On-line Monitoring of the Laser Joining Process of Aluminum Alloy and Polyamide 6.6 by Acoustic Emission Analysis

A novel Laser joining process for polyamide and aluminium hybrid structures has proven a strong bond between these dissimilar materials. This newly developed welding technique is strongly requested by the automobile producing industry for several applications within the car structure. However, the joining quality exhibits a strong dependency to process-related variables, which highlights the need for an online inspection technique. In that case only the acoustic emission analysis (AEA) as a Non-destructive Technique (NDT) can be used to guarantee reasonable results. Sometimes the break of the melting bath can occur and is often not recognizable by optical methods. The AEA however was able to detect this lack of fusion. The appearance of gas bubbles, arising from the PA 6.6 could be detected by the AEA. The signals related to this effect can be correlated clearly to micrographic sections. Future tasks will develop algorithms to separate the different defects by pattern recognition of the AEA signals and parameters.