Two questions :
1.- What does mean cross-couple stiff and cross-couple damping?, How can be evaluated it in bearing supports?.

2.- Why cavitated bearing are named pi-film?. Isnt Attitude angle = pi/2 for this orbit position?
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How is the impact impedance method?, What could be to make to evaluate stiff and damping out of a laboratory?

1.- What does mean cross-couple stiff and cross-couple damping?, How can be evaluated it in bearing supports?.

Cross coupled stiffness refers to forces in an orthogonal direction generated by a displacement in a direction. Similarly, cross coupled damping refers to the forces generated in the orthogonal direction due to a velocity perturbation in a direction.

2.- Why cavitated bearing are named pi-film?. Isnt Attitude angle = pi/2 for this orbit position?

‘pi’ refers to the film being 180 degrees or pi radians. In general the attitude angle is not pi/2, but I don’t fully understand the question or point of this second part. Of course, the oil film will not in general be exactly 180 degrees. Otherwise, this might be used as the boundry conditions for a calculation on an oil film, 0 to pi -- cavitated region assumed not to contribute.

How is the impact impedance method?, What could be to make to evaluate stiff and damping out of a laboratory?

It is difficult to determine what is asked, but in general impact impedance methodology uses an impact device (hammer with force transducer on head) to excite a structure. Impedance is force divided by velocity; although in general, this type of parameter identification might be called an impedance method even if acceleration or displacement is measured.

Find the ROMAC site. They measure stiffness and damping on bearings.

William Foiles,
Thank you very much for your comment