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Course of ADVANCED MANUFACTURING PROCESSES Proff. Michele Monno – Barbara Previtali – Matteo Strano SURNAME NAME PERSONAL ID Exam - February 9th 2017 Exercise n. 1 – scientific article comprehension You are the person in charge of research and development team in a university group. Your project is focused on thermal process investigation of a laser treatment, which final purpose is a surface patterning modification, with a dimples array on a EN3 low carbon steel substrate. About this, the article “Hydrodynamic Physical Modeling of laser Drilling” by D.K.Y. Low, L. Li, P.J. Byrd can help your team in problem comprehension. Referring to the article: 1. It is asked a schematic representation of described complex problem. In the sketch it is required a schematization of optical setup with employed laser source, a schematization of employed laser head and the beam delivery up to the sample. 2. Referring to the article, determine the absorbed laser intensity Iabs . To solve the request you must consider: • You have at your disposal the same laser source of the article (Nd:YAG) • Laser source power Pavr = 400 W • Pulse Repetition Rate, fp= 148 Hz • Pulse width, ! = 1 ms • Pulse behaviour is represented in figure 1. Iabs=_____________ MW/cm2 Ppeak P ! 1/$%='% ' Figure 1 Temporal profile of the employed pulsed laser source 3. Considering the previous points, it is asked to determine the value of melt surface temperature, Ts [K], considering laser drilling using O2 as assistance gas. Ts=_____________ [K] 4. Considering previous points, it is asked to calculate drilling velocity Vd considering a treatment with O2 assistance gas. In this condition which is the predominant effect? Why? Vd=_____________ cm/s It is asked to check the correct answer and to justify your choice. § Melt…