1、BRITISH STANDARDBS EN 843-3:2005Advanced technical ceramics Mechanical properties of monolithic ceramics at room temperature Part 3: Determination of subcritical crack growth parameters from constant stressing rate flexural strength testsThe European Standard EN 843-3:2005 has the status of a Britis
2、h StandardICS 81.060.30g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 843-3:2005This British Standard was published under the authority of th
3、e Standards Policy and Strategy Committee on 31 January 2007 BSI 2007ISBN 978 0 580 49982 1National forewordThis British Standard was published by BSI. It is the UK implementation of EN 843-3:2005. It supersedes DD ENV 843-3:1997 which is withdrawn.The UK participation in its preparation was entrust
4、ed to Technical Committee RPI/13, Advanced technical ceramics.A list of organizations represented on RPI/13 can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Complianc
5、e with a British Standard cannot confer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 843-3 June 2005 ICS 81.060.30 Supersedes ENV 843-3:1996 English version Advanced technical ceramics - Mechanical prope
6、rties of monolithic ceramics at room temperature - Part 3: Determination of subcritical crack growth parameters from constant stressing rate flexural strength tests Cramiques techniques avances - Proprits mcaniques des cramiques monolithiques temprature ambiante - Partie 3: Dtermination des paramtre
7、s de propagation sous-critique des fissures partir des essais de rsistance la flexion raliss vitesse de contrainte constante Hochleistungskeramik - Mechanische Eigenschaften monolithischer Keramik bei Raumtemperatur - Teil 3: Bestimmung der Parameter des unterkritischen Risswachstums aus Biegefestig
8、keitsprfungen mit konstanter Spannungsrate This European Standard was approved by CEN on 14 April 2005. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
9、 Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
10、under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
11、 Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Sta
12、ssart, 36 B-1050 Brussels 2005 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 843-3:2005: EEN 843-3:2005 (E) 2 Contents Page Foreword 3 1 Scope. 4 2 Normative references. 4 3 Terms and definitions 4 4 Significance and use 5 5 Appa
13、ratus 6 5.1 Test jig. 6 5.2 Environmental control 7 5.3 Test machine. 7 5.4 Linear measuring devices 7 5.5 Drying oven. 7 5.6 Humidity measuring device . 8 6 Test pieces 8 7 Test procedure 8 8 Calculation 9 9 Precision and interferences. 10 10 Report 11 Annex A (informative) Derivation of relationsh
14、ip for determination of subcritical crack growth parameters from constant stressing rate flexural strength tests 13 Bibliography 14 EN 843-3:2005 (E) 3 Foreword This document (EN 843-3:2005) has been prepared by Technical Committee CEN/TC 184 “Advanced technical ceramics”, the secretariat of which i
15、s held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by December 2005, and conflicting national standards shall be withdrawn at the latest by December 2005. EN 843 Advanced technical cerami
16、cs Mechanical properties of monolithic ceramics at room temperature consists of six parts: Part 1: Determination of flexural strength; Part 2: Determination of Youngs modulus, shear modulus and Poissons ratio; Part 3: Determination of subcritical crack growth parameters from constant stressing rate
17、flexural strength tests; Part 4: Vickers, Knoop and Rockwell superficial hardness; Part 5: Statistical analysis; Part 6: Guide for fractographic examination. This document supersedes ENV843-3:1996. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followi
18、ng countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
19、Switzerland and United Kingdom. EN 843-3:2005 (E) 4 1 Scope This European Standard specifies a method for the determination of subcritical crack growth parameters of advanced monolithic technical ceramics in the temperature range 15 C to 30 C by measuring the dependence of mean fracture strength on
20、the rate of loading. The method is based on strength test procedures described in EN 843-1. This European Standard is not applicable to test pieces with artificially introduced flaws or cracks. 2 Normative references The following referenced documents are indispensable for the application of this do
21、cument. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 843-1, Advanced technical ceramics Mechanical properties of monolithic ceramics at room temperature Part 1: Determination of flex
22、ural strength EN ISO 7500-1, Metallic materials Verification of static uniaxial testing machines Part 1: Tension/compression testing machines Verification and calibration of the force measuring system (ISO 7500-1:2004) EN ISO/IEC 17025, General requirements for the competence of testing and calibrat
23、ion laboratories (ISO/IEC 17025:1999) ISO 3611, Micrometer callipers for external measurement ISO 4677-1, Atmospheres for conditioning and testing Determination of relative humidity Part 1: Aspirated psychrometer method ISO 4677-2, Atmospheres for conditioning and testing Determination of relative h
24、umidity Part 2: Whirling psychrometer method 3 Terms and definitions For the purposes of this European Standard, the following terms and definitions apply. 3.1 nominal flexural strength maximum nominal stress at the instant of failure supported by the material when loaded in linear elastic bending 3
25、.2 three-point flexure means of bending a beam test piece whereby the testpiece is supported on bearings near its ends and a central load is applied 3.3 four-point flexure means of bending a beam test piece whereby the test piece is supported on bearings near its ends and is equally loaded at two po
26、sitions symmetrically disposed about the centre of the supported span 3.4 subcritical crack growth extension of existing cracks or flaws under a stress which does not produce instant failure EN 843-3:2005 (E) 5 3.5 subcritical crack growth parameters parameters describing the relationship between cr
27、ack velocity and stress intensity factor 4 Significance and use Subcritical crack growth can occur in brittle solids at stress levels below that required to cause instantaneous failure. This effect may be caused by the testing environment, or by the intrinsic crack propagation behaviour of the mater
28、ial. The phenomenon leads to a decay of remaining strength in a manner determined by the loading history of the component or test piece. NOTE 1 A review of subcritical crack growth may be found in 1. The determination of subcritical crack growth parameters in accordance with this document allows the
29、 characterisation of the susceptibility of the material to subcritical crack growth, and thus its ability to support continued mechanical loading. Using these parameters it is possible to compare materials for susceptibility to loss of strength under load in particular environments, and to estimate
30、the lifetime of a component used under similar loading and environmental conditions. NOTE 2 The use of these parameters in design and lifetime estimation is not within the scope of this document. The relationship between the stress intensity factor at the tip of a crack or flaw and the velocity of t
31、he subcritically growing crack may be given by: nIcIKKAv=0(1) where v is the velocity of the growing crack in metres per second; A0is a constant in metres per second; KIis the critical stress intensity factor developed at the crack tip by the applied stress in Megapascals metres1/2; KIc= critical st
32、ress intensity factor at the crack tip required to cause instantaneous crack propagatio. NOTE 3 There are other algebraic representations of this relationship which are less convenient mathematically, but may be physically more realistic in practice. See, e.g. 2 and 3. 2 considers that practical dat
33、a cannot reliably distinguish between various relationships. The mathematical analysis in this document therefore does not cover such alternative relationships. In Equation (1), the value of n at room temperature is normally high, typically in the range fifteen to several hundred. At the lower end o
34、f this range, materials are very susceptible to subcritical crack growth, while at the upper end the phenomenon becomes insignificant. It should be recognised that Equation (1) implies a single simple relationship, but in practice there may be non-linearities. There are thought to be two principal c
35、auses of non-linearity: a) At low stress intensity factors there may be no subcritical crack growth. This is termed the subcritical crack growth threshold, or “fatigue limit“. b) At intermediate stress intensity factors, the crack growth rate may be limited by the rate at which the environment can p
36、enetrate along the crack to control fracture at the tip. This results in a EN 843-3:2005 (E) 6 plateau effect, which is maintained to KIlevels at which crack growth can occur in the absence of an environmental effect. It should be noted that n and A0are often functions of the environmental condition
37、s employed. In particular, many ceramics show marked subcritical crack growth in humid air or in water, and much less marked effects in dry or inert conditions. The test environment shall be defined and controlled for reproducible results. In this document, the parameter n and a parameter B0, which
38、is related to A0, are determined from the effect of stressing rate on flexural strength. NOTE 4 The term “dynamic fatigue“ is frequently used to describe such tests, but tends to be misunderstood. Its use is discouraged. Annex A shows how the mathematical formulation of the relationship between the
39、subcritical crack growth parameters based on Equation (1) and the effect of stressing rate on strength is derived, yielding the basic formula: B0is the constant; II Machined (by agreed procedure); III.1 Standard finish by grinding; III.2 Standard finish by lapping and/or polishing. The test piece di
40、mensions shall be as follows. Span A Length: 25 mm Width: 2,5 mm 0,2 mm Thickness: 2,0 mm 0,2 mm Span B Length: 45 mm Width: 4,0 mm 0,2 mm Thickness: 3,0 mm 0,2 mm The maximum tolerable variation in width and thickness of any individual test-piece shall be either: a) test pieces which have been mach
41、ined (II, III.1, III.2), 0,02 mm, or b) as-fired test pieces (I), 0,1 mm along the length of the test piece and 0,05 mm across the width or thickness. Test-pieces shall be chamfered along at least the two long edges bounding the face of the test piece to be subjected to tensile stress in the test. T
42、he chamfer shall be at approximately 45oto a distance of 0,12 mm 0,03 mm as measured along the face or side, or alternatively the edge may be rounded to 0,15 mm 0,05 mm radius. Any test pieces which do not meet the above dimensional requirements shall be rejected. Test-pieces shall be washed after m
43、achining and dried at 120 C 5 C in the oven. If the tests are to be performed in the ambient laboratory atmosphere, allow at least two hours equilibration in the ambient atmosphere before testing. The number of test-pieces shall be at least 50, of which 10 shall be tested at each of five different s
44、tressing rates. 7 Test procedure Measure the thickness and width of each test piece at a minimum of three positions approximately equidistant along its length, using the micrometer (see 5.4.1). EN 843-3:2005 (E) 9 Measure the test jig span(s) to the nearest 0,1 mm and, using the travelling microscop
45、e or other suitable device (see 5.4.2), check that the relative positions of the rollers are in accordance with the requirements of 5.1. Assemble the test-jig in the test machine and arrange the environmental control facility as appropriate to the agreed test programme. Select at least five loading
46、rates covering at least four orders of magnitude (e.g. 10-2N s-1, 10-1N s-1, 1 N s-1, 10 N s-1and 100 N s-1), and test at least 10 test pieces at each rate in the following manner. NOTE 1 If the available test machine does not offer preselected constant loading rates (load control), employ cross-hea
47、d displacement rate control and select five displacement rates covering four orders of magnitude in rate (see 5.3, Note 2). Insert each test piece in turn in the test jig and carefully align it in accordance with the practice given in EN 843-1. If the tests are being conducted in a controlled enviro
48、nment, unless otherwise agreed allow at least 2 h equilibration of the test-piece in the environment before stressing. NOTE 2 For chemically corrosive environments it may be desirable closely to define the equilibration period by agreement. If the tests are to be performed in a humid atmosphere, rec
49、ord the relative humidity. The relative humidity shall not change by more than 10 % during the course of the test series. Record the ambient temperature. The temperature may be between 15 C and 30 C, and shall not vary by more than 3 K during the test series. Choose a range for recording the force applied by the testing machine (when necessary) such that the expected mean fracture force is near the centre of the range. Apply the test force at the chosen rate and record the force/displac
