in physics, what is a STRESS?

Answer 1

A mature tree trunk may support a greater force than a fine steel wire but intuitively we feel that steel is stronger than wood. To predict the forces which a structure of any size, made of any material, can sustain without failing, we need the concept of mechanical stress.

The definition of stress originates in two observations of the behaviour of a one-dimensional body subject to uniaxial loading, for example, a steel wire under uniaxial tension:

1. When the wire is pulled, it stretches. Up to a certain load, the stretch ratio (current length / initial length) is proportional to the load divided by the cross-sectional area of the wire. We therefore define the stress as σ = F/A.
2. Failure occurs when the load exceeds a critical value for the material, the tensile strength multiplied by the cross-sectional area of the wire, Fc = σt A.

These observations suggest that the quantity that affects the deformation and failure of materials is stress.

In the more general setting of continuum mechanics, stress is a measure of the internal distribution of force per unit area that balances and reacts to the external loads or boundary conditions applied to a body. Stress is an example of a type of quantity called a second-order tensor. In three dimensions, a second-order tensor can be represented by a 3×3 square matrix (containing nine components). However, in the absence of body moments, the stress tensor is symmetric and can be fully specified by six components. These six components are sometimes written in Voigt notation as a 6×1 column matrix which is often, misleadingly, called the stress vector.

Answer 2

Stress is a tensor (a matrix of values) that measures the force per unit area in body.

Imagine a tiny cube inside a body. On one face of the cube there can be three forces at work - one perpendicular to it and two (at right angles to it) in the face. The perpendicular one is the tensile stress - it makes the faces of adjacent cubes pull apart - and the others are shear stresses - they make the faces of adjacent cubes slide over each other.

You can repeat this for two other faces of the cube (the other three are parallel to these and so identical). This gives you 9 total values in the matrix - hence the stress tensor is a 3 x 3 matrix. Its diagonal components are the tensile stress.

Answer 3

there's no ordinary clarification of rigidity, because rigidity is a 'tensor' and must be defined in words of the rigidity in step with unit section on diverse planes by the point in question. as an example, in case you pull on each and each and every end of an iron twine, there'll be a tensile rigidity on the middle of the twine equivalent to the rigidity on both end divided by the realm on the middle. regrettably, it really is not the end of the outline. As you stretch the twine, that is likewise pulled inward, something extra obtrusive once you stretch chewing gum, say.

Answer 4

gravity, friction, warping