Lab Tensile test

TITLE

Tensile Tensile testing of materials

OBJECTIVE





To analyze and evaluate the tensile properties of materials such as values of Tensile strength, Yield Yield strength, Percentage elongation, fracture strain and Young's Young's Modulus of of the selected metal (steel and aluminum ) when subected to unia!ial tensile loading" To e!plain deformation and fracture characteristics of different materials such as aluminum, steel or any other metal"

INTRODUCTION

Tensile testing is one of the most fundamental tests for engineering, and provides valuable information about a material such as ho w they will behave under load and its associated properties" These properties can be used for design and analysis of engineering structures, structures, and for developing new materials that better suit a specified use" Most of the time this test is used to evaluate material parameters such as ultimate strength, yield strength, percentage elongation, percentage area of reduction and Young's Young's modulus" #n this lab e!periment the tensile testing is carried out b y applying longitudinal or a!ial load at a specific e!tension rate to a standard tensile specimen with $nown dimensions (gauge length and cross sectional area perpendicular to the load direction) till failure" The applied tensile load and e!tension are recorded during the test for the calculation of stress and strain" The e%uipment used for tensile testing ranges from simple devices to complicated controlled systems" #n this lab e!periment a device called a Tensometer Tensometer is used to measure, calculate and draw the &tress &train graph" In order to use this device, material to be tested must be cut to a specific shape so as to fit the grips, most usually in the form o f a dogbone shape when flat sheet is being tested"

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THEORY

Stress   /

Strain  =  /0

* +pplied load

 -longation of the specimen after the test

+. #nitial cross sectional area

. #nitial gauge length

Young/s modulus

E   0 

Young/s Young/s Modulus (-) or the modulus of elasticity is a measure of a materials stiffness" The higher the Young/s Young/s modulus value the stiffer the material" Young/s Young/s modulus can be calculated from tensile test stress (  )0strain )0strain ( ) graphs1derived from load0e!tension graphs" The slope of the graph is used to calculate - when the material is obeying obe ying 2oo$e/s law"

Yield strength σy  P y0 A0 #t is often difficult to precisely define yielding due to the wide variety of stress1strain curves e!hibited by real materials" 2owever b y considering the stressstrain curve beyond the elastic portion, if the tensile loading continues, yielding occurs at the beginning of plastic deformation" The yield stress, 3y, 3y, can be obtained by dividing the load at yielding (Py) by the original crosssectional area of the specimen (+o)

4ltimate Tensile &trength

= P max σ TS TS = max / A0

4ltimate tensile strength (4T&), often shortened to tensile strength (T&) is the ma!imum stress that a material can withstand while being stretched or pulled before failing or brea$ing" Tensile Tensile strength is not the same as compressive strength strength and the values can be %uite different" #f the load is continuously applied, the stressstrain curve will reach the ma!imum point, which is the ultimate tensile strength (4T&, 3T&)" +t this point, the specimen can withstand the highest stress before nec$ing ta$es place" This can be observed by a local reduction in the cross sectional area of the specimen generally observed in the center of the gauge length"





MATERIALS AND APPARATUS APPARATUS



Material  &pecimen 1 &teel



-%uipment  Tensometer  Percentage -longation gauge  Percentage +rea gauge  Micrometer A partial segment of the Tensometer Tensometer

*igure of Micrometer while measuring the length of the steel specimen after the e! eriment ent

Figure of Percentage Elongation gauge while measuring the percentage change of the steel specimen after the





PROCEDURE

+ sample of medium carbon steel was tested by using a manual TensileTesting TensileTesting Machine" 2orizontally fi!ed sample is subected to a unia!ial tensile force with a testing speed of about 6.mm0min" The force acting on the sample and the e!tension will be measured and recorded in the machine" 7asically meaning, placing the test specimen in the testing machine and slowly e!tending it until it fractures and during this process, the e longation of the gauge section is recorded against the applied force"

Metallic specimen used for the tensile test + ength of reduced section 8 8iameter 9 9age length : :adius of fillet

*irst choosing and measured the gauge length, width and the cross sectional area of it by using the micrometer, elongation gauge and area gauge" Then before loading the specimen to the Tensometer Tensometer (tensile test machine) the computer system connected to the machine was setup by inputting the necessary n ecessary information of gauge length and width of the specimen" The computer system was then prepared to record data and output necessary graphs" &pecimen was loaded into the Tensometer and the paddle was rotated in a constant speed until the specimen was fractured" The final graph was finally given as an output from the computer"





OBSERVATIONS o

;bservations 5e observed that when the metal was subected to an e!ternal tensile loading, the nec$ing point was unseen until u ntil it was about to brea$" There for the elastic deformation was invisible to the eye while doing the e!periment" 7ut after the
*igure= The metal specimen after the nec$ing occurred

o o

;bservation sheet 9raph (&tress vs" &train)

+ttached ne!t page

}





CALCULATIONS

#nitial diameter of the mild metal specimen 

>?"> mm

#nitial length of the mild metal specimen 

@"A mm

#nitial ar are of of th the mi mild me metal sp specimen 

B (d (d06)6

>A"C.@D mm6







RESULTS

+fter e!periment measurements=

-longation Percentage 

D.E

Percentage of reduction area 

6.E

Percentage of of reduction ar area  at the nec$ing point

? .E

Percentage of -longation 

D >E

*inal length of specimen 

6>"> mm

4ltimate tensile strength 

AFD"A <0mm6

Stress vs Strain curve of mild Steel

Stress vs Strain curve of Aluminum





CONCLUTION

This tensile test e!periment is important for determining a material/s properties, limits and its potential application in a wide range of industries" #f a material is is to be used in an engineering structure it will be subected to various loads and it is important to $now that the material is strong enough to withstand the loads that it will e!perience during its service life" #n summary, tensile properties should be considered as important design parameters for the selection of engineering materials for their desired application" -ngineers have played a significant role in that they should be able to analyze and understand material behavior and properties through these mechanical testing parameters"

REFERENCE

Tensile Tensile testing httpsG00en"wi$ipedia"org0wi httpsG00en"wi$ipedia"org0wi$i0Te $i0TensileHtesting nsileHtesting &tress and its effect on Materials httpG00www" httpG00www"scribd"com0doc066C>CCAI0Te scribd"com0doc066C>CCAI0TensileTe nsileTestJscribd stJscribd 8avis, Koseph :" (6..@)" (6..@ )" Tensile Tensile testing ( 6nd -d")" +&M #nternational +shby, M" (6..?)"-ngineering Materials >G +n #ntroduction to Properties, +pplications and 8esign" Drd ed" 7utterworth2einemann

Lab Tensile test

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