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Curve fitting units

Re: Curve fitting units

I do sometimes so

piece.png

Re: Curve fitting units

There are a couple mistakes (I believe) in your note.  MJG is right, this is fatigue (I recognize the MIL-HNDBK-5 equation).  So we need to be careful about how we treat this, and about what the definition of cycles is.  Please look at the attached Prime 3.0 sheet.

Re: Curve fitting units

Borrowing on Fred's idea how about

cycles=1*Hz*sec

Math/label/unit

seems to work fine. Does anybody see a problem with this?

Re: Curve fitting units


wrote:

Borrowing on Fred's idea how about

cycles=1*Hz*sec

Math/label/unit

seems to work fine. Does anybody see a problem with this?


Well, Hz = 1/sec

 

so Hz sec is unitless. 

 

Because (for fft's) I need Hz for frequency of vibration due to a rotating shaft, I set "RPM = Hz/60" (note the caps!)  Then I get the correct numerical value for the fft resolved frequency.  I like this answer:

Capture.PNG

Re: Curve fitting units

Great. This is the new "DesKohlhepp Equation/Theory"

Re: Curve fitting units

Hi Fred.

 

I prefer 1 RPM = 2 Pi / 60 Hz and 1 rev = 2 Pi.

Best regards.

Alvaro.

Re: Curve fitting units


wrote:

Hi Fred.

 

I prefer 1 RPM = 2 Pi / 60 Hz and 1 rev = 2 Pi.

Best regards.

Alvaro.


Hmmm

so RPM =   rpm (already built-in)

And rev is a built-in and equals 2 pi.

Okay!

And cycle?

Re: Curve fitting units

For cycle I guess that cycle = 1. Because then for the electrical alternating current you have  that 60 cycles/seg = 60 Hz which agrees with the usual frequency.

 

Best regards.

 

Alvaro.

Re: Curve fitting units

cycle = 1

cycle  + % = 2 but must be an error

 

PS

In Mathcad 11

rad + sr = error (!!!)

In Mathcad 15 and Prime

rad + sr = 2 (???)

Re: Curve fitting units

in Prime % is a function, not a unit, so

Capture.PNG

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