تحليل ارتعاشات پوسته هاي استوانه اي و مخروطهاي كامپوزيتي دوار با تقويت كننده هاي طولي و محيطي

چكيده انگليسي :

Abstract Rotating cylindrical and conical shells are used in many industrial applications such as driveshaft of gas turbines high speed centrifugal separators rotary kiln and rotor systems Toenhance the stiffness of the shell it is reinforced by stiffner The stiffened cylindrical andconical shell with beam type elements is extensively used in mechanical structures such asaircraft fuselages commercial vehicles road tankers missiles and submarines etc Most ofthese structures are required to operate in a dynamic environment and may have severedvibration buckling and fatigue phenomena Therefore investigating the dynamiccharacteristics of these structures such as natural frequencies and buckling loads is essentiallyrequired On the other hand considering the increasing need to apply light weight structureswith high strength the strength to weight ratio of these structure should be high as much aspossible to achieve optimum material usage energy consumption and cost in the designedstructure Shell optimum stiffening with the circumferential and longitudinal stiffenerelements is one of the solutions Also using the composite materials is another way forstiffening the shell In the present thesis the analytical solutions for the free vibration buckling and critical speedof rotating laminated composite cylindrical shell and the free vibration of rotating laminatedcomposite conical shell with longitudinal and circumferential stiffeners are presented Ritzmethod and Love s shell theory are applied in analytical solution and the effects of stiffenersare evaluated via two methods namely by a variational formulation with individual stiffenerstreated as discrete elements and by an averaging method whereby the properties of thestiffeners are averaged over the shell surface However in order to analyze the conical shellsonly the discrete element method is used considering both shell and stiffener geometry Theeffects of initial hoop tension centriugal and Coriolis forces due to the rotation are alsoconsidered in the present formulation The governing equaion of motion is evaluted usingenergy function then Hamilton s principle is applied For the case of simply supported shells the displacement fields can be expressed in terms of the products of sine and cosine functions As there is no exact solution for other boundary condition so the GDQ method is used Thismethod employ an effective way to approach the reliable results using a few numbers of gridpoint Using the GDQM the partial differential governing equations are transformedapproximately into a set of linear algabraic governing equations It should be noted here that isfor the first time the vibration of stiffened rotating conical shells is investigated Moreover the vibration equations of the conical shells have not yet been derived using the energymethod In addition investigation of critical speed the effects of axial load and internalpressure on the stiffened cylindrical shell was a new topic in this thesis The effects of parameters such as the shell and stiffeners geometries fiber s angles material stiffener s height to width ratio stiffener eccentricity stiffener material rotating speed shelllength to radius ratio and the number of stiffeners on the natural forward and backwardfrequencies buckling load and critical speed is studied Also the effects of axial andcircumferential load and rotating speed on natural frequencies buckling load and criticalspeed are studied In order to verify the results for cylindrical shell the comparison is madebetween the present results and those from other authors Finally to verify the results ofconical shells the comparison is made in special case where the angle of the conical shell goesto zero

طالبي توتي ،مصطفي

تحليل ارتعاشات پوسته هاي استوانه اي و مخروطهاي كامپوزيتي دوار با تقويت كننده هاي طولي و محيطي

ارتعاشات آزاد , سرعت بحراني , تقويت كننده هاي متعامد