50
Bosch Rexroth AG
| Tightening Technology
3 608 870 A47
Nexo cordless Wi-Fi nutrunner
| 3 608 870 A47/2019-10
5.1
Design of a bolted connection
The planning of a tightening system starts with the definition of the tightenings that are to be implemented.
5.1.1
Clamp force and distortion of connected parts, operating forces
Fig. 5–1:
Deformation diagram with acting operating force
When a bolted connection is tightened, the mounting clamp force F
M
stretches the bolt like a tension
spring. The clamp force acts on the parts to be tightened (compression spring), pressing them together.
Normally, tightening stretches the bolt more than the parts are compressed.
During assembly, the mounting clamp force F
M
stretches the bolt by the amount f
SM
. Due to the tightening
forces exerted, the parts to be tightened are pressed together (compressed) by f
PM
.
If operating forces act on the bolted connection, the operating force F
SA
superimposes the mounting
clamp force F
M
. The bolt is additionally stretched by f
SA
while the compression on the material f
PM
is re-
duced by the amount f
PA
. The deformed parts are relieved by the axial force f
PA
, but the residual clamp
force F
KR
acting on the parts remains.
Basics on bolted connections and tightening technology can also be found in “Tightening Technology”,
ISBN 3-478-93073-1, Moderne Industrie publishers.
F
Force
f
Distortion
F
M
Mounting clamp force
f
SM
Elastic stretching of the bolt due to F
M
f
PM
Elastic compression of the joined parts
f
SA
Increase in elastic stretching of the bolt
f
PA
Decrease in elastic compression of the joined parts
F
S
Total force (mounting clamp force and operating force)
F
A
Axial tightening force
F
KR
Residual clamp force
F
PA
Axial force, relief of the deformed parts
F
SA
Operating force
F
F
M
F
SA
F
PA
F
KR
F
S
f
PM
f
SM
f
SA
= f
PA
F
A
f
