Determination of the Residual Stress for Single and Double Autofrettage of Thick-walled FG Cylinders Subjected to Dynamic Loading

In the present article, a numerical procedure is developed for dynamic analysis of single and double autofrettage of thick–walled Functionally Graded (FG) cylinders under transient loading. The governing differential equations are discretized and presented in explicit Lagrangian formalism.The explicit transient solution to discrete equations is obtained on the meshed region, and results for stress and strain distribution for relevant problems under inner and/or outer boundary conditions are established.The autofrettage behavior is subsequently analyzed through the application of time dependent pressure to boundary regions of the axisymmetric domain. Dynamic results, in particular in transient loading, are different in comparison with static ones due to the presence of plastic deformation and wave propagation. The residual stress resulting from internal pressure changes the structural load bearing capacity of the cylinder, in so far as the tensile stress of the outer layers might reduce, while the compressive stress of the inner layers might increase. For functionally graded materials whose material properties change continuously, dynamic analysis yields results which are entirely different as compared with their static counterparts due to the change in the wavelength and acoustic impedance. In the static analysis, the dimensionless forms of equations can be developed from the onset, while in the dynamic analysis the physical dimensions and material properties gain importance due to the inherent properties of the stress waves. Residual stresses in the inner and outer parts of the cylinder are also studied for various volume fractions of FG material under single or double autofrettage.

کلیدواژه ها:

FG cylinder ، Double autofrettage ، Dynamic simulation ، Time dependent loading ، Residual stress