flat spring stock (source) (ti possibly?) 6

[JimBlackwood]

Hello all. New guy here. I build prototypes (usually mechanical but it varies) with concentration primarily in the automotive and agricultural fields. Right now I need to make a pair of leaf springs for a set of hinges to bias them in one direction and could use some help in finding a source for a suitable material in a small quantity.

The spring leaf will be 3/4"wide and can be about 1/16-1/8" thick. It will be approximately 6" long but that dimension can be varied for fine tuning. It will be clamped on one end up to within about 1" of the hinge pivot with the other end resting on the opposing hinge arm. The main issue is range of motion as the hinge will need to move through as much as 30-40°. The springs will be exposed to the elements so a corrosion resistant material is preferred such as a good grade of stainless or possibly a nickel-titanium alloy.

Regardless of the alloy chosen the range of allowable thicknesses should allow the spring to be tuned to the load so all I really need is a source that sells sheet or strip spring stock in an appropriate material. A strip only 1 ft long would be enough and I would have little need for more than 6ft of it.

Thanks for your consideration, I'm hoping this will be an easy one.

Jim

 

[KENAT]

JimBlackwood, how about a diagram of you situation? I realize due to IP issues it probably can't be complete but at least the 'free body diagram' of the spring aspects might help. As well as the actual diagram annotating the load (be it as torque or linear force at a given distance from your pivot) etc. will perhaps help.

You probably already know this but often for spring applications a 'softer' spring with a significant pre-load is better than a stiff spring with little to no preload.

http://www.tribology-abc.com/calculators/t14_9.htm

might give you a start in ball parking your situation or else

http://www.calculatoredge.com/mech/leaf_springs.htm.

There were plenty of results for a google search of "leaf spring calculations".

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[VEBill]

Is there an assumption that the spring material shall be metal?

Materials is not my area, but I've seen several cases where problematic metal springs were replaced with composite springs to meet challenging requirements.

Just a suggestion - nothing more.

 

[IFRs]

Getting bask to the 301 material not being suitable - full hard material should be darn hard to scratch while annealed material can be scratched with itself very easily. Maybe you did not get what you ordered?

 

[JimBlackwood]

The NiTiNOL would be operating in the superplastic phase. There may be other suitable Ti alloys, corrosion resistance would be a question. I will have another look at the 301 later today. This is my fall back position if the stainless does not exhibit adequate range of motion.[highlight #FCE94F][/highlight]

As much as I appreciate all the suggestions the design is set. What I need are small quantity online vendors so I can purchase the material. 440C or one of the other stainless alloys will probably work.

Jim

 

[NickE]

https://www.google.com/search?hl=en...1.2826.27j5.32.0.les;..0.0...1c.1.DFbs-tBfGnE

try those links

Nick

 

[IRstuff]

Nitinol that I'm used to has stiffness only above its SMA temperature. Below that, it behaves kind of like a wet noodle.

Again, a simple sketch of what you're trying to do would help everyone better understand.

TTFN
faq731-376

 

[israelkk]

CorBlimeyLimey

There is no superElastic condition at room temperature it can only exists when heated (usually to 70 to 90 Centigrade depends on the alloying of the Nitinol). Therefore, it is completely impractical in this case.

Over the last 30 years I have designed, developed and manufactured hundreds of different of springs over the whole range of spring types and materials with set remove and without it. For example: Helical compression and extension springs, linear and non-linear conical compression spring, helical torsion spring made of round and rectangular wire section, machined helical compression and torsion springs, belleville springs (linear, non-linear, snapped action, etc), torsion bars made of round and flat material, and other types. I have never needed to do any empirical trial and error, the manufactured springs always fitted the designed calculated spring within reasonable tolerances. The formulations for common springs analysis and design is well established for over the last 70 years (since Wahl). For other elastic members there is always the option of FEA and elasticity sound hand calculations and resources such as Roark.

 

[CorBlimeyLimey]

From

http://en.wikipedia.org/wiki/Nickel_titanium

In dentistry, the material is used in orthodontics for brackets and wires connecting the teeth. Suresmile is one example of an orthodontic application. Once the SMA is placed in the mouth its temperature rises to ambient body temperature. This causes the nitinol to contract back to its original shape, applying a constant force to move the teeth.

Average oral temperature is 36.8°C

With correct alloy composition & heat treatment, the transformation temperature of Nitinol can be adjusted between +100°C & -100°C. So, with the correctly spec'd alloy, superelasicity could easily be achieved at room temperature.

http://jmmedical.com/resources/122/...Nitinol-Shape-Memory-and-Superelasticity.html

 

[JimBlackwood]

http://www.designinsite.dk/htmsider/k0053.htm

 

[CorBlimeyLimey]

See also

http://www.nitinol.com/wp-content/uploads/2012/01/Material-Data-Sheet-Superelastic.pdf

from

http://www.nitinol.com/products-services/materials-sourcing

 

[JimBlackwood]

I have no desire to get personal. In response to criticisms that I have butchered the King's English, with one exception, easily interpreted correctly as pointed out, I have been extremely precise in my usage. Those who have dealt with the patent application process will clearly recognize this as a necessity, and those who have not will hopefully have that opportunity. I think I have presented the requirements in a wide enough variety of terminologies that none but the most willfully obtuse could fail to discern the intended meanings. But let's not go down that road. One of the problems with a trade language, and all professions have them, is that when you cross the boundaries to another profession the language does not mesh perfectly. Everyone here has experienced this and you all know that you cannot expect other professionals to adopt your most precise definitions any more than a doctor could expect you to learn Latin. So it behooves us all to broaden our vocabulary to encompass as many definitions of the words as we can. Sometimes this means we should accept more broadly defined terms than those which our own particular branch has chosen to interpret with a most stringent and strict definition but that broadens rather than restricting our understanding of the concept being conveyed to us.

For instance, some would think that Engineering and Art are diametrically opposed. But this is and has never been the case. Originally all engineering was by necessity artwork. The history of Engineering begins Empirically and it is this link that bonds engineering irrevocably to artwork. So it is that from a common root engineering took an analytical and practical turn while artwork progressed in the manner most pleasing to the senses, while their roots remaind eternally bound. Both disciplines make use of identical processesin all of their fundamental ideation and conception stages, and in their highest expression borrow freely from the processes of each other. So in fact Art and science, oe engineering have more similarities than differences.

 

[IRstuff]

Perhaps you should also stick to the problem at hand. SMA type nitinol is not particularly suitable for your, as yet still unclear, application. The fact that it can be "trained" implies that it, while not in the silly putty range of elasticity, is still quite deformable, and is therefore not particularly suited for spring-like applications. The only possibility would be if one were to apply electrical heating power to the strip to increase its stiffness as a function of the hinge position.

TTFN
faq731-376

 

[JimBlackwood]

Look guys, forget about it.

Jim