Vicinity Of Heat Source Research Articles

A numerical-experimental investigation of heat distribution, stress field and crack susceptibility in Ni60A coatings

3D finite element model (FEM) was built for the simulation of temperature and stress field induced by laser cladding. The proposed model was validated by experimental results. The numerical width and depth of coating matched well with the experimental cross-section of macrograph. The viscosity of molten pool versus the temperature field was also discussed, and the maximum difference of viscosity in different zones was approximately 32.8%. High temperature and sharp thermal gradient was generated in the vicinity of heat source, which was prone to produce residual stress. The heat distribution obtained from temperature field was in consistent with the thermocouple measurements. Due to large plastic tensile deformation of materials, the longitudinal residual stress was susceptible to crack propagation in the laser cladding. The measured maximum value of longitudinal residual stress reached 492 MPa, which was lower than predicts. The coatings were apt to crack along the vertical scanning direction. In addition, the crack susceptibility of coatings was not only depended on residual stress, but also the microsegregation of Cr, Ni and Fe elements. The calculation results are helpful for systematically understanding the melt pool, heat cycles, and stress, which related to laser cladding Ni-based materials.

NUMERICAL SIMULATION OF MIXED CONVECTION FLOW OVER HEAT SOURCE MODULES MOUNTED ON A HORIZONTAL PLATE

Mixed convection flow over heat source modules mounted on a horizontal plate has been studied numerically. The present analysis is valid when the buoyancy force effects are small compared to forced convection effects. The mixed convection flow problem is formulated by two-dimensional incompressible flow with the buoyancy term represented by the Boussinesq approximation. The governing equations are solved in the stream function and vorticity formulation using high accuracy finite difference schemes. Results are reported for single and two heat source modules mounted on a horizontal plate with and without thickness. The effects of induced velocity, heat input, thickness, and location of heat source modules on heat transfer rate and thermal field in the vicinity of heat sources are reported. Results have shown that there is a decrease of maximum temperature on heat source modules with increase in free-stream velocity of the fluid. Results show that the change of location and thickness of heat source modules has a significant effect on thermal flow field characteristics. The maximum temperature and average Nusselt number on heat source modules are reported at different parameters. The reported results agreed well with experimental results available in the literature.