## 1 Introduction  
The phenomenon of tensile buckling is of considerable scientific interest, and numerous theoretical studies have been devoted to it, especially in the last decade. For example, tensile buckling is studied for elastic rods [1, 2], elastomeric bearings [3], which lose stability due to shear deformation, bars with sliding connections [4] installed in separate sections, allowing elastic transverse movement in the beam sections. Various theoretical models of elements and mathematical models of their analysis are used. It is shown that the results of theoretical analyses depend on the models and methods for their analysis [5]. As an example, contradictory analysis results of this phenomenon for a stretched hinged supported beam have been provided. In this regard, an experimental study is of particular importance in order to verify the existence of the phenomenon and compare the calculated and experimental values of the critical force. Theoretical and practical issues, related to an elastic tensile rod with one end sliding along a straight guide and the other one along a curve, have been widely investigated in the recent years [6, 7, 8]. The possibility of buckling at some critical tensile force value was studied theoretically. The post-buckling behavior of the system was described, and calculation dependences, allowing to find the critical load, were proposed [6, 7]. Hinged and clamped connection schemes between rod and curved guide were considered. However, the investigated system was studied experimentally only after buckling. A thorough literature review on the topic was recently presented by [PERSON] and [PERSON] [8]. The present study was aimed at an experimental investigation of the buckling phenomenon for an elastic rod with an end sliding along a circular guide and with the following connection schemes: pinned-rigid, rigid-pinned, and rigid-rigid. To decrease the influence of friction in the guides, a dynamic method was used to study buckling and obtain the critical load [9; 10]. With this method, the critical force value was assumed to correspond to the zero frequency of natural vibrations [10; 11]. Since the zero frequency cannot be reached, the critical load was determined by extrapolating the results measured with a certain error at lower values of the axial force. It was shown theoretically [11] and experimentally [12] that for a compressed rod with rigid, pinned, and free end conditions, the buckling phenomenon is indicated by a monotonic decrease in the natural vibration frequency as the compression load increases. The same indicator for buckling at tension was used in the current research. The novelties of this study applying the dynamic method include:  
* developing a testing stand that allows reducing the influence of resistance to the movement of the rod end along a circular guide;
* the methodology of the experiment, which allows determining the critical load with sufficient accuracy, including the choice of rod-curved guide system parameters, taking into account the deformation of the rod at the connection nodes. To obtain the critical load by extrapolating the experimental values of squared natural frequencies, a linear dependence between frequency and axial load is expedient, since it includes a minimum of parameters and therefore it is less sensitive to frequency and force measurement errors. For the above-mentioned connection schemes, this dependence was proved previously [13]. It was shown that as the axial force becomes higher, the frequency increases and asymptotically approaches to that of a cable under tension. There are no similar available data for a system in which the rod end moves along a circular trajectory, like the case that is investigated in the present study. In known devices for testing rods with an end moving along a curved guide, roller guides are used [7; 14; 15].