Chapter-2-summary-FAIRES (machine design elements) Flashcards
also known as precipitation hardening. It is a heat treatment technique which occurs in certain stainless steel, aluminum and copper alloys. At ambient temperature of metals results in a metal’s increased strength and hardness at the cost of its ductility.
Age hardening
a substance with metallic properties, composed of two or more elements of which at least one is a metal.
Alloy
usually considered as metallic elements added for modifying the properties.
Alloying elements in steel
the characteristic of exhibiting different properties when tested in different directions (as tensile strength “with the grain” or “across the grain”).
Anisotropy
a tendency to fracture without appreciable deformation
Brittleness
a test which the energy absorbed in breaking the specimen is measured as the impact strength of the specimen. The specimen is supported at both ends.
Charpy test
brittleness of metals at ordinary or low temperatures.
Cold shortness
the process of deforming a metal plastically at a temperature below the recrystallization temperature and at a rate to produce strain hardening. Cold-drawn steel is frequently used because it enhances strength, machinability, and surface finish while reducing ductility.
Typically, steel undergoes 10-20% cold working for commercial purposes.
Cold working
the ability of a material to absorb vibrations by converting its kinetic energy to heat through hysteresis. At a particular stress level, cast iron is a much better damping material than steel.
Damping Capacity
a loss of carbon from the surface of steel when the
surrounding medium reacts with the carbon (as oxygen and carbon combining) which occurs during hot rolling, forging and heat treating.
Decarburization
the property that permits permanent deformation before fracture in tension. It is stated that the higher the indices, percentage elongation and percentage reduction of area, the more ductile the material. Although ductility is the opposite of brittleness, there is no distinct boundary. Instead, it can be assumed as:
Ductile material Elongation > 5% in 2-in. gage.
Brittle material Elongation < 5%
in 2-in. gage.
Ductility
ability of a material to be
deformed and return to its original shape.
Elasticity
involves the loss of ductility because of a physical or chemical change of the material.
Embrittlement
part of the carbon content of steel or iron that is in the form
of graphite or temper carbon.
Free carbon
is a temper produced in a wire, rod, or tube by cold drawing.
Hard drawn
materials that have the same structure at all points.
Homogenous materials
materials that have the same properties in all directions.
Isotropic materials
a test which the energy absorbed in breaking the specimen is measured as the impact strength of the specimen. The specimen is supported at one end as a cantilever
Izod test
steel that has been deoxidized with a strong deoxidizing agent (silicon or aluminum) in order to eliminate a reaction between the carbon and the oxygen during solidification.
Killed steel
a term used to describe how easy it is to cut a material.
Machinability
the material’s susceptibility to extreme deformation through rolling or hammering. The more malleable the material is, the thinner the sheet into which it can be formed. Examples:
o Gold
o Aluminum
Malleability
refers to the material’s characteristics concerning
stress and strain. Ultimate strength and percentage elongation are examples.
Mechanical properties
extension in the vicinity of the fracture of a tensile specimen, express as a percentage of the original area.
Percentage elongation
the smallest area at the point of rupture of a tensile specimen divided by the original area.
Percentage reduction area of area
properties such as density, conductivity and coefficient of
thermal expansion.
Physical properties
ability of a metal to be deformed without rupture. In a plastic deformation, the material does not return to its original shape.
Plasticity
the ratio of the lateral strain (contraction) to the longitudinal strain (extension) when the element is loaded with a longitudinal tensile force.
Poisson’s ratio
also called artificial aging, is the precipitation of a constituent from a supersaturated solid solution by holding the body at an elevated temperature.
Precipitation heat treatment
the stress which causes a specified permanent deformation of a material. Usually, 0.01% or less.
Proof stress
is a brittleness in steel when it is red hot.
Red shortness
are those not due to applied loads or temperature gradients.
Exists for various reasons; as unequal cooling rates, cold working and etc.
Residual stresses
incompletely deoxidized steel. Has a surface layer free of slag inclusions and gas pockets resulting to optimum surface on rolled sheets.
Rimmed steel
a process of holding an alloy at a suitably high temperature long enough to permit one or more constituents to pass into solid solution and then cooling fast enough to hold the constituents as a supersaturated solution.
Solution heat treatment
the ability of the materials to resist deformation.
o Higher modulus = stiffer material.
Stiffness
increasing the hardness and strength by plastic deformation at temperatures lower than the recrystallization range.
Strain hardening
a condition produced in a non-ferrous metal through mechanical or thermal treatment
Temper
the capacity of a materials
to withstand a shock load without breaking.
Toughness
frequently applied to brittles materials, it is the result of a transverse bend test to which the specimen is mounted as a simple beam. Also known as rupture modulus.
Transverse strength
the same as strain hardening
Work hardening
steel that has been hammered, rolled or drawn in the process of manufacture.
o Plain carbon
o Alloy steel.
Wrought steel
