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Elektromagnetika

Kelas C

Muhammad Wisnu Cakrawiguna

11/318537/TK/38103

Ali!ation o" Magneti! #arti!le $nse!tion in the %ield o" the &o!omoti'e

$ndustr(

A)stra!t* The magnetic particle method is established since 80 years as a method for the prove of

surface cracks in ferromagnetic material. The MT method (MT = magnetic testing) is one of the most

simple and most sensitive methods in NT. !sing MT surface defects can be detected safely even alongcomple" geometries. The most important cause of a damage# the crack# the surface of a component is t$o

times $eaker than the inside. This leads us to the fact that the highest forces affect the $eakest regions of a

part. ue to this# surface crack detection once more sho$s its significance in mass production. %ince theMT results are al$ays pictorial the magnetic particle testing method is a integral NT method that

perfectly matches the sensory needs of the human inspector. ue to this and due to the fact that the process

of magneti&ation and spraying can be applied upon the $hole surface of the component in one go# the MT

method sho$s a very high potential to be fully automated and production line integrated. The follo$ing passages $ill sho$ e"amples from the locomotive industry that $ill give an idea ho$ magnetic testing

combined $ith machine vision and a self controlling structure turns into a fully automated and production

integrated NT method.

Ke(words' Nondestructive Testing# Magnetic article *nspection# +ocomotive *ndustry#

Machine ,ision

$ntrodu!tion

Material defects are un$anted

contaminants right from ra$ material tofurnished products due to inade-uate

process adopted during metallurgical

change manufacturing etc. Material

defects can be appeared in differentforms. s an e"ample the some defects

have to be mentioned here non metallicinclusions defects# manufacturers

defects# high surface decarburi&ation

defects# bad microstructure defects#

surface corrosion defects# mechanicaldamage defects# surface defect# *nternal

defects etc.

The represented e"amples don/thave to lead to the failure of the material

in every case. These are merelye"amined on the material surface andmaterial insides as $ell as of structure

anomalies# $hich differs from the

standard. efects play a crucial role in

influencing the various materials properties# and e"hibit comple" structure

on varying length scales from electronic

structure of the defect core (sub

nanometer and belo$) to elastic fields of

the continuum (micrometer and beyond).efects in materials may be

detected by various processes such as

Magnetic particle inspection# ray

radiography# 1amma radiography#!ltrasonic testing# 2lectrical method#

amping test# Nonmagnetic method of nondestructive testing# 3ptical

holography method and 4ardness test.

This study is limited to

surface5subsurface imperfection $hichis detected through magnetic particle

crack detection techni-ue each process is

re-uired visual inspection. %o it is$orking to discuss about visual

imperfection.,isual testing is probably themost important of all magnetic particle

crack detection tests. *t can often provide

valuable information about defects. The

visual inspection ho$ever should not beconfined only to the structure being

investigated. *t should also include



neighboring structures# the surrounding

environment and the climatic and

services condition. This test report helpsthe component authority to allo$ their

safe use in the installation. ue to time

constraints it $as decided to take uponly magnetic particle crack detection

testing of locomotive components. %o

this is an attempt to learn about themagnetic particle crack detection testing

of materials in general# but locomotive

gear components in particular.

1+ Magneti! testing o" dri'e sha"ts

3ne application from the field of

the sub suppliers of automotive parts is

the fully locomotive inspection of driveshafts. 2"ample# rive shafts are

cylindrical parts of a length of 600 mmto 70 mm and a diameter of 9: mm to

6; mm.

<ig. 9' rive shaft# length' 90 mm<igure 9 sho$s such a shaft that

is toothed and hardened at both ends.

Typical fla$s on this components arematerial a hardening defects. <igure;

sho$s a materials defect after

magneti&ation and spraying $ith M*

test ink under !, light. The system basically is designed as a $alking beam

that leads the parts into the single

stations of the inspection process. <igure6 sho$s the part entrance of the machine

that is designed as a slope on $hich the

parts are piled up in a ro$.

<ig.;' Material defect under !, light

<ig. 6' art entrance of the M* system

The $alking beam al$ays takesout the first part ofthe ro$ and transports

it into the magneti&ation and spraying

station. <igure > gives a vie$ on the$alking beam transport into the

direction of the magneti&ation station.<or themagneti&ation of the shafts acombination of current flo$ and

magnetic flu" method is used. 4ereby

the current flo$ indicates the transversal

and the magnetic flu" method indicatesthe longitudinal defects. bove the

magneti&ation station one can the

spraying device $ith its si" sprayingno&&les. The follo$ing station in

transport direction is the inspection

station. *n case of the drive shaftinspection system it is designed as a

clamping and turning device (<ig.). The

illumination is reali&ed by t$o !,

tubes. The camera station $hich islocated above the clamping device

(<ig.) consists out of eight ??

cameras.



<ig. >' @alking beam in transport

direction

<ig.' ?lamping and turning device in

inspection station

3ne of the eight cameras ismounted to a linear positioning system.

This enables the machine to adAust itself

to the different shaft length thatare processed in the system.

<ig. ' ?amera station

<ig. 7' rive shaft $ith material defectB1rey scale image of the MT indication

<ig. 8' rive shaft after image analysis

of the machine vision

The figures 7 and 8 sho$ thecomponent in a grey scale image taken

by the system before and after image

analysis. <or the image analysis of theshaft every camera is $orking along a

specific area of interest (3*). 3nly thefirst and the last camera is $orking $itht$o different areas of interest since they

picture parts of the shaft surface and the

toothed ends of the component. @hilethe splines of the shaft are inspected

only on transversal cracks# the rest of the

surface is tested on longitudinal and

transversal defects. The reason for thiscan easily be seen in <ig.7 and 8. ue to

the geometry and shape of the spline it is

impossible not to collect M* po$der inthe grooves during the MT process.

machine vision algorithm# like it $as

used at the time this system $as build#$ould al$ays classify such a indication

as a critical effect and mark the part as

bad. This $ould al$ays lead to a very

high number of reAected parts. solution



to prevent false reAection in this case

$ould be a kind of a peeling algorithm

that can distinguish bet$een a real crack and a false indication. %uch an algorithm

peels off the circumference of an obAect

$ith a one pi"el $idth. ue to the factthat a realcrack indication is much more

narro$ than the false indication of a

groove it is easy to see that a real crack $ould vanish after one or t$o goes

$hile the indication of the groove $ould

still remain. *n this $ay the automatic

decision $hether a indication is a crack or a false indication can be made very

easy and safe. The camera set up used in

this machine is fully synchroni&ed to

meet the customers cycle time needs.ppending to the inspection station the

$ork piece gets demagneti&ed. This process is carried out in a yoke the is

build in the same $ay as the yoke in the

magneti&ing station. fter demagneti&ation the components are

handed over to a$ashing machine.

<igure : sho$s the technical data of the

drive shaft testing system.

<ig.:' Technical data of the MT shaftsystem

<ig. 90' osition of the shafts inside thedrive section of a locomotive

<igure 90 sho$s $here the drive shafts

are mounted in the drive section of a

locomotive.

,+ Magneti! testing o" !rank sha"ts

<igure 99 sho$s a fullyautomated and production integrated

magnetic particle crank shaft testing

system. This type of system is in1ermany already used by t$o crank

shaft manufacturing companies.

<ig. 99' %ystem for automated magnetictesting of crank shafts

This system is based on a

magnetisation bench $ith moving coiland turning yokes. The magnetisation

method is a combination of current flo$

for longitudinal and coil magnetisationfor transversal cracks. uring the

magnetisation process# the test li-uid

$ill be applied by a sho$er that is

integrated into the moving coil. <igure9; sho$s the magneti&ation station of

the system. The crank shaft is inserted

into the pneumatic $ork piece holder viaa overhead conveyerthat loads the shaft

through the roof of the darkening booth

into the machine. The $ork piece holder

adAusts the crank shaft in bet$een theyokes that are designed as a clamping

station. fter the yokes closed# the $ork

piece holder $ill release the shaft. Theshaft is no$ only held in position by the

clamping force of the yoke. uring the

magnetisation the crank shaft $ill bemagnetised by the yokes and at the same



time by themoving coil $hich can be

seen on the left side of fig.9;. fter the

magnetisation process is carried out# thecoil moves back into its initial position

and the crack detection se-uence begins.

The crank shaft has to be turned toenable the machine vision system to

inspect it. ueto the fact that such a

shaft has got no symmetrical shape# thefully automated inspection by cameras is

not trivial. <or the magnetic particle

testing of finished crank shafts the

inspection of all machined surfaces arenecessary. <or a four cylinder crank

shaft# like sho$n in fig.9;# this means

that four Aournals and five main bearings

have to be inspected. lus severalfittings for counter$eights.

<ig. 9;' Magnetisation station $ith yokeand coil

3n crank shafts that are designed for a

higher number of pistons very often t$orelated Aournals are not separated but

combined to each other like sho$n in

figure 96.

<ig. 96' 90cylinder crank shaft (upper

image)# combined Aournals (arro$)BMaterial defect on crank shaftB MT

indication

+ooking on the geometry and shape of a

crank shaft it is easy to see that a

inspection using fi"ed cameras $ill notlead to proper inspection results. uring

one turn of the shaft the Aournals are

moving on a circular orbit around themain bearings.

<igure 9> sho$s such a set up in

principal.3ne can see that the obAect to be

inspected $ill constantly change its

position in vertical direction $ithin the

field of vie$ as $ell as its distance to thecamera it self.

<ig. 9>' iagramm of the orbit of a

Aournal

<ig. 9' iagramm of the camera positions that realise a constant field of

vie$

To realise constant boundaryconditions for the imaging of the

Aournals the cameras have to follo$ the

motion of the shaft. This makes ahori&ontal and a vertical motion

necessary like sho$n in figure 9. The

hori&ontal motion# that means the motion

that reali&es the stabilisation of the



distance bet$een camera and Aournal#

could theoretically be replaced by using

motori&ed &oom optics. Cut due to thefact that these kind of optics change their

transmittance in dependence of the focal

length this solution is not practicalcompared to the use of a linear a"is.The

variation in transmittanceleads to the

problem that t$o obAects# comparable insi&e and brightness# in different distances

to the camera $ill be displayed in

al$ays the same si&e but in different

brightness.This means that a $orkingmeasuring system based on a &oom optic

al$ays has to match its sensor sensitivity

in dependence to the focal length.

<ig. 9' ?amera station of the crank

shaft inspection system $ith 6d

positioning unit<igure 9 sho$s camera station

of the crank shaft MT system. *t ise-uipped $ith t$o cameras $ith 6 mm

optics. 2very imaging unit is mounted to

6d positioning system that consists of 6linear a"is each. *n this $ay al$ays t$o

Aournals can be inspected at once. The

illumination system is e-uipped $ith

t$o !,+2 sources on each side (<ig.9 yello$ arro$). The first automated

crank shaft system from year ;000 $ascarrying mercury lamps as illuminationsources (<ig. 97).

<ig. 97' *llumination system of a crank

shaft system $ith mercury lamps(yello$ arro$)

<ig. 98' Technical data of the system for

crank shaft testing

Anal(sis

The test specimen is adAusted in

the !niversal magnetic particle crack

detection or ortable magnetic particlecrack detection tester. +et us supply

alternating current through the test bench

$hich causes the generation of magneticfield and then the magnetic flu" at the

probe ends longitudinally. @hen



dielectric li-uid solution (of kerosene oil

and iron o"ide particle) is made to flo$

over the specimen# therefore the cracksare clearly visible and can be measured

$ith the help of measuring scale. To

measure the transverse cracks either of the follo$ing steps are used'

i+ dAust the specimen as done for

longitudinal cracks. No$# allo$ flo$ of direct current instead of alternating

current. %o# magnetic flu" generated is

perpendicular to the longitudinal a"is B

thus#transverse cracks are visible and can be measured.

ii+ ?ontinue to supply the alternating

current to the universal5potable

test bench and rotate the test specimen bet$een t$o prods by :0 D so that

longitudinal cracks in step (i) becomethe transverse cracks in step (ii) and the

transverse cracks in step (i) become the

longitudinal cracks in step (ii). 4ence#the transverse cracks can be detected and

measured.

Con!lusion

3n the basis of this study# the follo$ing

conclusions may be dra$n'

i+ ,isual techni-ue is useful to find outthe condition of sample and helpful to

get ready for future NT operation.

ii+ Magnetic particle crack detection candetect transverse as $ell as longitudinal

cracks $hich can be identified and

-uantified.

*t can be concluded that M?evaluation must be conducted on

manufactured e-uipment prior to use# so

that failure of e-uipment in stipulatedtime could be prevented. *t is also

suggested that condition of vital

components must be subAected to their condition monitoring at certain interval.

-E%E-E.CE

Cet& ?2 (9:8). rinciples of

Magnetic article Testing#merican %ociety for

Nondestructive Testing# . ;6>#

*%CN:780698;9>8#retrieved from

Ehttp'55en.$ikipedia.org5$iki5M

agneticarticleFinspectionE.le"ander T4T (9:8:). GNon

destructive Testing of Materials

(+e$# 4%# 2d.)# ?* %99;#

p. ;9.%ei H# 1oenka (;009). Nanda Millar

?o. Grototype development of

cage suspension 1ear and Test

rocedureI.<arley HM (;00;). NT ,il;#

Mc1ra$4ill.Mc1onnagle @H (9:8).

*nternational dvances in Non

destructive Testing 9;# 1ordonJ Creach#Ne$ Kork# pp. 997

9>.

?L*N3 NH (9:8>). G+aboratory

study of fla$ detection inconcrete by the pulseecho

methodI# *n situ Non

destructive Testing of Material(Malhotra# ,.M.# 2d.)# ?* %

8;# merican ?oncrete

*nstitute 7.!mesh %ingh# Mohan %ingh and M.

. %ingh. Gnalysis study on

surface and sub surface

imperfections throughmagnetic particle crack

detection for nonlinear

dynamic model of some miningcomponentsI

Thomas ,2TT2L+2*N.

Gpplication of Magneticarticle *nspection in the <ield

of the utomotive *ndustryI