Laser welding quality of motors inspected by lock-in infrared thermography

Laser welding has the advantages such as non-contaminant process, no thermal stress and etc. It has been broadly used in manufacturing especially in producing motor components, but the quality of the laser welding products is influenced by laser power, laser welding velocity and so on. To ensure the quality of the laser welding, various different detecting technologies need to be applied. Lock-in infrared thermography (IRT) is an active nondestructive testing technology utilizing modulated heat source to incite surface of samples and recording thermal response from the samples by infrared camera. The article uses FFT tool to process date received by the infrared camera, the phase difference between the defect area and the healthy area indicates the information of defects. The article uses the Lock-in IRT to detect welding quality of six stainless steel welding samples of the motors, wherein four of them are produced with different welding powers, the others are formed with the different welding velocities. Phase images acquired at a lock-in frequency of 0.3Hz show that the lock-in IRT has the ability to evaluate quality of the laser welding samples. © 2009 SPIE.