Question

Uniaxial tension test (see the figure) is conducted on two different samples prepared with homogeneous, isotropic materials. One of the materials is brittle, whereas the other is ductile.

Assuming that there is no stress concentration at loading points, the failurewould initiate:

• A. along x–x in both materials
• B. along x–x in brittle material and along y–y in ductile material
• C. along y–y in brittle material and along x–x in ductile material
• D. along y–y in both materials

Hint:

Brittle → normal stress failure (perpendicular plane). Ductile → shear stress failure (45° plane).

Answer 1

The Correct Option is B

A uniaxial tensile load produces normal and shear stresses on inclined planes. Failure plane depends on the material response.

Step 1: Brittle materials.
Brittle materials fail along the plane of maximum normal stress.
Under axial tension, the plane perpendicular to load (x–x plane) has maximum tensile stress.
Hence brittle sample fails along x–x.

Step 2: Ductile materials.
Ductile materials fail by shear.
Maximum shear stress occurs on planes at 45° to the loading direction (y–y plane shown in figure).
Thus ductile sample fails along y–y.

Step 3: Combine both results.
Brittle → x–x failure
Ductile → y–y failure

Final Answer: (B)