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

The Brinell Hardness Test

The Brinell Hardness Test The Brinell hardness test method consists of indenting the test material with a 10 mm diameter hardened steel or carbide ball subjected to a load of 3000 kg. For softer materials the load can be reduced to 1500 kg or 500 kg to avoid excessive indentation. The full load is normally applied for 10 to 15 seconds in the case of iron and steel and for at least 30 seconds in the case of other metals. The diameter of the indentation left in the test material is measured with a low powered microscope. The Brinell harness number is calculated by dividing the load applied by the surface area of the indentation. The diameter of the impression is the average of two readings at right angles and the use of a Brinell hardness number table can simplify the determination of the Brinell hardness. A well structured Brinell hardness number reveals the test conditions, and looks like this, "75 HB 10/500/30" which means that a Brinell Hardness of 75 was obtained us...

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.

BEND TESTS

BEND TESTS Object: To determine the soundness of weld metal, heat affected zone and weld zone.These tests may also be used to give some measure of the ductility of the weld zone. It is not usual to use transverse and longitudinal bend tests for the same application. Method: All specimens to be removed and prepared without causing significant distortion or heating. The cap and root are ground flush. The specimen is bent by the movement of a former of prescribed diameter, the relevant side of the specimen to be placed in tension. Angle of bend and diameter of former should be as specified in the appropriate standard. Reporting Results: Thickness of specimen Direction of bend (root or face) Angle of bend Diameter of former Appearance of joint after bending e.g. type and location of flaws

Mechanical Engineering

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