Laser beams are used to thermally process materials in a wide range of applications. Often, the beam is scanned along the surface of the material in a desired pattern. Consider the laser heating process of Problem 4.18, except now the laser beam scans the material at a scanning velocity of U. A dimensionless maximum surface temperature can be well correlated by an expression of the form for the range 0

The maximum material temperature does not occur directly below the laser beam, but a lag distance, S, behind the center of the moving beam δU/a = 0.944Pe1.55.

(a) For the laser beam size and shape, and material of Problem 4.18, determine the laser power required to achieve Tl.max = 200°C for U = 2 m/s. The density and specific heat of the material are p = 2000 kg/m3 and c = 800 J/kg ∙ K, respectively.

(b) Determine the lag distance, S, associated with U = 2 m/s.

(c) Plot the required laser power to achieve Tmax.1 200°C for 0

Transcribed Image Text:

I,max,U=0 1 + 0.301Pe -0.0108PE? Ti,max,U40 - T2