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DNV-OS-B101 Metallic Materials |
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| Ch.2: Technical Provisions |
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| Sec.6: Testing Procedures |
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| B: Test Methods |
| Rm | = | tensile strength |
| Re | = | yield stress (yield point) |
| Rp | = | yield strength (proof stress) |
| Rt | = | yield strength (proof stress), total elongation |
| A | = | percentage elongation after fracture |
| Z | = | percentage reduction of area. |
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5 d and has the designation A5.If the material is a ferritic steel of low or medium strength and not cold worked, the elongation may also be measured on a non-proportional gauge length Lo after agreement. In that case the required elongation Ao is calculated from the following formula:
A5 = the
required elongation in % for test piece with gauge length
So = the cross-sectional area of the test piece in question
Lo = the gauge length in question
The elongation value is valid if the fracture occurs at least the following distance from the end marks of the gauge length:
| — | round test piece: 1.25 d |
| — | flat test piece: b + a |
The following symbols are used:
| d | = | diameter |
| a | = | thickness |
| b | = | width |
| Lo | = | gauge length |
| Lc | = | parallel test length |
| So | = | cross-section |
| R | = | transition radius |
| D | = | external tube diameter |
| t | = | plate thickness |
Fig. 1 Tensile test pieces.
Ch.2 Sec.6 B
107 The gauge length Lo may be rounded off to the nearest
5 mm, provided that the difference between this length and Lo is less than 10% of
Lc.
The parallel test length shall be parallel within acceptable
tolerances. Tolerances according to ISO 82-1974 will be accepted.
Ch.2 Sec.6 B
108 For plates, wide flats
and sections with thickness 3 mm or more, flat test pieces of full
product thickness according to alternatives A and B shall generally
be used. When the capacity of the available testing machine is insufficient
to allow the use of test piece of full thickness, this may be reduced
in thickness by machining one of the rolled surfaces. Alternatively,
for materials over 40 mm thickness, proportional round test piece according
to alternative C may be used. When round test piece is used it shall
be positioned with its axis at one-quarter of the thickness from
a rolled surface.
Alternative A, proportional flat test piece:
| a | = | t |
| b | = | 25 mm |
| Lo | = |
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| Lc | @ |
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| R | = | 25 mm |
Alternative B, non-proportional flat test piece:
| a | = | t |
| b | = | 25 mm |
| Lo | = | 200 mm |
| Lc | @ | 225 mm |
| R | = | 25 mm |
Alternative C, proportional round test piece:
| d | = | 10 mm to 20 mm, preferably 14 mm |
| Lo | = | 5d |
| Lc | ³ | Lo + d/2 |
| R | = | 10 mm |
| a | = | t |
| b | = | 12.5 mm |
| Lo | = | 50 mm |
| Lc | @ | 75 mm |
| R | = | 25 mm |
Fig. 2 Grey cast iron test piece.
Ch.2 Sec.6 B
114 For tubes, test piece
according to alternative A or B below shall be used.
Alternative A:
Full cross-section test pieces with plugged ends.
| Lo | = |
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| Lc | @ | Lo + D |
Lc is the distance between the grips or the plugs, whichever is the smallest.
Alternative B:
Strip
| a | = | wall thickness of the tube |
| b | = | 12 mm |
| Lo | = |
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| Lc | @ | Lo + 2 b |
Fig. 3 Bend test piece
Ch.2 Sec.6 B
202 For plates, structural
sections and sheets, test piece with the following dimensions shall
be used:
a = as rolled thickness t of material
b = 30 mm
If the as rolled thickness t is greater than 25 mm, it may
be reduced to 25 mm by machining on the compression side of the bend
test piece.
Ch.2 Sec.6 B
203 For forgings, castings
and semi-finished products, test piece with the following dimensions
shall be used:
a = 20 mm
b = 25 mm
The point of impact of the hammer shall be in the centre line of the notch. The scale of the machine shall be calibrated to an accuracy of +0.5% of the machine's maximum striking energy. Impact test machines with a striking energy of less than 290 J are acceptable. In such cases, KV shall be supplemented with an index giving the striking energy.
For example, KV145 indicates that a striking energy of 145
J has been used.
Ch.2 Sec.6 B
304 Samples may be flame-cut
but the notch shall not be closer to a flame-cut edge than 25 mm.
The notch shall be made in a single cut by a special milling cutter.
The cutter shall be kept sharp so that the shape of the notch is
correct and cold working at the base is avoided as far as possible.
The cutter shall be systematically checked at intervals not exceeding
100 test pieces.
Ch.2 Sec.6 B
305 Dimensions and tolerances
for Charpy V-notch test pieces shall be as given in Table B1.
Ch.2 Sec.6 B
| Table B1 Charpy V-notch test pieces. | ||
| Dimensions | Nominal | Tolerances |
| Length | 55 mm | 0.60 mm |
| Width - standard test piece - subsize test piece - subsize test piece | 10 mm 7.5 mm 5 mm | ±?0.11 mm ±?0.11 mm ±?0.06 mm |
| Thickness | 10 mm | ±?0.06 mm |
| Angle of notch | 45° | ±?2° |
| Depth below notch | 8 mm | ±?0.05 mm |
| Root radius | 0.25 mm | ±?0.025 mm |
| Distance of notch from ends of test piece | 27.5 mm | ±?0.42 mm |
| Angle between plane of symmetry of notch and longitudinal axis of test piece | 90° | ±?2° |
Test temperature shall be stated in the certificate.
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
The required temperature tolerance is usually obtainable by immersing
the test piece for at least 2 minutes in an agitated liquid bath
having the specified test temperature, and have the test piece broken
within 5 seconds after withdrawal from the bath.
Fig. 4 Charpy V-notch test piece
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