e894a5i

e894a5i - ESNC 460/894 Assignment 5 Mar 31 2006 due Apr 7...

This preview shows page 1. Sign up to view the full content.

ESNC 460/894 Assignment 5: Mar. 31, 2006 due Apr. 7, 2006 1. A light pulse of 7x10 7 W/m 2 is incident ont a semi-infintie 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 1 mm below the surface for times up to 0.1 sec. 2(a) Using the energy balance approach, estimate the power required to produce a spot weld 3 mm 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 diffusion depth given in part (a) with what is sometimes called the thermal penetration depth predicted on the basis of the uniform irradiance model. The thermal penetration depth is where the temperature changed is reduced by 1/e or about 37% 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)? 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
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern