In this study, we develop a high-speed, high-resolution vision system that enables real-time measurement of deflection displacement distribution in cranes with long beam structures. It can measure dynamic displacement distribution with sub-pixel accuracy in real time by executing digital image correlation for 4096×904 images at 100 fps. Millimeter-level deflections at tens of points on a crane are measurable with the position of its moving load when a camera is tens of meters away from the crane. The trolly of a crane indicates the load position, and our system can also analyze deflection influence lines at all points on the crane as speed-invariant features that indicate its structural property. The effectiveness of our vision-based displacement measurement is demonstrated by showing experimental results for (1) a 1-m-length belt conveyor, and (2) an unloader crane with a 98-m beam structure operating in ironworks.

Large structures, such as bridges or unloader cranes in a steel plant, require health inspection methods to monitor their operation. Optical inspection methods offer numerous advantages for these large structures compared to traditional contact-based inspection methods. The sampling moire method is one such phase analysis method. Its features include high precision and non-contact field inspection. When measuring large structures, the measuring instruments are often positioned far away, sometimes several hundred meters, from the target. Calibration of such larger structures while in motion is nearly impossible. In this paper, the authors propose a calibration-free sampling moire method for measuring 3-axis displacements. This method initially measures the angles between cameras and the target. Subsequently, these angles are used to calculate a coefficient array, which translates phase differences into displacement values. Thus, the proposed method enables measurement of larger structures situated at a distance. Indoor experiments were conducted to verify the principles of the proposed method, and outdoor experiments were performed in a real steel plant to measure the displacements of an actual unloader crane. The results demonstrate that the proposed method can accurately measure the displacements of a working unloader crane.

This study aims to identify structural damage in beams subjected to moving loads using the rate of change of the time history response of non-dimensional displacements. We analyze the time response of displacements of beams subjected to moving loads using the finite element method. The structural damage of the beam is simulated by changing the cross-sectional shape of the beam in a part of the section. The analysis results show that damage cannot be identified by the displacement time-history response alone but can be identified using the change rate of the displacement time-history response. Furthermore, it is shown that damage can be identified independent of the magnitude and velocity of the moving load by using the rate of change of the non-dimensional displacement time history response. These results suggest that our method can be used to identify damage in actual structures subjected to moving loads.

This study proposes a novel approach to structural health monitoring through active structure sensing using a high-resolution camera for deflection distribution measurement under operational conditions. With the increasing the number of aging social and plant infrastructures, structure health monitoring becomes crucial for early detection of structural anomalies due to deterioration. Conventional contact sensors like strain gauges and accelerometers face challenges in installation and structural limitations, and confine frequent inspections to infrastructures under operation regulations and elevating inspection costs. This study introduces an active sensing method that captures the effects of load passage on deflection displacement around structural anomalies of infrastructures in operating with moving loads, and dimensionless deflection influence lines are defined as speed- and weight-invariant features in active structure sensing. Their effectiveness for structural anomaly detection is validated by showing dimensionless deflection influence lines when loads are moving on 3-m-length H section metal beams.

This study proposes a novel video-based conveyor monitoring method that can estimate distances between belt-supporting rollers by analyzing belt vibration responses in high-frame-rate (HFR) images. Focusing on the fact that the vibration components of a belt include frequencies inversely proportional to the distance between its ends, roller-to-roller distances that correspond to the state of contact between a belt and rollers are estimated by HFR-video-based analysis that can detect vibration peak frequencies at multiple belt positions without directly observing them captured in images. Its effectiveness was verified by conducting a wide-area monitoring test of a material handing conveyor in ironworks for roller-to-roller distance estimation with vibration frequency analysis at multiple points on its several-tens-of-meters belt in 9344×600 images captured at 300 fps.

Neutron Bragg-edge transmission analysis was performed at a newly constructed compact neutron source, AISTANS, for 30Mn-C austenitic steels and ferrite-bainite-retrained austenite (TR) steels, which had previously been measured at BL22, RADEN, in J-PARC MLF. Employing a newly developed 2D Li-glass neutron detector, Bragg-edge spectra were obtained at 1 kW electron-beam operation of AISTANS. The obtained profiles were analyzed using the RITS code. In 30Mn-C steels, the determined lattice parameters were found to show a linear dependence with carbon content, similarly to the results obtained at RADEN. In TR steels, Bragg-edge spectra obtained from three orthogonal directions were differently shaped each other stemmed from the texture. Reasonable fitting was obtained only in the cases in which the influence of texture was weak; the profile obtained along the rolling direction or averaged one of the three directional results.

For small samples for which tensile tests cannot be conducted, methods have been developed to estimate stress-strain relationships using indentation tests and analysis models that simulate these tests. However, precise modeling of factors such as wear at the indenter tip and friction coefficients between the indenter and material is challenging. A few examples are applied to small regions, such as single crystal grains, using small loads. In this study, we developed a method to estimate stress-strain relationships based on the work-hardening law from load-displacement curves and hardness measured by pyramidal indentation tests. Using the presented method, we evaluated the stress-strain relationships from nanoindentation test results obtained under a load of five mN and results from micro-Vickers hardness tests conducted under a load of 10 N. While micro-Vickers test results estimated curves similar to tensile test results, the estimation accuracy decreased for nanoindentation tests with lower loads. This reduction in accuracy is attributed to the size effect of hardness, which occurs under low-load conditions. To improve the estimation accuracy under low-load conditions, we determined correction coefficients to reduce the influence of the size effect by comparing the estimation results under both load conditions for ferritic single-phase materials fabricated within the compositional range of hypoeutectoid steel. As a result, it is now possible to estimate the stress-strain relationship using indentation tests from microregions, approaching the scale of single crystal grains, for materials within the compositional range of hypoeutectoid steel.

The effect of the manganese content of 7% nickel-added steel on cryogenic toughness was investigated. When Charpy absorbed energy was investigated in the steels with wide range manganese content from 0.05% to 2.16%, the absorbed energy at −196°C increased with a decrease of manganese content. The two steels with manganese contents of 0.2% and 0.8% were selected for use in a more detailed investigation regarding the dependence of toughness at −196°C on the intermediate heat treatment temperature, fracture behaviors and the retained austenite. Although the 0.2% manganese steel stably exhibited a high absorbed energy at −196°C at all intermediate heat treatment temperatures examined in this work, it was necessary to select an appropriate intermediate heat treatment temperature for the 0.8% manganese steel in order to achieve high absorbed energy at −196°C. The total amount of the retained austenite and the size and the nickel content locally segregated into an identical retained austenite were quantified by using XRD and SEM/EDS, and the characteristics of the retained austenite in the steels with low manganese alloy designs were investigated. The cleavage-type brittle fracture that appeared in some specimens was discussed from the viewpoint of the stability of retained austenite.

This paper presents microstructural evolution and quantitative evaluation of precipitates during long-term creep of KA-SUS304J1HTB steel. Thermal aging and creep tests were conducted on a virgin material at 600 ~ 700 °C, for up to 26000 h, and the microstructures in grip and gage sections of creep ruptured specimens were observed by scanning and transmission electron microscopy including chemical analysis techniques. The effects of temperature and time on the growth of the σ phase and the Cu phase were quantitatively evaluated. Mean particle size of the Cu phase in the grain was increased with aging time by the volume diffusion control theory, and the activation energy for the Cu phase growth was calculated. Mean particle size of the σ phase and the Cu phase in grips were comparable to those in gage section, indicating that stress has little effect on both parameters. On the other hand, the average of the maximum particle size in the observation area and area fraction of the σ phase were larger in the gage section than those in the grips due to the effect of stress.

A typical hydrogen-related transgranular fracture, namely quasi-cleavage fracture, is usually accompanied by serrated markings on the resultant fracture surfaces in steels with body-centered cubic phases. The present paper investigated the microscopic three-dimensional morphology and crystallographic feature of serrated markings in a 2Mn-0.1C steel mainly composed of ferrite microstructure. The serrated markings corresponded to the corners of the step-like morphologies which consisted of microscopic {011} facets whose longitudinal directions were almost parallel to <011> or <211> direction. In addition, the microscopic {011} quasi-cleavage facets had the largest inclination angle from tensile axis among six crystallographically equivalent {011} planes, suggesting that resolved normal stress imposed on the {011} plane is an impor-tant factor for the hydrogen-related quasi-cleavage fracture. We propose that not only the slip deformation enhanced by hydrogen but also the coalescence of vacancies/voids induced by hydrogen-enhanced plastic deformation should be considered for understanding the mechanism of the hydrogen-related quasi-cleavage fracture along the {011} planes.