文档介绍：Statics
静力学
约束与约束力
PART2 Constraint and
constraint Force
Bilingual Edition
Constraint and constraint force
Free Body: A rigid body can move freely in the space
Non-Free Body: The motion of the rigid body is limited by the constraint, it is impossible for such rigid body to move in some special directions
1、Free Body and Constraint
PART TWO
Constraint and constraint force
Constraint The limited condition to the rigid body’s position and velocity In engineering , the bodies which form the constraint are said to be constraint bodies,or constraint.
1、Free Body and Constraint
PART TWO
Constraint and constraint force
Constraint Force
The constraint limits the free motion of bodies, they change the motion status, so the constraint must bear the force from the body, at the same time, it also apply a force with same magnitude, opposite direction to the body, this kind of force is Constraint Force.
2、Constraint Force (Reaction force)
PART TWO
Constraint and constraint force
Positive Force
load (载荷),gravity force, wind force, pressure force, etc.
Passive Force
Constraint force
3、Positive force and Passive force
PART TWO
Constraint and constraint force
The principle of determining the direction of constraint force: The direction of constraint force is opposite to the direction of which the constraint can prevent the motion of the rigid body 约束反力的方向总是和约束体所能阻止的运动方向相反。
4、Principle
PART TWO
Coplanar Constraints
1. Flexible Cable (Negligible Weight)
PART TWO
This kind of constraint can limit the motion direction of the rigid body along the stretch-out direction
Coplanar Constraints
1. Flexible Cable (Negligible Weight)
PART TWO
Usually we use to describe the constraint force of flexible cable
Coplanar Constraints
2. Frictionless Surface
PART TWO
Direction of Constraint Force:
Along the normal line(法线) of the contact point on both the rigid body and contact surface
Pay attention: there is not any friction force on the surface.
We use to d