پديد آورندگان :
سلماني‌تهراني، مهدي نويسنده استاديار دانشكده‌ي مهندسي مكانيك، دانشگاه صنعتي اصفهان Salmani Tehrani, M , همتي، محمدرضا نويسنده ,
كليدواژه :
معيار تسليم ترسكا , استوانه‌ي توخالي دوار , سرعت زاويه‌يي بيشينه‌ي مجاز , مواد مدرج تابعي
چكيده فارسي :
در اين مطالعه سرعت زاويه‌يي بيشينه‌ي مجاز استوانه‌ي مدرج تابعي دوار، بر پايه‌ي نظريه‌ي تغيير شكل‌هاي كوچك در حالت كرنش ـ صفحه‌يي بررسي شده است. مدول كشساني، چگالي و تنش تسليم به‌صورت تابع تواني از مختصه‌ي شعاعي فرض شده‌اند. سرعت زاويه‌يي بيشينه‌ي مجاز استوانه، سرعت متناظر با لحظه‌ي شروع تسليم براساس معيار تسليم ترسكا معرفي شده است. براي حالت خاصي كه پارامترهاي توان يكسان باشند، تنش‌هاي بي‌بعدشده رسم، و نشان داده شده است كه همواره تنش محيطي بزرگ‌ترين و تنش شعاعي كوچك‌ترين مولفه‌ي تنش است. آنگاه اثر پارامترهاي توان، به‌ويژه اثر تغيير چگالي و تنش تسليم، برسرعت زاويه‌يي بيشينه‌ي مجاز بررسي شده است. نتايج نشان مي‌دهد در نظر گرفتن تغييرات چگالي و تنش تسليم در راستاي شعاع اثر قابل توجهي بر چگونگي شروع تسليم و درنتيجه بر سرعت زاويه‌يي بيشينه‌ي مجاز دارد. در نظر گرفتن اثر تغيير چگالي بر رفتار استوانه‌ي مدرج تابعي دوار، تازگي دارد و در پژوهش‌هاي پيشين بررسي نشده است.
چكيده لاتين :
Rotating hollow cylinders are involved in many industrial applications. On the other hand, the advantages of functionally graded materials have made them more attractive for application in different areas, such as in aircraft and aerospace industries. Because of this, in recent years, much research has been conducted on them. In this paper, maximum allowed angular velocity of a rotating hollow FGM cylinder is investigated. The analysis is based on the small deformation theory. The cylinder is assumed to be infinitely long. Therefore, the deformation state in the cylinder is in a plane strain state. Young’s modulus, density and yield stress are assumed to be power-law functions of the radial coordinate. The maximum allowed angular velocity has been defined as the angular velocity at which yielding is initiated, based on the Tresca yield criterion. Dimensionless parameters have been introduced, based on the basic geometrical and material parameters of the problem. Then, the governing equation, which is an equilibrium equation in terms of radial displacement, has been solved analytically. The strain components have then been determined, using the obtained radial displacement and strain-displacement equations. Stress components are derived using the generalized Hook’s Law. To identify stress component ordering, the radial distribution of dimensionless stress components was plotted. This was done for the special case of equal exponent parameters. The results show that for this special case, when the exponent parameters vary between -2 and 2, hoop stress and radial stress components are, respectively, the largest and the smallest stress components. Then, the effect of parameter variation, especially density and yield stress, on the maximum allowed angular velocity, is investigated. Results show that the radial variation of density and yield stress may have a considerable effect on stress distribution and yielding initiation, and, consequently, on the maximum allowed angular velocity. To the best of the authors’ knowledge, density variation was not taken into consideration in previously published research into this problem.
