Issue 41

F. Chebat et alii, Frattura ed Integrità Strutturale, 41 (2017) 447-455; DOI: 10.3221/IGF-ESIS.41.56 447 Fatigue assessment of steel rollers by means of the local energy F. Chebat, M. Cincera Rulli Rulmeca S.P.A., Via A. Toscanini, 1, I-24011 Alme’ (Bergamo) – Italy S.M.J. Razavi, F. Berto, T. Welo Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology (NTNU), Norway javad.razavi@ntnu.no , filippo.berto@ntnu.no A BSTRACT . This paper aims to analyses the fatigue behavior of steel rollers using the average strain energy density (SED) criterion. Considering the variability of the V-notch opening angle, a simple scalar quantity, i.e. the value of the strain energy density averaged in a control volume surrounding the notch tip, has been introduced to overcome the complexities in failure assessment of this component. The strain energy is obtained using close form solutions based on the relevant Notch Stress Intensity Factors (NSIF) for modes I, II and III. Referring to the conventional arc welding processes, the radius of the control volume is carefully identified with reference to conventional arc welding processes being equal to 0.28 mm for welded joints made of steel. In this paper firstly the employed methodology for the fatigue assessment is described and then the first synthesis of fatigue data by means of local SED for a specific geometry is shown. K EYWORDS . Notch Stress Intensity Factor; Welded Joints; Strain Energy Density; Fatigue Strength. Citation: Chebat, F., Cincera, M. Razavi, S.M.J., Berto, F., Welo, T., Fatigue assessment of steel rollers by means of the local energy, Frattura ed Integrità Strutturale, 41 (2017) 447-455. Received: 12.05.2017 Accepted: 24.05.2017 Published: 01.07.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION he geometry of weld fillet cannot be exactly defined due to variation of different parameters such as length of lack of penetration, root radius, toe radius and bead shape from joint to joint even in well-performed operations [1-5]. The weld toe radius decreases in presence of the local heat concentration during the welding process and it is considerably small for automated high-power processes such as laser beam welding. According to the small values of toe radius in conventional arc welding [6], the weld toe is considered as a sharp notch and using the NSIF approach the local stress can be obtained [6,7]. Considering the large opening angles of the weld toe, the stress component regarding to mode II is non-singular and the fatigue behaviour can be assessed only by use of mode I NSIF [7]. Based on the relevant theoretical stress concentration factors an evaluation of different steel welded joints can be conducted considering a fictitious notch T