Howard Chung

Challenges in Meeting the Framework for SHM System Certification and Compliance

Monitoring the continued health of aircraft subsystems and identifying problems before they affect airworthiness has been a long-term goal of the aviation industry. Towards this end, Structural Health Monitoring (SHM) systems that could be used for the in-service monitoring of the health of new and existing aircraft structures are being matured. This paper will go step-by-step into the various challenges associated with meeting preliminary certification compliance requirements. A 5-year program completed under funding from the Federal Aviation Administration will be used as a guide to lead the reader through the various certification compliance steps The objectives of this program were to (1) develop, validate, and demonstrate Smart Patch System (SPS) technologies including advanced software, algorithms, and methodologies for structures and dynamic components to (a) detect fatigue cracks and damages before exceeding critical threshold or incipient failure and (b) characterize fatigue cracks and damages, and (2) develop preliminary certification compliance requirements and a framework for certification of an SPS that would be integrated into a Health and Usage Monitoring System (HUMS) for the fatigue crack monitoring of commercial rotorcraft structures per the guidelines provided in FAA Advisory Circular AC 29-2C, Section MG-15. This paper will use this program as a guide to discuss certification compliance challenges and recent work done to meet them. It presents the details on the tasks that were conducted towards the development, validation, and potential certification of the SPS and other similar SHM systems for specific structural applications.

A Robust and Effective Approach Towards Accelerated Dent-mapping using a Purposebuilt 3D Optical Inspection Tool

Dent-mapping of the aircraft skin remains a critical component in today’s maintenance, repair, and overhaul (MRO) industry. In addition to effectively and efficiently mapping dents on aircraft during regularly scheduled Base Maintenance, inspectors on the ground are under much higher time-pressure to complete the same dent-mapping task with high accuracy during unplanned Line Maintenance. This is a phenomenon that constantly plagues the MRO industry as pressure to reduce aircraft turn-around-time (TaT) continues to increase. Traditional manual methods are subjective, inaccurate, inconsistent, and extremely time-consuming. In pursuit of a technology that offers total efficiency gains in an end-to-end digital dent-mapping workflow, 8tree proposed the following requirements: (1) Zero-programming and minimal learning curves so that workers of all skill levels can operate the tool; (2) No special surface preparation requirements; (3) No post-processing software packages or need to develop specialized metrology knowledge; (4) Handheld portability and ease of maneuvering. This paper highlights the successful integration of a 3D digitization technique – structured-light scanning, and the proprietary analytics developed by 8tree to solve chronic surface inspection problems within the MRO industry. The principle of operation of dentCHECK®, a novel 3D digital surface inspection tool, as well as the design principles that helped shape the product during the early product development days will be discussed. In addition, two use cases – blend out assessment, and lightning strike assessment will also be discussed.

Development of a Multi-Functional Installed Ultrasonic System for Detection of Pitting Corrosion and Bolt Loosening on Aerospace Vehicles

This paper presents an innovative new Pitting Corrosion Sensor Tracker (PCST) system for the detection and monitoring of pitting corrosion, bolt preload, and clamping force changes in critical areas of the rotorcraft structure. The system utilizes small integrated ultrasonic sensor networks that can be installed on complex rotorcraft structures for monitoring of pitting corrosion and clamping force combined with miniaturized sensors installed on the fasteners to monitor the preload forces. By combining these two sensor technologies together and analyzing the data they provide using sophisticated waveform and information extraction algorithms, the PCST system becomes a complete technology solution for the monitoring of component mounting areas. Acellent Technologies in partnership with NAVAIR has tested the proposed PCST system on rotorcraft components under real corrosion conditions. The methodology and results of the corrosion testing will be discussed in the paper. doi: 10.12783/SHM2015/98

Evaluation of Long-term Flight Data from On-board SMART Layers

One of the major challenges in Structural Health Monitoring (SHM) techniques for aerospace applications is sensor survivability in actual flight conditions for certification. Data are needed to demonstrate that SHM sensors can sustain and survive harsh aerospace flight environments for a long period of time. This paper presents the results of a 72 month (6-year) study of sensor data from Acellent’s SMART layers that were permanently mounted onto a UH-60 Black Hawk helicopter at NASA Ames in California. The study was conducted under a Cooperative Research and Development Agreement (CRADA) with the US Army Research Laboratory (ARL), the Aviation Development Directorate - Aeroflightdynamics Directorate (ADD-AFDD) located at NASA Ames and Acellent Technologies to enhance, validate, and demonstrate the SHM technique and system that can potentially be used to enable condition-based maintenance (CBM) of aircraft structures. A UH-60L Blackhawk rotorcraft installed with SMART Layer piezoelectric actuators and sensors has been flying under the CRADA research program since 2009. The sensors have been subjected to various operational conditions such as loading, vibration, thermal cycling during flight and, heavy dust conditions at the Yuma Proving Ground. Selected results are presented in this paper (additional information is available in ref [1]). doi: 10.12783/SHM2015/335

Long Sensor Layers for Machinery Monitoring

Monitoring the integrity of rotating roller(s) of paper machinery equipment to optimize the paper production processing parameters is crucial to improve the production efficiency and quality of paper sheet and board products. The paper manufacturing industry has found that they can obtain significant cost savings by improving the nip profiles, parent roll hardness profiles and tension profiles for those rolling components in the machines. Utilizing Acellent’s SMART Layer sensing technology, a real-time integrity detection system was developed by Valmet for in-situ integrity monitoring of rotating roller(s). Valmet’s iRoll is the fastest and most sensitive on-line profile measurement tool in the industry. The iRoll can be utilized on a covered roll in paper, board, pulp or tissue production machines to expand the roll’s primary function to include use as a transducer for sensing cross-machine nip linear load or sheet properties such as the tension and parent roll hardness profile. The system is comprised of a long sensor layer, up to 12 meter in length permanently mounted on the metallic roll surface at an angle to measure the force. The sensor rotates under the wrap angle generating a continuous load signal. A mapping of the profiles can then be generated on the basis of the angular position of the roll. Data is processed by a signal conditioning module and transmitted from the rotating roll using a digital radio transmission. This system can evaluate and diagnose uniformity of loading or tension on the surface of roll. Testing has shown that the Sensor Layer, designed from the SMART Layer sensing technology, when mounted on the surface of metallic roll under a composite protective wrap can survive the harsh environmental conditions that a roller undergoes throughout its operational lifetime. The SMART Layer has been evaluated by Valmet and has demonstrated its efficacy for monitoring the integrity of paper manufacturing machines. doi: 10.12783/SHM2015/180

Maturation of Real-time Active Pipeline Integrity Detection System for Natural Gas Pipelines

Current natural gas pipelines are at risk of suffering mechanical damage either by degradation, third party strikes or natural events, (e.g. landslides, earthquake-induced liquefaction or other ground movement). When such damage is located, the pipe must be exposed and inspected to determine if the damaged areas require repair or replacement. There is no reliable, built in, non-destructive method for determining if the damage is sufficient to have a material effect on operational safety. Current inspection techniques for damage from impacts, fatigue, or corrosion generally require the pipeline to be shut down during inspection, resulting in loss of revenue and economic benefits. Acellent developed a Real-time Active Pipeline Integrity Detection (RAPID) system that is designed for gas pipelines for monitoring corrosion, cracks and leaks. The core of the system is an integrated structural health monitoring (SHM) technology that originated in the aerospace industry and is increasingly being evaluated by the pipeline industry for improving the safety and reliability of pipeline structures. Significant benefits are expected in all fields of application to reduce the maintenance costs and to improve the efficiency of the structural design. The aim of this technology is not simply to detect structural failure, but to provide an early indication of physical damage. The early warning provided by an SHM system can then be used to define remedial strategies before the structural damage leads to catastrophic failure. This paper will provide an overview of a two-year research and development program funded by the California Energy Commission for the maturation of the RAPID system and its testing and validation with Pacific Gas & Electric (PG&E) in San Ramon, CA. Current results have shown the system to be reliable and effective for the early detection of pipeline damage, and the technology has been deemed to be effective for in-field gas pipeline safety monitoring. doi: 10.12783/SHM2015/50