On the influence of the cord angle on air-spring fatigue life

This paper presents an advanced method for the estimation of air-spring fatigue life. Furthermore, the paper presents the influence of the cord angle on the air-spring external characteristic and fatigue life.To calculate the damage and respectively the fatigue life, experimental fatigue data, together with the finite element analysis in ABAQUS is used. The research shows that cord angle has a great effect on the air-spring life and external characteristic as well. As a result of the research, it can be concluded that at larger cord angles the damage is caused by the stress that acts in the air-spring axial direction (X-stress). Therefore, the crack at cord angles greater than 40° appears on the plane that is perpendicular to the air-spring axis. On the other hand, at smaller cord angles the damage is caused by the stress that acts perpendicular to the air-spring axial direction (Y-stress). Therefore, the crack at cord angles smaller than 40° appears on the plane that is parallel to the air-spring axis. The optimal cord angle is the one that assures an appropriate ratio between X-stress and Y-stress. For the air-spring discussed in this research, the optimal cord angle is between 40° and 45°. Since a cord angle also affects the air-spring external characteristic, it has to be chosen in a way to assure an acceptable compromise between the fatigue life and the external characteristic.

► An improved model for the estimation of air-spring life is presented.
► The most critical layer of the bellows composite is the inner rubber surface.
► Cord angle has a great effect on air-spring life.
► Optimal cord angle of an air-spring discussed in this research is 40°.
► Research showed an imperfection of the method for the estimation of air-spring life.