Study On The Rail Grinding Based On The Geometric Characteristics Shapes

The economy of China has grown rapidly since the economic reform and the opening up of the nation. To meet the needs of the fast development of logistics and the traveling near the traditional Chinese New Year, the transportation among different regions become much heavier. Under such background, the Chinese railway transportation is also developing fast towards efficiency, safety, high speed, and multiple marshalling heavy haul. During a long service life of the rail, the natural processes of wear and deterioration of rail steel can result in a rapid condemnation of rail. The rail economy also suffers from the unbalance in the applied contact stresses and the unbalanced yield strength of the steel itself. Grinding of rails has become a maintenance technique that controls the rail surface fatigue and plastic flow.Under such background, this thesis conducts a discussion on contact fatigue and the abnormal wear of the rail, which are often seen in railway transportation. Using the vehicle-track coupling dynamics model and the rail profile design model based on the rail/wheel geometric characteristics, this thesis developed rail grinding profiles for the sharp curves, mild curves, and tangent lines of the track for passenger railway lines. The comparison was also made for the lateral yield, vertical force, lateral force and the derailment coefficient before and after rail grinding. Based the empirical rail profile design method base on the contact geometric characteristics, rail grinding profiles for sharp curve in the metro was designed in this thesis. The dynamic performance of the designed profiles was tested. It is found that the designed profiles improves the wheelset's ability of steering by making the wheels rolling at different radii, therefore, improves the vehicle's curving performance with less lateral yield. The main research contents and conclusions in the present thesis are as follows:1. A design method of rail profile is developed in this thesis, based on the contact geometric characteristics. Grinding profiles are designed for the sharp curves, mild curves, and tangent lines of the track for high speed passenger railway lines. Comparisons are made for rail contact geometric characteristics and vehicle dynamics before and after rail grinding. The results show that the designed rail grinding profiles can effectively improves wheel-rail contact by reducing contact stress and improves vehicle curving performance.2. Based on the geometric characteristics of wheel-rail contact surface design methods, grinding profiles for sharp curves in metro lines are designed. Dynamic analysis is performed to compare the dynamic performance of the vehicle before and after grinding. The results show that the grinding profiles significantly reduce the amount of sliding, the wheel-rail vertical force, the derailment coefficient and improve the curving performance of the vehicle.3. A new economic model for rail maintenance costs is proposed. The new model combines the costs for rail grinding, rail defect inspection, service down time, rail replacement, lubrication, risk and depreciation. The model offers a platform for optimizing rail grinding.