Improving the reliability of acceleration measurements during vibration tests

Abstract

The paper analyzes some causes of distortion of the set and measured vibration parameters during testing of equipment on an electrodynamic vibration stage. In particular, the influence of the joints of the mating surfaces on the vibration stand – a transition table and a transition table – a device for vibration is determined. An idealized model of the junction of two surfaces is proposed, which can be theoreti-cally described using the theory of generalized conductivity of heterogeneous structures. The joint is represented as a matrix of metal with inclusions of voids, represented as components of a mixture having infinite conductivity. A relation is derived showing that the elasticity model of the two metal surfaces joint is approximately 30 % less than that of a homogeneous metal. The obtained theoretical conclusions substantiate the recommendation to increase the rigidity of the mechanical system "vibration stand table - transition table – device for vibration tests" by introducing a thin (40...80 microns) polyethylene film into the joints. The fundamental reason for the difference in the measurement of the vibration acceleration magnitude at different control points is shown – the presence of a tipping moment in the mechanical system. Elimination of a methodological error during vibration tests is possible when controlling the vibration stand not by a real, but by a conditional control point. Recommendations on the choice of a conditional control point for the vibration stand during vibration tests of the equipment are given and justified.