1 / 17

Impact Echo CEE 498KUC march 14, 2007

Impact Echo CEE 498KUC march 14, 2007. Jordan Card & Jonathan Loo. Agenda. Introduction to Impact Echo Theory Instrumentation Purpose Operation Interpretation Strengths/Weaknesses Commercial Products References. Introduction. Non-destructive test

tanner
Download Presentation

Impact Echo CEE 498KUC march 14, 2007

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Impact EchoCEE 498KUCmarch 14, 2007 Jordan Card & Jonathan Loo

  2. Agenda • Introduction to Impact Echo • Theory • Instrumentation • Purpose • Operation • Interpretation • Strengths/Weaknesses • Commercial Products • References

  3. Introduction • Non-destructive test • Looks for flaws/imperfections in the material • Can estimate thickness to within 3% (Sansalone) • Primarily used for concrete & masonry • “Local” in scope of testing • Approx. 25 years old • Ultrasonic pulse echo (1940’s) • Ineffective (>100kHz) • Similar idea to chain dragging

  4. Zhu, Popovics, Schubert, J of Acoust. Soc. Amer. 116 (4), 2004 Theory – Stress (Sound or pressure) waves A mechanical impact creates stress waves through a material. These (reflected)waves can be measured to gage depth of a discontinuity. Certain waves will dominate based on the location of the discontinuity. Wave velocities must be known to determine depth of flaw.

  5. Instrumentation • Steel ball (4-15mm) impacts (2-10 m/s) the concrete, creating stress waves (<80kHz & λ=5cm-6m). • Transmitter  Pulse echo • Can be spring loaded • Start from large impactor small • Transducer measures surface displacements • Placed adjacent to impactor • Measures primarily P-waves • Piezoelectric • Source: http://ciks.cbt.nist.gov/~carino/ie_Fig2.GIF

  6. Purpose • Plain, reinforced and post-tensioned concrete • Can be used to sense: • Cracks • Delamination • Voids • Honeycombing • Debonding

  7. Operation • Impact produces stress waves in the material; reflected waves from voids are detected by the transducer • These reflected waves set up a resonance condition having a distinctive frequency • Waveform is transformed into spectra (FFT) • Should have an idea of what to look for • Size of flaw • Operate parallel to regular occurring grooves

  8. Interpretation Peaks are associated with a certain “characteristic frequency”, specifying a distance to the discontinuity.

  9. Strengths and Weaknesses • Only need access to one surface • Internal flaws can be detected • Can determine depth of the internal flaws • Easily repeatable • Can construct a map of discontinuities • Data can be difficult to interpret; especially on thick plates or on layered materials (overlays, soil) • R-waves (clipping) • Layered- needs special attention • Small voids can be missed • limited by size of wavelength • Attenuation (esp. short wave) • Complicated geometries poses difficulties • Flaws beneath sensed flaw must be evaluated from the opposite side • Flaw detection length constraints: • Lmin = d/4, L>d/3 • Requires adequate frequency resolution

  10. Equipment Basic Test Set Up Portable Impact Echo (PIES) Test Set Up Source: www.impact-echo.com

  11. Transducers Cylindrical Transducer Pistol Grip Transducer Dual-Head Transducer Source: www.impact-echo.com

  12. Use of Each Transducer • Cylindrical – For testing in narrow and confined spaces • Pistol Grip – is easier to use and well suited to flat surfaces. • Dual Head – Used for independent measurements of wave speed which can be used to determine depth and thickness

  13. ASTM C 1383 Procedures Two-step procedure for measuring plate thickness: Procedure A is used to determine the P-wave speed and Procedure B is used to determine the thickness frequency. Source: http://www.fire.nist.gov/bfrlpubs/build01/PDF/b01005.pdf

  14. Suppliers and Costs Impact Echo Instruments www.impact-echo.com System “A” - $12,500 System “B” - $11,500 System “C” - $9,500 Olson Instruments www.olsoninstruments.com IE 1 - $5,000 IE 2 - $10,000 IE T - $13,000 Qualitest USA www.WorldofTest.com PIES System - $16,995

  15. Test Standards • ASTM Standard C1383-98a for measuring the p-wave speed and thickness of concrete plates using the impact echo method • ACI 228.2R-98 Nondestructive Test Methods for Evaluation of Concrete Structures

  16. References • www.impact-echo.com • www.WorldofTest.com • www.olsoninstruments.com • http://ciks.cbt.nist.gov/~carino/ieprin.html • http://www.fire.nist.gov/bfrlpubs/build01/PDF/b01005.pdf • M. Sansalone and W. Streett, Impact-Echo: Nondestructive Evaluation of Concrete and Masonry, 1997.

  17. Questions?

More Related