Testing of Hardness and Impact Strength

Introduction

Hardness and impact strength are a few very important concepts in mechanical engineering. They are crucial subjects to study since they provide information on the sturdiness and durability of metals or machine plants.  Testing of hardness is elementary to the study of mechanical engineering. There are many kinds of tests performed to conduct testing of hardness. Testing of hardness is done by observing a steel ball pressed against the other material’s surface under tremendous pressure.  Testing of hardness is done through the Rockwell Hardness test and the Brinell Hardness Test. There are also different types of hardness tests. 

Testing of Hardness

Testing of hardness involves two basic things. To see if the material is durable under pressure, and to know its resistance power to deformity. Testing of hardness, therefore, checks the material’s nature to withstand a high amount of pressure without being deformed. Material hardness in the testing of hardness is described as the property of the material facilitating resistance to deformity. Deformities can be of many types. There are fractures, scratch marks, indentation, and breaking. So, testing of hardness measures the tensile strength of metals. 

• The tensile strength in mechanical engineering is the total of pressure any material like a metal can withstand until being fractured
• Tensile strength is a very important consideration in the testing of hardness and is measured in the psi unit
• It is represented as Ftu
• In performing the testing of hardness things like engineering stress and tensile strength are considered
• These are important since calculations of these values yield the curve of stress-strain graphically
• Brittle materials like some metals, woods, ceramics, and alloys are tested
•  Ductile materials are often not tested in the testing of hardness

Rockwell Hardness Test

Rockwell hardness test is a test that is performed to test material hardness. The Rockwell hardness test is based on the Rockwell scale. The scale used in the Rockwell Hardness Test measures the indentation magnitude of materials. The Rockwell Hardness Test is used for testing of hardness based on the comparison. The test calculates the indentation made before the application of a load and the degree of penetration after the application of load. Through the Rockwell Hardness Test, the emphasis is placed on the fact that hardness is not a property but a characteristic.

• In the conduct of the Rockwell Hardness Test, there is a fixed load or force and an indent that is used to make the indentation
• The Rockwell Hardness Test proves that material is the strongest when its indentation is small. The Rockwell Hardness Test is easier to perform, it also gives the best and most accurate values
• The Rockwell Hardness Test involves the application of preload in the form of a ball indenter. A diamond is also used
• After the preliminary load, a major load is applied and then the values obtained from these phases are compared

Brinell Hardness Test

Brinell Hardness Test is another method to test hardness. In a Brinell Hardness Test, the testing of hardness is done on coarse materials. The test loads in a Brinell Hardness Test are very high. The indenter used is also thicker than most. The following are the characteristics of the Brinell Hardness Test:

• Test load that is predetermined is used
• Carbide balls are used in the test
• The test load can measure up to 3000 kgf 
• A specialised optical system is used for the measurement

Types of Hardness Test

Types of Hardness Test in the testing of hardness topic are as follows:

• Vickers

• Brinell Hardness Test

• Rockwell Hardness Test

Among these three tests, the Rockwell Hardness Test is the most commonly used to determine material hardness in materials.

Conclusion

Testing of hardness involves two basic things. To see if the material is durable under pressure, and to know its resistance power to deformity. Testing of hardness, therefore, checks the material’s nature to withstand a high amount of pressure without being deformed. In mechanical engineering, there are two ways of measuring material hardness: Indent size created by the load and Point of indent creation by the load. It is for these reasons that testing of hardness is so important part of impact strength in engineering and mechanics.