Ductility

The Main Idea

Ductility is a solids ability to deform under tensile stress. It is similar to malleability, which characterizes a materials ability to deform under an applied stress. Both of these are plastic properties of materials. While they are often similar, sometimes a materials ductility is independent from its malleability. Materials with metallic bond have much higher ductility's du to the mobile electrons that tend to deform, rather than fracture. Therefore the most common ductile materials are steel, copper, gold and aluminum. Ductility is an important property in material science and metal-working industries, where solids are deformed nd molded with outside forces.

Fig. 1- Highly brittle fracture

Fig. 2- Semi-ductile fracture

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Environmental factors can also affect the ductility of a material. A temperature increase causes a material to stretch, and thus increases ductility. A temperature decreases leads to brittle and fragile behavior of the material and as such decreases ductility. Percent Reduction of Area (formula below) is a better accepted form for measuring ductility of a material.

A Mathematical Model

Mathematically, ductility can be defined as the fracture strain, or the tensile strain along one axis that causes a fracture to occur. Fractures range from brittle fractures (Fig. 1) to fully ductile fractures (Fig. 2), resulting in very different physical appearances associated with the different types. This can be modeled on a stress/strain curve (https://www.nde-ed.org/EducationResources/CommunityCollege/Materials/Graphics/Mechanical/Brittle-Ductile.gif) showing where fracture occurs along the graph.

Quantitatively being able to measure ductility is important with regards to comparing ductility between different materials. Ductility can be measured through two main methods: percent elongation and percent reduction of area. The formulas can be found below: (http://www.engineersedge.com/material_science/ductility.htm)

Percent Elongation = (Final Gage Length - Initial Gage Length) / Initial Gage Length

      = ((Lf - Lo) / Lo) * 100

Percent Reduction of Area = (Area of Original Cross Section - Minimum Final Area) / Area of Original Cross Section

      = (Decrease in Area / Original Area)

Connectedness

As an engineering major, determining the correct material for components can be high risk. Knowing different materials ranges of ductility, can be integral in choosing he best option. This is especially important in materials that have a high applied tensile strength.

History

Percy Williams Bridgman's findings on tensile strength and material properties led to much of what is known about ductility, including that it is highly influenced by temperature and pressure. these findings led him to win the 1946 Nobel Prize in physics.

See also

• Malleability
• Temperature
• Pressure

Further reading

https://en.wikipedia.org/wiki/Ductility

External links

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References

https://en.wikipedia.org/wiki/Ductility https://en.wikibooks.org/wiki/Advanced_Structural_Analysis/Part_I_-_Theory/Materials/Properties/Ductility https://en.wikipedia.org/wiki/Ductility#/media/File:Ductility.svg https://en.wikipedia.org/wiki/Percy_Williams_Bridgman http://www.engineersedge.com/material_science/ductility.htm