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Author: Hsu, Y. L., Steele, C. R., Sheppard, S. D. (1994-04-01); recommended: Yeh-Liang Hsu (2010-06-15).
Note: This paper is published in Structural Optimization, Vol. 7, No. 3, pp. 199-205, April 1994.

Fully stressed thickness profile design at discontinuities of axisymmetric shells


In a shell structure, the discontinuity at the intersection of two shells causes stress concentration. This paper presents a procedure which couples the Curvature Function Method with the FAST1 structural shell analysis program to find a fully stressed thickness profile which keeps the stress at the discontinuities at the nominal stress value. The Curvature Function Method is a zero-order method that requires only stress values along the shell, not gradients of the stresses with respect to the design variables, and the resulting thickness profile has C2 continuity. Although the method is independent of the structural analysis program used to determine stress values, Fast1 provides a particular advantage because it allows the user to model complex shells with only a few large shell elements and still retain a sufficiently accurate solution. Thus both preparation and computation times are reduced substantially. Convergence of different initial designs to one final design using this procedure is demonstrated for a cylinder-cone intersection problem. This procedure is also applied to two other shell models with multiple discontinuities to find their fully stressed thickness profiles. The procedure presented in this paper provides a practical technique and tool to aid the design engineer, although the fully stressed design may not be the theoretically optimal design of minimum weight.