Optimum Autofrettage and Shrink-Fit Combination in Multi-Layer Cylinders

Abstract

The interest in the use of layered cylinders that combine autofrettage and shrink fit in order to extend fatigue lifetimes is increasing. As the number of layers increases, the sequential order of assembly and the size of each layer become more important. To achieve the most benefical result, a design optimization method is required. In this investigation, the optimum design of a three-layered vessel for maximum fatigue life expectancy under the combined effects of autofrettage and shrink fit has been considered. To obtain optimum size of each layer and to optimize the initial stress distribution, the numerical optimization procedure known as the Simplex search method is employed here. The thickness of each layer, shrink-fit pressures, and autofrettage percentages are treated as design variables. Under stress constraints, the operational sequences for assembly of a layered vessel have been formulated in order to lead to optimum results, defined as maximum life expectancy. The fatigue life consideration is based on ASME code provisions and standards for high pressure vessel technology, which define the allowable final crack depth for multilayer vessels. The proposed procedure has been carried out on a number of examples. The results show that, with proper combination of operations significant life enhancement can be achieved using the optimization procedure.

Practical estimation of the in situ physical properties of foods under high pressure

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Analytical solution of the thermo-mechanical stresses in a multilayered composite pressure vessel considering the influence of the closed ends

“…The interfacial pressure between two consecutive layers was calculated by a recursive algorithm. Jahed et al [4] optimized the design of a three-layered pressure vessel for maximizing fatigue life expectancy using the combined effect of autofrettage and shrink fitting. Ting [5,6] investigated a cylindrical anisotropic elastic circular tube under a complex loading of fluid pressure, torsion and axial loads.…”

Modeling and Finite Element Analysis of Load-Carrying Performance of a Wind Turbine Considering the Influence of Assembly Factors

“…Mack et al [6] studied the influence of temperature on the interference fit structure, permanent plastic deformation and thermal expansion of surrounding pieces, concluding that a decrease in contact pressure would be beneficial. Jahed et al [7] applied the simplex research method to obtain optimum distributions of thickness, stress and contact pressure for each layer of a multi-layer interference cylinder; as a result, the service life was prolonged. Sogalad [8] presented the influence of cylindricity and surface modification on load-carrying capacity of interference fitted assemblies.…”