I would like to ask you a question.
There are allowable ranges in flat spring design such as allowable bending stress, proof stress, spring limit value (and others). Can you tell me what each means? Are they applied differently depending on whether the load is static or dynamic?
Thank you for writing to us!
Regarding the meaning of each value…
– Allowable bending stress ⇒ Maximum static stress that does not cause permanent deformation of the spring.
– Proof stress ⇒ Stress that causes a certain amount of plastic strain in the material.
– Spring limit value ⇒ Stress that causes the spring to flex repeatedly for a predetermined number of times and begins to undergo permanent deformation based on JIS H3130.
In the case of dynamic loads, based on the required service life, we will set it lower than the allowable bending stress.
Hello Banetto kun.
Thank you for your answer. Because I am just a Spring Newbie, I would like to ask you more questions as follows.
For example, when calculating a spring’s allowable range that is in a static contact state at all times, we will use the spring limit value if we know the allowable bending stress and proof stress, right?
In that case, it is not clear how to properly use the allowable bending stress and proof stress. Could you tell me how? Thank you.
Hello!
The allowable bending stress is used when calculating the tolerance of a spring that is in constant static contact. Generally, proof stress is not used. When repeated stress is applied, we will set the stress using the fatigue diagram according to the required service life. (The spring limit value is a value obtained by testing the spring for about 10,000 times, so it can be used after using the springs for about 10,000 times.) The proof stress is the mechanical property of the material and does not indicate the stress of the spring. And, the allowable range of flat springs is determined by the bending stress.
