The target of statistical analyses for industrial accident occurrence is to provide various basic information for the decision making on the policy of loss prevention or risk management. For this purpose, it is required that the characterizing and evaluating of the potential risk of accident occurrence could be performed from the results of statistical analyses. This paper proposes a new statistical technique which can give a quantitative index to characterize the potential risk of industrial accident occurrence for many engineering systems. An approach taken in this study is based on the concept of the risk curve, in which the relationship between exceedance cumulative0frequencies and their corresponding magnitude of consequence for hazardous events is described in log-log scale. The representation of the risk for accident occurrence has been examined with the definition of risks considered by Kalpan and Garrick, and the result showed that the risk curves have been clarified to be of characterizing the risk of hazardous events. Furthermore, using a lot of collected actual accident data it was found that the risk curve can be essentially expressed with a mathematical form uniquely determined by one distribution parameter. This parameter characterizing the risk curve means the index as a measure of risk for accident occurrences. It was concluded that a possible method for statistically assessing risks of accident occurrence adopts this index (safety index). Finally, the application of the proposed methodolgy to risk evaluation for damages of equipments and materials will be presented

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This paper proposes a diagnostic method of bearing in sump pumps in nuclear power plants. The method measures the distance from the casing to the shaft by moving an ultrasonic sensor on the casing surface and diagnoses the anomaly of the bearing by solving the two dimensional movement of the shaft by analyzing the two types of outputs of the ultrasonic sensor.

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It is of great significance to deeply understand the characteristics of wave propagation in austenitic steel welds for precisely detecting and sizing flaws in welding areas or heat affected zones. In this paper, ultrasound, excited by a focal longitudinal type transducer in austenitic steel welding areas, is performed by finite element method, where Ogilvy's model for austenitic welds used in ray tracing is applied. The numerical results show that longitudinal waves propagate easily through the weld and longitudinal diffracted waves from a notch tip are much stronger than shear diffracted ones. Shear waves, however, are refracted in the weld and make their way to the bottom of weld. Numerical predictions of received echoes are in good agreement with the relative experimental measurements.

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Acoustic diagnosis system with condenser microphone has some attractive characters what is more cheap for cost of devices of sensor, is not keeping contact with machinery components and is wide band range on frequency compare with piezoelectric accelerometers. This paper proposes a method to do condition diagnosis about non stationary signal generated by operating rotary machineries which are a rolling bearing. Especially, a signal processing technique in order to eliminate non stationary noises including operating sound is described by adopting locally stationary AR model a kind of system identification. Further, the optimum order of locally stationary AR model is determined from presumption of division terms. The effectiveness of this method has been identified by experimentation based on a rotary simulator device on a rolling bearing.

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While control valves are used in many plants, most of the breakdown problems occur due to leakage of working fluid from grand packing. The primary cause of the leakage is stress relaxation of the grand packing. In this research, we proposed new method of measuring pressure of grand packing to evaluate mechanical properties of the grand packing. First, we verified that measurement of the radial pressure distribution is possible by using grease and pressure sensors for fluid. Next, making use of the method, a measuring device based on actual valve was developed, which can measure the axial pressure and the radial pressure distribution of grand packing simultaneously. Therefore, experimental results showed that the radial pressure is high as upper and the relation between the radial pressure and the axial pressure is proportional.

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Strange sounds generated by machines are expressed by onomatopoeia. And onomatopoeia expresses trouble or poor condition of the machines. Especially, many kinds of onomatopoeia are used for expressing strange sound of automobiles, and the relationship between onomatopoeia and the sources of strange sound is reported. In this study application of onomatopoeia for expressing strange sound is discussed. In order to solve the above matter, we chose onomatopoeia, which is used well. Sounds were made on the basis of word information of onomatopoeia. We performed the auditory sensory tests by using the prepared sounds. Furthermore, the actual sounds and the vocalized sounds were analyzed by using a one-third-octave analyzer. By comparing the auditory sensory test results with actual sound, we clarified that a frequency range of a sound regarded as an onomatopoeia almost corresponds to peak frequency of an actual sound. And we investigated relationship between the auditory sensory test results and the vocalized sounds, too.

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In recent years, a lot of industrial production facilities are superannuating. These production facilities are required the high reliability. Therefore, it is important to do preservation activities before accident. However, these production facilities are used in an unfavorable environment due to many corrosive gases, humidity and etc. We are researching the damage factor of electric equipment receive by such environments. Then, we proposed the evaluating method of the complex environmental quantitative stress by such environments and the expressing method of the stress from environment numerically, temperature, humidity, gas concentration, and so on. Moreover, the washing method in order to stop degradation and realizing recovery of function for the electrical equipment from environmental influence and calamity was reported herein.

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The objective was to apply a structural health monitoring concept to detect loosening of a bolt without human involvement. This paper proposes a new method of a bolt loosening detection by adopting a smart washer which uses a piezoelectric material with sub-space state spacce identification algorithm (4SID). The proposed washer is a cantilevered plate type patched piezoelectric material. A self-sensing and actuation function featuring this material is applied to the washer. An explanation that natural frequency decreases with decrease of the bolt tightening axial tension by using the system identification, the concept of the proposed method and experiments verifying its effectiveness are described. The natural frequency of the smart washer was identified with sub-space state space identification method. There was good correlation between the change of the natural frequency of the smart washer system and the decrement of bolt tightening axial tension.

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Life styles based on mass consumption and mass abandonment, which have been made possible by mass production, need to be rethought from the viewpoints of global environmental problems and future shortages of fossil energy resources. For power equiment and power systems, the life extension of power equipment using various diagnosis techniques is an important subject. The larger in size systems become, the more serious the damage to them becomes. Therefore, more sophisticated diagnosis technologies are required. In previous paper, an estimation method for vibrations and forces inside gas insulated switchgear, which are caused by an abnormal condition was discussed. The values and locations of inside forces were estimated by solving an inverse problem of vibrations using calculations and experiments. In the calculations, up to 50 force locations were well estimated while in experiments, up to 6 force locations were. Then, when the locations of inside forces do not agree with the location used to measure the transfer function, a new estimation technique which uses two or three exciting and observing points multiple times and searches for the real location of the inside forces successively, was proposed. In this paper, the accuracy of the new estimation technique was discussed for various vibration models. In some frequency, it is difficult to obtain an accurate result. This is because a single vibration mode is dominant. Even if the dimension of the matrix is very small, such as 2 the inverse problem becomes ill-conditioned.

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The parameter identification was very important in research areas including parameterization of joints and boundary conditions, model structure determination and model-based damage detection. In many cases, a beam is not uniform and is not supported rigidly. Boundary condition is unknown. To estimate the joint failure and to identify parameters of the beam itself, we must identify the parameters of the beam and the joint failure at the same time. In this paper, we tried to identify the density and the elasticity of the beam with uncertain support and then estimated the joint parameters from image processing data.

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This paper describes a study on crack detection of roof tiles by using damping factor of the vibration response with impact test. Damping ratio of roof tiles are calculated from logarithmic amplitude of the envelope of response for each natural frequency. The envelope of response is obtained from the analytic signal that has a real part which is the vibration response and an imaginary part which contains the Hilbert transform. Damping ratio for several natural frequencies of a roof tile become large greatly by a crack. Others are almost changeless. The relations between the variation of damping ratio by a crack and the vibration mode shapes are investigated by using experimental modal analysis. The result shows that a crack on a roof tile can be detected by the variation of damping ratios.

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In this paper a new algorithm for classification and real-time recognition of different (Preliminary assumed) operating modes for construction machines is proposed. This algorithm utilizes the effectiveness of the Self-Organizing Maps (SOM) for creating the so called Separation Models, that are able to distinguish each operation mode separately. After training, these models are used in a real-time procedure, which calculates at each sampling time the minimal Euclidean distances from the current data point to certain node of each SOM. The Separation Medel (SOM) that has produced the least minimal distance determines the number (class) of the operating mode. Simulation results. and consequent analysis, based on experimental data from a hydraulic excavator have shown that the proposed algorithm clearly leads to a higher percentage of true recognitions.

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In order to disseminate distributed energy systems an autonomous abnormal diagnosis is imperative. The purpose of this study is to develop the abnormal diagnosis method using the fieldbus technology, which makes it possible to share much information of field devices. At the first stage, the authors constructed a experimental apparatus of a heat exchanging process and a measurement and control system with fieldbus devices and developed two types of two types of the abnormal diagnosis method for the air retention to the shell of the heat exchanger : the monitoring of the overall heat transfer coefficient as the representative process parameter and the monitoring of the correlation between the condensing pressure and the condensing temperature as a simpler method. The experimental results show their effectiveness and features.

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So far, many techniques for detecting cracks in structures using dynamical response have been proposed. Most of them assume that the cracks are open crack, which does not close during vibration. However many of actual cracks are breathing crack which opens and closes during vibration. In this paper, a technique for detecting breathing cracks in a beam using dynamical response is proposed. When a breathing crack opens, it reduces flexural rigidity of the beam locally. The proposed technique introduces parameters that express the reduction in the flexural rigidity, and determines values of the parameters such that they yield the closest responses to measured ones. In order to check applicability of the proposed technique numerical simulation is conducted.

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In this study, the dynamic model of horizontal vibration of two kinds of shaft misalignment state is proposed for the dynamic analysis and diagnosis of shaft misalignment state. In order to obtained the solution of the vibration equations and clarify the feature of the vibration signal measured in shaft misalignment states, we show the calculation method of vibration forces caused by misalignments. The results of computer simulations and experiments using rotating machine are also shown to verify the efficiency of the dynamic analysis method proposed in this paper. Finally, the method for distinguishing shaft misalignment state from imbalance state is discussed.

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Electromagnetic acoustic resonance (EMAR) is a contactless resonant method with an electromagnetic acoustic transducer (EMAT). This method is free from extra energy losses, resulting in the measurement of intrinsic ultrasonic attenuation in solids. In this study, the EMAR was applied to detect the creep damage of a stainless steel. The material was exposed to the temperature of 973K at various stresses. We measured ultrasonic attenuation for 1-6-MHz frequency range as the creep advanced. The attenuation coefficient exhibits much larger sensitivity to the damage accumulation than the velocity. It shows a maximum around 40% of the whole life, which is interpreted as resulting from microstructural changes, especially, dislocation mobility. This is supported by TEM observations for dislocation structure. This technique has a potential to assess the damage advance and to predict the creep life of metals.

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Nonlinear ultrasound in the solid is expected as the promising tool for evaluating a crack which is difficult to evaluate with the linear ultrasound. We developed a procedure to introduce closed fatigue crack and controlled a crack closure accurately using tensile load during nonlinear ultrasonic testing. Transmitted echoes through the crack were analyzed with FFT varying the applied tensile load and the amplitude of incident ultrasound. As the results, especially in the case of oblique incidence, the strong subharmonic wave found to be appeared in addition to the superharmonics. Details of the subharmonic wave behaviors due to a crack closure were investigated and the mechanism of the subharmonic wave also discussed. Amplitude of the peak frequency of the subharmonic wave found to be a tool for monitoring the crack closure.

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In order to achieve the high efficiencies demand of industrial gas turbine (GT) combined cycle systems, it is necessary to operate the GT with high turbine inlet temperatures. Currently, gas temperatures at the combustor exit are around 1450 ℃, and combined cycle efficiencies of 50percent have been achieved. The use of ceramic coating on the component surfaces to provide a thermal barrier offers even more thermal protection. In this paper, eddy current testing for measurements of the thicknesses of thermal barrier coatings (TBCs) and artificial detects is described, and initial results are presented from measurements made with TBCs produced by air plasma spray and with CoNiCrAlY-type bond coats for flat surfaces.

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Crack is the most dangerous defect in machines and structures. Cracking often initiates from the surface of materials, since the surface stress is often higher than the stress of inside when a metal is under load. Nondestructive evaluation of a small crack is always regarded as a difficult but an utmost important issue for the integrity assessment of structural components. Recently, small cracks have been detected successfully by using microwaves under a condition of no contact and without any coupling medium, and a dual frequency technique has been developed to evaluate the size of surface cracks in metals. In the present paper, a study of evaluation of the shape and size of 3-D cracks using an enhanced microwave dual frequency technique is reported.

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This paper describes a new data processing technique used in the pulse heating thermographic NDT. The surface temperature after heating is measured by high-speed infrared camera. The shape of transient temperature descent curve, which reflects defect parameters such as depth and size, was analyzed by the Fourier series. It was found that the coefficient of the Fourier series, a_n, b_n, were effectively used to determine depth and size of the defects. This method was applied successfully to the detection and quantitative measurement of impact delamination damages in the advance CFRP plates and material loss defects in steel plates.

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