Shear stress is the stress that is applied along a parallel or tangential direction to a cross-section of a material. Shear stress differs from normal stress, which is when stress is applied perpendicular to the face of a material. Calculating general shear stress is relatively simple.
Obtain or measure the area of the material over which the force is applied. Let's call this value "A." The area of simple rectangle or square-shaped cross section is obtained by multiplying length by height. The area of a circular cross section is calculated by the equation A= pi*r^2. To further clarify, the area of a circle is equal to the value of pi (3.14159) multiplied by the squared radius of the circle. See the resources section for help with area calculations.
Obtain or measure the force that is to be applied over this area. Let's call this value "F." Simple static forces of weight can be measured with a scale that displays results in pounds.
Substitute the values obtained in Steps 1 and 2 into the following formula: T=F/A
T = the shear stress F = the force applied from Step 2 A = the cross-sectional area over which the force was applied from Step 1
Divide the numerical value for "F" by the numerical value for "A." The resulting number is the calculated shear stress.
Shear stress also applies to fluids that are moving along a solid boundary. This involves a calculation using the dynamic viscosity of the fluid as well as the velocity of the fluid.