Service strength of welded aluminium structures. Influences and validation
Increasing usage of welded aluminium structures and specific field experience require one to summarize the state of the art related to the procedures for the assessment of their service strength. The demands for light weight design and weight saving, especially for the components of transport means (cars, trains, ships, etc.), make it necessary to go to the limits of assumed service strength and caused spectacular and expensive service failures. The main cause for these failures is mostly inadequate components design and service strength validation. In this paper the main influences on the service strength of welded aluminium structures are presented and discussed. The procedures to validate the service strength of welded structures must be based on stresses generated by operational loads and on the structural strength, which depend as well on the behaviour under extreme monotonic load as on the fatigue under operational cyclic loads. Therefore the reliable design (shaping and dimensioning) has to include- - -the stress analysis (numerical or experimental) by which the nominal (global) stress in the critical components sections that is decisive for components fracture behaviour, as well as the local stress (structural stress or hot-spot stress or notch stress) that is decisive for components fatigue behaviour to the initial crack, - the validation of these stresses in relation to the maximum allowable values (structural strength). The examples of specific data and main parameters of the structural strength - structural yield point and fatigue strength - which depend on the shape (type) of weld-joint, material and loading conditions, are treated and presented. Finally the procedure to estimate the structural durability under operational loading, and the influencing parameters to carry out the validation, are described.