PROPERTIES OF ENGINEERING MATERIALS.docx

PROPERTIES OF ENGINEERING MATERIALS 1. **PHYSICAL PROPERTIES**- observable and measurable values describes the state of physical System. EXAMPLES **MASS DENSITY**- material's mass per unit of volume **WEIGHT DENSITY**- materials weight per unit volume **DIELECTRIC STRENGHT**- maximum elect...

PROPERTIES OF ENGINEERING MATERIALS 1. **PHYSICAL PROPERTIES**- observable and measurable values describes the state of physical System. EXAMPLES **MASS DENSITY**- material's mass per unit of volume **WEIGHT DENSITY**- materials weight per unit volume **DIELECTRIC STRENGHT**- maximum electric field that a pure material can withstand without breaking down **ELECTRICAL RESISTIVITY**- measures how strongly a material can resist electric current **MELTING POINT**- temperature which it changes state from solid to liquid **HEAT DISTORTION TEMPERATURE**- temperature at which a polymer plastic deforms under specific loads **REFRACTIVE INDEX**- dimensionless number that indicates light bending ability of that medium. **SPECIFIC GRAVITY**- ratio of the density of a substance to that of a standard substance **THERMAL CONDUCTIVITY-** ability of a material to conduct heat **COEFFICIENT OF EXPANSION-** tendency of a material to change its shape, area, volume in response to change in temperature. **SPECIFIC HEAT-** quantity of heat required to raise the temperature of one gram of a substance by one Celsius degree 2. **CHEMICAL PROPERTIES- changing its chemical identity through chemical reactions** EXAMPLES **CORROSION-** deterioration of a metal as a result of reaction between in and the environment **CAUSTIC BRITTLEMENT-** material of a boiler which are under stress becomes brittle due to accumulation of caustic substance. 3. **MECHANICAL PROPERTIES- behaviour of materials under the action of external forces called loads** **STRESSES-** measure of a force acting on a unit area of an imaginary section through a body **FORCE-** an influence that causes the object to undergo a certain change **LOADS-** external forces acting on a rigid body **STRAIN-** deformation of solid due to stress **TENSION-** two sections of material on either side of a plane tend to be pulled apart **TENSILE STRESS-** force which point away from its point **TENSILE STRAIN-** measures the deformation of an object under tensile stress **COMPRESSION-** applies a load that squeezes the ends of a cylindrical specimen **COMPRESSICE STRESS-** force which points towards its point of application **COMPRESSIVE STRAIN-** change in length per original length due to compressive force **SHEARING-** applying a load parallel to a plane which caused the material on one side want to slide across the other side **BENDING-** applying load in manner that causes the material to curve. **TORSION-** application of a force that causes twisting in a material. **Elastic limit** is the greatest stress the material can withstand without any measurable permanent strain remaining on the complete release of load. **Yield strength** is the stress required to produce a small-specified amount of plastic deformation. **Proportional limit** is the highest stress at which stress is linearly proportional to strain. **Ultimate tensile strength** is an engineering value calculated by dividing the maximum load on a material experienced during a tensile test by the initial cross section of the test sample. **True fracture strength** is the load at fracture divided by the cross sectional area of the sample **DUCTILITY-** ability of a material to be stretched into wires permanently without fracture **MALLEABILITY-** ability of metal to be hammered, rolled, or pressed into various shapes without fracture **BRITTLENESS-** tendency of a material to fracture without any plastic or little deformation **STIFFNESS-** tendency of an element to return to its original form after being subjected to a force **STRENGHT-** measures how much stress can be applied to an element before it deforms permanently **HARDNESS-** measures a materials resistance to surface **CREEP-** slow and continuous deformation that occur in the dimensions of the material under a constant stress, usually at high temp. **FRACTURE-** breakage of a material into separate parts under stress **FATIGUE-** changes in the mechanical properties of the material under the action of repeated stress **ELASTICITY-** property of a material to return exactly to its original shape on removal of straining force **PLASTICITY-** ability of a material to not return to its original shape when it deforms **HOOKE'S LAW-** stress is linearly proportional to strain **MODULUS OF ELASTICITY-** resistance to elastic deformation **YOUNG'S MODULUS-** ratio of uniaxial stress over uniaxial strain **SHEAR MODULUS-** ratio of shear stress over shear strain **BULK MODULUS-** ratio of normal stress over volumetric strain **OTHER PROPRTIES AND CHARACTERISTICS OF MATERIALS** **THERMAL PROPERTIES-** response of a material to application of heat **HEAT CAPACITY-** amount of energy required to produce a unit temp rise **THERMAL EXPANSION-** increase in length, are, volume in response to increase in temp. **THERMAL CONDUCTION-** transport of thermal energy from high to low temp regions of a material Solid materials, heat is transported by vibrational lattice waves or phonos Ceramics and polymers- poor thermal conductors because free electron concentrations are low and phonon conduction predominates **THERMAL STRESSES-** induced in a body as a result of changes in temp **THERMAL SHOCK RESISTANCE-** capacity of material to withstand plastic deformation under thermal stress **BIMETAL STRIP-** two metals bonded together with different coefficient of expansion **MAGNETISM-** phenomenon where materials exert an attractive or repulsive force or influence on other materials **MAGNETIC SUSCEPTABILITY-** measures the response of electrons to a magnetic field **MAGNETIC DIPOLES-** generated by moving electrically charged particles, imaginary line of force that indicate the direction of force **MAGNETIC FIELD VECTORS-** externally applied magnetic field **MAGNETIC INDUCTION-** magnitude of the internal field strength within a substance that is subjected to a magnetic field **PERMEABILITY-** property of the specific medium through which the magnetic field passes and in which magnetic induction is measured **MAGNETIZATION OF A MATERIAL-** dependent on susceptibility and magnetic fie;d strength **FERROMAGNETIC-** certain materials strongly attract each other **ANTIFERROMAGNETIC-** magnetic moments of each atom are arranged in such way that every second moment is in the opposite direction to the first. Alternate **FERRIMAGNETIC-** magnetic moments have opposing moments