4 Characterization of Metals
4.6 NOTES ABOUT TECHNOLOGICAL CHARACTERIZATION TESTS
It.has.already.been.stated.that.the.technological.properties.of.materials.relate.to.their.aptitude.to.
react.to.external.forces..The.main.technological.tests.for.metallic.materials.will.be.examined..Some.
of.these.tests.are.standardized,.while.others,.though.not.officially.recognized,.are.quite.widespread.
anyway.
10 2
10
75
R1
22 28 Mazza
FIGURE 4.21 Specimen.for.Izod.test.(Standardized.in.England).
Notch:
U notch:
2 10 2
10 55 5 5
Keyhole notch Area 0.5 × 1 = 0.5cm2
r = 1
FIGURE 4.20 Standard.bars.for.steel.
4.6.1 Drawing tests
These. tests. aim. to. assess. the. aptitude. of. sheet. metal. to. be. turned. into. a. hollow. body. without.
breaking..Obviously,.this.aptitude.varies.according.to.sheet.type.
Italian.norms.provide.for.three.different.types.of.drawing.tests:
•. Erichsen.drawing.test,.symbol.IE.(UNI.3037):
•. Erichsen.drawing.test.modified,.featuring.the.symbol.IE.(UNI.4693)
•. Socket.drawing,.featuring.the.symbol.IB.(UNI.6124) 4.6.2 erichsen Drawing test
The.test.performing.device.is.shown.in.Figure.4.24..It.is.made.up.of.a.spherical.20.mm.diameter.
punch,.a.template.on.which.the.sheet.is.laid,.and.a.blank.holder.A.that.presses.against.the.bar.to.
prevent.it.from.creasing.during.the.test.
The.metal.sheets.are.0.2–2.mm.thick.and.big.enough.to.accommodate.a.minimum.70.mm.circle.
15 60º
45º 40
55 1.5 3
210 10
Spina Ø = 5 RO ∞
FIGURE 4.22 Specimen.for.Schnad.test.
28 28
105 2
10 14MA
Ø8
FIGURE 4.23 Pendulum.Charpy.in.Schnad.test.
The.sheet.is.placed.between.the.template.and.blank.holder;.first.the.punch.is.brought.into.slight.
contact.with.the.sheet,.then,.either.by.a.hydraulic.or.manual.system,.the.punch.is.pushed.forward.
at.a.0.2–0.4.mm/min.speed,.until.it.generates.a.fracture.in.the.sheet.that.has.turned.into.a.spherical.
surface..At.the.end.of.the.test,.the.momentum.of.the.punch.expressed.in.millimeters.is.taken.as.the.
drawing.index.and.is.represented.by.IE.
4.6.3 erichsen Drawing test MoDifieD (uni 4693)
This.test.is.performed.much.like.the.previous.one.with.two.exceptions:.the.punch.is.pushed.forward.
at.a.velocity.of.5–20.mm/min and.sheet.thicknesses.are.0.5–2.mm.
4.6.4 socKet Drawing test (uni 6124)
The.test.device.is.identical.to.the.one.for.the.ordinary.Erichsen.test,.only.the.punch.is.different..
No.longer.spherical.but.cylindrical.(Figure.4.25),.tests.are.carried.out.on.sheet.disks.of.increasing.
diameter:.55,.56,.58,.60,.62,.64,.66,.68,.and.70.mm..The.procedure.is.the.same,.only.the.punch.
speed.varies.from.60.to.120.mm/min,.until.the.test.bar.breaks.
4.6.5 PoMP Drawing test
Here,.the.test.bars.are.sheet.metal.disks.with.a.central.hole..The.punch.is.cylindrical.with.a.central.
pin.that.enters.the.sheet.hole.for.centering.(Figure.4.26).
The.testing.stops.when.the.test.bar.hole,.now.enlarged,.shows.the.earliest.edge.cracks.in.a.radial.
direction..The.material.quality.index.is.given.by
. Ac d d= ud− 0
0 100,
du.being.the.test.bar.hole.diameter.at.the.end.of.the.test,.d0.the.test.bar.hole.at.the.beginning.
90 min 55:01 27:005
R 0.75:0.01 R 0.75:0.05
P
a ≤ 2
B
33:0.1 55:0.1 A
R 0.75:0.01 Ø = 20:0.0
5
3:0.1 20 min20 min
FIGURE 4.24 Erichsen.drawing.test.
4.6.6 benDing test
This.test.is.compulsory.for.the.steel.bars.in.reinforced.concrete,.for.the.sheet.metal.in.boilers,.and.
so.on..The.two.following.bending.tests.are.possible.
4.6.7 teMPlate benDing
The.test.is.shown.in.Figure.4.27..The.test.bar.lies.on.a.template.and.is.then.bent.to.a.V.by.the.appro-priate.punch..The.template.V.has.an.angle.of.60°–70°.and.an.opening.of.at.least.125.mm.
D d
FIGURE 4.25 Socket.drawing.test.
D
Punch
Guide pin
Sheet d0
S
dM
FIGURE 4.26 Pomp.drawing.test.
4.6.8 ManDrel bearing benDing
The.test.consists.of.bending.a.full-section.prismatic.or.cylindrical.bar.lying.on.two.roller.bearings.
by.using.a.mandrel.(Figure.4.28).
The.mandrel.diameter.as.well.as.that.of.the.two.roller.bearings.must.be.indicated.in.the.test.
specification..The.distance.between.the.two.bearings.must.be:.D.+.3a,.D.being.the.mandrel.diam-eter.and.a.is.the.bar.thickness.
Pressure.is.applied.by.the.mandrel.until.one.of.the.two.bar.edges.forms.an.angle.a.with.the.exten-sion.of.the.other.(Figure.4.29).
After.bending,.if.the.edges.are.parallel.α.=.180°,.two.cases.are.possible:
•. Bending.with.a.certain.aperture.D0 (Figure.4.30);
•. Block.bending,.the.edges.brought.into.contact.(Figure.4.31).
Test.results.are.given.after.examining.the.status.of.the.outside.of.the.bent.part..They.are.positive.
if.no.cracking.occurs.
4.6.9 Percentage Elongation anD the tetMajer coefficient
We.define.the.bending.test.elongation.as.the.percentage.given.by
.
L LuL
− 0
0 100,
Lu.being.the.width.of.the.arc.AOB.after.the.test,.whereas.L0.is.the.same.section.before.the.test.
(Figure.4.32).
Punch Plate
60º 70º
Matrice
>125 mm
FIGURE 4.27 Template.bending.test.
The.Tetmajer.number.is.shown.with.the.symbol.Cp; it.can.be.demonstrated.that
. Cp L L= L− = n
+
u 0
0 100 1001,
where.n.=.D/a,.D.being.the.mandrel.diameter.by.which.the.bar.is.bent.and.a the.test.bar.thickness..
Notice.that.the.expression.above.is.missing.the.angle.α,.which.does.not.affect.the.test.at.all,.whereas.
D
h
R R
FIGURE 4.28 Mandrel.bearing.test.(at.beginning).
D
60º
L
R R
α
FIGURE 4.29 Mandrel.bearing.test.(at.end).
the.bar.curvature.radius.R.is.essential,.since.bar.cracking.depends.on.it..The.expression.p.=.100./.(n.+.1).
can.indeed.be.written.as
. Cp a
= 50R .
4.6.10 forging tests
Forging.is.when.metals.undergo.deformation.through.hot.work.procedures.and.when.several.differ-ent.tests.are.carried.out..The.most.important.are.described.below.
4.6.11 stretch tests
This.test.measures.the.deformability.of.a.metallic.material..It.is.carried.out.on.a.prismatic.bar.that.
for.steel.has.the.following.dimensions.(Figure.4.33):
. L0=( .1 5 2− )b b0 †0=3a0.
4.6.12 heaDing test
This.is.carried.out.on.metallic.materials.that.become.rivets..It.is.performed.on.a.cylindrical.test.bar.
with.diameter.d0.and.height.h0..The.results.are.given.by.the.heading.number:
. A h h= 0h− u100,
where.h0.=.initial.bar.height,.hu.=.final.bar.height.(Figure.4.34).
D0 aa
FIGURE 4.30 Mandrel.bearing.at.D0.aperture.
FIGURE 4.31 Mandrel.bearing.at.contact.