Abstract: The shock response spectrum is widely used in the design of ship and its shipborne equipment for impact resistance. Because of the existence of the trend term error, a distortion always occurs in the low frequency region of the shock spectrum. The effect mechanism of trend term error on measurement distortion in the low frequency region of shock spectrum was explained through theoretical analysis. The relationships between the magnification in the zero drift phenomenon with the natural frequency of system and the response of system were obtained. And the advantages and disadvantages of mathematical correction methods are analyzed. A new correction method of torsion pendulum correction model is proposed for the existing correction instrument, and a vibration equation of torsion pendulum model is established. And the approximate periodic solution and the main resonance frequency equation of torsion pendulum are derived by using the Ritz-Galerkin method. The maximum shock responses of the torsion pendulum and the traditional spring-mass-oscillator under the same impact environment was theoretically analyzed and test. The results show that the torsion pendulum has a good linear relationship with the spring-mass-oscillator within the swing angle of low frequency torsion pendulum less than 20.06°. By comparing the methematical correction method, traditional spring vibrator correction method and torsion pendulum correction method, it is found that the torsion pendulum has high reliability for correction results of low frequency region in the shock spectrum. Key

Key words: shockresponsespectrum, mediumandlowfrequency, trendtermerror, spring-mass-oscillator, torsionpendulum, correctionmethod