MECH 513: Smart Materials and Intelligent Structural Systems
MECH 512: Design for Structural Integrity
MECH 513: Smart Materials and Intelligent Structural Systems

Condition Monitoring (CM)  -  Structural Health Monitoring (SHM)

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Condition Monitoring (CM)

Condition monitoring is the use of advanced technologies to determine the condition of equipment and predict its failure.  This in turn should inform predictive maintenance (PM) or reliability-centred maintenance (RCM).  Taylor [1] has suggested that "just as your physician uses a variety of tests and evaluations to assess your state of health, we should do the same for our machinery" and that there are six steps to a healthy machine:

  1. First ask, what are the possible failures?
  2. Next ask, which of these failures are significant?
  3. Next ask, how can we avoid these failures?
  4. Then ask, when we can’t avoid failure, how can we get an early warning?
  5. Then, tailor a suite of tests to detect those early warning signs.
  6. Finally, collect the results of the tests at one decision point.

Techniques that can be used include:

Lloyd’s Register’s integrated condition monitoring service (ICMS) [2] proposes that "integrated condition monitoring helps optimise maintenance by judging the health of machinery using non-invasive sensing technology".  The consequent benefits of the ICMS approach are:

Risk-based inspection (RBI) is a method for deciding which components to inspect.  Instead of a fixed inspection interval, RBI considers the risk of an item of plant or of a  component failing and decides the inspection interval on that basis.  A description of the Risk Assessment methodology (in the context of composites manufacture) can be found on the appropriate MATS324 page.  The basic approach is to consider the Probability and the Consequence (severity) of failure separately either as a range or simply as low/medium/high and endeavour to move to the calculated risk from top right to lower left or increase the inspection interval as the risk moves towards the top right in the diagram below:

   Consequence of failure
Low Medium High
Probability of Failure High     HIGH RISK
Medium      
Low LOW RISK    

For more information on Risk Based Inspection, see references 3-5.  For more information on Condition Monitoring, see the review by Heyns [6], the international standards [7-13] and the other resources below.

References

  1. James W. Taylor, Six Steps to A Healthy Machine, http://www.reliabilityweb.com/art05/6_steps_machine_health.htm, accessed 06 February 2006.
  2. Integrated condition monitoring – helping to reduce maintenance costs and enhance machinery reliability, http://www.lr.org/Industries/Marine/Services/Consultancy/Integrated+condition+monitoring+service.htm, accessed 28 October 2006.
  3. JB Wintle, BW Kenzie, GJ Amphlett and S Smalley (TWI and Royal & SunAlliance Engineering), Best practice for risk based inspection as a part of plant integrity management, Health and Safety Executive Contract Research Report 363/2001, 2001.  ISBN 0 7176 2090 5 [3 MB PDF].
  4. W Geary, Risk Based Inspection - A Case Study Evaluation of Onshore Process Plant, Health and Safety Laboratory HSL/2002/20, Sheffield, 2002.
  5. Best practice for risk based inspection as a part of plant integrity management, Health and Safety Laboratory CRR 363/2001, Sheffield, 27 September 2005.
  6. PS Heyns [21 references], Tool condition monitoring using vibration measurements - a review, Insight (BJNDT), August, 2008, 49(8), 447-450.
  7. ANSI/IEC/ISO 17024:2003 Conformity assessment - General requirements for bodies operating certification of persons.
  8. ISO 18436-1:2004 Condition monitoring and diagnostics of machines - Requirements for training and certification of personnel - Part 1: Requirements for certifying bodies and the certification process
  9. ISO 18436-2:2003 Condition monitoring and diagnostics of machines - Requirements for training and certification of personnel - Part 2: Vibration condition monitoring and diagnostics
  10. ISO/DIS 18436-3 Condition monitoring and diagnostics of machines - Requirements for training and certification of personnel - Part 3: Requirements for training bodies and the training process
  11. ISO/DIS 18436-4 Condition monitoring and diagnostics of machines - Requirements for training and certification of personnel - Part 4: Field lubricant analysis
  12. ISO/DIS 18436-6 Condition monitoring and diagnostics of machines - Requirements for training and certification of personnel - Part 6: Acoustic emission
  13. ISO/DIS 18436-8 Condition monitoring and diagnostics of machines - Requirements for training and certification of personnel - Part 8: Thermography

Other resources

  1. Sandy Dunn, Condition Monitoring in the 21st Century,  http://www.plant-maintenance.com/articles/ConMon21stCentury.shtml, accessed 06 February 2006.
  2. RK Mobley, Predictive maintenance, Chapter 50 of Plant Engineers' Handbook ISBN 0-7506-7328-1.
  3. Richard Overman and Roger Collard, The complimentary roles of reliability centred maintenance and condition monitoring, IMC-2003: 18th International Maintenance Conference, 8-9 December 2003. http://www.reliabilityweb.com/art04/collard.pdf, accessed 06 February 2006.
  4. Steve Reilly, Integrating Inspection-Based and Reliability-Based Information, http://www.reliabilityweb.com/excerpts/excerpts/integrating.htm, accessed 06 February 2006.
  5. JK Paik and R E Melchers (editors), Condition assessment of aged structures, Woodhead Publishing, Cambridge, October 2008. ISBN-13: 978-1-84569-334-3.

Structural Health Monitoring (SHM)

Structural Health Monitoring (SHM) is a damage detection process used for aerospace, civil and mechanical engineering infrastructure which monitors the system over time.  Typically, an array of sensors collects dynamic response measurements either continuously or at regular intervals.  The basis for SHM is that a normal response can be determined soon after installation.  This response may be a statistical database: e.g. a highway bridge probably has most activity during rush-hour  Changes in this response, or unusual features in the signal, will then suggest there has been a departure from the normal loading situation and/or the possibility of damage.  Over time the output of the monitoring process may change due to the inevitable aging and degradation of the structure resulting from the operational environment, and/or from ageing of the sensors and instrumentation.  SHM can be particularly useful after catastrophic events (flooding, earthquakes or explosions) for rapid assessment of the integrity of the structure.

A number of review articles exist:

De Leeuw and Brennan [8] identified a need for the development of objective measures to quantitatively assess the performance characteristics of monitoring technologies. They present the background and development of such a measure of performance based on fatigue and fracture mechanics failure models of the host structure. The structural integrity monitoring index (SIMdex) can use any failure model and criterion and means that structural integrity monitoring technologies can be objectively judged solely on their suitability for specific applications.

There exist several targetted initiatives where SHM may be applied:

An associated technology for cost reduction in the context of Structural Health Monitoring is Virtual Testing Risk Management Methodology [9].

References

  1. SW Doebling, CR Farrar, MB Prime and DW Shevitz, Damage Identification and Health Monitoring of Structural and Mechanical Systems from Changes in their
    Vibration Characteristics: A Literature Review, Los Alamos National Laboratory report LA-13070-MS, 1996. http://www.lanl.gov/projects/damage_id/reports/lit_review.pdf, accessed 06 February 2006.
  2. SW Doebling, CR Farrar, MB Prime and DW Shevitz, A review of damage identification methods that examine changes in dynamic properties, Shock and
    Vibration Digest, 1998, 30(2), 91–105: a condensed version of reference 1.
  3. Hoon Sohn, CR Farrar, FM Hemez, DD Shunk, DW Stinemates and BR Nadler, A Review of Structural Health Monitoring Literature: 1996–2001, Los Alamos National Laboratory Report, LA-13976-MS, 2003. http://www.lanl.gov/projects/damage_id/reports/LA_13976_MS_Final.pdf, accessed 06 February 2006.
  4. I Milne, R Ritchie and B Karihaloo, Comprehensive Structural Integrity (10-volume reference work), Elsevier, 2003. ISBN13: 9780-08-043749-1.
  5. Lisa Fixter and Caroline Williamson, State of the Art Review: Structural Health Monitoring, QinetiQ/S&DU/T&P/E&M/TR0601122, 2006.
  6. P M Pawar and R Ganguli, Helicopter rotor health monitoring- a review, Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 2007, 221(5), 631-647.
  7. Y Zou, L Tong and GP Steven, Vibration-based model-dependent damage (delamination) identification and health monitoring for composite stuctures - a review, Journal of Sound and Vibration, 2000, 230(2), 357-378.
  8. B de Leeuw and FP Brennan, Structural integrity monitoring index (SIMdex): a methodology for assessing structural health monitoring technologies, Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 2009, 223(5), 515-524.
  9. F Abdi, T Castillo and E Shroyer, Risk Management of Composite Structure, in Efstratios Nikolaidis, DM Ghiocel and Suren Singhal, Engineering Design Reliability Handbook, CRC Bress, Boca Raton, December 2004. ISBN-13: 9780849311802. ISBN: 0-8493-1180-2.

Other resources

Software

Condition Monitoring

Structural Health Monitoring

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Created by John Summerscales on 06 February 2006 and updated on 07 August 2009 11:42. Terms and conditions. Errors and omissions. Corrections.
Advanced Composites Manufacturing Centre
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