MATERIALE PLASTICE ♦53♦No.2♦2016 http://www.revmaterialeplastice.ro 295 The Use of Rubber as Elastic and Damping Element at Buffers Equipping Railway Vehicles CAMIL CRACIUN*, MADALINA DUMITRIU University Politehnica of Bucharest, 313 Splaiul Independenþei, 0600042, Bucharest, Romania Rubber is increasingly used in the industry of railway rolling stock, as elastic and damping element for the suspension of the vehicle or buffer and draw-gear devices. The simplicity of design, the lack of some special maintenance operations for the rubber elements and the high degree of shock and longitudinal oscillations absorption led to its increasingly use to shock isolators in order to equip railway vehicles. Keywords: rubber, railway vehicle, buffer, hysteretic loops Railway vehicles, regardless of the type of construction, motor vehicles or hauled vehicles, are equipped with buffer and draw-gear devices, commonly named buffers and binding couplers. The use of buffers, known in the literature as shock isolators [1, 2] has as main purpose the protection of the structure of railway vehicles when they interact during braking, pushing of the train or forming by individual launching of the vehicle from the shunting humps. Also, the buffer and draw-gear device affects longitudinal dynamic phenomena that develop in the body of the train, with implications on the running stability [3]. Each vehicle consists of four buffers installed on the head bar of the chassis, two on each side. In addition, on each front, there is a buffer with flat plate and one with curved plate, so it will always be contact between a buffer with flat plate and one curved. Thus, it is avoided the breaking of buffer plungers during the movement in a curved line or the tendency of lifting in the case of the curved buffers, when there are level differences, respectively the change slope – downhill, slope – alignment or downhill-alignment. The design and construction of buffers have evolved over time and have mainly focused on increasing the storage capacity and dissipation of the deformation potential energy due to: the increase of railway velocity, hauled tonnages and the number of vehicles from a train [4]. The main requirements that buffers must meet are: -protection of the vehicle against the number and intensity of repeated shocks that occur in using; -safety of the link bogie – chassis; -safety during circulation and stabilizing role particularly during the movement in curves; -dabbing speeds at values that provide an optimal duration and acceptable conditions for the implementation of sorting and train formation process; -the reducing of longitudinal acceleration to values that provide security and integrity to the transported goods, passenger comfort and the quality of driving. During the railway operating, the emergence and development of the compression forces and, respectively, tensile forces to the coupling devices and shock protection are mainly due to the successive entry into action of the brakes for every vehicle in the train body, aspect that cannot be avoided as long as the vehicles present UIC brake. These forces lead to oscillatory movements along the train that, under certain conditions, are dangerous in terms of road * email: craciun_camil@yahoo.com; Tel.: 0766429734 safety. The extinction of these oscillations depends on the capacity to absorb the kinetic energy of the collision devices [5]. To determine the dynamic longitudinal forces during train braking, it is necessary to determine the characteristics of the collision devices, but also those of traction and binding. Therefore, to enhance the simulation programs on the evolution of longitudinal forces in the trains body, it is necessary to establish calculation formulas that portray elastic and damping characteristics of the buffers and draw gear devices. The construction of buffers with rubber elastic elements From the construction point of view, there is a great variety of buffers, especially due to technical solutions used in order to store and dissipate convenient values of the potential energy of deformation in the elastic and damping elements. Related to this, there are differences due to vehicle operating schemes, meaning that passenger coaches and locomotives present better operating conditions than flat wagons. The buffers of the railway vehicles have a simple structure, consisting mainly of (fig. 1): 1 represents buffer body, 2 is subassembly which comprises the plate and 3 its elastic element. Depending on the elastic element used, there are buffers with metal springs (coil springs or ring springs), rubber springs, steel and rubber combined springs or hydraulic buffers. The buffers with ring springs are the most common type used in the construction of flat wagons. For the locomotives, buffers present coiled springs or friction ring springs. Wagons and locomotives used for passenger trains, due to easier operating conditions than flat wagons, can be equipped with buffers that have the elastic element from rubber or combined from steel and rubber. Also, to these types of vehicles, hydraulic buffers may be used. The use of rubber in the railway industry was made possible with the development of the vulcanization Fig. 1. General construction of buffers