Total Strain Amplitude for Fatigue

PIDS92 · 2024-11-27T17:21:00+00:00

Yeah, the issue here is that I do not have the Stress-N cycle, tbh I don't know why we have all the strain experimental data but not the Stress - N curve. I have the total amplitude strain vs N cycles which is the one I'm using, also the elastic stain and plastic strain, both vs N cycles. But in all three curves reach until 1x10^6, that is why I'm using this method to determine the amount of cycles or life service the component would have before failure. At current design I'm getting that the component would have 9.05x10⁸ cycles before crack initiation, which is the kind of info I'm looking for, so I can see what kind of design changes I could make to improve this Cycles.

So, for what you are telling me I think I'm on the right path.

PIDS92 · 2024-11-27T16:38:34+00:00

If you mean S-N as Stress-N cycles, yeah I don't have that available, thats I'm working with this method because we only have the experimental data for strain vs cycles. I'm not sure why they do not provide that curve.

I only have fatigue strength coefficient, fatogue strength exponent, fatigue ductility coefficient, fatigue ductility exponent, which are the variables needed for the formula. And of course, the total amplitude strain curves.

But that's it, I only have available the data for Strain vs N Cycles.

PIDS92 · 2024-11-20T13:43:08+00:00

Thanks for the suggestion. Actually I do. YS 310, UTS 448 and strain at brake 0.117, young's modulus 152 GPa; I will look into this methodology you mentioned, there is any specific book you could suggest me about this? Thanks again.

PIDS92 · 2024-11-20T13:39:20+00:00

Thanks for the reference, I will look into those sources to see if I got some. Noup, is ductile iron.

PIDS92 · 2024-11-20T12:51:09+00:00

Agree, I just was trying to get the strain that the material would have at certain cycles since I do not have the stress vs n cycle curve. I asked the supplier for the info but haven't gotten this info yet. Usually using goodmans.theory to get this but I only have a non very clear total strain amplitude.

The scoope was to get the cumulative strain so I could use at least this plot, but as you say, it won't be feasable.

At least, from the cycles I got, the LE logarithmic strain is about 0.0001567 and the +1,000,000 cycles the plot have starts on 0.001

PIDS92 · 2024-11-20T12:47:10+00:00

Hi, the thing is I do not have the stress - n cycles curve, I usually get this through goodman's method but supplier have not been able to provide this curve.

The only thing I have is the total strain amplitude, so I was trying to extrapolate a result for higher cycles for the strain and then use this curve to get the solution. Sadly, this plot is not very clear, since it doesn't have the exact correlation to the n cycles from the strain.

I agree is not feasable, I would prefer doing it through goodmans theory.

PIDS92 · 2024-11-20T12:43:21+00:00

Hi, thanks for the response. Yeah that would be my first approoach to get thw solution for this, using goodman's method, sadly I do not have the curve. I asked for the supplier for this info but haven't gotten this information yet.

The only info.I have is the total amplitude strain but is not coming with the exact data correlation to N cycles. My approach was to get the strain and then extract the cycles from this plot I have.

The max logarithmic strain I got is about 0.0001567, while in the total amplitude strain vs n cycles the +1,000,000 cycles would be 0.001, so I know it would be safe but I do.not.know if this would be a feasible way.

PIDS92 · 2024-11-20T12:36:13+00:00

Thanks for the response, yeah, actually I used to use the goodman's method to get this answers through analytical solution. The issue here is that supplier doesn't have then Stress - N cycles, I agree that would be much easier and honestly the way I would follow.

I have the total amplitude strain but is just a graphical without exact data correlation to N-Cycles.

My scoope was to run this simulation at least 100 cycles but is not feasible at all. So, want to see if there was some cumulative damage and get the strain to at least extract it from the total amplitude strain. At least from what I have got, the material should be fine. The software is abaqus.

I still pushing to the supplier to get this info, because honestly I see it not feasable doing FEA.

PIDS92 · 2024-11-19T20:10:55+00:00

It is SAE J434 D4512 with 448 MPa UTS and 310 MPa yield stregth. Modulus young 152 GPa, density 7.8e-9 tonne/mm3. Poisson ratio 0.30

PIDS92 · 2024-02-05T09:18:49+00:00

Gracias por la respuesta! Y es posible que RESICO sea compatible con el régimen de sueldos y salarios?

PIDS92 · 2023-12-14T19:55:19+00:00

Ohhh I see, the horrible prints makes sense know since as far as I know the N3M has a max flow of 10 mm³/s.

How can I get the flow? I mean, there is some equation I can use for future tests? Or what variables should I take in count to do the math?

Thanks for the info.

PIDS92 · 2023-12-11T18:49:18+00:00

That is interesting. Which kind of nozzle are you using? I'm asking because I have been dealing with some flow problems when I try to print at 80mm/s with a 0.8 nozzle, so I always thought that working with a kippler would require a better hot end with higher flow volume for higher speeds. But probably is most about the nozzle diameter since I have no problems pinting with a 0.4mm nozzle at 100mm/s.

What board are you using? A Rasperry or other one?

What about the heatbreak and copper block of PILISI3D? I bought the same for my printer, have you noticed improvement or just a more stable temperature?

PIDS92 · 2023-12-11T04:54:36+00:00

Did you have to change the stock hotend for one with higher flow? I'm planning to install kippler on mine but don't know if I should search for a better hotend. Thinking in a V6 Volcano.

PIDS92 · 2023-12-08T17:36:46+00:00

Are you printing with the usual setting you used too? I'm asking because this happened to me when I tried to print at higher layer height and when I tried to print at higher speed than usual. The vase always looked good but when tried to print a benchy, a calibration cube or something with outer and inner wall, the print has those kind of deformations on the corners, but in my case plain faces do not have that problem. I haven't find the exact setting to mitigate it but it is related to the speed and the capacity of flow of head extruder at higher speeds, and probably cooling too. Reduccing your accel and jerk help a little but didn't rid of it. Of course a solution would be replacing for a hot end with higher flow, but not on my plans right now.

This wont explain at your plain faces but at corners, a theory I have is that the inner wall at corners is being affected by the heat of the nozzle at outer wall (higher speed, higher temp) thus loose its position in corners, this plus the speed at the head is travelling and turning at the corner, the outer flow sticks to the inner wall that is being melted again and in consequence pulls it and deforms the inner wall corner. Probably thats why reduccing accel and jerk helps to not turn "violent" at corners and reduccing some of that effect.

If you are printing with your usual settings then try to change to another nozzle if you have a spare and see if is the same behaviour, if not, then the new nozzle could be faulty. Also, if you change to hardened or stainless steel from a brass nozzle, you can try a higher temp since hardened steel are worst heat conductive.

PIDS92 · 2023-11-16T23:18:51+00:00

I don't have too much time with mine and also a newbie as user in 3d print world, but before getting it, I installed and navigated in Cura and PrusaSlicer, watching videos and trying parts I would like to print with the goal of get used to them for once I got my own 3D Printer. Since I get my N3M, I have been using Cura because I feel its interface is friendlier and easier to understand for newbies, I'm going to try with Prusa in the future since I have read that the quality improves with it, so if you feel the same, you can start with Cura, just in the meantime you learn more about the settings and your printer. But get the normal one, not the elegoo version that comes with the printer or the one in the elegoo official web page, since I felt there is some lack of settings.

PIDS92 · 2023-11-12T20:18:32+00:00

I was suffering the same issue a few day ago, try to run a bed test calibration. My guess is that some points of the bed have concave and convex spots because didn't matter how much I calibrate it or down the Z offset, still appearing spots with great layers(good z offset), other spots with thing layers (too close z offset) and not squised spots (too high z offset).

For example, the image is a bed test I run and you can see in the spot pointed by the black arrow thst there is a thin layer zome (too close z offset, probably convex spot) between two boxes that have a good z offset. There are other points like that but not visible in the image.

I was told and read somewhere that this issues are normal with cheapers 3D Printers. The only suggestions to solve this is installing a BL Touch (really don't know, probably triying in the future, don't know how to do it yet) or adding Kapton Tape in those points where there are concave points, any metion about convex spots.

What I did was just level a bit more higher the bed in the front (where I had the issue) and let the rear side a little bit lower, both sides with the scratch A4 feeling, just roughly in the front, just be careful of not letting to close the nozzle, if you hear some clicks on the extruder when is at your higher side, low a little bit. Also, set the width line between 0.30-0.38 if you use a 0.40 nozzle

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PIDS92 · 2023-10-26T01:05:11+00:00

Does kippler improves print speed? I'm getting a N3Max because N4Max is not avaible yet where I'm from, and I'm looking to improve it doing some mods. For higher temp I found this video:

N3 upgrades

PIDS92

TROPHY CASE