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Course of ADVANCED MANUFACTURING PROCESSES Proff. Michele Monno – Barbara Previtali – Matteo Strano Exam – June 19th, 2020 Branch 0-1 Q1 (1). Explain why the overall efficiency of the Nd:YAG source in Figure 1 is higher than the overall efficiency of the Nd:YAG source in Figure 2. Both sources suffer from the thermal lens phenomenon. Which of the two more? Justify and explain your answer. Q1. Solution Nd:YAG Lamp, which is much more affected by problem of thermal lensing in comparison to laser diode solution. On the other hands the laser diodes are characterized by a narrow laser wavelength of 800-900 nm which is able to produce a good quantic efficiency with Nd:YAG and consequently a much more efficient pumping; this is directly visible by an higher deposit energy (35% vs 5%) in Laser Diodes. The Lamp light is characterized by larger wavelength with a higher heat dissipation and much problem in terms of thermal lens phenomenon. Q2 (3). A Pure waterjet has been chosen for piercing 5 mm thick Carbon Fiber Reinforced Polymer plate, which is characterized by a limit strength of 25 N. You can choose two different working pressure: 150 MPa, 250 MPa. Which working pressure would you select? Parameter Symbol Value Unit Primary Orifice diameter 𝑑0 0.30 mm Water density 𝜌0 1000 kg/m3 Impact angle 𝜑 90° ° Compressibility coefficient, at p = 150 MPa 𝛹1 0.985 - Compressibility coefficient, at p = 250 MPa 𝛹2 0.977 - Velocity coefficient 𝐶𝑣 0.90 - Contraction coefficient 𝐶𝑐 0.62 - 𝐹 = 2𝑚̇ 𝑤𝑣𝑤𝑗𝑐𝑜𝑠𝜗 = 2𝜌0𝑄𝑤𝑣𝑤𝑗 = 2𝜌0 ∙ 𝐶𝑑𝑑0 2𝜋 4 ∙ √2𝑝 𝜌0 𝐶𝑣𝜓√2𝑝 𝜌0 = 𝜓𝐶𝑑𝐶𝑣𝑑0 2𝜋𝑝 Figure 1 Figure 2 Q2. Solution Quantities Solution 1 Solution 2 P (MPa) 150 250 Cd 0.549 0.545 F (N) 20,65 33,87 Answer: p = 150 MPa Q3. In the High Definition Plasma technology, which process parameter follows the trend shown…