stress analysis on bracket 2

[Spike2000]

Forum Folks
see attached...i have a bracket w/1500 psi of pressure hitting the point shown
it is held in place with the static pin also as shown
we need this bracket to deform slightly yet not "bend" out of shape.
the bracket is .730" thick...everything is in inches
as of right now this thing does not budge...the question is what do i need to change .395 to, in order
for this bracket to deform while installing yet not pass the modulus of elasticity?
i don't expect a sure fire answer here, just a direction or software, a formula....something to get
this off the ground...material is 304ss by the way

thank you in advance

 

[FEA way]

You don't have to worry that the stresses will exceed material's elastic modulus. For steel it's 210 GPa and you'll never reach such a high stress because the bracket will be broken way before this value. Do you need an elastic deformation (reversible - when you remove the load it will go back to previous shape) or plastic deformation (irreversible - once deformed it won't go back) ? For the former you should make sure that the stresses won't exceed material's yield strength (about 205 MPa for 304 steel) and for the latter you should increase the stresses so that they go beyond the yield strength.
How can you know how high the stresses will be ? Well, mechanics of materials is the answer. Because of complex shape it's not possible to calculate it analytically with formulas but you can use a simple Finite Element Analysis software. In your case I suggest using some CAD-embedded FEA. You can find stress analysis modules for example in Autodesk Inventor, SolidWorks or CATIA.

 

[JStephen]

You may need better definition of the problem. I think that if you do an adequate analysis, you'll find that you get very high stresses in very small areas (inside corners, for example)- so you may technically have yielding at some point, but not plastic action of the whole bracket.
Note that anything whatever will deform "slightly" with any force whatever- there's not any infinitely stiff substance around.
Also be aware that stainless steel can have a fair bit of variability in its yield strength, and once yielded, may have ultimate strength much higher than yield- so behavior may not be what you're expecting.

 

[hydtools]

What is the load in terms of force and direction?

Ted

 

[BUGGAR]

Not sure what you are doing there but could you take the deflection/force in a bellville spring or similar that connects the parts? Or even a load indicator washer?

 

[dhengr]

Spike2000:
Where did you get the 1500psi? I doubt that number, that force?, would be shown that way, with those units. That arrow/vector should have a force value, explicit application point on that upper knob and a direction of application. The bracket looks kinda like a hook or a “C” clamp, or a latch of some sort, problems we have had solutions for, or at least dealt with, for many years. As a solution to your problem, the stress levels in that bracket may not be as important/critical as the way the bracket deflects under load. You should start by defining your problem with enough specificity so that an experienced engineer had a chance at understanding what you were actually trying to do. Most of the good engineers here on E-Tips don’t want to play 20 questions for the next two weeks, you’ve got to give a few meaningful hints and details if you want meaningful help.

 

[GregLocock]

1500 psi as a point load is zero. dhengr has it.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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

 

[rb1957]

yes, stress needs to be applied to an area. Since the obvious area is curved the simple thing would be a force acting thru the lug center represented by a (radial) stress applied to the surface.

where is the other reaction reaction point ? Normally a pin as shown would not react torsion (from friction under the head), and since the applied load is not aligned to the single restraint shown the part will rotate until it bears up against something.

is this rotation the "deformation" that you "need" ? Why do you Need this brkt to deflect/deform under load ?

another day in paradise, or is paradise one day closer ?

 

[kjoiner]

It reminds me of one other combined stress problems such as on a press. You need the section modulus of the bracket at the .395 location and then combine the axial and bending stresses. The issue is that your section is not uniform and the smaller sections will deflect first. I agree that FEA might be the best (and quickest) way to get your answer.

https://www.mathalino.com/reviewer/strength-materials/problem-908-combined-axial-and-bending

Is this some type of "snap fit" where you want to rotate the bracket and have it lock into place?

Kyle

 

[hydtools]

You will want to look at curved beam analyses, like hooks as mentioned.

Ted

 

[Spike2000]

thank you everyone for your responses
this will help get me going, i cannot show you the complete assembly as the assembly has a pattent
FEA Way - yes plastic deformation is the goal here, thank you for the info.
i am struggling with "Elmer" software, but if there is another FEA software anyone can suggest that would be great.
Kjoiner, you are right this is a snap fit rotating bracket.

regards

 

[hydtools]

Can you engage the mating part into the hook and force the mating part to finish the engagement to the surface near the static pin? This may require less deflection and still have the friction fit. This may not make sense since I don't know about the undefined parts.

Ted

 

[chicopee]

I just wish that the drawing was more complete, another word the drawing should show how the bracket is supporting the load or how it is attached to the load, otherwise I find it to be an exercise in futility to answer on an incomplete assembly drawing that involves this bracket. Hytools has in my estimation may have a satisfactory answer with the curved beam analysis but there are several other questions being: 1) is the pin hole design adequate for the load 2) where is the 1500 psi pressure acting on the bracket 3)Is there any seismic requirement 4)temperature fluctuation involved 5)any vibratory forces involved--you get the idea.