Real time acoustic monitoring of excimer surface treatment of coated steels

Abstract

Zinc coated sheet steel in the form of temper rolled galvanize and galvanneal are used extensively in the automotive industry. Through a process of excimer laser surface treatment, we have developed a procedure to significantly enhance the adhesion characteristics of these coated steels. The largest improvement in bond strength observed was more than a factor of three greater than for untreated surfaces. With the improved surface condition, the bond strength became limited by the cohesive strength of the adhesive.In order to apply this technology in an industrial setting, we have developed an acoustic monitoring scheme to sense the process condition and produce a real time indication of process quality. Process quality may be adversely affected by degraded laser power output and improper focus position. Both conditions produce a change in acoustic spectral intensity which is detected by performing a real time fast Fourier transform (FFT) of the acoustic signal. It may be possible to use the output of the acoustic monitor as a feedback signal which could be applied to a process controller to optimize the surface condition for bonding and maximize the process rate.Zinc coated sheet steel in the form of temper rolled galvanize and galvanneal are used extensively in the automotive industry. Through a process of excimer laser surface treatment, we have developed a procedure to significantly enhance the adhesion characteristics of these coated steels. The largest improvement in bond strength observed was more than a factor of three greater than for untreated surfaces. With the improved surface condition, the bond strength became limited by the cohesive strength of the adhesive.In order to apply this technology in an industrial setting, we have developed an acoustic monitoring scheme to sense the process condition and produce a real time indication of process quality. Process quality may be adversely affected by degraded laser power output and improper focus position. Both conditions produce a change in acoustic spectral intensity which is detected by performing a real time fast Fourier transform (FFT) of the acoustic signal. It may be possible to use the output of the ...