آناليز غير خطي كمانش يك طرفه پانل هاي مركب لايه لايه بر روي فونداسيون الاستيك بدون كشش برانگيخته شده با نيروهاي مكانيكي و گرمايي

چكيده انگليسي :

110 Nonlinear Analysis Unilateral Buckling of Composite Laminated Panels on The Tensionless Elastic Foundation Exited By Mechanical and Thermal Loads Danial Panahandeh Shahraki D panahandehshahraki@me iut ac ir 2011 07 05 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Dr Alireza Shahidi shahidi@cc iut ac ir Dr Hamidreza Mirdamadi hrmirdamadi@cc iut ac irAbstract One of the ways of reinforcing the structures is to attach metallic panels to them So panel is constrainedwith structure to buckle in just one direction In this thesis unilateral buckling of circular cylindricalisotropic homogenous and composite laminated panels with finite curvature radius on tensionless elasticfoundation excited by in plane mechanical and thermal loads is analyzed with Rayleigh Ritz method Stability analysis governing equations are extracted based on classic theory assumptions and using Sandersstrain displacement relations and applying virtual work principle on total potential energy equation Inapplying thermal loads it is assumed that the panel is in isothermal heat exchange with its environment Soenergy equation is written based on mechanical effects and the influence of uniformly distributedtemperature arise is introduced to the equations as initial stresses Considering foundation effect on panel total potential energy includes foundation strain energy in addition to panel strain energy and potentialenergy caused by external forces Considering membrane strains bending strains and nonlinear strains strain energy of panel is indicated as the summation of membrane strain energy bending strain energy andstrain energy caused by nonlinear Von Karman strains From first two components stiffness matrix andfrom third component geometrical stiffness matrix of panel is obtained For defining the distribution of inplane loads resulted from thermal forces static analysis is done before stability analysis So governingequations are presented with two pre buckling static analysis equations and one linear buckling analysisequation In this thesis a net consisting of concentrated springs are used to simulate the foundation andbecause of the bi modulus behavior of foundation in the presence of compression and tensional forces incontact area between panel and foundation a contact function is used Convergence studies for definingnumber of needed springs in the unit of length for defining an appropriate net reference appropriate aredone and values are allocated to other nets with different length to perimeter ratios with respect to this net Elastic buckling curves of homogenous isotropic and composite laminated circular cylindrical panelsexcited by in plane mechanical and thermals loads are presented These curves show the relation betweencritical buckling and critical thermal loads with length to perimeter ratio in a specific central angle of paneland the relation between critical buckling load and temperature with central angle Besides the effect ofnumber and arrangement of layers in constant thickness length to perimeter ratio radius to thickness ratio boundary condition fibers orientation on critical buckling and temperature of unilateral and bilateralbuckling is investigated For verifying the present method unilateral buckling of a panel with infinitecurvature radius is compared with previous work Results have shown that the increase in the panel areabecause of the rise in length to perimeter ratio will not necessarily lead to the increase in the contact areabetween panel and foundation and as a result the critical buckling load So different patterns are seen in thevariation of the critical load and temperature It is observed that by decreasing in the radius to thicknessratio on contrary to rise in critical load and temperature the influence of the unilateral constraint on thecritical load and temperature will decline Besides by increasing the number of layers in constant thicknessthe influenc

پناهنده شهركي، دانيال

آناليز غير خطي كمانش يك طرفه پانل هاي مركب لايه لايه بر روي فونداسيون الاستيك بدون كشش برانگيخته شده با نيروهاي مكانيكي و گرمايي

آناليز پايداري , كمانش دوطرفه , روش ريلي-رتيز , تئوري كلاسيك , پانل هاي استوانه اي