Strain-Life Approach: Application for Fatigue Design of Ship Superstructure Critical Detail

Abstract

Strain-Life approach to fatigue analysis of structures being developed since early 1960s recently was considered applicable in Civil Engineering, in particular, for fatigue evaluation of bridge structure with integrated abutments. To exemplify the approach and display the problems of its implementation in fatigue design, in-service reliability of structures, an example of fatigue design of a ship superstructure critical detail is presented. The detail is located at expansion joint ending in the superstructure which is frequently applied in ship design aimed at reducing stresses in a long superstructure caused by the general bending deformation of ship hull. Specific of the detail is the high local stress concentration which may result in fatigue damage menacing integrity of the ship hull. In the example of fatigue design of the expansion joint the modified «Strain-Life» criterion for fatigue of material is applied along with empirical relationship providing evaluation of the local strain. This version of the approach allows assessment of fatigue properties of the detail without utilizing Neuber’s formula and presenting the loading history in the block-type format. The results of analysis allowed selection of the expansion joint detail of the superstructure geometry and construction procedure at a shipyard providing necessary reliability.

Thermal-Fatigue Analysis of Turbine Discs under Complex Thermo-Mechanical Loading with Account of Plasticity and Creep Effects

“…For determining the complex stress-strain state in the stress concentration zone of disc rims the three dimensional finiteelement (FE) simulations have been carried out using the thermo-elasto-visco-plastic model with non-linear isotropic and kinematical hardening [2]. The deformational thermal-fatigue criterion [3][4][5], taking into account cyclic and unilaterally accumulated plastic and creep strains, is applied for the computation of the damage and the number of cycles to a crack initiation [6]. A verification of the proposed approach have been performed in comparison with results of full-scale tests with overloading up to a fracture [1,7,8].…”