ANALYSIS ON THE CAUSES TO CRACKING OF L-B COMPOSITE BRAKE BEAM AND SUGGESTIONS

The integrated analysis of crack failure for L-B Composite Brake Beam Bar Flange Slab was made by means of SEM, microscope and chemical analysis. The results showed that the essential reason due to early crack on brake beam safety chains bracket is unsuitable welding technology. In concretely, no preheating to brake beam welding zone before welding or much high welding heat input caused higher residual tensile welding stress and disadvantage microscopic structure; no post heating after welding to removing residual welding stress and improve disadvantage microscopic structure; no sanding after welding to removing macro/micro welding defect of the weld toe zone. All the above factors and unqualified mechanical properties and chemical constitution caused the cracking of brake beam.