Glossary: Material Science
Here's a short list of material science definitions so that you
can understand a few of the numbers that are typical on material
data sheets. It will help when you want to compare various types
of metals and composites that are used in bicycles, after car parts
and various other wheeled toys and accessories!
AISI/SAE Designations: a standard numerical
designation that identifies a specific metal and its impurities,
followed by a series of numbers that indicates the heat or mechanical
treatments applied. Allows for uniform trading of material, consistent
application and identification of treatment and associated mechanical
properties.
American Iron and Steel Institite (AISI)
Society of Automotive Engineers (SAE)
Alloying: Process of adding-in various
impurities to a material to improve or change the mechanical properties
of the original product.
Annealing: This refers to a process
of heat treatment. Materials are exposed to a specific temperature
and then slowly cooled. It is typically applied to a particular
material to a) change its microstructure, b) increase ductility
or c) relieve stress. It is an important process to modify or create
particular mechanical properties suitable for a specific application.
Anodizing: An electro or electrochemical
method to coat the exterior of a metal with a protective finish
using various metal's natural ability to create a surface oxide.
In some metals, it is the amount of voltage applied to the surface
that determines the ultimate colour (often subtle colour variations
occur where the metal does not transmit a consistent voltage).
It is a preferred method of making a surface corrosion resistant
because it is environmentally acceptable and the weight of the final
finish is lower than that of a typical painted alternative.
Elastic Deformation: When applying
a pulling force to a particular material, the internal molecular
bonds will stretch to accommodate these forces. In the absence of
this force the material will return to its original shape. Elastic
deformation then is a NON permanent form of physical change.
Heat Treatment: a process of continuously
heating and cooling metals (via air, oil or water) to create an
appropriate microstructured material with a given set of mechanical
properties. Its success is a function of the composition, time/temperature
relationship, cooling process and shape of the object being treated.
Plastic Deformation: The point in
time where the tension applied is so strong that the molecules within
a material are being torn apart. Permanent change in shape is typical,
and functionality may be affected to the point of material fatigue
or fracture.
Tensile Strength: The maximum strength
a material can sustain in tension (ie. being pulled apart along
its axis). The material typically experiences elastic and then plastic
deformation to peak at its tensile strength, just before fatique.
All deformation up until this point is uniformly experienced by
the entire sample, at which point the tensile strength is research
and with continued exposure a "weak link" is created and
sample fractures.This number gives us a relative understanding of
the strength of various material.
Young's Modulus of Elasticity: This
is a material's resistance to elastic deformation. In other words
.. How much load must one apply to cause a given compression or
stretch? The greater the number the stiffer the material.
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