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Dynamic force analysis of a six-link planar mechanism under consideration of friction at the joints

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The dynamic analysis of mechanisms with joints friction is complex since the frictional force depends nonlinearly on the resultant reactive force between the two mating surfaces of the joint. In this paper a non-iterative approximate method is used for determining the joint reaction forces and the driving torque of mechanisms is considered. By using the computing program MATLAB the dynamic forces of a six-link planar mechanism are cakulated with this method. | Vietnam Journal of Mechanics, VAST, Vol. 26, 2004, No 2 (65 - 75) DYNAMIC FORCE ANALYSIS OF A SIX-LINK PLANAR MECHANISM UNDER CONSIDERATION OF FRICTION AT THE JOINTS NGUYEN PHONG DIEN AND NGUYEN VAN KHANG Hanoi University of Technology ABSTRACT. The dynamic analysis of mechanisms with joints friction is complex since the frictional force depends nonlinearly on the resultant reactive force between the two mating surfaces of the joint. In this paper a non-iterative approximate method is used for determining the joint reaction forces and t he driving torque of mechanisms is considered. By using the computing program MATLAB the dynamic forces of a six-link planar mechanism are cakulated with this method. 1 Introduction Improvements in the mechanical characteristics of machines consist typically of trends to enhance their productivity by increasing the operational speed. In mechanism that operates at high speeds , dynamic forces are often greater than static or other externally applied forces and play an important role in the design, sizing of links and bearings. The dynamic analysis of a mechanism reveals all the joint reaction forces, including the driving torque required to generate a prescribed steady state motion. It is well known that by application of D ' Alembert 's principle, a dynamic problem can be converted into a static problem. So, every member of a mechanism can be considered to be in equilibrium under the combined effect of all the externally applied forces , the joint reaction forces and its own resultant inertia force and moment . By neglecting frictional forces at the joints, the joint reaction forces can be easily calculated from the dynamic equilibrium equations, which are linear algebraic equations [1, 2, 5]. The dynamic analysis of mechanisms with friction at the joints is complex since the frictional force depends nonlinearly on the resultant reactive force between the two mating surfaces of the joint . These joint reaction forces dep end .