very useful to keep the independency among several disciplines or tasks and to use distributed hardware and software resources. All engineering programs are integrated by XML wrapper. Related database of the engineering framework and web based user interfaces are also developed. A parametric study is carried out to take into account the effect of geometrical change of transom support bracket on its cumulative fatigue damage. The developed engineering framework reduced remarkably the time and costs required in designing and solving engineering problems.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.122-129
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• 2004

Finite element analysis was performed to analyze structural safety of a new heavy-duty direct injection diesel engine. A half section of the in-line 6-cylinder engine was selected as a computational domain. A mapping method was used to project heat transfer coefficients from CFD results of engine coolant flow onto the FE model. The accurate setting of thermal boundary condition on the FE model was expected to result in improved prediction of temperature, cylinder bore distortion, and stresses. Characteristics of high cycle fatigue were investigated by assuming the engine was operated under the following five loading conditions repeatedly; assembly force, assembly force with thermal loading, alternating maximum gas pressure loading at each cylinder combined with assembly force and thermal loading. Distribution of fatigue safety factor was calculated by using it Haigh diagram in which the maximum and the minimum stresses were selected from the five loading cases.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.11-16
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• 1989

This paper presents a fatigue reliability model for the reliability-based evaluation of remaining fatigue life of existing rail-road bridges. It is demonstrated that the simple fatigue reliability model based on the Weibull distribution of fatigue life can be extended by incorporating various effects due to the rate of the train-traffic increase and in-service Inspections. The paper also suggests the system fatigue reliability analysis using an approximate formulation and 2nd-order bound solutions. The application of the proposed model to existing rail-road brdiges based on field load tests shows that it may be practically used for the assessment of fatigue reliability, remaining life, and in-service inspection scheduling of existing rail-road bridges.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.50-55
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• 2008

In order to investigate and estimate the cause of fatigue crack occurred to curved girder bridge that is used during 20 years, in this study, filed tests to obtain the characteristic of stress hysteresis were performed under the real traffic flows. From these test results, we analyzed the cause of fatigue crack for various fatigue crack patterns. Also, the characteristic of structural behavior for the curved girder bridge were examined from the FE analysis. In addition, to retrofit various fatigue cracks occurred in the bridge, FE analyses considering the characteristics of crack patterns were performed and retrofitting methods were suggested.