1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 23228:2011Thermoplastics pipes forthe conveyance of fluids Determination of thestress-rupture resistance ofmoulding materials using plainstrain grooved tensile (PSGT)speci
2、mensBS ISO 23228:2011 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 23228:2011.The UK participation in its preparation was entrusted to TechnicalCommittee PRI/88/4, Test Methods - Plastic Piping.A list of organizations represented on this committee can beobta
3、ined on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 57523 5ICS 23.040.20Compliance with a British Standard cannot confer immunity fromlegal obligations.This B
4、ritish Standard was published under the authority of theStandards Policy and Strategy Committee on 31 October 2011.Amendments issued since publicationDate Text affectedBS ISO 23228:2011Thermoplastics pipes for the conveyance of fluids Determination of the stress-rupture resistance of moulding materi
5、als using plain strain grooved tensile (PSGT) specimensTubes en matires thermoplastiques pour le transport des fluides Dtermination de la rsistance la rupture sous contrainte des matriaux de moulage, au moyen dprouvettes de traction rainures dformation plane ISO 2011Reference numberISO 23228:2011(E)
6、First edition2011-10-01ISO23228INTERNATIONAL STANDARDBS ISO 23228:2011ISO 23228:2011(E)COPYRIGHT PROTECTED DOCUMENT ISO 2011All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including phot
7、ocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in Switzerlan
8、dii ISO 2011 All rights reservedBS ISO 23228:2011ISO 23228:2011(E)Contents PageForeword .ivIntroduction . v1 Scope 12 Normative references .13 Terms and definitions .14 Principle .25 Apparatus 25.1 Loading system .25.2 Constant temperature system .35.3 Timing device .35.4 Failure detection device 35
9、.5 Sample grips .35.6 Calibration and accuracy of the apparatus 36 Test specimen 46.1 Dimensions .46.2 Measurements 56.3 Specimen preparation 57 Conditioning .68 Procedure 69 Calculation 610 Test report .7Annex A (informative) Determination of specimen dimensions for the plane strain condition 8Bibl
10、iography .9 ISO 2011 All rights reserved iiiBS ISO 23228:2011ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical commit
11、tees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the In
12、ternational Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International S
13、tandards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the sub
14、ject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 23228 was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the transport of fluids, Subcommittee SC 5, General properties of pipes, fittings and valves of pla
15、stic materials and their accessories Test methods and basic specifications.ISO 23228:2011(E)iv ISO 2011 All rights reservedBS ISO 23228:2011IntroductionISO/TC 138 provides test methods for determining the resistance to internal pressure which are essential for assessing the properties and durability
16、 of thermoplastics piping system parts. These test methods constitute a basis for the determination of short-term and long-term strength characteristics. However, with regard to moulding materials for pipes and fittings, until the publication of this International Standard, no satisfactory test meth
17、od has existed in which the material can be exposed to stress conditions that mimic internally pressurized pipes.The method specified here has been demonstrated to replicate the stress conditions of internally pressurized end-capped pipes by the use of plaque specimen having a reduced section in the
18、 form of a groove positioned perpendicular to the uniaxial loading direction. This method is useful for evaluating the stress-rupture resistance of moulding materials and experimental resins being developed for pipes and fittings as well as for those pipes that are difficult to test, such as larger
19、diameter pipes.ISO 23228:2011(E) ISO 2011 All rights reserved vBS ISO 23228:2011BS ISO 23228:2011INTERNATIONAL STANDARD ISO 23228:2011(E)Thermoplastics pipes for the conveyance of fluids Determination of the stress-rupture resistance of moulding materials using plain strain grooved tensile (PSGT) sp
20、ecimens1 ScopeThis International Standard specifies a method for the determination of the time-to-failure of thermoplastics resins and compounds for piping and fitting applications by the use of a plane strain grooved tensile specimen in a stress-rupture test.The grooved tensile specimen produces a
21、biaxial state of stress on uni-axial loading, which is taken to be indicative of the stress conditions found in pressurized solid-wall plastics pipes. The ratio of the stress in the axial direction to the transverse direction approximates that for a pressurized end-capped solid-wall pipe specimen47.
22、It is intended that the data generated on these specimens be utilized to determine the stress-rupture (time to failure) resistance of moulding materials for pipes and fittings as well as experimental piping resins.This method is also applicable to stress-rupture evaluations of pipes which are diffic
23、ult to test, e.g. larger diameter pipes, including their batch release tests.This International Standard is not intended to replace the stress-rupture test of ISO 11672, which uses internally pressurized end-capped pipes.2 Normative referencesThe following referenced document is indispensable for th
24、e application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 3126, Plastics piping systems Plastics components Determination of dimensions3 Terms and definitionsFor t
25、he purposes of this International Standard, the following terms and definitions apply.3.1stress-rupture testtest at which a constant nominal stress is applied and maintained until specimen rupture (failure)3.2failure timetftime at which a specimen fails by gross yielding or by through thickness slow
26、 crack propagation on stress-rupture loadingNOTE The failure time is expressed in hours.3.3applied nominal stressnapplied stress calculated using the undeformed minimum groove cross-sectional areaNOTE The applied nominal stress is expressed in megapascals. ISO 2011 All rights reserved 1BS ISO 23228:
27、20113.4plane strain condition in the groovezero strain condition in the groove axis where there exists no change in displacement along the groove on load application perpendicular to the groove axisNOTE In PSGT specimens, the stress biaxiality is developed in the groove as a result of the plane stra
28、in condition in the groove. Plane strain condition also occurs in the end-capped pipe when internally pressurized.3.5long-term hydrostatic strengthLTHSquantity with the dimensions of stress, which represents the predicted mean hydrostatic hoop strength at a temperature, T, and failure time, tfNOTE T
29、he long-term hydrostatic strength is expressed in megapascals.3.6long-term strengthLTSquantity with the dimension of stress, which represents the predicted mean strength at a temperature, T, and failure time, tfNOTE 1 The long-term strength is expressed in megapascals.NOTE 2 Long-term strength LTSis
30、 similar to long-term hydrostatic strength LTHS; however, they differ in the mode of loading, tensile versus hydrostatic.4 PrincipleA plane strain grooved tensile (PSGT) specimen is made from a moulded flat plaque of finite width and length dimensions having reduced area (see Figures 1 and 2). The c
31、oncave grooves are made along the width of the specimen and perpendicular to the axis of the direction of uni-axial loading. The plane strain condition in the groove is induced by the deformation constraint in the groove. This is the result of the difference between the reduced thickness, eg, of the
32、 groove and unreduced thickness, e, of the test specimen, as illustrated in Figure 2.With the appropriate dimensions applied (see Table 1 and Figure 2) a plane strain condition, and hence biaxial stress state, is generated in the groove on uniaxial loading. After conditioning in the test medium, the
33、 specimen is subjected to a specified constant load for sustained time duration until the test specimen fails, at which point the stress and corresponding rupture time are recorded. In this manner, it can be tested in various controlled environments, and at specified constant temperatures, in order
34、to obtain the long-term strength capacity of moulding materials for pipes and fittings. Such a controlled environment can be accomplished by, but is not limited to, immersing the specimens in a controlled-temperature water bath or circulating-air oven.The PSGT stress-rupture data obtained from mould
35、ing materials, experimental piping resins and samples obtained from pipes and fittings can be extrapolated in accordance with a method such as that specified in ISO 90803for providing estimations on their long-term strength properties. For estimating the effect of extrusion processing on pipes, the
36、results from PSGT specimen can be compared with the results generated with pipes according to ISO 11672.5 Apparatus5.1 Loading systemAny device that is capable of continuously applying constant load on the specimen may be used. The device shall be capable of reaching the test load without exceeding
37、it and holding it to within 1 % of the applied load throughout duration of the test. A loading system that utilizes an electro-pneumatic device was found to be suitable. Other constant loading systems may also be used, such as those described in ISO 899-11. It is important to maintain the straight s
38、ample alignment with the load-train to avoid any bending and/or twisting of the specimen.ISO 23228:2011(E)2 ISO 2011 All rights reservedBS ISO 23228:2011Figure 1 PSGT specimens undergoing stress-rupture test5.2 Constant temperature systemA reservoir capable of maintaining a fluid at a uniform temper
39、ature and which ensures complete immersion of the test specimen shall be used. The construction material for the reservoir shall not affect the environment or vice versa. If evaporation affects the medium condition, a lid shall be part of the construction so as to prevent this phenomenon. If water o
40、r other liquid medium is used, agitation is permitted to stabilize the temperature throughout the reservoir. If an air or other gaseous environment is used, provision shall be made for adequate circulation. The temperature of the environment shall be controlled to maintain the specimens at (T 1,0) C
41、, where T is the specified test temperature, in case of a liquid bath and T+( )12C when an oven system is used. Control and measurement of the temperature in the test medium shall be done with a calibrated thermometer, thermocouple or thermistor to an accuracy of 0,1 C.5.3 Timing deviceA suitable ti
42、ming device that can monitor time accumulation shall be used. The accuracy of the measurement shall be better than 1 % of the elapsed time.5.4 Failure detection deviceAny device that can detect failure due to gross yielding of the sample or slow crack propagation through the groove thickness shall b
43、e utilized.5.5 Sample gripsBy means of an appropriate system, grips shall be installed at the ends of the specimen to allow transfer of the applied load to the specimen without causing slippage, damage or any other adverse effect on the test specimen during the test.5.6 Calibration and accuracy of t
44、he apparatusThe temperature and load control systems and the equipment for measuring temperature, load and time shall be capable of maintaining the values within the specified limits and shall be calibrated regularly to maintain the required accuracy.ISO 23228:2011(E) ISO 2011 All rights reserved 3B
45、S ISO 23228:20116 Test specimen6.1 DimensionsThe shape of the test specimen is shown in Figure 2. A concave groove is produced along the full width of the specimen on both sides. The opposing grooves shall be parallel and centred in the specimen within 0,1 mm. A PSGT specimen that has been used succ
46、essfully is shown in Figure 2. The critical dimensions of this specimen are shown in Table 1.KeyB groove height e unreduced thicknessegreduced thicknessH groove depth L specimen length r groove radiusW specimen widthy loading directionFigure 2 Schematic diagram indicating the dimensions of PSGT spec
47、imenISO 23228:2011(E)4 ISO 2011 All rights reservedBS ISO 23228:2011Table 1 Dimensions of PSGT specimenDimensions in millimetresVariable Dimension ToleranceWidtha, W40,0b0,1Groove radius, r 3,0 0,1Groove height, B 6,0 0,1Unreduced thicknessc, e9,0b0,2Reduced thicknessc, eg2,5d0,1Overall length, L 15
48、0,0 2,0Distance between ends of grips 70b1,0Misalignment between grooves Groove axis deviation from load axis0,1 0,01aGroove width and specimen width are the same.bFor a series of test specimens, the same dimension shall be used within the tolerance indicated.cReduced and unreduced thicknesses refer
49、 to the groove root thickness, eg, and plaque thickness, e, respectively.dThe reduced thickness in the groove shall be measured at three locations, at the centre of the groove, and at the edges of the test specimen. All three measurements shall conform to the dimensions specified in this table.Dimensions given in Table 1 are based on test specimens of polyethylene. Although considered independent of the material of the test specimen, new materials should be tested for suitability of a plane s
