Contact Conditions over Turnout Crossing Noses

Abstract

Even though railway systems are becoming a more preferred transportation concept regarding high speeds, punctuality, safety, availability, which are appealing for passengers; cost-effectiveness, environmentally friendliness and less soil occupation corresponding to other transportation modes, which attracts the governments and operators, it still suffers from two major drawbacks: first investment and high maintenance costs. Life cycle costs analyses show that maintenance costs have significant effects on the total value as well as early investment costs. The reason for high maintenance costs in railway systems is that critical components (i.e. turnouts), which are the weak points of a railway system, require frequent detailed inspection and maintenance associated with high safety standards. For instance, it is widely known for a turnout that European countries have conducted a series of projects such as Innotrack, IN2Rail, S-code in order to lower the maintenance costs. Moreover, turnouts also restrict the design limits of a railway system, which results in lower operational speeds. Consequently, studies on turnouts have been increasing. In general, the studies focus on track stiffness along the turnout, environmental effects on configuration, conversion problems and the contact problem. Among these issues, the issue regarding contact is the most premature problem due to its nonlinear nature, which could not be solved analytically. Having increased computational power, sophisticated methods for the contact problem have been developed. The problem regarding the contact patch, forces and positions are of considerable interest. From the aspect of turnout crossing noses, there is a contact patch evolution on crossings from single to double and double to single contact patch, which affects the vehicle dynamics to a large extent. Numerous studies have been presented for the problem. However, these studies, commonly, consider one type of turnout, mostly standard turnouts. Regarding the absence of collective study, in this study, the aim is to review the contact conditions depending on turnout types from a wider perspective. As result of the study, it has been found that crossing nose types such as fixed and movable have significant effects on lateral and vertical movements of the contact patches. Moreover, different layouts of turnouts have different effects on the contact conditions.