BS 131-5-1965 Notched bar tests - Determination of crystallinity《缺口棒试验 第5部分 结晶度的测定》.pdf

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1、BRITISH STANDARD CONFIRMED NOVEMBER1990 BS 131-5: 1965 Methods for Notched bar tests Part 5: Determination of crystallinity UDC 620.178.746BS131-5:1965 This British Standard, having been approved by the MechanicalEngineering IndustryStandards Committeeand endorsed by theChairman of the EngineeringDi

2、visional Council,was published undertheauthorityof the GeneralCouncil on 26 February1965 BSI 08-1999 First published August 1920 First revision August 1933 Part 5 of second revision February1965 The following BSI references relate to the work on this standard: Committee references MEE/37, MEE/37/8 D

3、raft for comment D64/4911 ISBN 0 580 00801 0 Co-operating organizations The Mechanical Engineering Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizatio

4、ns: The Government departments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Associated Offices Technical Committee* Institute of

5、Petroleum Association of Consulting Engineers Institution of Civil Engineers Association of Mining Electrical and Institution of Gas Engineers Mechanical Engineers Institution of Heating and Ventilating British Chemical Plant Manufacturers Engineers Association Institution of Mechanical Engineers* B

6、ritish Compressed Air Society Institution of Mechanical Engineers British Electrical and Allied Manufacturers (Automobile Division) Association* Institution of Production Engineers* British Gear Manufacturers Association Locomotive and Allied Manufacturers British Internal Combustion Engine Associat

7、ion of Great Britain Manufacturers Association London Transport Board British Iron and Steel Federation* Machine Tool Trades Association British Mechanical Engineering Federation Ministry of Defence, Army Department* British Railways Board Ministry of Defence, Navy Department* Crown Agents for Overs

8、ea Governments and Ministry of Labour (H.M. Factory Administrations Inspectorate) D.S.I.R. National Engineering Laboratory* Ministry of Power Electricity Council, The Generating Board Ministry of Public Building and Works and the Area Boards in England and Wales Ministry of Transport Engineering Equ

9、ipment Users Association National Coal Board Gas Council National Physical Laboratory (D.S.I.R.)* High Commission of India Radio Industry Council Institute of Marine Engineers Royal Institute of British Architects Aluminium Federation Council of British Manufacturers of Association of British Chemic

10、al Petroleum Equipment Manufacturers D.S.I.R.Building Research Station British Cast Iron Research Association D.S.I.R. Forest Products Laboratory British Constructional Steelwork Association Institute of Welding British Iron and Steel Research Association Institution of Engineering Inspection Britis

11、h Non-ferrous Metals Federation Lloyds Register of Shipping British Non-ferrous Metals Research Ministry of Aviation Association Testing machine manufacturers and British Welding Research Association individual firms Copper Development Association Amendments issued since publication Amd. No. Date Co

12、mmentsBS131-5:1965 BSI 08-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Terminology 1 3 Recognition of crystallinity 1 4 Determination of crystallinity 1 5 Accuracy 1 6 Presentation of results 2 Figure 1 Typical examples of guide diagrams 3 Figure 2 Direc

13、t measurement of crystallinity 4BS131-5:1965 ii BSI 08-1999 Foreword This British Standard has been prepared as part of the second revision of BS131-1, BS131-2 and BS131-3 of the standard, dealing respectively with the Izod, Charpy V- and Charpy U- notch impact tests on metals, and Part4, covering t

14、he calibration of pendulum impact testing machines have already been published. The increasing use of percentage crystallinity as one of the criteria for assessing the notch ductility of steel by means of notched bar tests has prompted the issue of this standard, which assumes that a broken Izod or

15、Charpy test piece, having a cross-section of10mm 8mm below the notch, is to be examined. The methods for estimating the percentage of crystalline fracture are, however, generally applicable to any area of fractured surface. When fracture does not occur by cleavage, brittle areas may occur as the res

16、ult of inter-crystalline fracture or “flat” fracturing. In such cases the distinction between the crystalline and fibrous areas may be less well defined, and expert interpretation may be required. For notched bars other than stated in Clause1, the methods of determination described in this standard

17、may also be applied provided that the same definition (seeClause2) is used and suitable reference diagrams or control test pieces are available. It is emphasized that, for the purposes of this standard, the definition of crystalline fracture is general and refers to that part of the fracture surface

18、 which has a bright sparkling appearance. The standard is not concerned with the interpretation or significance of crystallinity, which depends on the type of test, the material considered and the application. A British Standard does not purport to include all the necessary provisions of a contract.

19、 Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to4, an inside back cover and a

20、 back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS 131-5:1965 BSI 08-1999 1 1 Scope This British Standard describes methods for determining the percentage of crystallini

21、ty in the fractures of notched bar test pieces of carbon, carbon-manganese and low-alloy steel, with particular reference to test pieces of the forms specified in BS131 1) , BS131-1, BS131-2 and BS131-3. 2 Terminology When a notched bar test piece of a metal is broken by bending, the individual crys

22、tals may fracture either by cleavage or by shear, and both modes may occur in the same fracture. In cleavage, the crystals fracture on crystallographic planes, which appear as bright sparkling facets, giving the appearance known as “crystalline”. In the shear mode, the crystals elongate and deform,

23、producing a silky texture described as “fibrous”. The “percentage of crystallinity” is defined as the total area of the crystalline portions of the fractured test piece expressed as a percentage of the original cross-sectional area of the test piece below the notch. Example. For a Charpy test piece

24、in which the cross-sectional area below the notch is8mm 10mm,i.e.80mm 2 , if the total area of crystallinity were32mm 2 , the percentage of crystallinity would be percent. 3 Recognition of crystallinity The crystalline portions of the fractured surface can be distinguished visually by their bright,

25、sparkling appearance, particularly when viewed from several angles under a point source of light, or by parallel light. An ordinary light bulb is preferable to strip lighting, and a small, brilliant bulb in a parabolic reflector gives the best practical contrast. The fibrous areas are characterized

26、by a relatively dull or silky appearance. 4 Determination of crystallinity The percentage crystallinity shall, in general, be estimated by one of the following methods, but other methods agreed between the interested parties are not precluded. a) Direct visual estimation. In this method, the fractur

27、e of one half of the broken test piece is examined (seeClause3) and the percentage crystallinity is estimated either by comparison with guide diagrams of the type shown in Figure 1, or by reference to a set of control test pieces for which the percentages of crystallinity have been determined more a

28、ccurately. b) Direct measurement. In this method, the crystalline areas are measured, without magnification, by means of a scale marked in millimetres, or preferably using a card having an opening graduated in millimetres, as indicated in Figure 2. c) Measurement with magnification. In this method,

29、the fracture surface is viewed under low optical magnification (say 10) preferably by means of an optical projector or projection microscope. The crystalline area is traced on a piece of paper and the area estimated, for example, by one of the following procedures: i) by counting squares, if squared

30、 paper or a transparent graticule is used; ii) by means of a planimeter; iii) by weighing the paper representing the crystalline area on a suitable balance. Alternatively, the crystalline area is determined by the use of a graticule in the eye piece of an ordinary monocular or binocular low-powered

31、microscope. NOTEWhen there are several crystalline areas, the aggregate area is to be used in calculating the percentage. Small isolated cleavage facets may be ignored. 5 Accuracy For most purposes, an accuracy to 10percent crystallinity is adequate, and this can usually be achieved by an experience

32、d operator using the method described in Subclause4 a). 1) BS131, “Methods for notched bar tests”, Part1, “The Izod impact test on metals”, Part2, “Charpy V-notch impact test”, Part3,“Charpy U-notch impact test”. 32 80 -10040 = BS 131-5:1965 2 BSI 08-1999 When more accurate determinations are requir

33、ed, methods such as those described in Subclauses4 b) and4 c) should be used. It is desirable that when methods a or b are used occasional checks should be made by method c. 6 Presentation of results The results of determinations made in accordance with this standard shall be reported as “percentage

34、 crystalline” as defined by the following formula: The values obtained may be rounded to the nearest5per cent unless a specially high degree of accuracy is required and is warranted by the method of determination used. The method of determination (seeClause4) shall be indicated. If, for any reason,

35、it is required to report the results of determinations in terms of “percentage fibrous”, such results shall only be derived by subtracting the crystalline area from the original cross-sectional area,i.e. Percentage crystallinityCrystalline area Original cross-sectional area below the notch -100 = 10

36、0 1 Crystalline area Original cross-sectional area below the notch - per centBS 131-5:1965 BSI 08-1999 3 Figure 1 Typical examples of guide diagramsBS 131-5:1965 4 BSI 08-1999 Figure 2 Direct measurement of crystallinityBS131-5:1965 BSI 08-1999 British Standards The following are available on applic

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