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