Power-law friction in closely packed granular materials
1Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-0032, Japan.
Summary
Friction in granular materials increases with shear rate. A new parameter, the inertial number, unifies friction behavior across different pressures, revealing power-law relationships for both friction and volume fraction.
Area of Science:
- Physics
- Materials Science
- Geophysics
Background:
- Understanding friction in dense granular materials is crucial for various scientific and engineering applications.
- Granular materials exhibit complex behaviors under shear stress.
Purpose of the Study:
- To investigate the nature of friction in dense granular materials under isobaric plain shear.
- To establish a generalized relationship for friction coefficients using a nondimensional parameter.
Main Methods:
- Discrete element simulation was employed to model granular layers.
- Granular layers were subjected to isobaric plain shear conditions.
Main Results:
- The friction coefficient was found to increase with the shear rate, following a power law.
- A nondimensional parameter, the inertial number, was used to generalize the power law, causing friction coefficients at different pressures to collapse onto a single curve.
- The volume fraction was also shown to obey a power law.
Conclusions:
- The study provides a generalized framework for understanding friction in granular materials.
- The inertial number is an effective parameter for unifying friction behavior across varying pressures.
- Power-law relationships govern both friction and volume fraction in dense granular shear.
Related Concept Videos
01:05Static and Kinetic Frictional Force
One of the simpler characteristics of sliding friction is that it is parallel to the contact surfaces between systems, and is always in a direction that opposes the motion or attempted motion of the systems relative to each other. If two systems are in contact and moving relative to one another, then the friction between them is called kinetic friction. For example, kinetic friction slows a hockey puck sliding on ice.
However, if two systems are in contact and are stationary relative to one...
However, if two systems are in contact and are stationary relative to one...
01:07Frictional Force
When a body is in motion, it encounters resistance because the body interacts with its surroundings. This resistance is known as friction, a common yet complex force whose behavior is still not completely understood. Friction opposes relative motion between systems in contact, but also allows us to move. Friction arises in part due to the roughness of surfaces in contact. For one object to move along a surface, it must rise to where the peaks of the surface can skip along the bottom of the...
01:21Rolling Resistance
When a solid cylinder rolls steadily on a rigid surface, the normal force applied by the surface on the cylinder is perpendicular to the tangent at the contact point. However, since no materials are entirely rigid, the surface's reaction to the cylinder involves a range of normal pressures.
For instance, imagine a hard cylinder rolling on a comparatively soft surface. The cylinder's weight compresses the surface beneath it. As the cylinder moves, the material in front of it slows down due to...
For instance, imagine a hard cylinder rolling on a comparatively soft surface. The cylinder's weight compresses the surface beneath it. As the cylinder moves, the material in front of it slows down due to...
01:21Characteristics of Dry Friction
Dry friction occurs when two solid surfaces slide against each other without any lubrication or fluid present. It causes resistance when pushing objects along a surface, like a gardener pushing a wheelbarrow. The force applied to move the cart causes dry friction between the wheel and the ground.
Before the wheelbarrow starts moving, the static frictional force acts tangentially to the contact surface, opposing the force that is about to induce the motion. This frictional force prevents the...
Before the wheelbarrow starts moving, the static frictional force acts tangentially to the contact surface, opposing the force that is about to induce the motion. This frictional force prevents the...
01:28Frictional Forces on Flat Belts
Flat belts are commonly used in various industrial applications for transmitting power from one pulley to another. When a flat belt is wrapped around a set of pulleys, it experiences different tensions at the driving pulley ends due to the friction between the belt and pulley surface. When the pulley moves in a counterclockwise direction, the tension T2 on the opposite side of the pulley where the belt is moving away from is higher than the tension T1 on the side where the belt is moving...
01:27Types of Friction Problems
Friction is an essential concept in physics, engineering, and everyday life. It is the force that opposes the relative motion or tendency of such motion between two surfaces in contact. One of the most common types of friction encountered in various applications is dry friction. Dry friction problems can be broadly categorized into three types, each with unique characteristics and challenges.
The first type of dry friction problem involves situations where there is no apparent impending motion.
The first type of dry friction problem involves situations where there is no apparent impending motion.