Fatigue Fracture

        Fatigue fracture is a fracture that occurs when a material is subjected to cyclic loading and unloading. If the loads are above a certain threshold, microscopic cracks will begin to form at the surface. Eventually a crack will reach a critical size, and the structure will suddenly fracture.

        Rotating shafts, connecting rods, aircraft wings and leaf springs are some examples of structural and machine components that are subjected to millions of cycles of alternating stresses during service. Majority of fractures in such components is due to fatigue.

         Fatigue fracture occurs by crack propagation. The crack usually initiates at the surface of the specimen and propagates slowly at first into the interiors. At some critical stage, crack propagation becomes rapid culminating in fracture.

        The fatigue behavior can be understood from results of fatigue test, which are presented in from of S-N curves.  Samples of material are subjected to alternating stresses of different levels. The number of cycles of stress reversals N required to cause fracture is plotted against the applied stress level S. Some materials such as mild steel show a clearly defined fatigue limit. If the applied stress is below the fatigue limit, (aka Endurance Limit) the material will withstand any number of stress reversals. If materials don't show clearly defined limit, the fatigue limit is defined as stress that would cause failure after a specified number of stress reversals.

       The above info is taken from Material Science and Engineering by Raghavan and the picture shown here is taken from http://www.fea-optimization.com/. Please do refer to them for more info. 

Don't forget to grab a copy of Material Science and Engineering.

with warm regards

AllMyPosts

Relation between E, G and Poisson's Ratio

The definite relationship between Young's modulus, Shear modulus & Poissons ratio  is asked many a times in our old question papers though for two marks only.

So I thought I will put up the answer here:

Let young's modulus = E, Shear modulus = G, Bulk Modulus = K and

poisson's ratio = v

E = 3K(1-2v)

E = 2G(1+v)

the above relationship is taken from answers.com. Please do refer to them for further info.

Don't forget to grab a copy of Material Science and Engineering book, which is essential for preparing for AMIE, Material Science.

with warm regards

AllMyPosts

What is the most fetching topic in Material Science??

Hello Everyone,

    I was wondering about what is the most fetching topic in Material Science. I was going through the old question papers sometime back. I find a pattern when it comes to questions from some chapters like burgers vector, APF of crystal,... I also find that the pattern is not very strong in itself.

    So tell me which topic / chapter is really fetching in material Science of section A of AMIE exams?

Question Papers

Hello Everyone,




I was surfing around on the web and came across these old question papers of AMIE. Please do go through the same.
http://hotfile.com/dl/82063184/a3a06f9/amie_Question_papers_SEC-A_2004-2008.zip.html




The simple way to get the most out of question papers is:

1. Read question papers, group questions belonging to each chapter. This will give you idea about the topics to be covered.
2. Please attempt the old questions and try to answer them all. It gives you both confidence and also lets you know your ability
3. Take a mock test with the help of timer, i.e. try to complete answering the questions in the given time limit. This will help you to maintain calm @ exams

Don't forget to grab a copy of Material Science and Engineering book, which is essential for preparing for AMIE, Material Science.


with warm regards
allmyposts

Status Chap 02

Hello Everyone, 

    Good Day to you all, I was little lazy yesterday. I did not read a single new topic also yesterday. I was making notes of all the topics which I was studied. I am sure making notes is good, as I read from hell lot of sources. I need to study about them all, make and store points at one place for future reference. So its good. Know more about study skills here by buying the book Effective Study Skills: Step-by-Step System to Achieve Student Success at amazon.

    So nothing new today. Just gonna edit old posts to ensure that they are of good quality. 

Don't forget to grab a copy of Material Science and Engineering book, which is essential for preparing for AMIE, Material Science.

with warm regards

allmyposts

Simple, Body Centered & Face Centered Cubic Systems

The three Bravais lattices which form cubic crystal systems are

Simple cubic (P)

Body-centered cubic (I)

Face-centered cubic (F)

The simple cubic system (P) consists of one lattice point on each corner of the cube. Each atom at the lattice points is then shared equally between eight adjacent cubes, and the unit cell therefore contains in total one atom (¹⁄₈ × 8).
The body-centered cubic system (I) has one lattice point in the center of the unit cell in addition to the eight corner points. It has a net total of 2 lattice points per unit cell (¹⁄₈ × 8 + 1).
The face-centered cubic system (F) has lattice points on the faces of the cube, that each gives exactly one half contribution, in addition to the corner lattice points, giving a total of 4 atoms per unit cell (¹⁄₈ × 8 from the corners plus ¹⁄₂× 6 from the faces).
Attempting to create a C-centered cubic crystal system (i.e., putting an extra lattice point in the center of each horizontal face) would result in a simple tetragonal Bravais lattice.


All the above information is taken from Wikipedia. Please refer to Wikipedia for more info.  

Don't forget to grab a copy of Material Science and Engineering book, which is essential for preparing for AMIE, Material Science.


with warm regards
AllMyPosts

Crystal Systems. Bravias Lattices.

Crystal system - Wikipedia, the free encyclopedia -