What Is Non-destructive Testing?
Non-destructive testing (NDT) also known as
‘positive testing’.
As its name implies, non-destructive testing means testing of materials without
destroying them.
It is a kind of a testing approach in which the testing is performed to cover only the positive cases to confirm that the software behaves properly and returns the expected results as per the product requirement. It is one of the best courses to do if you want to get a high profile job in abroad or India in oil & gas, petroleum, aircraft, refinery, etc. It is commonly used in the area of aerospace engineering, mechanical engineering, civil engineering, electrical engineering, system engineering, and medicines.
EXAMPLES OF DESTRUCTIVE TEST:
- Tensile test
- Compression test
- Shear test
- Hardness test
- Impact test
- Fatigue test
- Bending test
- Creep test
- Torsion test
- Chemical test, etc.
IMPORTANCE OD NDT:
- Save both time and money in product evaluation.
- It can be used to detect flaws in an in-process machine part.
- No requirements for special equipment
BASIC ELEMENTS OF NDT:
- Source
- Modification
- Detection
- Indication
- Interpretation
SOME OF THE METHODS OF NDT:
Advantages:
- Generally fast test time
- Can be automated
- Good at finding dimensional flaws or surface blemishes
- Portable
Disadvantages:
- Reference standards required
- May require multiple cameras and viewing angles for automated
systems
- Subject to operator interpretation if not automated
- Dye Penetrant Testing (DPT):
Advantages:
- Non-destructive
testing of concrete helps in detecting the
surface cracks or defects.
- One of the most widely used NDT testing methods.
- It is used for surface detection of casting, weld elements.
- It is also called liquid penetrant testing.
Disadvantages:
- The defect must be open to the surface
- Parts must be cleaned before and after testing
- Surface films, such as coatings, scale, and smeared metal may visually mask defects
- Magnetic Particle Testing (MPT):
Advantages:
- Economically and easy to
perform.
- Portable for field testing.
- Fast for production testing.
- Relatively simple method.
- Low cost.
Disadvantages:
·
Ferromagnetic materials only
·
Alignment of the magnetic field
is critical
·
Demagnetization required after
the test
·
Surface coatings can mask
defects
·
Pre- and post-cleaning
necessary
·
Messy
·
Subjective: dependent on
operator interpretation
·
Difficult to automate
Advantages
·
It is an electronic device that
can produce high-frequency ultrasonic energy.
·
It introduced and propagates
through the materials in the form of waves.
·
Portable.
·
Instant test results don’t take
too much time.
·
It is fully capable of being
automated.
· A probe is used.
·
Immediate results.
Disadvantages:
- Couplant required
- Complex or small parts may be difficult to check
- The defect may be missed if not in the path of the ultrasonic
signal
- Reference standards required
- Trained operators for manual inspections
- Special probes
- Surface condition
- Eddy Current Testing (ECT):
Advantages:
- Equipment is very portable.
- Detect surface and near-surface
defects.
- Deep penetration is limited.
- High speed.
- Low cost.
Disadvantages:
- Conductive material only.
- Shallow depth of penetration.
- Surface roughness may affect test quality.
- Radiography Testing (RT):
Advantages:
·
It is having a fast method of
testing.
·
It is the same as medical
radiography, which only differs in wavelength.
·
Lessor no manual work.
Disadvantages:
- Radiation hazard.
- Expensive.
- Trained operators needed.
- Linear defects may be missed.
- Depth of defect not indicated.
MAIN OBJECTIVE OF NDT:
- To detect internal or surface flaws.
- To measure the dimensions of the specimen.
- To determine material structure or chemistry.
- To evaluate the material’s physical or mechanical properties.
ADVANTAGES OF NDT:
- The equipment is easy to handle.
- The data is more recordable and more repeatable.
- Methods are quick and accurate.
- Defects can be detected without damaging the components.
- It can be done on small instances of the code to confirm it is
ready to be merged into the main code, thus reducing the chances of it
breaking the code.
- No extra tools or equipment are required to do NDT.
- Less Skill and non-expensive.
- It is used for finding out the defects.
- The Specimen is not damaged during testing.
- It provides reliability.
- Harmless to humans.
DISADVANTAGES OF NDT:
- Purchase costs may be preventative, so renting can be a
preferable option.
- Due to load applications, the material gets damaged. Sometimes
there might be a lack of depth sizing
- On some non-destructive test methods, only relatively heavy
surfaces can be inspected.
- Some test methods require electricity.
- Some can also be affected by variations in magnetic
permeability.
- Some tests are only effective in conductive materials.
- The methods take time and rarely be finished in less than 30
minutes.
- Components needing to be cleaned before and after inspection.
APPLICATIONS OF NDT
- To ensure product reliability
- To control the manufacturing process
- To lower production cost.
- Inspection of raw products i.e. forgings, castings, extrusions,
etc.
WHERE TO USE NDT:
- In product evaluation.
- For troubleshooting
- For identifying areas of wear
- For assuring the safety and reliability of structures and
component
- To find flaws or irregularities both on and under the surface
of materials.
NDT is used in many industries, including:
- Engineering
- Air
- Space
- Rail
- Motor vehicles
- Utilities
- Power and energy companies
- Construction
CONCLUSION:
Non Destructive Testing provides
cost-effective and reliable analysis under realistic conditions. Each NDT Testing services has certain
capabilities and limitations and often more than one technique is used to cover
various parts. Increasing the availability of robotic scanners improve the
speed of testing large surfaces, hence minimizing the testing time.
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