Materials in Mechanical Design Flashcards
The food of design
Materials
It refers to the one that performs well, is good value for money and gives pleasure to the user.
Successful product
Six broad classes of Engineering materials
Metals, Polymers, Elastomers, Ceramics, Glasses, Composites
This class has relatively high moduli.
Metals
Metals can be made strong through what method?
By alloying, by mechanical and heat treatment
A high-strength alloy with ductilities as low as 2%.
Spring steel
Metals are prey to fatigue partly due to what?
Their ductility
Of all classes of material, they are the least resistant to corrosion.
Metals
A class of engineering material that has high moduli but are brittle.
Ceramics and Glasses
They have no ductility and have low tolerance for stress concentrations or high contact stresses.
Ceramics
They are stiff, hard and abrasion-resistant. They retain their strength to high temperatures and they resist corrosion well.
Ceramics
They have low moduli, roughly 50 times less than those of metals, but can be as strong as metals.
Polymers and Elastomers
What is the property of polymer at 20 degrees celcius?
Tough and flexible
What is the property of polymer at 4 degrees celcius of a household refrigerator?
Brittle
What is the property of polymer at 100 degrees celcius of boiling water?
Creeps rapidly
What temperature do the polymers no longer have useful strength?
Above 200 degrees celcius
TRUE OR FALSE. When combinations of properties, such as strength per-unit-weight, are important, polymers are as good as glasses.
FALSE [ Glasses - Metals ]
They are easy to shape, corrosion resistant, have low coefficients of friction and have large elastic deflections.
Polymers
This class combines the attractive properties of the other classes while avoiding some of their drawbacks.
Composites
They are light, stiff and strong, and can be tough.
Composites
Composites cannot be used above 250 degrees celcius because?
The polymer matrix softens
At what temperature do composites have outstanding performance?
Room temperature
Only when do the designers use composites?
When the added performance justifies the added cost
It defines the behavior of materials under the action of external forces.
Mechanical properties of materials
These external forces are also called as?
Loads
How do we determine the mechanical properties of metals ?
By the range of usefulness of the metal and establish the service that is expected.
What are the 7 most common properties?
Strength, ductility, hardness, brittleness, toughness, stiffness, Impact resistance
It is the ability to undergo some permanent deformation without rupture (brittle).
Plasticity
It is the ability of a material to resume its normal shape after being stretched or compressed.
Elasticity
It is a property of materials which enables it to withstand permanent deformation.
Brittleness
It is a property of a material that enables it to withstand shock or impact.
Toughness
It is a property of a material which permits it to be hammered or rolled into sheets.
Malleability
It is a property of a solid body by virtue which they resist from being broken into a fragment.
Cohesion
It is a property that enables metals to resist deformation load.
Strength
It is the ability of a material to resist scratching, abrasion, cutting or penetration.
Hardness
It is the capacity of a material to withstand destruction under action of external loads
Strength
TRUE OR FALSE. The stronger the materials, the lesser the load it can withstand.
FALSE [ Lesser - Greater ]
Good examples of elastic materials
Heat-treated springs and rubber
It is also called dynamic hardness.
Rebound Hardness
It is the ability of materials to oppose the scratches to the outer surface layer due to external force.
Scratch Hardness
It is the ability of materials to oppose the dent due to punching or external hard and sharp objects.
Indentation Hardness
It is the is the resistance of a material to elastic deformation or deflection.
Stiffness
It is the ability of a metal
to resist suddenly applied loads.
Impact strength
It is a property of a material which enables it to be drawn out into a thin wire.
Ductility
It is the long effect of repeated
straining action which causes the strain or break of the material.
Fatigue
It is used to describe the fatigue of material under repeatedly applied forces.
Fatigue
Examples of malleable materials
Aluminum, copper, tin, lead
It has high compressive strength but low in tensile strength.
Brittle metals
Examples of brittle metals
Cast iron, glass
It is a slow and progressive deformation of a material with time at a constant force.
Creep
The simplest type of creep deformation
Viscous flow
The force for a specified rate of strain at constant temperature.
Creep strength
They are hard, non-adhesive, cold and
smooth, they are very often shiny and strong.
Metals
A process by which metals react with oxygen in water and air
Oxidation or rusting
A reddish- or yellowish-brown flaky coating of iron oxide that is formed on iron or steel, especially in the presence of moisture.
Rust
Examples of metals that are toxic
Lead or mercury
Metals can be divided into two main
groups
Ferrous metals and non-ferrous metals
It is considered to be of little use as an engineering material because it is too soft and ductile.
Pure iron
Some iron cools and changes from a liquid to a solid become misaligned,
creating areas of weaknesses called?
Dislocations
It is a mixture of two or more chemical elements and the primary element is a metal.
Alloy
By adding carbon to the iron however, we can produce a range of alloys with quite different properties called?
Carbon steels
It has a carbon content between 0.1%
and 0.3%. Less ductile but harder and tougher than iron, grey color, corrodes easily.
Mild Steel
It has a carbon content between
0.3% and 0.7% carbon. It is harder
and less ductile than mild steel, tough and have a high tensile strength.
Medium carbon steel
It has a carbon content between 0.7%
and 1.3% carbon. It is very hard
and brittle material.
High carbon steel `
An element that prevents rusting with an oxide film.
Chromium
It is an alloy of iron (94%), carbon
(3%) silicon (2%) and some traces of magnesium, sulphur and phosphorous.
Grey Cast Iron
A chemical element that makes the alloy magnetic and improves elasticity.
Silicon
A chemical element that improves strength and prevents corrosion.
Nickel
A chemical element that makes the alloy harder and heat-resistant.
It’s used to make stainless steel.
Manganese
A chemical element that makes the alloy harder and tougher and more rustproof.
Chromium
A chemical element that makes the steel harder, more heat-resistant
and prevents corrosion.
Tungsten
They are metals that don’t contain iron.
Non-ferrous metals
It’s the most abundant metal in the earth’s crust and after steel, is the most widely used of all the
metals.
Aluminum
It’s a pure metal that is the world’s third most important metal, in terms of volume of consumption.
Copper
It covers a wide range of
copper-zinc alloys.
Brass
It has very
good anticorrosive properties and it’s
resistant to wear.
Brass
It’s shiny and silvery white. It reacts
very strongly with oxygen.
Magnesium
It doesn’t oxidize at room
temperatures and is very soft.
Tin
It is toxic when its fumes are inhaled
Lead
It’s an alloy of copper and tin.
Bronze
It is a bluish grey shiny metal.
Zinc
It contains Iron as a major component
Ferrous alloys
It does not contain Iron as a major
component.
Non-ferrous alloys
The major categories of manufacturing processes
– Metal Casting,
– Bulk/Metal Deformation,
– Sheet Metalworking/metal forming,
– Machining,
– Polymer Processing,
– Powder Metallurgy,
– Finishing and
– Assembly.
Other non-value added processes of manufacturing processes
– Inspection,
– Testing, and
– Quality assurance.
A manufacturing process that creates complex shapes from molten metal.
Metal casting
It creates intricate wax patterns
that are coated with slurry, the wax melted out, then filled with molten metal.
Investment casting
It uses permanent molds into which low melt point metals such as zinc are injected under pressure.
Die casting
Two types of die casting machines
Hot and cold chamber
It is used to transform bulk
materials in the form of billets, blooms, and slabs as they come from a mill into other shapes such as pipe or bars.
Metal deformation
It is a common method for making
plastic bottles.
Blow molding
This is a common method of making tires.
Polymer Processing
It is another compression molding
technique in which the heated polymer is injected into the closed mold.
Transfer molding
It encompasses many final operations
that make a part ready for assembly.
Finishing
It is where the different parts that
compose a finished product come together.
Assembly
