I am thinking of designing a flat spring with SUS304 material.
When calculated from the conditions, the stress of 512 Mpa is applied. The target number of times of durability is assumed to be 100,000 times, but looking at the data of the spring limit value and S-N curve of SUS304, it is stated that:
・Spring limit of SUS304-CSP H…390Mpa or more
・S-N curve of SUS304 at 100,000 times…600Mpa
Would the flat spring I designed work well? I don’t know which material to refer to when designing a flat spring. In addition to SUS304, I am also considering SUS631 which has good strength, but there is no document referring to repeated stress, so it is difficult to select the material.
I look forward to your reply.
References:
http://www.bkeye.com/pdf/SUS-CSP-hyou6.pdf https://astamuse.com/ja/drawing/JP/2004/027/325/A/000003.png
Dear Fuji, thank you for your question!
I can’t say anything about the data of the attached links because I don’t know the source, but SUS304 and SUS304 CSP-H are the same material, just the finishing state of the materials is different.
By cold rolling, stainless steel strips for springs: CSP-H (JIS G 4313) has a high tensile strength of 1130 N/mm2, and by solution treatment, the tensile strength of cold-rolled stainless steel sheets and steel strips: CS (JIS G 4305) is 520 N/mm2 or more. Therefore, I think it is better to select CSP material!
Also, it is considered that the spring limit value ≒ 10^7 times or more, and it might not appropriate to compare it at the point of 100,000 times! If you provide us with more details from the link below, we can evaluate the strength ♪ Thank you!
Contact form
A cantilever spring of SUS301CSP material (reference: Young’s modulus 186000) with a plate thickness of 0.15 mm, a width of 1.3 mm and a length of 6.2 mm, and when a load of about 0.9 N was applied, it was calculated to be able to bend to about 1.05 mm.
I would like to know what the spring limit value at this time is. JIS describes it as proof stress and tensile strength, but is proof stress applicable in this case?
The problem here is that a battery terminal does not change the shape until the battery is removed once it comes into contact. Since the spring limit value is the value after tens of thousands of tests, it is not clear how to determine the spring limit value in an example such as this time when the contact time is only once.
Spring Newbie, thank you for your question!!!
Regarding the thin leaf spring of SUS301 CSP, when the spring limit value is set as the maximum stress to be used, the tensile strength of the material is used as a standard and multiplied by a coefficient.
For example, if there is a material with a tensile strength of 1200 N/mm^2, the maximum stress to be used at the point where the load is fixed is 1200 x 0.6 = 720 N/mm^2. For the multiplication coefficient, please use the above 0.6 as the standard.
In addition, when the product is used under a dynamic load (thousands or more), the durability is evaluated from the minimum stress and the maximum stress. Generally, it is estimated from the endurance limit diagram called the S-N diagram.
Thanks again for your question!!!
