12118

11104

كارشناسي ارشد

طراحي كاربردي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1395

دوازده، 70ص.: مصور، جدول، عكس(رنگي)، نمودار

ص. ع. به فارسي و انگليسي

مهدي سلماني تهراني

محمد مشايخي

واژه نامه

محمود كدخدايي، رضا جعفري ندوشن

1395/11/17

كتابنامه

مكانيك

مهندسي مكانيك

ID11104

چكيده بيلوز فلزي لولهاي كنگرهاي شكل است كه در محلهاي اتصال لولهها بهكار ميرود تا جابهجاييهاي ناشي از بارگذاري مكانيكي و گرمايي را در اثر تغييرشكل جذب نمايد هيدروفرمينگ لوله شكلدهي غلتكي و جوشدادن حلقههاي تكي روشهاي متداول توليد بيلوز هستند از ميان روشهاي توليد بيلوز هيدورفرمينگ كاربرد گستردهتري دارد توليد بيلوز بهروش هيدروفرمينگ شامل دو مرحلة بادكردگي بالجينگ و تاشدگي فولدينگ ميشود تعيين بيشينة فشار در مرحلة بادكردگي را ميتوان مهمترين پارامتر در شكلدهي بيلوز بهروش هيدروفرمينگ دانست در اين پاياننامه روشي تحليلي براي مطالعة تغييرشكل لوله در مرحلة بادكردن در فرآيند هيدروفرمينگ لوله ارائه ميشود براي اين منظور فرض ميشود جدارة لوله در هنگام بادكردن بهشكل يك كمان دايرهاي باشد با فرض همسانگردي لوله مسأله متقارن محوري خواهد بود با بررسي تعادل يك جز از سطح پوستة حاصل از دوران توزيع تنش بهصورت تحليلي بر حسب فشار داخلي شعاع كمان و ضخامت در هر نقطه بهدست آمده است سپس با چشمپوشي از تغييرشكل االستيك و با فرض رابطة خطي تنش كرنش پالستيك رابطة فشار بر حسب بيشينة افزايش قطر بيشينة برآمدگي تعيين شده است حل تحليلي توزيع تنش و همچنين رابطة فشار برآمدگي با استفاده از نتايج شبيهسازي اجزاي محدود اعتبارسنجي شدهاند سازگاري كامل براي حل تحليلي تنش و همچنين سازگاري خوب براي نمودار فشار برآمدگي نشانگر اعتبار تحليل ارائهشده است كلمات كليدي بيلوز هيدروفرمينگ انبساط آزاد لوله

Analytical and Numerical Study of Metal Bellows Manufacturing Using Hydroforming Process Zahra Dehghanian z dehghanian@me iut ac ir Date of Submission 2017 1 29 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mehdi Salmani Tehrani Tehrani@cc iut ac irAbstract Metal bellows or expansion joints are corrugated tubes which are used in connection points of pipingsystems to compensate movements vibrations or even misalignments of the connected parts Tubehydroforming roll forming and welding the individual rings are the main processes by which metal bellowsare manufactured Among different manufacturing methods tube hydroforming is widely to produce themetal bellows in a broad range of sizes There are two main steps in hydroforming of metal bellows Theseare commonly known as tube bulging and folding In tube bulging step the internal pressure in graduallyincreased to a maximum allowable value Then in folding step the die is gradually closed while the pressureis kept constant The maximum allowable pressure which can be achieved in tube bulging step is a keyparameter in designing the hydroforming of a metal bellows This pressure is mainly based on designerexperience and is usually determined via a try and error procedure In this thesis a semi analytical approachis presented to study the tube deformation during bulging step in hydroforming of a meal bellows For thispurpose the tube wall curve is approximated by a circular arc during deformation in bulging step Thematerial is assumed to be isotropic with a rigid linearly hardening stress strain curve in simple tension Assuming the process to be axially symmetric the equilibrium equations are derived for a proper element oftube surface The equilibrium equations are then integrated to determine stress distribution in the tube wall Some finite element simulations have been carried out to show the validity of the computed stresses Theintegration constant should be determined in terms of the boundary conditions However it is explained whythis approach cannot be applied due to different pattern of deformation during the initial stages of bulging Therefor an alternative approach is presented based on the ratio of stress components On the other hand thestrain components are determined based on assumed deformation geometry Hence the equivalent strain canbe computed in terms of maximum bulge The maximum bulge can be regarded as the main geometricalparameter by which the deformation during bulging can be characterized The relationship between theequivalent stress and equivalent strain will then give an equation for pressure maximum bulge Since noanalytical study was reported before again finite element simulations were employed to investigate thevalidity of presented approach A very close agreement was observed This evidently shows that the resultsof the presented model are accurate enough to be used to predict tube deformation during bulging step inhydroforming of a metal bellows Keywords Bellows Hydroforming Tube Bulging

مهدي سلماني تهراني

محمد مشايخي

محمود كدخدايي، رضا جعفري ندوشن