Experimental Test and Simulation of the Tribological Performance of Electrical Contact at the Dangerous Frequency of Nuclear Safety-Related DCS Equipment

Nuclear power safety level DCS mainly completes the safe shutdown of nuclear power plant reactors and accident mitigation functions, and is called as an emergency braking system of reactors. Therefore, the reliability and stability of nuclear power safety level DCS is the key to ensure the safe operation of reactors. However, the use of a large number of electronic connectors in nuclear power safety level DCS leads to possible friction and wear problems, which brings serious safety risks to the reliable control of the reactor. In order to address the issue of electrical contact wear in nuclear safety-related DCS device during their service life, the tribological behaviors of electronic connectors in nuclear safety level DCS were studied by means of experimental tests and numerical simulation, focusing on the friction and wear behaviors of electrical contact interfaces at different current currents. Firstly, the frequency scanning test on the safety-related DCS devices was conducted firstly, to determine its critical frequencies. Subsequently, an experimental platform for electrical contact friction and wear was established, and a series of tribological experimental tests were carried out. By combining the sequential coupling analysis method of electricity-thermal-mechanics with Archard's wear model, the influence of current magnitude on electrical contact friction and wear was explored. The experimental and simulation results indicated that the resonant vibrations corresponding to primary modes occurred at approximately 12 Hz for nuclear safety related DCS equipment, suggesting that 12 Hz was the hazardous frequency of the equipment and would be used for subsequent electrical contact tribology tests. Under this excitation frequency, as the input current increased, the friction coefficient at the electrical contact interface exhibited a phenomenon of initially decreasing and then increasing. The electrical contact surface showed wear characteristics such as abrasive particle wear, delamination, and arc erosion. Although increasing current intensified the interface wear, the material softening at high temperatures resulted in an enlarged contact area which favored maintaining a low-resistance state of electrical contact interface for a longer time period. However, under high currents, uneven distribution of worn surfaces occurred and there was a significant increase in fluctuation frequency of contact resistance. Finite element analysis could effectively simulate the process of electrical contact friction and wear. However, due to different stress distributions within the friction region under electrically contacted conditions, varying depths of wear grooves could be observed. On both sides of these grooves, increasing current led to deeper groove depths while in the middle region between them, groove depth at an input current level of 2 A was significantly greater than those at input levels of 1 A and 3 A which was consistent with experimental results. The results of this study had a certain significance for recognizing the tribological characteristics of nuclear safety DCS electrical contact.