Engg. materials.ppt
- 1. 5. Engineering Materials Materials and Civilization, Materials and Engineering, Classification of Engineering Materials, Mechanical Properties of Materials: elasticity, plasticity, strength, ductility, brittleness, melleability, toughness, resilience, hardness, machinability, formability, weldability. Properties, Composition, and Industrial Applications of materials: metals (ferrous- cast iron, tool steels, stainless steels and non ferrous- Aluminum, brass, bronze ), polymers (natural and synthetic , thermoplastic and thermosetting), ceramics (glass, optical fibre glass, cements), composites ( fibre reinforced, metal matrix), smart materials (piezoelectric, shape memory, thermochromic, photochromic, magnetorheological), Conductors, Semiconductors and insulators, Organic and Inorganic materials. Selection of materials for engineering applications.
- 2. Materials and Civilization Civilization comes from latin word civilis meaning civil and civilas meaning city # Civilization may be defined as the sum total of all progress made by man in every sphere of action. # Following are the sequences of civilization and happening in their periods: 1. Stone age is associate with the use of stone as materials. 2.Bronze age, the innovation of smelting and casting of materials started. 3. Iron age coincided with wide spread use iron or steel for their cutting tools and weapons. # We conclude that the progress of civilization is strongly related to the development of materials and engg.
- 3. Summary of Classification of Engineering Materials and Properties
- 5. Mechanical Properties of Materials Elasticity Elasticity (or stretchiness) is the physical property of a material that returns to its original shape after the external forces) that made it deform or distort is removed. The relative amount of deformation is called the strain. plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. Plasticity
- 6. Strength of a material is its ability to withstand an applied load without failure. The applied load may be tensile, compressive, or shear. A load applied to a mechanical member will induce internal forces within the member called stresses. The stresses acting on the material cause deformation of the material. Deformation of the material is called strain.
- 7. Ductility is a solid material's ability to deform under tensile stress; this is often characterized by the material's ability to be stretched into a wire. Malleability, a similar property, is a material's ability to deform under compressive stress; this is often characterized by the material's ability to form a thin sheet by hammering or rolling. Both of these mechanical properties are aspects of plasticity, the extent to which a solid material can be plastically deformed without fracture.
- 8. Brittleness Tendency of a material to fracture or fail upon the application of a relatively small amount of force, impact, or shock. Toughness Property of a material that enables it to absorb and distribute within itself relatively large amounts of energy (both stresses and strains) of repeated impacts and/or shocks, and undergo considerable deformation before fracturing or failing. Toughness is Opposite of Brittleness.
- 9. Resilience is the property of a material to absorb energy when it is deformed elastically and then, upon unloading to have this energy recovered. In other words, it is the maximum energy per unit volume that can be elastically stored. Hardness Resistance of a material to deformation, indentation, or penetration by means such as abrasion, drilling, impact, scratching, and/or wear. Machinability refers to the ease with which a metal can be machined to an acceptable surface finish. Materials with good machinability require little power to cut, can be cut quickly, easily obtain a good finish, and do not wear the tooling much; such materials are said to be free machining.
- 10. Formability is the ability for a given metal workpiece to undergoing plastic deformation without damage. Weldability, also known as joinability,of a material refers to its ability to be welded. Many metals and thermoplastics can be welded, but some are easier to weld than others. A material's weldability is used to determine the welding process and to compare the final weld quality to other materials.
- 11. Stiffness is the resistance of an elastic body to deformation by an applied force Fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material. Creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and near melting point. Creep always increases with temperature.
- 12. Criteria for Selection of Material # Design of any machine element begins with the selection of a material. # There are large number of engg. Materials available and many more are adding up day by day. Д Choice of material depends upon the following factors: 1. Availability of material 2. Cost of material 3. Manufacturing considerations 4. Material properties.
- 13. Material Selection Process 1. Analysis of desired material properties 2. Screening of candidate materials 3. Selection of most suitable material
- 14. 6. Centroid, Centre of Gravity and Moment of Inertia: Difference between centre of gravity and centroid. Determination of position of centroid of plane geometric figures of I, U, H, L, T, C, Circular and Triangular Sections. Centroid of Composite Areas. Determination of position of Centre of Gravity (CG) of regular solids viz. Right Circular Cone, Solid Hemisphere, thin Hollow Hemisphere. Area moment of inertia & mass moment of inertia, Polar moment of inertia, Parallel axes Theorem (or transfer formula), Perpendicular axes Theorem, Radius of gyration, determination of area Moment of Inertia of I, U, H, L, T, C, Circular and Triangular Sections along various axes. Mass moment of Inertia of Circular Ring, Disc, Cylinder, Sphere and Cone about their axis of symmetry and other axes.