Stress Strain Curve Conclusion - Mechanical Properties of Solids Video Lecture - Class 11

hello friends this video on mechanical
properties of solid part 6 is brought to
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no more fear from exam please make sure
that you have watched all the videos
from part 1 to part 5 before going ahead
with part 6 now let us look at certain
conclusions from the stress-strain curve
that is we reach at certain results
which we arrive at on the basis of our
study from stress-strain curve
this was our stress finger the first
thing which we conclude is an object is
brittle if D and E are very close
so what which was point D this was the
point E where fracture occurs and this
point was point D so it says that if D
and G are very close it needs to points
are very close to each other that means
the object is brittle what do you mean
by brittle beta means an object which
breaks down for example let us say glass
glass is a brittle material it is oppose
you have a bottle made of glass on in
one hand you have a bottle made of glass
and on the other hand you have a plastic
bottle you drop both of them from the
same height or you drop both of them
suddenly what happens the glass bottle
breaks down whereas the plastic doesn't
break like that is because the glass
glasses a brittle substance that is a
substance which easily breaks down so
any substance which is spreader will
have if you draw the stress-strain curve
of a substance which is brittle you will
see that the point D and the point E add
very close so point E as close with the
point E is towards point D that we lose
the fracture may occur more quickly if
point E is very close to point B that
means fracture will occur
so the body will break down very quickly
so try to understand the logic behind
why I began he will be very close if the
object is written I hope you're getting
me because point three is the ultimate
tensile strength that means after point
B the strength of the body will not
increase any more because after point E
is the stress to decrease and the strain
may increase so the body can break down
any knife so if that fracture point is
closure to point D that means it will
break down even more quickly so the
object will be written an object is
ductile if B and D are fired from each
other now in the same way if suppose
point E is far away that means the
object will not break down easily this
object will be ductile what do you mean
by that thing the objects which can be
gives you easily drawn into wires for
example I add all the little I guess I
have discussed in first few slides right
ductility for example if you consider
metals like gold silver you see that you
make chains and all these ornaments of
gold and silver
how come how is that possible so it had
gold or silver been brittle in that is
you you would not have been able to draw
them into thin wires because they will
break down as you try stretching them
they will break down but it is not like
that they have this property because the
fracture point is far away from the
ultimate tensile strength that means if
they break down after a long time that
means after the strain is capable of
getting increased even when given with
decreased stress for a long time so this
region B and D D and B in agent is very
wide so those substances are there like
elastic substances like rubber have
larger elastic region
so more elastic and a substance is the
broader or the larger will elastic
region which is the elastic region so
from A to E is perfectly elastic from a
this is a and
is P so from o to aliens perfectly
elastic a to B is also in the elastic
region so it is the elastic limit that
means this region o to B will be large
so if you think of a substance which is
very much elastic they will have a very
broad elastic region and sorry I have
not drawn it very nicely but it's
something of the sort
if you come see this figure you see that
the plastic region is very small plastic
region is only this much but this
elastic region is four so four
substances which are very much elastic
their elastic region will be more
similarly for substances which are
plastic for them the plastic region
would be more thank you please visit
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