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Hardness ranges from super hard materials like diamond and boron-carbide to other ceramics and hard metals, soft metals, plastics, and soft tissues. Hardness is only one mechanical measurement; toughness and strength must also be considered, as hard materials have low toughness and are easily fractured.
A variety of techniques, such as indentation, scratch, and rebound hardness measurements, can be used to determine hardness. nCATS has access to standard Vickers hardness and microhardness machines, as well as instruments for exploring hardness at the nano-scale with nanoindentation and atomic force microscope indentation.
What is hardness?
Little research is done on the assessment of therapeutically significant mechanical characteristics, and the numbers cited are nearly always connected to the material’s hardness. Although hardness tests have a place in contact lens characterisation, they do not indicate the sort of mechanical failure or difficulties that typically occur, which are typically linked with fracture, chipping or splitting, or distortion. In the lack of agreed-upon standards for appropriate procedures, manufacturers’ reported results are often derived using one or more of the standard hardness test methods.
Hardness and Microhardness
Hardness and microhardness are two of the most significant metrics for defining a material’s tribological properties. Friction and wear tests use practically every known material, from the hardest diamond to exceedingly delicate ones like human cartilage. Hardness, for example, is crucial to abrasive and erosive wear, and the hardness of experimental specimens should be equal to or identical to the hardness of actual components for valid measures of abrasive Wear resistance. Other wear processes are also heavily influenced by hardness, therefore if the hardness of the test specimens deviates from either realistic values or an intended level for study, erroneous findings are likely.
What is a hardness unit?
Brinell hardness testing is one of the indentation hardness tests developed for hardness testing. Brinell tests involve forcing a hard, spherical indenter into the surface of the metal to be tested under a specific load. A hardened steel ball with a diameter of 10 mm (0.39 in) is used as an indenter in the usual test, with a force of 3,000 kgf (29.42 kN; 6,614 lbf). For a set period of time, the load is kept constant (between 10 and 30 s). A smaller force is used for softer materials; for harder materials, a tungsten carbide ball replaces the steel ball.
The test yields numerical data that measure a material’s hardness, which is indicated by the Brinell hardness number – HB. The most generally used test standards (ASTM E10-14 and ISO 6506–1:2005) denote the Brinell hardness number as HBW (H from hardness, B from brinell, and W from the indenter material, tungsten (wolfram) carbide). Former standards used the abbreviations HB or HBS to refer to measurements taken using steel indenters.
What is “hard water?”
Hard water is water that contains calcium and magnesium salts, primarily as bicarbonates, chlorides, and sulphates. Ferrous iron may be present as well; when oxidised to ferric form, it appears as a reddish brown stain on washed fabrics and enamelled surfaces. Water hardness caused by calcium bicarbonate is referred to as temporary because boiling converts the bicarbonate to the insoluble carbonate; hardness caused by other salts is referred to as permanent. Hard water’s calcium and magnesium ions react with the higher fatty acids of soap to form an insoluble gelatinous curd, resulting in soap waste. Modern detergents do not cause this objectionable reaction.
Permanent Hardness of Water
When soluble salts of magnesium and calcium exist in water as chlorides and sulphides, we refer to this as permanent hardness because it cannot be removed by boiling.
We can remove the hardness from the water by treating it with washing soda. When washing soda reacts with the sulphide and chloride salts of magnesium and calcium, insoluble carbonates are formed, and hard water is converted to soft water.
Temporary Hardness of Water
When these ions are dissolved, they produce calcium and magnesium cations as well as carbonate and bicarbonate anions. The presence of metal cations causes the water to become hard. Hardness can be removed by boiling or adding lime (calcium hydroxide). Boiling encourages the formation of carbonate from bicarbonate and precipitates calcium carbonate out of solution, resulting in softer water after cooling. The insoluble carbonate is formatted.
Conclusion
Hardness is only one mechanical measurement; toughness and strength must also be considered, as hard materials have low toughness and are easily fractured. A variety of techniques, such as indentation, scratch, and rebound hardness measurements, can be used to determine hardness. Little research is done on the assessment of therapeutically significant mechanical characteristics, and the numbers cited are nearly always connected to the material’s hardness. Hardness, for example, is crucial to abrasive and erosive wear, and the hardness of experimental specimens should be equal to or identical to the hardness of actual components for valid measures of abrasive E-wear resistance. Hard water’s calcium and magnesium ions react with the higher fatty acids of soap to form an insoluble gelatinous curd, resulting in soap waste. Permanent Hardness of Water When soluble salts of magnesium and calcium exist in water as chlorides and sulphides, we refer to this as permanent hardness because it cannot be removed by boiling.
Elastic Modulus
We know that when an elastic material is distorted by an external force, it maintains an internal resistance to resist the deformation and returns to its original state once the external force is removed.
The various types of elastic moduli are as follows:
- Young’s Modulus: Young’s modulus is a property of an object that allows it to endure changes in its length when longitudinal tension or forces, such as compression, are applied. The longitudinal stress divided by the object’s strain equals the Young’s modulus. The letter Y symbolises Young’s Modulus.
- Shear Modulus: The shear modulus, also known as the Modulus of Rigidity, is the ratio of shearing stress to shearing strain. The letter ‘G’ symbolises Shear Modulus.
- Bulk Modulus: The ratio of hydraulic stress to associated hydraulic strain is known as bulk modulus. The letter ‘B’ symbolises Bulk Modulus.
Application of Elastic Behaviour of Solids
A slingshot deforms when stretched. When the force is removed, it reverts to its original shape. However, imagine trying to bend a thin steel rod. You bend it slightly and then let off the pressure. Is it possible for the rod to restore to its original shape? It doesn’t, it doesn’t, it doesn’t. The elastic and pliable characteristics of the material cause this difference in behaviour.
The rubber strip on the slingshot is incredibly bendable. Elasticity refers to a body’s ability to withstand irreversible change when stressed. The body returns to its original shape and size once the stress is released. The degree of elasticity in various materials varies. The elastic behaviour of a material is crucial to understand. Understanding material elastic behaviour is required in almost every engineering design.
In the construction of various structures such as bridges, columns, pillars, and beams, to name a few. Understanding the strength of the materials used in construction is crucial.
The elasticity of materials is primarily considered and learned in three scenarios:
- Thickness of the Steel Rope used in Cranes
- Design of the bridges
- Maximum Height of the mountains
Conclusion
We know that each atom or molecule in a solid is surrounded by other atoms or molecules. Interatomic or intermolecular forces hold them together and keep them in a stable equilibrium position. The atoms or molecules in a solid are displaced from their equilibrium positions when it is deformed, resulting in a shift in interatomic (or intermolecular) distances. Interatomic forces tend to drive them back to their former places when the deforming force is removed. As a result, the body reverts to its natural size and shape. A model of a spring-ball system, as shown in Fig, can be used to visualise the restoring mechanism. Atoms are represented by the balls, while interatomic forces are represented by the springs.
