Control Of Penetration During Deep Penetration Laser Welding Process On Tailor Rolled Blanks

The use of tailor rolled blanks(TRB)in the automobile body manufacturing can not only reduce vehicle weight but also ensure high strength.Laser welding is one of the most effective material joining methods,and the laser welding of TRB requires the penetration depth changes along with the change of material thickness.However,process variation occurs due to the effects of many factors such as fluctuation of the focal point position,varying assisted gas pressure,and changes of thickness.Therefore,online monitoring and real-time control of TRB are an essential approach to guarantee the full penetration.In order to realize online monitoring of penetration during laser welding of TRB.At first,a coaxial monitoring system of laser welding of TRB is built to acquire images of keyhole,and these keyholes images including partial penetration,moderate full penetration,and excessive penetration are preprocessed by using morphological image processing method.Then,a penetration feature extracting method based on interaction time between material and focal area of laser beam is proposed.Next,the penetration status is divided through weld bead geometry,and then the relationship between penetration features and penetration status is studied when the laser welding parameters changed,such as laser power,welding speed,and material thickness.The results show that the penetration hole related features defined in this work can quantifiably monitor the penetration.Finally,the principal component analysis of these penetration features is conducted.It is found that the frequency of penetration hole(FPH)defined in this work makes the highest contribution,which means the FPH can be used as a control signal of penetration.In order to realize real-time control penetration during laser welding of TRB.This work applies time-domain signal,FPH,in laser welding of TRB,At first,the penetration control scheme is designed through analyzing laser welding system.Then,a fuzzy controller based on welding experience,and a hardware scheme based on system requirements are designed.Next,controlled object model during laser welding of 1.6-2.0mm TRB is built by adaptive neural fuzzy inferences system(ANFIS).Finally,two simulation experiments are designed and conducted under different welding conditions,with the sine curve of the thickness and different initial laser power,which proved the penetration controller is effective and stable.