NON-DESTRUCTIVE TESTS

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• Q1: What is a Non-Destructive Test for materials?
  Ans: A Non-Destructive Test (NDT) is a method of inspecting or evaluating materials without causing damage, so the material can still be used after testing.
• Q2: Name the types of Non-Destructive Tests for materials.
  Ans: The main types of NDT include:

  • ➔ Radiography (X-ray or Gamma ray)
  • ➔ Ultrasonic Testing
  • ➔ Magnetic Particle Inspection
  • ➔ Liquid Penetrant Inspection
  • ➔ Eddy Current Testing
  • ➔ Infrared Thermography
  • ➔ Visual Inspection (Boroscope)
• Q3: What is Radography?
  Ans: Radiography is a NDT method using X-rays or Gamma rays to detect internal defects in a material by producing an image on a film or detector.
• Q4: What is Magnetic Particle Inspection?
  Ans: Magnetic Particle Inspection (MPI) detects surface and near-surface cracks in ferromagnetic materials by magnetizing the part and applying magnetic particles that gather at defects.
• Q5: What is Liquid Penetrate Inspection?
  Ans: Liquid Penetrant Inspection (LPI) is a method where a colored or fluorescent liquid penetrates surface cracks, and excess liquid is removed to reveal defects under UV or visible light.
• Q6: What is Ultrasonic Inspection?
  Ans: Ultrasonic Inspection uses high-frequency sound waves to detect internal flaws or thickness variations in materials.
• Q7: What is Eddy Current Inspection?
  Ans: Eddy Current Inspection detects surface and near-surface defects in conductive materials using induced electric currents and monitoring changes in electromagnetic response.
• Q8: State the benefits of Non-Destructive Tests.
  Ans: Benefits of NDT include:

  • ➔ Detect defects without destroying the part
  • ➔ Saves cost and material
  • ➔ Allows inspection of in-service components
  • ➔ Provides quick and reliable results
• Q9: What is a Pressure Test or Pneumatic Hydraulic Test?
  Ans: A pressure test checks the strength and leak-tightness of pressure vessels, pipes, or tanks by applying water (hydraulic) or air (pneumatic) pressure.
• Q10: What is Hydraulic Testing?
  Ans: Hydraulic testing is a method of applying water or liquid pressure to a component to ensure it can safely withstand operating pressure without leaking or bursting.
• Q11: What is Pneumatic Testing?
  Ans: Pneumatic testing uses compressed air or gas to test components for leaks and pressure resistance.
• Q12: What is a Hammer Test?
  Ans: Hammer test is a simple method to detect cracks, voids, or delaminations in materials by tapping with a hammer and listening to the sound changes.
• Q13: What is the X-ray method of Testing?
  Ans: X-ray testing is a radiographic NDT method to detect internal defects by passing X-rays through the material and capturing the image on film or a digital detector.
• Q14: State the basic principle of X-ray Test.
  Ans: Principle: X-rays penetrate the material; defects absorb less radiation, showing lighter areas on the radiograph, indicating cracks, voids, or inclusions.
• Q15: State four advantages of X-ray Test.
  Ans: Advantages:

  • ➔ Detects internal defects
  • ➔ Provides a permanent record (radiograph)
  • ➔ High accuracy and reliability
  • ➔ Can inspect complex shapes
• Q16: State four disadvantages of X-ray Test.
  Ans: Disadvantages:

  • ➔ Expensive equipment and operation
  • ➔ Requires skilled operator
  • ➔ Health hazards due to radiation
  • ➔ Limited thickness penetration for dense materials
• Q17: State four safety measures adapted in X-ray Test.
  Ans: Safety measures:

  • ➔ Use lead shielding around the source
  • ➔ Keep a safe distance from X-ray beam
  • ➔ Use personal dosimeters
  • ➔ Limit exposure time
• Q18: What is a Boroscope?
  Ans: A boroscope is an optical instrument used to visually inspect internal areas of components that are difficult to access.
• Q19: State four advantages of using a Boroscope.
  Ans: Advantages:

  • ➔ Non-destructive inspection
  • ➔ Accesses hidden or confined spaces
  • ➔ Immediate visual feedback
  • ➔ Portable and easy to use
• Q20: What is Infrared Thermography?
  Ans: Infrared thermography is a NDT method using thermal cameras to detect surface temperature variations caused by defects like cracks, voids, or corrosion.
• Q21: What is the Gamma Ray Method of Testing?
  Ans: Gamma ray testing is a radiographic NDT method using gamma radiation from radioactive isotopes to detect internal defects in materials.
• Q22: State the basic principle of the Gamma Ray Method.
  Ans: Principle: Gamma rays penetrate the material; areas with defects absorb less radiation, creating a shadow or image that shows cracks or voids.
• Q23: State four advantages of Gamma Ray Method.
  Ans: Advantages:

  • ➔ Can inspect thick sections
  • ➔ Portable sources available
  • ➔ Permanent record on film
  • ➔ Detects internal defects effectively
• Q24: State four disadvantages of Gamma Ray Method.
  Ans: Disadvantages:

  • ➔ Radioactive hazard
  • ➔ Expensive
  • ➔ Requires skilled personnel
  • ➔ Limited exposure time and safety protocols needed
• Q25: Name the equipment used in the Gamma Ray Method.
  Ans: Equipment:

  • ➔ Gamma radiation source (e.g., Cobalt-60)
  • ➔ Radiation shield and collimator
  • ➔ Film or digital detector
  • ➔ Exposure control and safety devices
• Q26: State four safety measure for Gamma Ray Method.
  Ans: Safety measures:

  • ➔ Use lead or concrete shielding
  • ➔ Limit exposure time
  • ➔ Maintain safe distance from source
  • ➔ Use personal dosimeters and follow safety protocols
• Q27: Compare X-rays and Gamma Rays.
  Ans: Comparison:

  • ➔ X-rays are produced by X-ray machines; Gamma rays are emitted by radioactive isotopes.
  • ➔ Gamma rays have higher penetration for thicker materials.
  • ➔ X-rays can be switched on/off; Gamma rays are always active and need shielding.
  • ➔ Both are used for internal defect detection in radiography.
• Q28: State four properties of Gamma Rays.
  Ans: Properties of Gamma Rays:

  • ➔ Electromagnetic radiation
  • ➔ High energy and penetration
  • ➔ Emitted by radioactive decay
  • ➔ Cannot be turned off; continuous emission
• Q29: State four properties of X-Rays.
  Ans: Properties of X-Rays:

  • ➔ Electromagnetic radiation
  • ➔ Produced electrically in X-ray tube
  • ➔ Can be switched on and off
  • ➔ Medium to high penetration power depending on voltage
• Q30: What is the Magnetic Particle Method of Testing?
  Ans: Magnetic Particle Testing (MPT) is a method to detect surface and near-surface cracks in ferromagnetic materials using a magnetic field and magnetic particles.
• Q31: Name the equipment used for the Magnetic Particle Method.
  Ans: Equipment includes:

  • ➔ Magnetic yoke or coil for magnetization
  • ➔ Magnetic particles (dry or suspended in liquid)
  • ➔ UV light or white light for observation
  • ➔ Demagnetization equipment
• Q32: State the basic principle of the Magnetic Particle Inspection Method.
  Ans: Principle: Magnetic field is applied to a ferromagnetic material; defects distort the field and attract magnetic particles, revealing surface or near-surface cracks.
• Q33: What is DeMagnetisation?
  Ans: Demagnetisation is the process of removing residual magnetism from a component after magnetic particle testing.
• Q34: Briefly discuss the procedure of Crack Detection by Magnetic Particle Inspection.
  Ans: Procedure:

  • ➔ Clean the surface of the material
  • ➔ Magnetize the component using a yoke or coil
  • ➔ Apply magnetic particles on the surface
  • ➔ Inspect under UV or white light for indications of cracks
  • ➔ Demagnetize the part after inspection
• Q35: What is Eddy Current?
  Ans: Eddy current testing uses induced electrical currents in a conductive material to detect surface and near-surface defects by monitoring changes in current flow and impedance.