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Failure of Tribo-Systems
Published in Ahmed Abdelbary, Extreme Tribology, 2020
Cam/follower systems are used in most internal combustion engines to provide a prescribed motion to a valve train system. The cam moves on its follower in extreme and complex contact conditions of high temperatures, no lubrication and high contact stresses. Consequently, the performance of a cam/follower system is highly affected by the contact conditions. It is believed that failure from contact stresses generally leads to localized deformation or fracture by the progressive spreading of a crack (Tounsi et al., 2011). Pitting is a fatigue process that can also cause initiation and propagation of cracks. Rolling contact fatigue (RCF) cracks of the cam/follower system can be categorized into two groups, based on where they started. First, cracks that initiated at the surface and propagated down into the bulk of the cam at a shallow angle to the surface, or cracks initiated below the surface. Second, cracks which initiated in a region of maximum cyclic shear stress. An experimental and analytical research on contact fatigue wear of cam and roller follower performed by Cheng et al. (Cheng et al., 1994) indicated that the end clearance between the roller and rocker had a significant influence on friction and heat generation in the roller follower surface.
Prototyping of automated systems
Published in Fuewen Frank Liou, Rapid Prototyping and Engineering Applications, 2019
A cam mechanism as shown in Figure 8.60 usually consists of two moving elements, the cam, and the follower, mounted on a fixed frame. A cam may be defined as a machine element having a curved outline or a curved groove, which, by its oscillation or rotation motion, gives a predetermined specified motion to another element called the follower. The cam has a very important function in the operation of many classes of machines, especially those of the automatic type, such as printing presses, shoe machinery, textile machinery, gear cutting machines, and screw machines. A cam can be used to convert rotary motion into designed motion. The motion created can be simple and regular, or complex and irregular. A cam is driven by the circular motion, it turns, and the cam follower traces the surface of the cam transmitting its motion to the required mechanism.
Bearings, Slides, Guides, Ways, Gears, Cylinders, Couplings, Chains, Wire Ropes
Published in Don M. Pirro, Martin Webster, Ekkehard Daschner, Lubrication Fundamentals, 2017
Don M. Pirro, Martin Webster, Ekkehard Daschner
There are many cases in machines where rotary motion must be converted to linear motion. Where the linear motion required is comparatively short, a common method of accomplishing this is with a cam and cam follower combination (cam follower is sometimes referred to as a tappet). Probably the best known applications of these mechanisms is for operating intake and exhaust valves in a reciprocating internal combustion engine, but many other applications also exist. As the cam will only lift the cam follower, some arrangement must be made to keep the cam follower in contact with the cam. This may be accomplished by transmitting load from the mechanism being actuated, or directly with a loading mechanism such as a return spring.
Improving the performance of industrial machines with variable stiffness springs
Published in Mechanics Based Design of Structures and Machines, 2022
Tom Verstraten, Pablo López-García, Bert Lenaerts, Branimir Mrak, Dirk Lefeber, Bram Vanderborght
The simulations revealed that the PEA requires a locking mechanism in order to limit the energy consumption during the dwell periods of the motion. To generate a double dwell period, the setup is equipped with a cam-follower mechanism. Cam-follower mechanisms have been utilized for ages in different types of machinery to create this type of dwell motion (Adanur 2000). They have also been implemented in PEA designs for active prostheses with the aim of shaping the linear torque-angle characteristic of the parallel spring to a more desirable nonlinear characteristic (Realmuto, Klute, and Devasia 2015; Gao, Liu, and Liao 2018). Compared to a discrete locking mechanism such as e.g., a controllable clutch, the cam-follower mechanism has the distinct advantage that it smoothens out the acceleration profile. Moreover, it is completely passive. The downside is that their strongly nonlinear characteristic presents some serious additional challenges in terms of control.
Numerical model proposed for a temporomandibular joint prosthesis based on the recovery of the healthy movement
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
Henrique Takashi Idogava, Pedro Yoshito Noritomi, Gregory Bregion Daniel
In order to allow a comparison with the responses of a healthy mandible available in literature (Missaka 2010; Mesnard et al. 2012), the rotation and translation functions were analyzed together to represent the real movement presented in the TMJ. For this, forms of planar mechanisms were analyzed as a solution alternative, allowing the visualization of the trajectory adopted. The mechanical system used in this application is based on Cam-Follower Mechanism, in which the cam is a solid body formed in such a way that the movement of its trajectory defines the movement of the second body attached to it, the follower (Doughty 2001). The cam provides a similar form of movement in which an analogy can be made to the analyzed system.