The influencing factors on the stick-slip induced phenomenon and its prediction on large structural systems

As technical systems evolve they contain an increasing number of components with many mutual interactions. In order to properly tune and control each system it is essential that one understands the component interactions and how they are affected by the system. One of the most typical interactions in mechanical systems is the one that is established when two components are connected via a joint based on dry friction. In recent years the mechanical systems associate with vehicles and other structural systems have become more silent than in the past. As a direct result of this, the discontinuity feature associated with the dry friction joints has created a comfort-related condition known as low speed clunk, or more precisely stick-slip. This situation can be described as the intermittent motion between the components of the joint at low speeds. Utilizing self-excitation vibration theory, a controlled laboratory test rig was built to determine the main factors that influence the occurrence of the stick-slip in a specific system. A mathematical model of the test rig was formulated and solved numerically. The solution from the mathematical model was then compared with experimental measurements from the test rig. This comparison demonstrated the ability of the model to predict the behavior of the test rig. The mathematical model was then adapted to simulate the stick-slip occurrence in a vehicle system. Field tests were performed on the vehicle systems and the results were compared with the results obtained from the model. The comparison indicated that there was good agreement between the model and the field tests performed on the vehicles. The results demonstrated that the stick-slip is a very sensitive phenomenon that does not occur at the component level. The stick-slip phenomenon was found to be very dependent on the parameters of the system where the dry friction component is located. The results also indicated that the system stiffness, the normal loads, and the delta friction are the three variables that had the biggest effect on the occurrence of the stick-slip phenomena. These findings suggest that a particular dry friction joint could produce intermittent motion in a system with certain system parameters, but the same joint would have a smooth and periodic motion in another system with slightly different system parameters. The mathematical model proposed in this work can be used to analyze and predict potential stick-slip occurrences in other systems once the parameters of the system are accurately measured.