Lecture
Non-destructive testing (NDT) is the control of reliability of the main operating properties and parameters of an object or its individual elements/units, which does not require taking the object out of service or dismantling it.
There is also the concept of destructive testing (for example, crash tests of automobiles).
The main methods of non-destructive testing are :
| Type of inspection | By the nature of interaction of physical fields with the object under inspection | By primary informative parameter | By method of obtaining primary information |
|---|---|---|---|
| Magnetic | Magnetic |
Coercive force, Magnetization, Residual induction, Magnetic permeability, Barkhausen effect intensity |
Inductive, Flux-gate, Magnetographic, Ponderomotive, Magnetoresistive |
| Electrical |
Electrical, Triboelectric, Thermoelectric, |
Electropotential, Electrocapacitive |
Electrostatic powder, Electroparametric, Electric-spark, Recombination-radiation, Exoelectronic emission, Noise, Contact-potential-difference |
| Eddy-current |
Transmitted radiation, Reflected radiation |
Amplitude, Phase, Frequency, Spectral, Multi-frequency |
Transformer, Parametric |
| Radio-wave |
Transmitted radiation, Reflected radiation, Scattered radiation, Resonance |
Amplitude, Phase, Frequency, Time, Polarization, Geometric |
Detector (diode), Bolometric, Thermistor, Interference, Holographic, Liquid crystal, Thermal paper, Thermoluminophor, Photo-controlled semiconductor wafer, Calorimetric |
| Thermal |
Thermal contact, Convective, Intrinsic radiation, |
Thermometric, Heat-metric |
Pyrometric, Liquid crystal, Thermal paint, Thermal paper, Thermoluminophor, Temperature-dependent parameters, Optical, Interference, Calorimetric |
| Optical |
Transmitted radiation, Reflected radiation, Scattered radiation, Induced radiation |
Amplitude, Phase, Frequency, Time, Polarization, Geometric, Spectral |
Interference, Nephelometric, Holographic, Refractometric, Reflectometric, Visual-optical, |
| Radiation |
Transmitted radiation, Scattered radiation, Activation analysis, Characteristic radiation, Autoemission |
Energy flux density, Spectral |
Scintillation, Ionization, Secondary electrons, Radiographic, Radioscopic |
| Acoustic |
Transmitted radiation, Reflected radiation (echo method), Resonance, Impedance, Free oscillations, Acoustic-emission |
Amplitude, Phase, Time, Frequency, Spectral |
Piezoelectric, Electromagnetic-acoustic, Microphone, Powder |
| Penetrant | Molecular |
Liquid, Gas |
Brightness (achromatic), Color (chromatic), Fluorescent, Fluorescent-color, Filtering-particle, Mass-spectrometric, Bubble, Manometric, Halogen |
| Vibroacoustic | Mechanical oscillation — the motion of a point or mechanical system in which the scalar quantities characterizing it oscillate | Statistical parameters of the oscillatory process (mechanical oscillations) | Piezoelectric. Electromagnetic-acoustic |
Non-destructive testing (Nondestructive testing (NDT)) is also called reliability evaluation by non-destructive methods (nondestructive evaluation (NDE)) or inspection of a product without destroying it (nondestructive inspection (NDI)). NDT is especially important in the creation and operation of critical products, components, and structures. For detecting various flaws, such as corrosion, rust, and cracking.
International practice uses abbreviated designations for the types of non-destructive testing (AWS), given in the table:
| No. | Type of inspection | Symbol |
|---|---|---|
| 1 | Inspection using acoustic emission | AET |
| 2 | Electromagnetic inspection | ET |
| 3 | Leak testing | LT |
| 4 | Magnetic-particle inspection | MT |
| 5 | Neutron radiography | NRT |
| 6 | Inspection using penetrating liquid | PT |
| 7 | Radiographic inspection | RT |
| 8 | Ultrasonic inspection | UT |
| 9 | Visual inspection | VT |
| 10 | Vibroacoustic | VA |
The indicated symbols are marked on drawings.
The purpose of using non-destructive testing in industry is the reliable detection of dangerous defects. Therefore, the choice of specific NDT methods is determined by the effectiveness of detecting such defects. In practice, ultrasonic inspection has become the most widespread, as it has high sensitivity, mobility, and environmental friendliness, as well as radiation inspection, which successfully detects dangerous defects and objectively records the results obtained .
Depending on the tasks at hand, other inspection methods are also used. For example, capillary methods are used to search for surface defects, and leak testing for detecting through-defects.
Electrical, magnetoelectric, magnetic, and eddy-current methods make it possible to inspect the properties of conductive media, as a rule, on the surface and in the subsurface layer. Non-destructive testing is carried out more completely by a combination of several methods .
The introduction of a quality control system increases the price of products. According to expert estimates, in developed countries the cost of quality control in the aerospace and defense industries, as well as in nuclear power, amounts to 12-18% of the cost of production.
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