Page 262 - Modular design for machine tools

Engineering Design Fundamentals and Single Flat Joint Characteristics 221

TABLE 6-4 Values of C and m for Nonmetallic Materials (in Part, Calculated from
Data of Eisele and Corbach)

Type of surfaces in contact C m Remarks

Bronze (SnBz8), 0.3 0.65
scraped
Cast iron (GG26), MoS 2 compressed 0.52 0.85
scraped
Polyamide 8.8 0.35
Backlite laminated 11.0 0.5 Valid range of p:
woven clothes 2.0–7.5 kgf/cm 2

Turcite, scraped Reported by
Cast iron, ground = 30 mm) 2.0 0.6
(R max Furukawa, Tokyo
(R max = 2 mm) –
Turcite, ground 1.4 0.7 Metropolitan Univ.,
(R max = 6 mm) elsewhere
2
2
Note: Values of C and m are available up to 6 kgf/cm and when l and p are in mm and kgf/cm ,
respectively.
can be seen, the value of m is not 0.5, but is less than 0.5 in the case of
the plastic material and more than 0.5 in the cases of bronze and MoS 2 .
In addition, it is noticeable that MoS 2 compressed material and bake-
lite of woven clothes laminated type show some peculiar characteristics,
although both have relatively low joint stiffness: the former shows a
large value of m, but the latter shows a large value of C compared with
those of other joint materials.
In addition, further noteworthy behavior can be observed as follows.

1. Apart from certain kinds of nonmetallic joint and joints of laminated
type, the interface pressure–joint deflection curve does not show any
hysteresis, even when the loading and unloading procedures are
repeated.
2. The joint stiffness is in proportion to the modulus of elasticity of the
joint material. With the increase of the modulus of elasticity, the
joint stiffness becomes higher.
3. With improving surface roughness, the joint stiffness increases, pro-
vided that the joint surface has no flatness deviation and/or waviness.
4. In the cast iron joint, its surface roughness has no effects on the joint
stiffness.

In many respects, it is very desirable to apply the expression of
Ostrovskii to the joint under higher interface pressure, and from such
a viewpoint, Taniguchi et al. [10] investigated the further availability