# A Novel Structure of Rubber Ring for Hydraulic Buffer Seal Based on Numerical Simulation  
[PERSON]  
Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; [PERSON]DRESS]  
[PERSON]  
reviewed the widely used constitutive models of rubber materials in FEA, and pointed out that M-R model is suitable for small deformation and medium deformation [5]. [PERSON] pointed out that the seal structure is axisymmetric, so the two-dimensional axisymmetric model can be used for the numerical calculation of the seal ring. Also, the two-dimensional axisymmetric model of the seal structure was established by using ANSYS software, and the validity of the two-dimensional axisymmetric numerical model is verified by the FEA of the sealing surface and the back support structure of the roller bit bearing seal [6; 7]. [PERSON] established five contact pairs and analyzed the state of contact surface with the form of pseudo element. By comparing the numerical results with the experimental data, [PERSON] pointed out that it is feasible to simulate the contact pressure distribution of bearing seal structure through contact pairs [8]. The FEA method is an effective method to study the sealing performance of the rubber ring [9]. The most important factor in the design of hydraulic buffer seal structure is the configuration of the rubber ring. The configuration of the rubber ring determines the contact peak pressure and contact length, both of which are used as the evaluation index of seal performance. [PERSON] analyzed the influence of geometric shape on the deformation of rubber structure, and pointed out that different structural shapes have a great influence on the sealing performance of the rubber ring [10]. A lot of work has been done in the structural design of rubber sealing ring, and some new rubber sealing rings have been used in buffer seal, such as D-ring, T-ring, U-ring, X-ring, Y-ring, etc. The geometry of D-ring, which is designed to increase the contact length between groove and D-ring, could be seen as a half of O-ring. [PERSON] compared D-ring with O-ring in the sealing performance, and concluded the sealing performance of D-ring is better than O-ring from the perspective of contact peak stress. Also pointed the disadvantage of extrusion through buffer gap for D-ring [11]. [PERSON] analyzed the extrusion of D-ring with hydraulic pressure 5.89 MPa, and concluded the extrusion is likely to cause sealing failure. The sealing disadvantage of D-ring is laid on stress concentration at corner under static sealing and extrusion through gap under dynamic sealing [12]. The geometric shape of X-ring is benefit for dynamic condition by decreasing friction. [PERSON] showed the higher contact stress of X-ring than O-ring under certain research condition, but the ultimate pressure of extrusion is only 3.92 MPa for X-ring [13]. The disadvantage of X-ring is the contact length under low pressure, which is harmful to the sealing of the rubber ring [14]. Furthermore, the X-ring is not suitable for landing gear buffer, due to the limitation of hydraulic pressure. The sealing characteristic of Y-ring relied on the surface of lips to coupling, as a lip-type rubber ring. [PERSON] analyzed the effect of hydraulic pressure on Y-ring sealing performance, and found out the location of the maximum stress and largest deformation area according to seal failure criterion [15]. The disadvantage of thresh tendency under high pressure is a weakness for Y-ring. The type of O-ring is widely used in hydraulic buffer of landing gear, due to the stability of contact length and pressure [16]. According to test data on 21 joint seals, [PERSON] concluded that the properties of joint seals are differed by geometry shape and manufacture method [17]. As the seal of hydraulic buffer for landing gear, the disadvantage of lower contact pressure at groove side than piston rod side still needs to be modified for O-ring during assemble process [18].