1 ME 302 DYNAMICS OF MACHINERY Virtual Work-Energy Methods Dr. Sadettin KAPUCU © 2007 Sadettin Kapucu

Gaziantep University 2 VIRTUAL WORK-ENERGY METHODS Newton method provides complete information about all interior forces at pin joints as well as about the external forces and torques on the mechanisms. One consequence of this fact is the relative complexity of their application which requires the simultaneous solution of large system of equations. Energy methods for solution of these problems are easier but it gives less information. Only the external, work producing, forces and torques are found by these methods. The internal joint forces are not computed. One chief value of the energy approach is its use as a quick check on the correctness of the Newtonian sol’n for input torque.

Gaziantep University 3 Example 1 Find the magnitude and direction of the moment must be applied to link 2 to drive the linkage against a 100 N force at the point E of the link 4 as shown. Use virtual displacement method AB=DE=2.5 cm, DC=4 cm, BC=5.7cm

Gaziantep University 4 Example 1

Gaziantep University 5 Example 1

Gaziantep University 6 Example 1 We need the ratio of This ratio can easily be found from instantaneous velocity analysis.

Gaziantep University 7 Example 1