I'm looking for a formula that describes the bending behavior of Aluminum (in function of Al-type thickness, shape,…); I want to know at what bending angle aluminum starts to deform (so not springs back to his initial position).
Unless You are dealing with "annealed or low-alloyed" aluminum there WILL be a critical minimum bend-radius and a minimum "spring-back" factor in every case. Note: for virtually every alloy/temper combination [or "similar-to" combination] this data is published. I use company data so I can't send you numbers; however, many aircraft sheet metal fab manuals have this data.
Note: simple bend-tests should confirm min BR and spring-back for various samples.
NOTE: this data is usually valid for STRAIGHT-LINE bends using constrained tooling, such as a "break" with radiused edges. Caution: bends thru a curve CAN present different challenges!!!
NOTE: deburr edges carefully and examine outer BR surfaces and edges with 10X--50X magnification for signs of cracking [NDI if questionable]. Regards, Wil Taylor
I had the same question in the past and someone gave me a bending calculator software is pretty handy and it helps to reduce testing. email me and I'll send it to you