Stiffness test and stability test of metal bellows

Date:Sep 17, 2018

The metal bellows is a cylindrical thin-walled elastic shell with transverse corrugations, which has a wide range of applications as displacement compensation, vibration isolation and flexible joints for pipes and equipment. Research on the static and dynamic characteristics of metal bellows has been widely concerned, but there are still many problems to be further studied.

In order to verify the correctness of the finite element results, the stiffness and stability tests of the metal bellows were carried out.

Stiffness test

The metal bellows stiffness test principle is shown in the figure. During the test, the end pipe and the cover are welded at both ends of the test piece, placed on the test bench, and the lower cover is fixed to the test stand. The displacement is realized by adjusting the tie rod nut, and the displacement is monitored by the dial indicator. After the weighing indicator is zeroed, record the prestress value of each tension sensor, adjust the displacement of the tie rod nut, record the force value of the displacement pull-down pressure sensor, and obtain the force-displacement curve, and find the metal bellows when the pressure is zero. Axial tensile and compression stiffness values.

Stability test

The metal bellows stability test principle is shown in the figure. During the test, the test piece is sealed at both ends and axially limited. One end is connected to the pressure gauge, one end is connected to the pressure test pump, and the test piece is slowly pressurized by the test pump. The pressure difference between each stage does not exceed the expected instability pressure. 10% (take 0.04MPa), hold pressure for 5min, can not be unloaded in the middle until twisted, and finally the critical instability pressure is measured.

Metal bellows have the disadvantages of complicated manufacturing process, high cost, poor safety and reliability, and loss of elasticity. According to the metal plastic deformation theory and the metal pressure processing principle, the metal bellows manufactured by the integral forming method overcomes the above disadvantages while retaining the advantages of the metal bellows.

The stiffness and stability of the metal bellows show strong nonlinear characteristics. The deviation caused by the linear finite element model is large, and it is difficult to achieve the appropriate accuracy requirements. The results obtained by the nonlinear finite element method have good consistency with the experimental data, and can better simulate the critical instability pressure and instability of the metal bellows.

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