بررسي عوامل موثر در شكل دهي بيلوزهاي قطر بزرگ و كاهش عيوب شكل دهي آن ها

چكيده انگليسي :

85 Study of Effective Parameters on Forming of Large Diameter Bellows And Reducing Their Forming Defects Mehrdad Golkar Khouzani m golkarkhouzani@me iut ac ir Date of Submission 15 Septamber 2012 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mahmoud Farzin farzin@cc iut ac ir Abstract Expansion joint are the most basic parts of piping systems that are used in various industries such aspowerhouses petrochemical and aerospace industries The expansion joint is used for absorption ofmechanical and thermal displacements in piping systems Bellows is the main part of an expansion joint Bellows are essentially flexible elements of expansion joints These are usually made from austeniticstainless steels that show good weldability formability creep and corrosion resistance strength and fracturetoughness The bellows can be made by various methods such as hydroforming punch and roll formingmethods In roll forming the tube is held by three rollers two on the outside and one on the inside of thetube The tube is rotated and the rollers are driven radially and axially towards each other thus forming theconvolution The main purpose in this research is study of effective parameters on bellows roll forming oflarge diameter bellows and reducing their forming defects such as wrinkles or other undesirable shapes in themanufactured bellows Some factors of roll forming process such as position of guide rollers axial feeding orgeometrical parameters of bellows such as pitch and depth of convolution thickness can affect the finalquality of produced bellows In this thesis first explains various types of expansion joints and their application Then is pastresearch on bellows are reviewed In the next chapters of this thesis various forming method of bellows aredescribed and also their advantages and disadvantages are explained Then attention is paid on roll formingmethod of large bellows and effective parameters on this method are focused Finally different methods formaking bellows with more than one convolution are presented The finite element model has been used to simulate roll forming of bellows The model has beenconfirmed by experimental results with respect to thickness at the cross section of a convolution in the axialdirection The simulation results showed good agreement with experimental test Then effective parameterson bellows roll forming process were explained using FEM results The simulation model also showedinstability in forming that also happens in practice Consequently in this thesis various strategies forreduction of instability in forming process has been presented During bellows roll forming wrinkling mightoccur that often are located in rim of bellows and in root of convolution The wrinkles in the rim of bellowsdepend on various factors such as position and type of guide rollers in forming process pitch and depth ofconvolution thickness type of loading of the rollers Various techniques to reduce or eliminate the wrinklesthat might occur at the rim are explained In bellows roll forming bellows diameter is reduced in the root ofconvolution thus can create wrinkles in this area The wrinkle in root is increased by decreasing initialthickness of bellows Another important parameter in bellows is thickness of convolution after forming Thethickness depends on friction coefficient and axial feeding in forming process The convolution wallthickness is increased by axial feeding in roll forming process In the crests of a convolution thickness isincreased by increasing the friction coefficient Keywords Bellows Expansion Joint Roll Forming Finit Element Method

گلكار خوزاني، مهرداد

بررسي عوامل موثر در شكل دهي بيلوزهاي قطر بزرگ و كاهش عيوب شكل دهي آن ها

اتصالات انبساط گير , شكل دهي غلتكي , روش اجزا محدود