How does a cast iron specimen fail under compression load?

Materials like cast iron are weak in tension because of the presence of sub-microscopic cracks and faults. In compression test the cross sectional area of the specimen increases which tends to increase the compressive strength. Therefore reach much higher ultimate stresses in compression than in tension.

What is the expected angle of fracture in cast iron?

Cracks along the diameter of the cast iron specimen are formed at the angle of approximately 50 degrees on both sides.

Why cross sectional area of compression specimens must be larger than those of tension specimens?

It is seen that a compression test is more difficult to be conducted than standard tensile test due to (i) specimen must have larger cross-sectional area to resist any buckling due to bending, (ii) the specimen undergoing strain hardening as deformation proceeds, and (iii) cross-section of the specimen increases with …

When a cast iron specimen is tested in tension its failure is?

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

Where would the fracture in cast iron specimen occur in compression test?

Therefore the fracture would be due to slip of planes and is due to the combination of compressive and shear stresses. As cast iron is weak in shear, failure occurs along this inclined plane.

Why compression tests are generally performed on brittle materials?

Mechanical Testing Brittle materials are well known to be much stronger in compression than in tension. This is because under a compressive load a transverse crack will tend to close up and so could not propagate.

Where would the fracture in a cast iron specimen occur in a compression test?

Why is compression test needed?

Compression tests are important to measure the elastic and compressive fracture properties of brittle materials or low-ductility materials. These properties are important to determine if the material is suited for specific applications or if it will fail under specific stresses.

Which is the is code used for compression test on metals?

ASTM E9 describes the compression testing of metals such as steel or metal alloys. This test method determines important mechanical properties such as the yield strength, the yield point, Young’s Modulus, the stress-strain curve, and the compressive strength.

What type of specimen may be used during the tensile test on cast iron?

Usually, most of metal foundries in China use the 14mm diameter as the standard test specimen. This principle is suitable for both cast iron and cast steel.

Why alignment of the specimen is is important in compression test?

Specimen alignment plays a critical role in material testing. If a specimen is not properly aligned prior to or during testing, the accuracy and the reliability of test results will be directly affected, and, depending on the method followed, results may not be acceptable.

Why is bone stronger in compression than tension?

Both cortical bone and trabecular bone are stronger in compression than tension, which reflects the fact that the inorganic phase is stronger in compression than tension. The organic phase contributes to the ductility and toughness of the tissues.

Why do brittle test pieces fracture in compression?

The brittle test piece fractures in compression because of shearing along a plane inclined to the axis. The orientation of the plane of shear is affected by the compressive stresses, the shear of plane may vary from 35o and 45o along with the axis.

Why is compression not uniform over the height of the specimen?

Due to the high frictional forces between the upper side of the specimen and the pressure plate or between the underside of the specimen and the base, the compression is not uniform over the specimen height.

What is a compression test?

A compression test is a method for determining the behaviour of materials under a compressive load. Compression tests are conducted by loading the test specimen between two plates and then applying a force to the specimen by moving the crossheads together.

What is the value of plastic strain in compression test?

The value for this is commonly set at 0.2\% plastic strain.Materials like cast iron are weak in tension because of the presence of sub-microscopic cracks and faults. In compression test the cross sectional area of the specimen increases which tends to increase the compressive strength.