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Course of ADVANCED MANUFACTURING PROCESSES Proff. Michele Monno – Barbara Previtali – Matteo Strano SURNAME NAME PERSONAL ID Exam - September 13th 2016 Exercise n. 1 – scientific article comprehension You are the chief engineer of research and development team in a company specialized in surface patterning. Your project is focalized on wettability surface modification, in particular your purpose is the investigation of laser ablation patterning technique in order to optimize surface hydrophobicity of a 316 stainless steel sheet. About this, the article “Surface geometrical model modification and contact angle prediction for laser patterned steel surface” by B.H. Luo, P.W. Shum, Z.F. Zhou, K.Y. Li can help your team in problem solving. Referring to article and considering Figure 1: 1. You have at your disposal the same type of laser source: a nanosecond pulsed fiber laser YLP-1/100/50/50 from IPG Photonics. The laser source provides a collimated beam at the output, which is manipulated in X and Y coordinates by means of a scanner head (TSH 8310 by Sunny Technology, Beijing, China) in order to realize pattern treatment. The scanner head is equipped with an f-theta lens with 100 mm focal distance that allows a flat scanning plane. The main specifications of employed system are reported in table 1. It is needed the identification of beam focal position in order to replicate the laser ablation treatment detailed in the article (Laser ablated area with a width of b=50 µm). Wavelength λ [nm] 1064 Maximum Power P [W] 50 Pulse duration τ [ns] 250 Pulse repetition rate PRR [kHz] 20-80 Beam quality factor M2 1.7 Collimated beam diameter dc [mm] 5.9 Focal lens f [mm] 100 Focused beam diameter d0 [µm] 39 Beam focal position Δz =_________mm 2. Referring to the experiments part in…