Optimization of Laser Transmission Joining Process Parameters on Joint Strength of PET and 316？L Stainless Steel Joint Using Response Surface Methodology
The objective of the present work is to study the effects of laser power, joining speed, and stand-off distance on the joint strength of PET and 316？L stainless steel joint. The process parameters were optimized using response methodology for achieving good joint strength. The central composite design (CCD) has been utilized to plan the experiments and response surface methodology (RSM) is employed to develop mathematical model between laser transmission joining parameters and desired response (joint strength). From the ANOVA (analysis of variance), it was concluded that laser power is contributing more and it is followed by joining speed and stand-off distance. In the range of process parameters, the result shows that laser power increases and joint strength increases. Whereas joining speed increases, joint strength increases. The joint strength increases with the increase of the stand-off distance until it reaches the center value; the joint strength then starts to decrease with the increase of stand-off distance beyond the center limit. Optimum values of laser power, joining speed, and stand-off distance were found to be？18 watt, 100？mm/min, and 2？mm to get the maximum joint strength (predicted: 88.48？MPa). There was approximately 3.37% error in the experimental and modeled results of joint strength. 1. Introduction Laser transmission joining has various advantages over conventional plastic joining techniques, for example, no contact, high joining speed, accuracy, flexibility, small heat affected zone, and so forth. Laser transmission joining technology has extensively promising applications in the fields of the microfluidics, microelectromechanical systems, and biomedicine [1, 2]. During laser transmission welding of overlap connections laser radiation transmits through the upper thermoplastic part and is absorbed by a lower material. Heat is developed in the laser absorbing part, which melts the thermoplastic locally. Due to heat conduction, the laser transparent part melts locally too. Thermoplastic materials are laser radiation absorbing, when the material contains, for example, carbon black, absorbing additives, and pigments or when the materials are reinforced with carbon fibers [3]. There is a continuously growing interest in the joining of dissimilar materials in manufacturing industries. Joining of PET to 316？L stainless steel is found in a number of industrial applications [4]. The advantages of laser transmission joining are as follows: (a) exact control of the energy deposition in the joining area; (b) minimization of the heat affected
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