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238 Engineering Design for Machine Tool Joints

the second loading cycle and beyond, i.e., progressive loop type.
Importantly, Masuko and his coworkers suggested that the hysteresis
loop is caused by the microslip at the contact asperities under the elas-
tic and plastic deformation. As a result, damping at the single bolted
joint can be characterized by its viscous—and dry frictionlike property
(see Chap. 7).
In the immediate previous research, Masuko and coworkers investi-
gated the joint behavior at first loading to observe the essential features
of the tangential joint stiffness [22]. Figure 6-15 shows the tangential

M8
Upper connecting
test piece
bolt
5 4 2 9 8
Displacement
detector of differential
transformer type f40
f20

7 3 1 6 10
Lower test piece Dead weight

40
Joint material: FC 25 = 1.0 mm 0.16
Tangential joint stiffness K s , kgf/mm 20 K s K d r P 0.08 mm Microslip d r ,
Joint surface: Ground, R max

s

P

d

0
0 200 400 600
Normal preload Q kgf
(a)
Figure 6-15 Tangential joint stiffness and microslip in varying normal preload: (a) For cast
iron joint and (b) for brass joint.