文档介绍：Statics
静力学
平面力系简化
Resultants of
a coplanar force system
Bilingual Edition
Changing the line of action of a force
Changing the line of action of a force
PART FOUR
How to change the line of action of a force without affecting its external effect on a rigid body?
It consists of the following steps:
Changing the line of action of a force
Couple of transfer (附加力偶)
PART FOUR
We refer to the couple M as the Couple of transfer.
The couple of transfer is equal to the moment of the original force (acting at B) about the transfer point A
Reduction of a coplanar force system to a force and a couple
Procedure of Reduction
PART FOUR
1) Consider the coplanar force system show in the figure
2) Move each force to an arbitrarily chosen base point O,we will obtain the following figure:
Reduction of a coplanar force system to a force and a couple
Procedure of Reduction
PART FOUR
1) Because the forces are now concurrent at point O, they can be added to yield the resultant force F’R,that is:
2) The couples of transfer can also be added, because the forces are coplanar, then :
Reduction of a coplanar force system to a force and a couple
Principle Vector and Principle Moment
PART FOUR
1) We refer to the resultant force of a coplanar force system as the Principle Vector (主矢)—FR’
1) We refer to the scalar sum of couples of transfer as the Principle Moment (主矩)—MO
Reduction of a coplanar force system to a force and a couple
Principle Vector and Principle Moment
PART FOUR
1) The magnitude of Principle Vector is not related to the arbitrarily point O, because:
2) The value of Principle Moment is related to moment center point O, because Mi is different to various moment center point.
Reduction of a coplanar force system to a force and a couple
Cantilever Support (Built-in constrains)
PART FOUR
The Cantilever support (Built-in) (固定端约束) is widely used in engineering, because of plex reaction force, we have to reduce it to a simpl