Short-pulse laser processing is usually referred to as"cold" due to the very high intensities causing a largefraction of the processed material to evaporate. Thisminimizes the thermal interaction with the remainingmaterial. However, very often recast layers and rims ofmolten material are observed in metal processing. Inthe case of CFRP processing much larger heat affectedzones are observed than expected from pure heatconduction. Besides plasma energy redistribution andscattering the so-called heat accumulation is very oftenmade responsible for such thermal effects.An analytical model was used to describe the processof heat accumulation. It allows estimating the amountof energy which does not contribute to the processitself and remains as heat in the material contributingto a time-averaged temperature increase. The modeltakes 3-D heat flow into account for different pulserepetition rates and beam profiles.
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