Non-destructive testing is a wide group of methods used to detect discontinuities that cannot be identified by the naked eye or those in the surface of the material without damaging the material. In these tests, defects such as corrosion, cracks, abrasion, decrease in wall thickness or gaps in internal structures are identified in ferritic and austenitic steels, aluminum alloys, nickel and copper alloys, and titanium alloys during production or usage.
We provide services of non-destructive testing and results evaluation for industrial and welded products and applications according to ISO 9712 (EN 473) and ASNT CP-189-2011 standards with our Level II and Level III qualified expert staff.
NON-DESTRUCTIVE TESTING METHODS
Magnetic Particle Testing is a test method used to detect surface defects. When the testing surface is magnetized, any surface discontinuity in the material causes the magnetic flux to leak. Then ferromagnetic (magnetizable) particles are applied to the part, and these particles are pulled by the stray flux and collected on the discontinuities. In this way discontinuities and defects can be located.
This method can be applied on all ferromagnetic materials.
The roughness of the inspection surface can negatively affect the error detection process.
If there is paint, coating or residue on the inspection surface, the thickness of these directly affects the test result.
Penetrant testing is another method used to detect surface defects.
Liquid penetrant tests check for material flaws open to the surface.
It is a method to reveal discontinuities by drawing out the penetrant liquid, penetrated into the open discontinituities with capillarity effect, to the inspection surface with the help of the developer material.
Flaws under the surface or disconnected from the surface cannot be detected with this method.
Only smooth and clean surfaces can be inspected. Insufficient and inappropriate pre-cleaning can cause incorrect evaluations and errors.
Ultrasonic Thickness Measurement Examination is a non-destructive testing method of the local thickness of a solid element (typically made of metal) basing the test on the time taken by the ultrasound wave to return to the surface.
As shown that ultrasonic waves travel at constant speed with only small changes through individual alloys, the test is usually carried out on metals and is often used to track metal thickness or welding quality in industrial environments such as marine, aviation and automotive.
Main advantages of the ultrasonic thickness measurement method:
- It is a non-destructive method.
- It is relatively cheap compared to other methods and can be set up easily.
- It does not require access to both sides of the equipment to be tested.
- Sensitivity value can be decreased using standard timing methods.
It is a testing method carried out with the naked eye.
It is a method of inspection with or without optical aids of defects on the material surface, of structural defects, and of negative parameters affecting the surface quality.
Though visual testing is regarded as a very simple method, it requires some examination conditions.
Generally it must be applied before the other non-destructive testing methods are applied.
It can be applied on all metallic or non-metallic materials.
Generally, surface cleaning is not required as preparation for inspection. The surface should be such that the expected flaws can be detected easily. The inspection should be carried out under adequate lighting and at suitable viewing angles.
Radiographic testing or x-ray is the application of electromagnetic radiation on the specimen to detect hidden flaws.
High-energy electromagnetic waves penetrate the material. The radiation penetrating the material affects the radiation-sensitive film placed on the other side of the material. When developed, this film reveals the image of the inner part of the material through which the beam passes. The darker areas on the image are evaluated as the indicators of discontinuities.
This method can be used to detect the expected volumetric and surface flaws in all metallic or non-metallic materials.
The thickness of the test material cannot exceed certain values depending on the type of the radiation source used.
It can be applied on all kinds of materials except thickness limitation.
Both surfaces of the test material must be accessible.
Products to be used for examination are far more expensive than in other methods.
Careful work on radiation protection is required.
Eddy-Current testing is a suitable method for identfying surface and near-surface defects.
When an energy coil is brought close to the surface of a metal piece, the variable magnetic field of the coil creates eddy currents on the material. These currents tend to magnetize against the original magnetic field. The impedance of the coil near the sample is impacted by the presence of induction currents induced in the sample.
When a coil of conductive wire is excited with an alternating electrical current. This wire coil produces an alternating magnetic field around itself in the direction ascertained by the right-hand rule. The magnetic field oscillates at the same frequency as the current running through the coil. When the coil approaches a conductive material, currents opposed to the ones in the coil are induced in the material — eddy currents.
When the eddy currents in the sample deteriorate due to defects or material variations, the coil impedance changes. This change is measured, and displayed as indicating the defect or the material variation.
It can be applied on all metallic and alloy materials with electrical conductivity.
With eddy current testing, it is also possible to classify materials based on properties such as electrical conductivity or magnetic permeability. In addition, it is also possible to measure coating thickness or thickness of thin metal sheets.