lec. one bolted joints
DESCRIPTION
Lec. One Bolted JointsTRANSCRIPT
الرحيم الرحمن الله بسمDesign of Mechanical Systems
الكومي حسن محمد الدكتور اعدادالميكانيكي التصميم استاذ
االسكندرية – جامعة الهندسة كلية
5th Term Electromechanical Eng. ProgramLecture one
Bolted and Riveted Joints Fall 2015
Bolts and Rivets
Thread Terminology
Thread ClassificationsUnified National Standard ISO (Metric)
Thre
ad P
itch
UNC –coarseUNF –fineUNEF –extra fine
coarsefine
-¼20 UNF –2A
Class 2
20 threads/in.
d=0.25”
external threads
fine
M12 x 1.75metric
d=12mm
p=1.75 mm/thread
Tole
ranc
e
Class 1 Class 2Class 3
several levels
Thread Forms
Metric Marking for Steel Bolts Bolts
Torque Wrench
Statically Loaded Bolted and Riveted Joints
Ft = Fi + Fe
Fi : initial tightening load per bolt
Fe : external load per bolt
σ = Ft / A
σall = Sy / f.s.
σ : working stress
σall : allowable stress
Case I
Statically Loaded Bolted and Riveted JointsCase II
τ = F / A = P / A
σ = F / A = P / A
σbr = F / A = P / A
Statically Loaded Bolted and Riveted JointsCase III
r1
r3r2
r4
1
2
4
3
F1p : primary(direct) shearing load of bolt number 1
F1p = F2p = F3p = F4p = F / n
n : total number of bolts
M = (F1s×r1) + (F2s×r2) + (F3s×r3) + (F4s×r4)
(F1s/r1) = (F2s/r2) = (F3s/r3) = (F4s/r4)
M : twisting moment = F × L
F1s : secondary (indirect) shearing load of bolt number 1
F1 : resulting shearing load of bolt number 1
Statically Loaded Bolted and Riveted JointsCase IV
)F1/D (=) F2/d(
M = (F1×D) + (F2×d) O
Example 1
Example 2
Example 3
Example 4