Crack Analysis And Improved Design Of The Hugging-Bearing Box Body For The SS7-Type Electric Locomotive

Presented is the theory and methods on the strength analysis, model analysis and transient respond of mechanical components by means of the Finite Element Method (FEM). Introduced is the install, bearing loads, structural features and service in electric-transmission locomotives. Summed up is the process of the crack treatment on spot, the theory analysis and the design improvement of the hugging-bearing box body(HBBB) for SS7-type electric locomotive. Treatment on spot is to drill holes to stop cracking and determine service period according to the length of crack. The crack analysis is divided into three steps, measurement and statistics analysis, section electron microscopic scan and FEM analysis. Analysis results of histogram statistics and section electron microscopic scan technique, are that fracture feature of the cracks of the HBBB is similar and the crack is multi-source strain fatigue one. Internal defects of the cast, such as impurities, gas holes, etc, are the main causes for early cracks. The contrast analysis of static strength, model and transient respond on three structures with FEM proves that geometrical stress concentration in partial area has influence on early crack, also. Design improvement is in three stages partial, geometrical stress concentration improvement, pure casting technology improvement and a forge-weld box body design. Prolonging the fatigue life of the HBBB for the SS7-type electric locomotive relies on improving cast process and cast quality. Under the condition that the existing technology in the Works can't be heightened in a short period, the forge-weld HBBB is an efficient way. Therefore, the two schemes on the forge-weld HBBB are designed and trial-manufactured in the Works. They have passed the product appraisal by Acceptance Office of the Ministry of Railway and the experts of the Works. Afterwards, they are installed on the locomotive. No cracks have happened since they are used,which verifies that the way of the analysis and the improvement is correct and effective. Put forward is the future plan on the improvement of the forge-weld HBBB, which is helped to research and design of the HBBB for the SS7-type electric locomotive and other electric-driving locomotives in the future.