Abstract
This paper takes the crank-rocker mechanism as the research object, purposed for the simulation of the motion pair with clearance utilizing the contact force model and the coulomb friction model, we build the virtual prototype of four-bar mechanism with clearance joints in the ADAMS. The article mainly contrasts the influence dynamics characteristics towards the mechanism multi-joint clearance between the rigid rocker and the flexible rocker. Considering the jointed arm’s flexibility, the four, five and six order modal of the rocker, generated by ANSYS as a neutral document, were imported into ADAMS for simulation. The result shows that Mechanism with four joint clearance increased the impact on the speed and the acceleration appeared greater fluctuation, the flexible rod has a buffer effect to the contact-impact forces, and the dynamic characteristics of fluctuations are improved.
Highlights
As the existence of the joint clearance, the center distance between the shaft pin and sleeve is no longer zero, and resulted collision and friction of shaft pin and sleeve
When the shaft pin and the sleeve in collision, the contact force decompose into the normal collision force FN and the tangential friction FT
Ek,Q k,Rk represent Young’s modulus, Poisson ratio and contact radius of the object.δ is the collision depth.Collision index n can reflect the level of material nonlinearity, normal metal materials takes the number of 1.5.In ADAMS, transient damping coefficient is the step function of collision depth, the value of c is determined by the Step function
Summary
As the existence of the joint clearance, the center distance between the shaft pin and sleeve is no longer zero, and resulted collision and friction of shaft pin and sleeve. There are three kinds states of shaft pin: free state, collision, Continuous contact. When er, the shaft pin and sleeve generate collision. When the shaft pin and the sleeve in collision, the contact force decompose into the normal collision force FN and the tangential friction FT. The function of the collision between two objects is equivalent to a nonlinear spring-damper model. Ek,Q k,Rk represent Young’s modulus, Poisson ratio and contact radius of the object.δ is the collision depth.Collision index n can reflect the level of material nonlinearity, normal metal materials takes the number of 1.5.In ADAMS, transient damping coefficient is the step function of collision depth, the value of c is determined by the Step function. 0.01mm.Generally, friction coefficient data obtained from experiments, normal dynamic friction coefficient take 0.1, static friction coefficient take 0.3
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