Post on 05-Aug-2015
Mechanical Properties of Materials
Introduction and Agenda
Materials Properties- helps to determine how to make things with it- helps to determine the processing conditions- helps and constrains process optimization
Processes- forming, cutting, non-traditional, joining, surface treatments, electronics components, …
Materials
Nanomaterials, shape-memory alloys, superconductors, …
Ferrous metals: carbon-, alloy-, stainless-, tool-and-die steels
Non-ferrous metals: aluminum, magnesium, copper, nickel, titanium, superalloys, refractory metals, beryllium, zirconium, low-melting alloys, gold, silver, platinum, …
Plastics: thermoplastics (acrylic, nylon, polyethylene, ABS,…) thermosets (epoxies, Polymides, Phenolics, …) elastomers (rubbers, silicones, polyurethanes, …)
Ceramics, Glasses, Graphite, Diamond, Cubic Boron Nitride
Composites: reinforced plastics, metal-, ceramic matrix composites
Physical Properties
Property Application (e.g.)
Density, r = mass/volume Drop forging, hammering
Specific heat Coolant in machining
Thermal conductivity Cutting titanium
Coeff of linear thermal expansion, a = DL/(L DT) Compensation in Casting, …
Melting point Brazing, Casting, …
Electrical conductivity EDM, ECM, Plating
Magnetic properties Magnetic chucking
Chemical Properties:-• Corrosion Resistance• Oxidation• Flammability• Toxicity
The MECHANICAL PROPERTIES of a material are those properties that involve a reaction to an applied load.
• The mechanical properties of metals determine the range of usefulness of a material and establish the service life that can be expected.
• Mechanical properties are also used to help classify and identify material.
• The most common properties considered are strength, ductility, hardness, impact resistance, and fracture toughness.
Definition
Mechanical Properties:-• Strength – it is the ability of a material to resist failure under working
conditions
• Ductility – it is the ability of a material to be drawn into wires, increase in length and decrease in cross sectional area occur, tensile forces are involved
• Malleability – it is the property of a material to be hammered into thin sheets, compressive forces are involved, increase in surface area in all directions, decrease in cross sectional area
• Brittleness – absence of ductility, when the material fail without warning in working conditions
• Elasticity – the property of a material that returns to its original shape after stress (e.g. external forces) that made it deform or distort is removed
• Plasticity -- material cannot regain its original shape when the external load is removed, permanent deformation takes place
• Toughness – the ability of a material to absorb load shock etc.
• Hardness -- the ability of a material to resist scratches, chemical reaction marks, indentations etc.
• Machinability – the property of a material that can be shaped by hammering, pressing, rolling
• Stiffness-- it is the ability of a material to resist elastic deformation
• Resilience – ability to resist deformation till elastic range
Ductility
Measures how much the material can be stretched before fracture Ductility = 100 x (Lf – Lo)/Lo High ductility: platinum, steel, copperGood ductility: aluminumLow ductility (brittle): chalk, glass, graphite
Hardnessresistance to plastic deformation by indentation
Failure under impact
CharpyIzod
pendulum
scale
pointer starting position
sample placed here
CharpyIzodIzod
pendulum
scale
pointer starting position
sample placed here
Impact tests are used in studying the toughness of material. A material's toughness is a factor of its ability to absorb energy during plastic deformation. Brittle materials have low toughness as a result of the small amount of plastic deformation that they can endure. The impact value of a material can also change with temperature. Generally, at lower temperatures, the impact energy of a material is decreased. The size of the specimen may also affect the value of the Izod impact test because it may allow a different number of imperfections in the material, which can act as stress risers and lower the impact energy.
Application: Drop forging
Shear stress and Strain: the torsion test
L
g
C
C’
q
T
T
L
g
T
T
D
d
T = torque,J = polar moment of inertia J = r2 dACylindrical shell: J = (p D4-d4)/32
Angle of twist: q = TL/GJShear stress: t = Tr/JMaximum shear stress = tmax = TR/JShear strain = g = rq/L
G: Modulus of rigidity
Which properties do the following materials possess?
Material Properties
aluminium lightness ; strength
rubber elasticity ; insulation
ceramics thermal resistivity
steel strength
copper conductivity ; corrosion resistance
lead high density; ductility
nylon strength ; toughness
cast iron damping capacity
wood insulation ; environmental friendliness
Material Application
aluminium foil; aircraft; window frame
rubber tyres,; seal; gasket
ceramics furnace; brick
steel section; pipe
copper pipe; cables
lead storage battery; radiation protection ballast; bullets
nylon rope; clothing
cast iron engine block; valves
wood furniture; deck
Applications
Summary
Knowledge of materials’ properties is required to
Select appropriate material for design requirementSelect appropriate manufacturing processOptimize processing conditions for economic manufacturing…
Materials have different physical, chemical, electrical properties
Presented by—Akash Sharma