• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.96-111
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• 1995

A bellows is a component installed in the automobile exhaust system to reduce the impact from an engine. It's stiffness has a great influence on the natural frequency of the system. Therefore, it must be designed to keep the specified stiffness that requires in the system. This study present the finite element analysis of U-typed bellows using a curved conical frustum element and the shape optimal design with specified stiffness. The finite element analysis is verified by comparing with the experimental results. In the shape optimal design, the weight is considered as the cost function. The specified stiffness from the system design is transformed to equality constraints. The formulation has inequality constraints imposed on the fatigue limit, the natural frequencies, the buckling load and the manufacturing conditions. A procedure for shape optimization adopts a thickness, a corrugation radius, and a length of annular plate as optimal design variables. The external loading conditions include the axial and lateral loads with a boundary condition fixed at an end of the bellows. The recursive quadratic programming algorithm is selected to solve the problem. The result are compared with the existing bellows, and the characteristics of the bellows is investigated through the optimal design process. The optimized shape of the bellows are expected to give quite a good guideline to the practical design.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1273-1281
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• 1988

In this study, the dynamic characteristics of Bellows, used for expansion joint, were investigate by F.E.M. Using the axisymmetric conical frustum element, the natural frequencies, modevectors and the parameters governing the dynamic characteristics of Bellows were also investigated. Through the experiment, it was shown that the results calculated by finite element method and measured experimental values were in good agreement.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1439-1450
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• 1995

Bellows is a familiar component in piping systems as it provides a relatively simple means of absorbing thermal expansion and providing system flexibility. In routine piping flexibility analysis by finite element methods, bellows is usually considered to be straight pipe runs modified by an appropriate flexibility factor; maximum stresses are evaluated using a corresponding stress concentration factor. The aim of this study is to develop a bellows finite element, which similarly includes more complex shell type deformation patterns. This element also does not require flexibility or stress factors, but evaluates more detailed deformation and stress patterns. The proposed bellows element is a 3-D, 2-noded line element, with three degrees of freedom per node and no bending. It is formulated by including additional 'internal' degrees of freedom to account for the deformation of the bellows corrugation; specifically a quarter toroidal section of the bellows, loaded by axial force, is considered and the shell type deformation of this is include by way of an approximating trigonometric series. The stiffness of each half bellows section may be found by minimising the potential energy of the section for a chosen deformation shape function. An experiment on the flexibility is performed to verify the reliability for bellows finite element.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.8
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• pp.1195-1208
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• 1997

Bellows is a component in piping systems which absorbs mechanical deformation with flexibility. Its geometry is an axial symmetric shell which consists of two toroidal shells and one annular plate or conical shell. In order to analyze bellows, this study presents the finite element analysis using a conical frustum shell element. A finite element analysis is developed to analyze various bellows. The validity of the developed program is verified by the experimental results for axial and lateral stiffness. The formula for calculating the natural frequency of bellows is made by the simple beam theory. The formula for fatigue life is also derived by experiments. The shape optimal design problem is formulated using multiple objective optimization. The multiple objective functions are transformed to a scalar function by weighting factors. The stiffness, strength and specified stiffness are considered as the multiple objective function. The formulation has inequality constraints imposed on the fatigue limit, the natural frequencies, and the manufacturing conditions. Geometric parameters of bellows are the design variables. The recursive quadratic programming algorithm is selected to solve the problem. The results are compared to existing bellows, and the characteristics of bellows is investigated through optimal design process. The optimized shape of bellows is expected to give quite a good guideline to practical design.

• Journal of Chest Surgery
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• v.35 no.6
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• pp.439-448
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• 2002

Pulmonary artery banding (PAB) in the functional univentricular heart (UVH) is a palliative procedure for staging toward the Fontan procedure; however, it is known to be a risk factor. Material and method： The records of all 37 patients with functional UVHs who underwent surgical palliation using PAB between September 1989 and August 1999 were reviewed retrospectively. We investigated the aortic arch obstruction, the development and progression of subaortic stenosis after PAB, and risk factor of mortality according to surgical method. Result： In 37 neonates and infants with single ventricular physiology, aortic arch obstruction was combined in 7. There were 6 early deaths (16.2%) after PAB and 3 late deaths (8.1%) after Fontan operation. The actuarial overall survival including early mortality at 3 and 5 years were 80.7$\pm$6.6%, 72.2$\pm$8.2% respectively. Among 31 patients who survived PAB, 27 patients (87.1 %) could become candidates for Fontan operation； 22 patients (71.0%) completed Fontan operation with 3 deaths and 5 were waiting bidirectional cavopulmonary shunt(BCPS) or Fontan operation (follow-up mean 4.5 year, minimal 2 year). Subaortic stenosis developed in 8 patients after PAB (8/29, 27.6%)； 3 cases in the patients without arch anomaly (3/22, 13.6%) and 5 in those with arch anomaly (5/7, 71.4%). The subaortic stenosis was managed with Damus-Kaye-Stansel procedure (DKS) in 6 patients without operative mortality and conal septum resection in 2 without long-term survivor. Analysis of risk factors established that aortic arch obstruction was strongly associated with subaortic stenosis (p＜0.001). The only risk factor of late mortality was Fontan procedure without staged palliation by BCPS (p=0.001). Conclusion： PAB is effective as an initial palliative step in functional UVH. And the high risk group of patients with aortic obstruction can undergo effective short-term PAB as an initial palliative step, with subsequent DKS for subaortic stenosis. This strategy, initial PAB and careful surveillance, and early relief of subaortic stenosis can maintain acceptable anatomy and hemodynamics for later Fontan procedures.