Bøjningsradius

Bøjningsradius, or bend radius, is the radius of curvature of a part that has been bent. In engineering practice the centerline bend radius, R, is commonly used, defined as the radius of the circle that lies along the middle of the material’s cross-section as the bend forms. The inner and outer radii of the bend are approximately R − t and R + t, where t is the material thickness.

Why it matters: the bend radius affects fit, strength, flow, and the likelihood of material damage. If the bend is too sharp for the material, cracks, excessive thinning, or wrinkling can occur. Manufacturing processes also exhibit springback, a partial return toward straightness after forming, so the tool set must account for it.

Factors influencing the minimum bend radius include material ductility and grain structure, thickness and cross-section, heat treating state, and the bending method (for example, plain bending, mandrel bending, or rotary draw bending). Lubrication, tooling geometry, and bend angle also play roles.

Measurement and standards: bend radii are specified in terms of the centerline radius, often expressed as a multiple of thickness (R = k·t). The minimum bend radius grows with decreasing ductility and increasing thickness or stiffness. Designers consult material data sheets and standards from industry organizations for guidance.

Applications: bend radii are important in tubes and pipes, electrical wiring conduits, hydraulic hoses, and sheet-metal components. The chosen radius influences flow capacity, weight, and assembly tolerances, as well as springback and fatigue life.