BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI - Universitatea ...

Bul. Inst. Polit. Iaşi, t. LVI (LX), f. 2, 2010 181
those areas which are prone to failure. It can be stated that the method enables
the so-called "defect management", the monitoring of the infrared radiation
emitted by a technical system during normal operation often being the only
imaging method that enables the actual visualization of the notions of "fault"
and "inclination to failure".
Thermography is very often the only quick on-site investigation of a
facility. The areas which are prone to failure can be observed through a mere
scanning of the frontage of the device.
2.1.2. Ultrasonic technology. Ultrasound is applied differently, depending
on the nature, geometry and destination of the product, taking into accounts the
technical performance of the Probes Flaw system. Steel products are the ones
which are most commonly examined by means of the ultrasound technique.
Ultrasonic control can be differentiated and customized according to the
methods specific to steel products: metal, forgings, castings, welded structures
and products made of austenitic steel.
The ultrasound check reveals all the types of internal defects of welded
joints. The ultrasonic method can be used to determine wall thickness and the
number of deposited layers. This technology is applicable to all metals and
nonmetallic materials. Having a great penetrating force, the ultrasound enables
the verification of large sections. The application is only limited by the rough
structures which are highly heterogeneous. The devices are lightweight,
portable and autonomous, and the technology will ensure good results even in
on-site working conditions. The verification techniques, particularly the
immersion control, lend themselves to mechanization and automation.
The result is safe and immediate and it can accurately predict the location,
size and depth of the defects. From an economic standpoint, the ultrasound
method is much cheaper and more productive than the radiation technique in
those cases where the number of defects exceeds a certain limit [14].
2.1.3. X-ray technology. X-rays can penetrate a large number of different
materials, including composites. Usually, the images are obtained as shadow
variations along the X-ray propagation. Under normal operation conditions, the
X-rays are not able to reveal the cracks which have a parallel orientation with
respect to the rays.
The energy requirement is low and the safety prerequisites can be fulfilled
from a remote position. The X-ray sources can be small, air-cooled and easily
implemented for various applications. This method is able to detect the lack of
binder between the metal, as well as cracks and holes in the metal. Some
sources enable the detection of defects at less than 10 micrometres. This method
can be used during real-time inspection for quality control or shortly after the
blade of the wind turbine is set in motion. [13].