Increased accuracy of calculated fatigue resistance of welds through consideration of the statistical size effect within
- PDF / 2,187,189 Bytes
- 12 Pages / 595.276 x 790.866 pts Page_size
- 89 Downloads / 140 Views
RESEARCH PAPER
Increased accuracy of calculated fatigue resistance of welds through consideration of the statistical size effect within the notch stress concept Andreas Deinböck 1 Klaus Dilger 2
&
Ann-Christin Hesse 2 & Michael Wächter 1
&
Jonas Hensel 2
&
Alfons Esderts 1
&
Received: 5 March 2020 / Accepted: 19 June 2020 # The Author(s) 2020
Abstract The notch stress concept has been established for fatigue life calculations of welded components. One of its advantages is that the SN curve is not based on an S-N curve catalog in which the user has to identify a suitable FAT class; instead, a single S-N curve (based on modeling, failure location, and material) is used for different weld geometries. In return, however, the weld needs to be modeled in a detailed manner for finite element analysis. The evaluation of experimental fatigue results collected in a database shows a relatively high degree of scattering (low accuracy) of the strengths calculated according to the notch stress concept. With fatigue tests on different specimen geometries manufactured from the same welded base plates, a correlation between the highly stressed weld seam length and the experimentally determined notch stress strength can be observed. The fatigue strength decreases with the increasing length of the highly stressed weld seam area. The latter quantity can be calculated using the finite element simulations that are needed to determine the notch stress. The presented results are used to describe the statistical size effect as a qualitative influence and quantitative support factor that can be used within the notch stress concept to increase its accuracy. Keywords Fatigue design . Welding . Steel . Statistical size effect . Notch stress concept . Highly stressed weld seam length . Support factor
Nomenclature A Surface area A90% Highly stressed surface area c Proportionality factor F External force FATX Classification reference to S-N curve, in which x is the stress range in MPa at 2·106 cycles, according to IIW [1] ΔF Force range Recommended for publication by Commission XIII - Fatigue of Welded Components and Structures * Andreas Deinböck [email protected] 1
Institute for Plant Engineering and Fatigue Analysis, Clausthal University of Technology, Leibnizstraße 32, 38678 Clausthal-Zellerfeld, Germany
2
Institute of Joining and Welding, Technische Universität Braunschweig, Langer Kamp 8, 38106 Braunschweig, Germany
ΔF(N) m Kt kst Lref L90% Mσ N nst t V V90% σ S Δσ Δσ0 Δσ(N) Pf R TN
Force range for a certain number of cycles N Exponent of S-N curve Stress concentration factor Weibull’s exponent Reference length Highly stressed length Mean stress sensitivity Fatigue life in numbers of cycles Statistical support factor Plate thickness Volume Highly stressed volume Notch stress Nominal stress Notch stress range Modified notch stress range assessed with the statistical size effect Notch stress range for a certain number of cycles N Probability of failure Stress ratio Deviation range in direction of fatigue life
Data Loading...
