Dynamic focal spot and extremum effect of deep penetration of electron beam

The measurement methods of focal spot with welding characteristic are analyzed.Using the simple model of molten pool,the inherence relation of the different measurement methods with the welding property is illuminated.The conception of dynamic focal spot is set up,and the factors which influence the dynamic focal spot are discussed.Furthermore,the characters of dynamic focal spot are analyzed,and the most important character is the extremum effect of deep penetration of electron beam.