Ultrasonic Test ( UT )

It is used in the detection of planar and volumetric faults as well as crack type discontinuities in metallic materials.

High-frequency sound waves are produced by piezoelectric crystals in a piece called a “probe”.

As a general principle; High-frequency sound waves sent into the material are reflected if they hit an obstacle. Depending on the angle of impact, the receiver may or may not come to the probe. The location of the error can be determined by the coordinates of the reflected signal reaching the receiving probe on the screen of the ultrasonic inspection device. An interpretation of the size of the reflector is made by looking at the height of the echo.

Evaluation becomes difficult if the sound velocity and sound attenuation characteristics of the inspection piece show strong regional variations. In cases where the coarse grain structure and sound attenuation are too much, it is sometimes difficult to perform the examination.

Magnetic Particle Test (MT)

It is an inspection method used to detect surface defects. Ferromagnetic can be applied to all parts. Not applicable to ferro-magnetic materials. If a magnetic flux is applied to the inspection surface, leakage flux occurs on the discontinuities on the surface. In the meantime, if ferromagnetic powders are sprinkled on the inspection surface; As these dusts are attracted by stray fluxes and collect on the discontinuities, it is possible to detect the errors.

If there is paint blasting on the inspection surface, they directly affect the inspection result depending on the thickness. Very high magnetizing currents are required for large parts. As a result of the inspection, final cleaning is required for magnetization removal.

Hardness Test (HT)

Hardness is not a relative measure, but is defined as resistance to friction, scratching, cutting and plastic deformation. It is the resistance of the material against plastic deformation.

Hardness measurement generally consists of measuring the resistance of the material when a conical spherical standard tip is dipped into the material. A properly selected hard tip will leave a mark on the material when dipped into the material under the applied load. The hardness of the material is inversely proportional to the size of this scar.

In addition, Hardness gives information about the machinability of the material. There is an inverse proportion between hardness and traceability. Hard materials are difficult to machine.

Rocwell, Brinell and Vikers hardness tests are generally used in the metal industry.

These tests are done by measuring the immersion depth of a sphere or cone that does not deform under a given load. There are different test methods for different materials, and their results differ. Therefore, when talking about the hardness of a material, the test method must also be determined.

Vacuum Test

Vacuum testing is a method used to detect leaks in welded joints. In the vacuum test, the pressure difference between the inner and outer surfaces of the tested area is used. Its main areas of use are piping systems, pressure tanks and storage tanks.

There are different types of vacuum test methods according to the region to be applied. The vacuum test is suitable for checking lap welds, butt welds and corner welds.

Visual Control (VI)

It can be applied on all metallic or non-metallic materials.

It is usually a control method that should be done before applying another non-destructive testing method. It is the examination of the parameters affecting the quality such as discontinuity, structural defects, surface condition on the surface of a product, with or without the use of an optical aid (magnifying glass).

Depending on the accessibility of the examination surface, auxiliary devices such as endoscopes are used when necessary. The examination is made under sufficient light and with appropriate viewing angles.

Radiographic Test (RT)

It is used to detect expected volumetric and surface defects in all metallic and non-metallic materials.

High-energy electromagnetic waves (radiation) can penetrate many materials. Radiation penetrating a certain material may affect the radiation sensitive films placed on the other side of the material. After these films are subjected to the process of processing; The image of the interior of the material through which the radiation passes appears. This appearance is caused by voids in the material or changes in thickness/density. This view of the inside of the material is called radiography. If a detector is placed on the back of the material instead of a film and the radiation passing through the material is transferred to a monitor, this technique is also defined as radioscopy.

The radiation sources generally used in the industry are X-ray tubes and these are generally between 50 kV and 350 kV. Gamma radiation sources are IR192,Co60. In addition to these, Se75, Yb169 and Tm170 isotope energies are also used in the field of radiography.

In order for the examination to give healthy and reliable results; must be done according to standards. It is necessary to reach both surfaces of the inspection piece. It can be applied to all kinds of materials except the thickness limitation.

Penetrant Test (PT )

Penetrant test is used to detect surface defects. It is possible to detect expected surface defects on all metallic and non-metallic materials.

Errors that are not exposed to the surface and whose surface clarity has been lost for any reason cannot be detected with this method. In the penetrant test, the defects must be exposed to the surface. If the surface cleaning is not done properly, it directly affects the result negatively.

Forged steels, steel pipes, bridges, buildings, steel castings, high-low pressure casting molds and precision castings are a few examples of materials that can be controlled by this method.

Eddy Current Test ( ET )

When a variable current (AC) is passed through a winding, a magnetic field is created around this winding. When this winding is brought close to the surface of an electrically conductive material, the variable magnetic field of the winding creates eddy currents on the material surface. These currents flow in a closed circuit and are called Eddy currents. Eddy currents also create their own magnetic fields. By measuring this created secondary magnetic field, surface defects can be found, and parameters such as conductivity and permeability of the material can be determined.

Scope of Application

This method is used to detect surface and subsurface discontinuities in all electrically conductive materials (copper, aluminum, etc.). With the eddy current inspection method, it is also possible to classify materials based on properties such as electrical conductivity or magnetic permeability. Apart from these, it is also possible to measure the thickness of the coating or the thickness of thin metal sheets.

Limitations

Not applicable to electrically non-conductive materials. Inspection of ferromagnetic materials requires special procedures. The depth of penetration is limited. Since the inspection result depends on the scanning direction, some errors may not be observed at the end of the scanning in unsuitable directions. It is more dependent on the user’s education and experience than other methods. Surface conditions greatly affect the inspection result. Special reference standard blocks are needed for the assembly.

Application

If crack-type symptoms are sought on the inspection surface, scanning is usually done with probes called differential probes, since they are more sensitive, but it is possible to detect crack-type errors with absolute probes. Absolut probes are mostly used for material characterization and coating thickness measurement. The “lift-off” effect is used for thickness measurement. For this, the device must first be calibrated. The thicknesses to be used for calibration should be chosen close to the thickness to be measured, with a slightly larger value and a slightly smaller value. If the magnetic permeability or electrical conductivity of the inspection piece is to be characterized by measurement, absolute probes are used again and the device values ​​should be calibrated with the help of known reference blocks before the measurement.