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Acceleration (Vibration) Of source unit in multiples if G 2
- Thread starter ninjaz
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BlasMolero
Mechanical
Dear Ninjaz,
G level is a "convenient" way to define an acceleration we use a lot in Dynamic analysis with NX NASTRAN, for instance in Response Spectrum Application usually the excitation curve is defined in G levels vs. frequency (Hz), or sometimes directly in real acceleration vs. frequency -- see the following image. Is also typical in Modal Frequency Response (SOL111) or Transient Dynamics (SOL112) with Enforced Base Motion with the structure being forced at a base node with a 1g sinusoidal (Seismic) loading condition.
But do not get confused, soon or later we enter in the FEA package the real value of acceleration used, ie, 1 G = 9.81 m/s2, (or the equivcalent value in the system of units used in the FE model). In the following picture we use Acceleration Scale Factor = 1.0 because the above excitation curve of response spectrum acceleration was defined in in/s2 vs. freq (Hz). Alternatively, you can define the excitation curve of acceleration in Gs vs. Freq. (Hz), and use an acceleration scale factor when defining the loading as 1G = 386.4 in/s2, then is up to you, we are talking the same all the time, OK?.
Best regards,
Blas.
~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director
IBERISA
48011 BILBAO (SPAIN)
WEB: Blog de FEMAP & NX Nastran:
G level is a "convenient" way to define an acceleration we use a lot in Dynamic analysis with NX NASTRAN, for instance in Response Spectrum Application usually the excitation curve is defined in G levels vs. frequency (Hz), or sometimes directly in real acceleration vs. frequency -- see the following image. Is also typical in Modal Frequency Response (SOL111) or Transient Dynamics (SOL112) with Enforced Base Motion with the structure being forced at a base node with a 1g sinusoidal (Seismic) loading condition.
But do not get confused, soon or later we enter in the FEA package the real value of acceleration used, ie, 1 G = 9.81 m/s2, (or the equivcalent value in the system of units used in the FE model). In the following picture we use Acceleration Scale Factor = 1.0 because the above excitation curve of response spectrum acceleration was defined in in/s2 vs. freq (Hz). Alternatively, you can define the excitation curve of acceleration in Gs vs. Freq. (Hz), and use an acceleration scale factor when defining the loading as 1G = 386.4 in/s2, then is up to you, we are talking the same all the time, OK?.
Best regards,
Blas.
~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director
IBERISA
48011 BILBAO (SPAIN)
WEB: Blog de FEMAP & NX Nastran:
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- #5
GregLocock
Automotive
Vibration is often measured in terms of acceleration, and obviously needs some units. 1 g is an acceleration of 9.81 m/s/s or 32.2 fpss.
Confusingly for the statically minded loads are oftem mentioned as being in g, for example I'd refer to a 0.9g load on a wheel. That merely means the weight multiplied by 0.9.
Newton says that's OK.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
Confusingly for the statically minded loads are oftem mentioned as being in g, for example I'd refer to a 0.9g load on a wheel. That merely means the weight multiplied by 0.9.
Newton says that's OK.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
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