The rule for assessing the lightening of welded frame of Bo-Bo locomotive
bogie is proposed. Based on the analysis result of the frame s whole structure with finite
element method, the stress distribution in the lateral butt-weld on the bottom cover
plate of the side beam of the frame is analyzed with boundary element method. The
stress concentration due to the incomplete penetration root of the weld is discussed, and
a feasible scheme to reduce the stress in the tensile butt-weld is presented. A comparison
between the results of the theoretical analysis and fatigue intensity tests shows that the
stress distribution in the weld region can be calculated accurately with boundary element
method.