ABSTRACT
As explained in Chapter 1, a dynamic force analysis (Figure 1.1) is the next type of force analysis to consider beyond a static force analysis when determining the structural forces in mechanical systems. Such an analysis should always be considered when angular velocities and accelerations are substantial (when mechanism motion is truly dynamic). Dynamic force analyses are also more general than static force analyses when mechanism motion is quasi-static. This is because, with a dynamic force analysis, acceleration-based forces and torques (however small in a quasi-static condition) are included.* In a dynamic force analysis, loads such as forces and torques are considered for each mechanism link according to Newton’s second law (∑F = ma, ∑M = Iα) [1-5].†
Unlike the static force equations in Chapter 6, the equation systems presented in this chapter consider the inertia, mass, velocity, and acceleration of each link.‡ Like the Chapter 6 equations, the equation systems presented in this chapter consider in-plane forces and torques, and mechanism links are considered to be rigid. Link weights are also neglected in the forthcoming equations because, as the acceleration of the links exceeds gravitational acceleration, the effect of gravity (and subsequently the link weights) becomes increasingly negligible. This condition is common in high-speed machinery.
