Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld. This book presents current research data in the study of welding, including the design of high brightness welding guns; electron beam welding; friction stir welding; limit load solutions for highly under-matched welded joints; fracture and fatigue assessment of welded structures; and laser transmission welding.