EN ISO 7539-5-1995 en Corrosion of Metals and Alloys - Stress Corrosion Testing - Part 5 Preparation and Use of C-Ring Specimens First Edition《金属与合金的腐蚀 应力腐蚀试验 第5部分 C-环行试样的制备和使用(ISO.pdf
《EN ISO 7539-5-1995 en Corrosion of Metals and Alloys - Stress Corrosion Testing - Part 5 Preparation and Use of C-Ring Specimens First Edition《金属与合金的腐蚀 应力腐蚀试验 第5部分 C-环行试样的制备和使用(ISO.pdf》由会员分享,可在线阅读,更多相关《EN ISO 7539-5-1995 en Corrosion of Metals and Alloys - Stress Corrosion Testing - Part 5 Preparation and Use of C-Ring Specimens First Edition《金属与合金的腐蚀 应力腐蚀试验 第5部分 C-环行试样的制备和使用(ISO.pdf(21页珍藏版)》请在麦多课文档分享上搜索。
1、 CEN N*IS0*?539- 5 95 3404589 0109308 L87 Corrosion of metals and alloys - Stress corrosion testing Part 5. Preparation and use of C-ring specimens The European Standard EN 7539-5 : 1995 has the status of a British Standard BS EN IS0 7539-5 : 1995 - CEN EN*IS0*7539- Amd.No. =?%- 5 95 m Date Text aff
2、ected *-M”S s. b.sp-e-T BS 6980 : Part 5 : 1990 Committees responsible for this British Standard The piqmratioii of this I3i-itish Standard was entiiistetl by the Iron and Steel Staiidrtiuls Policy Coiniiiit t er (ISMi-) and Non-cwous Metals Standards Policy Coininittce (NFM -) to Technical Coininit
3、tce ISM NFJI 8. upon which the following twdies were represented: Aluminium Federatior? British Gas pic British Steel Industry Department of Trade and Industry (National Physical Laboratory) Department of Transport (Transport and Rtmd Research Laboratory) Electricity Supply industry in England and W
4、ales Institution of Carrosion Science and Technology Institution of Structural Engineers Society of Chemical Industry United Kingdom Atomic Energy Authority Welding Institute This British Standard, having been prepared under the direction of the Iron and Steel Standards Poiicy Cornmittee and the Non
5、-Ferrous Metals Standards Policy Committee, was published under the authority of the .Paration and use of bent-beam specimens Part 3 Prepamtion and use of U-bend speciw Part 4 that is, transverse as well as circumferential stresses are developed. The transverse axial stress varies from a maximum at
6、the mid-width to zero at the edges, and has the same sign as the Circumferential stress. In general, the transverse stress decreases with decreasing width-to-thickness and increasing diameter-to-thickness ratios. 5.2.3 In the case of the notched C-ring a triaxial stress state is present adjacent to
7、the root of the notch. In addition, the cir- cumferential stress at the root of the notch will be greater than the nominal stress and generally may be expected to be in the plastic range. 5.2.4 When C-rings are machined from products that contain appreciable residual stress or are subjected to heat
8、treatment involving quenching after being machined, internal stresses may be present. These may introduce errors in the calculated stress. It is necessary to measure the tubing diameter before and after the axial cut is made and to use these measurements to calcu- late the residual stresses in the t
9、ube. 5.2.5 The possibility of relaxation during the exposure period should be considered, especially when specimens are exposed at elevated temperatures. Relaxation can be estimated if creep data are available for both the ring and the stressing bolt. NOTE - If the ring and bolt have different coeff
10、icients of thermai expansion, the applied stress may be significantly changed when testing at elevated temperatures Alm, if plastic insulators are used to Dimensions in millimetres ext. 10,05 II 9int. 1o,o5 II 1,6 min. Figure 2 - Example of C-ring specimen 3 - CEN EN*ISO*7539- 5 95 M 3404589 OLO93L7
11、 L9T IS0 7!539-5 : 1989 (E) avoid galvanic corrosion, the possibility of stress relaxation should be anticipated. 5.3 Stressing methods metre; where E is the modulus of elasticity, in newtons per square 5.3.1 C-ring specimens are usually loaded under constant p is Poissons ratio: displacement condit
12、ions with tensile stress produced on the exterior of the ring by tightening a bolt centred on the diameter of the ring see figure 3a)l. 5.3.2 C-rings can alternatively be stressed in the reverse direc- E, is the circumferential strain; ct is the transverse strain. When using electrical strain gauges
13、 on thin walled C-rings, a , correction should be allowed for the displacement of the gauge adhesive must be removed from the C-ring before it is exposed. tion by spreading the ring and creating a tensile stress on the in- side by the use Of a in figure 4. In the latter case the necessary displaceme
14、nt is pro- vided by inserting an accurately machined wedge of the same as in figure 3c Or wedge Opening technique to the arms Of the C-rings as from the of the ring. All traces ?f the gauge and material as the C-ring, CO avoiding galvanic effects. A suitable jig for inserting the wedge is shown in f
15、igure 4. Calculation of stresses above the limit of elasticity may be car- ried out on the basis of an electric-plastic analysis. 5.3.3 The C-ring test can be modified for approximately con- 5.3.5 When several rings of the same alloy and dimensions are to be loaded, it is convenient to determine a c
16、alibration stant load conditions by the use of a suitably calibrated spring placed on the loading bolt see figure 3b)l. 5.3.4 The most accurate stressing procedure is to attach cir- cumferential and transverse electrical strain gauges to the sur- face stressed in tension and to tighten the bolt unti
17、l the strain measurements indicate the desired circumferential stress. The circumferential oc and transverse ot stresses are calculated as follows provided that they are within the elastic range : E 1-112 ff, = - (E, + PEt) curve of circumferential stress versus ring deflection to avoid the inconven
18、ience of strain-gauging each ring. 5.3.6 The amount of compression required on the C-ring to produce elastic straining only, and the degree of elastic strain can be predicted theoretically. Therefore, C-rings may be stressed by calculating the deflection required to develop a desired elastic stress
19、by using the individual ring dimensions in a modified curved beam formula as shown in annex A. Experience shows good agreement between the stresses calculated in this way and those measured by fixing strain gauges to specimens. a) Constant strain bl Constant load Figure 3 - Methods of stressing C-ri
20、ngs ci Constant strain 4 IS0 7539-5 : 1989 (E) 5.3.7 Alternatively the stress-strain distribution throughout the specimen, for various applied displacements of the C-ring, may be calculated using the finite element method of stress analysis. Such analyses should be done using well established finite
21、 element programmes and by personnel fully conversant with the finite element technique. The method would normally be used for specimens with more complex geometries or loading configurations for which simple theoretical analysis is not applicable. 5.3.8 For notched specimens (see 5.2.3) a nominal s
22、tress is assumed using the ring outside diameter measured at the root of the notch. The maximum stress at the notch is then calculated from the product of the nominal stress and the stress concentration factor K, for the specific notch. 5.4 Machining and surface preparation 5.4.1 A high quality mach
23、ined surface is the most desirable for corrosion test purposes unless it is desired to test the as- manufactured surface of a tube or bar. When rings are machined from solid stock, precautions should be taken to avoid practices that overheat, plastically deform, or develop residual stress in the met
24、al surface. Machining should be done in stages so that the final cut leaves the principal surface with a clean finish of 1 pm rms or better. Lapping, mechanical polishing, and similar operations that pro- duce flow of the metal should be avoided. 5.4.2 The surface of the specimen should be degreased
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