Health Monitoring Research Research Articles

Industrial Age non-destructive evaluation to Information Age structural health monitoring

This article was originally presented as a keynote address at the Ninth International Workshop on Structural Health Monitoring with the intent of provoking discussions relating to the transformation of aircraft maintenance practices by exploiting opportunities and benefits offered by Information Age technology and techniques. The US Air Force currently manages its aircraft using a schedule-based maintenance philosophy. This schedule-based approach works well for ensuring aircraft integrity; however, it is very costly, labor-intensive, and reduces aircraft availability. Structural health monitoring systems have the potential to analyze near-real-time and historical weapon systems data to provide a predictive maintenance capability. However, much aerospace structural health monitoring research has focused on in situ structural inspection techniques instead of structural monitoring. Structural inspections typically entail examining key locations of an airframe for material degradation or flaws. These examinations usually occur at predefined time intervals. As such, each inspection is considered an independent evaluation. Conversely, structural monitoring involves continuous condition surveillance of an airframe over an extended period of time. Structural monitoring uses past conditions and expected future conditions for producing a comprehensive understanding of the current health state. A new architecture, Cognitive Architecture for State Exploitation, is introduced as a monitoring technique that combines diagnostic or state (i.e. health) assessments, prognostic assessments, and mission objectives into a common framework to enable goal-based decision making. Results from a laboratory experiment are utilized to demonstrate the application of Cognitive Architecture for State Exploitation and to illustrate the potential to improve effectiveness and efficiency metrics compared to those of the current US Air Force maintenance procedures.

Damage detection and conductivity evolution in carbon nanofiber epoxy via electrical impedance tomography

Utilizing electrically conductive nanocomposites for integrated self-sensing and health monitoring is a promising area of structural health monitoring (SHM) research wherein local changes in conductivity coincide with damage. In this research we conduct proof of concept investigations using electrical impedance tomography (EIT) for damage detection by identifying conductivity changes and by imaging conductivity evolution in a carbon nanofiber (CNF) filled epoxy composite. CNF/epoxy is examined because fibrous composites can be manufactured with a CNF/epoxy matrix thereby enabling the entire matrix to become self-sensing. We also study the mechanisms of conductivity evolution in CNF/epoxy through electrical impedance spectroscopy (EIS) testing. The results of these tests indicate that thermal expansion is responsible for conductivity evolution in a CNF/epoxy composite.

On-Line Health Monitoring Research on T-Joint of Main Steam Piping

The main challenge of long-time creep monitoring on site is a reliable sensor. In this paper, a sensing device is developed specifically for high temperature creep monitoring. And it is applied to on-line monitor the strain of material on T-joint of main steam piping. Its reliability is verified theoretically using the finite element method and experimentally by high temperature on site test. The creep damage of the T joint is evaluated basing on the creep rate sensed by the sensing device. And the residual life is predicted for the piping system using the Monkman-Grant equation. This system is useful for safety assessment procedures in thermal power plant, nuclear power plant and petrochemical industries.

Three-dimensional laser scanning vibrometry as a visualisation tool for structural health monitoring research

Three-dimensional laser scanning vibrometry as a visualisation tool for structural health monitoring research

Three-Dimensional Laser Scanning Vibrometry as a Visualisation Tool for Structural Health Monitoring Research

The application of three-dimensional scanning laser vibrometry for visualising stress wave propagation in a specimen with a non-surface penetrating defect is presented in this paper. The aim of this paper is to demonstrate the use of this measurement technique to achieve a good insight of the propagation of the stress wave over a given region on a test specimen. An investigation into the interaction of the various wave modes with the defect in the structure can be enhanced with this knowledge. The ability to acquire the time series at an array of measurement points in a given region on the structure provide for an excellent means for visualising the propagation of the incident stress and how they interact with the defect present. In addition to the visualisation aspect, the data acquired can also be transformed to assess the modal content of the various wave modes present within the structure. For the purpose of this paper, a flat aluminium test plate with a non-surface penetrating defect will be used. The application of this form of non-contact measurement technique for the stress wave visualisation work will be illustrated. It will be shown that this measurement technique can be used to establish the modal content and the time-development of the incident and the scattered wave modes in the test specimen.

Dynamic Model for Hydro-Turbine Generator Units Based on a Database Method for Guide Bearings

A suitable dynamic model of rotor system is of great significance not only for supplying knowledge of the fault mechanism, but also for assisting in machine health monitoring research. Many techniques have been developed for properly modeling the radial vibration of large hydro-turbine generator units. However, an applicable dynamic model has not yet been reported in literature due to the complexity of the boundary conditions and exciting forces. In this paper, a finite element (FE) rotor dynamic model of radial vibration taking account of operating conditions is proposed. A brief and practical database method is employed to model the guide bearing. Taking advantage of the method, rotating speed and bearing clearance can be considered in the model. A novel algorithm, which can take account of both transient and steady-state analysis, is proposed to solve the model. Dynamic response for rotor model of 125 MW hydro-turbine generator units in Gezhouba Power Station is simulated. Field data from Optimal Maintenance Information System for Hydro power plants (HOMIS) are analyzed compared with the simulation. Results illustrate the application value of the model in providing knowledge of the fault mechanism and in failure diagnosis.

Dynamic Model for Hydro-Turbine Generator Units Based on a Database Method for Guide Bearings

A suitable dynamic model of rotor system is of great significance not only for supplying knowledge of the fault mechanism, but also for assisting in machine health monitoring research. Many techniques have been developed for properly modeling the radial vibration of large hydro-turbine generator units. However, an applicable dynamic model has not yet been reported in literature due to the complexity of the boundary conditions and exciting forces. In this paper, a finite element (FE) rotor dynamic model of radial vibration taking account of operating conditions is proposed. A brief and practical database method is employed to model the guide bearing. Taking advantage of the method, rotating speed and bearing clearance can be considered in the model. A novel algorithm, which can take account of both transient and steady-state analysis, is proposed to solve the model. Dynamic response for rotor model of 125 MW hydro-turbine generator units in Gezhouba Power Station is simulated. Field data from Optimal Maintenance Information System for Hydro power plants (HOMIS) are analyzed compared with the simulation. Results illustrate the application value of the model in providing knowledge of the fault mechanism and in failure diagnosis.

Using Personal Cell Phones for Ecological Momentary Assessment

Ecological Momentary Assessment (EMA) is a way of collecting data in people’s natural environments in real time and has become very popular in social and health sciences. The emergence of personal digital assistants has led to more complex and sophisticated EMA protocols but has also highlighted some important drawbacks. Modern cell phones combine the functionalities of advanced communication systems with those of a handheld computer and offer various additional features to capture and record sound, pictures, locations, and movements. Moreover, most people own a cell phone, are familiar with the different functions, and always carry it with them. This paper describes ways in which cell phones have been used for data collection purposes in the field of social sciences. This includes automated data capture techniques, for example, geolocation for the study of mobility patterns and the use of external sensors for remote health-monitoring research. The paper also describes cell phones as efficient and user-friendly tools for prompt manual data collection, that is, by asking participants to produce or to provide data. This can either be done by means of dedicated applications or by simply using the web browser. We conclude that cell phones offer a variety of advantages and have a great deal of potential for innovative research designs, suggesting they will be among the standard data collection devices for EMA in the coming years.

Guest Editorial - Selected Papers from the 2012 IEEE International Solid-State Circuits Conference (ISSCC)

THE IEEE International Solid-State Circuits Conference (ISSCC) is the flagship conference of the IEEE Solid-State Circuits Society and the foremost global forum for presenting advances in solid-state circuits and systems- on-a-chip. In 2010 and 2011, the IEEE Transactions on Biomedical Circuits and Systems highlighted select papers from the ISSCC conference on topics related to biological and healthcare applications, which were well received. This special issue once again features six select papers from the ISSCC 2012. This set of papers offers a sample of the rapidly expanding developments in solid-state circuits for health monitoring, therapeutics, diagnostics, and medical research applications. The selection of these papers, whose final decision was based on peer review, was coordinated with the Editor-in-Chief of the IEEE JOURNAL OF SOLID-STATE CIRCUITS, Prof. Un-Ku Moon, to avoid overlap with its ISSCC 2012 special issue, which will include biomedical papers as well. We also acknowledge the ISSCC 2012 General Chair, Prof. Anantha Chandrakasan and the Editor-in-Chief of the IEEE Transactions on Biomedical Circuits and Systems, Prof. Gert Cauwenberghs, for their support.

Modal identification of Canton Tower under uncertain environmental conditions

The instrumented Canton Tower is a 610 m high-rise structure, which has been considered as a benchmark problem for structural health monitoring (SHM) research. In this paper, an improved automatic modal identification method is presented based on a natural excitation technique in conjunction with the eigensystem realization algorithm (NExT/ERA). In the proposed modal identification method, damping ratio, consistent mode indicator from observability matrices (CMI_O) and modal amplitude coherence (MAC) are used as criteria to distinguish the physically true modes from spurious modes. Enhanced frequency domain decomposition (EFDD), the data-driven stochastic subspace identification method (SSI-DATA) and the proposed method are respectively applied to extract the modal parameters of the Canton Tower under different environmental conditions. Results of modal parameter identification based on output-only measurements are presented and discussed. User-selected parameters used in those methods are suggested and discussed. Furthermore, the effect of environmental conditions on the dynamic characteristics of Canton tower is investigated.

Some Recent Developments in Structural Health Monitoring

This paper is concerned with reporting some recent developments in Structural Health Monitoring (SHM) research conducted within the Dynamics Research Group at the University of Sheffield. The particular developments discussed are concerned with arguably the two main problems facing data-based approaches to SHM, namely: how to obtain data from damage states of a structure for supervised learning and how to remove environmental and operational effects from data when unsupervised learning (novelty detection) is indicated.

Ship Structural Health Monitoring Research at the Office of Naval Research

The Office of Naval Research (ONR) has developed a program to advance the science and technology of ship structures, called the ONR Ship Structural Reliability Program. The program has the strategic long-term vision of the development of technologies suitable for cradle-to-grave lifecycle performance analysis and monitoring of ship structural systems, particularly aluminum structures. Structural health monitoring (SHM) is an important part of that program, and efforts are being made to improve SHM technology to make it useful for lifetime management of ship structures as well as to provide operational guidance to ships’ force in order to minimize the possibility of incurring structural damage at sea.

Data Management Backbone for Embedded and PC-based Systems Using OSA-CBM and OSA-EAI

Cassidian is in the process of developing a comprehensive simulation framework for integrated system health monitoring and management research and development. One significant building block is to invite 1st class technology providers, e.g. Universities and SMIs, to provide innovative technologies and support their integration into the simulation framework. This paper is a joint presentation of Cassidian and Linova Software GmbH, a Cassidian preferred software provider.Prognostic Health Management (PHM) systems are commonly composed of disparate and distributed hard- and software components. Further, these components exchange vast amounts of data over a heterogeneous collection of communication channels. Any such system’s success depends upon an open, uniform, and performance-optimized solution for data management. A solution that includes: data definition, data communication, and data storage. The Open System Architecture for Condition-based Maintenance (OSA-CBM) and Open System Architecture for Enterprise Application Integration (OSA-EAI) are complementary reference architectures and represent an emerging standard for application domain-independent asset and condition data management. Herein, we will report on our experiences while implementing a data management backbone based on OSA-CBM and OSA-EAI for a simulation environment supporting PHM systems in the aerospace domain. Our work encompasses both airborne embedded systems and ground-based PC systems. While we can generally confirm the feasibility of OSA-CBM and OSA-EAI, we found several implementation recommendations unsuited to real-time operating conditions. To address these issues, we propose work towards standardizing non-XML-based transportation formats for OSA-CBM data packets. Further, we discovered issues specific to implementing the OSA-EAI data model in the aerospace domain. These issues drove our proposal to extend the OSA-EAI database model, where we seek to optimize its usability for analytical tasks. To underline the feasibility of our solutions, we provide empirical evidence drawn from our work. The conclusion is a summary of our experience and the direction of future work in the area of PHM system design for aircraft maintenance. In total, our contribution to the community is best seen from a practitioner’s perspective. We aim to establish best practices for and contribute to the evolution of OSA-CBM and OSA-EAI.

Monitoreo de Salud Estructural

Non-destructive methods for damage detection in civil structures have recently gained the attention of researchers throughout the world due to the advances in instrumentation technology and digital signal processing. Structural Health Monitoring techniques allows the presence, location and magnitude of damage to be detected due to changes in the static and dynamic characteristics of the structure. These techniques can be implemented remotely and in real-time, which can significantly reduce inspection costs and provide an instantaneous alert signal due to damage in the structure. The School of Civil Engineering and Geomatics of the Universidad del Valle has a Structural Health Monitoring research project that includes real-time monitoring of the Hormiguero bridge and an agreement with the Universidad Tecnológica de Pereira for joint monitoring of the Pereira-Dos Quebradas Viaduct.

Fiber Bragg Gratings, IT Techniques and Strain Gauge Validation for Strain Calculation on Aged Metal Specimens

This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG) sensors and infrared thermography (IT) techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and after aging using different adhesives. Moreover, a comparison has been made with IT techniques and conventional methods for calculating stresses in F114 steel. Implementation of Structural Health Monitoring techniques on real aircraft during their life cycle requires a study of the behaviour of FBG sensors and their wiring under real conditions, before using them for a long time. To simulate aging, specimens were stored in a climate chamber at 70 °C and 90% RH for 60 days. This study is framed within the Structural Health Monitoring (SHM) and Non Destructuve Evaluation (NDE) research lines, integrated into the avionics area maintained by the Aeronautical Technologies Centre (CTA) and the University of the Basque Country (UPV/EHU).

Vibration Characteristics of an Overpass Bridge During Full-Scale Destructive Testing

Progressive destructive testing is a schematic way of applying damage on a structure and evaluating the immediate effects in terms of the change in structural characteristics. Generally a progressive destructive test is conducted on a small scale specimen in a controlled environment such as laboratory. On-site full-scale progressive damage of an existing structure, which is rare considering cost and size of the structure, is an important learning opportunity in a framework of structural health monitoring research. Such a test provides an opportunity to observe the real change in structural characteristics which often masked by environment effects. Moreover such a test can be utilized as a benchmark for several damage detection methods. In this paper a full-scale progressive destructive test of an overpass post-tensioned bridge is presented. The bridge was instrumented with vibration sensors and the ambient acceleration responses were recorded during damage stages. Damage was introduced by cutting one of bridge piers at the footing level. This type of damage is expected to simulate a condition where a bridge suffers from a non-uniform pier settlement. By applying time and frequency domain vibration analysis, as well as system identification, evolution of dynamic characteristics caused by the damage is quantified. The results show that changes of natural frequencies are clearly visible, thus can be used as indicator of damage presence, while the change in mode shapes can be used as the local damage indicator.

Mobile Agent Computing Paradigm for Building a Flexible Structural Health Monitoring Sensor Network

Wireless structural health monitoring research has drawn great attention in recent years from various research groups. While sensor network approach is a feasible solution for structural health monitoring, the design of wireless sensor networks presents a number of challenges, such as adaptability and the limited communication bandwidth. To address these challenges, this paper explores the mobile agent approach to enhance the flexibility and reduce raw data transmission in wireless structural health monitoring sensor networks. An integrated wireless sensor network consisting of a mobile agent-based network middleware and distributed high computational power sensor nodes is developed. These embedded computer-based high computational power sensor nodes include Linux operating system, integrated with open source numerical libraries, and connected to multimodality sensors to support both active and passive sensing. The mobile agent middleware is built on a mobile agent system called Mobile-C. The mobile agent middleware allows a sensor network moving computational programs to the data source. With mobile agent middleware, a sensor network is able to adopt newly developed diagnosis algorithms and make adjustment in response to operational or task changes. The presented mobile agent approach has been validated for structural damage diagnosis using a scaled steel bridge.

Non-destructive testing of hardened cement specimens at microwave frequencies using a simple free-space method

In this research paper, we show microwave reflection and transmission properties measured from various sides of hardened mortar and concrete specimens with different water-to-cement ratios. These properties are important in predicting/measuring accurate electrical properties of cement-based materials which can eventually be utilized in structural health monitoring, public safety, and propagation-related research. Measurements are carried out by a simple and relatively inexpensive non-destructive free-space set-up with its newly developed calibration technique at X-band (8–12 GHz) during 3–36 months after samples’ preparation. A new approach (relative difference approach) is introduced for transmission properties to predict the state and degree of hydration inside specimens. It is shown that concrete specimens will complete the hydration sooner than mortar specimens with the same water-to-cement ratio ( w/ c) ratio due to heavy aggregates. In addition, among the specimens, while the concrete specimen with a higher w/ c ratio will exhibit faster hydration during approximately 3–6.1 months, the mortar specimen with a lower w/ c ratio will display rapid hydration during approximately 6.1–30 months. Besides, it is demonstrated that the magnitude of transmission properties for the top (or bottom) is less than those for the right (or left) side due to the effect of gravels and sand particles in specimens. Measurement results indicate that a varying electrical property depending on height should be used for cement-based materials in the predicting the channel properties in propagation-related researches.

長大橋の対風動態観測記録のヘルスモニタリング研究への活用

長大橋の対風動態観測記録のヘルスモニタリング研究への活用

Recommended guidelines for reporting on emergency medical dispatch when conducting research in emergency medicine: The Utstein style

To establish a uniform framework describing the system and organisation of emergency medical response centres and the process of emergency medical dispatching (EMD) when reporting results from studies in emergency medicine and prehospital care. In September 2005 a task force of 22 experts from 12 countries met in Stavanger; Norway at the Utstein Abbey to review data and establish a common terminology for medical dispatch centres including core and optional data to be used for health monitoring, benchmarking and future research.