On the Exact Solution of Non-Uniform Torsion for Beams with Axial Symmetric Cross-Section
In the traditional theory of non-uniform torsion the axial displacement field is expressed as the product of the unit twist angle and the warping function. The first one, variable along the beam axis, is obtained by a global congruence condition; the second one, instead, defined over the cross-section, is determined by solving a Neumann problem associated to the Laplace equation, as well as for the uniform torsion problem. So, as in the classical theory the warping function doesn’t punctually satisfy the first indefinite equilibrium equation, the principal aim of this work is to develop a new theory for non-uniform torsion of beams with axial symmetric cross-section, fully restrained on both ends and loaded by a constant torque, that permits to punctually satisfy the previous equation, by means of a trigonometric expansion of the axial displacement and unit twist angle functions. Furthermore, as the classical theory is generally applied with good results to the global and local analysis of ship structures, two beams having the first one an open profile, the second one a closed section, have been analyzed, in order to compare the two theories. Keywords—Non-uniform torsion, Axial symmetric cross-section, Fourier series, Helmholtz equation, FE method.
Incidence of residual stresses and steel properties variability on corroded bulk carrier reliability
Time-variant sagging/hogging hull girder bending capacity of a corroded bulk carrier is determined by Monte Carlo simulation, in terms of mean values, variation coefficients and probability density functions; the incidence of welding residual stresses and steel mechanical properties is purposely investigated. Time-variant hull girder reliability is characterized, for both sagging and hogging conditions, by the annual failure probability and is determined by Second-Order Reliability Method. Sensitivity coefficients of all random variables at discrete points in time are also determined. Four different scenarios are considered and analysed, in order to separately and jointly investigate the incidence of welding residual stresses and material properties variability on hull girder capacity and annual failure probability and compare individual results with the reference case, which is relative to no welding stresses and material properties nominal values. The Capesize single side bulk-carrier, benchmarked in the last ISSC Report, is assumed as test case. Finally, obtained results of time-variant hull girder statistical properties and annual failure probabilities are discussed.
Jet, Rocket, Nuclear, Ion and Electric Propulsion: Theory and Design
Jet, rocket, nuclear, ion, and electric propulsion; theory and design , Jet, rocket, nuclear, ion, and electric propulsion; theory and design , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی