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  1. mirelavus

    Flat Spring Design Analysis

    I don't want any rotation to happen, so the first analysis looks closer to mine (which was around 80 LB/in, but I fixed it on y direction instead of giving it a zero value. Whahave you done for rotational constraints in the first case (analysis 1)? I fixed it on Dy and Ry. Maybe I would have to...
  2. mirelavus

    Flat Spring Design Analysis

    I run the optimization and after 11th iterations I stopped it, because it took too much time (already 2 hours). I got the stress down to 1147 MPa (1148 MPa is the yield point). I set the goal: maximize displacemets by keeping the stress < 1140 MPa (which is the yield point), by modifying almost...
  3. mirelavus

    Flat Spring Design Analysis

    Here is the second report, where I tried some of your sugestions. think i am getting closer. What do you think? I need stiffnes around 80-90lb/in at a preload height of .16".http://files.engineering.com/getfile.aspx?folder=cfcad96b-5d14-4a27-8e34-560704e02475&file=Spring_static2_Results_Report.zip
  4. mirelavus

    Flat Spring Design Analysis

    ok, I give up, would you mind giving it a shot? Here is the part. I am a bigginer in Mechanica so I don't really know what should I expect. I begin my learning with a difficult part...but it is what it is. Thank you much and I am looking forward for your...
  5. mirelavus

    Flat Spring Design Analysis

    Thank you for your input. That is true, I first applied some other boundery conditions, but then I try to give it another approach. By applying the force from the bottom and fix the bow, you can get the same animation. My conclusion was almost the same both ways: stiffnes=131 LB/in. I run...
  6. mirelavus

    Flat Spring Design Analysis

    I attach here my report and as you can see, the max displacemets are about 4 mm (.016"), so the stiffness will be: 92/4=23 N/mm (or 20.64/.016=131 LB/in). My hand calc shows only 43 LB/in with the same thickness. It is true that my hand calc idealize the section, which in reality is not a...
  7. mirelavus

    Flat Spring Design Analysis

    I already have this .pdf file (I've done a lot of research on this subject). The reason I do not follow what is written here is that I don't know if I should make these two contact plates in ProE like an assembly and use this assembly to study the spring in Mechanica, or should I use another...
  8. mirelavus

    Flat Spring Design Analysis

    And these are hand calculationshttp://files.engineering.com/getfile.aspx?folder=71f0db41-a234-47ba-986b-a22b48e65c92&file=Hand_calc.jpg
  9. mirelavus

    Flat Spring Design Analysis

    this is the spring designhttp://files.engineering.com/getfile.aspx?folder=695f6ead-62d8-4705-a6f3-856be2f71164&file=spring_design[1].pdf
  10. mirelavus

    Flat Spring Design Analysis

    PetieSmo the article was not found.It was probably removed. The problem is this: This flat spring has to push in some lugs that sit on a bladder. This bladder when inflated has 80 PSI. The area of the lugs is 2.58in^2.The spring sits between the lugs and a steel tube with 2" ID. Practically the...
  11. mirelavus

    Flat spring design FEA

    Also the coordonate systems are off a little as when I am printed graphics they do not start from 0 point. I also forgot to attach the new dims.http://files.engineering.com/getfile.aspx?folder=f81e8e53-7e39-485f-95c1-5b6dbb5a2b7c&file=spring_dwg_last.bmp
  12. mirelavus

    Flat spring design FEA

    Hi desertfox. I work with Pro Mechanica. Maybe my boundary conditions are wrong and/or edges that I selected for constraints are wrong, something is got to be wrong in FEA as we both have close foundings by different ways of hand calculations. Here is the last model.I used metric units (mm, N...
  13. mirelavus

    Flat Spring Design Analysis

    Hi all, I have to design a spring and test it using Pro Mechanica Wildfire 3. I don't know how should I approach the problem and what will be the boundary conditions. The spring sits between two curved areas. I will attach pictures. Thank you for your postings.
  14. mirelavus

    Flat spring design FEA

    I agree your calculations are fine, but I think we have asumed too much idealization to the real model. Thank you for your postings, very valuable. I concludes 36 lbs/in without cutouts myself by using some simple supported spring calculations and some beam idealizations. I think I have to start...
  15. mirelavus

    Flat spring design FEA

    desertfox, I've done FEA all day today and I modified the geometry of the spring including the free height, until I came up in FEA with a spring rate of 100 lb/in. I set the material thickness to .016 too, because this is the thickness of material I can get. I scooped it more in so now looks...
  16. mirelavus

    Flat spring design FEA

    I applied mass instead of force, meaning I applied 21 LBM instead of 202.96 LBF in my FEA calculations that's why my wrong calc. As soon I got a chance I can post pictures with FEA, but now I am at home. Thank you.
  17. mirelavus

    Flat spring design FEA

    I got my FEA to work, it was a unit problem, I had it wrong. The force was calculated wrong too. It does not have to support any load. The force is P*A=202.96lbf, so the load will be 21 LB. In FEA, I need to apply the foce at the center at the arch, not the load. Sorry about the confusion.
  18. mirelavus

    Flat spring design FEA

    That means I have to change the geometry of the spring. A=2.537in^2 (area of the curved spring)--from model P=80PSI (pressure inside the tube)--> F (force)=202.96 lbf--> Load = 21 LB. That is the minium force or load that I need at the preload length (.16"). At this point the spring has to...
  19. mirelavus

    Flat spring design FEA

    can you tell me how should I approach this problem? What do you think it should be approached?
  20. mirelavus

    Flat spring design FEA

    I ment to say unsuported beam (what is wrong with me?)

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