bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study of Dynamic Strain for Gear Tooth using Fiber Bragg Gratings and Piezoelectric Strain Sensors
Authors: Qu Yongzhi , Hong Liu , Jiang Xixin , He Miao , He David , Tan Yuegang , Zhou Zude
Published: March 2024

It has always been a critical task to understand gear dynamics for gear design and condition monitoring. Many gear models have been proposed to simulate gear meshing dynamics. However, most of the theoretical models arebased on simplified gear structure and may contain approximation errors. Direct measuring of gear strain is important to gear design validation, load analysis, reliability assessment, gear condition monitoring, etc. Most of theexisting studies of tooth strain measurements are performed under static load condition. In this paper, we investigate new measuring techniques of using fiber Bragg grating (FBG) sensor and piezoelectric strain for gear dynamicstrain measurement. We conduct gear dynamic strain measurement under both low speed and normal speed condition on an industrial gearbox with relatively small module gears. Multi-combinations of speed and load conditions of the gearbox are tested and the results are discussed and analyzed. We analyze multiple factors that affect the tooth root stress, including speed, load, extended tooth meshing, etc. It is found that under low operation speed range, the tooth root strain is mainly determined by the torque, while in the mediate to high speed range, the tooth root strain is jointly affected by speed and torque. Extended tooth contact is shown in the measurement results with strong evidence. It conforms with earlier founding that the transmission error and dynamic load factor are overestimated while the operation smoothness are underestimated for spur gear under heavy load. The measured stains are also compared with numerical simulation.
Analysis of Correlationship between Partial Discharge and Ozone Emission in High Voltage Motor Stator Windings as the Index of the Insulation Diagnosis
Authors: Lee Soo-Hoh , Kong Tae-Sik , Kim Hee-Dong
Published: March 2024

In this study, it turned out that the magnitude of Partial Discharges(PD) and the emission of Ozone(O3) were in a strong positive relation by performing insulation diagnostic tests on artificially defect high voltage motor statorwindings. In this sense, the O3 measurements can be a powerful index of the insulation deterioration during normal operation especially in case of surface PD activity.
Effect of Phase angle of Acceleration on Fatigue life in Frequency Domain of Vibration-Based Energy Harvester for Railway vehicle
Authors: Jin Ji-Won , Kang Ki-Weon
Published: March 2024

This study aims to perform fatigue life prediction of vibration-based energy harvester (VEH) considering resonance characteristics. First, we investigated the vibration environment of a structure on which an energy harvester may be installed and determined the level and frequency range of the power spectral density (PSD) exerted on the energy harvester. On the one hand, this research considered random vibration load, because VEH was operated by resonance phenomena. So, to consider random load, life prediction was performed by durability test machine and system. And in order to consider dynamic effect by natural frequency, vibration fatigue analysis was performed in frequency domain. Also, we were performed durability test and vibration fatigue under random load, which is composed of the PSD. As results, accuracy of life prediction procedure for VEH by vibration fatigue analysis was verified.
A study on decision making for replacement on old hydroelectric facilities based on RBM
Authors: Park Pyeong Kang , Kim Jong Sung
Published: March 2024

Hydroelectric power plants are operated with various types of hydroelectric power plants. The aging of these facilities is increasing the importance of stabilizing the facilities for stable power generation, and the demand for the reliability of such facilities is continuously increasing. In this study, the evaluation items of hydropower generation facilities such as water turbines, generators, control facilities, auxiliary facilities, transformers, transmission facilities, etc. were developed and the technology for evaluating the hydroelectric power plant technology was developed and the RBM technique And to make optimal decision making of alternate hydropower facilities.
A Practical Guide for the Characterization of Lithium-Ion Battery Internal Impedances in PHM Algorithms
Authors: Pérez Aramis , Benavides Matías , Rozas Heraldo , Seria Sebastián , Orchard Marcos
Published: March 2024

This article aims at describing the most important aspects to be considered when using the concept of battery internal impedances in algorithms that focus on characterizing the State-of-Health (SOH) degradation of lithium-ion (Li-ion) batteries. The first part provides a brief literature review that will help the reader to interpret the outcome of typical Li-ion discharge and/or degradation tests. The second part of the paper shows preliminary results for accelerated degradation experiments performed on a Li-ion cell under controlled conditions. Results show changes on electrochemical impedance spectroscopy test that can be linked to battery degradation. This knowledge may be of great value when implementing algorithms aimed at predicting the battery End-of-Life (EoL) in terms of temperature, voltage, and discharge current measurements.
Hamiltonian Monte Carlo Sampling for Bayesian Hierarchical Regression in Prognostics
Authors: Astfalck Lachlan , Hodkiewicz Melinda
Published: March 2024

Advances in computational speed have enabled the development of many Bayesian probabilistic models due to Markov-Chain-Monte-Carlo (MCMC) posterior sampling methods. These models includes Bayesian hierarchical regression methods, which use group level information to inform individual asset predictions. Hierarchical models are increasingly used for prognostics as they recognise that the parameter estimates for an individual asset may be rationally influenced by data from other similar assets. Larger and high dimensional datasets require more efficient sampling methods for calculations, than traditional MCMC techniques. Hamiltonian Monte Carlo (HMC) has been used across many fields to address high dimensional, sparse, or non-conjugate data. Due to the need to find the posterior derivative and the flexibility in the tuning parameters, HMC is often difficult to hand code. We investigate a probabilistic programming language, Stan, which allows the implementation of HMC sampling, with particular focus on Bayesian hierarchical models in prognostics. The benefits and limitations for HMC using Stan are explored and compared to the widely used Gibbs Sampler and Metropolis-Hastings (MH) algorithm. Results are demonstrated using three case studies on lithiumion batteries. Stan reduced coding complexity and sampled from posterior distributions more efficiently than parameters sampled with the Metropolis-Hastings algorithm. HMC sampling became less efficient with increasing data-size and hierarchical complexity, due to high curvature in the posterior distribution. Stan was shown to be a robust language which allows for easier inference to be made in the Bayesian paradigm.
Determining an acceleration factor for a metering pump used in a polyurethane injection machine
Authors: Lee Gi-Chun , Choi Byung-Oh , Choi Jong-Sik , Song Tae-Jin , Suh Chae-Young
Published: March 2024

A metering pump for a polyurethane injection machine is used to mix urethane with isocyanate (a plasticizer) and polyol (the raw material of polyurethane). The metering pump has typically used a piston-type hydraulic pump,which is a high-pressure mixed type; the materials are mixed with a constant flow by the mixing head device, which supplies the fluid flow through the pipelines. In terms of supplying the flow to the devices, the role of the metering pump is important in supplying a constant flow. This study focused on determining the acceleration factors (AF) via the accelerated life test method, as a life test under normal operating conditions takes more than five years to carry out. This research selected the stress factor that accelerated the main failure modes of the polyurethane injection metering pump, and the adopted acceleration model was the inverse power law. After selecting the acceleration factor and the model, the acceleration test was performed with an acceleration pressure of 21 MPa, as the operating pressure of the metering pump under the surveyed field operation conditions was 15 MPa.
A Bayesian approach to reliability prediction for one-shot devices
Authors: Lee Chinuk , Mun Byeongmin , Lee Junseop , Kim Zaeill , Ryu Byungtae , Bae Sukjoo
Published: March 2024

Projectile such as rocket and missiles is one of most important object for military and space industry. In order to measure its reliability accurately, general method which uses binomial distribution often require more than 3,000 sample to evaluate the reliability which can be problematic for further research and development. There have been many researches and studies to predict reliability with small sample size. Many studies suggest Bayesian approach with precise prior distribution as effective method to measure reliability of one shot device. In this research, we suggest application of proportional hazard model with Bayesian approach to estimate reliability of one shot device withsmall sample size.
Thermal and mechanical degradation of recycled poly-lactic acid filaments for use in 3D printers
Authors: Lee Dongoh , Zhao Xing Guan , Hwang Kyung-Jun , Cha Cheolung , Yoon Bumjin , Kim Namsu
Published: March 2024

Recycling of filaments used in 3-D printing system is beneficial to both the environment and and its manucactures by reducing manufacturing costs. This study investigates how multiple-recycled poly-lactic acid (PLA) filamentsaffects mechanical properties of fabricated objects.. Mechanical strengths of the printed PLA, as well as the adhesion strengths between 3-D-printed beads, were evaluated by tensile tests of horizontally and vertically fabricated specimens. The mechanical strength of the printed PLA as well as the adhesion strength between 3-Dprinted beads were determined through tensile testing of horizontally and vertically fabricated specimens. Subsequent gel permeation chromatography revealed that recycling reduced the molecular weight of the polymer, leading to a loss of mechanical strength in the 3D-printed component. In addition, images of cutting plane using scanning electron microscopy showed that the fabricated bead itself was broken in the case of the horizontally fabricated specimen, while in the case of the vertically fabricated one, the adhered between the beads was found to be broken. This indicates that the mechanical strength of inplane and out-of-plane direction should be improved by increasing mechanical strength of bead, itself, as well as the adhesion strength between beads.
A PHM Testbed for Fault Diagnosis of the Machine Tools
Authors: Jung Kyusung , Park Hyungjun , Kim Seokgoo , An Dawn , Choi Joo-Ho
Published: March 2024

In manufacturing, a machine tool needs to maintain in good condition to prevent degradation in accuracy and disruption in production. All machine tools degrade as it operates, but it is difficult to discern degradation before visual identification, especially detecting degradation in real time. As failure of main elements in the machine result in the significant loss in cost and time, manufacturers need automated and efficient method to diagnose and predict the condition of its elements while in its operation. This paper addresses the Prognostics and Health Management (PHM) architecture for the machine tool, in which the functional model is created from the target system, critical failure modes are identified, sensor units are design to measure failure cause, symptom and the effect on the quality. The proper sensors, features and PHM algorithms are suggested for each of the failure modes as well. To demonstrate and validate this approach, a testbed is designed and operated for machine tools equipment that can implement PHM technique by detecting the faults of critical components, monitoring their degradation and predicting the remaining useful life. After the implementation, cost benefit analysis of the PHM application is conducted. Final goal is to apply and validate the system in the real field.
Crack Detection on Pressed Panel Products using Image Processing Techniques with Camera System
Authors: Moon Hoyeon , Jung Hweekwon , Lee Changwon , Park Gyuhae
Published: March 2024

The detection of cracks on panel products is a vital step for ensuring the quality of panel products. General crack detection technique has been performed by human inspectors who are good at detecting crack, which is spend many times and much money. Therefore, it is necessary to detect efficiently crack on panel products by machine vision system during the press forming process. In this study, we performed an automated crack detection using two image processing techniques with camera system. The first technique is evaluating the panel edge lines which are extracted from a percolated object panel image. This technique does not require a reference image for crackdetection. Another technique is based on the comparison between a reference and a test image using the local amplitude mapping on the edge line image. The reference image of panel product is automatically acquired by camera system using image difference and time interval technique. As a result, cracks are efficiently detected using two crack detection techniques based on image processing. For demonstrating the proposed techniques, experiments were performed in the laboratory and the actual manufacturing lines. Experimental results show that the proposed techniques could effectively improve the crack detection rate with improved speed.
Study on impact of UV curing process of digital light processing 3-D printer on the mechanical properties and dimensional accuracies
Authors: Lee Younghun , Zhao XingGuan , Lee Dongoh , Kim Namsu
Published: March 2024

In the last decade, there has been an exponential increase of the scientific interest for smart additive manufacturing (AM) technology. Among the different AM techniques, the most commonly applied processes are digital light processing (DLP). DLP is a laser-based process that works with photopolymer resins, which react with the ultraviolet (UV) and is cured to form a solid in a very precise way to produce parts with high dimensional accuracy. However, because of the scattering effect when UV light passes through the transparent vat and different polymerization characteristics and curing depth of photopolymer resins, there are lots of parameters of DLP printers need to be optimized. Among these, exposure time affects the quality of the 3D printed specimen. If it is not optimized, it brings about problems such as poor mechanical properties and poor dimensional accuracy. Therefore, this study examinedoptimal exposure time. With a same specimen and layer thickness, the photopolymer resin was exposed to the UV light in different times to evaluate the influence of it. The UV mercury lamp, 240 W and wavelength of 385-650nm is used. To investigate the effect of exposure time on the mechanical strength, the tensile strength and young’s modulus were experimentally determined using universal material test machine.
A Study on Smart Roll Forming Based on Real Time Process Data
Authors: SON Jae-Hwan , CHO Dong-Hyun , LEE Seung-Yong , KIM Chul-Hong
Published: March 2024

Roll forming refers to the production of long plate molded products such as panels, pipes, tubes, channels, and frames by continuously causing bending deformation to thin plates using rotating rolls. Since the roll forming method has advantages in terms of mass production because of its excellent productivity, the size of the roll forming industry has been continuously increasing and the roll forming method is being used in diverse industrial fields as a very important processing method. Since the roll forming method mainly depends on the continuous bending deformation of the plate materials, the time and cost used for heterogeneous materials developed in the process are relatively large when seen from the viewpoint of plastic working because many processes are continuously implemented. Existing studies on the roll forming manufacturing as such involve the losses of large amounts of time and materials when raw materials or product types are changed, can hardly secure the uniformity of formed shapes and the quality of sizes, and cannot detect all defects occurring in mass production and the dimension. Although dedicated lines with fixed settings for individual products may be considered for the foregoing reasons, the formation of individual dedicated roll forming lines for individual products faces great difficulties due to excessive manufacturing costs. Therefore, in this study, a real - time process data based smart roll forming that can be applied to multiple products was studied. As a result of such a study, a roll forming system was implemented that remembers and automatically sets changes in fine adjusted values of the supplied quantities of individual heterogeneous materials so that the equipment setting changing time for heterogeneous material replacements or changes in the products being produced can be shortened and secures the uniformity of products so that more competitive precise slide rail products can be mass-produced with improvements in the quality, price, and productivity of products. In addition, smart roll forming process designs were numerically analyzed and the results were applied so that targeted shapes can be approached faster, the reactions in reduction processes by step can be evenly distributed to reduce the intensity fatigue of each process roller, the productivity can be improved, and, in particular, fine cracks or damage to rollers can be prevented thereby removing the fundamental cause of theoccurrence of mass defects.
Structural Health Monitoring of CFRP Structures Using Electromechanical Behavior
Authors: Roh Hyung Doh , Park Young-Bin
Published: March 2024

Whereas the number and the fields of carbon fiber reinforced plastics (CFRPs) are vastly increasing, studies about in-situ real-times self-sensing are limited. Thus, our research group investigated the CFRP self-sensing capability using the electromechanical behaviors of CFRPs. Both elastic region and failure of CFRPs can be monitored by electrical resistance change ratio. Therefore, structural health monitoring (SHM) and prognostic health management (PHM) are feasible for both elastic deformation and delamination.
Wavelet-based Wavenumber Filtering for Damage Detection with a Scanning Laser Sensing System
Authors: Kim DuHwan , Todd Michael D. , Park Gyuhae
Published: March 2024

This paper describes the use of wavelet-based wavenumber filtering for damage detection with a signal-frequency standing wave excitation on thin plate structures. Using a single, fixed frequency excitation from a mounted piezoelectric transducer, the full standing wave-field could be obtained using a Laser Doppler Vibrometer (LDV) with a mirror-tilting device. After scanning, a wavelet-based wavenumber filtering is performed to determine dominant wavenumber components, which could be used for indicative of structural damage. Mapping processes based on the wavelet-based wavenumber filtering is then carried out for damaged area visualization. To demonstrate the proposed techniques, several experiments are performed on thin walled structures with several different types of damage (corrosion, debonding). The results demonstrate that the techniques are very effective in localizing damage with the potential for the improved speed and the performance for damage detection.
Development of Compressor Blade Prognostics and Health Management for Large Gas Turbine Engine
Authors: Park Luke , Hwang Donghyeon , Nam Samsik
Published: March 2024

DOOSAN has been developed large gas turbine since 2014 as a national project in Korea. Recent researches showed that one of major risk item in gas turbine development is compressor rotor blade failure. There are several events of compressor rotor blade failure which have occurred over the last few years, in some cases causing catastrophic damage to the entire compressor. In response to these issues, DOOSAN started to develop compressor monitoring system to prevent failures and diagnose blades to assess the structural integrity of each blades. This paper presents the ideas and plans how DOOSAN will develop the system with latest sensors. Additionally, validation methods will be presented using sub-scaled test rig in 2018 and real scale engine test in 2019, respectively.
Towards a Cloud-based Machine Learning for Health Monitoring and Fault Diagnosis
Authors: Khan Samir , Yairi Takehisa , Kiran Mariam
Published: March 2024

Large complex engineered systems collect large amounts of varied data sets, making it often difficult to process and analyze these for diagnosing, isolating, and predicting faults during operation. To recognize symptoms with standard testing tools, infer potential faults and eventually diagnose causes needs constant maintenance support. This problem is particularly faced in the aerospace industry, where it is essential to analyze and maintain assets to prevent potential failures or loss both technological and human. Recent usage of Cloud computing provides infinite computing resources to quickly process and troubleshoot, reducing ‘time-to-fix’ problems. Exploiting artificial intelligence (AI) algorithms, with Cloud resources, can help build an integrated fault diagnostic platform to provide resilient and scalable resources for data acquisition, processing and decision making. This paper presents an industrial perspective and problems when using machine learning methods for fault diagnosis, particularly using Cloud resources in the aerospace industry. Special attention is paid to the benefits; with potential future research on technical diagnosis being enumerated.
Research on Fault Detection Method for Tire Dynamic Balance Measuring System Based on Correlation Analysis
Authors: Yueyue Liu , Xiaoyang Li , Deng Liu , Wenbin Chen
Published: March 2024

Application of correlation analysis method was studied in fault detection of dynamic balance measuring system. The test data reproducibility in dynamic balance measuring system is a key index of the system’s reliability, there aremany influencing factors and all of them are with relevance, which make it difficult to troubleshoot the factors that affect the reproducibility of test data in practical project, this has been restricting the development of tire dynamicbalance measuring systems. The method of correlation analysis was used to the fault detection for tire dynamic balance measuring system by the first time. The sensitive factors of test data repeatability in dynamic balance measuring system was obtained through the correlation analysis of the measured data in the measuring system, and the measuring system was optimized according to the analysis results, then a series of tests were arranged in the optimized system to verify the correctness of the correlation analysis, thus clarifying the important role of correlation analysis in fault detection.
Battery prognostics based on discharge voltage drop for energy storage applications
Authors: Kim Dongjin , Lee Jaewook , Kim Seok Goo , Choi Jooho , Song Hwa Seob , Park Sang Hui
Published: March 2024

This study proposes an approach that can predict the end of Li-ion battery life using the discharge voltage drop curve during its use in the energy storage system (ESS). The approach is developed based on the findings that the voltage drop in Li-ion batteries increases as the battery undergoes cycles, and it can be related with the residual capacity. The key idea is to insert the additional cycle of full charging and discharge with constant c-rate during the usage of the ESS. In this cycle, the relation between the voltage drop and capacity is established off-line via regression technique. Then this is applied to estimate the SOH and RUL on-line during the battery cycles. Particle filter (PF) algorithm is applied to this end, in which the degradation and regression models are taken as the state and measurement models respectively, and the capacity is estimated in the form of samples. The obtained samples are then used to predict its behavior in the future, from which the RUL distribution is determined. Conclusion of the study is that the voltage drop in Li-ion batteries can be a good indicator of the battery health and PF is a useful toolthat can predict the RUL accurately even when the chargedischarge conditions change in the middle of the usage cycles.
A Feasibility Study on CNT- and Graphene-aided Structural Health Monitoring of Wind Turbine Blades
Authors: Lee In Yong , Park Young Bin
Published: March 2024

This paper presents a study on incorporation of hybridized MWCNTS and rGO in fiber-reinforced plastics for structural health monitoring in real time. Carbon nanoparticle that has certain MWCNT to rGO ratio was dispersed in a solvent were uniformly spray-coated on the surfaces of glass fiber fabrics, which were then layed-up and impregnated with an unsaturated polyester resin using vacuum-assisted resin transfer molding(VARTM) to form composite samples. Prior to VARTM process, electrodes were embedded on the sprayed coated glass fiber ply for electrical resistance change monitoring. The composite sample was subjected to cantilever bending and twist test, during which the changes in resistances between various electrode pairs were measured and recorded. Experimental results showed the dependence of resistance change on the deformation. In particular, this research covers hybridized MWCNTS and rGO electrical network on wind turbine blade. Cantilever bending and twist test were demonstrated by simulation program and this paper gives proposal about future application on huge composite part with MWCNT and rGO.
Numerical Analysis of heat dissipation in photovoltaic module through highly thermal conducting backsheet
Authors: Kim Taemin , Kim Namsu
Published: March 2024

The performance of photovoltaic module is largely dependent on the temperature of photovoltaic cells. Hence, the heat management for PV module is crucial to increase the performance of cell as well as to predict the generated energy from PV module. In this study, the temperature of PV module was calculated based on numerical simulation and the mechanism of heat dissipation in the module was investigated. Based on numerical simulation results, efficient structure of PV module and appropriate range of thermal conductivity for efficient heat dissipation can be suggested.
Evaluating Strategies to Mitigate Jamming in Electromechanical Actuators for Safety Critical Applications
Authors: Hussain Yameen M. , Burrow Stephen , Henson Leigh , Keogh Patrick
Published: March 2024

In this paper various techniques to mitigate jamming in Electromechanical Actuators (EMA) for safety critical applications in aerospace are evaluated. This paper highlights and assesses what has already been achieved and thechallenges still to be addressed. Through Hierarchical Process Modelling (HPM), it was identified that Prognostics and Health Monitoring (PHM) and achieving fault tolerant designs in EMAs could be considered as means to mitigate jamming. The evaluation of past research revealed that achieving a fault tolerant EMA system through a reliable and robust anti-jamming system is currently at an early development stage for implementation within safety critical systems due to the increased design complexity (the antijamming system may even require PHM functionality itself). It was concluded that a hybrid diagnostic approach to predict the onset of jamming would be the most optimal approach by using a combination of model based and data-driven techniques to capture any discrepancies between the predicted and observed behaviour to isolate and identify faults. Furthermore, in order to achieve a robust and reliable hybrid diagnostics functionality (to mitigate EMA ballscrew jamming), recommendations were made to improve modelling fidelity and test stand analysis methodology, these are discussed in more detail in this paper.
Development of Hybrid Measurement System for Railway Infrastructure by Utilizing IoT Technology
Authors: Choi Kyungwho , Kang Donghoon
Published: March 2024

Recently, advanced sensors like fiber optic sensors have been developed and replaced with conventional resistance type sensors due to their many advantages such as long-distance capability, EMI immunity, multiplexing easiness, and etc. However, it was hard to commercialize fiber optic sensors in railroad applications so far since their types are limited and are not cost effective to construct a measurement site. In order to overcome these problems, the authors developed a hybrid measurement system which integrates the commercial electrical sensors and optical sensors with IoT-based wireless communication technology in this study.
On Determination of the Non-periodic Preventive Maintenance Scheduling with the Failure Rate Threshold for Repairable System
Authors: Lee Juhyun , Park Jihyun , Ahn Suneung
Published: March 2024

Determination of a preventive maintenance scheduling is regarded as a key part in manufacturing system to maintain the equipment in good condition. In practice, many preventive maintenance policies is used in manufacturing system to reduce the unexpected failures and increase sustainability of system. In this paper, the failure rate of system is used as a condition variable and a decision variable, and preventive maintenance policy is then developed for minimizing the expected maintenance cost rate. The imperfect preventive maintenance activities of the proposed models are modeled via the arithmetic reduction model which uses the age reduction factor or the hazard reduction factor. The results of the numerical example shows that the model based on age reduction can not only extend the system lifetime but also reduce the expected maintenance cost rate although the preventive maintenance cost is significantly higher than those of the model based on hazard reduction.
Thermal Fatigue Analysis and Evaluation of Wheel-Rail Contact under Braking Conditions
Authors: Lee Soyoung , Shao Hailong , Lee Dong-Hyung , Choi Ha-Young , Lee Jongsoo
Published: March 2024

Recently, reliability design considering the fatigue has been demanded for ensuring the driving safety for the high speed railway. In particular, the railway wheel and rail are subjected not only to mechanical load but also to highthermal load due to frictional heat generated when the railway wheel contacts with the brake shoe during tread braking. As repetitive thermal load accelerates damage to the wheel surface, it leads to shorten the replacement cycle and increase the maintenance cost. Therefore, we expect to achieve the economic efficiency by using the wheel over the life expectancy while maintaining the structural health. Initial braking velocity is one of the main factors affecting the behaviors of contact surface between the wheel and rail. Therefore, it is necessary to evaluate the effect of thermal stress according to it. In this study, through the thermalmechanical analysis considering both mechanical load and thermal load caused frictional heat under braking conditions, thermal stress subjected to the contact surface between the railway wheel and rail was calculated. Based on these results, the thermal fatigue analysis was carried out to evaluate the safety under fatigue and predict the fatigue life.
Functional Reliability Prediction of Pyrotechnic Separation Device using Response Surface Model
Authors: Kim Dong-seong , Jang Seung-gyo , Ryu Byung-Tae
Published: March 2024

Pyrotechnic separation device is used in military and aerospace application because of many benefits such as fast operating time, simple structure, and light weight. The reliability the pyrotechnic device is very important due to itsone-shot nature. Thus, reliability prediction of the device should be considered from the beginning stage of its design. This paper introduces an approach to predict functional reliability of pyrotechnic separation device. The overall procedure consists of the following steps: 1) design parameters affecting the pyrotechnic separation device are identified, 2) design of experiment is defined through the sensitivity analysis about parameters, 3) response surfacemodel is constructed using polynomial equation. 4) The functional reliability is calculated using Monte Carlo simulation by iterating response surface model.
Low Cost Wireless Vibration Monitoring using Thermoelectric Energy Harvester for Machinery Prognostic
Authors: Nishino Takuya , Nagata Junichi , Nakagawa Kanae , Tsukada Mineharu
Published: March 2024

This paper presents a microphone-modified low cost vibration sensor that can be operated by a self-battery system using a thermoelectric generator. The developed microphone-based vibration sensor with two batteries forthe efficient use of electric power from the thermoelectric element was integrated as a wireless sensor node. The sensor accuracy was calibrated in two operations. One was an experimental setup to evaluate the frequency dependence of the developed sensor by using waves of a specific vibration compared with piezoelectric accelerometers. The second operation was long term data acquisition in real field. We successfully demonstrated the wireless vibration sensing operation for a motor in real field. It was operated only their sensing and transmitted energy by itself using its surface temperature difference for two months. The raw vibration data was sensed and acquired for two months, and the feature values of the results of time series data were in good agreement with the referenced piezoelectric sensor data.
Prognostic method for tripping over when walking for controlling the robotic ankle prosthetics
Authors: Lee Y. , Hwang D.H.
Published: March 2024

Generally, the walking road includes many bumps. In order to wear a robotic ankle prosthesis and walk on a general walkway, it is necessary to control the robotic ankle prosthesis so that it can cope with tripping over when it iscaught by a bump. The purpose of this study was to analyze the kinetic behavior of the ankle and to determine the discrimination method of the case of tripping over by unevenness. The ankle is in bent toward plantar more thangeneral walking toe-off when it is caught by unevenness. and the thigh is bent toward body, the ankle is in dorsiflexion to prevent from tripping over. When tripping over, it can be discriminated according to the degree of the ankle angle and then the robot's ankle can be bent in dorsiflexion to prepare for the next movement of the body to prevent from tripping over.
Bending Wave Propagation Analysis Induced by Metal Ball Impacts on Reactor Pressure Boundary Structure
Authors: Moon Seong-In , Kang To , Lee Seong-Il , Seo Jung-Seok , Lee Jeong-Han , Han Soon-Woo , Park Jin-Ho
Published: March 2024

Recently, a model-based prognostic approach is becoming one of noticeable techniques to predict the fault behaviors of mechanical components in nuclear power plant. Lamb’s general solution for an arbitrary impact force function and Hertz impact theory have been used to identify the bending wave characteristics impacted by a metallic loose part in reactor pressure boundary components. However. these approaches can hardly provide an information on accurate acceleration response for identifying the impact source. In this study, the impact response characteristics such as maximum acceleration amplitude and primary frequency of the impact response signal by a simulated loose part (metal ball) are analyzed using finite element analysis (FEA) and the FEA-based model is verified by experimental results. It is expected that the developed FEA-based model can be utilized in model-based prognostics for localization and estimation of mass of loose part in nuclear power plants.
A Study on Acoustic Signal Processing Technique for Detecting Small Leak of Piping System
Authors: Yoon D.-B. , Moon S.-S. , Yang B.-S.
Published: March 2024

The objective of this work is to develop a signal processing technique for detecting small leak of piping system in a noisy environment. For this purpose, as algorithms for enhancing the leak detection capability, a small leak detection algorithm were developed by using time-spatial characteristics of the measured acoustic signal. The leak detection capability of the developed algorithm is verified by experiments and numerical simulations. It is expected that the developed small leak detection algorithm can be utilized for leak detection of piping system of a power plant.
Measurement of wavenumber of wall-thinned plate using spatial local wavenumber filtering
Authors: Kang To , Lee Jeong Han , Han Soon Woo , Park Jin Ho , Park Gyuhae , Jeon Jun Young
Published: March 2024

The surface of a shell-type structure can generate cracks or wall-thinning due to corrosion, etc. Those can eventually lead to the fracture of the structure, which can trigger enormous fatality and property loss. Thereby, a laser imaging technology on such structures as thin plate structureor piping whose thickness is relatively thin in comparison to the area, has been steadily studied for the past 10 years. The most typical among the laser imaging technology is the pulse laser imaging. By using the same, a new technology for inspecting and imaging a desired area within a relatively short period of time was developed, so as to scan various structures including the thin-plate structure and piping. However, this method builds image by measuring waves reflected from defects, and has a time delay of a few milliseconds at each scanning point. Moreover, complexityof the systems is so high due to additional components such as laser focusing parts. This paper proposes laser imaging method with increased scanning speed based on excitation and measurement of standing waves in structures. It is shown that defects in a structure can be visualized bygenerating standing waves with single frequency and scanning the waves at each point by the laser scanning system suggested in this work. To quantitatively evaluate thickness of a plate, wavenumber is calculated by acoustic wavenumber spectroscopy, and relationship between wavenumber and thickness of the plate is established by Rayleigh-Lamb frequency equation. The proposed technique is validated by wall-thinned plates that have constant wall loss and a linear thickness variation wall loss.
Development of degradation model of viscoelastic polymers during thermo-oxidative aging by Oberst beam testing
Authors: Kim Sun Yong , Lee Doo Ho
Published: March 2024

Depending upon the environmental conditions such as oxygen, ozone, sunlight, thermal, UV and radiation, the characteristic of viscoelastic polymer would be degraded. It is well known that oxidative degradation is generally considered to be the most serious problem for rubbers at high temperature. The prediction of their performance requires the knowledge of their dynamic properties as a function of frequency and temperature. In order to identify the characteristic of viscoelastic polymer during thermooxidative ageing, Oberst beam testing would be adopted. The aim of this research project is to identify the degradation characteristics of viscoelastic polymer by ageing at different properties and time period.
Numerical evaluation of ABS parts fabricated by fused deposition modeling and vapor smoothing
Authors: Zhang Sung-Uk
Published: March 2024

Fused deposition modeling (FDM) is one of the popular 3D printing technologies due to an inexpensive extrusion machine and multi-material printing. However, FDM could only use thermoplastics such as ABS and PLA and has a problem related to the post-processing. In this study, themechanical properties of ABS parts fabricated by FDM were measured. The ABS parts were divided into one with vapor smoothing process and the other without the vapor smoothing process which is one of the the post-processing methods. Using dynamic mechanical analysis (DMA) anddilatometer, temperature-dependent storage modulus and CTE for ABS specimens were observed. Based on the measured thermo-mechanical properties of ABS parts, finite element analysis was performed for an automotive bumper made of ABS. Moreover, response surface methodologywas applied to study the relationship among design parameters of thickness of the bumper, ambient temperature, and application of the vapor smoothing process. In result, a design guideline for a ABS product could be provided without time-consuming experiments.
Effects of the bonding length on the reflected spectra and strain measurement of the surface bonded fiber Bragg grating sensor
Authors: Kwon Hyunseok , Park Yurim , Shrestha Pratik , Kim Chun-Gon
Published: March 2024

Surface bonded fiber Bragg grating (FBG) sensors have the limitation that signal characteristics are affected by the bonding layer. Previously conducted studies with regard to this limitation used different optical fiber sensors and load types during the experiments, and didn’t consider the effects on the reflected spectra. Therefore, in this study, the effects of the bonding length on the reflected spectra and strain measurement of the surface bonded FBG sensor were experimentally investigated. From the experimentation results, sufficiently bonded FBG sensor showed stablereflected spectra and enough strain transfer rate. However, insufficiently bonded FBG sensor showed distorted reflected spectra with high multiple peak ratio due to internal strain gradients within the grating length of the FBG sensor. In addition, distorted reflected spectra made it difficult to calculate adequate peak and decreased the strain transfer rates. Therefore, it was found that effective bonding length need to be determined to get a stable reflected spectra and enough strain transfer rate from the surface bonded FBG sensors.
Continuous-wave Laser Thermography for Concrete Crack Evaluation under Moving Conditions
Authors: Jang Keun-Young , Hwang Soonkyu , Park Jiho , An Yun-Kyu
Published: March 2024

This paper presents a continuous-wave laser thermography (CLT) technique for concrete surface crack evaluation under moving conditions. The CLT technique is able to visualize and quantify surface cracks on moving concrete structures by generating a continuous-wave laser source and capturing infrared images at a fixed spatial point. Although the CLT system has spatially limited field of view, it can inspect the entire region of interest (ROI) of the moving target structure. To precisely quantify surface cracks, the data acquired from the entire ROI are integrated and subsequently processed by developing an instantaneous crack evaluation algorithm. In this study, concrete specimens with various macro- andmicro-cracks are specially prepared and used to validate the proposed CLT technique. The test results reveal that various cracks are successfully visualized and quantified within 3% error ratio.
Computer Vision-based Displacement Measurement Method With Arbitrarily Positioned Camera
Authors: Lee Junhwa , Cho Soojin , Sim Sung-Han
Published: March 2024

Displacement is broadly used in structural health monitoring as a meaningful indicator of structural status. Measuring structural displacement using conventional devices such as the linear variable differential transformer is challenging due to practical issues such as equipment inaccessibility, insufficient measurement accuracy, or expensive system cost. Recently, computer vision-based displacement measurement methods have been developed to build high field applicable measurement system. However, the existing computer vision-based displacement measurementtechniques still have practical issues such as absence of camera installation point, marker attachment, or lightinduced error. This paper presents a computer vision-based displacement measurement system focusing on solving camera positioning issue. The proposed method adopts homography transform to allow cameras to be positioned at arbitrary point. A laboratory scale experiment was conducted to verify accurate displacement measurement of the proposed method with the arbitrarily positioned camera.
Assessment of Concrete Efflorescence based on Hyper-spectral Imaging
Authors: Kim Byunghyun , Kim Dae-Myung , Cho Soojin
Published: March 2024

Efflorescence is a phenomenon mostly made by carbonation process of concrete structures. It is one of the internal damages seriously considered in evaluating the durability of concrete bridges. In Korea, the guideline for the bridge safety inspection requests to assess crack, efflorescence, spalling and reinforcement exposure in prior for the slabs and girders of concrete bridges. Currently, the assessment is performed based on the visual inspection of expertized engineers, which may result in subjective inspection result. In this study, a novel method to assess concrete efflorescence is proposed based on hyper-spectral imaging (HSI) device. The HSI acquires the light intensity for a number of continuous spectral bands of light for each pixel in an image, which makes the HSI provides more detailed information than a normal color camera that collects intensity for only three bands corresponding to the colors, RGB (red, green, and blue). A stepwise assessment algorithm is developed based on the spectral features developed to decompose efflorescence area from the inspected concrete area. The algorithm is verified in the laboratory testing using concrete specimens with the efflorescence, which shows high accuracy of the proposed HSI-based assessment.
Monitoring of the Hardening Process of Ultra High Performance Concrete (UHPC) based on Guided Wave Propagation
Authors: Lee Changgil , Park Jooyoung , Tola Kassahun D. , Park Seunghee
Published: March 2024

In this study, the hardening process of ultra high performance concrete (UHPC) was monitored non-destructively using a single embedded sensor system. The propagating characteristics of guided waves obtained from the sensing system were analyzed to estimate the setting time and thestrength development of UHPC. Since the boundary conditions of the embedded sensor system continuously change during the hardening process of concrete materials, the hardening process can be monitored based on the measured characteristics of the propagating waves. To understand the variations in wave propagation, the modes for the guided waves were decomposed. The strength development of UHPC, with and without short-fiber reinforcement, was estimated using the variation of patterns of the decomposed wave modes. Based on the proposed methodology, which measures the propagation and variation of the guided waves, it is possible to estimate the time of phase transition and the strength development of UHPC.