Abstract
The absorptivity of laser radiation of metals is investigated in several studies. Therefore, absorption coefficients depending on temperature or roughness are known. However, many processes use iterative processing strategies, such as additive manufacturing, laser beam bending, or laser-assisted incremental forming. Simulations of these processes often use literature data for absorption coefficients and do not consider the variation of absorptivity during the process. In this study, the influences of multiple laser beam processing on absorptivity are investigated for stainless steel sheets. Absorption and roughness measurements are compared before and after heating treatments with the laser beam or in an oven. It is shown that an increasing amount of laser heating cycles correlates with higher absorptivity and higher roughness values. However, this increase of roughness is not considered to be sufficient for enhanced absorptivity. On the one hand, similar changes of absorptivity were detected when heating steel sheets in an oven. These oven-heated specimens do not show extensive roughness changes. On the other hand, the same amount of laser heating cycles with additional cool down time after each cycle results in a negligible absorptivity change. Therefore, the variation of the absorptivity is attributed to oxidation.
Highlights
Laser radiation can be used for several applications
When it comes to materials processing, the efficiency of laser beam processing is dependent on the absorption of the irradiated material
For analyzing the effects of multiple laser processing, it is mandatory to measure the initial states For oafntahleyaznianlgyztehdeveaflufeecs.tsThoefrmefourlet,itphleemlaesaenrvpalruoecseosfsrionugg,hinteisssmanadnadbastoorprytiotnommeeaasusruermeetnhtseoifnailtlial states of the anuanlytrzeeadtedvasplueceism.eTnhs earreefliostreed, tinheTambleea1n. values of roughness and absorption measurements of all untreated specimens are listed iTnabTlea1b. lTehe1.mean values of initial state specimens
Summary
Laser radiation can be used for several applications When it comes to materials processing, the efficiency of laser beam processing is dependent on the absorption of the irradiated material. Absorption of laser beams is dependent on the laser wavelength and the irradiated material and its topography. Various absorptivity-enhancing coatings were irradiated with different laser beam intensities. Dausinger and Shen analyzed the absorption of laser radiation with various wavelengths in iron and steels [2]. From 0 ◦C–800 ◦C absorptivity decreases by about 7% and stays rather constant for temperatures over 800 ◦C. This is often neglected in numerical simulations. Bielak et al, for example, assumed a linear increase of the absorption in a temperature range from 350 ◦C–500 ◦C during their simulations [3]
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