ME297_02___Shellsx_Composites_x_Anisotropy - 1 Shells...

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Unformatted text preview: 1/30/2009 1 Shells, Composites & Anisotropy Shells, Composites & Anisotropy January 28 2009 January 28 2009 January 28, 2009 January 28, 2009 Today’s Agenda ¡ Shells • Read Ch. 12 in Logan. ¡ Brief review of isotropic materials ¡ Anisotropic materials E. Chan – SJSU ME297 Spring 2009 2 ¡ Composites • laminate layups • laminate stiffness matrices (A, B, D) Shell Elements - Motivations ¡ Why use shell elements when we have solid elements? ¡ Performance!!!! For thin models, shells can be used to get very good results at a fraction of the computational cost. E. Chan – SJSU ME297 Spring 2009 3 ¡ Some structures are more naturally modeled with shells (vs thin solids). E.g. auto body, aircraft. 8160 solids or 108 shells Modeling Example ¡ How would you model this mechanical part? E. Chan – SJSU ME297 Spring 2009 4 Shell Elements - Motivations 3D Solid 3D Shell 163 solids E. Chan – SJSU ME297 Spring 2009 5 2D Plane Stress ~49000 equations 124 secs elapsed 32 2D plates ~2040 equations 2.88 secs elapsed 29 shells ~5750 equations 7.8 secs elapsed Why use shells instead of plane stress? Shell Elements ¡ Shells are fully 3-D elements which are thin in one dimension (its depth). ¡ Plates are a special case of shells Î flat shells ¡ Shells deform: E. Chan – SJSU ME297 Spring 2009 6 • Axially (membrane stretching) • Transverse shear • Bending ¡ Which element do you know that has the same modes of deformation? 1/30/2009 2 θ Side View w Degrees of Freedom for Shells ¡ A shell has 6 dofs per function: • 3 translational dofs • 3 rotational dofs E. Chan – SJSU ME297 Spring 2009 7 ¡ Compare these with other elements such as beam and solid elements? Local Normal To surface w, θ z v, θ y u, θ x Limitations of Shells ¡ Shells are recommended for very thin sections. Thin direction should be < 1/10 th of other two dimensions....
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ME297_02___Shellsx_Composites_x_Anisotropy - 1 Shells...

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