I am engaged in the sheet metal industry, and sometimes I have to calculate the unfolded size of parts, so I must know the bending coefficient of metal. I usually contact iron, which is generally calculated according to 1.8, and this only refers to the situation of bending 90 degrees. If the bending angle is 135, 120, or any angle, I don't know how to calculate it. Do you know any netizens? Please tell me in detail. Also, I know that accurate calculation needs neutral layer, but I haven't seen this kind of table about neutral layer, so I can't check the parameters from all angles. I would appreciate it if you knew this table about the neutral layer.

Give me the website of relevant information.