A theoretical and experimental study of the deformation of the piston-cylinder unit of a metrological pressure balance

[摘要] Pressure balance is a measuring system widely used in metrology as a reference standard. The common procedure is to estimate the pressure from an analytical formula involving a set of phenomenological parameters. These parameters are determined experimentally by calibration tests of the balance. In particular, the piston-cylinder deformation is taking into account by the use of a global distortion coefficient and by the use of an effective area of the piston. In order to analyze the possible influence of local deformation on the pressure estimation, a Finite Element (FE) model has been developed using OpenCavok FE code. For a given position of the piston in the cylinder chamber, for a given initial gap between of the cylinder and the chamber, a coupled fluid-structure calculation is carried out. From the local fields, mean values are calculated from which the effective area of the piston-cylinder unit. The analysis is conducted for several engagement lengths of the piston in the chamber and for several loads. The first results obtained show that the local deformation play a role and that FE models could help for precise calculation of the measured pressure.

[发布机构] Federal University of Ceará, Department of Mechanical Engineering, Fortaleza, CE, Brazil^1

[效力级别] 力学 [学科分类] 力学，机械学

[关键词] Analytical formulas;Calibration tests;Cylinder chambers;Distortion coefficients;Local deformations;Piston-cylinder units;Pressure estimation;Reference standard