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Change in load of extension springs

keyword
load
springmaterials
springdesign
SWP-B
extensionsprings

Question TETSU

Nice to meet you. I designed an extension spring (SWP-B) within the allowable value and operated it 1 million times, but the specified load dropped by about 1% before and after the processing process. Since the JIS tolerance is ± 8%, I think it is in a negligible range, but is this phenomenon usually happen?

Answer Tokai Spring

Thank you for writing to us, TETSU! Actually, there is a possibility that some load loss may occur due to working stress and heat treatment during manufacturing. In addition, there is a possibility that this is caused by the initial permanent deformation!

Answer TETSU

Thank you very much. What is the reason for the initial permanent deformation? (Strictly speaking, is it because the stress-strain curve is not linear?)

Answer Tokai Spring

Hello TETSU! If the stress-strain curve exceeds the elastic limit, it may not be linear. Also, in a high-temperature environment, when certain stress is applied to the material for a long time, the strain is large at the beginning, but the strain gradually decreases and eventually disappears. This often happens to springs. Even at room temperature, the phenomenon is more likely to occur, though not as much as at high temperatures.

Answer Azril

Hi,

Can please help to share the calculation for lift up force from extension hook spring?

Thank you

Answer Tokai Spring

Dear Azril,

Please check the formulas here for your reference:

Extension Springs: Calculation Formulas

If you have any other questions, please do not hesitate to contact us anytime!

Best regards,
Tokai Spring’s Support Team

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