NDT ( NON DESTRUCTIVE TESTING )

NDT (NON DESTRUCTIVE TESTING) :-

Non Destructive Testing in great variety are in world wide used to detect variations in structure,minute changes in surface finish, the presence of cracks or other physical discontinuities,measure the thickness of materials and coatings and to determine other characteristics of industrial products.

REASON'S FOR THE USE OF NDT:

"NDT" is used by the manufacturers for the following reasons:

1. To ensure product reliability.

2. To make profit for the user.

a) To ensure customer satisfaction

b) To aid in better product reliability.

c) To control the manufacturing processes.

d) To lower the manufacturing costs.

e) To maintain uniform quality level.

SOME OF THE MOST COMMON NDT METHODS ARE :

1.VISUAL INSPECTION

2.LIQUID PENETRATION TEST

3.MAGNETIC PARTICLE TEST

4.RADIOGRAPHY TEST

5.ULTRASONIC TEST

CHARPY V NOTCH IMPACT TEST

CHARPY V NOTCH IMPACT TEST Object : To determine the amount of energy absorbed in fracturing a standardized test piece at a specified temperature. Method : A machined, notched specimen is broken by one blow from a pendulum. Because scatter occurs in the results, at least three specimens are used to assess the joint represented. Testing is carried out at a temperature specified in the appropriate application standard. Reporting Results: Location and orientation of the notch. Testing temperature. Energy absorbed in joules. Description of fracture appearance. Location of any defects. The Charpy impact test, measured in joules, is an assessment of TOUGHNESS. Transition temperature (curve) in steel.

What is Annealing ?

Annealing:- Annealing Process :- Annealing is a heat treatment process by which the properties of steel are enhanced to meet machinability requirements. In this process Hypoeutectoid steels (less than 0.83% carbon) are heated above upper critical temp., soaked and cooled slowly and Hypereutecoid (above 0.83%) are heated above lower critical temp., soaked and allowed to cool slowly. Annealing Process Steps: 1.Heat material into the asutenite region (i.e. above 1600F) – rule of thumb: hold steel for one hour for each one inch of thickness 2.Slowly furnace cool the steel – DO NOT QUENCH 3.Key slow cooling allows the C to precipitate out so resulting structure is coarse pearlite with excess ferrite 4.After annealing steel is quite soft and ductile The purpose of Annealing is : 1)Reduce hardness and brittleness 2)Alter microstructure for desired mechanical properties 3)Soften...

Part -1 Most commonly asked Mechanical Interview Questions with answer

Most commonly asked Mechanical Interview Questions 1. What is the importance of the Thermodynamics in the field of Mechanical Engineering? All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very important for the mechanical engineers. 2. How many Laws of Thermodynamics are there? There are three laws of the thermodynamics. First Law : Energy can be neither created nor destroyed. It can only change forms.In any process in an isolated system, the total energy remains the same. Second Law : When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, but not in equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems, and they exchange matter or energy, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropy's of the initial, isolated systems is less than or equal to the entropy of the ...

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