ASME B31J:2008 pdf free download

ASME B31J:2008 pdf free download.Standard Test Method for Determining Stress lntensification Factors(i-Factors) for Metallic Piping Components.
The ASME B31 Code for Pressure Piping and the ASME Boiler and Pressure Vessel Code, Section III, Nuclear Components, Subsections NC and ND piping rules require the use of stress intensification factors (i-factors or SIFs) when checking the adequacy of components and joints (welded and nonwelded) in piping subject to loadings, including those cyclic loadings that may produce fatigue failures. As used herein, where the word “Code” is used without specific identification, it means theCodeor Standard which incorporates or references this Standard. The piping Codes provide stress intensification factors for the most common piping components and joints. This Standard presents an experimental method to determine SlFs.
2 DEFiNITIONS
piping components: mechanical elements suitable for joining or assembly into pressure-tight, fluid-containing piping systems. Components include pipe, tubing, fittings, flanges, gaskets, bolting. valves, and devices such as expansion joints, flexible joints, pressure hoses, traps, strainers, in-line portions of instruments, and separators.
stress intensification factor: a fatigue strength reduction factor that is the ratio of the elastically predicted stress producing fatigue failure in a given number of cycles in a butt weld on a straight pipe to that producing fatigue failure in the same number of cycles in the component or joint under consideration.
3 TEST PROCEDURE
3.1 Test Equipment
A schematic of a test arrangement is given in Fig. 3.1.
(a) The machine framework must be sufficiently stiff to prevent significant rotation at the fixed end of the assembly. A significant rotation is one readily visible to the observer.
(b) The pipe component shall be mounted close to the fixed end of the test assemb1) but no closer than two pipe diameters.
(b) Paragraph 3.2. Markl’s tests specimens were ASTM A 106 Grade B material, or equivalent in the case of forgings, castings, and plate. Use of different materials requires a new C constant to be developed, since materials such as copper, aluminum, or very high-strength steels exhibit different fatigue life from plain carbon steel. The intent of the test is to develop an SIF that is geometry dependent, not material dependent.
Identifying nominal dimensions and wall thicknesses is important, particularly in the case of branch connections, to ensure extrapolation of results to other sizes is done correctly. The importance of the weld profile is clearly shown in reference 161.
(c) Paragraph 3.3. Marki’s tests were based on linear elastic equivalent moments, i.e., a constant displacement or rotation was applied and the moment at the failure location was based on extrapolation of the M-6 (or F-b) elastic curve. This allows agreement with the way linear elastic thermal expansion analyses are used, even though predicted stresses may be above yield.
(d) Paragraph 3.4. The use of a nominal pressure is to ensure a ready means of detecting a through-wall crack The use of 500 cycles as a minimum is to ensure correlation with the lower bounds of Marki’s work. From reference 141, it can be seen that the preponderance of tests lie above 1,000 cycles. The few that fall below show a fair amount of scatter off the proposed straight line. Until more work is done in the very low cycle range, the lower limit of 500 will remain.
(2) Section 4
(a) Paragraph 4.1. II forces are being applied, it is important to measure the distance from the point of application to the point of failure in order to determine the appropriate equivalent moment.
(1’) Paragraph 4.2. The section modulus is used in piping analysis to convert the calculated moments to stresses. Thus, it is important that the section modulus used to calculate the stress in the test agrees with that to be used in the analysis (and described in the Code).
(c) Paragraph 4.3. The equation in para. 4.3 is taken directly from the work by Markl [e.g., reference 141, eq. (4)1. Since Markl’s tests formed the basis of the current i-factors and Code rules, use of Markl’s equation is appropriate for correlation.
(d) Paragraph 4.4. The factor for the number of tests is to provide for uncertainty. The basis for the factors is engineering judgment. The basis is a reasonable estimate when compared to ASME BPVC, Section III.