Bend Radius, Thickness and Stretched Length

How large should the bending radius be, and how does it affect the stability of the component, springback and stretched length? How does the ratio between sheet thickness and bending radius affect the stretched length? This exercise explains these relationships and shows in detail, how the stretched length is calculated using the neutral fibre. However, contrary to what is often shown, this is not located in the centre, and its position changes dynamically.