The selection of seismic resistance grades for touch finger springs used in rail transit is directly related to the safety of train operation. Under conditions such as earthquakes and vibrations, grade mismatch can easily lead to electrical connection failure. It is necessary to strictly follow industry standards and equipment requirements.

It is necessary to clearly define the seismic resistance grade standards in accordance with the GB50909-2014 code. Performance Requirement I corresponds to seismic resistance grade 1. It can be used normally without damage after an earthquake. Performance Requirement II: The grade must be no less than 2. Minor damage is allowed but can be repaired. Performance Requirement III: The grade must be no less than 3 to ensure that the vehicle does not collapse completely and can be repaired and reopened to traffic.

The selection should be based on the seismic fortification intensity of the line. For high-intensity areas, Grade 3 touch finger springs should be given priority. For medium-intensity areas, Grade 2 products can be selected. Due to its high operating speed, the seismic resistance grade of high-speed railway lines needs to be one grade higher than that of metro lines.

Material properties are at the core of grade adaptation. The beryllium copper material touch finger spring has stable elasticity and can meet the requirements of high-level seismic resistance. Stainless steel has strong corrosion resistance and is suitable for humid environments, but its seismic resistance grade is limited. Chromium-zirconium copper material has both electrical conductivity and vibration resistance, making it suitable for high-current scenarios.

The structural design needs to match the seismic resistance grade. The multi-point contact structure can disperse vibration stress and enhance seismic performance. The card slot fixing method is more stable than the traditional installation and reduces vibration displacement. The diameter of the spring wire needs to be adjusted according to the seismic resistance grade. For higher grades, a thicker wire diameter should be selected to enhance rigidity.

The selection should take into account the criticality of the equipment. The touch finger springs used in traction systems and signal equipment should be selected with a high seismic resistance grade. The auxiliary power supply system may be appropriately downgraded in grade based on its importance, but it shall not be lower than grade 2. After selection, it needs to be verified through vibration tests to ensure that it meets the actual working conditions.

The verification stage needs to simulate actual scenarios. Sinusoidal vibration testing is adopted, with frequencies covering the common vibration range of rail transit. After the test, the contact pressure of the touch finger spring is detected. If the attenuation does not exceed 10%, it is qualified. Combined with salt spray tests, it ensures both seismic resistance and corrosion resistance.