JNTU B.Tech IV NON-DESTRUCTIVE TESTING Previous Question Paper (February/March - 2022 - R18)

Borescopes are optical instruments used for remote visual inspection of internal surfaces. They are categorized based on their construction and flexibility:

• Rigid Borescopes: Consist of a solid metal tube containing a series of relay lenses. They provide high-resolution, clear images for straight-line access paths.
• Flexible Borescopes (Fiberscopes): Utilize coherent fiber-optic bundles to transmit images. They are ideal for navigating complex, curved, or multi-bend internal geometries.
• Video Borescopes: Incorporate a miniature CCD or CMOS sensor at the distal tip. These convert optical images into digital signals, allowing for real-time viewing on a monitor, image capture, and digital measurement.

A typical sketch would show the objective lens at the tip, the transmission medium (lenses, fibers, or electrical cables), and the eyepiece or display unit at the proximal end.

Acoustic Emission (AE) is a passive NDT technique that detects transient elastic waves generated by the rapid release of energy from localized sources within a material, such as crack growth, plastic deformation, or corrosion.

The working principle involves:

1. Sensors: Piezoelectric transducers are attached to the surface of the component to detect stress waves.
2. Signal Conditioning: The detected mechanical vibrations are converted into electrical signals, which are then amplified and filtered to remove background noise.
3. Data Acquisition: The processed signals are sent to an AE system that records parameters like hit count, amplitude, energy, and duration.
4. Analysis: The location of the defect is determined through triangulation based on the time-of-arrival difference between multiple sensors.

A schematic sketch would depict the test specimen under load, sensors mounted on the surface, a pre-amplifier, the main processing unit, and a display showing the event waveforms and source location mapping.