Rolling contact is a mechanical phenomenon where rolling bodies or surfaces contact each other, with zero relative velocity. It underlies many mechanical processes, but can cause fatigue and failure in bearings. Research examines conditions for failure and how to design bearings more effectively. Rolling contact has been used for a long time, including the log roller.
Rolling contact is a mechanical phenomenon involving rolling bodies such as wheels or bearings contacting each other, or surfaces such as roadways. At the point where they meet, the relative velocity is zero. This underlies a wide range of mechanical processes, from the toothed gears used in automobiles to conveyor belts. Researchers study the physics behind rolling contact because it provides important information about how and when bearings fail. It is a special type of mechanical wear.
In a simple example, two bearings can roll against each other to allow a joint to articulate and move. When they change position, they make rolling contact. This point can have a relative velocity of zero, but the deformation can be very large, because the force is concentrated there. As a result, rolling contact fatigue tends to develop on bearing surfaces. They can develop cracks, pitting and other problems, depending on the amount of tension involved in the joint.
The level of friction present in rolling joints can depend on their design, how they are used, and the lubricants that can be added to smooth out their movement. Low friction allows a joint to move more smoothly and functionally and can reduce the strain on components. It can also cause slipperiness, which may require a compromise. With cars, for example, a little friction is needed to help the wheels grip the road, while too much would slow down the car and make it difficult to handle.
Rolling contact research examines the types of conditions that must be present for components or entire joints to fail. High pressure and high friction tend to increase the failure rate, as do harsh conditions. Dust storms, for example, can drive sand into the joints, causing bearings to wear more quickly. This research helps engineers determine how to design bearings more effectively to create strong, reliable joints with minimal maintenance requirements.
Forms of rolling contact have been in use among human populations for a long time. One of the earliest forms of bearing was the log roller, which allowed people to move huge objects by pushing them along log arrays. People arranged logs, put objects on top, and pushed them. When the logs spun under the objects, they forced them forward to the logs at the front of the cluster. Eventually, the individual logs would pop out from underneath and could be recycled by placing them back into the front of the array.
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