What is the term for the location at which the metal starts to bend?

The term that describes the location at which the metal starts to bend is referred to as the neutral axis. This is the line where the material experiences no tensile or compressive stress during the bending process. When a material is bent, the outer fibers are elongated (under tension) while the inner fibers are shortened (under compression). The neutral axis is critical in structural analysis because it helps determine how the material will react under load and is used to calculate the moments of inertia in beams and structural components.

The bend tangent line and bend start line are not standard terms used in structural engineering or materials science; they may describe related concepts but do not specifically define the critical point where bending initiates within the material. Similarly, curvature guideline does not accurately represent the initial bending location but might imply aspects of the bending process in a more general sense without pinpointing its significance in terms of stress distribution.

Understanding the concept of the neutral axis is essential for engineers and technicians involved in aircraft metal structural repair, as it impacts material selection, repair techniques, and overall structural integrity.