Some aspects of laser heating of engineering materials

Abstract

Laser induced heating processes are important when a laser is used as a machine tool in industry, since the quality of the machining process strongly depends on the heating mechanism. The present study examines a heat transfer model that provides useful information on the laser induced interaction mechanism. Steady state and time dependent heating models are introduced and temperature profiles inside the materials are predicted. Using appropriate assumptions, the time for the surface temperature to reach 90% of its steady state value is estimated. To validate the theoretical predictions, experiments are performed to measure the surface temperature of the irradiated spot during the laser heating pulse. It is found that, during the use of a pulsed laser in the drilling process, as the heating progresses the drilling velocities rise while the liquid depth and time to reach steady state fall, in this case, the energy consumed for evaporation is higher than losses through conduction.

Laser non-conduction limited heating and prediction of surface recession velocity in relation to drilling

“…H owever, this process becomes visible at power intensities of I surf > 10 13 W=m 2 (I surf being the laser power intensity at the workpiece surface) [1]. On the other hand, at machining intensities …10 11 4 I surf 4 10 13 W=m 2 †, the vapour front generated is small in size and laser beam absorption by the vapour front is insigni cant. Consequently, the processing parameters, which control the energy input to the workpiece, in uence the extent of the melted region and this should be determined with accuracy if the simulation is to give quantitative results.…”

“…They introduced the equilibrium time, which was based on the energy balance among the internal energy gain, conduction losses and latent heat of fusion. The steady state and time-dependent heating models were introduced by Yilbas and Al-G arni [11] to predict the temperature pro les. They indicated that the drilling velocities increased as the heating progressed while the liquid depth and time to reach steady heating fell during a pulsed laser drilling process.…”

Laser Heating and the Phase Change Process

“…Solution of eqn [25] gives the values of R for melt at the point of maximum width. Y can be found from:…”

Laser Duplex Treatment of Surfaces for Improved Properties

“…Some of these techniques include plasma nitriding, coating and carbonizing, and laser gas-assisted processing (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). The alloy surface has poor tribological properties and several techniques have been considered to improve surface properties of the alloy.…”

“…where C 0 is constant, i.e., a constant flux at the surface and it is 0.56 kg m À3 (20). The semi-infinite consideration of the surface allows incorporating zero flux at a depth well below the surface, which yields…”