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DYNAMICS OF MACHINES. To know the purpose for which the m/c is needed. To develop concept design . To analyze the motion involved - Kinematics To calculate & analyze the forces and torques required for producing the motion
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DYNAMICS OF MACHINES • To know the purpose for which the m/c is needed. • To develop concept design. • To analyze the motion involved - Kinematics • Tocalculate & analyze theforces and torques required for producing the motion - Kinetics • To give physical shape to the components. - Machine Design
STATIC FORCE ANALYSIS IN MACHINES • To evaluate the forces acting on the machine members at a particular configuration. • Each configuration is considered as system of rigid bodies in static equilibrium under the action of external forces. • Helps in finding load carried by each part of the machine during cycle of its operation
TYPES OF FORCES • Applied forces : Gas, hydraulic & pneumatic forces etc.. Electrical, magnetic & gravity forces • Constraint forces : Reaction forces. • Friction forces. • Inertia forces. Due to mass of accelerating parts
Condition for static equilibrium F1 • ∑ F i = 0 • ∑ Mi = 0 F2 M/c part CG F5 F3 F4
EQUATIONS FOR STATIC EQUILIBRIUM Fi = 0 M i = 0
EQUILIBRIUM OF TWO FORCE AND THREE FORCE MEMBERS Two force member in equilibrium F2 F1
THREE FORCE MEMBER IN EQUILIBRIUM F1 F1 F2 F2 O O F3 F3
STATIC FORCE ANALYSIS IN SLIDER-CRANK MACHANISM A 3 2 4 FBDof Link 2 O2 P 1 B C12 2 F32 F34 F12 4 P F34 F23 FBDof Link 3 F14 A P F14 3 FBDof Link 4 B F43
STATIC FORCE ANALYSIS IN 4-BAR MECHANISM F34 O B 3 A F14 C 4 4 2 P F14 P P F34 O2 O4 F43 3 F32 h C12 F23 F12 O2 C12 = F32 X h
O2 P 6 5 C B 3 6 P A 2 F56 5 C O2 4 F16 1 P F16 O4 F56
F65 5 F45 C O F54 F54 LINE OF ACTION OF F34 F14 3 F34 LINE OF ACTION OFF14 4 F32 A 2 F43 3 C12 F23 O2 F12
Inertia force - m a • Inertia torque - I α
D’ Alemberts principle In order to find the effect of inertia of the actual link on the forces transmitted to the adjacent links of a mechanism, the actual link may be replaced by a rigid mass-less link to which inertia forceF i = -ma is applied. The mass-less link is then under equilibrium under systems of forces along with inertia force.