I always visit your homepage and use it as a reference for designing. Currently, we are designing flat springs for the first time. It is used where static loads are continuously applied (for example, about 10 years).
Q1: Is there any problem with the following design concept?・ Allowable bending stress = 75% of tensile strength ・ Working stress = 80% of allowable stress
Q2: SUS301-CSP and SK85 are under consideration for materials. Please tell us the allowable bending stress of each. (If it differs depending on the processing method, please tell us about each individually)
Q3: While ensuring a certain amount of deflection against static load, we are struggling with the design and material selection considering stress. Are there any recommended materials other than the ones in Q2? If you have any materials in mind, please tell us the allowable bending stress.
Thank you in advance for your reply.
Spring Newbie, thank you for posting!!! We will answer your questions as follows.
Q1: Is there any problem with the following design concept?
・ Allowable bending stress = 75% of tensile strength
・ Working stress = 80% of allowable stress
Answer:
・ Allowable bending stress = 70% of tensile strength.
・ Maximum used bending stress = 80% or less of allowable bending stress
Q2: SUS301-CSP and SK85 are under consideration for materials. Please tell us the allowable bending stress of each. (If it differs depending on the processing method, please tell us about each.
Answer:
・ For SUS301-CSP 3/4H (Available material) Allowable bending stress is 791N / mm2.
・ For SK85, the bending stress is different according to the specified hardness range. If the specified hardness range is HRC42 to HRC48, the tensile strength of HRC42 will be about 1340N/mm2, so the allowable bending stress will be about 938N/mm2.
Q3: While ensuring a certain amount of deflection against static load, we are struggling with the design and material selection considering stress. Are there any recommended materials other than the ones in Q2? If you have any materials in mind, please tell us the allowable bending stress.
Answer ・SUS304-CSP H: Allowable bending stress is 791N/mm2.
・ We think SK85 is good for strength.
Thank you for your answer.
Would you please answer one more question? We are looking for a material with a low Young’s modulus and high allowable bending stress, although this is answered in Q3 already. I thought that beryllium copper (Precipitation hardening) would be good, but if there are other good materials, please let me know. We would also appreciate it if you could tell us about the allowable bending stress and Young’s modulus of the material too.
Thank you for your cooperation.
Spring Newbie, thank you for your question!!!
We will answer your questions as follows. It is as you think, beryllium copper (Precipitation hardening) is the best material with low Young’s modulus and high allowable bending stress. Allowable bending stress of beryllium copper C1720R-1/2H is 868N/mm2 and Young’s modulus is 127000N/mm2.
