Anti-fatigue Design Of Welded Structure Based On 30t Axle Load Dual Tub Gondola Body

Economic development in some areas has been restricted by the capability of railway freight transportation. It is urgent to develop a heavy axle-load wagon with heavy haul and light weight. Fatigue crack at welded area of bolster has been found during overhaul in the heavy haul railway truck that had been put into use, and become a significant threat to the safe operation of heavy vehicles. Therefore, fatigue life prediction of 30t axle load dual tub gondola body is studied at early stage in order to improve service life of heavy axle load wagon.Firstly, the finite element model for static strength analysis is established based on the structure of 30t axle load dual tub gondola; nine computation loads are determined according to AAR Standards and TB requirements; the design requirements in static strength and stiffness could be met in the final plan after contrast of multi-scheme finite element calculation.Then, fatigue life at key parts of 30t axle load dual tub gondola is predicted according to nominal stress method. Load spectrums of body structure fatigue life prediction come from center plate load spectrum, coupler load spectrum and side bearing total load spectrum of 90.7t high side gondola, body torque load spectrum of 90.7t hopper wagon,which picked from AAR Standards, fatigue property parameter of evaluate site is selected from BS standards. The result of fatigue life prediction shows: the design requirements of the fatigue life of the car body can be achieved, bolster stiffener and weld at side beam are relatively weak positions.Lastly, the latest structure stress method of American ASME Standard is used for stress concentration calculation and fatigue life prediction at body weld of 30t axle load dual tub gondola. A finite element model for stress concentration calculation and fatigue life prediction is established on base of the structure of 30t axle load dual tub gondola and welding flow chart, structure stress distribution at weld of vehicle body can be obtained by extract nodal force of each load according to finite element analysis result of the body under vertical load, longitudinal load, torsion load and horizontal load, fatigue life at body weld of key parts is predicted on the basis of vertical center plate load spectrum, longitudinal load spectrum, torsion load spectrum and side bearing spectrum from AAR Standard. The results show that: accumulative damage value is slightly higher both at weld end between cross beam and center sill, and weld between beam lower cover and end of side beam, which does not reach the design qualification. It is proposed to do necessarily process for treatment at aforesaid position, and control the quality of welding process strictly. Comparison of fatigue life prediction between nominal stress method and equivalent structure stress method shows: stress concentration distribution at weld could not be obtain, and fatigue property parameters at welded joint could hardly selected by the former; equivalent structure stress equation is derived from fracture mechanics, and so the latter has a relatively higher value after comprehensive consideration of factors affecting fatigue assessment.