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Stress & Strain

Assumptions and Limitations

Pressure is the intensity of normal distributed forces exerted on a surface and is defined as a force per unit area. Cylindrical and spherical pressure vessels are commonly used to carry or store both liquids and gases under pressure or vacuum, or to protect from outside pressures. Several assumptions have been made.

• Thin walled sections are those with a inner radius to thickness (r/t) ratio above or equal to 10.
• The applied pressure is the gauge pressure (the difference between the internal and external pressures).
• Materials are considered to be homogeneous, isotropic and linear-elastic.
• Any internal fluids or gases have a negligible weight.
• Plane sections before deformation remain plane after deformation.
• Stress and strain are linearly related and strains are small.
• Stress is measured from the point of application and acts perpendicular to the cross-section and any deformation of the member is uniform throughout.