In tension failure of a brittle metal, failure plane is at ________ degrees.

Question

Question

This question was previously asked in

JKSSB JE CE 2021 Official Paper Shift 2 (Held on 27 Oct 2021)

Answer 1

Explanation:

Modes of failure

Since brittle material is strong in compression but weak in tension whereas its shearing strength is in between its compressive strength and tensile strength.
Ductile material is approximately equal to strong tension and compression but weak in shear.

Case-1: Brittle material in torsion

Since brittle materials have minimum tensile strength. Hence, brittle materials fail in tension.
Hence brittle material subjected to torsion fails at 45° plane (Helicoidal failure).

Case-2: Ductile material in torsion

Since, ductile materials are weak in shear. Hence ductile materials failure occurs due to principle shear stress.
In torsion test maximum shear stress is in the direction perpendicular to longitudinal axis. Hence, ductile failure plane is torsion will be perpendicular to longitudinal axis.

Cast iron is a brittle material. So failure occurs as per case 5.

Case-3: Brittle material under tension

Brittle materials are very weak in tension. Brittle materials fail due to the separation of particles along the surface which is at 90° to the direction of load. The failure surface is rough.

Case-4: Brittle material under compression

Since brittle material strong in compression, therefore, failure is due to shear the plane to failure is at 45° from the axis of the shaft.

Case-5: Ductile material in tension

Since ductile material strong in tension, therefore failure is due to shear, the plane of failure is at 45° from the axis of the shaft, such failure is known as cup and cone failure.

Case-6: Ductile material in compression

Short compression members fail in compression yielding. The failure plane is at 90°, to the compressive load. In compression yielding, bulging of material occurs.