bendradius

Bend radius is the radius of the curve through which a flexible element is bent. It is commonly described in three related forms: inner bend radius (the radius to the inner surface of the bend), centerline or midline bend radius (to the material’s centerline), and outer bend radius (to the outer surface). The centerline radius is a standard reference in many cables and piping specifications.

Why bend radius matters: Too small a bend radius concentrates strain, increasing the risk of kinking, wall collapse, cracks, or fatigue failure. In cables and fiber optics, excessive bending can impair signal integrity or cause insulation damage. In piping or hose assemblies, bending beyond capability can reduce pressure rating or lead to leaks. Material stiffness, wall thickness, and operating environment all influence suitable bend radii.

Measurement and relationships: For hollow sections, inner radius Ri, outer radius Ro and wall thickness t relate roughly by Ro = Ri + t, while the midline radius Rm is approximately Ri + t/2. The minimum bend radius is often specified as a multiple of diameter D (for tubes and cables) or of wall thickness t for metal components (for example, 2–6t in various industries). Exact values depend on material properties, ductility, and manufacturing method.

Applications: Bend radii are specified for electrical cables, hydraulic and pneumatic hoses, metal tubes, and printed circuit board traces. Different materials have different ductility and fatigue limits, so designers rely on manufacturer data and standard guidelines to ensure reliability and avoid damage during installation and use.

Design and testing: When in doubt, use gradual curves or fittings to increase the effective bend radius, and perform bend tests or simulations to verify performance over expected service conditions.