UNIT 1 D
3 marks Questions:
6. Explain the
Bragg’s law of X-ray
diffraction in detail with neat
sketch.
A.
•
The crystal an
diffract x ray because the inter planner spacing in crystal lattice is of some
order as that of wavelength of x ray.
•
Diffraction: It is
a bending of line around the corner and it depend on wavelength.
•
Diffraction due to
inter planner spacing.
•
separation of
layer= x RAY wavelength.
•
X-ray transmitted
to words the crystal lattice. And this Xray are reflected and detected by
detector
•
Ray 2 travel more
distance then ray one.
•
Extra difference is
DE+EF then if ray 2 and ray 1 have a same of phase after reflection thus path difference
is decide if both are in same phase or
not.
The
different layers of crystal
7. What are the
basic processing steps
of a liquid penetrant
inspection?
A. Steps of
Liquid Penetrant Testing :
The general steps can be
summarized as follows:
1. Surface
Preparation : ). One of the
most critical steps
of a liquid a person with a
penetrant testing is the surface preparation.
The surface must
be free of
oil, grease, water,
or other contaminants that may
prevent Penetrant from
entering flaws. The
sample may also
require etching if mechanical
operations such as
machining, sanding, or grit
blasting have been
performed. These and other
mechanical operations can
smear metal over the
flaw opening and prevent the penetrant from entering.
2. Penetrant Application : penetrant material Once
the surface has
been thoroughly cleaned
and dried, the is applied
by spraying, brushing, or
immersing the part
in a penetrant bath.
3. Penetrant Dwell : The
penetrant is left
on the surface
for a sufficient time allow
as much penetrant as
possible to be
drawn from or
to seep into
a defect. Penetrant
dwell time is the
total with the times are by to time that
the penetrant is
in contact part surface. usually
the required being dwell from five Dwell
recommended penetrant producers or by
the specification followed. Minimum times typically
range to 60 minutes. 4. Excess
Penetrant Removal : This is
the most delicate
part of the
inspection procedure because
the excess penetrant
must be removed
from the surface
of the sample
while removing as little
penetrant as possible
from defects. Depending
on the penetrant
system used, this step
may involve cleaning
with a solvent,
direct rinsing with
water, or first treating the
part with an emulsifier and then rinsing with water
5. Developer Application : A thin
layer of developer
is then applied
to the sample
to penetrant trapped in
flaws back to
the surface where
it will be
visible. draw Developers come
in a
variety of forms
that may be
applied by dusting
( ( dry powders wet developers ). ), dipping, or
spraying
6. Indication Development : period The developer Photo Courtesy
of Contoso is allowed to stand on
the part surface for a
of time sufficient to permit the extraction of
the trapped penetrant out of any
surface flaws. This development time is
usually a minimum of 10 minutes. Significantly longer
times may be necessary
for tight cracks.
7. Inspection
: Inspection is
then performed from any flaws
which may be present.
8. Clean Surface : under appropriate lighting The
final step in the process is to
thoroughly clean the part surface to remove the developer from the
parts that were found to be acceptable. to detect indications
8. Differentiate between
substitutional and interstitial solid solution.
A.
Substitutional solid solution
|
Interstitial solid solution
|
Substitutional Solid Solution is formed when some of the atoms of solvent
are replaced by the solute atoms at their normal lattice points, as shown in
Fig.. In the formation of substitutional solid solutions, an element A
cannnot dissolve any amount of element B, its limit (known as solid
solubility limit) is determined by certain factors. These factors were first
studied by Hume Rothery and are
known as Hume Rothery Rules.
 |
interstitial
solid solution is formed when
atoms of small atomic radii fit into the empty
spaces or interstices of the lattice structure of the solvent atoms as shown
in Fig.. Since the empty spaces of the lattice structure are limited in size,
only atoms with atomic radii less than I angstrom are likely to form
interstitial solid solu-tions.
Interstitial solid solutiom normally have
limited solid solubility. The
well known example of this group is
interstitial solid solution of carbon in iron. y-iron can dissolve uptu 2 per
cent carbon at 1147 'C. This interstitial solid solution Of carbon in iron is
the basis for hardening in steel.
Interstitial solid solution ot hydrogen in min
formed during acid pickling (cleaning), plating or welding operations With
steel causes a sharp decrease in ductility of steel. This harmful phenomenon
is known as hydrogen embritllemem.
 |
9. Write difference
between crystalline solid and
non-crystalline solid.
A. Crystalline Solids: Crystalline Solids have an
evenly distributed three-dimensional arrangement of atoms, ions, or molecules.
Non-crystalline solids: Non-crystalline solids
do not have a consistent arrangement of particles.
Properties of Crystalline and Non-crystalline
Solids
Geometrical Shape
Crystalline Solids: Crystalline solids have a
well-defined geometrical shape due to the regular arrangement of unit cells.
Non-crystalline Solids: Non-crystalline solids
do not have well-defined geometrical shape.
Range Order
Crystalline Solids: Crystalline solids have a
long range order.
Non-crystalline Solids: Non-crystalline solids
have a short range order.
Melting Point
Crystalline Solids: Crystalline solids have a
definite melting point.
Non-crystalline Solids: Non-crystalline solids
melt over a range.
Heat of Fusion
Crystalline Solids: Crystalline solids have a
high fixed value for the heat of fusion.
Non-crystalline Solids: Non-crystalline solids
do not have a fixed value for the heat of fusion.
Properties of Solids
Crystalline Solids: Crystalline solids are
true solids. They show all the properties of solids.
Non-crystalline Solids: Non-crystalline solids
do not show all the properties of solids. Therefore, they are called “pseudo
solids”.
Energy
Crystalline Solids: Energy in crystalline
solids is lower than that of non-crystalline solids.
Non-crystalline Solids: Nature favours
crystalline solids due to the low energy arrangement.
10. State different
types of unit cells
and sketch their geometries.
A.• The four basic types of unit
cells are :
Simple
Body Centred cubic
Face centred cubic
Base centred cubic
Hexagonal Closed packed
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