Consideration of random loading processes and scatter of fatigue properties for assessing the service life of welded bus bodyworks

• Published in: International journal of fatigue 2021-10, Vol.151, p.106324, Article 106324
• Main Author: Kepka, Miloslav
• Format: Article
• Language: English
• Subjects: Aluminum base alloys; Automobiles; Bus bodywork; Buses (vehicles); Design stress spectrum; Electric vehicles; Fatigue damage calculation; Fatigue life assessment; Fatigue life distribution function; Fatigue tests; FEM model of bodywork; High strength alloys; High strength steels; Materials fatigue; MBS model of vehicle; Nodes; Permissible maximum stress amplitude; S-N line; Scattering; Service life assessment; Stainless steels; Stress-time history; Stresses; Structural steels; Trolley-buses; Undercarriages; Variable amplitude loading; Weight reduction; Welded bodywork node
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2021.106324

As in the field of passenger cars, the development of a new bus (trolleybus, electric bus) includes computational and experimental activities: CAD - MBS - FEM - stand tests - measurements with prototypes - fatigue life calculations. Current challenges include the rise of electromobility and battery-powered electric buses, which open up new fields of research. Heavy batteries significantly change both the vehicle's dynamics and the stresses in the bodywork and undercarriage frame. The main structures of bus bodyworks are welded from thin-walled profiles. In addition to conventional structural steels and, in the case of some manufacturers, also aluminium alloys, stainless steels and high-strength steels are beginning to be widely used. If a manufacturer decides to develop a conceptually new vehicle, it initially does not have the exact input information necessary to assess the strength and fatigue life of a new bodywork. Therefore, the challenge is to analyse the experience from the development and operation of the previous generation of vehicles and to introduce new research methods. One of these trends is to estimate the service fatigue life and future reliability of the bodywork at an early stage of its development. The paper briefly describes the process of development of a new bus bodywork and summarizes the general assumptions for assessing the fatigue life of welded bodywork nodes based on the concept of nominal stresses. In several specific case studies, the variable amplitude loading and the scatter of fatigue properties of welded bodywork nodes are considered.