Analysis on fatigue behavior of water hydraulic artificial muscles under different elastic loads in underwater environment

As a novel and flexible actuator, the water hydraulic artificial muscle (WHAM) has become at the forefront of bionic robot research. In order to explore the fatigue behavior of WHAM, the lifetime of WHAM was analyzed based on the crack propagation of neoprene rubber and the S-N curve of aramid fiber. Meanwhile, WHAM's fatigue tests were carried out, and the fatigue life exceeded 56,000 cycles under the pressure of 2 MPa and the elastic load of 1030.7 N/mm. In addition, WHAM's fatigue failure is represented as the burst of the rubber tube after fiber fracture. Moreover, heavy load aggravates fibrillation that leads to severe fracture of fibrils under similar friction, and the fatigue life of WHAM is aggravatingly shortened by the coupling of fibrillation and friction. Finally, an empirical model of fatigue life was obtained, which can predict the lifetime of WHAM.