Issue 41

F. Chebat et alii, Frattura ed Integrità Strutturale, 41 (2017) 447-455; DOI: 10.3221/IGF-ESIS.41.56 454 experience fatigue failure starting at the level of the weld root. A detail of the weld root is shown in Fig. 1b, where the lack of penetration length is indicated as c . The rollers have been modelled by using the finite element method combined with three-dimensional analyses. The procedure for evaluating the local parameters in the zone close to the lack of penetration at the weld root has been described in the paper showing the low sensitivity of the model to the length of the lack of penetration. The detailed procedure for evaluating the SED in the control volume surrounding the crack tip in the weakest point of the roller has been summarised [27]. Some fatigue tests from two different geometries belonging to the family of rollers called PSV4 from Rulmeca production have been carried out and summarised here by means of local SED. It has been proved that the scatter band Δ W - N (strain energy range – number of cycles to failure), summarising about 1200 fatigue data from welded joints with the majority of failures originated from the weld toes, can be successfully applied also to welded joints with failures from the weld roots and in particular to the considered rollers geometry. R EFERENCES [1] Zou, L., Yang, X., Tan, J., Sun, Y., S-N curve modeling method of aluminum alloy welded joints based on the fatigue characteristics domain, Frattura ed Integrita Strutturale, 11(40) (2017) 137-148. [2] Abe, T., Akebono, H., Kato, M., Sugeta, A., Fatigue properties and fracture mechanism of load carrying type fillet joints with one-sided welding, Frattura ed Integrita Strutturale, 10(35) (2016) 196-205. [3] Tsutsumi, S., Morita, K., Fincato, R., Momii, H., Fatigue life assessment of a non-load carrying fillet joint considering the effects of a cyclic plasticity and weld bead shape, Frattura ed Integrita Strutturale, 10(38) (2016) 244-250. [4] Radaj, D., Design and analysis of fatigue resistant welded structures, Abington Publishing, Cambridge (1990). [5] Taylor, D., Barrett, N., Lucano, G., Some new recent methods for predicting fatigue in welded joints, Int. J. Fatigue, 24 (2002) 509-518. [6] Yakubovskii, V.V., Valteris, I.I., Geometrical parameters of butt and fillet welds and their influence on the welded joints fatigue life, International Institute of Welding, Document XIII-1326-89 (1989). [7] Dunn, M.L., Suwito, W., Cunningham, S., Fracture initiation at sharp notches: Correlation using critical stress intensities, Int. J. Solids Struct., 34 (1997) 3873-3883. [8] Lazzarin, P., Tovo, R., A Notch Intensity Approach to the Stress Analysis of Welds, Fatigue Fract. Eng. Mater. Struct. 21 (1998) 1089-1104. [9] Ayatollahi, M.R., Razavi, S.M.J., Chamani, H.R., Fatigue Life Extension by Crack Repair Using Stop-hole Technique under Pure Mode-I and Pure mode-II Loading Conditions, Procedia Eng., 74 (2014) 18–21. [10] Ayatollahi, M.R., Razavi, S.M.J., Chamani, H.R., A numerical study on the effect of symmetric crack flank holes on fatigue life extension of a SENT specimen, Fatigue Fract. Eng. Mater. Struct. 37(10) (2014) 1153-1164. [11] Ayatollahi, M.R., Razavi, S.M.J., Yahya, M.Y., Mixed mode fatigue crack initiation and growth in a CT specimen repaired by stop hole technique, Eng. Fract. Mech. 145 (2015) 115-127. [12] Ayatollahi, M.R., Razavi, S.M.J., Sommitsch, C., Moser, C., Fatigue life extension by crack repair using double stop-hole technique, Mater. Sci. Forum, 879 (2017) 3-8. [13] Razavi, S.M.J., Ayatollahi, M.R., Sommitsch, C., Moser, C., Retardation of fatigue crack growth in high strength steel S690 using a modified stop-hole technique, Eng. Fract. Mech., 169 (2017) 226–237. [14] Jiang, Y., Feng, M., Modeling of fatigue crack propagation, J. Eng. Mater. Technol., 126 (2004) 77-86. [15] Berto, F., Lazzarin, P., Recent developments in brittle and quasi-brittle failure assessment of engineering materials by means of local approaches, Mater. Sci. Eng. R, 75 (2014) 1–48. [16] Ferro, P., The local strain energy density approach applied to pre-stressed components subjected to cyclic load, Fatigue Fract. Eng. Mater. Struct. 37 (2014) 1268–1280. [17] Radaj, D., State-of-the-art review on the local strain energy density concept and its relation to the J-integral and peak stress method, Fatigue Fract. Eng. Mater. Struct., 38 (2015) 2–28. [18] Radaj, D., Berto, F., Lazzarin, P., Local fatigue strength parameters for welded joints based on strain energy density with inclusion of small-size notches, Eng. Fract. Mech., 76 (8) (2009) 1109-1130. [19] Lazzarin, P., Campagnolo, A., Berto, F., A comparison among some recent energy- and stress-based criteria for the fracture assessment of sharp V-notched components under mode I loading, Theor. Appl. Fract. Mech., 71 (2014) 21- 30. [20] Lassen, T., The effect of the welding process on the fatigue crack growth. Welding J. 69, Research Supplement, (1990) 75S-81S.