It is popular abbreviation of "Non-Destructive Testing". NDT is a branch of "Material Testing" which does not affect the future usefulness (serviceability) of the object after the examination is over. NDT provides an excellent balance between Quality Control and cost effectiveness.

NDT includes the following popular methods.

• Ultrasonic
• Radiography
• Magnetic Particle
• Dye-Particle
• Eddy-Current
• Acoustic Emission etc.

NDT is used to

• Detect internal or external imperfections.
• Determine structure, composition, or material properties
• Measure Geometric characteristics.

NDT should be used in the phases of a product's design and manufacture, including material selection, research and development, assembly, Quality Control and Maintenance.

What is "Material Testing by Ultrasonics"?

Sound in the frequency range of 500 x 10³ cycles/sec(500KHz.) to about 50 x 10⁶ cycles/sec. (50 MHz.) is used for "Material Testing by Ultrasonics". It is above the human audible range and hence it is called Ultrasonic. Ultrasonic is the most extensively used NDT method. It has following inherent advantages over other methods.

• Safe
• Gives instant results
• Can penetrate high thickness
• Economical
• Can generate instant "Test Report"
• Can detect majority of types of defects
• Easy to introduce automation

Following are the types and sub-types of Ultrasonic Testing.

• Detecting discontinuity
• Locating discontinuity
• Evaluating discontinuity
• Diagnosing discontinuity

• Remaining (Residual) thickness measurement.
• Checking dimensions of a solid object.

• Determining Physical Properties.
• Percentage nodularity in SG Cast Iron.