welcome back friends in the previous lecture
we have studied about different moulding sand
properties we have seen how these properties
are going to affect the final quality of the
casting so it is important for a foundry men
to control these moulding sand properties
thats why in this lecture let us see how to
test the moulding sand properties so this
lecture is moulding sand testing these are
the important moulding sand tests one is the
moisture content test another one is the clay
content test next one the grain fineness test
next one the permeability test next one the
compatibility test finally the strength tests
and among the strength test there are four
one is the green compression strength green
shear strength dry compression strength and
finally the hardness
now let us see these tests one by one first
let us see the moisture content test how to
determine the moisture content in a moulding
sand in the beginning we have seen that the
moulding sand should contain moisture from
two to five percent how to know whether it
the moisture is between two to five percent
if the moisture is below two percent what
can happen they may not be enough for what
say binding or if the moisture content is
more than five percent then what happens excessive
of steam and hot gases will be produced and
because of that there will be blow holes and
pin holes on the surface of the casting so
the moisture content should be optimum so
how to measure the moisture content in the
moulding sand so this moisture content can
be measured using an infrared heater so we
can see here this is an infrared heater and
yes uh here we can place the sand spaceman
so when you keep this what say container with
the sand the green sand inside this ah infrared
heater may be after few minutes the moisture
will be dried out then we can find out the
moisture content so this is the ah procedure
place twenty to fifty grams of uh prepared
green sand the pan and heat it in an infrared
uh woven for about two to three minutes then
what happens the moisture in the moulding
sand is evaporated so initially we have weighed
it may be it may be say about twenty two or
fifty grams of the sand now the moulding sand
is taken out from the pan and it is weighed
again the percentage of the moisture can be
calculated from the difference in the weights
the percent of the moisture is equal to w
one minus w two multiplied by hundred whole
divided by hundred what is this w one and
w two w one is the weight of the sand
before drying before we kept inside the infrared
woven and what is w two it is the weight of
the sand after drying difference of these
weights multiplied by hundred whole divided
by initial weight of the sand gives the moisture
content so this is the old and traditional
method of finding the moisture in the green
sand recently a new techniques have been develop
that is the rapid moisture teller so this
is the the new technique develop right so
if the process of the infrared woven it to
takes ah what say we need initially we need
to weigh the sand then we have to put it inside
the woven and heat it about two to three minutes
again take it out and again weigh and we have
to make some calculation
that way it takes about ten minutes totally
whereas this rapid moisture teller tells us
within a minute how so this is a small equipment
so when calcium carbide comes in contact with
the moisture acetylene gas is generated so
this is well known to us now this principle
is used in the rapid moisture teller now what
we will do a weighed quantity of sand sample
is mixed with a fine fixed quantity of calcium
carbide reagent and the whole mixture is thoroughly
shaken in a vessel in which pressure gauge
is fixed now ah we are what say making me
calcium carbide react with the moisture of
the green sand and accordingly acetylene gas
is produced now what is the amount of acetylene
gas produced it depends upon the moisture
content of the moulding sand
now the acetylene gas produced develops pressure
the instrument indicates moisture on the pressure
gauge so this pressure gauge is calibrated
so right so accordingly we can know the percentage
moisture in the moulding sand so this takes
very less time thats why it is known as the
rapid moisture teller
next let us see the clay content test so it
is very important for us to control the clay
in the green sand again so when we are talking
about the clay ah yes initially we will be
mixing the clay or it is also known as the
binder and uh remember among this clay or
the binder the most important binder is the
bentonite now ah in the previous lecture we
have seen that as we keep pouring the molten
metal into the mould as we keep reusing the
sand again and again what happens
part of the clay or the part of the binder
which is close to the mould wall will be heated
above five hundred degree centigrade once
it is heated above five hundred degree centigrade
it loses all its properties binding properties
it cannot create cohesion anymore between
the neighbouring sand grains but physically
it is present so now we need to what say distinguish
between the ah what say actual clay or the
active clay or the total clay now let us see
how to measure clay contest so clay content
means there are two terms is it the total
clay which is um what say ah some of the active
clay and the dead clay or there is the another
test ah in which we only measure the active
clay first let us see how to measure the total
clay content right so this is the what say
an ah instrument used for the total clay content
right
so this is the equipment now this is used
ah what we do is we what say mix the sand
in a container with water and uh we stir it
using this equipment so this is the way separate
fifty grams of dry moulding sand and transfer
to wash bottle right next one add four seventy
five cc of distilled water plus twenty five
cc of three percent naoh sodium hydroxide
now hesitate this mixture for about ten minutes
with the help of the sand stirrer this this
is the sand stirrer next one fill the wash
bottle with water up to the marker after the
sand has settled right siphon out the water
from the wash bottle now after we stir some
time right remember we have mix the sodium
hydroxide
what does this uh sodium hydroxide do it separates
the clay particles from the sand grains and
sees that it ensures that the clay is settle
down sorry clay will be floating and the sandal
will be settle down now while the clay is
still what say mixed with the water will be
siphon it out using a siphon now what is there
inside the bottle only the water not the water
only the ah fine and clear clean sand base
sand is there clay has already been siphoned
out now this sand is to be dried out remember
in the beginning we have taken fifty grams
of the sand next one now the percentage of
the clay content can be calculated as follows
right percentage of the clay content is equal
to w one minus w two into hundred whole divided
by w one
where w one is the weight of the sand before
the test and w two is the weight of the sand
after the test but remember this is the test
for finding out the total clay content but
for us total clay impo ah what say content
is not so important but what is the active
clay because part of the clay becomes the
dead clay so what is the active clay so for
that we need to conduct another test so this
is the clay content to test for the finding
out the active clay the test which we have
conducted previously is to ah that is the
test for finding or the total clay whereas
the this test we will be using for finding
or the active clay right so here we use the
methylene blue what is this mrthylene blue
solution
it is a what say ah heterocyclic aromatic
chemical compound with the molecular formula
c sixteen h eighteen n three scl so this is
the a chemical um formula of the methylene
blue now methylene blue is a potent cationic
dye now ah how to proceed how to conduct this
test so we have to use an apparatus right
so this is the apparatus used for the methylene
blue test in which we will be finding out
the ah active clay content steps in methylene
blue test first one what we have to do is
we have to calibrate the methylene with the
clay system so this methylene blue solution
reacts with the active clay so ah as long
as the active clay is present right so this
methylene blue will be reacting and we cant
see any methylene blue and its effects
now what is happening is ah is uh what say
we will be calibrating say for this much of
what say active clay this much of methylene
blue will be required for reaction for this
much of clay this much of methylene blue is
required so this way what they uh with prior
experiments we have to calibrate the methylene
clay system next one in the second step so
the first part is the calibration second part
is the take five grams of the sand in a stainless
steel container and fifty ml of two percent
tetra sodium pyrophosphate solution via pipette
disperse sand particles using an ultrasonic
accessory right so slowly fill the vessel
with the methylene blue from the burette and
stir the system
now we have what say ah mixture of the sand
and the tetra sodium pyrophosphate right now
what is happening is we are dropping methylene
blue drop by drop now remember in this sand
what say the active clay is there but we are
slowly dropping the methylene blue solution
as we keep dropping the methylene blue solution
the active clay readily reacts with the methylene
blue solution and sees that methylene blue
has no effect this process will continue so
how to know that the clay content is exhausted
methylene blue is dominating using a glass
rod remove a single drop of the liquid and
place it on a filter paper
watch for the formation of a blue green halo
around the central spot so this is the indication
that the active clay is exhausted and methylene
blue is dominating we have to take a what
say glass rod and remove single drop of the
liquid and place it on a filter paper if the
what say active clay is exhausted then there
is little excess amount of methylene blue
and [meca/because] because of that when you
place the drop on the filter paper there will
be a blue green halo means thats an indication
that the active clay content is exhausted
then we have to stop uh what say drop in the
methylene blue solution right so if we dont
see the what say blue green halo increase
the addition of the methylene blue drop by
drop till blue green halo appears
once of this blue green halo appears we have
to stop dropping the methylene blue solution
now we have already calibrated between the
methylene blue solution and the clay content
now how much methylene blue is what say consumed
so that we have to find out from the burette
now from that calculate the amount of from
the burette calculate the amount of the methylene
blue consumed and based on the consumption
of the methylene blue using the calibration
factor determine clay content of the sand
remember that methylene blue doesnt react
with the dead clay it reacts only with the
active clay so that is how we can find out
the active clay in the green sand next one
let us see ah among the moulding sand properties
let us learn how to find out the grain fineness
test
so for finding out the grain fineness test
there will be what say sieve shaker will be
there so the equipment looks like this there
will be different sieves will be there and
here we can see different sieves are there
right so there will be ah for each sieve there
will be a mesh will be there in one mesh there
will be coarser what say holes will be there
in some other meshes medium holes will be
there and in some other meshes fine holes
will be there so initially at the top the
coarser [mess/mesh] mesh will be there you
can see this one is the coarser mesh below
that say the mesh me having the little smaller
holes will be there below that likewise there
will be mo what say more what say ah what
say sieves will be there and
all these will be arranged one over another
at the bottom there will be a pan and here
we can see when all these what say sieves
are arranged together it looks like this and
this is known as the sieve shaker this is
known as the sieve shaker now how to find
out the grain fineness number this remember
first of all what is this grain fineness number
this grain fineness number tells us how big
the sand grains are or how small the sand
grains are if the grain fineness number is
very high means the sand grains are very fine
sand grains on the other hand if the grain
fineness number is very small it indicates
that the sand grains are very coarser sand
grains now this is the way place the sample
of dry sand after removing the clay in the
upper sieve
generally a people place fifty grams or hundred
grams place the sample of the dry sand remember
it is dry sand and free from the clay next
one yes uh we put it in the here we open this
lid and here we places that to dry sand fifty
grams or hundred grams next vibrate the sieve
shaker for a definite period yes this can
be vibrated there will be a vibrating system
will be there we can set it to the for vibrating
ten minutes five minutes or fifteen minutes
and uh this whole structure will be vibrating
now what happens the sand which we have placed
inside slowly it will be coming down and if
they ah remember and this sand may contains
different what say grain sizes right maybe
few sand particles or coarser few sand particles
are finer and few sand particles are of medium
size and
accordingly the finest particles will reach
the bottom pan whereas the medium sized sand
particles will be collected somewhere in the
between in between whereas the coarser particles
will be remained in the upper sieves so that
is how the sand will be distributed in different
sieves now where now we stop vibrating this
sieve shaker weigh the amount of sand retained
on each sieve means we have stop it and we
have to to remove separate all these sieves
and carefully collect the sands that are collected
in each and every sieve and we how to very
precisely we have to vary sands in all these
pans then compute the percentage of distribution
of the grains so this is the data sheet for
the sieve analysis right so here we can see
each sieve has been given a specific number
right
so what is the sand ah initially we have dropped
right and the percentage we have to enter
here next one is this is the cumulative percentage
and say for each uh what say sieve there will
be a multiplier will be there now after that
there will be a product product of a and b
means uh percentage collection of the sand
in each sieve multiplied by the ah what say
this multiplayer product right ah this is
the product a into b now grain fineness number
it is indicated by gfn is equal to sum of
products means these are the products these
are the products sum of the products divided
by sum of the percentage weights of the sands
retains what are these percentage weights
and here we can see these are the percentage
weights and if we add up these here we get
the sum of the percentage weights means
sum of these products divided by sum of these
percentage weights gives us the grain fineness
number that is how we can find out the grain
fineness number grain fineness number is indicated
by or simply is known as the gfn now let us
take a problem a sample of fifty grams of
moulding sand was sieved through a sieve shaker
the quantities of sands collected in different
sieves were recorded determine afs grain fineness
number of the said sand and what are the quantities
of the sands collected in different sieves
so these are the quantities of the sands remember
the different sieves are assigned the different
numbers the first sieve is assigned the number
six
the second sieve is assigned number twelve
third sieve twenty fourth sieve thirty fifth
sieve forty sixth sieve fifty seventh sieve
seventy eighth sieve hundred ninth sieve one
forty tenth sieve two hundred eleventh sieve
two hundred and seventy and the finally the
pan will be there so totally including the
pan there will be twelve sieves will be there
of course pan cannot be considered as the
sieve with excluding the pan there will be
eleven sieves will be there now in these sieves
so these are the sands collected in the right
in the first i think first four sieves there
was no sand was corrected next one in the
war say ah uh forty is excessive means the
ah sieve with the number fourteen point two
grams were collected
similarly in the sieve with number fifty point
six five grams were collected similarly in
the sieve with number seventy one point two
grams were collected similarly in the sieve
with the number hundred two point two five
grams are collected and in the sieve with
number one forty eight point five five grams
are collected in the sieve with number two
hundred eleven point zero five grams are collected
and with the last sieve with the number two
seventy ten point nine grams are collected
and finally in the pan nine point three grams
are collected and these are the total we can
see forty for point one grams are retained
or collected right and there will be a loss
will be there there will be a toss because
say ah some sand grains will be trapped between
the meshes and when we separate the meshes
and we when we what t say ah take them out
some sand particles are tapped and they wont
come out that is how though we have what say
taken fifty grams and finally if we add up
all the sands which we take from different
sieves it will be less than fifty grams now
this is the given data so this is these are
the right ah afs sieve numbers these are these
are all and this is the these are the sand
what say amounts collected in different grain
what say sieves and in the first four sieves
no sand is collected and these are the sands
collected in different sieves now this is
the percentage of the sand retained now what
is the amount of sand that we have taken we
have taken fifty grams of sand now what is
the ah in fifty grams of the sand
so this is the amount of sand contained point
two grams and if you want the percentage it
will be point four grams and ah uh here in
the sieve with the number fifty point six
five grams are were retained now what is the
percentage one point three similarly here
it is two point four and here it is four point
five and here it is seventeen point one twenty
two point one right twenty one point eight
and eighteen point six and this is the sum
of the what say ah amounts of the sands retained
in different sieves that the percentage uh
what say of the retained sands here now ah
here we can see an important curve curve that
is the multiplier for each sieve there is
a particular multiplication factor right
for the first sieve the multiplication factor
is three for the second sieve ah means with
the sieve number twelve the multiplication
is factor is five and for the third sieve
the multiplication factor is ten and for the
fourth sieve the multiplication factor is
twenty right for the see what say sieve with
uh number forty the multiplication is thirty
for the sieve with number fifty the multiplication
factor is forty and for the sieve seventy
the multiplication factor is fifty for the
sieve hundred the multiplication factor is
seventy for one forty sieve the multiplication
factor is hundred for two hundred sieve the
multiplication factor is one forty for two
seventy sieve the multiplication factor is
two hundred and for the pan the multiplication
factor is three hundred and
it is easy to remember these multiplication
factors for example i will show you see here
we can see it this is the multiplication factor
multiplication factor ah say uh for example
you consider this sieve with two seventy what
is its multiplication factor two hundred that
two hundred is the previous sieve number you
see this is the previous sieve number similarly
for two hundred mesh sieve the multiplication
factor is one forty but you see what is this
one forty this one forty is the sieve number
of the previous sieve number you see similarly
for one forty sieve the multiplication factor
is hundred and what is that hundred it is
the sieve number all right ah the sieve ah
the previous sieve number you see like this
likewise it is easy to remember these multiplication
factors now in the last column we are finding
out the product a into b
where a is the percentage of the sand retained
in each sieve b is the multiplication factor
which is assigned for what say each and every
sieve now here we are making product a into
b now the total the sum of the product is
fifteen thousand two hundred and forty three
the sum of the percentages of sands retained
is eighty eight point two now we will find
out the grain fineness number grain fineness
number is equal to sum of products divided
by sum of percentage weights of sands retained
what is the sum of products sum of products
is this much fifteen thousand to forty three
and what say sum of percentage of the sands
retained is eighty eight point two so yes
now we have substituted those values in this
formula
now we are getting grain fineness number is
equal to one seventy two point eight or it
is approximately equal to one seventy three
afs so the afs grain fineness number four
theses sand is one seventy three so this is
the way to find out the ah what say grain
fineness number of the moulding sand so remember
this uh what say what say number seems to
be little high generally in most of the sand
foundries the grain fineness number right
of the sand casting industries it will be
between say say fifty to seventy so that is
the normal what say grain fineness number
of those sands and here the grain fineness
number is hundred and seventy means this is
very fine sand
on the other hand if the number happens to
be very low below fifty or below forty then
its a very coarse sand whereas this one is
a very fine sand so that is all that is the
interpretation of the grain fineness number
next one let us see the permeability test
we have seen that what is permeability permeability
is the ability of the moulding sand to enable
hot gases to pass through the neighbouring
sand grains and finally to the atmosphere
because when we pour the molten metal the
moisture in the moulding sand readily reacts
with the molten metal and forms steam and
hot gases these stream and hot gases will
be escaping through the ah gaps between the
neighbouring sand particles and finally they
leave the mould so a good moulding sand should
have this property of the permeability
if the permeability is not adequate what happens
the gases thus produced will be accommodated
inside the mould and finally they lead to
the gas and blow defects blow holes defects
now how to know whether our sand has the required
permeability or not so we have to determine
so how we will determine this permeability
the quantity of the air that will pass through
a standard specimen of the sand at a particular
pressure condition is called the permeability
of the sand means we will make a sand specimen
may be generally it is two inches diameter
and two inches height and generally about
say ah two thousand cc of uh air will be made
to pass a at a particular pressure but whether
two hundred cc will pass right or not uh we
have to see so that is how we used to measure
the permeability so for that purpose ah we
use the sand rammer right
so this is the specimen tube its a cylindrical
tube and inside this is what say specimen
tube we placed the sand for placing the sand
effectively we place the tube here take this
tube and put it here so this is the filler
accessory and through this of funnel we what
say drop the ah what say green sand and the
grain sand green sand will be dropping inside
this specimen tube and now we place this specimen
tube here so this the sand rammer so this
sand rammer has a hammer you can see and this
is the hammer and this is the what say hand
uh spindle we can rotate this spindle like
this and every time when you rotate this hammer
will go and suddenly will fall again if we
rotate it will go and it suddenly it falls
so when we place this what say sand specimen
here and with the sand inside that and yes
now you rotate the what say that spindle the
hammer goes up and falls down and the sand
will be compacted generally people give three
to five rams now the sand will be compacted
inside the specimen tube right now we now
to take this specimen tube with the compacted
sand inside to the permeability meter so this
is the permeability meter or the permeability
ah test apparatus now how to measure the what
say permeability using this permeability apparatus
now ah previously we have filled what say
moulding sand in this specimen tube we have
to bring this placement tube and we have to
place it here we can see here there is a what
say whoop ring here we have to place it and
here we can see there is a jar there is a
jar and there will be water in it and with
this what say
what say handle ah or a this lid can be raised
up then what happens air will be going inside
now when you release it slowly the air will
be coming out and it will be passing through
this tube and finally it will pass through
the sand specimen so this is the ah what say
ah what says permeability apparatus right
what are the components it has an inverted
bell jar which floats in a water so this is
the inverted bell jar now it right specimen
tube for holding these sands specimen right
so here we place the specimen tube and finally
there is a manometer for measuring the air
pressure and here we can see there is a manometer
what are the steps involved two hundred cc
volume of air held in the bell jar and
it is forced to pass through the sand specimen
at this time air entering the specimen is
equal to the air escaped through the specimen
take the pressure reading of the ma manometer
right note the time required for the two hundred
cc of air to escape through the specimen now
permeability can be measured like this permeability
number is equal to vh divided by apt where
v is the volume of the air h is the height
of the specimen in centimeters a is the area
of the cross sectional area of the specimen
that is the space centimeters next one p is
the air pressure grams per square centimeter
next one t is the time taken by the air to
pass through the sand specimen and this is
expressed in seconds now let us take a problem
determine the permeability of a afs standard
what say specimen of five point zero eight
centimeters means two inches diameter and
five point zero eight centimeters means two
inches height the air drum was raised to take
two thousand right centimeter cubic centimeters
of air into it the whole air was then allowed
to escape through the sand specimen at a pressure
of ten grams per or centimeter square meter
this is square in a span of fifteen seconds
now ah how to calculate the permeability first
of all this is the formula for the permeability
permeability number vh by apt where v is the
volume of the air in cc h is the height of
the specimen in centimeters a is the cross
sectional area of the specimen square centimeters
and p is the air pressure next one t is the
time taken by the specimen to pass through
ah time taken by the air to pass through the
specimen and it is experienced in seconds
that way v is equal to two thousands centimeter
cube cubic centimeters next one h is is the
height of the specimen that is five point
zero eight centimeters a is the cross sectional
area of the specimen that is twenty point
two six eight square centimeters p is the
air pressure that is ten grams per square
centimeter next one t is the time that is
the fifteen seconds now we have the formula
so this is the [fo/formula] formula for the
permeability vh by apt let us substitute these
values in this formula when we substitute
and simplified the permeability becomes two
hundred and five so this is the permeability
of the sand so we have seen how to measure
the permeability of the sand moulding sand
next one let us see the compatibility test
so we have covered moisture content test clay
content test grain fineness test permeability
test and now let us see the compatibility
test
what is this compactibility the compactibility
indicates the water tempering degree of the
green sand moulding then how to measure it
compactibility is the percentage decrease
in height of a loose mass of sand under the
influence of a controlled compaction we take
the what say loose sand and we make a controlled
compaction then what is the reduction in height
percentage reduction in height that is the
compactibility so this is the compactibility
scale accessories right mounted on the sand
rammer sometime back we have seen the sand
rammer right so to measure the compactibility
this is the compactibility accessory which
is fitted on the sand rammer now we can see
here since these are the we can see here three
ah specimens are there specimen tubes and
this is the moulding sand this is also the
moulding sand and this is also the moulding
sand
and all the three specimens are given same
compaction may be they they are given three
what say rams but see the reduction is this
much in this case the in this case in the
second case the reduction is this much in
the third case the reductionism this much
means the third sample has the highest compactibility
and this is how the compactibility varies
with the clay content now testing procedure
how to measure the compactibility position
a specimen tube and pedestal cup on the tube
filler beneath the funnel outlet next one
pass the sand to be tested through the screen
until the specimen tube is filled so fill
this specimen with the moulding sand loosely
dont compact to yourself right next one stickle
the what say sand level with the top of the
tube if there is any excess sand that one
we have to stickle next one remove the specimen
tube and place in position on the sand rammer
now we have to take this specimen tube
after placing sand inside and we have to put
it under the sand rammer now this is the sand
rammer and this is the specimen tube and the
specimen tube and we have to place it here
and right so this is the what say oh we can
with that we can rotate and we here we can
see this is the hammer and it goes suddenly
it falls goes suddenly it falls now when we
place the specimen tube with sand and uh we
can give rams generally lower the plunger
and gently on to the sand and ram three blows
three rams have to be given then what happens
this is the accessory to measure the what
say ah this compactibility now this accessory
will be fitted here will be fitted here now
when we give the three rams certainly there
will be reduction in the height of the sand
if it has got a good compactibility there
will be more reduction and if it has a poor
compactibility there will be less reduction
accordingly read the percentage conpactibility
by the position of the top of the plunger
shaft on the scale so here we can see how
much reduction is there accordingly from that
we can see the percentage reduction also so
that is how we can find out the compactibility
of this moulding sand finally let us see the
strength tests under the strength tests we
have the green compression strength and we
have the green shear strength we have dry
compression strength and finally we have the
hardness so let us see how to measure the
green compression strength for measuring the
green compression strength also we have to
prepare the sand specimen in the same way
yes uh this is the sand what say tube specimen
tube and in this we have to place the moulding
sand
now we have to ah what say give the blows
or we have to make the give the rams generally
three rams or five rams now right so the this
is used for the ah what say filling easily
means what say the specimen tube is kept here
and uh through this way we put the moulding
sand we place the moulding sand so the moulding
sand is easily placed in to the it is easily
placed in to the tube now there is a universal
sand strength machine is there you can see
this is the universal sand strength ah what
say machine now we we have to prepare the
sand specimen yes this is the tube and in
the in to that we have to place the moulding
sand and using the rammer and we have to make
the rams and the sand will be compacted and
here we can see the what say specimen separator
so using that ah we can separate the sand
specimen from the tube and this sand specimen
we have to kept keep here so these are the
here we can see there is a pendulum is there
right this pendulum here we can see is a small
wheel is there and when we rotate this wheel
what happens the pendulums slowly goes up
and here there is a graduation is there and
here there is a scale and for uh what say
green uh what say compression strength there
will be one scale will be there green shear
strength there will be another scale will
be there similarly for dry compression strength
and dry shear strength there will be another
two more scales will be there totally there
will be four scales will be there here
now we are measuring the green compressions
strength for measuring the green compression
strength right we have to put this specimen
at the bottom at the bottom and these what
say specimen holders will be plane holders
plane holders right between these plane holders
we place this specimen and when we rotate
this pendulum as it goes up the weight of
the pendulum falls on the sand specimen at
one stage this specimen breaks and a magnet
will be ah what say carried along with the
pendulum somewhere here a magnet will be there
so as the pendulum is going up it goes they
magnet goes along with that the moment the
sand specimen breaks there the what say magnet
will be what say arrested and uh of course
the pendulum comes back because the specimen
is broken now ah where the what say magnet
is arrested the that is the what say green
compression strength next one using the same
what say ah what say sand ah universal sand
strength machine
we can also measure the green shear strength
right so this is the here we use the specimen
pads used for the shear strength so here the
specimen pads are different from the specimen
pads that are used for measuring the green
ah compression strength in the case of the
um measuring the green compression strength
the specimen pads are plane they are plane
here they have a ah projection here he this
is one pad and there is a projection here
and this is the other pad and here also there
is a projection and in between we place the
sand specimen and yes uh we place it on the
ah what say universal ah what say sand strength
machine what happens as the machine what say
pendulum is going up what happens previously
compression force was falling on the specimen
now because of the what say pads the nature
of the pads now a shear force will be acting
on the specimen again same thing you keep
rotating this ah right pendulum pendulum will
be going up at one stage they there will be
shear will be maximum and the specimen will
be broken and uh the magnet will be carried
along with the pendulum at one place it will
be arrested where it is arrested and now we
have to refer to the scale which is meant
for measuring the green compression strength
right there ah note down that uh reading that
is the green compression strength now same
uh same way we can also find out the dry compression
right so ah for measuring the dry ah dry compression
strength yes uh ah yes at the bottom for uh
this is the position for placing the or for
finding out the green shear strength and green
compression strength
when we want to measure dry compression strength
and dry shear strength we have to place the
specimen here at the top and the same thing
the pendulum will be there and we have to
rotate the pendulum will be raised up as it
is raised up the load will be falling on the
sand specimen but one uh thing is here more
load will be falling on the sand specimen
same thing if we want to find out the dry
compression strength yes uh keep rotating
that at one stage the specimen fails and now
we have to refer to that scale which is meant
for measuring the dry compression strength
from that scale and from where the magnet
has stopped that is the reading of the dry
compression strength similarly if we want
to measure the dry shear strength now we have
to change the pads for measuring the dry compression
strength and uh what say green compression
strength the pads will be plane for measuring
the dry shear strength and for measuring the
green shear strength
the pads will have what say projections on
both the sides so because of the projections
your shear will be induced now here we have
to use the second ah set of the pads though
which are meant for measuring the shear strength
yes the dry specimen will be here and keep
rotating the pendulum at once stage they will
fail now we have to refer to the scale which
is meant for uh ah measuring the dry shear
strength where the magnet has stopped that
indicates the dry shear strength of the specimen
finally this is the ah determination of the
mould hardness so ah right for measuring the
hardness so this is the what say small device
this is known as the hardness tester now ah
right it is what say uh there is a scale is
graduated inside the dial now here we can
see there is a small what say ah projection
is there
so this uh actually is pushed when we want
to ah find out the hardness hardness indicates
the resistance of the mould to plastic deformation
due to evolution of the gases it also indicates
the resistance against erosion due to flow
of melt so that is the hardness now what we
do we prepare the sand specimen and above
the sand specimen we take this hardness tester
and press it and here is the knob and the
knob will be little pushed up because of done
that what say the dial gauge here it will
be rotating how much it is rotating accordingly
we can know the hardness of the moulding sand
not only what say what say specimen even on
the final mould we can find out the hardness
in a similar way just to take this hardness
tester and press it on the mould and we can
know the reading
friends ah in this uh what say lecture we
have seen the ah different methods to find
out the properties of the ah moulding sand
right not the properties how to conduct the
ah what say different tests and we have learnt
how to measure the moisture content test right
and we ha under the moisture content is the
traditional method we have learnt and the
rapid moisture teller method also we have
learnt next we have seen to ah what is the
method to find out the clay content the active
clay and the total clay both the methods we
have seen for finding out the ah what say
active clay there is a method called the methylene
blue test so that we have learnt next one
we have seen how to measure the grain fineness
number right
so the grain fineness number indicates the
size of the sand particles if the grain fineness
number is very low the sand particles are
very coarser on the other hand if the grain
fineness is very high the sand particles are
very fine particles so how to they measure
this grain fineness number we have learned
next one permeability permeability means ability
of the moulding sand to allow hot gases to
pass through the sand system so this is very
important so we have seen how to measure the
permeability next one what is this compactibility
right percentage reduction when a what say
it is rammed or a compaction is made so we
have seen how to measure the compactibility
under under the ah strength tests we have
seen how to measure the green compression
strength and how to measure the green shear
strength and how to measure the dry compression
strength and finally the hardness so with
this we are closing the what say moulding
sand testing we will meet in the next lecture
thank you
