1,721,061 research outputs found
Cycle distribution and fatigue damage under broad-band random loading
No full textFatigue damage under broad-band loading is analysed by summarizing and reviewing available analytical solutions. Relationships between fatigue damage assessment and counting methods are investigated by establishing when, in frequency domain analysis, analytical solutions of expected damage are connected with a counting procedure assumption and how this is related to the rainflow counting procedure. A new approach is also proposed for rainflow damage evaluation. This approach gives accurate approximations of fatigue damage under both broad- and narrow-band Gaussian loading; it is based on the theoretical investigation of possible combinations of peaks and valleys in Gaussian loading and on numerical fitting on several simulated broad-band loads. © 2002 Elsevier Science Ltd. All rights reserved
A damage-based evaluation of probability density distribution for rain-flow ranges from random processes
No full textA new method is proposed for the evaluation of a single Weibull distribution approximating the cycles mining out from the rain-flow counting of a random process. The founding hypothesis is a multi-modal distribution assumption, i.e. the probability density is a linear combination of several Weibull distributions; thus a simplified evaluation of a single distribution is proposed as an approximation of the most damaging part of the counted cycles instead of the most frequent range occurrences
Previsione della vita a fatica di giunzioni saldate con difetti
No full textIl presente lavoro mette in luce la possibilità di considerare i difetti nelle giunzioni saldate ad arco come semplici concentratori di tensione in aggiunta al cordone di saldatura. La procedura numerica del gradiente implicito, validata in precedenza per le giunzioni integre, viene estesa anche a giunti con disallineamenti, undercuts e porosità. La soluzione tiene conto dello sviluppo tridimensionale dei giunti e delle eventuali difettosità senza introdurre modifiche o esemplificazioni di tipo geometrico rendendo possibile anche analisi numeriche a partire da scansioni tridimensionali che riproducono nel dettaglio il cordone di saldatura
Concentrazione delle tensioni dovuta a disallineamento assiale nei giunti testa a testa
No full textNel presente lavoro viene eseguita una approfondita analisi numerica per analizzare il comportamento a fatica di giunzioni saldate testa a testa con disallineamento assiale. La procedura di calcolo è basata sul metodo del gradiente implicito attuata con le stesse modalità proposte in precedenza per lo studio delle giunzioni saldate ad arco. Viene presentata un’analisi di tipo parametrico al variare dell’entità del disallineamento assiale nella giunzione fornendo dei diagrammi di sintesi utili per il calcolo della resistenza a fatica. Infine, è stato eseguito un confronto con dati sperimentali tratti dalla letteratura di provini saldati testa a testa sollecitati a fatica e caratterizzati da tre diversi livelli di disallineamento assiale. I dati sperimentali sono relativi a provini in acciaio S1100.This paper reports a detailed numerical analysis of the fatigue strength of butt-welded joints with axial misalignment by applying the implicit gradient method. The numerical procedure is implemented similarly to a previous proposed investigation on the arc welded joints. A parametric analysis is proposed by changing misalignment type and quantity and providing some diagrams useful for the fatigue strength assessment. Finally, the paper shows an experimental comparison between the numerical assessment and the experimental fatigue data taken from the literature. The experimental data are some fatigue tests on welded joints made of steel S1100 and characterized by three different levels of axial misalignment
Fatigue in Al casting alloys: metallurgical aspects
No full textOverview of the role of microstructure and defects in controlling fatigue bahaviour of cast aluminium alloys
On fatigue damage assessment in bimodal random processes
No full textRainflow fatigue damage in bimodal Gaussian processes is discussed. Some methods specifically developed for bimodal processes (e.g., single-moment, Jiao–Moan, Sakai–Okamura and Fu–Cebon method) are compared with the Tovo–Benasciutti method, a new approach valid for the broader class of wide-band processes. Further, an improvement of the Fu–Cebon method is also proposed. Numerically simulated bimodal random processes are used to compare the accuracies of all methods and to find the optimal range for their applicability. The single-moment, the modified Fu–Cebon and the Tovo–Benasciutti methods are seen as the most accurate over a wide combination of bimodal spectra
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