Material Science

Intrinsic dielectric strength

Another test term sometimes used is ‘intrinsic dielectric strength’, which is the maximum voltage gradient a homogeneous substance will withstand in a uniform electric field. This shows the ability of an insulating material to resist breakdown, but practical tests produce lower values for a number of reasons: • Defects, voids, and foreign particles introduced during manufacture which lower the dielectric strength locally, having the effect of reducing the test values as the area tested is increased • The presence of a stress concentration at the electrode edges or points where the electric field is higher than average. • Due to the damaging effect of an electric discharge during testing • Because of dielectric heating, which raises the temperature and lowers the breakdown strength.

Jacob

September 14, 2021

Material Science

Yield criteria and macroscopic aspects of plastic deformation

Gross plastic deformation of a polycrystalline specimen corresponds to the comparable distortion of the individual grains by means of slip. During deformation, mechanical integrity and coherency are maintained along the grain boundaries; that is, the grain boundaries is constrained, to some degree, in the shape it may assume by its neighboring grains. Before deformation the grains are equiaxed, or have approximately the same dimension in all directions. For this particular deformation, the grains become elongated along the directions. For this particular deformation, the grains become elongated along the direction in which the specimen was extended.

Jacob

September 14, 2021

Material Science

Copper Alloys

• Brasses and Bronzes are most commonly used alloys of Cu. Brass is an alloy with Zn. Bronzes contain tin, aluminum, silicon or beryllium. • Other copper alloy families include copper-nickels and nickel silvers. More than 400 copper- base alloys are recognized. Applications - Electrical wires, - roofing, nails, rivets - Automotive radiator - core, lamp fixture, - clutch disk, - diaphragm, fuse clips, - springs - Furniture, radiator - fittings, battery clamps, - light fixtures - Bearings, bushings,…

Jacob

September 14, 2021