Failure Of Bellows Research Articles

Analysis and Optimization of Flow-Guided Structure Based on Fluid-Structure Interaction

Gases containing sulfur oxides can cause corrosion and failure of bellows used as furnace blowers in high-temperature environments. In order to mitigate this issue, the behavior of an effective blast furnace blower has been examined in detail. Firstly, the Sereda corrosion model has been introduced to simulate the corrosion rate of the related bellows taking into account the effects of temperature and SO2 gas; such results have been compared with effective measurements; then, the average gas velocity in the pipeline and the von Mises stress distribution of the inner draft tube have been analyzed using a Fluid-Structure Interaction model. Finally, the semi-closed internal corrosion environment caused by a 5 mm radial gap between the inner draft tube and the bellows has been considered. The gas flow rate in the residential space has been found to be low (0.5 ms–this value leads to a stable semi-closed internal corrosion environment for exhaust gas exchange); water phase in the exhaust gas is prone to accelerate the corrosion rate. On this basis, a bellows with an optimized inner draft tube has proposed, which includes corrosion-resistant honeycomb buffer rings.

Failure analysis of 316L stainless steel bellows serving in steam tube

Premature failure of bellows in pipeline transportation system was reported frequently. Burst failure occurred at 316L stainless steel bellows in a turbine after three years of service. Optical microscope, energy dispersive spectrometer, scanning electronic microscopy and numerical simulation were used to analysis the failure reason of the failed bellows. Through the investigation of the operating environment, analysis of the chemical compositions of bellows material and corrosion products, micromorphology and metallographic test of specimens with cracks, the cracking mode can be described as the stress corrosion cracking of austenitic stainless steel. The simulation analysis results further proved that there exists high level tensile stress zone on the inner surface. Based on the analysis results, failure causes can be drawn: under the combine action of working stress and corrosion medium (caustic Na and chloride), stress cracks came into being at the inner wall of the bellows. And the cracks extended under the continuous impact of high temperature steam, finally resulting in burst. Practical countermeasures were put forward to prevent similar failure of the stainless steel bellows as well.

The Effects of Convolution Geometry and Boundary Condition on the Failure of Bellows

Bellows have wide applications in automobile, aerospace, piping systems and industrial systems. An optimised shape for the bellows is expected to give good guidelines for practical design. Metallic bellows expansion joints are subject to displacement loading, this frequently results in cyclic strains. The effects of convolution geometry and boundary conditions on the failure of bellows are analysed in this study. Lateral deflection is considered as a boundary condition and a FEM solution for bellows is obtained. The stress distribution and the number of cycles to failure in the conditions of lateral deflection are obtained. Comparing results, the relation between the number of load cycles to failure and the flexible tube radius is obtained. In addition, the relation between stress and boundary conditions for the model in this study is also obtained.

A Consideration on the Low-Cycle Fatigue Life of Bellows : The Fatigue Life under Completely-Reversed-Deflection Cycles

In this paper, a method is treated which predicts the low-cycle fatigue failure of bellows subjected to completely-reversed loading, with use of the solution procedure employing the finite difference technique proposed previously by the authors for the large deflection problems of elastic-plastic shells of revolution. Namely, a procedure is discussed which estimates the low-cycle fatigue life, applying the plastic strain range under cyclic loading assessed by the elastic-plastic analysis to the Manson-Coffin equation. A U-shaped bellows subjected to deflection-controlled cyclic loading is taken as an example for the fatigue life analysis, and comparison is made with the corresponding experimental results to ascertain the appropriateness of the present method. Moreover, the fatigue lives predicted by other methods are compared with those by the present method, and fairly good agreement is recognized between the fatigue lives by the modified Langer equation which takes account of the strain concentration factor obtained from the elastic-plastic analysis and the experimental ones.