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  1. hamsuplo

    Material properties of steel for spring

    Additional note: I'm mainly talking about the ends of the hooks of the springs (the cross sectional ends at the end of spring when its cut during manufacturing), is where the color change occurs. the body of the spring also changes color but slower - for example, by the time the hooks are...
  2. hamsuplo

    Material properties of steel for spring

    I have tested heating of springs at different temperatures and duration (i only know my steel is steel grade 70) I have noticed as temperature/duration goes up, the steel color turns from silver -> yellow/brass -> reddish/brown -> purple ->blue -> light blue I would like to know, for my...
  3. hamsuplo

    Hardness testing of spring material

    Thanks. Is the correction factor for the curvature added onto the hardness indicated by testing machine? How does one test the tensile strength of a 3.2mm diameter round wire? We have a tensile testing machine (with several different grips/clamps for different materials)... Most of the grips...
  4. hamsuplo

    Hardness testing of spring material

    What are ways to test the hardness or the quality of manufacturing/heat treatment of the spring? The problem with a normal hardness testing machine (eg a rockwell hardness testing) is that these are usually used for flat surfaces and will be difficult to make accurate on a round surface such...
  5. hamsuplo

    Spring stretching

    The springs are used for trampoline, are 5.5 inches in length from the ends and take up to loads of 55 kg before overloading.
  6. hamsuplo

    Wind vs Mesh/Netting force

    I have a Mesh with a 5mm hole, which during high winds/typhoons can have the effect of a sail. With the area of the net and size of the holes (maybe i can also figure out mesh thickness), speed of wind, how can I find the interaction between the net and wind? What is the approximate force of...
  7. hamsuplo

    Spring stretching

    Actually, all springs originally have same length and spring number 1 broke in the middle, same place where the irregular stretch is. No one uses any tools to bend or stretch them, and they are installed straight. They are intended to stretch uniaxially and must be assumed that they do, also...
  8. hamsuplo

    Spring stretching

    Hi, below are a few pictures of 4 damaged springs, let's say the spring on the left is 1 to the spring on the right is 4. Spring 2 stretches evenly so I believe it's manufacturing quality is good but has been overloaded. However spring 3 and 4 have irregular stretch in the middle so I think the...
  9. hamsuplo

    Spring Creep?

    Also another question, what happens to a spring if you don't heat treat it? Does this make the spring more likely to suffer creep?
  10. hamsuplo

    Additives and materials for swimming pool noodle

    Swimming pool noodles don't absorb water and are resistant to chemicals in the pool. I have a protective foam tube supplier, whose products deteriorates within weeks in exposure to UV light, but I have swimming pool noodles that seem to last forever. Since they are both foam I would like to...
  11. hamsuplo

    Spring Creep?

    the spring is 28coils, 3.2mm diameter, and standard steel i've looked up some information on relaxation/creep and it depends on the degree of stress, temperature and time, which is why it confuses me since the stress is low, the temperature is room temperature and the time is only 1 day. what...
  12. hamsuplo

    Spring Creep?

    I have an extension spring that is used (theoretically well below its yielding point) and used at room temperature. It is under constant loading (yield load is around 65kg~, constant load is no more than 10-20kg) and within one day it stretched out and didn't return to its original shape...
  13. hamsuplo

    Electrical resistance vs temperature

    You mixed up T1 and T2? You should use the same for each. R2 = R1[1+alpha(T2-T1)] = 6.179 ohms R1 = R2/[1+alpha(T2-T1)] = 6.179/[1+0.0039(20--40)]=5.007293
  14. hamsuplo

    Spring failure reasons

    hydrtools: Dimensions (alignment of the hooks), and that they are not broken/deformed before shipping. We also do small sample fatigue tests (100,000 cycles), and 50N tensile tests (the test results far exceed the requirement). These test results don't explain why the springs deform as they do...
  15. hamsuplo

    Spring failure reasons

    Tmoose: Not way to determine the time bad units were delivered, but most of the bad springs were produced the past year (returns started within the past year). Your test recommendations are good ideas; can you explain to me the Stretch Acceptance test, what would be the allowable Stretch and...
  16. hamsuplo

    Spring failure reasons

    drawoh: The springs are heat treated, but for 3-4 minutes (344 deg C) or 4-5 minutes (317 deg C), I don't know whether this is sufficient for steel-70. israelkk: The deformation during use is irrelevent, I have to assume that they are used as they were designed to. I need to know possible...
  17. hamsuplo

    Spring failure reasons

    Our product is trampolines, the spring is not meant to be loaded laterally but that doesn't mean that it wouldn't be. The springs are inspected before being shipped out, so the spring failure is not overloaded/yielded during the manufacturing stage, but during use. But I must assume that the...
  18. hamsuplo

    Spring failure reasons

    I have some returned springs that look like picture 3 and 4. There are many ways that the spring user could have misused it so that it turns into picture 3 or 4. But I have to assume that the spring user used it as meant to be used and that the failure is 100% due to the procedures before it...

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