Ultrasonic testing

Ultrasonic inspection is one of the NDT methods which uses high frequency ultrasounds. Most of the ultrasonic inspections are performed at frequencies between 5 to 20 MHZ, which is upper than the human hearing limit (almost 20 HZ to 20 KHZ). The ultrasonic waves lose their energy when transmitting through the material because of the material properties. The intensity of the ultrasonic waves, is measured after reflecting from the interface or the defect (pulse echo) or in the surface opposite to the sample (transmitted pulse). The reflected ray is detected and analyzed to determine the place of the defect. The amount of reflection mainly depends on the physical state of the material in the opposite side of the interface and to a lesser extent to the special physical properties of the material. Ultrasonic testing has higher leverage ratio than radiography testing and can detect deeper defects inside the sample. It’s very sensitive to tiny imperfections and allows to determine the right place and magnitude of the defect.

Ultrasonic testing methods:

Mostly used for identification of defects in the materials
It is used in most of the materials to measure the thickness
It is used to determine the mechanical properties and grain structure of materials
It is used to appraise the parameters in manufacturing the samples

Some advantages of the ultrasonic testing are:

High sensitive to detect tiny imperfections
High penetration which allows the operator to examine very thick samples
High accuracy to measure the place and degree of the defect
High responsiveness which provides fast and automatic inspection
Only one surface of the sample is enough

Some disadvantages are:

It needs couplant
The probe should be well connected during the scan
The equipment is so expensive
It needs highly skilled operator
Rough surfaces are problematic and the surface should be prepared
The defect direction affects the identification
Improper geometry of the sample causes problems during the inspection