Finite Element Analysis Of Bellow Extrusion Forming Process And Shape Optimization

Bellows are widely used for displacement compensation in aviation, mechanical, energy, shipbuilding and transportation industry. Bellows can resist multi-direction deformation and have exceptional resistance to bending, tension and compression. They have good displacement compensation behavior under various conditions such as vibration, offset and swell. In this thesis, extruded bellows are studied for their simple fabrication, superior overall performance and wide application.In the present thesis, a finite element analysis on mechanical performance in bellow's forming and loading process is first implemented. The analysis result shows that the mould shape has a great influence on residue stress of bellow after forming process. In actual applications, bellow is usually under long-lasting static pressure loading condition and its maximum Mises stress under pressure i s one of the most parameters to evaluate its overall performance. A shape optimization for the mould is then carried out to minimize the maximum Mises stress under pressure condition. The optimization result gives a set of optimized mould shape parameters which can be used in actual engineering application. The work in this thesis is based on large-scale commercial FEA software ABAQUS and multi-disciplinary implemented optimization system Isight.This thesis is divided into the following five chapters:In the first chapter, the classification, industry standards, application fields and recent research work are introduced briefly.In the second chapter, a finite element analysis is compared with empirical formula in the modified EJMA(US Expansion Joint Manufacturers Association) standards and the empirical formula.In the third chapter, several finite element models under different loading conditions are established. The geometry modeling, mesh generation, element and material selecting, and contact condition setting are introduced in details.In the fourth chapter, the forming and loading process analyses are studied, in forming analysis, the contact slip problem, residue stress and the influence of mould shape on residue stress are mainly studied. In the loading analysis, the distribution of Mises stress and stress state are compared between loading with the residue stress and non-residue stress armored bellows. The analysis result shows that the Mises stress region and its maximum value of armored bellows are significantly less than those of the forming processIn the fifth chapter, a co-simulation and shape optimization using ABAQUUS and Isight are implemented. The main design variables are a set of mould shape parameters. The optimization objective is to minimize the maximum Mises stress in the bellow under static pressure condition.