numero25

E. Maggiolini et alii, Frattura ed Integrità Strutturale, 25 (2013) 117-123; DOI: 10.3221/IGF-ESIS.25.17 122 Figure 7: σ eff,IG /σ eff,int function of filled radius and notch opening angle 2α. M ESH I NFLUENCE further problem regarding the numerical assessment of non-local effective stress is the sensibility of results to the elements dimension. Taking the 120° geometry and through mesh analysis, it is possible to look at the relationship between the maximum element size and errors that occur. Tab. 4 d shows the dimension of the element at the notch tip. In this investigation “Plane 42” elements in Ansys and “quadrangular” elements in Comsol, were used. Mesh Comsol Ansys Error d/c σ eff,IG σ eff,int σ eff,sum σ eff,int VS σ eff,sum 4 7.44 6.66 7.39 10.93% 3 7.53 6.67 7.58 13.74% 2 7.57 6.66 6.84 2.73% 1 7.65 6.65 6.70 0.76% 0.5 7.67 6.64 6.70 0.90% 0.25 7.67 6.64 6.70 0.96% 0.1 7.67 6.64 6.70 0.97% Table 4: Error occurs in the mesh analysis. H OW TO ccording to a previous theoretical framework, it is possible to sketch a procedure for effective non-local effective stress assessment by means of a general FE numerical tool. First of all, it is suitable to make a subdomain around the interested zone: this makes it easier to create a good quality mesh (element size close to c/2) and to export the needed results and no more. After that, it is only necessary to make an appropriate model and to export the nodal data: first principal stress of stress analysis, nodal coordinates, and reaction solutions under uniform loading. The Eq. (2) defines “ψ” and the data are combined into the Eq. (4), N is the reaction solution and σ eq is the first principal stress. T HREE - DIMENSIONAL PROBLEM he applicability of the proposed approach was also verified for a three-dimensional component. The investigated structural detail is a welded joint depicted in Fig. 9. The obtained results are reported in Tab. 5. In this first application, the errors are slightly higher, however, it remains acceptable if used for design strength assessment. 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 0 1 2 3 4 5 6 7 8 9 10 σ eff,IG /σ eff,int ρ/c 0° 30° 60° 90° 120° 135° A A T