Page 297 - Modular design for machine tools

256 Engineering Design for Machine Tool Joints

observed, but it is more complicated than that of dynamic stiffness.
More specifically, the following should be stated.
1. The larger the in-phase component, the lower the quadrature com-
ponent; and both components increase by providing the oil at the
joint in the case of scraped cast iron joint.
2. The in-phase component increases and decreases with the excitation
frequency and oil viscosity, respectively, in the joint made of gray cast
iron. In contrast, the quadrature component decreases and increases
with the excitation frequency and oil viscosity, respectively.
3. In the joint made of cloth laminated bakelite, the oil viscosity shows
the opposite behavior to that for the joint made of gray cast iron.

In accordance with the reports of PERA, there is higher possibility of
improving the static and dynamic joint stiffness as well as damping
when the liquid polyisobutylene or antithixotropic polymer solution is
applied to the multiple-laminated joint. In this context, furthermore,
Groth [39] observed, by contrast, the larger increase of damping under
sliding up to 3000 mm/min in nearly all the bending and rocking vibra-
tion modes.

Single flat joint under higher preload and dynamic normal loading—
researches of Thornley and Koenigsberger [49] and Thornley and Lees [50].
Thornley and coworkers are thought to have conducted the first exper-
imental work regarding the dynamic behavior of the single flat joint.
They employed the test rig and measuring system shown in Fig. 6-29,
and the noteworthy feature of their test rig is a mechanism to apply uni-
formly the higher preload across the whole joint area. For this purpose,
the static preload is applied using the hydrostatic oil thrust bearing with
three pads. Following those studies of Thornley and coworkers,
Dekoninck [40] conducted certain experiments to expand the needed
knowledge using similar test rigs and experimental techniques. The
theoretical and experimental evidence reported by these earlier
researches indicates obviously that the dynamic behavior of the single
flat joint under dynamic load normal to the joint surface is, in nearly all
cases, identical to that of the multiple-laminated joint.
In the following, some representative behavior of the single flat
joint will be shown, focusing on the relevant effects of major jointing
factors.

1. Static preload. Figure 6-30 shows the effect of the static preload on
the dynamic stiffness. Although not shown here, the dynamic stiffness
of the joint under higher preload increases steeply with the preload,