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Experiment No.: 07 Date: / /200

IMPACT TEST

AIM: Todetermine the toughness of thematerial by impact test (Charpy & Izod test).

APPARATUS:

Impact testing machine Model FIT-300-N, notched specimen.

THEORY:

Under certain situations, a ductile material fails in a brittle manner in theservice and such a failure is characterized by low absorption of energy. Thefactors which contribute to the brittle type of failure are:

(i) Triaxial state of stress, (ii) Low temperature and (iii) High strain rate orrapid rate of loading. The brittle failure may result due to the presence of

anyone or the combination of these factors in sufficient magnitude. A triaxialstate of stress which exists at the tip of defects in the component and lowservice temperatures are mostly responsible for the brittle failures. Theseeffects become more important at high rates of loading. Therefore, thesusceptibility of materials for brittle failures under the existence of thesefactors is determined by such tests which apply fast loads like Impact tests.

A triaxial state of stress is developed at the root of a notch and hencenotched specimens are used in these tests. The tendency of brittle failuresin the presence of notches is called, Notch sensitivity and hence thenotched impact tests measure the notch sensitivity of the material.Variation of this condition is achieved. by using different types of notches

or the same notch such as V and varying the angle of V.

The effect due to temperature is assessed by testing the specimensat low temperatures. The temperature at which a ductile material fails in abrittle manner is called Ductile Brittle transition temperature.

Charpy impact test is widely used in the United States and Izod impacttest in Great Britain for this purpose. Procedures for the Charpy and Izodtests as applied to metals have been standardized (ASTM E 23 or IS 1499and 1598) and are as below:

In each case a certain mass is released from some distance above the

impact point which strikes the specimen. The kinetic energy of the tup orhead at the moment of impact is mv2/2 which is equal to the potentialenergy of the tup before its release (mgh)

Where, m = Mass of tup,v = Tangential velocity oftup at the point ofimpact;g = Gravitational acceleration (= 9.806 m/s2)

and h = Height ofdrop.

METALLURGY G. S.PATIL

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From this it will be seen that the drop height determines the velocity andthe drop

height and mass jointly determine the energy. For different tests andmaterials, differentiate levels ofkinetic energy and tangential velocity at thepoint ofimpact are required and hence this can be achieved by changing themass ofthe head and the position ofthe pendulum arm before release.

The standard specimen for the charpy test is square prism 10 by 10 by 55mm,V-notched in centre as shown in Fig. In many specifications a key hole notchor aU-notch is used, as shown in Fig. (b) & (c). The specimen is arranged as a

simply supported beam with a span of 40 mm and the notch is on tension

side i.e. on the opposite side of the striking edge, as shown in Fig. 3.47 (a).For the Izod test, square prism specimens 10 by 10 by 75 mm, V-notched as

illustrated in Fig. are clamped to act as vertical cantilever with the notch onthe tension side i.e. on the same side of striking edge as shown is Fig. (b).Round samples can also be used in the Izod test. :

Effect of variables:

(i) Velocity(ii) Specimen

(iii) Notch effect

(iv) Temperature

PROCEDURE:

1. Standard test piece provided with a notch is placed on an anvil for firm

support.

2. A pendulum hammer is raised to a std height (h) depending upon the

type of specimen used.

3. Change the mass of head for different test and for all different test

levels.

4. Pointer is provided with semicircular test dial which is set initially.

5. Release the pendulum so that it is supported by hand breaker.

6. Note down the reading on semicircular dial as energy needed to break

speed.

SPECIFICATIONS:

A machine has a head (with arm) weighing 20.932 kg and length of

arm 0.825 metre. On this machine both the Charpy and Izod tests can be


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carried out by changing the heads and specimen fixing arrangement. For

Charpy test, pendulum is released from an angle of1400 C (the drop height

corresponds to 1.457 m)

OBSERVATION TABLE:

Sr.No.

Impact Test Material Impact Energy(Toughness)

01 Charpy Test

Brass

Mild Steel

02 Izod TestMild Steel

Aluminum

CALCULATIONS:

1) For Charpy Test-

Hammer Weight = _________ kg

Impact Height = _________ m

Impact Energy = mgh=

= _________ J

Impact Velocity = 2gh= ________ m/s

2) For Izod Test-

Hammer Weight = _________ kg

Impact Height = _________ m

Impact Energy = mgh


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== _________ J

Impact Velocity = 2gh= ________ m/s

CONCLUSIONS:

1) In Charpy impact test, Impact energy (Toughness)values are,

Mild Steel =

Brass =

2) In Izod impact test, Impact energy (Toughness)values are,

Mild Steel =

Aluminum =


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Experiment No.: 04 Date: / /200

ROCKWELL HARDNESS TEST

AIM: To determine hardness of given sample of metal with the help of Rockwell hardness test.

APPARATUS: Rockwell hardness tester, Standard specimen.

THEORY:

In this method, hardness of metal is correlated with the

depth of indentation and not with the area of indentation as is done in theBrinell and Vickers hardness methods. Harder the material, depth ofindentation is less for a. given load and vice versa. Hence, the hardness isinversely proportional to the depth of indentation of the dial is calibrated inan inverse fashion so that the hardness number becomes directlyproportional to the hardness of the material. In this test, two types ofindenters are used:

(1) Hard steel balls of 1/16", 1/8", 1/4" and 1/2"

diameters.

(2) Brale indenter made of diamond in the form of a cone witl1 included

angle of 120. The tip of the indenter is accurately ground to a radius of 0.2mm.

Loads are applied in two stages. First a constant minor load of

10 kg is applied and then major load is applied. The major loads are

60,100,or 150 kg. These various combinations of indenters and loads are

indicated by letters stitch as A, B, C, etc.; the complete list is given in Table

3.4. In all there are 15 combinations. 'A' letter indicates 60 kg load and Brale

indenter, 'B' letter indicates 100 kg 1.0 ad and 1/16" diameter ball indenter,

'C' letter indicates 150 kg load and Brale indenter and 8.0 on. Few of the

applications .of each scale are given in Table.

PROCEDURE:

1.The specimen is placed on the anvil. The dial pointers are idle. Neitherthe minor

nor the major load is applied.


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2. The anvil along with the specimen is raised so that the specimen

touches the indenter. By further raising the anvil slowly, a

minor load of 10 kg is applied. At this stage, the small pointer of the dial

coincides with the index mark. When the minor load is fully applied, the

large pointer will be in vertical position and automatically matches with

0 mark painted in black ink or 30 mark painted in red ink or a set-point

mark on the dial. (Working of small pointer is not shown in the above

figure). If the large pointer is not at this position, the bezel of the dial is

then rotated until the 0 or 30 or set-pointmark coincides with the large

pointer. The minor load of 10 kg has forced the indenter into the

specimen to a depth upto B i.e (A-B).

In this step, since load is applied in an oppositedirection, the large pointer moves in clockwise direction during

penetration of indenter.3. Major load of 100 kg is applied by means of a release handle provided

on the rightside of the instrument. This load is applied gradually by means of adashpot arrangement.

This major load of 100 kg consists of the original minor loadof 10 kg plus an additional load of 90 kg. The application of major load,has forced the ball into the specimen to additional depth up to C i.e. (B-C).

Due to this, the large pointer moves in counter-clockwisedirection from set point to 40. Corresponding to (B-C), the depth ofpenetration becomes (100 - 40) x 0.002 = 0.120 mm, since eachnumber on dial corresponds to a depth of 0.002 mm.

4. Without removing the minor load of 10 kg, the major load (90 kg out ofthe total 100 kg) is removed. Due to this, elastic recovery in thedeformed region occurs and the impression depth comes to D i.e. depthrecovery becomes (D - C). As a consequence of this, the large pointerrotates in a clockwise direction from numbers 40 to 60 on the dial. Thisdifference of 20 divisions is actually a measure of elastic recovery ofthe metal, corresponding to (D - C).5. Without removal of the minor load, hardness number is read directly

from the dialwhich is 60 in the figure shown. This hardness is designated as RockwellB 60 or RB = 60. It is of interest to note that this hardness number B 60or RB = 60, is actually a reversed measurement of the penetration (B -D) i.e. the depth (B - D) does not correspond to 60 x 0.002 = 0.120 mm,but it corresponds to (100 - 60) x 0.002= 0.08 mm. It is also clear thatthis 0.08 mm depth does not correspond to total depth but correspondsto depth (B - D) only.


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6. The minor load of 10 kg is removed and next reading is taken on thesame specimen at different place in a way similar to above.

The calibration is according to the following equations:

(A)For Brale indenter:

Hardness number = 100 - depth of penetration in mm0.002

(B) For ball indenters:

Hardness number = 130 - depth of penetration in mm0.002

Scale symbols for various

Combinations of Loads and Ball Diameters

IndenterMajor Load, Kg

60 100 150

Cone (Brale) A D C

1/16 - Ball F B G

1/8 - Ball H E K

1/4 - Ball L M P

1/2 - Ball R S V


ComponentCondition

Scale to be usedhaving:

Thin Low load such as 60Kg

Thick High load such as 150Kg

Hard Brale

Soft 1/16 - Ball

Very Soft 1/8 or 1/4 - Ball

Very Very Soft 1/2 - Ball

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Standard Rockwell Hardness Scales And Their Applications

(Minor Load: 10Kg)

ScaleSymb

olIndenter

MajorLoad,

Kg

DialNumera

ls

Typical Application ofscales/ Remarks

B1/16 Ball

(1.6mm)100 Red

Brass, low and mediumcarbon steels in annealedor normalized condition,Al-alloys, soft cast irons,

cast alloys.

CBrale

(Diamondcone)

150 BlackHardened steels, hard castirons, deep case hardenedsteels.

A Brale 60 Black

Hard thin materials likerazor blades, shallow casehardened steels, casecarburized surfaces,cemented carbides.

D Brale 100 Black

Useful for applicationswhere a major load isdesired intermediatebetween those required forA and C scales e.g.medium case hardenedsteels.

E 1/8 Ball(3.2mm)

100 Red Useful for measuringhardness of very softmaterials, such as bearing


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metals, ferritic cast irons,Al and Mg alloys.

F 1/16 Ball 60 Red

Similar to E scale alloysbut thin components,annealed Cu- alloys, thinsoft sheet metals.

G 1/16 Ball 150 Red

Useful for materialsslightly harder than B100e.g. phosphor bronze,beryllium bronze, cupro-nickels.

H1/8 Ball(3.2mm)

60 Red Pb, Zn, Al, MG alloys.

K 1/8 Ball 150 Red

L1/4 Ball(6.4mm)

60 RedPlastic materials, bakelite,vulcanized rubber.

M 1/4 Ball 100 Red

Nylon, polystyrene, flexiglass (Rigid sheet andplate materials used forelectrical insulation aretested by L and M scales).

P 1/4 Ball 150 Red

R1/2 Ball(12.7mm)

60 Red

When the SpringConstant or Correlationfactor is included in thetest procedure, only Rscale is used.

S 1/2 Ball 100 Red

V 1/2 Ball 150 Red


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CONCLUSIONS:

Sr.No.

Material Hardness

01

02

RESULT:

Hardness of the given specimen is =


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PENDULUM IMPACT MACHINE


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CHARPY METAL SPECIMENS (ASTM E 23)

IZOD METAL SPECIMENS (ASTM E 23)


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SPECIMEN ARRANGEMENTS


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PRINCIPLE OF OPERATION OF THE ROCKWELL HARDNESS TESTER


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