Issue 48

B. Chen et alii, Frattura ed Integrità Strutturale, 48 (2019) 385-399; DOI: 10.3221/IGF-ESIS.48.37 387 F ATIGUE STRENGTH ANALYSIS OF BOGIE FRAME BASED ON DETERMINISTIC MODEL FE model of the bogie frame n this paper, the analyzed bogie is a metro bogie (Fig. 1(a)). The numerical analysis by the FEM is performed to evaluate the fatigue strength of the bogie frame. A study conducted by Lu shows that the calculation results of the shell model without considering weld details are more conservative than those of the shell model considering weld details. It is feasible to adopt the conservative method of seamless structure modeling in engineering design. [14]. Therefore, the bogie which is modeled by shell and solid model, is given in Fig. 1(b). The bogie frame is modeled using beam188, COMBIN14, shell181 and solid185 elements. It is meshed to have 730,423 elements, including 123,755 triangular and quadrilateral shell elements and 606,659 tetrahedral and hexahedral solid elements. Considering the boundary conditions of the bogie frame for the primary suspension, the spring elements COMBIN14 are established and the stiffness of the elements is the same as the primary suspension. The material of the bogie frame is S355J2(H) and Q345D (yield strength=355MPa and 355MPa). Definition of the load conditions In conventional load cases, fatigue strength analysis is performed based on the UIC standard. The main in-service load case is designed to verify the absence of any risk of fatigue cracks that could occur under the combined effect of the main forces encountered during service. Therefore, in this study, six fatigue conditions are calculated according to UIC615-4 and EN13749 standard. Tab. 1 and Tab. 2 show the fatigue conditions for each load. The twisting loads of 1 and 2 working conditions are 11 mm, 3 and 4 working conditions are -11 mm. Load case Air spring vertical and right Air spring vertical and left Air spring horizontal Lateral stop Longitudinal Gear box hanger Front/After Braking Front/After 1 107.5 83.4 16.1 62.6 52.3 -23.8/23.8 -8.8/8.8 2 155 131.1 16.1 62.6 52.3 -23.8/23.8 -8.8/8.8 3 83.4 107.3 -16.1 -62.6 -52.3 23.8/-23.8 8.8/-8.8 4 131.2 155 -16.1 -62.6 -52.3 23.8/-23.8 8.8/-8.8 Table 1 : Load cases for operational loads (kN) Load case Air spring vertical and right Air spring vertical and left Vertical inertia of motor Transverse inertia of motor Longitudinal inertia of motor Gear box hanger front/after Vertical inertia of brake Transverse inertia of brake Longitudinal inertia of brake 5 119.3 119.3 -20.8 -20.8 -20.8 -5.2/-5.2 -3.9 -3.9 -3.9 6 119.3 119.3 31.2 20.8 20.8 7.8/7.8 5.9 3.9 3.9 Table 2 : Load cases for inertial load (kN) Tab. 3 shows the mechanical properties of the materials used in the bogie frame. The material of steel plate and primary spring seat is S355J2(H) and the cross beam and traction seat are made from Q345D. Type Material type Yielding strength S=1 Yielding strength S=1.1 Yielding strength Bogie frame Steel plate S355J2(H) 355 （≤ 16mm ） 355 322 Primary spring seat 345 （ >16mm ） 345 313 Cross beam Q345D 345 345 313 Traction seat Table 3 : Material properties of the bogie frame (MPa) I