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1997
Conference Paper
Title
Betriebsfestigkeit von Schweißverbindungen unter mehrachsigen Spannungen mit variablen Amplituden
Other Title
Fatigue behavior of welded joints under combined multiaxial variable amplitude loading
Abstract
Flange-tube as well as tube-tube joints from fine grained steel StE 460 with unmachined welds were investigated under biaxial constant and variable amplitude loading (bending and torsion) in the range of 10(exp 3) to 5 x 10(exp 6) cycles to crack initiation and break-through, respectively. In order not to interfere with residual stresses they were relieved by a heat treatment. In-phase loading can be treated fairly well using the conventional hypotheses (von Mises or Tresca) on basis of nominal, structural or local strains or stresses. But the influence of out-of-phase loading on fatigue life is severely overestimated if conventional hypotheses are used. However, the introduced hypothesis of the effective equivalent stress leads to fairly well predictions. Herefore, the knowledge of local strains or stresses is necessary. They are determined by boundary-element analyses in dependency of weld geometry. This hypothesis considers the fatigue-life reducing influence of out-of-phase loading by taking into account the interaction of local shear stresses acting in different surface planes of the material. Further, size effects resulting from weld geometry and loading mode were included. Damage accumulation under a Gaussian spectrum can be assessed for in- and out-of-phase combined bending and torsion using an allowable damage sum of 0.35.
Author(s)
Conference
Language
German
Keyword(s)
Apparatebau
Betriebsfestigkeit
constant amplitude loading
damage accumulation
damage sum
displaced phase loading
Einstufenbeanspruchung
equipment construction
fatigue life estimation
fatigue strength
Lebensdauerabschätzung
Meerestechnik
mehrachsige Beanspruchung
Mehrstufenbeanspruchung
metal
Metall
multiaxial loading
offshore technology
phasenverschobene Beanspruchung
random loading
Rohrverbindung
Schadensakkumulation
Schadenssumme
Schweißverbindung
Schwingfestigkeit
Spannung
stress
structural fatigue strength
test
tube joint
variable amplitude loading
Versuch
welded joint
Woehler curve
Wöhlerlinie
zufallsartige Beanspruchung