Abstract
In recent years, the automotive industry has emphasized not only improving fuel efficiency but also reducing overall environmental impact, aligning with the Sustainable Development Goals (SDGs). Concurrently, the electrification of vehicles has progressed, leading to an increase in vehicle weight. Suspension coil springs that make up the undercarriage of automobiles are required to be even lighter, more durable, and safer. To meet these needs, the stress level acting on the spring must be increased. On the other hand, as the applied stress and material strength increase, the risk of delayed fracture increases. Therefore, it is extremely important to accurately evaluate the delayed fracture characteristics of springs. Regarding delayed fracture evaluation methods, a survey conducted by our society's“Delayed Fracture Test Methods Research Committee”revealed that there is a strong desire in the industry to unify and standardize test methods. Delayed fracture tests using springs have issues in terms of safety and convenience, so the“Research Committee on Delayed Fracture of Springs (Phases I and II)”conducted evaluations by replacing springs with test pieces. To this end, the committee has been considering establishing evaluation methods such as test piece design, hydrogen addition method, and loading method. Based on the results of previous committees, this committee conducted confirmation tests and verified remaining issues regarding test pieces, loading methods, hydrogen addition methods, etc. necessary for standardization of delayed fracture tests. Although not covered in this report, we also investigated the organizations and processes necessary for standardization. These results will be passed on to the Spring Delayed Fracture Test Standardization Committee, which aims to standardize spring delayed fracture tests.
