NDT is the acronym for Non-Destructive Testing. The method of testing or inspection of a component or material to examine or detect the presence of any defect without damaging or destroying is called non-destructive testing.
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It is defined as the process of testing the material without causing any damage or reducing the service life of the engineering materials.
Defects are of two types; external defects and internal defects.
| External defects | Internal defects | |
| (i) | Surface damage | No surface damage |
| (ii) | Stress corrosion | Porosity in casting |
| (iii) | Blow holes in castings | Over stressed parts |
| (iv) | Hardening crack | Pipe or axial segregation |
NDT plays a key role in the fields, namely aircraft, motor vehicles, pipelines, trains, power stations etc. One can successfully apply the NDT techniques to monitor integrity of the components or structure throughout their life.
Objective of NDT methods
Generally, NDT identifies the presence of imperfections and defects during manufacturing,
- In order to provide a detailed idea about a structure or material.
- In order to detect any physical defects in a material or structure that presents during in service, and
- In order to reduce the costs.
- In order to provide safety and reliability.
Types of NDT methods
The defects or flaws in the material can be detected by various NDT methods as follows:
| 1. Visual inspection | 2. Liquid penetrant method |
| 3. Ultrasonic inspection | 4. Radiographic method |
| 5. Eddy current testing | 6. Magnetic particle testing |
| 7. Thermography |
Table Comparison of destructive and non-destructive testing
| S.No | Destructive testing | Non-destructive testing |
| 1. | This method is applied only to a sample. | This method is applied directly on production items. |
| 2. | Tested parts are damaged during testing. | Tested parts are not damaged during testing. |
| 3. | Different tests cannot be performed on the same item. | Different tests can be performed on the same item. |
| 4. | Preparation of testing specimen is required. | No specimen preparation is often required. |
| 5 | It cannot be performed even to a single part that is in service. | Can be performed on various parts that are in service. |
| 6. | Time consumption is high | Time consumption is low. |
| 7. | Equipments and labour costs are high. | Labour costs are low. |
Among the different available NDT methods, we are going to discuss the ultrasonic testing in detail.
| Read More Topics |
| Photonics introduction and properties of laser |
| Ultrasonic testing methods |
| Piezo – Electric oscillator method |
