The Analytics On The Facture Of The Bolts Connecting The Axle Box And Motor Of The Locomotive HXD1C

The fracture problem of the bolts is widespread in engineering applications, which is dangerous for social production and property, and also the personal safety. This paper is all about the10.9high strength bolts’fracture problem, the bolts involved are assembled in the Locomotive HXD1C, where the bolts are used to connecting the axle box and the motor. To find the reasons of the fracture problem, the analysis of the force of the bolts, fitted positions, assembling process and the metallographic test methods are adopted. Improving the design and manufacture process of the bolts to ensure that the bolts will work normally and the locomotives will run safely.The main contents include:Introduction to the requirements and application of the material of the high strength bolts, and stress on the forms of destruction and the characteristics and analysis methods used to find reasons of the destruction. This part is the foundation of the research and analysis behind; the loads of the bolts, the bolts’hole size and accuracy, the final operation of the torque on the bolts in the assembly processing are analysed, which are meeting the regulatory requirements, the conclusion can be made that the damage of the bolts is not due to the unreasonable loads. By macro-and micro-analysis of the fracture position, brittle fracture characteristics are found, combined with the bolt breaking characteristics of the time delay, we conclude that the bolts’failure is because of the Hydrogen embrittlement fracture; Through the physical and chemical inspection (including chemical composition analysis, mechanical testing, metallographic test, etc.), the material and mechanical properties of the bolts are proved to be meeting the requirements of national standards, but bolt fillet cracks begin from the bottom of small corrosion, which occur before Blackening processing, which is found in the metallographic examination, over-pickling is took place during the manufacturing process of the bolts, so the bolts’surface absorb hydrogen leading to Hydrogen embrittlement fracture.As, the reason is found, then the manufacture process of the bolts must be improved:by increasing the diameter of the bolt block and the diameter of bolt fillet, and the process of absorption of the hydrogen is added, so the problems of the bolts’fracture are completely solved. After the manufacture process is improved the bolts on the locomotives never fracture again,and the normal running of the locomotive is ensured.The analysis methods of the bolts’ fracture used in this paper is a good reference to solve this problem similarly and have a great practical value in society.