8/2/2019 Nondestructive Testing and Its Day4

http://slidepdf.com/reader/full/nondestructive-testing-and-its-day4 1/3

NONDESTRUCTIVE TESTING AND IT’S

DAY-TO- DAY APPLICATIONSooraj.R , Naga BalA,sooraj194@gmail.com,9566100361

Abstract:

In my paper I am going to explain about NDT

(NON DESTRUCTIVE-TESTING).In this highly

competitive world it’s our duty to do any task perfectly inorder to win the battle. In the field of manufacturing many

products come but only the best will be able to survive and

will be opted by the customers. Hence during

manufacturing it’s our duty to manufacture a product withnull or least defects only then it can serve the purpose for

the fullest. For example consider a screw, only when it is

manufactured perfectly with no voids it can hold a part of 

machine rigidly or else it may fall causing destruction of 

the machine and loss of money. Hence before launching a

product it must be tested for defects, if there was any it

must be rectified. One of the best methods for testing a

finished product is NDT. It is widely used now-a-days.

Keywords: Non-destructive testing

1.Introduction:

Nondestructive testing or Non-destructive testing

(NDT) is a wide group of analysis techniques used in

science and industry to evaluate the properties of a

material, component or system without causing damage.

The terms Nondestructive examination (NDE),

Nondestructive inspection (NDI), and Nondestructive

evaluation (NDE) are also commonly used to describe thistechnology. Because NDT does not permanently alter the

article being inspected, it is a highly-valuable technique

that can save both money and time in product evaluation,

troubleshooting, and research. Common NDT methods

include ultrasonic, magnetic-particle, liquid penetrant,

radiographic, remote visual inspection (RVI), eddy-current

testing, and low coherence interferometry . NDT is a

commonly-used tool in forensic engineering, mechanical

engineering, electrical engineering, civil engineering,

systems engineering, aeronautical engineering, medicine,

and art. In this paper, I am going to explain the applications

of NDT in our day-to day life’s. And in what all fields it is

being used and why???They are widely used in many

fields but I m going to portray very few but important

one’s 

2.Applications

a. Weld verification

1. Section of material with a surface-breaking crack that is

not visible to the naked eye.

2. Penetrant is applied to the surface.

3. Excess penetrant is removed.

4. Developer is applied, rendering the crack visible.

In manufacturing, welds are commonly used to join two or

more metal surfaces. Because these connections may

encounter loads and fatigue during product lifetime, there is

a chance that they may fail if not created toproper specification. For example, the base metal must

reach a certain temperature during the welding process,

must cool at a specific rate, and must be welded with

compatible materials or the joint may not be strong enough

to hold the surfaces together, or cracks may form in the

weld causing it to fail. The typical welding defects, lack of 

fusion of the weld to the base metal, cracks or porosity

inside the weld, and variations in weld density, could cause

a structure to break or a pipeline to rupture.

Welds may be tested using NDT techniques such

as industrial radiography or industrial CT

scanning using X-rays or gamma rays, ultrasonic

testing,liquid penetrant testing or via eddy current. In a

proper weld, these tests would indicate a lack of cracks inthe radiograph, show clear passage of sound through the

weld and back, or indicate a clear surface without penetrant

captured in cracks.

Welding techniques may also be actively monitored with

acoustic emission techniques before production to design

the best set of parameters to use to properly join two

materials.

b.Structural mechanics

8/2/2019 Nondestructive Testing and Its Day4

http://slidepdf.com/reader/full/nondestructive-testing-and-its-day4 2/3

Structures can be complex systems that undergo

different loads during their lifetime. Some complex

structures, such as the turbo machinery in a liquid-fuel

rocket, can also cost millions of dollars. Engineers will

commonly model these structures as coupled second-order

systems, approximating dynamic structure components

with springs, masses, and dampers. These sets of 

differential equations can be used to derive a transferfunction that models the behavior of the system.

In NDT, the structure undergoes a dynamic input, such as

the tap of a hammer or a controlled impulse. Key

properties, such as displacement or acceleration at different

points of the structure, are measured as the corresponding

output. This output is recorded and compared to the

corresponding output given by the transfer function and the

known input. Differences may indicate an inappropriate

model (which may alert engineers to unpredicted

instabilities or performance outside of tolerances), failed

components, or an inadequate control system. 

c. Radiography in medicine

Chest radiography indicating a peripheral bronchial

carcinoma. 

As a system, the human body is difficult to model as acomplete transfer function. Elements of the body, however,

such as bones or molecules, have a known response to

certain radiographic inputs, such as x-rays or magnetic

resonance. Coupled with the controlled introduction of a

known element, such as digested barium, radiography can

be used to image parts or functions of the body by

measuring and interpreting the response to the radiographic

input. In this manner, many bone fractures and

diseases may be detected and localized in preparation for

treatment. X-rays may also be used to examine the interior

of mechanical systems in manufacturing using NDT

techniques, as well.

2.Methods and techniques:

There are several methods in which non destructive

testing can be done .I am going to explain three common

and main techniques in specific. They are

a. Ultrasonic testing

b. Radiographic testing

c. Eddy current testing

a. Eddy current testing:

The main applications of the eddy current

technique are for the detection of surface or subsurface

flaws, conductivity measurement and coating thicknessmeasurement. The technique is sensitive to the material

conductivity, permeability and dimensions of a product

.Eddy currents can be produced in any electrically

conducting material that is subjected to an alternating

magnetic field (typically 10Hz to 10MHz)

Advantages of Eddy Current Testing

• Suitable for the determination of a wide range of 

conditions of conducting Material , such as defect

detection, composition, hardness, conductivity,

Permeability etc. in a wide variety of engineering metals.

• Extremely compact and portable units are available. 

• No consumables (except probes –  which can

sometimes be repaired).

• Flexibility in selection of probes and test frequenciesto suit different

applications.

• Suitable for total automation. 

Disadvantages :

• The wide range of parameters which affect the eddycurrent responses means

that the signal from a desired material characteristic,

e.g. a crack, can be

masked by an unwanted parameter, e.g. hardness

change. Careful selection

of probe and electronics will be needed in some

applications.

• Generally tests restricted to surface breakingconditions and slightly subsurface

b.Ultrasonic testing:

This technique is used for the detection of 

internal and surface (particularly distant Surface ) defects in

sound conducting materials. The principle is in some

respects similar to echo sounding

8/2/2019 Nondestructive Testing and Its Day4

http://slidepdf.com/reader/full/nondestructive-testing-and-its-day4 3/3

Advantages

• Thickness and lengths up to 30 ft can be tested. 

• Position, size and type of defect can be determined. 

• Instant test results 

Disadvantages:

• No permanent record available unless one of themore sophisticated test

results and data collection systems is used.

• The operator can decide whether the test piece isdefective or not whilst the

test is in progress.

c.Radiography:

This technique is suitable for the detection of internaldefects in ferrous and nonferrous

metals and other materials.

Advantages:

• Information is presented pictorially. 

• A permanent record is provided which may be viewedat a time and place

distant from the test.

• Useful for thin sections. 

• Sensitivity declared on each film. 

• Suitable for any material 

Disadvantage:

• Generally an inability to cope with thick sections. 

• Possible health hazard. 

• Need to direct the beam accurately for two-

dimensional defects.

• Film processing and viewing facilities are necessary,as is an exposure

compound.

• Not suitable for automation, unless the systemincorporates fluoroscopy with

an image intensifier or other electronic aids

• Not suitable for surface defects. 

• No indication of depth of a defect below the surface 

References:

[1] wikipedia

[2] http://www.insightndt.com/papers/index.html