Wear types and maintenance strategies for national standard rails
- What are the common wear types of national standard rails?
Rolling wear is the most common, generated by rolling contact between wheels and rails, forming uniform wear on the rail head surface. The annual wear of ordinary railways is about 0.3 - 0.5mm, and that of heavy - haul railways can reach 0.8 - 1.2mm. Sliding wear mostly occurs in curve sections, where there is relative sliding between wheels and rails. The wear of the outer rail head is 2 - 3 times more serious than that of the inner rail. Small - radius curves (R≤600m) are prone to such uneven wear. Fatigue wear is caused by alternating loads, with fatigue cracks on the rail head surface, which gradually expand into spalling. Heavy - haul railways are prone to this after 2 - 3 years of operation, with spalling depth up to 1 - 3mm. Corrosive wear is common in humid or saline - alkaline environments. The rusted rail surface is worn off by wheels, forming pockmarked wear. Such wear in coastal areas is 30% - 50% faster than that in inland areas.
- What factors will aggravate the wear of national standard rails?
The increase of train axle load is a key factor. When the axle load increases from 20t to 25t, the rail wear increases by 50% - 70% because the contact stress rises significantly with the increase of axle load. The increase of driving speed will increase the wheel - rail impact force. The rail wear of high - speed railways with a speed of 300km/h is 1.5 - 2 times that of ordinary railways with 120km/h, especially in turnout areas. Poor track smoothness will lead to poor wheel - rail contact and local stress concentration, increasing the wear rate by 40% - 60%. When the height deviation exceeds 3mm, wear is aggravated. Improper matching of wheel and rail materials, such as wheel hardness being 10% higher than rail hardness, will accelerate rail wear by 20% - 30%. The hardness difference between them should be controlled within 5%.
- How to detect the wear degree of national standard rails?
Regularly detect with rail wear measuring instruments, once every 3 months for ordinary railways and once a month for high - speed railways. Measure the rail head wear and side wear, compare with the standard value. When the wear exceeds 1/3 of the design margin, maintenance is required. Detect with a rail head profiler, generate a profile curve and compare with the original curve. If the area decreases by more than 10%, grinding measures must be taken to ensure good wheel - rail contact. Observe the rail surface state. If there are obvious spalling, cracks or fish - scale wear, it indicates that the wear is serious, and local replacement or grinding is required, which is more sensitive for heavy - haul railways. Monitor train vibration data. Increased wear will increase the vibration acceleration by 15% - 20%. Indirectly judge the rail wear state through vibration sensors and arrange maintenance in time.
- What are the maintenance measures for different wear types?
Rolling wear can be handled by periodic grinding. Use a profile grinder to grind the rail head to the standard profile. Grinding off 0.3 - 0.5mm can restore the wheel - rail contact state. Ordinary railways are ground once every 2 - 3 years. For sliding wear in curve sections, adjust the outer rail superelevation to make the wheel - rail contact point in the best position. At the same time, perform unilateral grinding on the outer rail with serious wear to reduce side wear. Curves with 600m radius are ground once every 1 - 2 years. For fatigue wear, surface cracks must be removed in time. Shallow cracks (≤0.5mm) can be eliminated by grinding. Deep cracks (＞0.5mm) require cutting off the damaged rail section and replacing with new rails to avoid crack expansion leading to fracture. For corrosive wear, strengthen rail anti - corrosion, regularly apply anti - rust paint. Coastal areas can use anti - corrosion coated rails and shorten the grinding cycle to remove rust layers.
- What are the differences in rail wear rates among different railway types?
Heavy - haul railways have the fastest wear rate, with annual wear of 0.8 - 1.5mm. Due to large axle load and frequent loads, grinding is required every 1 - 2 years, and some rails in key sections are even replaced every year. High - speed railways have uniform but high wear rate, with annual wear of 0.5 - 0.8mm, mainly rolling wear. Preventive grinding is carried out every 2 - 3 years to ensure smoothness. Ordinary railways have a medium wear rate, with annual wear of 0.3 - 0.6mm, with obvious differences between curve and straight sections. Targeted maintenance is required: straight sections are ground every 3 - 4 years, and curve sections every 2 years. Urban rail transit has "tread depression" wear due to frequent start - stop, with annual wear of 0.6 - 1.0mm. Grinding is required every 1.5 - 2 years, and train braking strategies are optimized to reduce sliding wear.