Pipes in power plants tend to be damaged at the pipe elbows and lower reach of orifices by Flow accelerated corrosion and erosion. As one of the conventional techniques, an ultrasonic thickness meter is generally used to measure the main pipe thickness and detect the corrosion wastage in power generation plants. However, this requires plant outage time and cost to dismantle and reassemble the heat-insulating coat of the pipes. To solve these problems, we developed a new measuring technology by combining Electromagnetic Acoustic Transducer (EMAT) and Fiber-Optic sensors. Since it can be put between the pipe and the heat insulator, this sensor enables us to measure and monitor the thickness of the pipe online. This report describes both high-temperature endurance and resistance to radiation of junction of sensors with pipes.

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To date, the non-destructive testing (NDT) is mainly realized by using ultrasonic inspection, X-ray inspection, eddy-current testing and magnetic-particle testing, etc. These inspection methods have high accuracy and reliability. However, they also have some disadvantages. For instance, a long inspection time is usually needed because the inspection area in these methods is relatively narrow at one time. To overcome this weak point, the damage inspection techniques with Lamb waves which can detect a wide area due to their long-distance propagation ability are actively studied in recent years. In the present work, based on an inverse algorithm, a tomographic reconstruction technique of damage image, e.g., the area and shape of a damage, by using the amplitude decrease of the transmitted Lamb wave through the damage, is proposed. From the obtained experimental results, the validity of the proposed method for reconstructing the damage image is verified. This method can be also applicable to the case where multiple damages exist in the inspected area.

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As for social infrastructures such as a lot of bridges and tunnels that have been constructed in various places since the high economic growth age of postwar days, deterioration is serious, and taking action to the deterioration of infrastructures is desirable. In this research, we aim to develop the robot that can inspect cracks and corrosion under the steel bridge. We make a four-wheel driving robot for trial purposes, and it can ambulate and climb vertically. Strong permanent magnets are installed on the edge parts in the wheels. This robot does not fall by gravitation when it climbs a steel wall or runs along the ceiling upside down. The running performance of the robot is examined by the driving experiment and by the analysis by using software DYMOLA.

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Machine condition monitoring and diagnosis have become increasingly important, and the application of these processes to beam structures and rotating machinery has been widely investigated. The authors previously proposed a stepwise primary diagnosis method using a force identification approach. The method is that the location of the abnormality is firstly estimated using the force identification approach based on the transfer function. It is considered that more accurate identification result can be obtained by using more measurement points, however, huge number of sensors cannot be used for the actual application. In this paper, the possibility of improvement of the diagnosis accuracy by using the virtual sensors, that is, by using a lot of sensors, is investigated by a numerical example. As a result, it was shown that the accuracy of identification of abnormality location can be improved by using many sensors, and the virtual sensors have little effect on the accuracy of diagnosis.

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This study concerns damage localization method based on nonlinear elastic wave modulation spectroscopy. When fragments of a contact-type damage is rupping and crapping in synchronization with the 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 thi modulation propagates through the structure with the group velocity, it may be possible to estimate damage location by measurering the modulation and performing an inverse analysis based on the wave propagation model. In this paper a mathematical model of the phase modulation propagation on a Timoshenko beam is constructed, and by considering the damage as a source of the modulation wave, a localization algorithm which utilizes the time difference between the demodulated waves measured by sensor arrays located at both sides of the damage is proposed, and examind experimentally.

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Pre-failure damage behaviors of different materials (ductile cast iron, steel) have been investigated by acoustic emission (AE) technique. As spheroidal graphite cast iron has high strength as well as excellent workability and damping capacity, it has been widely used as automobile and many other machine parts. In this study, the failure of the materials cased by cracks, micro-cracks have been investigated. AE data with different thresholds have been taken for analyzing the damages. CCD images with high resolutions have been taken for analyzing the deformation of the materials under different tensile loadings. The crack, micro-crack data has been investigated by using microscopic images with high resolutions and magnifications rate in a real time data processing system. The combination of above results has revealed the pre-failure damage characteristics of tested materials significantly.

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It is extremely important to measure the strain distribution of reinforced concrete structures and to detect the generated cracks location. Currently, the digital image correlation (DIC) method is applied for measuring technique. However, the DIC method has several problems concerning accuracy; an out-of-plane deformation of structures has an adverse effect on the strain measurement accuracy. For improving the strain measurement accuracy of the DIC method, it is essential to compensate the equivalent strain owing to the out-of-plane deformation of the measurement objects. Therefore, it is necessary to measure the three-dimensional surface geometrization using the stereo camera system. This paper discusses the crack generating detection technique of reinforced concrete structure using the three-dimensional method measurement based on the stereo camera system. In particular, the previously our proposed compensation method for the equivalent strain is used. As a result, it is found that the three-dimensional measurement method based on stereo camera system with our compensation method is superior to existing both the strain distribution and the crack generating detection technique, on a basis of a series of experimental examination using the large-scale four-point bending test.

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This paper presents a method to identify the geometrical shape and the location of the defect embedded in a concrete structure by processing nonstationary thermal images of the structural surface captured by an infrared thermography camera. In the proposed method, the structure is modeled as a homogeneous infinite plate whose boundary condition on the observed surface is known. The temperature field in the plate is represented by a truncated power series with respect to time, and a layer-by-layer inverse analysis scheme using a regularized interlayer transfer matrix based on 2D Fourier transform is carried out to obtain the sharper image of the failure as well as the depth of the damaged layer. The estimated depth is mapped as a depth image which displays the shape of the failure as well as their depth. Change passive heating to short active heating, create shape and depth image using thermal image in cooling process after active heating.

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This paper proposes an innovative vibration testing method for membrane structures based on impulse response excited by laser. Non-contact impulse force can be applied to a structure by using a shock wave generated by laser-induced breakdown in air. A high-power YAG pulse laser is used in the present vibration testing system for generating the laser-induced breakdown in acoustic fields. The laser excitation makes a precise measurement of the frequency response in wide frequency range possible because an ideal impulse force is applied to a point on the structure. Using a laser Doppler vibrometer to detect a response of the structure, both non-contact laser excitation and measurement are achieved in the vibration testing system. Furthermore, vibration mode shapes of the membrane structure can be extracted by conducting a multi-point measurement. The validity of the present vibration testing system is verified by measuring the frequency response data and extracting the mode shapes of a square Kapton membrane structure.

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Magnetic resonance elastography (MRE) is non-invasive method to identify elastic modulus distribution of human body by magnetic resonance imaging (MRI). MRE measures displacements of elastic wave propagation in response to excitation on the surface of human body. This data is transformed into elastic modulus distribution in human body by solving inverse problem about viscoelastic body model. In this study, vibration analysis based on modal analysis is conducted to the finite element (FE) model of a human body phantom as a part of the advancement in MRE. Elastic wave images of FE model and elastic modulus distribution recovered from the wave data are compared to results of MRE measurements, demonstrating high efficiency of FE analysis for MRE evaluation.

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This paper proposes a novel condition monitoring method on rotary machineries by fault vibration signals extraction algorithm based on the proposed Multiplex Elements Auto Regressive model with Single Input (MEAR-SI model), which can be removed influence of vibration signal components generated by other machineries located close range except for monitored and diagnosed rotary machinery elements. We intend to have attempted to demonstrate the effectiveness of the proposal MEAR-SI model and its extraction algorithm using an experimental rotary machine which, is constructed by a rotor, spur gears and rolling element bearings, which are connected to a drive and two driven shafts. The experimental machine can be artificially assumed three common faults such as the outer race fault of the rolling bearing, the unbalanced rotor and a wear of all gear teeth at the same time. Good results are obtained in this article, the ability of the proposal condition monitoring method (MEAR-SI model and its algorithm) is effectively identified.

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本研究では,機械設備に様々な種類の異常を高精度に検出・識別するために,回転機械の構造系異常(アンバランスやミスアライメント,締め付け具のゆるみ等)の検出・識別を実例として,信号融合法と多変量解析法(ハイブリッド主成分分析法)を用いた設備状態の自動診断法を提案し,回転機械の各種構造系異常状態の特徴を明らかにすると共に,信号融合法と多変量解析法による設備状態の簡易・精密診断の結果例を示す.

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本研究では、機械設備の異常を早期に検出・識別するために、測定した振動信号の特異値分解とフーリエ変換により信号中のノイズを除去する精度について比較検討し、サポートベクターマシンを用いて診断用の特徴パラメータの統合法及び可能性理論による逐次診断法を提案し、回転機械の構造系異常を早期に検出・診断した実例により提案した方法の有効性を検証した。

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Wire rope and lashing belt are conveniently being used in many places without knowing their tension. In terms of safety, it is important to know the magnitude of their tension to avoid accident. We developed a tension meter for wire rope and lashing belt by which the magnitude of their tension in use can be evaluated. The tension meter twists a small part of the target and evaluates the torque required for a twist. So far, it has been unclear where to set a reference point for twist angle due to an internal friction of wire rope. In this study, the reference point can be determined automatically by an electric control system so as to set the same twist angle. Regarding the lashing belt, there is no need to control the reference point as it has little internal friction. It was confirmed in the experiments that there is a linear relation between the tension and torque in both wire rope and lashing belt. In addition, the internal friction of wire rope is discussed using a simple model.

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Milling is one of the most important metal cutting processes. If we measure the cutting force, we can make cutting process optimum, prevent tool breakage, and improve efficiency of process. Especially in the case of using a micro end mill, it is very difficult to identify whether cutting process is good or not. In this paper, we proposed the cutting force measurement technique by using image processing. In the technique, we captured images of end mill during cutting process from x-y direction, determined deflection of the tool and then estimated cutting force. Finally we can estimate small cutting force in two-dimension plane.

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In recent years, the number of helicopters with vibration monitoring equipment, which is called Health and Usage Monitoring System, has increased around the world. The vibration monitoring is intended for condition based maintenance which is economically advantageous maintenance method. First SH-60K helicopter with vibration monitoring equipment was delivered for Japan Maritime Self-Defense Force in 2005. Mahalanobis Taguchi System (MTS) is applied to vibration monitoring method for helicopter's transmission. MTS is a method which evaluates the difference between a target signal and normal signal by Mahalanobis Distance. This paper shows an approach of SH-60K helicopter for vibration monitoring and experimental results intended to evaluate MTS.

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Reciprocating compressors have much repetition of maintenance as compared with other compression and long-term continuous operation is desired. In practice, the troubles of breakdowns have occurred in the connecting parts during operation. Thus, the importance is to understand the effects of the rigidity of the connecting parts on the dynamic behavior in reciprocating compressors. To this end, the present study treated the multi-body dynamics of the crankshaft-piston system using an analytical model with variable spring constants at the connecting parts. By the experimental measurements and simulation results confirmed the common resonance frequency. Further, the resonance peaks are consistent with the natural frequencies. From this, we may be able to estimate the internal state by simulation of the dynamic model.

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Lubricating oil is used in various machines and devices. However, lubricating oil is degraded with operating time or usage environment. Degradation causes of the lubricating oil are roughly classified into two types, one is caused by solid particle and other is caused by oil oxidation products. Diagnosis methods for solid particles in lubricating oils have many standards and researches. However, there are few diagnosis methods for oil oxidation products. Furthermore, oxidation degradation of the turbine basis oil becomes a serious problem in power generation plants recently. Therefore, on-site degradation diagnosis method which can detect the early stage of oxidation degradation of lubricating oil is desired for the proactive maintenance. In this study, we have developed degradation diagnosis method of lubrication oil which paid to the attention to coloration of the membrane patch with contamination. We prepared sample oils which were degraded by oxidation in the laboratory. We measured color parameters of membrane patches produced from sample oils using the colorimetric patch analyzer. As a result, we found that this method could detect the early stage of oxidation degradation of lubricating oil by measuring color parameters of membrane patch using the colorimetric patch analyzer.

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A wide-band vibration energy harvester using a Duffing-type nonlinear oscillator with self-excitation circuit is presented. For the conventional linear vibration energy harvester, the resonance frequency is matched to the source frequency, and the mechanical Q factor is designed as large as possible to maximize the oscillator's amplitude. The large Q factor, however, bounds the resonance in a narrow frequency band, and the performance of the vibration energy harvester can become extremely worse when the frequency of the vibration source fluctuates. As is well known, the resonance frequency band can be expanded by introducing the Duffing-type nonlinear oscillator. However, it is difficult for the nonlinear vibration energy harvester to maintain the regenerated power constant because such nonlinear oscillator can have multiple stable steady-state solutions in the resonance band. We introduce a self-excitation circuit with a variable resistance which has two values with negative (excitation mode) and positive (regeneration mode) switched depending on the response amplitude so as to enable the oscillator entrained by the excitation only in the large amplitude solution. In this paper, the energy flow in the excitation mode is analyzed for some specific cases to reveal how the negative resistance works to push the response back to the large amplitude solution, and the possibility of more power-efficient control algorithm is suggested.

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In the previous authors' study, the vibration energy harvester of the piezoelectric bimorph cantilever type was proposed for vibration condition monitoring applications of rotating machinery. Authors assumed that the typical casing or pedestal vibration amplitude of the rotating machinery was 0.71 mm/sec rms and this low intensity excitation condition was the input for experimental evaluation of the voltage generation performance of the piezocomposite vibration energy harvester. Proposed energy harvester consists of the surface bonded two Macro-Fiber Composites (MFCs). In this study, energy transfer efficiency was derived from the system energy balance during the natural period of the proposed vibration energy harvester. Energy balance equations were successfully obtained from the governing equations of the piezoelectrically coupled electro-mechanical system. In this study, the two types of cantilever, milling plate and thin plate, were used for evaluating the effect of the mechanical damping property of the clamped end. The maximum AC power of milling plate through 51.0 Kilo-Ohm resistor which includes instrument internal resistances experimentally obtained 408.8 microwatt at the resonant frequency of the harvester (58.40 Hz). The impedance matching between MFCs and the electrical resistive load was effective for maximizing AC power transfer of the vibration energy harvester. Estimated energy transfer from mechanical system to electrical system shows the agreement with the experimentally evaluated generating power during the natural period of the vibration energy harvester with about 3 (%) difference. Estimated energy transfer efficiency was about 30 % for different excitation magnitudes: 0.71, 0.568, and 0.355 mm/sec rms.

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In some areas of the leading-edge industry, hardware-in-the-loop (HIL) simulation is used in the development, instead of testing with physical machines. This paper describes the simulation method of abnormal vibrations on rotating machinery using HIL simulation, which aims to generate various abnormal vibrations instead of a rotor kit and study the effectiveness and convenience of HIL simulation through diagnostics using a latest vibration analysis system.

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