Monitoring of Overhead Polymer Core Composite Conductors Under Excessive Mechanical Loads Using Fiber Bragg Grating Sensors

This combined experimental and numerical study addresses mechanical effects associated with static and dynamic loading of novel High Temperature Low Sag (HTLS) transmission line polymer core composite conductors. The developed methodology was successfully applied to ACCC® to explain the complex failure mechanisms associated with combined bending and tension loading. Furthermore, the use of Fiber Bragg Grating (FBG) sensors was investigated for the first time to monitor the ACCC® design during installation and in-service. Transverse low-velocity impacts to the ACCC® conductor having either free or constrained end conditions and large axial tensile loads were performed. It was identified that the most damaging condition under impact is when the conductor had free ends and was thus subjected to severe bending. The experimental work performed using an original approach was supported by non-linear static and dynamic finite element analyses. For the multiaxial case of rods subjected to bending and axial tension, the axial stresses were predicted analytically and numerically with the likely failure initiating locations identified based on the theoretical composite compressive strengths. The initiating damage mechanisms change from compressive to tensile modes as axial tension increases. It has been shown for the first time that the natural presence of fiber misalignment must be considered in the failure analysis of hybrid composite rods as it can significantly reduce bending strength and influence the location of damage initiation. It has been demonstrated that FBG sensing is a viable technique for in-service monitoring of ACCC® conductors subjected to a variety of static and impact situations. Under static and low energy/velocity conditions, surface mounted sensors can accurately measure strains both on the bare rods and inside the conductors. The tests on the fullscale conductors under low energy impact also showed that the sensors can identify the location and magnitude of impact with a high degree of sensitivity. These results, combined with the intrinsic properties of optical sensors and fibers, indicate the FBG sensors could be especially useful in the monitoring of low and high energy impact events in-service. Finally, an evaluation of using of embedded FBG sensors inside the hybrid composite core of ACCC® is presented

Intensity based interrogation of optical fibre sensors for industrial automation and intrusion detection systems

In this study, the use of optical fibre sensors for intrusion detection and industrial automation systems has been demonstrated, with a particular focus on low cost, intensity-based, interrogation techniques. The use of optical fibre sensors for intrusion detection systems to secure residential, commercial, and industrial premises against potential security breaches has been extensively reviewed in this thesis. Fibre Bragg grating (FBG) sensing is one form of optical fibre sensing that has been underutilised in applications such as in-ground, in-fence, and window and door monitoring, and addressing that opportunity has been a major goal of this thesis. Both security and industrial sensor systems must include some centralised intelligence (electronic controller) and ideally both automation and security sensor systems would be controlled and monitored by the same centralised system. Optical fibre sensor systems that could be used for either application have been designed, developed, and tested in this study, and optoelectronic interfaces for integrating these sensors with electronic controllers have been demonstrated. The versatility of FBG sensors means that they are also ideal for certain mainstream industrial applications. Two novel transducers have been developed in this work; a highly sensitive low pressure FBG diaphragm transducer and a FBG load cell transducer. Both have been designed to allow interrogation of the optical signal could occur within the housing of the individual sensors themselves. This is achieved in a simple and low cost manner that enables the output of the transducers to be easily connected to standard electronic controllers, such as programmable logic controllers. Furthermore, some of the nonlinear characteristics of FBG sensors have been explored with the aim of developing transducers that are inherently decoupled from strain and temperature interference. One of the major advantages of optical fibre sensors is their ability to be both time division and wavelength division multiplexed. The intensity-based interrogation techniques used here complement this attribute and are a major consideration when developing the transducers and optoelectronic circuits. A time division multiplexing technique, using transmit-reflect detection and incorporating a dual bus, has also been developed. This system architecture enables all the different optical fibre transducers on the network to have the same Bragg wavelength and hence the number of spare replacement transducers required is minimal. Moreover, sensors can be replaced in an online control system without disrupting the network. In addition, by analysing both the transmitted and reflected signals, problems associated with optical power fluctuations are eliminated and the intensity of the sensor signals is increased through differential amplification. Overall, the research addresses the limitations of conventional electrical sensors, such as susceptibility to corrosive damage in wet and corrosive environments, and risk of causing an explosion in hazardous environments, as well as the limitations of current stand-alone optical fibre sensor systems. This thesis supports more alert, reliable, affordable, and coordinated, control and monitoring systems in an on-line environment

Bridges Structural Health Monitoring and Deterioration Detection Synthesis of Knowledge and Technology

INE/AUTC 10.0

Development and application of a borehole stress meter in rocks surrounding the roadway, based on optical-fiber sensing technology

Stress in rock masses is an important parameter in the design and construction of underground engineering, such as the design and maintenance of mine roadways and the design of mining working faces. It is also a fundamental force causing the deformation and failure of geotechnical engineering excavation. At present, the abutment-pressure monitoring technology of the surrounding rocks of the coal mine roadway in China is not intelligent and systematic and lacks some high-precision sensing instruments and multi-functional monitoring systems. The mechanical model of the rocks surrounding the borehole was constructed by theoretical analysis of problems in the stress monitoring technology for underground rock masses in coal mines. Additionally, the interaction between the surrounding rocks and the borehole stress meter was analyzed. The borehole stress meters for tubular-structure fiber Bragg grating (TS-FBG) and cystic-structure fiber Bragg grating (CS-FBG) were designed by combining the sensing principle and sensing characteristics of fiber Bragg grating, and the performance of the two kinds of fiber Bragg grating borehole stress meters was compared by laboratory test. The track roadway of the 14,301 tested working faces in the Shaqu Coal Mine was taken as an example, and the stress of the rocks surrounding the 14,301-track roadway was monitored in real time by CS-FBG borehole stress meter during the mining of the working face. The following conclusions are drawn from the field application. The rig-site utilization results revealed obvious stress growth and stress peak zones in the mining-stress change curves of each measuring point on the two sides of the 14,301-track roadway in the process of mining the tested working face. Additionally, there were four stages: rapid rise, uniform growth, rapid rise to the peak, and rapid decline. Maximum stress monitored by the second station was 18.5 MPa, and the influence range of stress was over 140 m. Maximum stress monitored by the first measuring station was 19 MPa, the influence range of stress was about 80 m, and the peak stress position was about 20 m in front of the coal wall. Rig-site utilization proved the design of the CS-FBG borehole stress meter to be reasonable. Performance was stable and reliable, and the successful operation of field monitoring achieved the expected effect

NASA Tech Briefs, September 2012

Topics covered include: Beat-to-Beat Blood Pressure Monitor; Measurement Techniques for Clock Jitter; Lightweight, Miniature Inertial Measurement System; Optical Density Analysis of X-Rays Utilizing Calibration Tooling to Estimate Thickness of Parts; Fuel Cell/Electrochemical Cell Voltage Monitor; Anomaly Detection Techniques with Real Test Data from a Spinning Turbine Engine-Like Rotor; Measuring Air Leaks into the Vacuum Space of Large Liquid Hydrogen Tanks; Antenna Calibration and Measurement Equipment; Glass Solder Approach for Robust, Low-Loss, Fiber-to-Waveguide Coupling; Lightweight Metal Matrix Composite Segmented for Manufacturing High-Precision Mirrors; Plasma Treatment to Remove Carbon from Indium UV Filters; Telerobotics Workstation (TRWS) for Deep Space Habitats; Single-Pole Double-Throw MMIC Switches for a Microwave Radiometer; On Shaft Data Acquisition System (OSDAS); ASIC Readout Circuit Architecture for Large Geiger Photodiode Arrays; Flexible Architecture for FPGAs in Embedded Systems; Polyurea-Based Aerogel Monoliths and Composites; Resin-Impregnated Carbon Ablator: A New Ablative Material for Hyperbolic Entry Speeds; Self-Cleaning Particulate Prefilter Media; Modular, Rapid Propellant Loading System/Cryogenic Testbed; Compact, Low-Force, Low-Noise Linear Actuator; Loop Heat Pipe with Thermal Control Valve as a Variable Thermal Link; Process for Measuring Over-Center Distances; Hands-Free Transcranial Color Doppler Probe; Improving Balance Function Using Low Levels of Electrical Stimulation of the Balance Organs; Developing Physiologic Models for Emergency Medical Procedures Under Microgravity; PMA-Linked Fluorescence for Rapid Detection of Viable Bacterial Endospores; Portable Intravenous Fluid Production Device for Ground Use; Adaptation of a Filter Assembly to Assess Microbial Bioburden of Pressurant Within a Propulsion System; Multiplexed Force and Deflection Sensing Shell Membranes for Robotic Manipulators; Whispering Gallery Mode Optomechanical Resonator; Vision-Aided Autonomous Landing and Ingress of Micro Aerial Vehicles; Self-Sealing Wet Chemistry Cell for Field Analysis; General MACOS Interface for Modeling and Analysis for Controlled Optical Systems; Mars Technology Rover with Arm-Mounted Percussive Coring Tool, Microimager, and Sample-Handling Encapsulation Containerization Subsystem; Fault-Tolerant, Real-Time, Multi-Core Computer System; Water Detection Based on Object Reflections; SATPLOT for Analysis of SECCHI Heliospheric Imager Data; Plug-in Plan Tool v3.0.3.1; Frequency Correction for MIRO Chirp Transformation Spectroscopy Spectrum; Nonlinear Estimation Approach to Real-Time Georegistration from Aerial Images; Optimal Force Control of Vibro-Impact Systems for Autonomous Drilling Applications; Low-Cost Telemetry System for Small/Micro Satellites; Operator Interface and Control Software for the Reconfigurable Surface System Tri-ATHLETE; and Algorithms for Determining Physical Responses of Structures Under Load

Research and Technology, 1995

This report presents some of the challenging research and technology accomplished at NASA Ames Research Center during FY95. The accomplishments address almost all goals of NASA's four Strategic Enterprises: Aeronautics and Space Transportation Technology, Space Sciences, Human Exploration and Development of Space, and Mission to Planet Earth. The report's primary purpose is to inform stakeholders, customers, partners, colleagues, contractors, employees, and the American people in general about the scope and diversity of the research and technology activities. Additionally, the report will enable the reader to know how these goals are being addressed

2003 Research Engineering Annual Report

Selected research and technology activities at Dryden Flight Research Center are summarized. These activities exemplify the Center's varied and productive research efforts