• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.277-280
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• 2008

Multi layer bellows are being manufactured for commercial vehicle because of the characteristic of high durability compared with single iaγor bellows used to passenger vehicle. Finite Element Method (FEM) study and optimization about single layer bellows are actively progressed, but FEM study about multi layer bellows which have gap between layer is rarely processed. Therefore, this article presents finite element modeling of multi layer bellows for the improvement of simulation reliability. For the shape optimization of multi layer bellows, design of experiment and Taguchi method are used.

• Transactions of Materials Processing
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• v.18 no.3
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• pp.223-228
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• 2009

Generally ferritic stainless steels are used for parts of exhaust system in commercial vehicle, because they have many advantages as low price and high corrosion resistant compared with austenitic stainless steels. Even though ferritic stainless steels have such various merits, austenitic stainless steels have been used to manufacture multi-layer bellows with complex geometry because of their high ductility. Recently, the mechanical properties of the ferritic stainless steels are getting improved and alternating austenitic stainless steel. In this paper, the possibility of mass production of multi-layer bellows made of ferritic stainless steel like MH1 and 443CT was studied. Tensile test, ridging test and corrosion test were carried out to observe material properties of STS304, MH1 and 443CT. Three types of prototype bellows were made using STS304, MH1 and 443CT stainless steels, and stiffness and fatigue tests were carried out to evaluate performance of the prototype bellows.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.281-285
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• 2008

Ferritic stainless steel is used for parts of exhaust system of commercial vehicle, because it has such advantages as low price and high corrosion resistant compared with austenite stainless steel. Even though ferritic stainless steel has these merits, to manufacture multi-layer bellows with complex geometry, austenite stainless steel is being used in the industry, because of it's high ductility. However, recently, the mechanical property of the ferritic stainless is getting improved and alternating austenitic stainless steel. In this paper, the possibility of mass production of bellows made of ferritic stainless steel like MH1 and 443CT is studied. Tensile test and ridging test are carried out to observe mechanical properties of STS304, MH1 and 443CT. Forming analysis using FEM is performed to investigate plastic strain during forming process. Prototype bellows has been made using STS304, MH1 and 443CT, respectively, and fatigue tests are carried out to evaluate fatigue life of bellows.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1007-1013
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• 2011

Because of their high flexibility and durability, multilayer bellows are manufactured for use in commercial vehicles, while single-layer bellows are manufactured for use in passenger vehicles. A study based on the finite element method (FEM) and shape optimization for the single-layer bellows has been actively performed; however, until now, a study based on the FEM has rarely been performed for the multilayer bellows with gaps between the layers. This paper presents a finite-element modeling scheme for the multilayer bellows to improve simulation reliability during the evaluation of stress and flexibility. For performing shape optimization for the multilayer bellows, DOE (design of experiment) and the Kriging metamodel followed by the D-optimal method are used.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.39-45
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• 2024

Seismic safety of expansion joints for piping systems has been underscored by water pipe ruptures and leaks resulting from the Gyeongju and Pohang earthquakes. Metal bellows in piping systems are applied to prevent damage from earthquakes and road subsidence in soft ground. Designed with a series of corrugated segments called convolutions, metal bellows exhibit flexibility to accommodate displacements. Several studies have examined variations in convolution shapes and layers based on the intended performance to be evaluated. Nonetheless, the research on the seismic performance of complex bellows having multiple corrugation heights is limited. In this study, monotonic loading tests, cyclic loading tests, and fatigue tests were conducted to evaluate the shear performance in seismic conditions, of metal bellows with variable convolution heights. Single- and triple-layer bellows were considered for the experimentation. The results reveal that triple-layer bellows exhibit larger maximum deformation and fatigue life than single-layer bellows. However, the high stiffness of triple-layer bellows in resisting internal pressure poses certain disadvantages. The convolutions are less flexible at lower displacements and experience leakage at a rate related to the variable height of the convolutions in certain conditions. At lower deformation rates, the fatigue life is rated higher as the number of layers increase. It converges to a similar fatigue life at higher deformation rates.