Re: Spring Design
Re: Spring Design
(OP)
Does anyone know of a good share/free ware program for spring design?
Thanks,
mikemkc
Thanks,
mikemkc
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
|
RE: Re: Spring Design
http://www.rentoncoilspring.com/design.html
Note that it does not include rate softening, or fatigue life.
Cheers
Greg Locock
RE: Re: Spring Design
As far as general guidelines go, I constructed my spreadsheet as follows (Shigley can help with this). My goal was finding the highest frequency spring that would fit in a particular package and still survive both static and fatigue loads:
inputs -
wire material, UTS, fatigue strength vs size info, density, shear modulus, max displacement, wire diameter, minimum fitted force, number of dead turns, min and max limits on force @ max displacement, package ID, package OD, minimum solid clearance
calculations -
for each of a series of values of force @ max displacement, I calculate the following:
spring index, mean diam, outer diam, inner diam, concentration factors, max working stress, max solid force
then I calculate max stiffness based on allowable solid force, max stiffness based on min fitted force, max stiffness based on allowable stress range
then I take the max of those three, which I call max allowable stiffness, and I output an indicator to show which limit was the most restrictive (fitted force, stress range, min force)
then based on my max allowable stiffness I calculate fitted force, fitted stress, stress range, fatigue cover factor, number of active turns, solid length, fitted length, solid force, and natural frequency.
the end.
Sorry, I can't share all of the equations.
RE: Re: Spring Design
The Bosch blue book and MIL handbook 5 are invaluable sources of fatigue properties for materials for springs, but you should also chat to your spring manufacturer.
One persistent issue I came up against was the rate softening under load - our spring supplier just didn't 'get' the idea that the actual rate at nominal design was my important parameter.
Cheers
Greg Locock