Testing technology for Thermography

Thermography, also called infrared test or thermal imaging test, is a non-destructive method for optical testing of components and joints for internal and external defects. Heat changes and temperature distributions of the test object are detected by means of heat radiation (infrared radiation), which is invisible to the human eye. The process of so-called passive thermography, in which the intrinsic heat of an object is measured, is used in many areas to detect overheating (hot spots) as well as to control insulation or insulation in plants and buildings. For quality control and process monitoring in industrial production, the process of active thermography is used most of the time. Test items are specifically heated by external excitation. The fault detection is based on the principle that defects or joints cause a disturbance of the heat propagation. The heat flow can be detected by a digital high-speed camera with area sensors as a series of thermal images (heat flow thermography). For visualization, the measured values are displayed in gray values or false colors. The evaluation of the infrared videos can be done by an automated image processing system. For the pulse thermography, the heat excitation can be done for example by means of a flashbulb or a laser, in the method of lock-in thermography, for example, by halogen lamps or application of electrical voltage. After heat stimulation the test items is recorded with a very fast high-resolution infrared camera. At defects or joints the heat propagation is disturbed, which is recognizable by the evaluation of the infrared videos. In welding seam inspection, the heat input on one side of the connection and the infrared image on the other side are applied to check the heat flow. In a defect-free weld there is a firm connection between the two welded parts at each point. This solid compound has a higher thermal conductivity than a defective connection. By analyzing thermal image sequences, defects in the welds can be detected. Thermography is used in particular for the automated 100% control of safety and function critical components for internal or external defects as well as for process monitoring. Typical areas of application include the non-destructive testing of bodywork welds or other load-bearing structural components with a lifetime prediction, turbine blades, solar cells and microelectronic components. User industries include the automotive and automotive supply industries, aerospace and steel, power plant and mechanical engineering, as well as major research facilities, universities or research and development departments of companies.