Abstract
Problems of fatigue life prediction of materials and structures are discussed in the paper. Service loading is assumed as a continuous loading process with possible discontinuous events, which are caused by various operating conditions. The damage in a material is due to a cumulative degradation process. The damaging process is then represented either by rain-flow matrices or by a fatigue damage function which is derived using some hypothesis of a fatigue failure criterion. Presented theoretical procedure enables a very effective estimation of a service life and/or reliable evaluation of residual life of any structures under various types of loading and environmental conditions. This approach creates a good basis for powerful expert systems in structural and mechanical engineering. The aim of the paper is to present briefly some results of analysis of load-bearing steel structure loads of special railway crane PKP 25/20i which was utilized in some specific ad relatively hard operating conditions. Virtual models of the structure were being used in an analysis of acting working dynamics loads influence to be able to forecast fatigue life of load-bearing of the crane jib.
Highlights
Optimization of structure design is a decisive condition for effective production
That to accelerate calculation procedures, we must have a suitable databank of operating parameters and of their influence upon a service life
If we accept some non-linear hypothesis, the rain-flow matrix should be three-dimensional, too. Having both the rain-flow matrix of loading (RML) and rain-flow matrix of damaging (RMD), we can calculate the estimation of an accumulated fatigue damage D as their scalar product [2], i.e
Summary
Optimization of structure design is a decisive condition for effective production. It is exceptionally significant in mechanical and material engineering because either economy demands or waste effects could be considerable in this case. The parameters that affect a durability of structure parts are following: operating loading, structure characteristics, material properties and environmental conditions. We must use an appropriate method to estimate a service life and dependability for each combination of the parameters. Methods that enable these objectives are created by a combination of an empirical-. The simulated loading is simultaneously transformed into closed hysteresis loops using a rain-flow method, and a damage accumulation is estimated according to failure hypotheses. That brings much more complications in comparison with procedures used for homogeneous materials
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