Kaarekeevitus

Kaarekeevitus is a term used in structural metalworking to describe a curvature distortion that can occur in welded assemblies. The word is formed from Estonian roots kaar, meaning arc or curve, and keevitus, meaning welding, and it is sometimes encountered in theoretical discussions of weld-induced distortion, though it is not a universally standardized term in engineering literature.

Definition and scope

Kaarekeevitus refers to a residual bend or camber along a weld seam or across a welded component that persists after the workpiece has cooled, and that exceeds typical distortion margins for the given fabrication. It is one form of weld-induced deformation and is considered in conjunction with other distortions such as bow, twist, or waviness.

Mechanism

The effect arises from nonuniform heating and cooling of the weld area. Differential thermal expansion and contraction between the weld metal, heat-affected zone, and surrounding base metal generate internal stresses. When the structure is restrained by fixtures or adjacent members, these stresses cannot fully relax, producing curvature. Welding sequence, bead geometry, and variations in joint fit-up can amplify the distortion, especially in thick or highly restrained assemblies.

Detection and measurement

Kaarekeevitus is identified through visual inspection and dimensional metrology. 3D scanning, coordinate measuring machines, and optical profilometry are used to quantify curvature along the welded region, with the distortion expressed as camber or warp relative to nominal geometry.

Prevention and mitigation

Prevention strategies include controlling heat input, preheating where appropriate, and careful fixturing to minimize restraint. A balanced weld sequence, multiple passes with consistent parameters, and proper fit-up help reduce distortion. Where needed, post-weld straightening or design tolerances that accommodate distortion may be employed.

Context

Kaarekeevitus is discussed alongside other forms of welding distortion and residual stresses in engineering texts, serving as a conceptual reminder of how thermal cycles interact with mechanical constraints in welded constructions.