8/13/2019 Expt 08 Plastic Anisotropy

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EXPERIMENT NO-8:

To study the anisotropy ratio of aluminium sheet by 2! "old rolled#

Objective:To find the plastic anisotropy ratio for the Aluminum tensile samples.Requirements:3 Aluminum sample (00, 450and 900from rolling direction), Scre gauge, !ernier calliper

Principle: "n our daily#s life e use many metallic structures that loo$ to %e in the form of cup or tu%e,$e all types of &essels, utensils, automo%ile panels etc. They all formed %y sheet metal deep draingperation. 'eep draing is done %y placing a %lan$ of appropriate sie o&er a shaped die and pressing the

metal the metal into the die ith a punch (ig **.*). "n the deep draing of a cup the metal is su%+ected tohree different types of deformations. ig **. represents the deformation and stress de&eloped in a pie-haped segment of a circular %lan$ during deep draing .The metal at the center of the %lan$ under theead of the punch is rapped around the profile of the punch and in doing so all thic$ness is reducing.

ig **.* 'eep 'raing of a cylindrical cup a) %efore draing %) after draing ig **. Stress and deformation in

a section from a dran cup

'raing operation classified into draing ith apprecia%le decrease in all thic$ness called ironing andraing ith little change in all thic$ness, called sinking. The ironing process is %asically the same asu%e draing ith a mo&ing mandrel. The predominant stress in ironing is the radial compressi&e stresse&eloped %y the pressure of the punch and the die. 'raing ithout reduction in all thic$ness isasically the same as tu%e sin$ing or tu%e draing ithout a mandrel. The predominant stresses are anial tensile stress from the action of the punch and a circumferential compression from the draing in of

he metal.

To impro&e draa%ility, the potential failure site near the %ottom of the cup all must %e strengthenedelati&e to the metal deforming %y radial draing near the top of the cup all. /oughening the punch or

ithholding lu%rication to the punch may also help in this regard. "t ould also %e possi%le to ea$en the

metal in the flange relati&e to the failure site %y selecti&ely heating the metal in the flange area. oe&er,y far the greatest impro&ement in draa%ility comes a%out %y the control of crystallographic texture in theheet that is to %e dran. The correct teture gi&es the proper orientation of slip systems so that thetrength in the thic$ness direction is greater than that in the plane of the sheet.

The resistance to through thic$ness thinning as measured %y R, the plastic strain ratio of idth tohic$ness in a sheet. R measures the normal anisotropy.A large &alue of R denotes high resistance tohinning in the thic$ness direction (direction normal to the plane of the sheet).

R1 ln (wo/w)2ln (h0/h)

here w0 and w are the initial and final idth and h0 and h are the initial and final thic$ness. Sincehic$ness measurements are difficult to ma$e ith the precision on the thin sheets, the euation can %e

eritten using the constancy-of-&olume relationships./12h1 2-(l) 1 ln (wo/w)2-ln (w0L0/wL) 1 ln (wo/w)2ln (wL/w0L0)

here L0and Lare the initial and final gauge length

8/13/2019 Expt 08 Plastic Anisotropy

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Since most rolled sheets sho a &ariation of elastic and plastic properties ith orientation in the plane ofhe sheet, it is usual to allo for this planar anisotropy %y R a&eraged o&er measurements ta$en atifferent angles to the rolling direction of the sheet.

R 1 (R0R45R90)24

here R0, R45and R90are the normal anisotropy &alue for the samples in 00, 450and 900from the rolling

rection

ig **.3 Aluminum Sample

Equipment:"nstron machine that as used for 6periment no. 3 (Tensile testing of Teflon sample)

Experimental Procedure:

. 7ar$ all samples for the reduced gauge length (uniform idth)

. 7easure all the dimensions (8auge length and idth %y !ernier caliper and thic$ness %y Scre gauge)

f the gi&en lead sample

. oad the *stsample up to mar$ in the machine

. :se crosshead speed as mm2min

. Start tension test till the :TS (ultimate tensile strength) point

. :nload the sample and measure its dimension again

. /epeat 4-; for other samples

Report:

. rite dimensions reading for all three samples %efore and after tensile test

. =alculate 6ngineering >ield strength and :ltimate tensile strength of all three samples

. =alculate R of all three samples and =alculate R

. ?lot 6ngineering stress &s. engineering strain cur&e of all three samples in the same graph

Questions:

. hat are the typical R &alues of common engineering 7aterials and hich products can %emanufactured %y them using sheet metal draing operation@

. hat is more important, Ror R and hy@

. hat are the precautions to %e ta$en during plastic anisotropy testing@

. hat is effect of 8rain sie on the R &alue@

idth ()

8auge ength ()

Thic$ness (h)