What are shear stress and strain deformation?

In continuum mechanics, stress describes the internal forces present during deformation while strain measures the relative deformation of a material. Strains can be decomposed into normal components, which stretch or compress material fibers, and shear components, which cause angular distortion through the sliding of plane layers. Together, these concepts allow engineers and scientists to analyze how solid materials respond under external forces.

What we know

• Stress expresses the internal forces that neighboring particles of a continuous material exert on each other, whereas strain measures the relative deformation of the material. [4]
• A given strain can be decomposed into normal components, which involve stretching or compression, and shear components, which involve angular distortion and the sliding of plane layers over each other. [2]
• Strain is a dimensionless quantity defined as a relative change of length or a ratio of lengths, with SI base units of meter per meter. [1, 2]
• Stress has the dimension of force per area, with SI units of newtons per square meter or pascals. [4]

Still open

• The exact relationship between mechanical stress, strain, and strain rate can be quite complicated, though linear approximations are often used in practice when quantities are sufficiently small.

Where to go next

• the bigger pictureHow do materials behave under solid mechanics?
• how we knowWhat is a stress-strain curve?
• what caused itHow does tensile stress cause elongation?
• what followedWhat causes permanent deformation and fracture?
• how it workedHow is linear strain calculated?
• an unexpected connectionCan dental prostheses rely on the mechanics of solid materials?Solid mechanics is not just for massive civil engineering structures like bridges, but is also fundamental for designing medical items like surgical implants and dental prostheses.

Sources

• [1]linear strain (Wikidata Q1990546) · CC0 1.0
• [2]Strain (mechanics) · CC BY-SA 4.0
• [3]Solid mechanics · CC BY-SA 4.0
• [4]Stress (mechanics) · CC BY-SA 4.0
• [5]Stress–strain curve · CC BY-SA 4.0