rubber compound preparation for conveyor belt

DEVELOPMENT OF RUBBER COMPOUND FOR CONVEYOR BELT

USING BIO-FILLERS

Conveyor belts manufactured in laminated layers from plastics, fibres and natural and

synthetic rubbers are used to transport a wide variety of materials.

Based on application, conveyor belts are classified into following groups:

• Highly resistant conveyor belts

• Oil resistant conveyor belts

• Food conveyor belts

• Underground conveyor belts

Based on minimum tensile strength, conveyor belts are classified into three categories:

� M-24 (Min. tensile strength: 24 MPa)

� M-17 synthetic

� N-17 (Min. tensile strength: 17 MPa)

Conveyor belts are composite products composed of matrix (generally rubber) and

filler (fibres and particulate fillers).

Matrices used in conveyor belts are

�Natural rubber

�Styrene-Butadiene Rubber

�Chloroprene

�Polyvinylchloride-Nitrile Rubber Blend

�Polyvinylchloride

�Ethylene-Propylene Rubber (EPDM)

Fillers to be used are:

� Wood Cellulose

� Coconut pith

MATRICES

NATURAL RUBBER

`Vulcanisate properties of natural rubber

(A) Strength

• Tensile strength: gum vulcanisates: 17-24 MPa

Black filled vulcanisates: 24-32 MPa

• Good tear strength

• Good cut-growth resistance

• Strength of natural rubber vulcanisates decreases with increase in

temperature, but better than other elastomers.

(B) Abrasion and wear

• Excellent abrasion resistance under mild abrasive conditions.

• Abrasion resistance can be improved by blending with small amount of

polybutadiene.

• Below 350C, NR shows better wear than SBR, but above 35

0C, SBR is

better.

(C) Dynamic properties

• NR has high resilience value more than 90% in well cured gum

vulcanisates.

• Fatigue life of NR is superior to that of SBR at large strains, reverse is

true for small strains.

• Good flex resistance

(D) Compression set

• Compression set and creep are poorer in NR than synthetic polyisoprene.

• Compression set is reduced by good cure.

Reasons for NR to be used for spring/belt applications

� Excellent resistance to fatigue cut growth and bearing

� High resilience

� Low creep

� Low heat build-up

� Reasonably good bonding with metals and fibres

� Wide temperature range of use

� Low cost and

� Good processability

Natural Rubber Conveyor beltings

� Top grade conveyor belting can be made from NR except those for those used in

underground mines.

� In belt manufacture, good tack and adhesion are very important.

� Good compound viscosity is also very important in the proper compaction of the

belt carcass.

� In service, NR offers reasonably good resistance to wear and chipping by such

abrasive materials as stone, coal and ores.

� For moderate heat resistance, NR is blended with SBR.

STYRENE-BUTADIENE RUBBER (SBR)

o The properties of SBR are broadly similar to that of NR.

o In comparison with NR and CR, SBR gum vulcanisates have poor mechanical

properties. The raw gum elastomer must have reinforcing fillers.

o Higher upper temperature heat ageing resistance than NR.

o Cost of raw elastomer is low and comparable with NR.

Physical Properties

Property S-SBR E-SBR

Tensile Strength( MPa) 18 19

Elongation at tear (%) 565 635

Glass Transition

Temperature (0C)

-65 -50

Polydispersity 2.1 4.5

POLYBUTADIENE RUBBER (BR)

� High resistance to wear

� Cured BR imparts excellent abrasion resistancedue to its low glass transition

temperature (Tg)

� BR is usually blended with other elastomers like natural rubber or SBR.

Vulcanisate properties

Tensile strength: 70 kg/cm2

Elongation: 540%

Modulus @ 300%:165 kg/cm2

Hardness (shore A): 59

Tear strength: 50.3 kg/cm2

ETHYLENE PROPYLENE DIENE MONOMER RUBBER (EPDM)

� The main property of EPDM is its outstanding heat, ozone and weather

resistance.

� Good resistance to polar substances and steam.

� Properly pigmented black and non-black compounds are colour stable.

� Amorphous or low crystalline grades have excellent low temperature flexibility

with glass transition points of about minus 60°C.

� Heat aging resistance up to 130°C can be obtained with properly selected

sulphur acceleration systems and heat resistance at 160°C can be obtained with

peroxide cured compounds.

� Compression set resistance is good, particularly at high temperatures, if sulphur

donor or peroxide cure systems are used.

� They can develop high tensile and tear properties, excellent abrasion resistance,

as well as improved oil swell resistance and flame retardance.

� EPM and EPDM are used in highly resistant conveyor belts.

Thermal properties of EPDM

Max. Service temperature: 1500C

Min. Service temperature: -500C

Vulcanisate Properties of EPDM Hardness, Shore A Durometer: 30 to 95

Tensile Strength: 7 to 21MPa

Elongation: 100 to 600 %

Compression Set: 20 to 60%

Useful Temperature Range: -50° to +160°C

Tear Resistance: Fair to Good

Abrasion Resistance: Good to Excellent

Resilience: Fair to Good (stable over wide temp. ranges)

Properties of different matrices can be summarised as:

FILLERS

Wood Cellulose

� The depolymerized celluloses of wood and cotton.

� It is prepared by methylation and subsequent cleavage of methylates of wood α-

celluloses.

� Cleavage of methylated wood cellulose under conditions of promoting the

complete fission of trimethylated cotton cellulose resulted in dissection of

materials into two parts.

� Another method of production of wood cellulose: acetylation – action of

Barnett’s reagents on the wood cellulose under carefully standardized

conditions results in formation of triacetates.

� Deacetylation of cellulose triacetates produces depolymersied wood cellulose.

� Methylated depolymerized cellulose is a white powder, which is soluble in

chloroform, benzene, pyridine, alcohol and glacial acetic acid and insoluble in

acetone.

Coconut Pith

� Coco peat, also known as coir pith, coir fibre pith, coir dust, or simply coir, is

made from coconut husks, which are by-products of other industries that use

coconuts.

� It consists of short fibres (<2cm) around 2% ‐ 13% of the total and cork like

particles ranging in size from granules to fine dust. Coir dust strongly absorbs

liquids and gases.

� This property is due in part to the honeycomb like structure of the

mesocarptissue which gives it a high surface area per unit volume.

� Raw coconuts are washed, heat‐treated, screened and graded before

beingprocessed into coco peat products of various granularity and denseness.

� Coir pith has a high lignin (31%) and cellulose (27%) content. Its

carbon‐nitrogen ratio is around 100:1. Because of the high lignin content left to

it, coir pith takes decades to decompose.

� Coir pith and fibre are widely used along with Rubber and Thermoset and

thermoplastics resins to make composites. Most of the works were done to

utilize the naturally occurring material in the polymer matrix for the cost

reduction and property enhancement purposes.

SELECTION OF MATRIX

Depending on the application of conveyor belt, following matrices can be used:

� Highly resistant conveyor belts: NR, EPM and EPDM

� Oil resistant conveyor belts: NR, CR, NBR and PVC-NBR

� Food conveyor belt: NR, Polyurethane, PVC-NBR

� Underground conveyor belt: NBR

PREVIOUS STUDIES ON THIS FIELD

Coconut pith was found to have a thermal conductivity equivalent to granular

cork and when bound into blocks with rubber latex was found suitable as insulating

materials for fish boxes (Pillai and Varier 1952). Coconut pith can be used in fibre

resistant building boards (Shrisalkar 1964); thermal insulating concrete (Jain and

Goerge 1970); thermal insulation boards (Rao 1971).

Viswanathan and L.Gothandapanistudied about the particle board madefrom UF

and PF resin using coir pith as the filler. Coir pith with various particle sizeswere

employed to make the composite. Better mechanical properties were obtained forPF

resins composite than the UF resin ones.

V.G.Geethammastudied on the short coconut fibre natural rubbercomposites and

the effect of fibre loading, orientation and chemical modification on theoverall

properties of the composites. They treated the fibre with alkali like 5% solutionof

sodium hydroxide and sodium carbonate for 48 hrs.and washed to remove the

excessalkali content. The fibres are then treated with natural rubber and toluene di

isocyanatesolution. The tensile properties, both in transverse and longitudinal

directions weremeasured and it was found better values in longitudinal direction. And

in the case ofalkali treated + natural rubber and toluene di isocyanate solution treated

one, gaveproperty enhancement than that of the alkali treated one. The fibre loading of

40 phrshowed better orientation of fibre in the matrix. But it failed to give a hike in

tensilestrength and tear strength values.

From another study from the same authors, dynamical mechanical behaviour

ofshort coir fibre natural rubber composites was revealed. Short fibre reinforced

rubbercomposites can be used in vibration dampers, tires etc. so the study on

dynamicmechanical properties are of great interest. The study carried out on various

treated anduntreated coir fibres in which, NaOH treatment, Resorcinol Formaldehyde

Treatment,Bleaching etc were done. In thetreatments provided, the one with bleaching

exhibitedgood dynamic mechanical properties.

ChanakanAsasutjaritstudiedon the treated coir fibre green composites.

The treatment done to coir fibres were washing in boiling water and then washing

incold water. In the first treatment coir fibres were thoroughly washed in excess of

watertill the water pH reached 7. By this the water procedure removes a part of

extraneouscomponents, such as inorganic compounds, tannins, gums, sugars and

colouring matterpresent in coir. The hot‐water procedure removes, in addition,

starches. From themorphology obtained it was found that in the surface of treated

fibres there was theformation of small pits which increased the total surface area

which eventually increasesthe interaction between binder and the filler. From the two

treatments boiling and thenwashing in water gave much better properties than the first

one.

J.Rout studied on the coir polyester amide bio composite. The polyesteramide

used was a biodegradable material thus the tag bio composite came.

Variouspretreatments were done on the coir fibres which were used for composite

preparation,namely alkali treatment, cyanoethylation, bleaching and vinyl grafting. In

alkalitreatment the coir fibres were treated with NaOH and then washed in water.

Afterdrying, AN and MMA were grafted on the surface of the coir fibre. In

cyanoethylationthe coir fibres were obtained by refluxing the alkali treated coir with

AN, acetone andpyridine (as catalyst) at 60°C for 2 h, then washing the fibres with

acetic acid andacetone, followed by washing with distilled water and finally vacuum

drying. The fibre content used was from 30 ‐60 wt%. For the untreated coir

composites better propertieswere observed for 50 wt% coir fibre incorporated

composite. Among the treated coir fibre composites, the cyanoethylated one showed

better properties than that of theuntreated and other treated fibres. In the case of alkali

treated + grafted fibres, the 7%PMMA grafted one showed better mechanical

properties. In the case of biodegradabilityof the composite, it showed same

characteristics of the biodegradable polyester amideused.

S.V.Prasadstudied on the properties of coir fibre polyester composite, inwhich

alkali treated coir fibre was used. The coir fibre were soaked in 5% NaOHsolutions for

various time spans and their impact on mechanical properties wereinvestigated. It was

found that, the time span of 72 to 76 hrs..gave much better propertiesafterwards up to

96 hrs.of time span, the properties got a decreasing trend. In the case ofchanging alkali

solution at every 24 hrs., the mechanical properties found decreasingnature after 48

hrs.of treatment. Scanning electron micrographs revealed that the cellwall thickening

and fibre shrinkage was occurring by the alkali treatment. The untreatedcoir fibres

were having a smooth surface in which alkali treatment increased surfaceroughness

which can be accounted for the better wettability and increased mechanicalproperties.

Wang Wei and Huang Gu carried out studies on coir fibre reinforced

rubbercomposite boards. The composites were prepared using compression moulding

techniquewith layer by layer construction of coir fibres. Various temperatures viz.

130°C 140°C150°C and 160°C were employed for compression moulding. From these

temperatures130°C was found to be the optimum one. As the coir fibres used were

having lengthfrom 8 mm to 337 mm, they were not homogenously mixed in the rubber

matrix, whichwas evident from the tensile property measurements. From the

percentage of fillerincorporation versus Tensile Strength studies, it was found that

60% filler loading wasthe optimum one whereas higher or lower filler content the

tensile strength reduces.

K.G.Sathynarayana studied on coir fibre‐polyester composites alongwith coir

fibre, the studies were carried out in banana fibres, cotton were also used forcomposite

preparation. The composites were prepared with an eye on end useapplications like

laminates, helmets, roofing, postbox, mirror casing, electrical equipment casing,

paperweights etc. the composites were using coir mats incorporatedin polyester resin

matrix using hand lay‐up process. These materials gave betterweatherablity properties

as that of GRP composites. And a considerable cost reductionand utilization of natural

resources were assured.

R.V.Silva and co-workers studied on Fracture toughness of natural fibres/castor

oil polyurethane composites. Sisal and coconut fibres and woven sisal matwere used

for the composite preparation. 10% NaOH solution is used for the alkalitreatment and

finally repeated washing in water was equipped. But the properties werelesser for

coconut fibre composites than that of sisal fibre ones. But as compared to

thepolyurethane matrix, no property enhancement was observed. In the treated fibre

section the coconut fibres showed better properties.

J. Rout and co-workers studied on the influence of the fibre treatment on

theproperties of natural fibre polyester composites. Alkali treatment,

cyanoethylation,bleaching and vinyl grafting were the different surface treatments

done on coconut fibre.From the result obtained it was found that the surface treatments

gave much betteraddition between polymer and filler thus improving mechanical

properties in aconsiderable manner. Among the treatments alkali treatment gave better

results ascompared to the other three.

From a study it was found that in the case of natural fibre, coated with lignin

andethylene diamine (EDA) in order to reduce the higher resin consumption and to

reducethe moisture absorption. Just half of the resin amount was utilized for the

treated fibre ascompared to the untreated one. Even though the tensile and modulus

values wereaffected little bit by the treatment and gave less value, considering the

economic view,the resin consumption and moisture absorption got reduced.

FORMULATIONS FOR CONVEYOR BELT IN WHICH

REINFORCINGSILICA IS BEEN USED:

Black conveyor belt cover (NR/BR)

Formula:

SMR CV60- 80

BR 1208- 20

Vanox ZMTI- 1.1

Carbon black N330 10

Hi-Sil- 40

Vanplast- 2

Sundex790- 2.5

Santoflex 6PPD- 2.5

ZnO- 3

RM Sulphur- 2.5

Santocure MBS- 1.4

Perkacit TMTD- 0.2

This compound was mixed in a 2-wing lab internal mixer

ML (1+4) 1000C MU- 15.8

Specific gravity- 1.118

Tensile strength- 23.3MPa

Elongation- 766%

Modulus @200% 2MPa

Modulus @ 300% 4.3MPa

Hardness (Shore A) 59

Tear resistance 85.3N/mm

Abrasion Resistance DIN loss 137mm3

D-Flex Crack Growth, 5 mm

100K cycles,

Black Conveyor Belt Cover (SBR)

Formula:

Copo SBR1500- 100

Flectol TMQ- 2

Carbon Black N550- 15

HiSil- 50

Stearic Acid- 2

Cumar MH- 10

Calsol510 (NAPH Oil)- 10

Sunproof Reg. Wax- 2

Santoflex 6PPD- 2.5

ZnO - 4

RM Sulphur - 0.5

Santogard PVI- 0.2

Santocure TBBS- 3

Perkacit TMTD - 1

This compound was mixed in a 2-wing lab internal mixer.

ML (1+4) 1000C 30+

Specific gravity 1.176

De Mattia Flex, 1000 cycles 8.0mm

Tear Resistance 43.9N/mm

Abrasion Resistance- 147mm3

CONVEYOR BELT COVER

NATURAL RUBBER 80

POLYBUTADIENE RUBBER 20

ZINC OXIDE 5

STEARIC ACID 2

ISAF BLACK 50

AROMATIC OIL 10

ANTIOXIDANT 1.5

SULPHUR 2.5

MBTS 1.0

TMTD 0.2

FORMULATION-2

NR 100

PEPTISER 0.2

ZnO 5

STEARIC ACID 2

ANTIOXIDANT 1

ANTIOZONANT 1

HAF BLACK 45

CI RESIN 2

AROMATIC OIL 6

PARAFFIN WAX 0.5

CBS 0.8

TMT 0.05

PVI 0.1

SULPHUR 2.3

FORMULATION-3

SBR 1500 100

CARBON BLACK N375 40

ZINC OXIDE 5

STEARIC ACID 1

AROMATIC OIL 5

CBS 1

SULPHUR 2.5

ANTIOXIDANT 1.5

ANTIOZANANT 1.5

FORMULATION-4

EPDM 100

YELLOW IRON OXIDE 6

POLYETHYLENE GLYCOL 3350 2

SILICA 50

POLYETHYLENE 3

NAPHTHENIC OIL 20

HYDROCARBON RESIN 2

STEARIC ACID 2

ZINC OXIDE 5

SULPHUR 0.5

TETD 3

ZDMC 3

DTDM 1

MANUFACTURING

1. DRYING OF FABRIC(FOR COTTON FABRIC)

2. RFL DIPPING(FOR SYNTHETIC FABRIC)

3. FRICTIONING AND TOPPING

4. BELT BUILDING

5. PREHEATING(BY MICROWAVE TECHNIQUE)

6. VULCANISATION & MOULDING

a) PRESS CURE

b) CONTINUOUS VULCANISATION

DRYING OF FABRIC

Drying of fabrics is essential to avoid blowing of the laminate occurring during

the vulcanising operation. The fabric is dried by passage over a multiple stem-heated

drum drier or hot plate at a speed of 15 m per min at a surface temperature of 115oC.

A minimum moisture level of 1% for cotton containing fabrics is required.

RFL DIPPING

Synthetic filament fabrics, which have been impregnated with adhesive, eg:

RFL type, and heat treated, do not usually require pre-drying before skim coating.

FRICTIONING AND TOPPING

To ensure good fractioning, a hot fabric is essential. Frictioning on each side is carried

out on a three/four roll calendar. The lighter weight fabrics are friction coated, and

heavier fabrics are also topped or skim coated to give additional rubber between plies

and between the outer plies on covers. It is important that a uniform layer of rubber is

applied during the topping operation.

BELT BUILDING

Usually full width fabrics to the optimum width of the calendar are used for the

calendaring operation, in which both sides of fabric are coated simultaneously. The

fabrics are then cut accurately to the width required on a cam-cutting machine which

as multiple circular cutting knives. The cut widths are adhered together by passing

them through a doubling roll arrangement until the correct number of plies are

obtained.

The covers are calendared directly onto the belt carcass using a three/four roll

calendar; or calendared sheeting is applied on the building table. In the latter case, the

completely built belt is then consolidated and passed through pricking rollers to

remove any trapped air.

PREHEATING

This can sometimes result in substantial reduction of vulcanising time, because

materials, such as rubber, are difficult to heat uniformly without degrading their

structure. Rubber has high dielectric characteristics and thus can absorb energy of very

high frequency, generating heat uniformly within the material structure. Micro wave

heating is basically similar to dielectric heating but, with the frequency increased from

100 MHz to 2000 MHz.

Microwave heating system consists of a power supply to raise the mains voltage to

approximately 7Kv, which is then fed to a magnetron oscillator. The magnetron

oscillator contains within its vacuum envelope a tuned circuit and delivers the energy

via an aerial and waveguide to the applicator.

A typical applicator is a metal chamber , so designed that , for frequency generated,

the chamber becomes a resonant cavity. The laminate is placed inside the cavity: no

direct contact with metal is required as in dielectric heating, and the material can be

heated irrespective of the product shape. Even distribution of energy is obtained

through cavity design and the provision of a rotary deflector system mounted at each

entry point, and perhaps inside the pre-heating chamber.

VULCANISATION & MOULDING

PRESS CURE

Various types of large flat multi-ram presses are used, of frame or column

construction, both single and double daylight.

The raw belt is unreeled from a braked ‘let-off’ station to the press, and a section is

vulcanised. The presses have cool areas at the ends t prevent over cure between

successive sections of the belt. Each press is equipped with stretching gear, usually

consisting of flat hydraulically operated clamps, the belts being stretched a given

amount prior to closing the press. This stretching is essential to prevent excessive

lengthening of belt occurring in service. A moulding frame is made from flat 50-75

mm wider metal irons placed along each side of the belt. Lateral pressure to form the

belt edges is usually applied by hydraulically operated cams which move the metal

irons in a fixed amount after the press has been closed on low pressure. The thickness

of the metal irons is selected to give 10-12 % compression on the raw belt thickness .

The length of cure depends upon the thickness of the belt, and an average cure time

would be 17 min at 1450C. On completion of the cure of a section , the next length is

indexed into the press, the small semi-cured end section being brought to the exit

end of the press and its cure completed on the next operation.

CONTINUOUS VULCANISATION

The belt is passed between a rotating steel drum and an endless high-tensile-steel

band, pressure being applied by tensioning the latter hydraulically; heat is applied to

both sides of the product, from the internally heated drum and also through the steel

band by contact with steam-heated shoes. Typical dimensions of one such machine are

as follows: width of steel band, 2m; width of main drum,2.3m; approximate maximum

product width,1.9m; drum diameter,1.5m; maximum pressure, 4.8kgf/cm2. The

maximum product thickness is 32 mm, but the maximum product width varies with the

application. The curing speeds are variable between 65m/h and 40m/h, giving cure

times of from 3.5 min to 53 min, which adequately covers the range normally required

for rubber belting. The belt being fed through the vulcaniser is subjected to an initial

tension accurately set and maintained, and also to a predetermined stretch.

TESTING

1. Raw material testing

2. In process testing

3. Functional testing

4. Final product testing

Raw material testing

1. Plasticity

2. Mooney viscosity

3. Tack

4. Plasticity retention index

5. Die swell and stress relaxation

6. Dynamic stress strain properties

In process testing

1. Tests on rubber compound

2. Tests on rubber vulcanisate

Tests on rubber compound

I. Rheometeric test

II. Mooney viscosity test

III. Mooney scroch test

Tests on rubber vulcanisate

I. Hardness

II. Stress strain-tensile strength, elongation at break, modulus

III. Creep/stress relaxation

IV. Load deflection

V. Set properties

VI. Abrasion

VII. Flexing test

VIII. Heat build up

IX. Ageing tests

X. Pressure test

XI. Electrical testing

Functional testing

1. Flammability tests

2. Propane burner test

3. Large scale fire test

4. Drum friction test

5. Surface resistance test

6. Limiting oxygen index test

Final product testing

1. Flexing test

2. Ageing test

3. Hardness

4. Stress-strain test –tensile strength, elongation at break, modulus

5. Creep /stress relaxation

6. Load deflection

7. Set properties

8. Abrasion

Dynamic mechanical analysis

Dynamic mechanical analysis (abbreviated DMA, also known as dynamic mechanical

spectroscopy) is a technique used to study and characterize materials. It is most useful

for studying the viscoelastic

the strain in the material is measured, allowing one to determine the

The temperature of the sample or the frequency of the stress are often varied, leading

to variations in the complex modulus; this approach can be used to locate the

transition temperature of the material, as well as to identify transitions corresponding

to other molecular motions

Types of analyzers

There are two main types of DMA anal

analyzers and free resonance analyzers. Free resonance analyzers measure the free

oscillations of damping of the sample being tested by suspending and swinging the

sample. A restriction to free resonance analyzers is

rectangular shaped samples, but samples that can be woven/braided are also

applicable. Forced resonance analyzers are the more common type of analyzers

available in instrumentation today. These types of analyzers force the samp

oscillate at a certain frequency and are reliable for performing a temperature sweep.

Analyzers are made for both stress (force) and strain (displacement) control. In strain

control, the probe is displaced and the resulting stress of the sample is measured by

implementing a force balance transducer, which utilizes different shafts. The

advantages of strain control include a better short time response for materials of low

viscosity and experiments of stress relaxation are done with relative ease. In stress

control, a set force is applied to the same and several other experimental conditions

(temperature, frequency, or time) can be varied. Stress control is typically less

expensive than strain control because only one shaft is needed, but this also makes it

harder to use. Some advantages of stress control include the fact that the structure of

the sample is less likely to be destroyed and longer relaxation times/ longer creep

studies can be done with much more ease. Characterizing low viscous materials come

at a disadvantage of short time responses that are limited

control analyzers give about the same results as long as characterization is within the

linear region of the polymer in question. However, stress control lends a more realistic

response because polymers have a tendency to resist a load.

viscoelastic behavior of polymers. A sinusoidal

in the material is measured, allowing one to determine the

of the sample or the frequency of the stress are often varied, leading

to variations in the complex modulus; this approach can be used to locate the

of the material, as well as to identify transitions corresponding

to other molecular motions.

There are two main types of DMA analyzers used currently: forced resonance



sample. A restriction to free resonance analyzers is that it is limited to rod or



available in instrumentation today. These types of analyzers force the samp





ntages of strain control include a better short time response for materials of low



temperature, frequency, or time) can be varied. Stress control is typically less





at a disadvantage of short time responses that are limited by inertia



e polymers have a tendency to resist a load.

sinusoidal stress is applied and

in the material is measured, allowing one to determine the complex modulus.

of the sample or the frequency of the stress are often varied, leading

to variations in the complex modulus; this approach can be used to locate the glass

of the material, as well as to identify transitions corresponding

yzers used currently: forced resonance



that it is limited to rod or



available in instrumentation today. These types of analyzers force the sample to





ntages of strain control include a better short time response for materials of low



temperature, frequency, or time) can be varied. Stress control is typically less





inertia. Stress and strain



Stress and strain can be applied via torsional or axial analyzers. Torsional analyzers

are mainly used for liquids or melts but can also be implemented for some solid

samples since the force is applied in a twisting motion. The instrument can do creep-

recovery, stress-relaxation, and stress-strain experiments. Axial analyzers are used for

solid or semisolid materials. It can do flexure, tensile, and compression testing (even

shear and liquid specimens if desired). These analyzers can test higher modulus

materials than torsional analyzers. The instrument can do thermomechanical

analysis(TMA) studies in addition to the experiments that torsional analyzers can do.

Figure shows the general difference between the two applications of stress and strain.

Changing sample geometry and fixtures can make stress and strain analyzers virtually

indifferent of one another except at the extreme ends of sample phases, i.e. really fluid

or rigid materials. Common geometries and fixtures for axial analyzers include three-

point and four-point bending, dual and single cantilever, parallel plate and variants,

bulk, extension/tensile, and shear plates and sandwiches. Geometries and fixtures for

torsional analyzers consist of parallel plates, cone-and-plate, couette, and torsional

beam and braid. In order to utilize DMA to characterize materials, the fact that small

dimensional changes can also lead to large inaccuracies in certain tests needs to be

addressed. Inertia and shear heating can affect the results of either forced or free

resonance analyzers, especially in fluid samples.

NVH analysis

NVH is an industry term that stands for noise, vibration, and harshness.

It is a search for the source of a noise, shake, or vibration, and it refers to the entire

range of vibration perception, from hearing to feeling.

Noise is unwanted sound; vibration is the oscillation that is typically felt rather than

heard. Harshness is generally used to describe the severity and discomfort associated

with unwanted sound and/or vibration, especially from short duration events.

NVH is also called sound quality analysis, which involves metrics such as loudness,

sharpness, sound exposure level, and others.

NVH Test Equipment Include

Analyzers, shakers and controllers, accelerometers, noise dosimeters, octave band

filters, transducers for vibration and acoustics, dynamometers, sound level meters,

microphones, and analysis software.

rubber compound preparation for conveyor belt

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