In recent years, laser transmission welding has gained in significance by displaying its specific advantages among the established welding processes for thermoplastics. However, a deep understanding of the developed process variants is so far missing. Useful results for temperature development were obtained in cases of high absorption constants by setting up an analytical model by analogy to single‐sided heat impulse welding. Yet there is no physico‐mathematical model considering the different energy conditions for joining parts with various absorption properties. This investigation is a first step towards a deep and detailed insight into the heating phase of the laser transmission welding process. Experimental data for temperature progression was collected for polypropylene. In addition, an analysis of the heat transfer problem using the finite element method showed a good level of agreement with the experimental results.
In laser transmission welding, the parts to be joined are brought into contact prior to welding, and the heating and joining phases take place simultaneously. The laser beam of the N d: YAG laser penetrates the transparent part being joined and is converted into heat by the absorbing part. The transparent part is similarly heated and plasticized by means of heat conduction, thereby ensuring that the parts are welded together.When the heating phase was analyzed, it was seen that if the part that absorbs the laser beam has a high absorption constant, this process phase can be readily described by a physico-mathematical model, by analogy to single-sided heat impulse welding. A comparison of calculated and measured melt layer thicknesses showed that, by introducing a correction factor, it is possible for this model to be successfully used for the case of a low absorption constant as well.
The Pacific Northwest Laboratory is conducting a four-phase program for measuring and evaluating the effectiveness and reliability of in-service inspection (lSI} performed on the primary system piping welds of commercial light water reactors (l..WRs). Phase I of the program is complete. A survey was made of the state of practice for ultrasonic rsr of LWR primary system piping ·Nelds. Fracture mechanics calculations 'Nere made to establ-ish required nondestru:tive testing sensitivities. In general, it was found that fatigue flaw·s less t11an 25% of wall :hic!
In laser transmission welding, the parts to be joined are brought into contact prior to welding, and the heating and joining phase take place simultaneously. The laser beam of the Nd:YAG laser penetrates the transparent part being joined and is converted into heat by the absorbing part. The transparent part is similarly heated and plasticised by means of heat conduction, thereby ensuring that the parts are welded together. When the heating phase was analysed, it was seen that if the part that absorbs the laser beam has a high adsorption constant, this process phase can be readily described by a physico-mathematical model by analogy to single-sided heat impulse welding. A comparison of calculated and measured melt layer thicknesses showed that, by introducing a correction factor, it is possible for this model to be successfully used for the case of a low absorption constant as well.
This paper extends the investigation of critical-angle phenomena and investigates the relationships between material properties and the condition (F0) for which zero reflectivity occurs. It was found that material attenuation, density, and velocity all influence F0. Graphs are presented for several materials from which the reader may determine F0 for a particular sample. Measurements which further verify the accuracy of the model, which we have used in these calculations, are also presented.
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