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EMA 405. Quadrilateral Elements. Introduction. Quadrilateral elements are 4-sided, planar elements They can address plane stress, plane strain, or axisymmetric analyses Plane stress - z =0 (for thin structures) Plane strain - z =0 (for thick structures)
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EMA 405 Quadrilateral Elements
Introduction • Quadrilateral elements are 4-sided, planar elements • They can address plane stress, plane strain, or axisymmetric analyses • Plane stress - z=0 (for thin structures) • Plane strain - z=0 (for thick structures) • Axisymmetric will be addressed in the next chapter • 2-D triangular elements are related and can be thought of as quad elements where two nodes are coincident
Element Types in ANSYS • Constant Strain Triangle • Option for Plane42 in ANSYS 3 2 1
What if triangles have midside nodes (linear strain triangle)? 3 4 5 Plane2 element in ANSYS 2 6 1
Bilinear quadrilateral element? 4 3 1 2 Option in Plane42 element in ANSYS
Bilinear Quadrilateral (cont.) • This element does not permit curvature in bending this not this
Quadratic quadrilateral element? 4 8 3 5 Plane82 element in ANSYS 7 6 1 2
Improved bilinear quadrilateral element • This is the default behavior of Plane42 in ANSYS • It adds curvature terms to the assumed displacements to permit curvature in bending
Von Mises Stress • Also known as equivalent stress • A common model for the onset of yielding in multiaxial stress states