Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Nature   Participation form：Joint(The vice charge)  

This study aims to develop a multiple excitation system that improves the identification of modal parameters for the vibration testing of tires. Rubber, the main tire material, shows high damping characteristics. Therefore, the resonance peaks broaden, and it is difficult to identify the modal parameters. In the equations of motion, the damping force is proportional to the velocity of the equivalent mass and acts in the opposite direction of motion. This study proposes a novel multiple excitation testing method using velocity feedback control to counteract the damping force. The proposed method provides frequency response function (FRF) data with peak shapes. Three shakers were used to excite an automotive tire, and they were driven with forced vibration and velocity feedback signals. Using the proposed method resulted in shaped resonance peaks of the FRF and lower damping characteristics. Furthermore, the natural frequencies and mode shapes obtained by the proposed method was consistent with the single-shaker testing data obtained by the conventional method. Therefore, the proposed method primarily influences the damping characteristics of the vibration system as a target and facilitates the identification of modal parameters.

DOI： 10.1007/s00419-022-02318-8

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：COMADEM International   Participation form：Joint(The main charge)  

This paper presents a novel evaluation method of contact-type failure development based on nonlinear wave modulation utilising self-excited ultrasonic vibration. The contact-type failure, e.g. fatigue crack, delamination of composite material and debonding, is difficult to detect by using linear ultrasonic waves or vibrations. When the contact condition of the contact-type failure is fluctuated caused by structural low-frequency vibration, the amplitude and phase of ultrasonic waves passing nearby the failure area is fluctuated in synchronization with low-frequency vibration (nonlinear wave modulation). The fluctuation of natural frequencies caused by fluctuation of local contact stiffness is the cause of this amplitude and phase fluctuation. Therefore, frequency of ultrasonic natural vibration excited by local feedback control changes, chasing the change of natural frequency automatically. Thus, the frequency fluctuation of ultrasonic natural vibration in synchronization with low-frequency vibration (frequency modulation) occurs caused by nonlinear wave modulation. In this paper, the experimental investigation of proposed evaluation method is performed. Especially, the dependence of the proposed evaluation index of contact type failure on the viscous damping is clarified. Firstly, the design of an analogue circuit of local feedback control is explained. Secondly, it is confirmed that the self-excitation of ultrasonic natural vibrations can be implemented. Finally, it is clarified that the variation width of the frequency fluctuation is a novel evaluation index of contact-type failure level, which is independent from the variation of the viscous damping.

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Lecture Notes in Mechanical Engineering   Participation form：Joint(The main charge)  

This study concerns the evaluation method of contact-type failure, which is difficult to detect by linear ultrasonic because of transmission of ultrasonic at the contact surfaces utilizing frequency fluctuation caused by nonlinear wave modulation. When the contact-failure is vibrated by low-frequency vibration, the amplitude and phase of ultrasonic in the vicinity of the failure area is fluctuated in synchronization with low-frequency vibration (nonlinear wave modulation). This amplitude of amplitude fluctuation and phase fluctuation is the evaluation index of contact-type failure. However, the change in this index depends on the viscous damping of the structure. In the nonlinear wave modulation utilizing self-excited ultrasonic vibration, the frequency of ultrasonic vibration is fluctuated by low-frequency vibration. The frequency fluctuation may be the evaluation index of contact-type failure independent of the viscous damping of the structure. In this paper, the experimental verification using beam structure is done. Firstly, the self-excitation technique of ultrasonic natural vibration using feedback control is introduced. Secondarily, it is shown that the amplitude of frequency fluctuation is the evaluation index of contact-type failure by experiment. The uniform beam structure with simulated failure, which is simulated the contact-type failure is used. The vibration characteristics of this structure and the self-excited ultrasonic vibration excited by feedback control can measure easily. Finally, the viscous damping dependency of the frequency fluctuation is investigated. As the result, it is shown that the amplitude of frequency fluctuation is the evaluation index independent of viscous damping.

DOI： 10.1007/978-3-030-93639-6_14

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：日本機械学会   Participation form：Joint(The main charge)  

Contact-type failures, such as early-stage fatigue cracks, bolt loosening, and welding cracks, are difficult to detect with nondestructive inspection, which uses ultrasonic waves or vibrations. When a structure experiencing contact-type failure vibrates due to ultrasonic vibrations of two different frequencies, low-frequency vibrations with frequencies equal to the difference between the frequencies of the ultrasonic vibrations are generated due to local nonlinearity at the contact interface (frequency down-conversion). The detection methods of contact-type failure based on the frequency down-conversion of elastic waves or vibrations have been proposed. These detection methods can be applied using measurements with low-sampling rates. This study aims to develop a detection and localization method based on the frequency down-conversion of elastic vibrations. Low-frequency vibrations caused by frequency down-conversion are generated only if the structure has contact-type failure. Accordingly, contact-type failure can be regarded as the excitation point of low-frequency vibration caused by frequency down-conversion. Herein, a localization method of contact-type failure using the structural intensity as the localization method of the exciting location was proposed. First, an overview of the frequency down-conversion phenomenon is mentioned. Second, the theoretical investigation of the proposed localization method is explained, and the parametric excitation model that uses the Euler-Bernoulli beam is suggested. The equation transformation of the proposed model clarifies that the contact-type failure can be regarded as the exciting point of low-frequency vibration. Furthermore, from the results obtained herein, the location of contact-type failure was identified as the exciting point of low-frequency vibration caused by the frequency down-conversion. Finally, the basic performance of the proposed localization method was experimentally investigated. The exciting point can be localized from the sign change point of the structural intensity. Thus, the sign change point of the structural intensity of low-frequency vibrations caused by the frequency down-conversion is the contact-type failure location.

DOI： 10.1299/mej.21-00201

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of ASME 2021 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2021   Participation form：Joint(The main charge)  

The failure, e.g. fatigue crack, weld crack, and bolt loosening, of infra-structure is one of the causes of serious accidents. To prevent these accidents, structural health monitoring systems have been proposed. Among them, the evaluation methods by measurement of natural vibrations are useful for various structures because of ease in introducing a monitoring system. Currently, the natural vibrations at lowfrequency range are usually used because of the difficulty of exciting natural vibrations at high-frequency range. In this paper, the excitation method of natural vibrations by multi excitation using decentralized control is developed. Firstly, the difficulty of excitation of ultrasonic natural vibrations is confirmed. Secondly, the basic performance of the multiexcitation using decentralized control is investigated by the experiment using a simple beam structure. The excitation of an ultrasonic natural vibration in the case of multi-excitation using decentralized control with the self-excitation automatically is examined. From the phase differences between each measurement signal, it is clarified that mutual synchronization is realized. Thus, it is confirmed by the measurement of vibration mode shape that an ultrasonic natural vibration is excited. Finally, it is tried to excite another natural vibration by forced entrainment.

DOI： 10.1115/SMASIS2021-67457

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of ASME 2021 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2021   Participation form：Joint(The main charge)  

The contact-type failure, e.g. fatigue crack in early stage, delamination of composite material and adhesive failure, leads to the serious accidents. When the object with the contact-type failure vibrates due to ultrasonic vibrations of different frequencies, the interaction of the contact interfaces of failure occurs. As the result of this interaction, the low-frequency vibration, of which frequency is the difference frequency of ultrasonic vibrations, generates (Frequency down-conversion). The detection, evaluation and localization by measurement of structural intensity of low-frequency vibration caused by frequency down-conversion has been proposed. In this paper, the performance of the proposed method in the case of multiple contact-type failures is investigated. Firstly, the detection method of contact-type failure based on frequency downconversion of elastic vibrations is introduced. Overview of frequency down-conversion and the example of detection of contact-type failure is shown. Secondly, the proposed method for single failure is explained. By the measurement result of structural intensity of the low-frequency vibration caused by frequency down-conversion, it is confirmed that the contact-type failure can localize as the excitation point of low-frequency vibration. Finally, the influence of other failures on the localization accuracy is investigated. From these results, it is clarified that the contact-type failure, of which the excitation force of low-frequency vibration is the largest, only localizes.

DOI： 10.1115/SMASIS2021-67739

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：COMADEM International   Participation form：Joint(The main charge)  

In this paper, a novel method is proposed for detecting contact-type failure based on nonlinear wave modulation utilising ultrasonic vibration driven by selfexcitation. In particular, the purpose of this paper is to propose an evaluation index independent of the viscous damping of the contact-type failures. When
the structural element of an infrastructure with contact-type failures vibrates at low frequency caused by environmental disturbance or forced excitation, the
contact stiffness of failure fluctuates in synchronisation with low frequency. In this case, the transfer characteristic of ultrasonic vibration fluctuates due to
the fluctuation of contact stiffness. As a result, the amplitude and phase of ultrasonic vibration were modulated in synchronisation with low frequency
(nonlinear wave modulation). The essence of nonlinear wave modulation is the fluctuation of natural frequency caused by the fluctuation of modal stiffness.
Therefore, this phenomenon can be expressed as a time-varying system caused by the fluctuation of natural frequency. In this research, the concept of a
novel method for detecting contact-type failures utilising ultrasonic vibration driven by self-excitation was investigated using time response analysis. The
self-excitation method by feedback control (local feedback control) using collocated sensor and actuator is the excitation method of natural vibration
automatically. Therefore, the frequency of the ultrasonic vibration excited by local feedback control fluctuated simultaneous with the fluctuation of natural
frequency caused by nonlinear wave modulation. It is clarified that the fluctuation range of frequency of ultrasonic vibration corresponds to the evaluation
index of development of the contact-type failure independent of viscous damping.

Language：English   Publishing type：Research paper (international conference proceedings)   Participation form：Joint(The vice charge)  

This research aims to find a better design of cartilage plate used in myringoplasty, a surgical procedure to reconstruct the tympanic membrane (TM) of human middle ear when it is perforated. A detailed three-dimensional finite element model of human middle ear is created and used to investigate the effects of thickness variation of cartilage plate on sound transmission. The validity of the numerical model is verified by comparing the vibration response of the stapes footplate with that of the measurement results of other researchers under a sound pressure of 90 dB. Then, a reconstructed model is created by replacing an assumed perforation on the TM with a uniform thickness cartilage plate. Varying the thickness of cartilage plate from 0.1 mm to 0.7 mm, and evaluating the displacement of stapes footplate in a frequency range from 0.1 kHz to 10 kHz, frequency response analysis show that 0.3-0.5 mm models have the best performance than others. However, from the viewpoint of quality of life (QOL), there is still a large difference between the performance of reconstructed models and that of the heathy model. As a further investigation, instead of adopting a uniform thickness, the thickness of the cartilage plate is designed into several patterns by combination of thinner layers and thicker layers. The frequency response curves of some patterned models show better matching to the curve of healthy model than using uniform thickness plate. From these results, a further improvement can be expected by optimizing the pattern design.

Language：English   Publishing type：Research paper (international conference proceedings)   Participation form：Joint(The main charge)  

This study concerns the detection method of contact-type failure based on frequency down-conversion of elastic vibrations. Frequency down-conversion is the phenomenon caused by contact acoustic nonlinearity (CAN) caused by large amplitude ultrasonic vibrations. The contact condition is fluctuated by large amplitude ultrasonic vibration. In this condition, the scatter characteristic of another ultrasonic vibration, of which frequency is close to the large amplitude ultrasonic vibration, fluctuates. As this result, the low-frequency vibration, of which frequency is the difference frequency between two ultrasonic vibrations, generates. The detection method of the contact-type failure based on frequency down-conversion of elastic vibrations is useful to detect small failure. In this study, the novel detection and localization method by measurement of structural intensity of low-frequency vibration is proposed. Frequency down-conversion generates, only when the object has a contact-type failure. Therefore, the contact-type failure can be regarded as an exciting source of low-frequency vibration. The localization of contact-type failure realizes by the measurement of structural intensity of low-frequency vibration caused by frequency down-conversion as a detection method of exciting point. In this paper, the basic investigation of the proposed method is done by experiment using simple cantilever. Firstly, the vibration mode of low-frequency vibration caused by frequency down-conversion is measured. It is shown that the estimation of a failure location from vibration mode shape is difficult. Secondly, the concept of the proposed method is introduced. The structural intensity of the low-frequency vibration is calculated using the measured vibration mode. It is shown that the detection and localization of the contact-type failure can be realized by the measurement of the structural intensity. Finally, the basic investigation of the proposed method is done by experiment. It is confirmed that the sign of the structural intensity of low-frequency vibration caused by frequency down-conversion changed at the failure location.

Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

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.

DOI： 10.1299/transjsme.20-00105

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP Conference Series: Materials Science and Engineering   Participation form：Joint(The vice charge)  

© Published under licence by IOP Publishing Ltd. The purpose of this research is to investigate an appropriate design of the sliced cartilage used for the reconstruction of the tympanic membrane (TM). A great number of people are suffering from TM perforation caused by diseases or accidents. A surgical procedure, called cartilage myringoplasty, can save the people from hearing loss by replacing the damaged part of the membrane with thin-sliced cartilage. In this research, as the first step of designing the sliced cartilage, we established a three-dimensional finite element model of the human ear for numerical analysis. The ear model consists of the middle ear (TM, ossicular chain, ligaments, muscle), and inner ear cochlea. The joints between ear bones were also modelled with softer tissues. The analysis result of the frequency response shows a good correspondence with measurement results reported by other researchers. Then, using the numerical model, we investigated the optimal thickness of the cartilage plate. The TM was cut at the bottom position with a size of about 40% of TM and filled by cartilage plate with the thickness of 0.1mm to 0.7mm. Comparing with the frequency response of the healthy ear, we found that the optimal thickness of the plate is different in a various frequency range. The reason is considered as the difference of material properties between the membrane and the cartilage. Finally, to evaluate the performance of repaired models in all frequency range, we proposed an equation of matching rate as the evaluation equation. The results show that 0.5mm cartilage plate model shows a better performance at peak response area (600Hz-1kHz), and 0.3mm. cartilage plate model shows better average performance in the total frequency range.

DOI： 10.1088/1757-899X/886/1/012045

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP Conference Series: Materials Science and Engineering   Participation form：Joint(The main charge)  

© Published under licence by IOP Publishing Ltd. This research concerns the detection method of contact-type failure based on nonlinear wave modulation utilizing ultrasonic vibration driven by self-excitation. When the structure is vibrating by environmental force or forced excitation, the contact area is fluctuated by vibration. In this condition, the vibration transfer characteristics of ultrasonic vibration have fluctuated in synchronization with vibration (non-linear wave modulation). The detection method based on non-linear wave modulation can detect contact-type failure. In this paper, the novel detection method based on nonlinear wave modulation is presented. Firstly, the self-excitation method using local feedback control is introduced. Local feedback control can oscillate at the natural frequency automatically. Secondly, the concept of a novel detection method is introduced. When the structure with contact-type failure is vibrating, the frequency of the ultrasonic vibration excited by local feedback control will fluctuate in synchronization with natural frequency fluctuation. To explain the detection method, non-linear wave modulation is expressed 1 degree of freedom model. In this model, the local stiffness fluctuation is modelled by the spring element of which spring coefficient is fluctuated in synchronization with structural vibration. We regard the transfer function of this model as a linear time-varying system. The amplitude of the fluctuation of natural frequency caused by stiffness fluctuation can be the novel index of failure level. Lastly, the result of the experiment using the uniform beam specimen is shown. From the relationship between forcing pressure of the contact-type failure and the amplitude of the frequency modulation, it is proved that the novel index is associated with failure level.

DOI： 10.1088/1757-899X/886/1/012032

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Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

Driving at resonance point of the large degree of freedom and large damping vibration system is difficult because of crowd of natural frequencies and decreased peak of gain of transfer characteristics. To solve this problem, the multi-point excitation is effective. Centralized control as the general control method for multi-point excitation is the method to adjust the amplitude and frequency of all actuators and the phase difference between the adjacent actuators to suit modal shape of natural vibration. Therefore, to grasp the natural frequency, vibration mode of natural vibration is necessary. In this paper, the expansion to the large degree of freedom and large damping vibration system of the proposed decentralized control is proposed. Firstly, the difficulty of the driving at resonance point of large degree of freedom and large damping vibration system by centralized control and conventional decentralized control is explain. The self-excited vibration is generated at the frequency that has the highest peak gain of a loop transfer function. In the condition of crowd of natural frequencies, this method can excite only the particular natural vibration. Secondary, the cross feedback control is to excite the arbitrary natural vibration. The phase adjusting modal shape of natural vibration is fed back to adjacent actuator. Lastly, the adaptability for the change of damping caused by environment using damping element is verified. The influence of damping of the system in a loop transfer function is decrease by local feedback control as the active damping control. As the result, the amplitude of system maintains against the increase of damping.

DOI： 10.1299/transjsme.19-00422

Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

In aerial industry, to improve the mileage, workpiece such as jet engine turbine case has been lightened and thinned. However, cutting workpiece with thin-walled structure causes vibration called “chatter vibration of workpiece deformation type”. Chatter vibration affects not only processing accuracy but also wear of cutting tool. This paper describes chatter vibration generated in cutting thin-walled cylindrical workpiece. Firstly, by cutting various thickness workpieces, limit thickness and waveform of chatter vibration was investigated. In workpiece with axis length 200mm, 150mm and 100mm, vibration generation limit thickness is 16mm, 12mm and 4mm, respectively. Chatter vibration consists of sine mode vibration with node in tool position and cosine mode vibration with anti-node in tool position. Secondly, natural frequencies and natural vibration modes of the workpieces were measured. A thin-walled cylindrical workpiece has natural vibration similar to chatter vibration in frequency and vibration mode. When tool contacts workpiece, natural vibration is separate in 2 which are sine mode and cosine mode. Finally, coupling of two natural vibrations was investigated. Vibration system from thrust force to translational displacement (cosine mode) and vibration system from principal force to rotational displacement (sine mode) are coupled by two cross feedback in tool position. Cross feedback 1 is transfer characteristics from translational displacement to principal force, and cross feedback 2 is transfer characteristics from rotational displacement to thrust force. When the feedback system which consists of two natural vibration systems and two cross feedback becomes unstable, chatter vibration is generated.

DOI： 10.1299/transjsme.19-00335

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Smart Innovation, Systems and Technologies   Participation form：Joint(The main charge)  

© 2020, Springer Nature Switzerland AG. This paper introduces the concept of new detection method of contact-type failure based on nonlinear wave modulation utilizing ultrasonic vibration driven by self-excitation. It is difficult to detect the contact-type failure in standard inspection utilizing linear ultrasonic vibration. The constructional element of infrastructure is excited by environmental disturbance or forced excitation. In this situation, the contact condition of the failure fluctuates in synchronization with vibration. As this result, local stiffness in the vicinity of failure location fluctuates at the vibration frequency. Thereby, the amplitude and phase of ultrasonic vibration are modulated caused by local stiffness fluctuation (nonlinear wave modulation). This phenomenon can be expressed by a linear time-varying system caused by fluctuation of the natural frequency. In this paper, the new detection method of contact-type failure utilizing self-excited ultrasonic vibration is introduced. Firstly, the concept of detection method of contact-type damage based on nonlinear wave modulation is proposed. It is indicated from time history response analysis using single degree-of-freedom model of nonlinear wave modulation that the fluctuation amplitude of the amplitude and phase of ultrasonic as failure index varies depending on viscous damping. Secondly, the self-excited method utilizing local feedback control and characteristics are introduced. This method realizes oscillator which start to oscillate at the natural frequency automatically. Thus, the frequency of oscillation signal controlled by local feedback control is fluctuated in synchronization with fluctuation of natural frequency when nonlinear wave modulation occurred. Lastly, it is proved that the fluctuation amplitude of frequency of oscillation signal is the failure index independent of viscous damping.

DOI： 10.1007/978-3-030-57745-2_8

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本機械学会   Participation form：Joint(The main charge)  

Natural vibrations of acoustic space expand noise. Measurement of natural vibration is effective to reduce noise based on noise generation mechanism. Acoustic space has many natural vibrations in the noise frequency band. Multi-point excitation is useful for measuring natural vibration, which has mixed modes and high damping. Furthermore, it is necessary to cancel the influence of dumping to excite the modes individually. In this study, the new measurement principle of natural vibrations of acoustic space by multi-point excitation using decentralized control with local feedback control is proposed. An excitation system with local feedback control excites natural vibration without frequency adjustment and cancels damping in acoustic space. Excitation systems with decentralized control can have multi-point excitation without any adjustment of amplitude and phase each other. The proposed acoustic excitation system consists of a speaker, a microphone and a local feedback controller. The controller generates negative damping according to the sound pressure detected by the microphone and feeds it to the speaker. Firstly, it is confirmed that one acoustic excitation system is self-excited at resonance frequency and some resonance peak of the transfer function is sharpened by canceling the effect of damping. Secondly, multi-point excitation using decentralized control using four acoustic excitation systems is performed to excite many modes. All supposed modes are excited without adjustment of the excitation systems according to mode such as amplitude and phase. Finally, it is confirmed that acoustic excitation system has no limitation on the number of installations and has extensibility for higher-order mode excitation.

DOI： 10.1299/transjsme.18-00449

Language：English   Publishing type：Research paper (international conference proceedings)   Participation form：Joint(The main charge)  

Natural vibrations of acoustic space expand noise. To reduce noise based on mechanism, measurements of natural vibration is effective. Acoustic space has many natural vibrations with damping
in the noise frequency band. Multi-point excitation is useful for measuring natural vibration,
which has mixed modes. Furthermore, it is necessary to cancel the influence of dumping to excite the modes individually. In this study, the measurement technique of natural vibrations of
acoustic space by multi-point excitation using decentralized control with local feedback control
is proposed. An excitation system with local feedback control excites natural vibration without
frequency adjustment and cancels damping in acoustic space. Excitation systems with decentralized control can have multi-point excitation without any adjustment of phase and amplitude each
other. The acoustic excitation system consists of a speaker, a microphone and a local feedback
controller. The controller generates negative damping according to the sound pressure detected
by the microphone and feeds it to the speaker. Firstly, it is confirmed that one acoustic excitation
system is self-oscillate at resonance frequency and some resonance peak of the transfer function
is sharpened by canceling the effect of damping. Secondly, to excite many modes, multi-point
excitation using decentralized control is performed using four acoustic excitation systems. All
supposed modes are excited without adjustment of the excitation systems according to mode such
as amplitude and phase. Finally, it is confirmed that acoustic excitation system has no limitation
on the number of installations and has extensibility for higher-order mode excitation.

Language：English   Publishing type：Research paper (international conference proceedings)   Participation form：Joint(The vice charge)  

This study concerns adhesive failure detection of bonded joint in a structure by utilizing a sensitive baseline-free structural health monitoring methodology referred to as nonlinear piezoelectric impedance modulation method. According to the progress of adhesion technologies, adhesion joints have been used more often replacing conventional mechanical joints such as bolted and riveted joints. Thus, a nondestructive technique, which can detect and monitor the development of adhesive failures in-situ to investigate the health state of adhesive joints would be required. This technique evaluates failures in the structure under the pump excitation at low frequency, by demodulating the current response in amplitude and phase when a PZT patch on the surface is driven by a high frequency probe voltage source. It has distinctive features of being sensitive to incipient defects inside the structure and theoretically baseline-free because no modulation exists in a structure, which has no defect. In this study, thin plate specimens with bonded parts in healthy and incomplete conditions are subjected to the probe and pump excitations, and the resultant damage evaluation indices are investigated in terms of the probe and pump amplitudes.

DOI： 10.1299/jsmemovic.2014.12._2B21-1_

Language：English   Publishing type：Research paper (international conference proceedings)   Participation form：Joint(The main charge)  

This study presents the integrity diagnosis method of the bolted joint based on nonlinear wave modulation. When the structure that has the contact interface is vibrating at low-frequency, the contact interface is tapping and clapping due to low-frequency vibration. In this condition, the scatter characteristics, such as wave transmissivity and reflectivity, of high-frequency waves in vicinity of the contact interface are fluctuated in synchronization with low-frequency excitation because of the contact acoustic nonlinearity. The time fluctuation of reflection intensity, which expresses the reflectivity in the specific location, of high-frequency waves at the contact interface is given as the reflection intensity map which plots time-spatial map. In this paper, experiment using the beam specimen which has single bolted joint is conducted to examine the performance of the evaluation index based on the fluctuation amplitude of reflection intensity.

DOI： 10.1115/DETC2014-34879

Language：English   Publishing type：Research paper (international conference proceedings)   Participation form：Joint(The main charge)  

This study presents the detection and localization method of contact-type failure based on the reflectivity modulation which is the reflectivity fluctuation caused by nonlinear wave modulation. When the structure including contact-type failure, such as fatigue crack, delamination of composite material and bolt loosening, is vibrating at low-frequency, the contact interfaces are breathing due to low-frequency vibration. Then, the scatter characteristics of high-frequency waves, such as wave transmisivirity and reflectivity, in the vicinity of the contact-type failure are fluctuated in synchronization with low-frequency vibration. The fluctuation of the reflection intensity of high-frequency waves which expresses the reflectivity in the specific location is given at the location of the contact-type failure. So, the time-spatial map of the reflection intensity can figure out the location of contact-type failure as the reflectivity fluctuation point. Especially, in this paper, the theory of some contact-type failures detection based on the reflection intensity fluctuation caused by nonlinear wave modulation is proposed, and investigated for a beam specimen which has some simulated contact-type failures experimentally.

DOI： 10.1299/jsmemovic.2014.12._2B22-1_

Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

This paper concerns the estimation method of damage location based on the nonlinear wave modulation demodulation which has attracted much attention in the field of structural health monitoring. When a structure containing a contact-type damage is subjected to a low-frequency vibration, a high-frequency wave which propagates through the damage may undergo amplitude and phase modulation at the damage location because the scatter characteristics of high-frequency waves in the vicinity of the damage may fluctuate in synchronization with the low-frequency vibration because of the contact acoustic nonlinearity. Since this modulation propagates through the structure with the group velocity, it may be possible to estimte damage location by measuring the modulation and performing an inverse analysis based on the wave propagation model. In this paper, a mathematical model of the modulation propagation on a Timoshenko beam is constructed, and by considering the damage as a source of the modulation, an estimation algorithm of damage location which utilizes the time difference between the modulated waves measured by sensor arrays located at both sides of the damage is proposed, and examined experimentally.

DOI： 10.1299/kikaic.79.1594

Award type：Award from international society, conference, symposium, etc.  Country：Thailand

Award type：Award from international society, conference, symposium, etc.  Country：Thailand

Award type：Award from publisher, newspaper, foundation, etc.  Country：Japan

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京大学 駒場リサーチキャンパス  

DOI： 10.11517/jsaisigtwo.2024.SMSHM-001_23

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学東山キャンパス  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：English   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Audience： Teachers