Mitigating Corrosion Under Insulation and Supporting the Longevity of Industrial Pipe Insulating Systems

# Tensile Stress

Last updated: July 19, 2024

## What Does Tensile Stress Mean?

Tensile stress (σ) is the resistance of an object to a force that could tear it apart. It is calculated with the highest tension endured by the object in question without tearing, and is measured in Newtons/mm2, but was originally denoted in tons/inch2. Tensile stress can be defined as the magnitude of force applied along an elastic rod, which is divided by the cross-sectional area of the rod in a direction perpendicular to the applied force. Tensile means the material is under tension and that there are forces acting on it trying to stretch the material.

Stress is the force per unit area of a material, thus:

Tensile Stress = Force / Cross-sectional Area

Tensile stress measures the strength of a material; therefore, it refers to a force that attempts to pull apart or stretch a material. Many mechanical properties of a material can be determined by a tensile test.

Tensile stress may also be known as normal stress or tension. When an applied stress is less than the material’s tensile strength, the material returns completely or partially to its original shape and size. As the stress approaches the value of the tensile strength, the material has already begun to flow plastically and rapidly forms a constricted region called a neck, which is the point at which it fractures.

Tensile stress accelerates the corrosion process and leads to intergranular corrosion and intergranular stress-induced corrosion cracking of steel. Consequently, stress can reduce the mechanical properties and the overall strength of the corroded steel.

## Corrosionpedia Explains Tensile Stress

Tensile stress is a state in which an applied load tends to stretch the material in the axis of the applied load, or in other words, it is the stress caused by pulling the material. Tensile stress is the amount of direct load associated with stretching or tensile forces and is responsible for the stretching of the material on the axis of the applied load. The strength of structures with equal cross-sectional areas that are loaded in tension are independent of the shape of the cross-section.

Materials loaded with tension are subjected to stress concentrations at the location of material defects and abrupt changes in geometry that accelerate the strain of the material. Some materials may exhibit ductile behavior and can tolerate a certain number of defects before failure, while brittle materials can fail below their total material strength.

Tensile stress is the stress state leading up to expansion. The tensile stress may increase up until the tensile strength limit, which is known as the limit state of stress, and is defined as the force per unit area that is associated with stretching. It is denoted by the symbol σ.

The formula for computing the tensile stress in a rod is:

Tensile Stress = F / A

Tensile stress can cause stress corrosion cracking (SCC), which is the combined influence of tensile stress and a corrosive environment. The required tensile stresses may be in the form of directly applied stresses or residual stresses.

Stresses that cause environmental cracking can arise from the following actions:

• Residual cold work
• Welding
• Grinding
• Thermal treatment
• Externally applied during service

In order to be effective, these stresses must be tensile (as opposed to compressive).

One method of controlling stress corrosion is to eliminate stress, or at least reduce it below the threshold stress for stress corrosion cracking. Residual stresses can be relieved by stress-relief annealing, and this is widely used for carbon steels.

Synonyms

Normal Stress

Tension