Abstract: Linear friction welding (LFW) machine is a key equipment for researching and producing higher thrust-weight ratio aero-engines .The most important part of the machine is a reciprocating vibration system. When the driving system reciprocates, the fixed clamping device system will move unavoidably. The movement is elastic or mechanical. Dynamic theoretic model of LFW is established to study the influence of the elastic vibration of the fixed clamping device system on the driving force, mechanical power, heat generation power of the machine. The results show that the rigidity has a great influence on the process of LFW. The elastic movement decreases the heat power at friction interface. There is a turning point of the influence of friction force on system output power and heat generation power if elastic distortion exists, both of the powers will decrease if friction force is too great. So the rigidity of the clamping device in FLW machine should be ensured. The research provides theoretic basis for designing LFW machine.

Key words: Elastic vibration, Friction heat, Linear friction welding machine, Reciprocating system