# Railway Track Stress-Strain Analysis Using High-Precision Accelerometers
## 2 State of the Art  
Mechanical deformation arising in the elements of the superstructure of the railway line, and on the main site of the roadbed during the interaction of the track and the rolling stock, are some of the paramount characteristics that determine the durability and economic efficiency of a railway, its life cycle cost, and the safety of the transportation process as a whole [12; 13]. Railway track diagnostics are essential for checking the precise condition and evolution of a network's infrastructure; in so doing, they make it possible to formulate a replacement strategy and plan work, taking into account operating requirements. Most operations in the monitoring and control of deformations of a railway track are currently carried out with the help of various track-testing cars [14; 15]. Some examples of this technology's successful use are given in recent papers [16; 17]. Nevertheless, the problem of using the sensors deployed on the railway track line remains highly relevant, but does not ensure permanent and reliable monitoring. Sensors are widely used in the railway industry to perform monitoring of multiple parameters and thus provide high security, reliability, and efficiency. Examples of railway sensors being implemented are presented in [18; 19]. Various types of sensors are deployed to provide the required railway track diagnostics [20; 21; 22]. Modern ideas, methods, and technological trends in the area of sensor equipment design and development are combined under the concept of the Internet of Things [23; 24; 25], which was used as a theoretical basis for the current research. Implementation of this theory in practice is concerned with solving a number of problems of sensor allocation and data collection, which significantly affect the benefits of its application [26; 27]. The problem of railway sensor equipment design and development requires simulating a complex system and having access to a railway track and diagnostic instrumentation that dynamically interacts with a rolling stock wheel set in idle and load conditions. In this paper, we propose a new approach for sensor equipment design and development based on a railway track stress-strain analysis [28; 29; 30]. The sensors should be located in the places at the most critical risk of construction damage, determined using the stress-strain analysis [31; 32]. The stress-strain state of a railway track is mostly influenced by the train load and the configuration of the track's superstructure: the type of rails, intermediate rail fastenings, sleepers, the thickness and compaction of the ballast layer, etc. At present, there is no direct method for determining the mechanical stresses in the elements of the railway track that arise during the action of the rolling stock. However, calculation of the estimated parameters of the internal force factors is possible using classical analytical methods and mathematical numerical modeling. Railway track line stress-strain state testing has certain specifics that have studied in a number of research projects [33; 34; 35]. It is noted that rail stress can be changed due to thermal and mechanical loads in both longitudinal and vertical directions. Therefore, monitoring the longitudinal rail movement or rail creep is regarded as one of the effective ways to understand the rail's stress states in critical locations, including fixed structures such as level crossings, turnouts, and fixed top bridges. The dynamic component of the design force depends on various factors that must be considered in models and design solutions [36]. Some examples of efficient stress-strainanalysis are illustrated by [37; 38; 39], which can be considered in this research. Railway track line monitoring and stress-strain analysis is performed to provide safety and stability according to the modern requirements and standards [40; 41]. High longitudinal rail stresses contribute to problems such as track buckling, rail joint failure, rail breakage, and failure of turnouts.