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e894a5j - kerf Using energy balance estimate the power that...

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ESNC 460/894 Assignment 5: Mar. 31, 2008 due Apr. 7, 2008 1. A light pulse of 9x10 7 W/m 2 is incident onto a semi-infinite slab of nickel. The energy is uniformly distributed over a circle of radius 1 mm. The nickel is coated to allow perfect absorption. Plot a graph of the temperature variation directly below the center of the spot at the surface and at 0.07 mm below the surface for times up to 0.05 sec. 2 Keyhole welding is to be done on mild steel with a multi-kilowatt CO 2 laser. Using the model of keyhole welding, estimate the power required to produce a weld of 2 mm width and 4.5 mm depth at 1 m/min. Use the following parameters α = 0.09 cm 2 /s, k = 0.4 W/cmK, T m = 1809 o K 3 Low carbon steel of 5 mm thickness is to be cut with a laser at a speed of 1.25 m/min. with a 0.5 mm
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Unformatted text preview: kerf. Using energy balance, estimate the power that must be coupled into the material. Use ρ = 7.86 g/cm 3 , α = 0.07 cm 2 /s, C = 0.50 J/gK, k = 0.4 W/cmK, T m = 1809 o K, L f = 13.8 kJ/mol, L v = 350 kJ/mol, T v = 3135 o K, R=60% 4 Holes are to be drilled in 0.5 mm thick nickel with a diameter of 0.13 mm, using a pulsed Nd:YAG laser with a 4 kW peak power output. Use energy balance equations to estimate the energy needed and the pulse length, assuming a nearly square pulse in time. Show that the time to reach vaporization at the surface is very small, based on the results of the uniform irradiance model. ρ = 8.9 g/cm 3 , C = 0.444 J/gK, k = 0.91 W/cmK, T m = 1726 o K, L f = 298 J/g, L v = 6303J/g, T v = 3187 o K, R=60%...
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