For a full penetration butt weld on thick plates, why is a double-V or double-U groove preparation often preferred over a single-V groove, especially for minimizing distortion?

For a full penetration butt weld, which is a weld where the weld metal completely fills the joint thickness to fuse the plates together, particularly on thick plates, a double-V or double-U groove preparation is significantly preferred over a single-V groove for minimizing distortion. Distortion refers to the unwanted warpage or change in shape of the welded component, primarily caused by the localized heating and subsequent cooling and solidification shrinkage of the weld metal. When weld metal solidifies, it shrinks, creating internal stresses that pull the base material. The amount and distribution of this shrinkage dictate the degree and type of distortion. Angular distortion, a common type, is characterized by the plate edges rotating out of their original plane. In a single-V groove, the weld material is deposited entirely from one side of the plate. This creates a highly asymmetrical heating and cooling cycle. As the weld metal cools and shr....