Transcript Slide 1

Polymers for Heavy
Engineering
Silicones, or polysiloxanes
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Silicones, or polysiloxanes, are inorganic-organic
polymers with the chemical formula [R2SiO]n, where R =
organic groups such as methyl, ethyl, and phenyl.
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These materials consist of an inorganic silicon-oxygen
backbone (...-Si-O-Si-O-Si-O-...) with organic side
groups attached to the silicon atoms, which are fourcoordinate.
Silicones, or polysiloxanes
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In some cases organic side groups can be
used to link two or more of these -Si-Obackbones together. By varying the -Si-Ochain lengths, side groups, and crosslinking,
silicones can be synthesized with a wide
variety of properties and compositions.
They can vary in consistency from liquid to
gel to rubber to hard plastic. The most
common type is linear polydimethylsiloxane
or PDMS
Silicones, or polysiloxanes
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Service temperature to about 260C
Good chemical resistance, low water
absorption, good electrical properties, &
available in flame retardant grade
In the plumbing and automotive fields,
silicone grease is often used as a lubricant. In
plumbing, the grease is typically applied to Orings in faucets and valves.
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In the automotive field, silicone grease is
typically used as a lubricant for brake
components since it is stable at high
temperatures, is not water-soluble
Epoxy
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Epoxy or polyepoxide is a thermosetting
epoxide polymer that cures (polymerizes and
crosslinks) when mixed with a catalyzing
agent or "hardener"
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The family of epoxy resin includes
epichlorohydrin with bisphenol-A (range from
low viscosity liquids to high molecular weight
solids).
Epoxy
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Epoxy adhesives are a major part of the class of
adhesives called "structural adhesives" or
"engineering adhesives"
These high performance adhesives are used in the
construction of aircraft, automobiles, bicycles, golf
clubs, skis, snow boards, and other applications
where high strength bonds are required.
In general, epoxy adhesives cured with heat will be
more heat- and chemical-resistant than when cured
at room temperature.
Epoxy
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Novolacs are another important class that
offer higher thermal properties and improved
chemical resistance
The cycloaliphatics types important for the
applications requiring high resistance to
wheatering
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Epoxies typically are not used in the outer
layer of a boat because they are deteriorated
by exposure to UV light
In the aerospace industry, epoxy is used as a
structural matrix material which is then
reinforced by fiber. Typical fiber
reinforcements include glass, carbon, Kevlar,
and boron.
Rubber Applications in Earthquake Bearing
Industry
1.0 Introduction
INTRODUCTION
Bearings
- structural joints that are
installed between a structure and its
foundation.
The
bearing is very stiff and strong in
the vertical direction, but flexible in the
horizontal direction.
HOW THE BEARING WORKS
Figure: Base-Isolated and Fixed-Base Buildings
•A
base isolated structure is supported by a
series of bearing pads which are placed
between the building and the building's
foundation
2.0 How The Bearing work?
As
a result of an earthquake, the ground beneath
each building begins to move.
Each building responds with movement which tends
toward the right.
The building's displacement in the direction opposite
the ground motion is actually due to inertia.
2.0 How The Bearing work?
In
addition to displacing toward the right, the un-isolated
building is also shown to be changing its shape-from a
rectangle to a parallelogram. –deforming
The primary cause of earthquake damage to buildings is the
deformation which the building undergoes as a result of the inertial
forces acting upon it.
2.0 How The Bearing work?
The
base-isolated building retains its original,
rectangular shape.
It is the elastomeric bearings supporting the building
that are deformed.
It implies the inertial forces acting on the base-isolated
building have been reduced.
3.0 Elastomeric Bearings
ELASTOMERIC BEARINGS
Fig: Basic structure of
rubber bearing
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Consist of thin rubber sheets bonded onto thin steel plates
and combined with an energy dissipation mechanism.
The rubber sheets are vulcanized and bonded to the thin
steel plates under pressure and heat.
it is designed in such a way that bearing is very stiff and
strong in vertical direction, but flexible in horizontal direction.
Thick mounting steel plates are bonded to the bottom and top
surfaces allowing the isolator to be firmly connected to the
foundation below and the superstructure above.
4.0 Types Of Elastomeric Bearing
TYPES OF ELASTOMERIC
1. LEAD RUBBER BEARINGS (LRB)
•a
bigger laminated bearing
•manufactured from layers of low-damping natural rubber
sandwiched together with layers of steel and a lead cylinder plug
firmly fitted in a hole at its center to deform in pure shear.
•lead inserted as center
core of bearing dissipates
the energy of earthquake
while the rubber, reinforced
with steel plates, provide
stability, supports structure
and isolate vibration.
•LRB provide initial rigidity,
due to the high elastic
stiffness of lead, which is
essential for minor lateral
loads.
4.0 Types Of Elastomeric Bearing
2. HIGH DAMPING RUBBER BEARING (HDRB)
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Consists of thin layers of high damping rubber
sandwiched between steel plates.
High-damping rubber is filled rubber compound with
inherent damping properties due to the addition of
special fillers, such as carbon and resins. The addition
of fillers increases the inherent damping properties of
rubber without affecting its mechanical properties.
When shear stresses are applied to high-damping
rubber, a sliding of molecules generates frictional heat
which is a mechanism of energy dissipation.
4.0 Types Of Elastomeric Bearing
3. Hybrid type: Lead High-damping Rubber Bearing
(LHDRB)
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Consist of layers of high-damping rubber
sandwiched between steel plates and a smaller
diameter lead cylinder plug firmly fitted in a hole
at its center.
LHDRB has both an initial rigidity, due to the
presence of the lead plug, and a continuous
energy dissipation mechanism, due to the
damping properties of the high-damping rubber.
5.0 Requirements
Requirements for Rubber Bearings
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Mechanical and damping properties of the bearing
must remain constant over the whole life of the
structure
Ability to return to its original configuration and
dimensions when unloaded
Elastomeric bearings must be strong and stiff for
vertical loadings and flexible under shear stresses
The base isolator must support the vertical load of the
structure with a large safety factor.
The sheer stiffness of the isolator must be low enough
to attenuate the majority of the frequency components
in an earthquake on that site.
5.0 Requirements
6. The isolator must be stiff enough vertically to
power significantly amplification of any vertical
component in the earthquake.
7. During an earthquake, the building will move
sideways on the isolators. At the extremes of the
movements, the bearing must continue to
support the vertical load of the structure.
8. The damping in the isolators must be sufficient to
prevent a build- up of amplitude in the structure
during an earthquake.
9. Motion of the structure during high winds should
not be sufficient to disturb the occupants.
10.The isolator should provide a restoring force so
the building will always return to its original rest
position.
6.0 Raw Materials
BEARING MATERIALS
Natural Rubber and Polychloroprene
• Ethylene Propylene Rubber as a promising
alternative to Natural Rubber and
Polychloroprene will be
consider as the raw
material for
earthquake bearing elastomer.
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Processing
Flow Chart Seismic
Rubber
Bearings