Experimental Mechanics

, Volume 17, Issue 9, pp 347–353 | Cite as

The measurement and significance of energy in acoustic-emission testing

Purpose of investigation is to present an approach to measuring the energy sensed by an acoustic-emission transducer and to present experimental results that compare energy measurements with couting and RMS measurements in several different types of tests
  • D. O. Harris
  • R. L. Bell


A technique for measuring the energy sensed at an acoustic-emission transducer is presented that utilizes a squaring circuit and digital integrator. Theoretical relationships between energy and other more conventional acoustic-emission parameters, such as counts and RMS voltage, are derived for certain idealized cases. Experimental results from the following types of tests are presented: (1) unflawed tensile (‘continuous’ emission); (2) precracked stress-corrosion cracking; (3) precracked fracture toughness; and (4) fatigue-crack growth. Energy, counts, RMS-voltage, energy/event and counts/event measurements are included. In the case of unflawed tensile specimens, energy techniques appeared somewhat superior to counts. In all other cases, a direct relationship between counts and energy was obtained. Energy measurements tended to give a larger weight to higher amplitude events. Other than this, energy measurements appeared to have no advantage over counts. The theoretical relationship predicted between energy/event and count/event agreed quite well with experimental observations. Overall, the test results presented indicate that energy techniques provide no significant advantage over counting threshold crossings in cases in which crack extension in metals is the primary source of acoustic emission.


Fracture Toughness Fluid Dynamics Acoustic Emission Tensile Specimen Idealize Case 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



a constant [see eq (3)]


frequency of oscillations in an acoustic-emission signal


gain of amplifier chain to counter


gain of amplifier chain to energy processor


counts for a single event


total acoustic-emission counts


acoustic-emission count rate


acoustic-emission counts/load cycle


tensile load


value of RMS-voltage signal above background noise




time for acoustic-emission signal to counter to ring down below trigger level of counter


time for acoustic-emission signal to digital integrator in energy processor to ring down to trigger level of processor


energy for a single event


total acoustic-emission energy


energy rate/s, V2-s/s


acoustic-emission energy/load cycle




amplitude of continuous-emission signal


initial amplified and filtered voltage from single event to counter


initial amplified and filtered voltage from single event to energy processor


amplified and filtered acoustic-emission signal to counter


amplified and filtered acoustic-emission signal to energy processor


threshold voltage in counter


threshold voltage in energy processor


tensile strain, percent


decay time of acoustic-emission signal [see eq (3)]


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Acoustic Emission, ASTM Special Tech. Pub. No. 505, ASTM, Philadelphia, PA (1972).Google Scholar
  2. 2.
    Dunegan, H.L. andTetelman, A.S., “Nondestructive Characterization of Hydrogen Embrittlement Cracking by Acoustic Emission Techniques,”Enrg. Fract. Mech.,2,387–402 (Jun. 1971).Google Scholar
  3. 3.
    Harris, D.O., Dunegan, H.L. and Tetelman, A.S., “Prediction of Fatigue Lifetime by Combined Fracture Mechnics and Acoustic Emission,” Proc. Air Force Conf. Fatigue and Fracture of Aircraft Structures and Materials, AFFDL Rep. AFFDL TR 70-144, 459–471 (1970).Google Scholar
  4. 4.
    Harris, D.O. andDunegan, H.L., “Continuous Monitoring of Fatigue Crack Growth by Acoustic-emission Techniques,”Experimental Mechanics,14 (2),71–81 (Feb. 1974).CrossRefGoogle Scholar
  5. 5.
    Dunegan, H.L. andHarris, D.O., “Acoustic Emission Techniques,”Exper. Tech. Fract. Mech., Kobayashi, A.S., ed., SESA, Westport, CT, Ch. 3, 38–75 (1973).Google Scholar
  6. 6.
    Magnani, N.J., “Acoustic Emission and Stress-corrosion Cracking of U-4 1/2 wt. % Nb,” Experimental Mechanics,13 (12) (Dec. 1973).Google Scholar
  7. 7.
    Harris, D.O., Tetelman, A.S. andDarwish, F.A.I.Detection of Fiber Cracking by Acoustic Emission,”Acoustic Emission, ASTM Special Tech. Pub., No. 505, ASTM, Philadelphia, PA, 238–249 (1972).Google Scholar
  8. 8.
    Brindley, B.J., Holt, J. andPalmer, I.G., “Acoustic Emission—3, The Use of Ringdown Counting,”Non-Destructive Testing,6,299–306 (Dec. 1973).CrossRefGoogle Scholar
  9. 9.
    Dunegan, H.L. andGreen, A.T., “Factors Effecting Acoustic Emission Response from Materials,”Acoustic Emission, ASTM Special Tech. Pub. No. 505, ASTM, Philadelphia, PA, 100–113 (1972).Google Scholar
  10. 10.
    Hutton, P.H., “Acoustic Emission Applied Outside the Laboratory,”ibid, (1972)114–128.Google Scholar
  11. 11.
    Beattie, A.G. and Jaramillo, R.A., “The Measurement of Energy in Acoustic Emission,” Sandia Laboratories, Albuquerque, NM (undated).Google Scholar
  12. 12.
    Tetelman, A.S., “Acoustic Emission, and Fracture Mechanics Testing of Metals and Composites,” Materials Department, UCLA, No. UCLA-ENG-7249, presented U.S.-Japan Joint Symp. Acoustic Emission, Tokyo, Japan (Jul. 1972).Google Scholar
  13. 13.
    Hamstad, M.A. andMukherjee, A.K., “The Dependence of Acoustic Emission on Strain Rate in 7075-T6 Aluminum,”Experimental Mechanics,14 (1),33–41 (Jan. 1974).CrossRefGoogle Scholar
  14. 14.
    Wessel, E.T., “State of the Art of the WOL Specimen for K Ic Fracture Toughness Testing,”Engrg. Fract. Mech.,1 (1),77–103 (Jun. 1968).Google Scholar
  15. 15.
    Johnson, H.H. andParis, P.C., “Subcritical Flaw Growth,”ibid., 3–46.Google Scholar
  16. 16.
    Bell, R.L., “Acoustic Emission Transducer Calibration—Transient Pulse Method,”Dunegan/Endevco Tech. Rep. No. DE-73-3, Dunegan/-Endevco, San Juan Capistrano, CA (Feb. 1973).Google Scholar
  17. 17.
    Harris, D.O., “The Effect of Gain and Frequency Bandpass on Acoustic Emission Observed from Growing Fatigue Cracks,” Dunegan/-Endevco Technical Report No. DE-74-4, San Juan Capistrano, CA (Jan. 1974). Presented at Symp. Schallemission Anwendung bei der Untersuchung, Prufung und Uberwachung metallischer Werkstoffe, sponsored by Deutsche Gesellschaft fur Metallkunde, Munich, Germany (Apr. 1974).Google Scholar

Copyright information

© Society for Experimental Mechanics, Inc. 1977

Authors and Affiliations

  • D. O. Harris
    • 1
  • R. L. Bell
    • 2
  1. 1.Science Applications, Inc.Palo Alto
  2. 2.Celesco IndustriesCanoga Park

Personalised recommendations