When the creep exceeds acceptable limits and it becomes challenging to secure the A size using the adjustment lining, the product must be replaced. For metal-rubber composite conical springs, typically 8 or 4 units are installed per bogie. To ensure the overall balance of the vehicle’s height, a height measurement test under load is essential.
The elastic properties of these springs are influenced by temperature, so the test samples must be kept at a stable temperature of 20–25°C for more than 24 hours before testing. Additionally, since rubber is a polymer material, it is crucial to pre-press the product five times under the specified load before any test to relieve internal stresses and ensure accurate results.
During the load-based height measurement test, the marked height is 205 mm when a vertical load of 18,175 kN is applied. The measured dimension should fall within the range of 204.12 mm to 205.18 mm. If the dimension is out of tolerance, a spacer can be used to bring it within the required range. This measurement must be performed on 100% of the products.
During the test, the height was measured at four points, and the arithmetic mean was calculated as the final result. The individual measurements were: H1 = 205.113 mm, H2 = 205.164 mm, H3 = 205.172 mm, and H4 = 205.136 mm. The average height was calculated as H = (H1 + H2 + H3 + H4) / 4 = 205.146 mm.
For the normal temperature static test, the vertical stiffness test was conducted using a CSS55100 microcomputer-controlled universal testing machine. The product was first preloaded with 0.11 kN vertically, where the displacement was set to zero. Then, the load was applied at a constant rate of no more than 30 mm/min, compressing the spring from 0 to 75 mm, followed by unloading. This process was repeated three times consecutively without any time interval between cycles.
After preloading, there was a 15-minute waiting period before the next vertical loading. At 0.11 kN, the position was set to 12 o’clock, and the spring was compressed from 0 to 65 mm while recording the load-deformation curve. The vertical stiffness was calculated during the rising half-cycle of the curve (the compression phase). The vertical static performance parameters include a stiffness of 0.175 kN/mm in the deformation range of 0–65 mm, with a tolerance of -11% to +9%, meaning the stiffness should be between 0.167 kN/mm and 0.182 kN/mm. Additionally, the vertical stiffness must remain nearly linear up to a deformation of 30 mm.
Once the data processing was complete, the computer generated a load-deformation hysteresis curve. For lateral stiffness determination, the sum of the absolute values of the loads at the +5 mm and -5 mm deformation points was divided by 10 mm to obtain the transverse stiffness value for the given deformation range.
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