Answer:
The article mentions that when the grinding temperature is below 471°C, the rail surface appears in its normal color; between 471-600°C, the rail shows light yellow burns; and between 600-735°C, the rail surface shows blue burns. Therefore, one can infer the degree of rail burn by observing the color changes on the rail surface after grinding.

Answer:
The EDS analysis results in the article show that with the increase of grinding stone strength, the content of oxygen elements on the rail surface decreases, indicating a reduction in the oxidation degree of the rail surface. This is consistent with the trend of color changes on the rail surface, suggesting that lower strength grinding stones lead to more severe oxidation.

Answer:
The article points out that during the formation of debris, plastic deformation occurs and heat is generated due to the compression of abrasives; during the outflow process of debris, the bottom surface of the debris rubs against the front end surface of the abrasive and generates heat. Therefore, the combined effect of debris deformation and frictional heat leads to a higher degree of oxidation on the bottom surface of the debris, resulting in a higher content of oxygen elements.

Answer:
The XPS analysis results in the article show that there are C1s, O1s, and Fe2p peaks on the rail surface after grinding, and the percentage of O atoms decreases with the degree of burn on the rail surface. Through XPS analysis, it can be determined that the main oxidation products on the rail surface are iron oxides, specifically Fe2O3 and FeO, and as the degree of burn decreases, the content of Fe2+ increases while the content of Fe3+ decreases.

Answer:
According to the article, the peak area percentages in the Fe2p narrow spectrum from XPS analysis show that from RGS-10 to RGS-15, the peak area percentages of Fe2+2p3/2 and Fe2+2p1/2 increase while the peak area percentages of Fe3+2p3/2 and Fe3+2p1/2 decrease. This indicates that as the degree of surface burn on the rail decreases, the content of Fe2+ in the surface oxidation products increases, while the content of Fe3+ decreases. Therefore, one can judge the degree of rail surface burn from the proportion changes of Fe2+ and Fe3+ in the XPS analysis results.

A: High-speed Grinding (HSG) technology is an advanced technique used for high-speed rail maintenance. It operates through sliding-rolling composite motions, driven by frictional forces between grinding wheels and the rail surface. This technology enables material removal and abrasive self-sharpening, offering higher grinding speeds (60-80 km/h) and reduced maintenance windows compared to conventional grinding.

A: The Sliding-Rolling Ratio (SRR), which is the ratio of sliding speed to rolling speed, significantly influences grinding behavior. As the contact angle and grinding load increase, the SRR increases, reflecting changes in the sliding-rolling composite motion of the grinding pairs. Shifting from a rolling-dominated motion to a balance between sliding and rolling significantly improves grinding outcomes.

A: Optimizing the contact angle improves grinding efficiency and surface quality. Studies show that a 45° contact angle produces the highest grinding efficiency, while a 60° contact angle yields the best surface quality. Surface roughness (Ra) substantially decreases as the contact angle increases.

A: Thermo-mechanical coupling effects, including high contact stress, elevated temperatures, and rapid cooling, lead to metallurgical transformations and plastic deformation on the rail surface, resulting in the formation of a brittle white etching layer (WEL). This WEL is prone to fracture under cyclic stresses from wheel-rail contact. HSG methods produce a WEL with an average thickness of less than 8 micrometers, thinner than the WEL induced by active grinding (~40 micrometers).

A: Grinding debris analysis provides additional insights into the material removal mechanisms. Flow-like and knife-shaped debris, which signify effective grinding performance, are more prevalent at higher SRRs. In contrast, block and sliced debris dominate at lower contact angles, reflecting inadequate grinding performance. The presence of spherical debris increases with grinding loads, indicating elevated grinding temperatures.

A: Sliding facilitates material removal from the rail surface, while rolling enhances debris discharge and abrasive self-sharpening. This dynamic balance is essential for achieving efficient grinding with minimal thermal damage.

A: By optimizing sliding-rolling composite motions, grinding efficiency can be improved, surface quality can be enhanced, and the service life of grinding wheels can be extended. Radar charts show that a 45° contact angle provides the best overall balance of efficiency and quality, while a 60° contact angle consistently produces the smoothest surfaces.

A: This research underscores the importance of dynamically balancing sliding and rolling motions to enhance grinding performance, improve surface quality, and extend the service life of grinding wheels. For initial grinding passes, a 45° contact angle maximizes material removal efficiency, while a 60° angle ensures superior surface quality in finishing stages.