What is the difference between ductile failure and brittle failure

An elastic deformation is recoverable, while a plastic deformation is permanent. Ability of a material to exhibit plastic deformation before fracture is the indication of ductility. Materials that show substantial plastic deformation under external loading are called ductile materials; while brittle materials exhibit negligible plastic deformation. Similarities and differences between ductile material and brittle material are provided below.

Skip to content. Similarities between ductile material and brittle material Both are associated with the plastic deformation of the material under tensile loading. Ductility or brittleness is highly temperature dependent. For example, a brittle material can behave like a ductile one at an elevated temperature.

Similarly a ductile material at room temperature, when frozen, can automatically convert into brittle material. Ductility or brittleness of a material also depends on the inbuilt stress level. Under presence of high residual stress, a ductile material may fail without palpable plastic elongation. Differences between ductile material and brittle material Ductile Material Brittle Material Solid materials that can undergo substantial plastic deformation prior to fracture are called ductile materials.

Solid materials that exhibit negligible plastic deformation are called brittle materials. Percentage elongation of the ductile materials before fracture under tensile testing is higher.

Percentage elongation of the brittle materials before fracture under tensile testing is very less. Ductile materials fail gradually by neck formation under the action of external tensile loading.

Brittle materials fail by sudden fracture without any warning such as necking. Cyclic stresses should be avoided for brittle materials. So, systems having thermal and pressure cycles should not be designed from brittle materials.

The main concern with a brittle fracture or brittle failure is that under certain conditions failure occurs at stresses well below the yield strength. Such conditions are the presence of a flaw or crack. Brittle fractures are normally initiated by defects present in the manufactured product or fabricated structure or by defects that develop during service. These are basically stress concentrators and may take the form of.

Brittle fracture normally occurs because of the propagation of such cracks at great speed. Smaller grain size, higher temperature, and lower stress tend to mitigate crack initiation. On the contrary, larger grain size, lower temperatures, and higher stress favor crack propagation. There is a stress level known as the lower fracture propagation stress below which a crack will not propagate at any temperature.

With the increase in temperature, higher stress is required for a crack to propagate. A crack arrest curve defines the relationship between the temperature and the stress required for a crack to propagate. The amount of stress required to propagate a preexisting crack is indicated by the Fracture Toughness which depends on various factors mentioned below:. From the above curve it is evident that to avoid brittle fracture operating temperature should be maintained above NDT temperature.

Consider a thin plate of length l having a thru-crack of length 2c, as shown in Fig 3. The upper curve shows the force-deflection curve for a non-extending crack of length 2c. The Griffith theory is good for every brittle material like glass, in which failure occurs without any plastic deformation.

Ductile fracture or ductile failure Fig. From the above discussions it is clear that the brittle fracture and ductile fracture mechanism is completely different. The major differences between brittle and ductile fracture are provided below:. I am a Mechanical Engineer turned into a Piping Engineer.

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