static force analysis

INTRODUCTION TO STATIC FORCE ANALYSIS

Free-body diagram

A free body diagram is a sketch or drawing of the body, isolated from the rest of the machine and its surroundings, upon which the forces and moments are shown in action. In case of the four bar mechanism shown in figure 1 the free body diagram

of link 3 is as shown below.

When a link or body is subjected to only two forces it is called a two-force member and when it is subjected to 3 forces it is called a three-force member. Similarly one may consider multi-force member also.

Static equilibrium: A body is in static equilibrium if

• the vector sum of the forces acting on the body is zero i.e., ΣF=0

• the vector sum of all the moments about any arbitrary point is zero i.e., ΣM=0