# What is Hertz theory?

## What is Hertz theory?

Hertzian theory of non-adhesive elastic contact. The classical theory of contact focused primarily on non-adhesive contact where no tension force is allowed to occur within the contact area, i.e., contacting bodies can be separated without adhesion forces.

What is JKR model?

The JKR model [1] (Johnson, Kendall, Roberts – 1964-1971) applies to tips with large curvature radius (most likely to macroscopic bodies) and small stiffness. Such systems are called strongly adhesive. The model accounts for the influence of Van der Waals forces within the contact zone.

What is the contact pressure between two bodies?

Suppose that two elastic bodies are in contact at a single point. If the bodies are pressed with a force, say F, the contact, because of deformation, will not be in a single point but will be over a small area of the surface of each body. This surface is called the pressure surface.

The contact radius between two objects depend on their material properties (e.g. elasticity) and on their geometry. If you press a rigid sphere into a fluid then after a while the wet area has radius a = sqrt(2Rh-h^2).

What is Hertz contact?

What is meant by elastic half space?

The theory of continuous elastic half-space implies that the subgrade forms a continuous, homogeneous and perfectly elastic body of infinitely large size, limited from above by the plane on which lies the foundation structure. Sometimes it is referred to as the Boussinesque model of soil.

## What are contact stresses?

Contact stress is damage to the tissue of the body caused by contact between soft tissue and a hard object. Contact stress may be internal or external. External contact stress is most often caused by a part of the body coming into contact with a hard surface such as a desk or machinery.

What is contact stress analysis?

Contact stress analyses for spur and helical gears are performed between two gear teeth at different contact positions during rotation. Two examples of spur and helical gears are presented to investigate the respective variations of the contact stress in a pair of mating gears with the contact position.

What is semi infinite elastic half-space?

The stresses may be calculated to good approximation by considering each body as a semi-infinite elastic solid bounded by a plane surface: i.e. an elastic half-space. It simplifies the boundary conditions and makes available the large body of elasticity theory which has been developed for the elastic half-space.

### What does von Mises stress represent?

The von Mises stress (σVM) represents the equivalent stress state of the material before the distortional energy reaches its yielding point. Note that the von Mises stress only considers distortion energy (change in shape) and not dilatational energy (change in volume).

What causes contact stress?

Internal contact stress may occur when muscles, nerves, tendons, or other soft tissue rub, or press, against bone or tendons in a way that causes the tissue to bruise or over-extend. External contact stress is most often caused by a part of the body coming into contact with a hard surface such as a desk or machinery.

What is elastic half-space theory?