The acoustic emission (AE) is the effect of
propagation of elastic vibrations (acoustic waves) generated by a
sudden deformation of strained material.
 |
| 1 – AE transducer (receiver 1);
2 – AE transducer (receiver 2);
3 – industrial
computer-based central collection and processing unit;
4 – test object;
t1 – time of
signal arrival at the first receiver;
t2 – time of signal arrival at the first receiver.
The system defines the difference of arrival time Т (Т= t2 - t1) at the diversed receivers by the registered signal arrival
time ti at the 1st receiver (sensor). Thereafter the program computes
the source (defect) coordinates by the known velocity of sound in
material and known coordinates of receivers. The layouts of sensors
can be different. |
Fluctuations propagate from the emission source to a sensor (sensor
s), where they are converted into electrical signals. AE devices record
these signals and display the data as oscillograms, locations, digital
indications, serving as the basis for the operator in estimating the
state and behavior of the stressed material structure, in detecting and
defining the defect site.
The AE-testing method is based on detection, registration and
analysis of elastic vibrations occurring under plastic deformation of
solid mediums, defects growth (cracks, microcracks, exfoliation,
corrosion, hydrogen embrittlement etc.), friction, leakage (passage of
liquid and gaseous media via the through defects).
ADVANTAGES OVER TRADITIONAL NDT METHODS
1. The method integrality which lies in the fact that using one or
several sensors mounted stationary on an object surface one can control
the object as a whole (100% testing). This property is especially
useful under examination of hard-to-reach (out-of-reach) surfaces of
the test object.
2. The AE method does not require a careful preparation of the test
object surfaces as contrasted to the scanning NDT methods. Therefore,
the method execution and its results do not depend on surface condition
and quality of its treatment. An insulation covering (if any) should
be removed at the points of sensor installation only.
3. Detection and registration of growing defects that allows
classifying defects not by dimensions (or by any other indirect
features – by defect form, position, orientation), but also by the
degree of their danger (influence on strength) for the test object.
4. The high efficiency many times exceeding the efficiency of
traditional NDT methods, such as ultrasonic, radiographic, eddy
current, magnetic methods etc.
5. The method remotabiity is a possibility to make testing, when the
operator is at the significant distance from the test object. This
property allows its effective use for testing (monitoring) critical
large-size structures, lengthy or extrahazardous facilities not taking
them from service and without detriment to the personnel.
6. The possible tracking of various processes and real-time
evaluation of object technical condition that permits preventing an
emergency destruction of the test object.
7. Maximum efficiency\cost ratio.
FIELDS OF APPLICATION
- Oil refinery and chemical industry;
- Tube-rolling and metallurgical enterprises;
- Thermal power and nuclear power engineering;
- Railway transport;
- Hoisting structures;
- Bridge constructions;
- Aerospace engineering;
- Concrete and reinforced concrete constructions.
The AE method makes possible receiving huge files of data, regulating
and extending the operation cycle of critical industrial objects
operatively and with minimum expenses; it helps in forecasting the
probability of emergency failures and catastrophes. The AE method also
gives extended opportunities in researching different properties of
materials, substances, and designs. At present the development and
reliable operation of many critical technical objects are impossible
without application of the acoustic control and monitoring.
