After introducing the concepts and characteristics of welding thermal processes and weld pool behaviors, this book addresses essential advances in welding analysis and processes with an emphasis on the latest modeling and simulation methods. It covers techniques and formulas for assessing welding thermal processes, finite difference and finite analysis methods for calculating thermal conduction, and numerical simulation of weld pool behaviors in metal-inert-gas/metal-active-gas arc welding, It also covers keyhole and weld pool dynamics in plasma arc welding and vision-based sensing of weld pool shape and geometry. It also provides case studies of fluid flow and heat transfer in tungsten-inert-gas arc welding.