what are the service requirements for..
1.Automobile engine- two wheeler
2.spindle of a lathe machine
3.artificial bone implant in human body
4.car bumper
5.tennis racket handle
post your comments....
Monday, 21 July 2014
Friday, 18 July 2014
HCP unit cell query
let's see what if we take it as unit cell
repetitive arrangement of it will give as arrangement of atoms as below
top view of the above arrangement is
now let us look at arrangements of atoms in hcp
so, can we take it as unit cell in hcp structure???
Thursday, 17 July 2014
Friday, 11 July 2014
Iron-Carbon diagram
The iron-carbon phase diagram is important in engineering as it provides the basis for understanding all cast irons and carbon steels and their heat treatment. For structural and mechanical applications, steels and other alloys based on iron (the ferrous alloys) are the dominant engineering alloys. They are intrinsically stiff, strong and tough, and mostly low cost. High density is a drawback for transport applications, allowing competition from light alloys,wood and composites. The wide range of applications reflects the many classes of ferrous alloy – different chemistries combined with different process histories. Here, we focus on ferrous alloys which are predominantly iron and carbon alone.
Examples of typical applications of iron-carbon alloys are:
- Cast iron brake discs. Brake discs use sliding friction on the brake pads to decelerate a moving vehicle,
generating heat in the process.The key material properties are therefore hardness (strength) for wear resistance, good toughness and a high maximum service temperature. Casting is the cheapest way to make the moderately complicated shape of the disc. Cast irons contain typically 2-4 wt % carbon, giving a lot of the hard compound iron carbide, giving excellent precipitation hardening.
- Plain carbon steel: I-beams, cars and cans. If we had to single out one universally dominant material, we might well choose mild steel – iron containing 0.1-0.2 wt % carbon. Almost all structural steels, automotive alloys and steel packaging (beer and food cans) are made of mild steel (or a variant enhanced with a few other alloying additions). All of these applications are wrought – the alloy is deformed extensively to shape. The excellent ductility of plain carbon steel enables this, while the deformation process exploits their work hardening to give the required product strength. Ductility, toughness and decent strength are vital in a structural material.
Thursday, 10 July 2014
Phase diagrams
Many of the engineering materials possess mixtures of phases, e.g. steel, paints, and composites. The mixture of two or more phases may permit interaction between different phases, and results in properties usually are different from the properties of individual phases. Different components can be combined into a single material by means of solutions or mixtures. A solution (liquid or solid) is phase with more than one component; a mixture is a material with more than one phase. Solute does not change the structural pattern of the solvent, and the composition of any solution can be varied. In mixtures, there are different phases, each with its own atomic arrangement. It is possible to have a mixture of two different solutions!
A pure substance, under equilibrium conditions, may exist as either of a phase namely vapor, liquid or solid, depending upon the conditions of temperature and pressure. A phase can be defined as a homogeneous portion of a system that has uniform physical and chemical characteristics i.e. it is a physically distinct from other phases, chemically homogeneous and mechanically separable portion of a system. In other words, a phase is a structurally homogeneous portion of matter. When two phases are present in a system, it is not necessary that there be a difference in both physical and chemical properties; a disparity in one or the other set of properties is sufficient.
There is only one vapor phase no matter how many constituents make it up. For pure substance there is only one liquid phase, however there may be more than one solid phase because of differences in crystal structure. A liquid solution is also a single phase, even as a liquid mixture (e.g. oil and water) forms two phases as there is no mixing at the molecular level. In the solid state, different chemical compositions and/or crystal structures are possible so a solid may consist of several phases. For the same composition, different crystal structures represent different phases. A solid solution has atoms mixed at atomic level thus it represents a single phase. A single-phase system is termed as homogeneous, and systems composed of two or more phases are termed as mixtures or heterogeneous. Most of the alloy systems and composites are heterogeneous.
It is important to understand the existence of phases under various practical conditions which may dictate the microstructure of an alloy, thus the mechanical properties and
usefulness of it. Phase diagrams provide a convenient way of representing which state of aggregation (phase or phases) is stable for a particular set of conditions. In addition, phase diagrams provide valuable information about melting, casting, crystallization, and other phenomena.
for more click on the links below
crystal structure
crystal structure
o
Crystallography:
It is that branch of science in which the internal structures of crystals,
their properties, external or internal symmetries of crystals are studied.
o
Various terms
associated with Crystallography.
(i)
Crystal
(ii)
Structure:
The structure implies the arrangement of the atoms within a crystal.
Other important terms – Space
lattice, Unit cell, Atomic planes, lattice parameters, Miller indices etc.
o
Classification of
solids:
1. Crystalline: If the atoms or
molecules in a solid are arranged in
regular fashion, then it is known as
Crystalline solid.
2. Amorphous: When the atoms or molecules in a solid are arranged in
an irregular fashion, then it is
known as amorphous solid.
o
Polycrystalline
Materials: When in a
solid material is build up of a large number of small interlocking crystals or
grains it is called polycrystalline.
o
Space lattice
& Crystal lattice:
The atoms arrange themselves in distinct pattern in space called a space
lattice. It can be considered as an infinite array of points in space, so
arranged that it divides space into equal volumes with no space excluded. In a
space lattice every point has identical surroundings.
o
Unit cell &
its lattice parameters:
It is the smallest group of atoms possessing the symmetry of the crystal.
for more click on the link given below
http://en.wikipedia.org/wiki/Crystallography
for more click on the link given below
http://en.wikipedia.org/wiki/Crystallography
Syllabus
Nirma University
Institute of Technology
SYLLABUS
Sr. No
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|
1.
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Crystal Structure:
- Space lattice, Unit
cell, Crystal systems, Simple Cubic, Body Centered Cubic, Face
Centered Cubic, Hexagonal Closed Pack structures.
- Atomic packing factor, Co-ordination number,
Crystallographic planes and directions (Miller Indices).
|
2.
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Phase Diagram and Theory of Alloys:
- Phase rule, Cooling curves, Lever rule,
important binary phase diagrams, isomorphous system, eutectic system,
peritectic system,
- Construction, significance and applications of
phase diagrams.
- Iron-iron
carbide (Fe-Fe3C) equilibrium diagram.
- Solid solution and its classification,
Hume-Rothery’s rule.
|
3.
|
Steel:
- Classification of steel.
- Effect of alloying elements on the properties
of steels.
- Carbon Steels and alloy steels, Stainless
steel, tool and die steels, high temperature alloys etc.
- Selection of steels for various machine
components and mechanical elements.
- Exposure to national & various
international standards such as ASTM, AISI, SAE, IS, DIN, JIS etc.
|
4.
|
Cast Iron:
- Classification of cast iron.
- Properties and uses of grey, white, malleable,
and spheroidal graphite cast irons.
- Heat treatment of cast irons, seasoning of
cast iron.
- Use of specific grades of cast iron in
mechanical field.
|
5.
|
Nonferrous Metals and
Alloys:
- Composition, properties & uses of
important Aluminum alloys & Copper alloys.
- Heat treatment of the above alloys.
|
6.
|
Powder Metallurgy:
- Introduction, Advantages, limitations &
application of powder metallurgy.
- Steps in manufacturing of powder metallurgy
components viz., preparation of metal powders, compaction, sintering etc.
- Typical products of powder metallurgy:
Filters, Babbitt bearings for automobiles, cermets, cemented carbides tools,
diamond impregnated tools etc.
|
7.
|
Heat Treatment of
Steels:
- Purpose of heat treatment
- Study of heat treatment processes such as
annealing, normalizing, hardening, tempering, TTT diagram, carburizing,
nitriding, cyaniding, martempering, austempering, induction hardening and
flame hardening.
- Cryogenic treatment of materials.
- Hardenability and its determination.
- Applications of above processes to machine
components & mechanical elements such as gears, shafts, crankshafts,
turbine blade, bearings, pistons etc.
|
8.
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Nondestructive Testing
of Materials:
- Advantages and limitations of NDTs, Types of
NDTs,
- Principle, procedure, advantages, limitations,
and applications of the following non-destructive testing (NDT) methods:
X-rays
and Gamma-rays radiography, Magnetic particles
inspection,
Ultrasonic testing, Dye penetrant inspection
and
Eddy
current testing.
|
9.
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Composite Materials:
- Introduction, Classification of composites,
- Properties and applications of composites.
|
10.
|
Ceramic Materials:
- Mechanical properties of ceramics, types and
applications of ceramics
- Glass and glass-ceramics,
- Refractories and their classification.
|
11.
|
Advanced Materials:
- Introduction
- Nano materials, smart materials,
materials for space applications
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