大型无约束型金属波纹管膨胀节隔振测试方法

Research on vibration isolation test method of large non-constrained metal bellows expansion joints

  • 摘要:
    目的 在大型无约束型金属波纹管膨胀节(简称金属膨胀节)的隔振试验中,由于其充压时极易发生失稳,试验工装既要平衡内压产生的巨大盲板力,又不能完全固定金属膨胀节两端,试验难度大,目前缺少标准的试验方法,为此设计一种用于测试大型无约束型金属膨胀节隔振效果的试验装置。
    方法 利用双只金属膨胀节对接彼此支撑,两端由台架支撑固定的方法实现轴向稳定,设计轴承拉索和气囊两种不同的限位方式防止径向失稳。利用激振器对充压下金属膨胀节进行轴向和径向激振,采集10~315 Hz频率范围内金属膨胀节在两种限位方式下的加速度响应,计算输入端与输出端的振级落差。
    结果 试验结果表明,轴承拉索和气囊装置测量的总振级落差均随着金属膨胀节内部压力的增大而减小,且在0P,0.8PP这3种内压下气囊装置的总振级落差相对轴承拉索装置在轴向激振方向分别提升了8.59,5.70和4.80 dB,在径向激振方向分别提升了4.32,3.57和4.95 dB。
    结论 该装置能获得大型无约束型金属膨胀节的隔振性能,气囊限位装置比轴承拉索限位装置对振级落差影响小,建议测试装置采用气囊径向限位可获得较佳的测量结果。

     

    Abstract:
    Objectives In the vibration isolation testing of large non-constrained metal bellows expansion joints (hereinafter referred to as expansion joints), due to their easy instability under filling pressure, test devices that balance the huge blind force generated by the internal pressure cannot be completely fixed at both ends of the expansion joints, making testing difficult and leading to the lack of a standard test method. For this reason, a device is designed to test the vibration isolation effect of expansion joints.
    Methods Double-metal expansion joints are supported against each other with both ends fixed by the pedestal support, achieving axial stabilization. Two different limiting methods – bearing cable and airbag – are designed to prevent radial instability. The axial and radial excitation of the expansion joints under pressure is carried out using a shaker, the acceleration response in the frequency range of 10~315 Hz under the two limiting methods is collected, and the difference in vibration level between the input end and output end is calculated.
    Results The total vibration level drops measured by the bearing cable and airbag devices respectively decrease with the increase in the internal pressure of the expansion joints, and the total vibration level drop of the airbag device under internal pressure of 0P, 0.8P and P increases by 8.59 dB, 5.70 dB and 4.80 dB respectively in the axial excitation direction of the bearing cable device. In the radial excitation direction, it increases by 4.32 dB, 3.57 dB and 4.95 dB respectively.
    Conclusions The designed test device can measure the vibration isolation performance of metal bellows expansion joints. As the airbag limiting method has less influence on the vibration level drop than the bearing cable limiting method, the device for testing the vibration level drop of expansion joints should adopt airbag radial limiting to obtain better measurement results.

     

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