You probably deleted the elements but kept the nodes with the constraints. These nodes are not necessarily connected to the model, resulting in the error. If the nodes of the refined model match the nodes of the coarse model, you could perform a coincident node check and keep the constraints...
Brad,
I don't understand your distinction between "independent of frequency" and "constant w.r.t. frequency". Perhaps you could clarify.
The damping force due to structural damping is equal to:
i*G*k*u
where i=sqrt(-1)
G=structural damping coefficient...
Chad,
In linear finite element analyses, there are three types of damping: (1) structural damping, which creates damping forces that are constant w.r.t. frequency, (2) viscous damping, which creates damping forces that increase linearly w.r.t. frequency, and (3) modal damping, which...
I once knew a guy who traveled all over the world "measuring" vibration levels in semiconductor facilities. When I analyzed the data, I found only peaks at 50 and 60 Hz. It turned out that he was using ICP accelerometers and forgot to turn on the ICP power supply in his analyzer!
pj
Mass Normalization means that each eigenvector is scaled to a unit value of generalized mass, that is,
(PHI-transpose)* M * (PHI) = 1.0
Where PHI is the eigenvector and M is the modal mass matrix. This is done in order to simplify computational and storage requirements in the finite element...
mpoc,
I cannot tell you the amplification factor without seeing some test data. I would recommend that you perform a test where you would put an accelerometer on the armature and subject the motor to a sine sweep in the frequency range of interest. This will give you the transmissibility of...
I think you can perform your thermal analysis, save the output and make the output set current, then go to Model, Load, From Output, and FEMAP will automatically define your nodal temperature loads. You should then use these nodal temperature loads in your structural analysis to perform a...
mpoc,
f = [1/(2*pi)]*sqrt(k/m)
where k = 620 lb/in
m = (1.3 / 386.4) sl
This yields a result of 68 Hz for the 1.3 lb mass. This is valid only if you can model the armiture as being supported on the preload spring as a single degree-of-freedom oscillator.
pj
mpoc,
Could it be that during vibration testing you are exciting the natural frequency of the armature on the preload spring? According to the numbers you are providing, the 1.3lb armature will vibrate at 68 Hz and the 2.2lb armature will vibrate at 53 Hz. If you can provide the value of the...
If you are performing a linear static analysis using the peak g-loading from the earthquake, and if you are calculating the steady-state thermal expansion, you can analyze the loads separately then combine the results in your post-processor. You could then determine the maximum allowable...
You should look at the stress gradients to determine which stresses look more reasonable. Keep in mind that the nodal stresses are average stresses obtained through the interpolation of the stress field defined by the element integration points.
In real life, there are plenty of applications...
Biomedman,
What you have "discovered" is a known singularity in the mathematical theory of linear elasticity that occurs at the interfaces of dissimilar materials (boundary layer effect). The singularity is due to the fact shear stress is being transferred between the two materials...
QCE:
No, I never said that engineering cannot change the world. The statement meant that engineering cannot (directly) change people's values. If someone feels that they can improve their quality of life with material things, it is engineering's role to supply these things.
You cannot...
