Compression test on neoprene pads

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General InformationExperimental Procedure

Compression test on Neoprene Rubber Pads

(As a part of TA assignment)

Abhimanyu Sable

Department of Civil Engineering

[email protected]

November 1, 2013

Abhimanyu Sable Indian Institute of Technology, Bombay


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Overview

1 General InformationSignificance

ComparisonApplications

2 Experimental Procedure

Hardness TestingProcedure



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SignificanceComparisonApplications

General Information

Neoprene is a synthetic rubber that has been around over 75

years.It is used in a wide variety of applications, such as laptopsleeves, electrical insulation, liquid and sheet appliedelastomeric membranes or flashings and automotive fan belts.

It is similar to natural rubber, but has durability and

resistance to environmental stresses that make it superior insome applications.



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General Information

From stability point of view, Neoprene is extremely resistant

to wear and weathering. It resists damage by chemicals suchas acids, ozone, oils and oxygen which can harm other typesof rubber.

Neoprene is also resistant to heat and can work in both coldand hot environments, although it does get stiffer in the cold.

It is resistant to flame, although extremely high temperaturescan damage it.


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General Information

Mechanical Resistance

Neoprene performs well under a variety of mechanical stresses.

It resists impact well, absorbing a considerable amount offorce without being damaged.

It also has good compression set and rebound rate; when it iscompressed and released, it springs back to its original shapefairly quickly.

It also resists abrasion damage and tearing and will not crackeasily from repeated bending.


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General Information

Uses With Other Materials

Neoprene is very useful in combination with a range of other

materials.It adheres well to metal, which makes it useful for applicationswhere the two have to be joined.

It is also useful in making bandages and binders and as acoating.

Manufacturers can even add it to asphalt or concrete to makeelasticized pavement.


Significance


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Significance

Neoprene rubber pads are elastomer bearings much easier toinstall in bridge as compare to other kind of bearings used andrequire little maintenance.

Compared to other elastomers neoprene pads does notundergo stiffening at low temperatures.

High durability/ life of neoprene elastomer rubber pads.

Neoprene pads allow smooth transfer of load fromsuperstructure to substructure.

It allows for Beam rotation at the bearing due to deflection of

beam under load.They also allow lateral and longitudinal movement of thebeam caused by thermal forces. Laminated neoprene padshave ability to give and take shear which absorbs thermal

expansion and contraction.Abhimanyu Sable Indian Institute of Technology, Bombay

Significance


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Plain Rubber Block v/s Laminated Elastomer Bearing

Capability of plain rubber block increases as the number oflaminations increase.

Plain rubber carries less load for the same strain level, thatwill be one of the observations of the experiment.


Significance


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Plain rubber block under vertical load compressed down whereas a laminated bearing bulge out with each laminationsabsorbing most of the vertical load.

Figure:


G l I f iSignificance


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Reaction against the horizontal load comparedThe resistance against excessive deformation for horizontalload is high in case of laminated neoprene pads

Figure:


G l I f tiSignificance


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gComparisonApplications

Seismic isolation

Seismic isolation separates the structure from the harmfulmotions of the ground by providing flexibility and energydissipation capability through the insertion of the isolateddevice so called isolators between the foundation and thebuilding structure.

Figure:


General InformationSignificance


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gComparisonApplications

Figure:




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Figure:




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Vibration Mounts

Engines

Internal combustion enginesGenerator sets

Rotating equipments

PumpsCompressorsWindmills

Electronic equipments

Instrument panels

Switch cabinets

Marine/offshore applications


General InformationSignificanceC i


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As bearing under bridge deck

Figure: Bridge Bearings


General Information Hardness Testing


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Experimental Procedureg

Procedure

Testing of hardness using Durometer

Durometer is one of several measures of the hardness of amaterial.

Hardness may be defined as a materials resistance topermanent indentation.

Unit is Shore A.

Students are supposed to take readings of hardness beforeproceeding with the compression testing of the samplespecimen.

Four reading on each side of the rubber block adding to 24

reading for one block. Readings need to taken for all the 3blocks

Mean of the readings for each block indicates the hardnesslevel for that block




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Experimental Procedureg

Procedure

Figure: Testing rubber for hardness




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Experimental Procedure Procedure

Figure: Mechanism


General InformationE i l P d

Hardness TestingP d


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Procedure for Experiment

The test specimens are classified in terms of different hardnessvalues.

Each block is placed in the test apparatus in the position

specified by helper.There are 5 indicators on the top. 4 indicate deflection(deflection transducers) and the other 1 indicate load.

The apparatus is strain controlled meaning readings need to

be taken at specified load levels. Hence consider one of thedeflection indicator as reference.


General InformationE i t l P d

Hardness TestingP d


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Each person takes reading observed in each indicator upon thecall of person taking reference indicator reading. The call has

to be made at 2mm levels.Maximum allowable deflection should not exceed 12 mm (orthe value specified by Nissar Khan Sir)

So there are 7 reading for each test.


General InformationE perimental Proced re

Hardness TestingProced re


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The reference point should be taken when the surfaces of themachine and the block just touches each other.

Once they get the deflection v/s load ordinates, they are

supposed to plot the respective values of each specimen onthe same graph indicating their hardness levels.

Then for a constant strain, get the three stress (resistance)values. And for a constant stress get three strains(deformation) values. This forms the reference for correcting

journals and comparing the results obtained by differentbatches.



Hardness TestingProcedure


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The End


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Compression test on neoprene pads