Name: brittle material failure under tension
Uploaded: 2025-05-22T09:06:17.000Z
Duration: 1 min 24 s
Channel: JoVE

Brittle materials, under tensile stress, do not elongate much before rupturing, meaning their ultimate and breaking strengths are identical. Compared with ductile materials, they possess lower strain during rupture.
It occurs along a surface perpendicular to the load, indicating that normal stresses primarily cause the failure.
Brittle materials do not undergo noticeable necking under stress.
Most brittle materials have higher ultimate strength in compression than tension, mainly due to microscopic flaws like cracks or cavities, that weaken the material under tension.
Consider a stress-strain diagram for the concrete slab, an example of a brittle material.
Under tension, a linear elastic range is observed until the yield point, and then strain increases more rapidly than stress until the slab ruptures.
Under compression, concrete displays a larger linear elastic range, and rupture doesn&#39;t occur as stress hits its peak. Instead, stress decreases while strain continues to increase until rupture.
The modulus of elasticity, represented by the slope of the linear region, is equal in both compression and tension for most brittle materials.

stress-strain diagram - brittle materials

Brittle materials, including glass, cast iron, and stone, exhibit unique characteristics. They fracture without considerable change in their elongation rate, indicating that their breaking and ultimate strength are equivalent. Such materials also show lower strain levels at the point of rupture. The failure in brittle materials predominantly results from normal stresses, as evidenced by the rupture created along a surface perpendicular to the applied load. These materials do not display significant necking. Necking is the local reduction in cross-sectional area under stress. An interesting aspect of most brittle materials is their higher ultimate strength in compression than in tension, primarily due to microscopic defects like cracks or cavities that can weaken the material under tensile stress but have minimal impact on its compressive strength.
Concrete, a common brittle material, behaves differently under tension and compression. The stress-strain diagram under tension reveals a linear elastic range up to the yield point, followed by a rapid increase in strain until rupture. In contrast, concrete shows a larger linear elastic range under compression, and rupture does not occur even at peak stress. Instead, stress decreases as strain increases until rupture. Importantly, the modulus of elasticity, indicated in the stress-strain curve by the slope of the linear section, remains consistent in both tension and compression for most brittle materials.

Stress-Strain Diagram - Brittle Materials

Brittle materials, including glass, cast iron, and stone, exhibit unique characteristics. They fracture without considerable change in their elongation ...

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JoVE Core

Mechanical Engineering

Unit 1

Stress and Strain - Axial Loading

KEY TERMS AND CONCEPTS

brittle material failure under tension

Brittle materials such as glass, cast iron, and stone fail with very little change in elongation. Their breaking strength and ultimate strength are nearly the same, and the strain at rupture is low. In these materials, failure is usually driven by normal stress, so the break surface is typically perpendicular to the applied load.

Brittle materials also show little or no necking. Necking is the local narrowing of a material’s cross section under stress. Another important feature is that many brittle materials are stronger in compression than in tension. Small cracks or cavities can weaken them in tension, but these defects have much less effect when the material is compressed.

Concrete is a common example of a brittle material. Under tension, its stress-strain curve has a linear elastic region up to the yield point, followed by a rapid rise in strain until rupture. Under compression, concrete has a longer linear elastic range, and rupture does not happen at the peak stress. Instead, stress drops as strain keeps increasing until failure.

For most brittle materials, the modulus of elasticity is the same in tension and compression. The modulus of elasticity is the slope of the linear part of the stress-strain curve. This slope shows how stiff the material is in both loading modes.

Brittle Material Failure Under Tension

normal strain under axial loading

Axial Stress and Strain in a Rod

Axial stress and strain in a rod describe how a material changes length when a force is applied along its axis. The force may stretch the rod or compress it. In mechanics of materials, this deformation is called normal strain. Normal strain is found by dividing the change in length by the original length. This gives a unitless ratio that shows how much the material deforms under load. A load-deformation diagram can show elongation, but it cannot predict how another rod will deform. When a...

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Brittle materials such as glass, cast iron, and stone fail with very little change in elongation. Their breaking strength and ultimate strength are nearly the same, and the strain at rupture is low. In these materials, failure is usually driven by normal stress, so the break surface is typically perpendicular to the applied load. Brittle materials also show little or no necking. Necking is the local narrowing of a material’s cross section under stress. Another important feature is that many...

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deformation of member under multiple loadings

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Calculating Rod Stretch from Mixed Loads

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poisson's ratio

Material Strain Under Axial Loading

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shearing strain

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saint-venant's principle

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Saint-Venant's principle describes how stress changes in a structural member when a load is applied. It shows that the exact way a load is placed matters most near the point of application. Farther away from that point, the stress pattern becomes much less dependent on how the load was applied. A simple example uses a member with plates on both ends. When the loads are applied at the center of the plates, the plates move toward each other without rotating. The member shortens in length and...

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key terms and concepts

Explore how brittle materials like glass, cast iron, stone, and concrete behave under tension and compression, including rupture, necking, and elasticity.

Brittle Material Failure Under Tension | JoVE K12

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Brittle Material Failure Under Tension

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