Evaluation of contact-type failure development using fluctuation of natural frequency caused by nonlinear wave modulation (Verification of estimation method of natural frequency fluctuation by time response analysis)

Transactions of the JSME (in Japanese) Pub Date : 1900-01-01 DOI:10.1299/transjsme.20-00105

Takashi Tanaka, Y. Oura, S. Maeda, Zhiqiang Wu

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Abstract

This research presents the evaluation method of contact-type failure level based on nonlinear wave modulation. It is difficult to detect contact-type failures using a linear ultrasonic inspection. The detection method based on nonlinear wave modulation has been proposed to detect the contact-type failure. Nonlinear wave modulation is the phenomenon, which is explained by contact acoustic nonlinearity (CAN) of ultrasonic caused by low-frequency vibration. The SDOF model for nonlinear wave modulation consists of modal mass, modal damping and modal stiffness which coefficient fluctuates caused by CAN of ultrasonic vibration. This model is described by time-varying linear model when the frequency ratio of the frequency of low-frequency vibration to frequency of ultrasonic vibration is sufficiently small. When the fluctuation frequency of coefficient of modal stiffness caused by low-frequency vibration is sufficiently smaller than the frequency of ultrasonic vibration, the instantaneous natural frequency of ultrasonic vibration fluctuates in synchronization with fluctuation of time-varying coefficient of modal stiffness. Therefore, the fluctuation of natural frequency can be used as a novel index for evaluation of failure level independent of viscous damping. In this paper, the estimation method of fluctuation of the natural frequency is proposed and verified using time response analysis. Firstly, the linear time-varying model of nonlinear wave modulation is introduced. The mechanism of fluctuation of natural frequency is explained by introduced model. Secondly, the estimation method of fluctuation of natural frequency based on the linear time-varying model is proposed. The phase fluctuation occurs as the result of the fluctuation of natural frequency. Finally, it is confirmed that the fluctuation of natural frequency can be estimated from time-invariant transfer function and phase modulation. The fluctuation range of natural frequency is the failure index.

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非线性波调制引起的固有频率波动对接触型故障发展的评价(时间响应分析估计固有频率波动方法的验证)

提出了一种基于非线性波调制的接触型失效水平评估方法。使用线性超声检查很难检测到接触型故障。提出了一种基于非线性波调制的接触式故障检测方法。非线性波调制现象是由低频振动引起的超声波接触声非线性(CAN)来解释的。非线性波调制的SDOF模型由模态质量、模态阻尼和模态刚度组成，其中模态质量、模态阻尼和模态刚度系数的波动是由超声振动CAN引起的。当低频振动频率与超声振动频率之比足够小时，该模型用时变线性模型来描述。当低频振动引起的模态刚度系数波动频率小于超声振动频率时，超声振动的瞬时固有频率与时变模态刚度系数的波动同步。因此，固有频率的波动可以作为一种新的不依赖于粘性阻尼的失效程度评价指标。本文提出了固有频率波动的估计方法，并利用时响应分析进行了验证。首先，介绍了非线性波调制的线性时变模型。用引入的模型解释了固有频率波动的机理。其次，提出了基于线性时变模型的固有频率波动估计方法。相位波动是固有频率波动的结果。最后，通过定常传递函数和相位调制，证实了固有频率的波动可以估计出来。固有频率波动范围即为失效指标。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Transactions of the JSME (in Japanese)

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