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# Stress

## Stress is force applied on cross-sectional area.

Stress is the ratio between applied force and cross-sectional area where the applied force is acting.

### Normal Stress

Normal stress can be expressed as

σ = FN / A                           (1)

where

σ = normal stress (N/m2, Pa, psi)

FN = applied force perpendicular to the area - Normal force (N, lb)

A = cross-sectional area (m2, in2)

### Shear Stress

Shear stress can be expressed as

τ = FV / A                           (2)

where

τ = shear stress (N/m2, Pa, psi)

FV = applied force in plane of the area - Shear force (N, lb)

### Example - Normal Stress in a Column A 10000 N force is acting in the direction of a British Universal Column UB 152 x 89 x 16 with cross sectional area 20.3 cm2. The normal stress in the column can be calculated as

σ = (10000 N) / ((20.3 cm2) (0.0001 m2/cm2

= 4926108 Pa (N/m2)

= 4.9 MPa

The Yield strength - the amount of stress that a material can undergo before moving from elastic deformation into plastic deformation - is typical 250 MPa for steel.

### Example - Shear Stress in a Beam with Point Load For a beam with single point load supported on both ends - the shear force Fv (or V in the figure above) is equal in magnitude to support force R1 or R2.

Reaction forces can be calculated due to moment equilibrium around support 1

F L / 2 = R2 L                              (4)

R2 = F / 2                              (5)

R1 = R2 = F / 2                         (6)

For a 10000 N point load perpendicular on a beam similar to the example above - supported at both ends - the magnitude of the reaction and shear forces can be calculated as

R1 = R2

= V1

= V2

= (10000 N) / 2

= 5000 N

= 5 kN

The shear stress can be calculated as

τ = (5000 N) / ((20.3 cm2) (0.0001 m2/cm2)

= 2463054 Pa

= 2.5 MPa

## Related Topics

• ### Mechanics

Forces, acceleration, displacement, vectors, motion, momentum, energy of objects and more.
• ### Statics

Loads - forces and torque, beams and columns.

## Related Documents

• ### Process Pipes - Allowable Stress vs. Temperature

Allowable wall stress in pipes according ASME M31.3.
• ### Restricted Thermal Expansion - Force and Stress

Stress and force when thermal expansion a pipe, beam or similar is restricted.
• ### Rotating Bodies - Stress

Stress in rotating disc and ring bodies.
• ### Shafts Torsion

The torsion of solid or hollow shafts - Polar Moment of Inertia of Area.
• ### Steam Boiler Shells - Stress vs. Boiler Pressure

Calculate the stress in steam boiler shells caused by steam pressure.
• ### Steels - Endurance Limits and Fatigue Stress

Endurance limits and fatigue stress for steels.
• ### Stress in Thick-Walled Cylinders or Tubes

Radial and tangential stress in thick-walled cylinders or tubes with closed ends - with internal and external pressure.
• ### Stress in Thin-Walled Cylinders or Tubes

Hoop and longitudinal stress thin-walled tubes or cylinders.
• ### Stress, Strain and Young's Modulus

Stress is force per unit area - strain is the deformation of a solid due to stress.

• ### Young's Modulus, Tensile Strength and Yield Strength Values for some Materials

Young's Modulus (or Tensile Modulus alt. Modulus of Elasticity) and Ultimate Tensile Strength and Yield Strength for materials like steel, glass, wood and many more.

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## Citation

• The Engineering ToolBox (2008). Stress. [online] Available at: https://www.engineeringtoolbox.com/stress-d_1395.html [Accessed Day Month Year].

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9.27.11