Tham khảo tài liệu 'laser welding part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 134 Laser Welding In both the conduction and convective transport based models the laser beam is considered as a surface heat source with Gaussian energy distribution. In conduction based heat transfer analysis a volumetric heat source is often used further to numerically compensate the influence of convection heat transport in weld pool. The existing approach to define a volumetric heat source needs a-priori definition of its shape and size that restricts the use of the same Goldak et al. 1984 Frewin Scott 1999 De et al. 2003 . We have introduced an adaptive volumetric heat source term to make it more general and close to the reality. The adaptive volumetric term is defined by mapping the instantaneous value of the computed weld dimensions length width and depth with respect to time step transient or load step steady-state and thus the requirement of a-priori definition of the source geometry is avoided. Lastly both conduction and convective heat transport based simulations of laser welding needs a number of parameters which are required for model calculations and cannot be defined by scientific principles alone. Absorption coefficient effective thermal conductivity and viscosity of molten material in weld pool and parameter defining the nature of energy distribution are examples of such parameters in laser welding simulations Chande Mazumder 1884 Tanriver et al. 2000 De DebRoy 2005 . Here we show that a robust optmization algorithm integrated with the numerical process models can help in identifying suitable values of the uncertain model parameters and provide reliable computed results. The present work includes a finite element based three-dimensional transient and quasisteady heat transfer and fluid flow model for the prediction of temperature and velocity field and weld dimensions in laser welding process. The novel feature introduced in the conduction model is the adaptive volumetric heat source term that is used to account for the energy absorbed by the .
