Due to its superior corrosion resistance and low coefficient of friction, polytetrafluoroethylene (PTFE) is extensively used in the aerospace, machinery, chemical, and pharmaceutical industries. However, PTFE components encounter complex alternating stresses, resulting in ratchet and creep, which will affect the component’s reliability. It is therefore necessary to clarify the PTFE’s resistance to ratchet and creep. In this paper, uniaxial ratchet and tensile creep experiments were conducted at five temperatures on a PTFE dog-bone tensile specimen. At various temperatures and stress levels, the effects of average stress and stress amplitude on the cyclic plastic behavior of PTFE were investigated. It is demonstrated that the ratchet strains and strain rates at 23 °C are greater than those at 50 °C. The reason for this is that the PTFE material exhibits different crystal states at these two temperatures. At temperatures above 50 °C, the ratchet strain and ratchet strain rate increase with temperature. At temperatures above 100 °C, the ratchet strain and ratchet strain rate of PTFE materials increase more rapidly due to the glass transition. By analyzing the creep strain and ratchet strain of specimens subjected to varying levels of average and amplitude stress, it was discovered that the creep strain and ratchet strain caused by the average stress under the same stress increment were greater than those caused by the amplitude stress.

Process industries often use B-ring self-tightening sealing structures and rely on interference assembly to meet the initial sealing requirements. Therefore, determining reasonable B-ring material, size and interference is crucial to ensure the sealing performance of the structure. In this paper, based on elastic deformation analysis, the deformation co-ordination equation of a B-ring sealing structure was established, and a sealing contact pressure calculation formula was obtained, with discussion of the main factors affecting sealing performance. With the finite element method, transient temperature field analysis was carried out for startup and shutdown load cases, and contact analysis was carried out for interference assembly, startup and shutdown. Based on the evaluation criteria of sealing performance with proposed sealing rate and leakage parameters, the effects of material properties, interference, B-ring size, etc., on sealing performance were investigated, revealing that although a B-ring with high material yield stress can meet the sealing requirements, both the B-ring and the sealing surface of a reactor body will yield plastic deformation. B-rings with a low material yield stress exhibit obvious plastic deformation during startup and leak during shutdown. However, leakage parameters can be minimized by smaller interference and moderate wave radius.