Papers by Author: Li Hua Fu

Abstract: Wheel/rail rolling contact fatigue is one of the most complicated and urgent problems of the key techniques of railway system, and seriously influences the operational safety. A finite element (FE) model of wheel/rail rolling contact of curve negotiation is established based on the single-layer track dynamic model, which is considering the effect of rail straightening residual stress, the actual wheel tread and the elastic support of rail track bed. The nominal stress approach is applied to study the rail rolling contact fatigue life with two residual stress-state conditions. Results show that the distribution of rolling contact fatigue life on the surface of rail head presents obvious peaks and troughs with a specific wavelength in the longitudinal direction, which are approximately corresponding to the peaks and troughs of the contact force. Meanwhile, the rail rolling contact fatigue life firstly increases and then decreases while the running speed varying from 150 to 250 km/h, and decreases while the axle load varying from 13 to 17 tonnes which do not fully show a linear law.

Abstract: This paper adopted explicit dynamics FEM software ANSYS/LS-DYNA and carried out the numerical simulation calculation of 9 roller horizontal straightening and 8 roller vertical straightening for 60 kg/m heavy rail with original curvature. The reductions of straightening rollers are taken as the main effective factor to the residual stress in the straightening regulation. It adopted orthogonal experimental method to obtain the main effective factors for straightness and residual stress. In the assurance of meeting the straightness, it obtained the regulation in which the residual stress is the smallest, so it makes the important theoretical and actual sense to formulate the rational straightening process and improve the straightening quality of rail.

Abstract: It has established the FEM model of nine horizontal roller straightening with original curvature for 60㎏/m heavy rail by using explicit dynamics software ANSYS/LS-DYNA in the paper, and it carried out the dynamic simulation process of the nine horizontal roller straightening, analyzed the stress changing rules of heavy rail in the seven deformation zones during the straightening process , even studied the value and distributive condition of residual stress after straightening, disclosed the mechanism of the residual stress in the heavy rail straightening process, and the paper is a guidance to improve heavy rail quality in straightening craft. It has the reference value to the design of heavy rail straightening machine and the formulation of the straightening regulations.

Abstract: Electric contact is an important component of high voltage circuit breaker switch lubicle, isolating switch and ground switch. It is composed of arc-extinction end and conduction end. The usual material of arc-extinction end is copper-tungsten and the usual material of conduction end is copper or chrome-copper. Currently, four process for making the integral electric contact such as common brazing, vacuum brazing, electric-beam welding; liquid-phase sintering is of the best integral technique capability. This article puts forward a process by friction welding for integral Cu-W electric contact, and studies about the weldability between copper-tungsten and copper or chrome-copper, and between copper and chrome-copper. In order to solve the worse weldability between copper-tungsten and copper or chrome-copper, the design conception of intermediate layer is tentatively suggested. From experimental results, using the production method of friction welding is practicable to integral electric contact. It has some advantages, such as high availability of material, high productivity, high ratio of finish products, and it has no any influence on environment.