Infrared and thermal testing work based on the principle that all objects emit electromagnetic radiation of a wavelength dependent on the object’s temperature. The wavelength of that radiation is inversely proportional to the object’s temperature. Infrared testing involves non-destructive, non-intrusive and no-contact mapping of an object’s temperature and can predict and diagnose object failure.
What Is Infrared?
The infrared spectrum of light is characterised by wavelengths longer than those of visible light. Infrared wavelengths are located on the nominal red side of the visible light spectrum – at wavelengths between 700 nanometres and 1mm.
Types of Infrared Thermography
There are two main types of infrared thermography: passive thermography and active thermography.
Passive Thermography: Passive thermography involves examination of an object during normal operation. No additional energy source is applied with the purpose of generating a thermal gradient in the object undergoing testing.
Active Thermography: Active thermography refers to the examination of an object after an external energy source has been applied to it. The energy source may be a heat source, mechanical energy like vibration or fatigue testing, electrical current or any other form of energy.
How Does Infrared Thermography Work?
An infrared thermographic camera measures temperature patterns according to variations in temperature as little as a few hundredths of a degree celsius. An infrared camera detects emitted radiation and converts it into electrical signals which are displayed on a coloured monitor. The visual image which is produced by an infrared thermographic camera is called a thermogram. It contains a map of temperature patterns according to the temperature of the test object.
Test Condition Requirements For Infrared Thermography
Thermographic non-destructive testing requires identification of a number of variables in order to complete thermographic non-destructive testing successfully:
- The heat required to detect discontinuities must be determined.
- The required heating rate (for active thermography) depends on surface properties and equipment characteristics such as speed and sensitivity.
- The engineer responsible for testing must be aware of whether the test object’s surface requires a strippable paint or coating because of the low emissivity of the test surface.
- The profile of time versus temperature is required to reveal discontinuities in the target object.
An appropriate heat source must be selected if required. Similarly, a detector (infrared camera) with the right specifications for the job must be chosen before testing can commence.
Contact NDT Australia
If you are looking for thermographic non-destructive testing equipment, check out NDT Australia’s online store. We supply a range of NDT technology, including infrared and thermographic non-destructive testing equipment, and can consult you about which equipment is most appropriate for non-destructive testing in your unique situation. We are open for business Monday to Friday, 7:30am to 4:00pm. Contact our friendly sales team on (02) 9524 0558 to ask any questions or to place an order for any of the products listed on our online store.
