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e894a5h

# e894a5h - 2/s C = 0.50 J/gK k = 0.4 W/cmK T m = 1809 o K L...

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ESNC 460/894 Assignment 5: Apr. 1, 2005 due Apr. 11, 2005 1(a) Using the energy balance approach, estimate the power required to produce a spot weld 3mm in diameter and 1 mm deep in low-carbon steel with a 1 sec pulse from a CO 2 laser. Use ρ = 7.86 g/cm 3 , α = 0.07 cm 2 /s, C = 0.7 J/gK, k = 0.4 W/cmK, T m = 1809 o K, L f = 13.8 kJ/mol, R=60% (b) Compare the depth given in part (a) with the thermal penetration depth predicted on the basis of the uniform irradiance model. Remember, at this depth the temperature is only about 35% of the surface temperature. (c) According to the uniform irradiance model, how long does it take to reach T m at the surface for the power in (a)? 2 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 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
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Unformatted text preview: 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% 3 Mild steel is to be welded with a multi-kilowatt CO 2 laser. Using the model of Swift-Hook and Gick, estimate the power required to produce a weld of 2 mm width and 4.5 mm depth at 1 m/min. α = 0.09 cm 2 /s, k = 0.4 W/cmK, T m = 1809 o K 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 = 0.44 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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