What is a contact stress?
Description. Contact stress happens when force is concentrated on a small area of the body, pinching or crushing tissue and causing discomfort and often pain. You experience contact stress, for example, when the edge of a work surface digs into your forearm or wrist.
What is contact stress in engineering?
Contact mechanics is part of mechanical engineering. Hertzian contact stress refers to the localized stresses that develop as two curved surfaces come in contact and deform slightly under the imposed loads. This amount of deformation is dependent on the modulus of elasticity of the material in contact.
What is contact stress analysis?
Contact stress calculations are based on Hertzian pressure analysis between two cylinders (represented by the teeth in contact under compression load).
What does contact pressure mean?
The contact pressure is the ratio of the normal load to the true contact area, which is the sum of the front and rear areas. It may be called the scratch hardness only in the case of plastic contact.
Which of the following is an example of contact stress?
Examples of contact stress include resting wrists on the sharp edge of a desk or workstation while performing tasks, pressing of tool handles into the palms, especially when they cannot be put down, tasks that require hand hammering, and sitting without adequate space for the knees.
What causes contact stress ergonomics?
Contact stress happens when some part of a worker’s body—knees, elbows, wrists or fingers, for example—touches or rubs up against a hard, sharp or inflexible surface repetitively or for an extended period of time. The surface could be a workstation, the floor, a ladder, a tool or the handle of a bucket.
What is mechanical contact stress?
Mechanical contact stress is the force applied to specific parts of an employee’s body as they come in continual contact with an inflexible surface such as a tool, workstation, or machine while performing assigned tasks within the workplace, which puts these particular body areas under increasing levels of pressure.
What is a contact problem?
A contact problem occurs when at least two bodies not mechanically joined touch each other without becoming rigidly attached. In most cases, high stress concentrations are developed in the contact areas. This fact and the presence of friction and wear often cause crack initiation and fretting fatigue.
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 soil contact pressure?
Contact pressure is the actual pressure transmitted from the foundation to the soil. This is only possible if the foundation is perfectly flexible. The contact pressure distribution of a rigid foundation depends upon the type of soil beneath it.
What is compression or contact stress?
Contact stress results from occasional, repeated or continuous contact between soft body tissue and a hard or sharp object, such as workstation edges, tools, machinery, products or the floor. Tissue that is compressed for prolonged periods of time may be damaged.
How can contact ergonomics reduce stress?
- Provide workstations with rounded edges.
- Provide padding or wrist/armrests and a mouse pad in appropriate spots.
- Redesign workstation to reduce contact between wrist/forearm and inflexible surfaces.
How to calculate contact stress of two spheres?
The following equation will determine the contact stress between a sphere and a flat surface with known young’s modulus and applied load. Where: E = Young’s modulus. F = load. r 1, r 2 =radii. v = Poisson’s ratio. Contact stresses two sphere’s in contact same material and differnet spherical radius. Contact area radius.
How are contact stresses determined for complicated surfaces?
The exact determination of contact stresses for complicated surfaces is a difficult process. It depends strongly on the geometry of the contacting surfaces. Point/line contacts are used to describe ideal situations whereby the contacting bodies do not undergo any deformation, that is, theoretically;
Is the contact area of two spheres infinite?
Theoretically, the contact area of two spheres is a point, and it is a line for two parallel cylinders. As a result, the pressure between two curved surfaces should be infinite for both of these two cases, which will cause immediate yielding of both surfaces.
When does a sphere press against an elastic material?
When a sphere is pressed against an elastic material, the contact area increases. Classical contact mechanics is most notably associated with Heinrich Hertz. In 1882, Hertz solved the contact problem of two elastic bodies with curved surfaces.