Designing a shock test system prototype based on a hydroelastic drive

Abstract

Laboratory shock tests involve the reproduction of simple one-time and repeated pulses of a certain waveform. In practice, such mechanical impacts on an object are implemented at specialized testing equipment ‒ shock systems. A promising direction in the development of shock machines includes the structures that operate on the energy of elastic deformation of the compressed liquid and the shell of the vessel that contains it. Such systems make it possible to improve the versatility, manageability, and accuracy of impact tests. Underlying this study is the use of a hydroelastic drive to design a prototype of the automated electro-hydraulic system for a shock test system. The proposed shock test system prototype makes it possible to expand the functionality of the installations to perform impact tests with a series of pulses, as well as improve manageability and increase the level of automation. The main feature of the proposed structural scheme is that the reconfiguration for a new impact pulse occurs very quickly. Owing to the presence of a driven rotary drum with braking devices, the bench makes it possible to generate a shock pulse repetition frequency of 1‒2 Hz. The constructed mathematical model of the shock machine takes into consideration the inertia of moving masses, the rigidity of the liquid or "one-way" spring of the charging chamber, as well as the influence of dampers on which the test platform rests. The variables in the mathematical model are linked by differential equations describing two periods within a shock system work cycle: charging and pulse generation. The model's practical value is to determine the dynamic characteristics of the test installation, as well as to calculate the required structural and technological parameters. The differential equations describing the movements at the shock machine have been solved in a numerical way. The study results have established the optimal value (in terms of minimizing the overload on an article on the return stroke of the rod) for the damping factor of the braking device, which is 13,000 kg/s. In this setting, the ratio of the amplitude of acceleration on the reverse stroke to the amplitude of effective acceleration during tests is reduced to a minimum of 0.195