This paper describes methods by which one may calculate the effects of high‐power pulses of laser radiation of specified shapes absorbed at opaque surfaces. First the heating effects at levels where no phase change is produced are treated by ordinary thermodynamics. The vaporization produced by Q‐switched lasers should proceed differently from that produced by ordinary lasers and the two processes are treated separately. The amount of material vaporized by an ordinary laser pulse is calculated using conventional methods, while we adopt a phenomenological model to treat the case of the higher peak power pulses from Q‐switched lasers. The results are in agreement with experimental data.

Effects Due to Absorption of Laser Radiation

Publisher Summary In the field of heat transfer, and more especially heat conduction, the transient heat conduction equation is linearized by assuming the thermal properties to be independent of temperature; furthermore, the boundary conditions are also taken to be linear. When dealing with heat conduction in solids, the linear approximation is often quite acceptable. This chapter presents a mathematical technique, called the integral method, by which approximate solutions to nonlinear transient heat conduction problems can be obtained. Such problems need not be linearized, because the technique is elastic enough to encompass all nonlinearities. The integral method reduces the nonlinear boundary value problem to an ordinary initial value problem whose solution can frequently be expressed in closed analytical form. The integral method can also be used to obtain approximate solutions to linear problems with complicated spatially-dependent thermal properties, and problems where convection as well as conduction is involved. The versatility of the method is demonstrated using several numerical examples.

Application of Integral Methods to Transient Nonlinear Heat Transfer

A measurement system consisting of two high- speed two- color pyrometers was used to monitor the flattening degree and cooling rate of zirconia particles on a smooth steel substrate at 75 or 150 °C during plasma spray deposition This instrument provided data on the deformation behavior and freezing of a particle when it impinged on the surface, in connection with its velocity, size, and molten state at impact The results emphasized the influence of temperature and surface conditions on particle spreading and cooling When the substrate temperature was 150 °C, the splats had a perfect lenticular shape, and the thermal interface resistance between the lamella and the substrate ranged from 10− 7 to 10− 8 W/m2 · K The dependence of the flattening degree on the Reynolds number was investigated

Influence of particle parameters at impact on splat formation and solidification in plasma spraying processes

Material removal from the front surface of a solid by a high-intensity laser beam is analytically treated. The model used allows for transmission of laser energy past the front surface and for transient phenomena. It is found that for certain laser and material parameters subsurface temperatures will exceed the surface temperature. Under such conditions, explosive removal of material could occur resulting in very rapid and efficient material removal. These predictions are compared to previously published experimental results.

High-intensity laser-induced vaporization and explosion of solid material

From constrained to unconstrained growth during directional solidification

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H. G. Landau

Papers

Heat conduction in a melting solid