On the Thermal Shock Wave Induced by a Moving Heat Source

1989 ◽  
Vol 111 (2) ◽  
pp. 232-238 ◽  
Author(s):  
D. Y. Tzou

Analytical solutions for the temperature field around a moving heat source in a solid with finite speed of heat propagation are obtained via the method of Green’s functions. When the speed of the moving heat source is equal to or faster than that of the thermal wave propagated in the solid, the thermal shock wave is shown to exist in the thermal field. The shock wave angle is obtained as sin−1 (1/M) for M ≥1. Orientation of crack initiation in the vicinity of the heat source is also estimated by considering the temperature gradient T,θ along the circumference of a continuum circle centered at the heat source. Such an orientation is established as a function of the thermal Mach number in the subsonic, transonic, and supersonic regimes, respectively.

1972 ◽  
Vol 22 (3) ◽  
pp. 381-385 ◽  
Author(s):  
L. A. Brichkin ◽  
Yu. V. Darinskii ◽  
L. M. Pustyl'nikov

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2052 ◽  
Author(s):  
Elham Mirkoohi ◽  
Daniel E. Seivers ◽  
Hamid Garmestani ◽  
Steven Y. Liang

Selective laser melting (SLM) is an emerging additive manufacturing (AM) technology for metals. Intricate three-dimensional parts can be generated from the powder bed by selectively melting the desired location of the powders. The process is repeated for each layer until the part is built. The necessary heat is provided by a laser. Temperature magnitude and history during SLM directly determine the molten pool dimensions, thermal stress, residual stress, balling effect, and dimensional accuracy. Laser-matter interaction is a crucial physical phenomenon in the SLM process. In this paper, five different heat source models are introduced to predict the three-dimensional temperature field analytically. These models are known as steady state moving point heat source, transient moving point heat source, semi-elliptical moving heat source, double elliptical moving heat source, and uniform moving heat source. The analytical temperature model for all of the heat source models is solved using three-dimensional differential equations of heat conduction with different approaches. The steady state and transient moving heat source are solved using a separation of variables approach. However, the rest of the models are solved by employing Green’s functions. Due to the high temperature in the presence of the laser, the temperature gradient is usually high which has a substantial impact on thermal material properties. Consequently, the temperature field is predicted by considering the temperature sensitivity thermal material properties. Moreover, due to the repeated heating and cooling, the part usually undergoes several melting and solidification cycles, and this physical phenomenon is considered by modifying the heat capacity using latent heat of melting. Furthermore, the multi-layer aspect of the metal AM process is considered by incorporating the temperature history from the previous layer since the interaction of the layers have an impact on heat transfer mechanisms. The proposed temperature field models based on different heat source approaches are validated using experimental measurement of melt pool geometry from independent experimentations. A detailed explanation of the comparison of models is also provided. Moreover, the effect of process parameters on the balling effect is also discussed.


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