Standard Article

Ultrasonic Methods

Physical Monitoring Principles

Passive and Active Measurements with Data Analysis Approaches for Load and Damage Identification

  1. Wolfgang Hillger

Published Online: 15 SEP 2009

DOI: 10.1002/9780470061626.shm015

Encyclopedia of Structural Health Monitoring

Encyclopedia of Structural Health Monitoring

How to Cite

Hillger, W. 2009. Ultrasonic Methods. Encyclopedia of Structural Health Monitoring. .

Author Information

  1. German Aerospace Center (DLR), Braunschweig, Germany

Publication History

  1. Published Online: 15 SEP 2009


Ultrasonic testing (UT) is a well-established nondestructive technique. It is based on ultrasonic waves in a frequency range usually from 0.5 to 20 MHz. UT provides a quality control, determination of material properties, and a flaw detection with location in all three dimensions. Using echo technique, only a one-sided access of the test component is necessary. A flaw detector provides instantaneous results. Automated systems deliver images like C-scans (top view) and B-scans (view in cross-section direction) of hidden defects. In this article, the physical principles of UT are explained and the parts of an imaging system are described.


  • nondestructive testing;
  • ultrasonic testing (UT);
  • acoustic waves;
  • reflection scattering;
  • transducers;
  • defect detection;
  • ultrasonic imaging;
  • visualization of wave propagation;
  • air-coupled ultrasonic testing