Calculating safety factor on gear box support
Calculating safety factor on gear box support
(OP)
Hello guys,
I want to calculate the safety factor on container support design of gear box and I need your tips
The actual mass = 1600 kg
I assumed the mass to be = 2500 kg
= 2500 X 9.8 = 24500 N
The material is Steel A36 (Structure Steel)
So, I choose static structure, performed the mesh and remote force (24500 N) to be applied in the center.

and the result is:
Total Deformation

Equivalent Stress

and the F.O.S equation will be:
F.O.S = max. strength / Design load
= 2500 (kg) / 668.73 (MPa)
= 3.73 > 1
I'm hope my calculation is right
Please if you have any tips or comment, share it with us
Thank you so much for your time
I want to calculate the safety factor on container support design of gear box and I need your tips
The actual mass = 1600 kg
I assumed the mass to be = 2500 kg
= 2500 X 9.8 = 24500 N
The material is Steel A36 (Structure Steel)
So, I choose static structure, performed the mesh and remote force (24500 N) to be applied in the center.

and the result is:
Total Deformation

Equivalent Stress

and the F.O.S equation will be:
F.O.S = max. strength / Design load
= 2500 (kg) / 668.73 (MPa)
= 3.73 > 1
I'm hope my calculation is right
Please if you have any tips or comment, share it with us
Thank you so much for your time





RE: Calculating safety factor on gear box support
And what do you mean by FOS equation?
Best action you can take now is to remove the force fron your model, apply a 9.8N/kg gravitational acceleration in the gravity direction. and check the von mises stress by dividing your Ftu (ultimate tensile material allowable) by the von mises stress you get from the analysis:
Ftu/vonmisesstress
This is what you are trying to achieve and you may be a atudent :)
Spaceship!!
Aerospace Engineer, M.Sc. / Aircraft Stress Engineer
RE: Calculating safety factor on gear box support
No I'm not student, I'm mechanical engineer who is working as quality assurance for period of time, so I may forget some information about mechanical design :)
FOS is Factor of Safety
I'll try gravitational acceleration and post the result today
And where I can find similar analysis?
RE: Calculating safety factor on gear box support
For a static load, the factor of safety is ultimate stress / working stress. Not sure why you include mass? If you don't want your part to deform permanently, your ultimate stress should equal the yield stress. Then your factor of safety is 250/669 = 0.37.
This all assumes that your mesh is adequate and your loads/BC's are appropriate.
RE: Calculating safety factor on gear box support
RE: Calculating safety factor on gear box support
I don't know why I divide the weight over max. stress
I saw a solved example from engineering design book and the weight was the same value as the yield stress, so I took it and it was totally OFF
and part of me was not sure about it and that's why I asked for your help.
Now,
I agree with you Dave >> Factor of Safety = ultimate stress / working stress = 250 / 668.72 = 0.37
What does that tells me? Is the design not safe at all? OR the load will cause permanent deformation and can be usable?
Because I copy the design of the finder (original Manufacturing) same design, material and thickness.
Also, in my company they used this support for long time without an issue (talking about more than 20 years)
but in short of the quantity, we're trying to fabricate a new one
So I'm waiting for your input guys
Thank you
RE: Calculating safety factor on gear box support
According to google, the ultimate tensile stress for your material (steel a36) is 400-550 MPa. If you have full confidence in your FEA model (geometry, mesh, element formulation, constraints, loads, application of loads, solver controls, assumptions etc.) then your FEA results indicate that this device will fail in service.
In reality, this part has been used for a long time without issue. This suggests that there are issues with your FEA model and the 668.72 MPa peak stress that you are predicting is non-physical. This could be caused by any number of modelling assumptions/errors.
Before you trust your FEA results you need to perform some validation. Load the device in a lab and measure the deflection at a specific point. Repeat this test with an FEA model and see do you produce the same force-displacement. This will give you confidence in your FEA results (or confirm that your model has issues).
Good luck,
Dave
RE: Calculating safety factor on gear box support
- Check your dimensions are correct
- Check your geometry is discretized using an adequate number of elements
- Check your geometry is discretized using an adequate element formulation
- Check you have assigned an appropriate material model
- Check are the material parameters consistent with the assumed dimensions
- Check is the loading representative of that observed in reality
- Check is the loading consistent with the assumed dimensions
- Check are the constraints representative of those observed in reality
- Check is the type of solution you have used appropriate (static/dynamic etc.)
- Check influence of stabilization/damping if present
- Check for post-processing errors
DaveRE: Calculating safety factor on gear box support
RE: Calculating safety factor on gear box support
The assumed weight I think is much higher (2500 kg)
In the Technical Manuel the gear box weight is 1117 kg
So I will assumed 1400 kg (The whole weight of the container + Support + Gear Box = 1400 kg per to TM)
So, The results are:
Factor of Safety = 250/231.11 = 1.08
and the max. working stress on this spot:
In reality it will stand on rubber absorber base which its size is twice bigger than the hole size
so maybe the max point are nonphysical.
What do you think?
RE: Calculating safety factor on gear box support
Its hard to comment on your results without knowing all the details of your model. One thing I would suggest is to run a mesh sensitivity study. From your images your mesh/contours look quite coarse. It looks like your primary loading mode is bending and you only have 2 elements through the thickness of the member with the peak deflection. Depending on the element formulation you have used, more elements may be required in this region to adequately capture bending effects. Also, I would try to perform some validation.
Good Luck,
Dave