c@~~H~ 1"/THf-'ft5()16IJ48LLrro~..Restri ted Circulation I r

REPORT No: NML/MST/IAF/1.13/66/2005.

September, 2005

~

FAILURE INVESTIGATION OF ARK-19 SENSE ANTENNA OF

MIG-29 AIRCRAFTKS-905.

Sponsored by

223 SquadronAir Force

C/O 56 APO

Ii

~~,,~

Materials Science & Technology Division

National Metallurgical Laboratory

(Council of Scientific and Industrial Research)

Jamshedpur - 831007

rr-!'~'I "'\" --. tit 'I~ '\. \ -. .

i 1':0~ l!\)~ 1:Jf).[I V' .

L D~H; .~ cJ'?f.' ". I'- -.-

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILURE INVESTIGATION OF ARK-19 SENSE ANTENNA OFMIG-29 AIRCRAFT KS-905

Report No.: NML/MST/IAF/1.13/66/2005. September 2005. NATIONAL METALLURGICAL LABORATORY(Council of Scientific & Industrial Research)

JAMSHEDPUR

PROJECT COMPLETION REPORT

Project Title: FAILUREINVESTIGATIONOFARK-19 Project No.: TH p-"t ()D 9(,SENSEANTENNAOF MIG-29 AIRCRAFTKS-905.

Report No.: NML/MST/IAF/1.13/66/2005.

Date of Project Initiation: 02.09.2005

Date of Completion: 28.09.2005

Project Team Members: Class:Dr. G. Das (PL) Public document (Free/Priced)Dr. S.R.Singh (Co-PL) Restricted circulation (X)Mr. Swapan Das Only to client

Secret

Customer / Client's name and address: Classification:

Wg. Cdr. R. BhardwajIn-house

SEa Grant-in-aid

For CO Sponsored (X)

223 Sqn, AF ConsultancyC/O 56 APO Collaborative

Date of Report : 28.09.2005

Area: Material Characterisation. Specify Type:

Sub Area: Failure analysisOngoing Area: (X)New Area Initiated:

Key Words: Sense antenna, aluminium alloy, surface anodising, fatigue failure, beach marks, fatiguestriations, foreign particle impact.

Abstract: The Sense Antenna is made of heat resistant duralumin closely similar to alloy AA 2618. Themicrostructural investigation revealed that its strength is derived from distribution of fineprecipitates of CuMgAh and dispersed particles of Al9FeNi phase which resist coalescence athigher operating temperature up to 300°C. Moreover, the measured hardness of 129 HB isconsistent with the observed microstructure as well as the hardness of the alloy AA 2618. Thelongitudinal surface of the antenna is hardened/protected by anodizing process. The weathering ofthe anodic coating involves uniform erosion of coating by wind-bone solid particles. The erosionmanifested by longitudinal abrasion marks do not seem to breach the protective anodizing coating.However, the non-gliding impacts of larger particles have been observed on the surface. The crackinitiation, leading to fracture, is found to be due to one such impact. Embedded silicon containingforeign particles have been observed near the impact site. The transverse fracture surface is flatand decorated with concentric beach marks centered around a crack initiation site. Fractographicexamination revealed fatigue striations throughout the fatigue zone which extended up to 90% ofthe fracture surface while rest of the fracture surface is separated by overload induced ductiledimple rupture. The crack initiation site on the longitudinal surface is imprinted with a dentdeformation. All these observation indicated that the fracture is due to fatigue and the fatiguecrack is initiated by impact of air borne particle of size larger than 1 mIll, on its surface.

Details of IPRs (PI tick): NA If no IPR taken, reasons: NAPatentCopyrightTrade Marks

Report Issuance Authority: Dr. S. R. Singh Signature: r<<;'.R- .

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILURE INVESTIGATION OF ARK-19 SENSE ANTENNA OF MIG-29 AIRCRAFT KS-905

Report No.: NML/MST/IAF/1.13/66/2005. September 2005

BACKGROUND

There was a flying incident of Mig-29 aircraft KS-905 of 223 squadron at 8 FBSU on

6th July 2005. The incident involved fracturing of ARK-19 Sense Antenna (hereafter, it will

be mentioned as antenna) which is made of metallic material. As the technical investigation

by IAF remains inconclusive, therefore, one of the retrieved fracture pieces of the antenna

was brought to NML on 02/09/05, for detailed investigation to find out the root cause of the

failure. The investigation is assigned to NML vide letter No. 223S/S 51l/lIEng, dated 2ih

August 2005, from 223 Sqn, AF.

SCOPE OF WORK

Based on the information on incident scenario, it was decided to do the following.

1.

2.

3.

Visual examination, photography, macrophotography and dimensional measurements.

Fractographic analysis of fracture surfaces to find out the fracture mode/mechanism.

4.

5.

Microstructural and hardness analysis to find out unusual features, if any.

EDS microanalysis of material.

SEM surface studies of the longitudinal surface of the antenna to find out mechanism

6.

of surface degradation/damage.

To find out the root cause of failure.

EXPERIMENTAL RESULTS

1. Visual examination, photography, macro photography and dimensional

measurements:

The photograph of fractured piece consisting of assembled cut pieces of sense antenna

is shown in Fig. 1a. It has failed at a height of 36.79 mm at thicker edge and 54 mm at thinner

edge from the root (Fig.la). It is aerodynamically designed with leading (thin) and trailing

(thick) edges. The fracture surface has maximum width of 14 mm and the length between

leading & trailing edges is 45 mm (Fig. lc). The fracture occurred in transverse section of the

antenna and the fracture surface is flat. The longitudinal surface has smooth shiny finish. Few

dark grooves on the longitudinal surface of the antenna (marked on the surface of the Figs.

Ia,b) have been observed, that may be formed due to gliding impact of wind-borne particles.

One of the grooves near to the fracture initiation point (marked in the Fig. 1d) is very

prominent. Probably the fracture initiated from the mechanically damaged surface region and

further crack propagation on fracture plane occurred due to fatigue. The macroscopic view of

2

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILURE INVESTIGATION OF ARK-19 SENSE ANTENNA OFMIG-29 AIRCRAFT KS-905

Report No.: NML/MST/IAF/1.13/66/2005. September 2005

fracture surface (Figs. l(c & d) clearly reveals the .signature of the fatigue failure, i.e.,

radiating marks at crack initiation site, concentric beach marks covering most of the fracture

surface and dull fast fracture zone at the opposite end of the crack initiation site. These

manifestations of fatigue failure have to be further substantiated by SEM fractographic

analysis. The beach marked fatigue zone covers nearly 90% of fracture surface. While rest of

the dull region is overload induced fast fracture zone. Therefore, material seems to have

sufficient strength and toughness.

2. Fractographic analysis of fracture surfaces to find out the fracture

mode/mechanism.

SEM fractographs of the fracture surface are shown in the Figs. 2(a & b). Low

magnification SEM fractograph (Fig. 2a) shows beach marks superimposed on transgranular

fracture surface whereas fatigue striations are observed in between beach marks at higher

magnification, shown in the Fig. 2b. It has been noticed that the spacing of fatigue striations

are not uniform throughout the fracture surface, indicating that the cyclic stress imposed on

the antenna is of irregular nature. The irregular cyclic stress may be arised due to random

nature of atmospheric wind presslire. The fatigue fracture initiation site (marked by arrow) is

shown in the Fig. 3a. This is more clearly visible in macrophotographs, shown in Figs. ~(c &

d). These observations clearly indicate that the fracture took place due to fatigue mechanism.

No traces of corrosive agents are found. Therefore, the possibilities of stress corrosion

cracking and corrosion fatigue are ruled out.

Longitudinal surface of the fractured end is also examined in SEM to reveal the

origin/nature of fatigue crack initiation site. A low magnification SEM surface micrograph

(Fig. 3b) shows impact induced cracked and deformed zone at the crack initiation site. The

length of the cracked zone is about 1 mm. This might have been induced by impact of air-

borne foreign particles of size larger than 1 mm. Moreover, abrasive wear tracks oriented

along longitudinal direction (along length of the antenna) have also been observed to form

because of abrasion by finer air-borne particles. The abrasion do not breached the surface

protective anodized layer of the antenna. A higher magnification surface micrograph (Fig. 3c)

shows impact induced flattened region at the intersection edge of longitudinal surface and

fracture surface. Few Si containing embedded particles (bright contrast) have also been

observed in the deformed zone. All the observations clearly indicated that the fatigue crack is

3

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILURE INVESTIGATION OF ARK-19 SENSE ANTENNA OFMIG-29 AIRCRAFT KS-905

Report No.: NML/MST/IAF/1.13/66/2005. September 2005

initiated by the impact of air-borne foreign partic1e~. The impact site appeared as dark

patches/spots in the micrographs (Fig. 1).

J - ,l

_..-[!)

'\..,

~ . ~

1 ~J4" OCt'l :) I !,- t.,..ji~ '~'. ""

'1.1 ~Ii

J,. 'w

". .. .. ~j~.

'. ", . .!:.t. " ,.,... . ~:;.,. ".

.\. ". ",.. ~ ,",\. 111,*,. ::" ,'t. ,., ';\.

""".,' , '".'.i'. (,\,'t, \~'r '. .~~~~.. ., . .\>

"'.

' \. ". \ ''.

..

..

.'

*,,\11(

.'t. ~, h,..'" . '. ~ , "i~ 't'. ...-.f,'".

. ~ 1 'ft"'t if '.(Y, J' l.I

1 't \.'" . 1. t. . '.!t' , "'\h '," ~'~.., "l ,.

...JiL. ..d['Ii".

,~'iC

t

;..:!.t . I

tor'L... "1 . "t ~

Figure 1: (a) Assembled cut pieces of the broken sense antenna, (b) side view of the fractured

portion, (c) macrograph of the fracture surface showing concentric beach marks,

and (d) crack initiation site (marked by arrow).

4

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILURE INVESTIGATIONOF ARK-19 SENSEANTENNAOFMIG-29 AIRCRAFTKS-905

Report No.: NML/MST/IAF/1.13/66/2005. September 2005

Figure 2: SEM fractographs of the fractured piece showing the (a) lower magnification view

of beach marks, and (b) fatigue striations confirming the fatigue failure of the sense

antenna.

5

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILURE INVESTIGATION OF ARK-19 SENSE ANTENNA OF MIG-29 AIRCRAFT KS-905

Report No.: NML/MST/IAF/1.13/6612005. September 2005

Figure 3: (a) Low magnification SEM fractograph showing the fatigue crack initiation site

marked by arrow, (b) dent marks near the fracture initiation point and (c) bright

embedded particles near impact site.

6

~-~

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILURE INVESTIGATIONOF ARK-19 SENSEANTENNAOF MIG-29 AIRCRAFTKS-905

Report No.: NML/MST/IAF/1.13/66/2005. September 2005

Figure 4(a & b): SEM micrographs showing the coarse elongated particles and fineprecipitates.

3. Microstructural Studies, EDS Microanalysis & Hardness Evaluation:

The transverse metallography section is prepared and etched in 0.5% HF solution to

reveal the microstructural constituents in the alloy. The lower and higher magnification SEM

micrographs are shown in Figs. 4a & b respectively. It shows dispersion of coarse elongated

particles and fine precipitates. EDS microanalysis of these phases indicated that they are

A19FeNi(Fig. 5a) and CuMgAh (Fig. 5b) respectively. The EDS microanalysis from the bulk

alloy is shown in Fig. 6. The quantified chemical analyses of all the three EDS spectra are

presented in Table 1-3. The bulk composition is closely similar to heat resistant dura1umin

(aluminium alloy) AA 2618. No unusual microstructural features have been detected. The

measured Brinne1 hardness (BHN) of the material is 129 HB which is above the required

minimum of 115 HB for the alloy AA 2168 in T61 temper condition. Therefore, the material

has desired microstructure and mechanical properties.

7

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILUREINVESTIGATIONOFARK-19 SENSEANfENNAOF MIG-29 AIRCRAFTKS-905

Report No.: NMLIMSTIIAF/l.13/66/2005. September 2005

Fe~ NIK..Fe~ NIK~ _keY

10

Figure 5a: EDS spectrum of elongated particles of Al9FeNi.

Table 1: Elemental composition of the phase AI9FeNi.

Cu~NIKa.

K ~!I.1q! keV10

8

AIK..I

5000

4000

IK"

3000

2000

1000NILNIL..

0 l:t I

0

2500Mg

2000

IK"1500

1000

500CullCuLoNILNI!-

0 u0

Figure 5b: EDS spectrum of finer precipitates of CuMgAl2 phase.

Table 2: Elemental composition of the phase CuMgAh.

Ka 35.5 1.2999 0.0102 0.0078 1.44 2.14 1.8602 0.00 0.00Ka 1506.7 8.4705 0.4432 0.3377 52.77 70.55 1.5626 0.00 0.00Ka 11.2 0.7305 0.0035 0.0027 0.49 0.63 1.8390 0.00 0.00Ka 102.8 2.2126 0.2544 0.1938 20.53 12.61 1.0593 0.00 0.00Ka 89.8 2.0684 0.2888 0.2200 24.77 14.06 1.1257 0.00 0.00

1.0000 0.7620 100.00 100.00 0.00 0.00

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILURE INVESTIGATIONOF ARK-19 SENSEANTENNAOF MIG-29 AIRCRAFTKS-905

Report No.: NML/MST/IAF/1.13/66J2005. September 2005

1000

~

AIKa

Mg

iKa

Cul~CulaNil ~Nil a

Fel~Fela

Til ~Til a keY

CONCLUSIONS

The Sense Antenna is made of heat resistant dura1umin closely similar to alloy AA

2618. The microstructural investigation revealed that its strength is derived from

distribution of fine precipitates of CuMgAlz and dispersed particles of A19FeNi

phase which resist coalescence at higher operating temperature up to 300°C.

Moreover, the measured hardness of 129 HB is consistent with the observed

microstructure as well as the hardness of the alloy AA 2618.

1.

9

Figure 6: EDS spectrum of the bulk material.

Table 3: Elemental composition of the bulk alloy.u -- .

29.8 0.5463 0.0211 0.0189 2.08 2.40 1.1004 0.00 0.001246.6 3.5308 0.9029 0.8085 89.79 93.63 1.1110 0.00 0.002.7 0.1629 0.0020 0.0018 0.36 0.36 1.9819 0.00 0.000.7 0.0808 0.0013 0.0012 0.14 0.08 1.1665 0.00 0.003.2 0.1792 0.0125 0.0112 1.27 0.64 1.1324 0.00 0.003.1 0.1761 0.0189 0.0169 1.92 0.92 1.1362 0.00 0.005.2 0.2285 0.0413 0.0370 4.44 1.97 1.2006 0.00 0.00

1.0000 .0.8955 100.00 100.00 0.00 0.00

NATIONAL METALLURGICAL LABORATORY, JAMSHEDPURFAILURE INVESTIGATIONOF ARK-19 SENSEANTENNAOFMIG-29 AIRCRAFTKS-905

Report No.: NML/MST/IAF/1.13/66/2005. September 2005

2. The longitudinal surface of the antenna is hardened/protected by anodizing process.

The weathering of the anodic coating involves uniform erosion of coating by wind-

bone solid particles. The erosion manifested by longitudinal abrasion marks do not

seem to breach the protective anodizing coating. However, the non-gliding impacts~-

of larger particles have been observed on the surface. The crack initiation, leading

to fracture, is found to be due to one such impact. Embedded silicon containing

foreign particles have been observed near the impact site.

3. The transverse ftacture surface is flat and decorated with concentric beach marks

centered around a crack initiation site. Fractographic examination revealed fatigue

striations throughout the fatigue zone which extended up to 90% of the fracture

surface while rest of the ftacture surface is separated by overload induced ductile

dimple rupture. The crack initiation site on the longitudinal surface is imprinted

with a dent deformation. All these observation indicated that the ftacture is due to

fatigue and the fatigue crack is initiated by impact of air borne particle of size

larger than 1 mm, on its surface.

RECOMMENDATIONS

A ftequent inspection of sense antenna for the presence of dark spots/patches is required.

If it is observed, the surface has to be refurbished to avoid recurrence of such type of

failure.

10

G:-,1"-'\ r->."-;:---:-," "~' \ - I

. " ,~t)()~ L(1) I

; ~--_.' - .?-~S-__J