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Course of ADVANCED MANUFACTURING PROCESSES Proff. Michele Monno – Barbara Previtali – Matteo Strano Exam – July 20th, 2020 Ex 1 In conventional oxyfuel cutting of thick metal sheets, a common problem is the potential lack of planarity of the workpiece after cutting (warping). This problem is much less frequent and relevant in laser beam cutting (LBC) and in plasma arc cutting (PAC). Why? 1. Because LBC and PAC provide a larger heat flux onto the work surface 2. Because oxyfuel can only work with material who easily tend to distort 3. Because LBC and PAC do not process the same sheet thickness of oxyfuel 4. Because PAC and LBC produce a narrower cutting kerf and a comparably smaller heat affected zone 1. Because PAC and LBC had a much faster feed rate and this reduces the total power transferred to the material 6. Because LBC and PAC vaporize the work material, while oxyfuel only melts it Solution Answer n°4 Ex 2 In the figure, the schematic of a thermal welding process (e.g. laser welding, rotary ultrason ic welding, plasma arc welding, conventional arc welding, resistance welding, etc.) is shown. The heat source is moving from left to right in the direction of the arrow. What is the variable x shown in the diagram? Which welding process is it? Motivate your answer. Solution The x variable is the Temperature. The process consists of Plasma arc welding. The reason is that the swirl of the gas does not generate a symmetric distribution of temperature and therefore the temperature profile of points A and B is different Ex 3 In order to increase the hardness, a 300 mm x 300 mm x 3 mm plate of alumin ium alloy 5005 has been treated using waterjet peening process. The pre-treatment aluminium 5005 alloy hardness was 46 HV (Vickers hardness). The following empirical model can…