Lec-2-History-and-Properties-of-Material-2.pptx

Classification of Material Materials Development Era The different eras of human history and prehistory were originally named after the primary material in use at the time. The Stone Age Materials Development Era Bronze Age Materials Development Era The Iron Age Materials Development Er...

Classification of Material Materials Development Era The different eras of human history and prehistory were originally named after the primary material in use at the time. The Stone Age Materials Development Era Bronze Age Materials Development Era The Iron Age Materials Development Era The Porcelain Age Materials Development Era The Steel Age Materials Development Era The Silicon Age https://www.youtube.com/watch?v=7SVybnfUkbo https://www.youtube.com/watch?v=oDHCZOAWq-4 https://www.youtube.com/watch?v=BHZALtqAjeM&t=213 s Properties of Materials Mechanical Properties 1. Abrasion: The resistance of a material to the abrasion is found out by dividing the difference in weights of specimens prior to and after abrasion with the area of abrasion. 2. Creep: In many applications, the building materials are required to sustain steady loads for long periods 3. Elasticity: When a load is applied to a material, there is change in its shape and dimension a. Elastic Deformation: A deformation is said to be elastic when the solid deforms when it is loaded but returns to its original position when unloaded b. Plastic Deformation: A deformation is said to be plastic when the solid retains full or partly the change in shape after the load is removed 4. Fatigue: When the materials are subjected to a repetitive or fluctuating stress, they will fail at a stress much lower than that required to cause fracture under steady loads. Mechanical Properties 5. Hardness: The ability of a material to resist penetration by a harder body Mechanical Properties 6. Impact Strength: The impact strength of a material is the quantity of work required to cause its failure per its unit volume 7. Plasticity and Brittleness: The term plasticity of a material is defined as its ability to change its shape under load without cracking and to retain its shape after the removal of load. The brittle materials fail suddenly under pressure without appreciable deformation preceding the failure. 8. Strength: The ability of a material to resist failure under the action of stresses caused by a load 9. Wear: The failure of a material under the combined actions of abrasion and impact Chemical Properties The chemical properties of the material suggest the tendency of the material to combine with other substances, its reactivity, solubility and effects like corrosion, chemical composition, acidity, alkalinity, etc. 1. Corrosion: When iron reacts with oxygen, iron oxide is formed which is red in color and iron metal is coated with it Electrical Properties These properties signify the ability of the material to resist the flow of an electric current and they include conductivity, dielectric strength and resistivity. 1. Conductivity: This refers to the ability of the material to allow the passage of electricity or heat. Magnetic Properties: 1. Permeability: the measure of magnetization that a material obtains in response to an applied magnetic field 2. hysteresis: a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past 3. Coercive force: the value of the external magnetic field that brings to zero the magnetization or magnetic flux density of a magnetic body when that external magnetic field is caused to operate in the opposite direction from the orientation of the magnetization of the magnetic body Optical Properties: 1. Color 2. light transmission 3. refractive index 4. reflectivity Physical Properties (1) Bulk Density: The term bulk density is used to mean the mass of a unit volume of material in its natural state i.e. including pores and voids. It is obtained by finding out the ratio of mass of specimen to the volume of specimen in its natural state Physical Properties 2. Chemical Resistance: The ability of material to withstand the action of acids, alkalis, gases and salt solution. 3. Coefficient of Softening: The ratio of compressive strength of material saturated with water to that in dry state 4. Density: The term density of a material is defined as the mass of a unit volume of homogeneous material. It is obtained by working out the ratio of mass of material to the volume of material in homogeneous state. 5. Density Index: The ratio of bulk density of a material to its density is known as its density index and it thus denotes the degree to which its volume is filled up with solid matter 6. Durability: The property of a material to resist the combined action of atmospheric and other factors Physical Properties 7. Fire Resistance: The term fire resistance is used to mean the ability of a material to resist the action of high temperature without losing its load- bearing capacity. 8. Frost Resistance: The ability of a water-saturated material to resist repeated freezing and thawing without considerable decrease of mechanical strength or visible signs of failure is known as the frost resistance 9. Hygroscopicity: The property of a material to absorb water vapor from air 10. Porosity: The term porosity is used to indicate the degree by which the volume of a material is occupied by pores. 11. Refractoriness: The ability of a material to withstand prolonged action of high temperature without melting or loosing shape. Physical Properties 12 Spalling Resistance: The ability of a material to endure a certain number of cycles of sharp temperature variations without failing is known as its spalling resistance and it mainly depends on the coefficients of linear expansion of its constituents. 13. Specific Heat: The term specific heat is defined as the quantity of heat, expressed in kilocalories, required to heat 1 N of material by 1°C. 14. Thermal Capacity: The property of a material to absorb heat 15. Thermal Conductivity: The thermal conductivity of a material is the amount of heat in kilocalories that will flow through unit area of the material with unit thickness in unit time when difference of temperature on its faces is also unity. 16. Water Absorption: The ability of a material to absorb and retain water and shape of pores, present in the material. 17. Water Permeability: The capacity of a material to allow water to pass through it under pressure Other Properties Thermal Properties: specific heat, thermal expansion and conductivity Technological Properties: The properties of metals and alloys which have a bearing on their processing or application are called technological properties. Castability, machinability, weldability and workability are some of the significant technological properties of metals and alloys