Nice to meet you.
I would like to know about the stress calculation of extension springs. The shear stress due to the initial tension (initial stress) can be calculated because there is a calculation formula. However, I heard from the advice of a business partner that the initial tension is 25% lower than the calculation due to heat treatment. In that case, I guess that the stress will also decrease, but in general, does heat treatment reduce the initial tension?
How is your company considering it? I would like to know for reference.
Since extension coil springs actively utilize the initial tension, low-temperature annealing after coiling causes a decrease in the initial tension if it is performed at a very high temperature for a long time, so it is necessary to apply it appropriately.
In general, the initial tension for materials other than steel wire and for low-temperature annealing is modified as follows.
In the case of stainless steel wire, it will be reduced by 15% of steel wire, and in the case of phosphor bronze wire, brass wire, nickel silver wire, etc., it will be reduced by 50% of that of steel wire.
In addition, when low-temperature annealing is performed after coiling, the initial tension of piano wire, hard steel wire, etc. will be reduced by 20 to 35%, and for stainless steel wire, it will be reduced by 15 to 25%.
