## 1 Introduction  
Hydro-pneumatic suspension is widely used in military vehicles, mining trucks, and construction machinery vehicles due to its nonlinear variable stiffness characteristics and nonlinear damping characteristics [1; 2]. The hydro-pneumatic spring is the core component of hydro-pneumatic suspension; it uses inert gas as the elastic medium, with oil to transmit pressure, and through the compressibility of elastic gas and the damping characteristics of hydraulic oil, adapting to the various use conditions of the vehicle [3; 4; 5; 6], the reciprocating linear movement of hydro-pneumatic springs and high-pressure impact imposes higher requirements on the sealing structure. The sealing form of a hydro-pneumatic spring is mainly divided into static and dynamic seals: the static seal is composed of an O-ring and retaining ring, located between the end cover and the cylinder barrel; the dynamic seal consists of a GS sealing ring, which is located between the end cap and the piston rod. The structure of the GS sealing ring is similar to the structure and principle of the Steseal seal and has the advantages of low friction, no crawling, a small starting force, high-pressure resistance, and a simple groove structure [7]. Hydro-pneumatic springs often work under high pressure and alternating load conditions, which easily cause seal damage leakage and lead to serious failure, seriously affecting vehicle performance and even causing safety accidents. Relevant studies have shown that the dynamic seal failure of hydro-pneumatic springs is the main cause of hydro-pneumatic spring failure, and the sealing performance of the GS sealing ring directly determines the service life of a hydro-pneumatic spring [8]. Therefore, studying the sealing performance change law of GS sealing rings under different working conditions can provide an effective theoretical basis for the design of the sealing structure of hydro-pneumatic springs. At present, many scholars have conducted in-depth research on hydro-pneumatic springs, but most of these studies have focused on the damping and stiffness characteristics of hydro-pneumatic springs [9]; there is a relative lack of research on the sealing performance and sealing structure of hydro-pneumatic springs, and the design of related sealing structures is mainly based on experience and lacks theoretical guidance. [PERSON] [10; 11] established the mathematical model of hydro-pneumatic spring fluid, derived the leakage flow formula of Steseal, and, combined with the finite element simulation method, analyzed the factors affecting the leakage amount of the Steseal seal and the main reasons for the seal failure of the hydro-pneumatic spring from the aspects of seal lubricity, temperature range adaptability, and oil-fluid compatibility based on engineering practice experience. [PERSON] [12; 13] analyzed the main failure modes and mechanisms of hydro-pneumatic springs, proposed a fault identification and prediction framework for the faults of air leakage, and verified the feasibility of the method with experiments. Some scholars have chosen a hydraulic actuator, which is similar to the hydro-pneumatic spring reciprocating seal structure, as the object of their research. [PERSON] [14] found through a comparative analysis that the main reason for the actuator seal failure is the wear of the sealing ring; the wear of the sealing ring leads to a rapid decrease in contact pressure and sealing performance. [PERSON] [15] studied the influence of actuator piston rod texture and sealing pressure on the wear of the sealing ring via numerical simulation and found that the texture of the piston rod surface had a significant effect on fluid pressure, film thickness, and contact pressure.