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44 results on '"Ding, H.H."'

35. Experimental study on wear properties of wheel and rail materials with different hardness values

Author

Hu, Y., Watson, M., Maiorino, M., Zhou, L., Wang, W.J., Ding, H.H., Lewis, R., Meli, E., Rindi, A., Liu, Q.Y., and Guo, J.

Abstract

This paper aimed to investigate the wear properties of different wheel-rail material pairs with various hardness values. Twin-disc wear experiments were carried out via cross-matching five types of wheel material (ER7, ER8, CL60, C-class and D-class) and four types of rail material (U71Mn, U75V, PG4 and PG5). The effects of bulk hardness, post-test hardness, hardening ratio, and rail/wheel hardness ratio (HR/HW) on the wear rate of wheel and rail materials were analyzed.\ud \ud \ud The results indicated that the wheel wear rates decreased with wheel bulk hardness and slightly increased with the rail bulk hardness. However, the rail wear rates decreased with the increasing wheel bulk hardness under 1% creepage and 1500 MPa contact pressure. In addition, both the wheel and rail wear rates showed increasing trends with the increase in wheel hardening ratio and the pre-test HR/HW. The surface damage of the harder C-class and D-class wheels, and the high-hardness PG4 and PG5 rail materials were relatively slight. The premium PG4 and PG5 rails possessed significantly shorter cracks than the base materials (ER8-U71Mn), whereas, U75V was relatively longer. The results will not only help optimize wheel and rail hardness matching, but also improve the prediction of wear and crack growth reliant on wheel and rail material properties.

Published
2021

44. Characterization and formation mechanisms of rail chips from facing grinding by abrasive wheel

Author

Ding, H.H., Yang, J.Y., Wang, W.J., Guo, J., and Liu, Q.Y.

Abstract

Rail grinding is a widely-used method to eliminate surface damages on railway tracks. The grinding chips are closely related to the grinding parameters and the grinding quality. Therefore, the investigation on the characteristics and the formation mechanism of chips from rail grinding is beneficial for the optimization of rail grinding process. In the present study, the grinding chips from the real rail grinding in the field and from the rail grinding experiments in the laboratory were analyzed in terms of their morphologies, microstructural evolution and chemical characteristics. The results showed that flowing, knife, slice and spherical chips were generated during rail grinding. The formation mechanism of flowing, knife and slice chips was plastic deformation by forces from abrasive grains with oxidation in air by grinding heat. Primary and secondary shear zones and central zones were generated. In the primary shear zone, cracks were generated in knife and slice chips. In the secondary shear zone, obvious plastic deformation was formed in knife and slice chips and a significant white etching layer (WEL) was generated in knife chips. The formation mechanism of spherical chips was melting of small powdery grinding debris by the high temperature and the subsequent solidification, accompanied with severe oxidization in air. The oxides produced in chips consisted of FeO, Fe3O4, Fe2O3and AlFe2O4. The grinding quality could be predicted through observing the grinding debris. The larger percentage of flowing chips represented the better grinding quality (smaller surface roughness, slighter surface burn and thinner WEL on ground rail), which could be the goal for the grinding parameters choice.

Published
2021
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