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Definition of the shear stress:

Equation 2.1

τ = F/A

τ (pronounced: tou); with the shear force F [N] and the shear area (or shearing surface area) A [m2], see Figure 2.1. The following holds: 1 N = 1 kg · m/s2

The unit of the shear stress is [Pa], (pascal).

Blaise Pascal (1623 to 1662 [2.1]) was a mathematician, physicist, and philosopher.

For conversions: 1 Pa = 1 N/m2 = 1 kg/m · s2

A previously used unit was [dyne/cm2]; with: 1 dyne/cm2 = 0.1 Pa

Note: [Pa] is also the unit of pressure

100 Pa = 1 hPa (= 1 mbar); or 100,000 Pa = 105 Pa = 0.1 MPa (= 1 bar)

Example: In a weather forecast, the air pressure is given as 1070 hPa (hecto-pascal; = 107 kPa).

Some authors take the symbol σ for the shear stress (pronounced: sigma) [2.2] [2.3]. However, this symbol is usually used for the tensile stress (see Chapters 4.2.2, 10.8.4.1 and 11.2.14). To avoid confusion and in agreement with the majority of current specialized literature and standards, here, the symbol τ will be used to represent the shear stress (see e. g. ISO 3219-1, ASTM D4092 and DIN 1342-1).