On the use of the peak stress method to assess the linear elastic and the fatigue notch factors of notched components under tension

Abstract

A simple method is proposed which allows the theoretical stress concentration factor at a rounded notch tip to be assessed from the fictitious stress value arising at the tip of the corresponding pointed V-notch. Such a stress value suffices to be determined by a finite element analysis carried out using a mesh pattern with a constant average element size, d, strictly related to the actual root radius, , and the opening angle, 2, of the radiused notch. The relevant expression linking d to  and 2 is obtained in closed form and the accuracy of the proposed method is discussed versus the results of a number of FE analyses carried out on notched plates under tension. \ud Eventually, the possibility of using the peak stress directly as a strength parameter is explored, and an example related to the fatigue strength of welded joints is provided to support this idea

Energy‐based evaluation of the stress concentration factor with highly non‐regular coarse meshes: Theoretical formulation and practical validation

“…The ratio σ COARSE peak /σ FINE max is also plotted in Figure 10, where it is evident that only when d LOC /ρ is lower than 0.5 the accuracy of σ COARSE peak becomes acceptable, whereas for larger d LOC /ρ ratii the accuracy of σ COARSE peak is very poor, with an error strictly dependent from the mesh size. In order to conclude this section, it is worth of mentioning that recently it has been proposed an extension of the conventional PSM to rounded notches 16 to assess the theoretical stress concentration factor at the tip of rounded notches under tension loading. The method is based on the use of the fictitious stress value evaluated at the tip of the corresponding pointed V-notch.…”

“…However, under particular circumstances, rough meshes can be effective in assessing local stress field parameters. For example, Meneghetti and co-authors recently developed the Peak Stress Method (PSM) [11][12][13][14][15][16] that allows one to quickly calculate Notch Stress Intensity Factors (NSIFs) at pointed V-notches or weld toes and roots using the nodal stresses at the notch tip as obtained from FE models with rough meshes characterized by elements of uniform size. This method, which was also extended to determine the theoretical stress concentration factor at a rounded notch tip, 16 requires the numerical calibration of a certain coefficient of proportionality, K Ã FE , which depends on the loading mode and the type of element used in the specific case.…”

“…In both cases irregular and coarse meshes were used, without hampering the overall accuracy in the NSIFs evaluation. This last-mentioned development of the approach is particularly advantageous, since accurate results can be obtained without any need of intelligent meshing strategy (such as that required to draw a circular volume as in Lazzarin's approach 17,18 ) nor the numerical calibration of any specific coefficient is required (as it happens, instead, for the PSM [11][12][13][14][15][16] ).…”

Analytical study on the mode III stress fields due to blunt notches with cracks

“…With the aim to determine an analytical solution for the SIF, K III , Equation 31 can be re-written close to the crack tip, where x ≈ x A + ε with ε much smaller than x A , so that…”

“…As a final comment, we would like to mention that modern engineers and practitioners are necessarily influenced by developments in numerical methods, which allows the estimation of local stress parameters with a reduced computational cost (see for example Lazzarin et al and Meneghetti and Zappalorto 30,31 ). However, numerical methods can only provide sparse data points.…”