NATIONAL BUREAU OF STANDARDS REPORT

10 017

Examination of

M513/M514 FUSE SLEEVES

To

Harry Diamond Laboratories

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT

8720641

NBS REPORT

10 017

Examination of

M513/M514 FUSE SLEEVES

By

G. E. Hicho

and

L . C. Sm i th Engineering Metallurgy Section

Metallurgy Division

To

Harry Diamond Laboratories

IMPORTANT NOTICE NATIONAL BUREAU OF S

for use within the Government

and review. For this reason, t whole or in part, is not auth Bureau of Standards, Washing

the Report has been specitical

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

ress accounting documents intended

is subjected to additional evaluation

re listing of this Report, either in the Office of the Director, National

, by the Government agency for which

copies for its own use.

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

U. S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, D. C. 202 34

Exami nat i on of

M5 1 3/M5 1 4 FUSE SLEEVES

Submi t ted by

Harry Diamond Laboratories

NBS Project 872064

1

HDL Project No. 76779

By

G . E . Hi cho

and

L . C . Smith

Division 312.01

Reference : (a) HDL Work Order, HDL Project No. 76779-

Ma ter i a 1 : A total of 102 fuse sleeves fabricated from 2014-T6 aluminum

alloy were submitted under reference (a) for examination. The fuse

sleeves have a semi -per forat i on located in the main length of the fuse

sleeve. Figure 1 shows three types of semi -per forat i ons that were

examined, ZW, N, and AHP. The fuse sleeve with a semi -perf orat i on marked NB was not photographed in the as received condition, however

a longitudinal view of the semi -perforat i on will be shown later. The

marks ZW, N, AHP, and NB are manufacturers' designations for the sleeve.

Some of the fuse sleeves had been fired and others had not. Fuse sleeves

numbered 63 to 89 were reported by HDL investigators, to have cracks

present. A list of the material submitted for examination is shown in

table 1

.

Purpose : The initial purpose of the investigation was to determine

whether there are cracks in the vicinity of the semi -per forat i on in fuse

sleeves 1 to 32. However, additional fuse sleeves were submitted

subsequently, 33 to 101, and the purpose of this part of the investigation

was to pull these samples in tension until breaking occurred. Among these

new samples 33 to 101, there were 47 samples, 43 to 89 that had been fired,

and among these 47 there were 27 samples, 63 to 89 , that had cracks

observed in them by HDL investigators. The tensile tests were conducted to

determine the effect of prior firing and an existing crack in the semi

perforation, on the breaking load of the fuse sleeve.

- 2 -

Hardness : Vickers (10 Kg load) hardness determinations were obtained

on fuse sleeves 24 to 32. These determinations and their converted

values of Rockwell B, are given in table 2. The hardness tests reveal

the fuse sleeves to be within the hardness limits for a 2014-Tb

aluminum alloy. The hardness limits were obtained from the Metals

Handbook, volume 1, Properties and Selection of Metals, 19^1.

Meta 1 lographi c Examination : Fuse sleeves 24 to 32 were given a metallographic examination. The sleeves were cut to reveal sections through

the semi -per forat i ons . Cracks, as indicated by the arrows in figures

2 and 3> were observed on the underside of the semi -perforat i ons . In figure 3> the crack appears to have opened more after firing. The fuse

sleeves were then sectioned longitudinally through the center of the

semi -per forat i on . Photomicrographs of the sectioned semi -per f orat i ons

are shown in figures 4 to 8. In figure 4, cracks as indicated by arrows (A), were observed on the underside of the semi -perforat ions in

both the fired and unfired conditions. In figures 5 an d 6, cracks,

as indicated by arrow (A), were observed on the underside of the fuse

sleeves where a sharp radius is present. However, in figure J, the more

generous radii as shown by arrows (A) and (B) in the type ZW semi

perforation appear to have been produced by the manuf acturer

s

1 processing.

Cracks were not found in this fuse sleeve.

Figure 8 is a photomicrograph of type ZW which had been pulled in

tension and then longitudinally sectioned. No cracks were observed,

however HDL investigators are reported to have observed cracks in this

particular fuse sleeve. It is possible that a prior existing crack may

have initiated the main fracture and hence would no longer be visible.

In the meta 1 1 ographi c examination of fuse sleeves 24,25,26, and 27

(AHP's) and 32 (NB), cracks were observed, figures 5 and 6, only at the

sharp radii on the underside of the semi -per forat i ons . However, in the

fuse sleeves, 28 and 29 (N's), which were meta 1 lographi ca 1

1 y examined,

figure 4, the sharp radii existed at the top of the semi -per fora t i on

.

The areas of sharp radii in type N were crack free, but cracks were observed on the underside of the semi -per forat i on on the smooth radii

indicated by arrows (A) in figure 4.

In figure 1, lb of 33 fuse sleeves of type N fracture during tension

testing occurred through the area marked by arrow (B), whereas in the

other 17 N's fracture occurred at the position indicated by arrow (A).

The failure at these two different areas indicated by arrows (B) and (A j in figure 1, could be attributed to the fact that underside of the semi

perforation, figure 4, did not have as sharp a radii as the top of the

semi -per forat i ons . The radii that existed at the top of N, figure 4, were

apparently equal. Therefore, if cracks were present on the underside

of the semi -perforat i on type N, the fracture would occur through the

-3 -

sharp radius adjacent to the larger of the pre-existing cracks. In fuse sleeves type AHP and NB, which were tested in tension, fracture

occurred only through the area indicated by the arrow (A) figures I, 5 and 6. This area of fracture initiation has sharp radii and

apparently had initial cracks present such as those shown in figures

5 and b, by arrow (A). The presence of a sharp radius and a crack are stress concentrators, and during tensile tests, failure would tend to occur through this area of the semi -perforat ion . Due to these stress

concentrators, the breaking loads obtained on types AHP, NB, and N should be lower than those of a fuse sleeve which did not have a sharp

radius and a crack present, such as in type ZW, figure 7-

Tens i I e Tests : Tensile tests were performed on fuse sleeves 33 to 101.

A fixture supplied by HDL was used in the test. The fuse sleeve was screwed into the fixture and a rod was then screwed into the fuse sleeve.

A tensile testing machine then applied a load to the rod which in turn

applied a pulling load to the fuse sleeve, thereby causing failure of the

sleeve. Because of the high breaking loads, the fuse sleeves were tested

at the Engineering Mechanics Section, NBS. The deflection rate applied to

all fuse sleeves tensile tested was approximately 0.05 inch per minute.

ASTM Specification B22 1 -68 for extrusions of 2014-T6 aluminum alioy, with

a wall thickness up to 0.499 inch thick, require a minimum tensile strength

of 60,000 psi. This corresponds in the fuse sleeves to a minimum breaking

load of approximately 26,700 pounds. The ASTM Specification B22 1 -68 for

elongation of a 2014-T6 extruded aluminum alloy, with a wall thickness of

up to .499 inch, requires a minimum elongation in 2 inches of 7 per cent.

The elongations for the fuse sleeves tensile tested in our program were not

calculated since the semi -per forat ion acts as a stress concentrator,

hence a true value of the elongation could not be determined. In table 3

the extension of a 2 inch gage length of the samples tensile tested is

reported. The data indicates the fuse sleeves with the semi -per forat i on mark of ZW have on the average a higher increase in a 2-inch length

than the other samples tensile tested.

The results of the tensile tests indicate the breaking loads of all

the samples tested to be above the minimum breaking load. The fuse

sleeves which were found to have cracks present, as observed by HDL, also were within ASTM specifications. Whether a fuse sleeve had or had not

been fired appeared to have no bearing on the breaking load, for all

these fuse sleeves had breaking loads above the specifications. The major

significance revealed in the tensile testing is that the fuse sleeves with

the manuf acturer 1 s designation ZW appear to have a higher breaking load

than the other types tested. This condition prevails whether the sample

ZW has or has not been fired.

Cone! us ions:

4 -

Cracks were found on the underside of some semi -perforat i ons in

both unfired and fired fuse sleeves. Firing appeared to have an effect

of opening the cracks somewhat. No cracks were found in sleeves

marked ZW arid it was ascertained that the semi -per forat i ons in these

fuses had more generous radii and hence had been deformed less severely

than the others. The design and manufacture of the semi -per forat i on

in type ZW is therefore considered superior to the others examined.

All specimens tested met requirements for hardness. Because of

the presence of a notch ( semi -perforat i on) , true tensile strength and

elongation values could not be obtained and compared with published data.

However, the breaking loads reported indicate that true tensile strengths were sufficiently high. All tensile fractures occurred through the

semi -perforat i ons , the exact location is assumed to be dependent on whether any existing cracks were present and the geometry of the semi - perforations. Firing did not appreciably effect the observed mechanical

proper ti es

.

Of all specimens tested in tension, type ZW had, on average,

slightly better properties. This is probably due to the less severe deformation and angles of the semi -per forat i on

.

USCOMM-NHS.DC
ccc
Table 1. Fuse Sleeve Designation and Examination Requested.

Samp 1

e

Number

Manufacturers

Des i gnat i on

F i red Not

F i red

Exami nation

Requested

1 ZW X Observe if cracks are in vicini

of semi -perforat i on

.

2 ZW X Macro-etch of semi -per f orat i on

.

3 ZW X Same as |l

.

4 ZW X

II II II

5 ZW X Macro-etch of semi -perforat i on

.

0 ZW X Same as # l . 7 ZW X

II II II 8 AHP X

II II II 9 AHP X

II M II 10 N X

II II II

1

1

AHP X Tensi le test

12 ZW X

II II 13 ZW X

II II 14 N X

II II 15 AHP X

II II 16 N X

II II 17 N X

II II 18 N X

II II 19 ZW X

II II 20 ZW X

II II 2 1 AHP X

II II 22 AHP X

II II 23 None,simi lar to NB X

II II 24 AHP X Meta 1 lographi c examination of

perforation, also hardness

measurements

.

2 5 AHP X Same as #24

26 AHP X

II II II 27 AHP X

II II II 28 N X

II II II 20 N X

II II II 30 ZW X

II II II 31 ZW X

II II II 32 NB X

II II II 33 N X Tensi le test

37 N X

II II 35 N X

II II 3o N X

II II 37 N X

II II 38 N X

II II 39 N X

II II 40 N X

II II 41 N X

II II 42 N X

II II 4 3 ZW X

II II 44 ZW X

II II 75 ZW X

II II
r._

L

[

:

—
Table 1 . Conti nued

Sample Manuf acturers

Number Des i gnat i on

46 zw

47 zw

48 zw

49 zw

50 zw

51 zw

54 zw

53 AHP

54 AHP

55 AHP

5b AHP

57 AHP

58 AHP

59 AHP

60 AHP

61 AHP

62 N 63 N 64 N 65 N 66 N 67 N 68 N 69 N 70 N 71 N 72 N 73 N 72 N 75 N 76 N 77 N 78 N 79 N 80 N 81 N 82 N 83 ZW

84 ZW

85 ZW

86 ZW

87 ZW

88 AHP

89 AHP

Fi red Not

Fi red

X Tensi le

X "

X "

X "

X

"

X

"

X

"

X

"

X "

X

"

X

"

X "

X "

X

"

X

"

X "

X

"

X

" X

"

X "

X

"

X "

X

"

X

"

X

"

X "

X "

X

"

X "

X "

X

"

X

"

X "

X "

X "

X "

X

"

X "

X "

X

X

" X

X

" X "

Exami nation

Requested

test

91

92

93

94

95

96

97

Q8

99

loo

101

102

Table 1 . Cont i nued

Manufacturers Fired Not

Des i gnat i on F i red

NB X NB X NB X NB X NB X NB X NB X NB X NB X NB X

N X

N X

N X

Exami nation

Requested

Tensi le test

Meta 1 lographi c examination

Table 2. Hardness of Fuse Sleeves

Samp 1

e

Number

Manuf acturers

Des i gnat i on

Fi red Not

Fi red

VHN Rb

24 AHP X 16

1

83.5

45 ahp X 172 87.0

26 AHP X 161 83.5

47 ahp X 175 87 .O

28 N X 155 82.0

49 N X 158 83.0

30 ZW X 163 84.0

31 zw X 161 83.5

32 NB X 161 83.5

* The ASM Committee on Properties of Aluminum Alloys, states

that for a 2014-T6 aluminum alloy, a BHN 135 (500 Kg load

10 mm ball)should be obtained as a hardness value. This

BHN 135 corresponds to a Rockwell B of 82.

Table 3- Tensile Results

Samp 1

e

Number

Breaki ng Load

( pounds

)

F i red

1 1 30,725

12 31,700

13 32,950

14 30,225

15 30,b00*

16 31 ,200

17 31,150 X 18 31,225* X

19 30,900 X 20 30,150 X 21 30,750 X 22 30,900 X

23 31,875 X 33 28, 100

37 30, 100

35 28,550

3o 30,650

37 29,000

38 28,000

39 28,700

4o 28,775

71 30,525

42 30,000

4r 32,150 X 44 33,700 X 45 32,700 X 46 31,350 X 77 32,300 X 48 32,900 X 79 31,800 X 50 32,000 X

51 32,350 X 52 32,250 X 53 30,900 X

57 30,650 X 55 30,725 X 50 29,575 X 57 29,850 X 58 30,250 X 59 30,850 X oO 30,400 X ol 29,700 X 62 30,700 X 63 31,175 X

Not

Fi red

Extension of

a 2" lenqth

Manuf acturers

Des i qnat i on

X (a) AHP

X (a) ZW

X (a) ZW

X (a) N X (a) AHP

X (a) N (a) N (a) N (a) ZW

(a) ZW

(a) AHP

(a) AHP

(a) NB

X 0.00 N X 0.01 N

X 0.02 N X 0.02 N

X 0.01 N X 0.00 N X 0.00 N X 0.02 N X 0.03 N X 0.00 N 0.02 ZW

0.04 ZW

0.02 ZW

0.01 ZW

0.00 ZW

0.03 ZW

0.04 ZW

0.03 ZW

0.02 ZW

0.02 ZW

0.01 AHP

0.00 AHP

0.02 AHP

0.01 AHP

0.02 AHP

0.00 AHP

0.01 AHP

0.01 AHP

0.01 AHP

0.02 N 0.04 N

* Yield load

.

(a) Not determined.
ri

r

)
65

66

67

68

09

70

71

72

73

7b

75

76

77

78

79

80

81

82

83

84

85

80

87

88

89

90

91

92

93

94

95

96

97

98

99

Table 3. Continued

Breaking Load

( pounds

)

Fi red Not

Fi red

31,050 X

29,550 X 31,425 X 30,700 X 31,350 X 28,475 X 30,050 X 29,350 X 28,950 X 29,750 X

31,000 X 30,500 X

31,400 X

29,700 X 31,600 X 29,750 X 29,500 X 28,650 X

28,650 X 33,200 X 32,000 X 31,150 X 31,600 X

32,975 X 30,900 X 30,500 X 28,025 X 29,050 X

29, 100 X

28,925 X 28,750 X 29,350 X 28,500 X

29,650 X 28,900 X

29,900 X 30,050 X 28,025 X

Extension of Manufacturers

a 2

11 length Des i gnat i on

0.03 N 0.01 N 0.02 N 0.03 N 0.05 N 0.00 N 0.01 N 0.03 N 0.00 N 0.03 N 0.03 N 0.02 N 0.06 N 0.04 N 0.04 N 0.00 N 0.03 N 0.04 N 0.02 N 0.02 ZW

0.02 ZW

0.04 ZW

0.02 ZW

0.01 ZW

0.01 AHP

0.01 AHP

0.00 NB

0.00 NB

0.00 NB

0.00 NB

0.00 NB

0.00 NB

0.00 NB

0.00 NB

0.00 NB

0.00 NB

0.02 N 0.02 N

Q_

3:<1

<uQ.'—

>-o

1/1 in

4- i—

0) 03

(U C JZ O hd)>

a) 3

<u M

to Q)Q.

>> cO 1 —

4J JZ — CT1 XI —

C l_ O

O d> -C XI D

<v> c — o

a)o -o

<D c

L. 03

1O *\ 03 Z

a) a) JZ CL

*-> >

c

i— "N

(1) 10

0) XI > XI

d> —

d) E

10 d) 31

d) *-< 10o c

3

cn

indicate

the

item,

the

semi

-perforat

i

on,

which

was

investigated

on

each

of

the

fuse

sleeves

submitted.

Arrow

(A)

indicates

the

area

through

which

53

fuse

sleeves,

type

AHP,

N

and

NB,

failed

during

tensile

testing.

Arrow

(B)

indicates

the

area

through

which

16

of

33

type

N

fuse

sleeves

failed

during

tensile

tests.
I:c
Figure 2. Photograph of underside of semi

perforation type AHP. Arrow

indicates crack location. Unetched,

X 20.

Figure

3*

Photographs

of

underside

of

semi

-per

forat i

on

of

type

N.

Photograph

on

left

is

of

the

unfired

condition,

on

the

right,

of

the

fired

condition.

Arrows

indicate

cracks.

Unetched,

X

20.
j5j||
Figure 4. Longitudinal sections of fuse sleeves type N,

not tensile tested. Photograph (l) i s of the

fired condition, and (2) of the unfired con- dition. Arrows (A) indicate location of cracks

observed on the underside of the fuse sleeves.

Arrows (B) and (C) are locations of sharp radius.

Sixteen type N fuse sleeves failed through area

(C) and seventeen failed through area (B) during

tensile tests. Etched, Keller's, X 12,
L
gure 5 . Longitudinal sections of fuse sleeve type AHP,

not tensile tested. Photograph (l) i s of the

fired condition, and (2) of the unfired con- dition. Arrow (A) indicates area through which

failure occurred during tensile tests, and area

of a crack and sharp radius. Etched, Keller's,

X 12.
-
Figure 6 . Longitudinal sections of unfired fuse sleeve

of type NB, not tensi le tested. Arrow (A)

indicates area through which failure occurred

during tensile test and area of a crack and a sharp radius. Etched, Keller's, X 12.

Figure 7. Longitudinal sections of fuse sleeve type ZW,

not tensile tested. Photograph (l) i s of the

fired condition and (2) of the unfired con- dition. Arrows (A) and (B) indicate areas of

smooth radius. Arrow (A) also indicates area through which fracture occurred during tensile

tests. Etched, Keller's, X 12.

Figure 8. Longitudinal section of fuse sleeve of type

ZW after the fuse sleeve was tensile tested.

Note absence of cracks on both the top and

underside of the semi -perforati on . Etched,

Keller's, X 12.