25.01.2011_02 - MULTICRITERIA OPTIMIZATION OF A COMPOSITE...

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Unformatted text preview: MULTICRITERIA OPTIMIZATION OF A COMPOSITE CYLINDRICAL SHELL SUBJECTED TO LONGITUDINAL THER MAL STRESSES AND BUCK LING UN DER THE AC TION OF TORQUE G. Teters Keywords : composite cylindrical shell, external torque, thermal stresses, multicriteria optimization The multicriteria op ti mi za tion of the struc ture and ge om e try of a multilayer cy lin dri cal shell un der the ac tion of ex ter nal torque and lon gi tu di nal ther mal stresses is con sid ered. From known monolayer prop er ties of the com pos ite and given val ues of vari able struc tural and geo met ric pa ram e ters, the thermoelastic prop er ties of the anisotropic lay ered com pos ite are de ter mined. The cri te ria to be op ti mized — the crit i cal ex ter nal torque and ther mal stresses — de pend on two vari able pa ram e ters and tem per a ture. In the space of op ti mi za tion cri - te ria, the do main of allowable solutions and the Pareto-optimal subdomain are found. The ef fect of thermoelastic stresses on the sta bil ity of thin-walled com pos ite plates un der ex ter nal tor sion and the meth ods of their Pareto op ti mi za tion were dis cussed in [1, 2]. In the pres ent study, the state ment and meth ods for solv ing the problems of multicriteria optimization of cylindrical shells under an external torque with account of longitudinal thermal forces are developed. The multicriteria op ti mi za tion with an tag o nis tic ob jec tive func tions is based on the Pareto con cept. By us ing nu mer i - cal meth ods, we de ter mine the do main of Pareto com pro mises, where any qual ity cri te rion can be im proved only at the ex pense of wors en ing the other ones. In the gen eral case, we come to a set of com pro mise so lu tions, from which de sign ers can choose a par tic u lar so lu tion most appropriate in given conditions [3, 4]. Let us ex am ine a thin, orthotropic, cir cu lar cy lin dri cal shell hinge-sup ported at its ends, which is made of a lay ered composite reinforced according to the longitudinal-transverse scheme. The origin of a moving system of coordinates x , y , and z lies on the midsurface of the cy lin dri cal shell, with the x axis di rected along the generatrix, the y axis along the tan gent, and z along the ex ter nal nor mal to the midsurface (Fig. 1). The con di tions of hinged sup port of the shell are as fol lows: in the trans - verse di rec tion, shell edges move freely; in the lon gi tu di nal di rec tion, the sup ports are mo tion less, and dis place ments of shell edges are ab sent in this di rec tion. Thus, upon heat ing the shell, com pres sive ther mal stresses arise in the lon gi tu di nal di rec tions, but in the trans verse di rec tion, the shell ex pands freely, with out ther mal stresses. The longitudinal thermal forces reduce the critical torque of the shell....
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This note was uploaded on 02/24/2011 for the course AERO 520 taught by Professor Rs during the Spring '11 term at Istanbul Technical University.

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25.01.2011_02 - MULTICRITERIA OPTIMIZATION OF A COMPOSITE...

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