scholarly journals PECULIARITIES OF CALCULATING THE CYCLIC STRENGTH OF IMPORTANT THREADED JOINTS

2002 ◽  
Vol 8 (1) ◽  
pp. 42-48
Author(s):  
Mindaugas Leonavičius ◽  
Algimantas Krenevičius ◽  
Stanislav Stupak ◽  
Marijonas Šukšta
Keyword(s):  
Nuclear Power ◽  
Cyclic Strength ◽  
Minimum Size ◽  
Power Equipment ◽  
Calculation Methods ◽  
Limit States ◽  
Theoretical Investigations ◽  
Asme Code ◽  
Threaded Joints ◽  
Definition Of

The calculation of the strength of important threaded joints is started by defining the minimum size of the cross-section of bolts (studs). Then the static and cyclic strength is tested. The studs of the demountable joints of nuclear power equipment are calculated in accordance with the norms of the Russian Federation and the ASME Code. The calculation methods coincide in essence, they are based on similar limit states; however, there also some differences exist. The authors investigate and compare both methods in their work. There is a brief analysis of calculation methods in the article. For closer definition of standards and their substantiation the authors used experimental and theoretical investigations performed at Laboratory of Strength Mechanics of Vilnius Gediminas Technical University. In order to develop a uniform cyclic strength and shakedown calculation procedure for critical threaded joints, a completely new calculation of a progressive profile change is recommended to be performed before the calculation of cyclic strength. The results have been used in the development of calculation standards for nuclear power equipment, in designing mineral grinding machines and evaluating their residual resource.

scholarly journals Assessment of the Durability of Threaded Joints

2021 ◽  
Vol 11 (24) ◽  
pp. 12162
Author(s):  
Žilvinas Bazaras ◽  
Mindaugas Leonavičius ◽  
Vaidas Lukoševičius ◽  
Laurencas Raslavičius
Keyword(s):  
Shape Change ◽  
Failure Process ◽  
Experimental Studies ◽  
Pressure Vessels ◽  
Experimental Investigations ◽  
Engineering Practice ◽  
Calculation Methods ◽  
Limit States ◽  
Plastic Failure ◽  
Threaded Joints

The article deals with the determination of the resistance to cyclic loading of the threaded joints of pressure vessels and defective elements according to the failure mechanics criteria. Theoretical and experimental studies do not provide a sufficient basis for the existing calculation methods for the cyclic strength of the threaded joints of pressure vessels. The short crack kinetics in the threaded joints, a shakedown in one of the joint elements of pressure vessels, i.e., in the bolt or stud, has not been studied sufficiently. The calculation methods designed and improved within the study were based on theoretical and experimental investigations and were simplified for convenient application to engineering practice. The findings could be used to investigate the shakedown of studs of a different cross-section with an initiating and propagating crack. Value: the developed model for the assessment of durability of the threaded joints covers the patterns of resistance to cyclic failure (limit states: crack initiation, propagation, final failure) and shakedown (limit states: progressive shape change and plastic failure). Analysis-based solutions of plastic failure conditions and progressive shape change were accurate (the result was reached using a two-sided approach; the solutions were obtained in view of the parameters of the cyclic failure process in the stud (bolt) and based on experimental investigations of the threaded joints).

scholarly journals ANALYSIS OF EXPERIMENT AND CALCULATION OF THE THREADED JOINTS UNDER TENSION AND CYCLIC BENDING/TEMPIAMŲ IR CIKLIŠKAI LENKIAMŲ SRIEGINŲ JUNGČIŲ BANDYMŲ IR SKAIČIAVIMŲ ANALIZĖ

1999 ◽  
Vol 5 (3) ◽  
pp. 170-175
Author(s):  
Algimantas Krenevičius ◽  
Marijonas Stupak
Keyword(s):  
Low Cycle Fatigue ◽  
General Rule ◽  
Deformation Energy ◽  
Cyclic Strength ◽  
Tension Stress ◽  
General Effect ◽  
Energy Devices ◽  
Asme Code ◽  
Threaded Joints ◽  
Bending Stresses

The effect of individual elements of the system “bolt-nut” under tension and bending on the cyclic strength is a complicated and insufficiently clear subject. The data presented in the works of the laboratories of strength mechanics and those of the present authors have been obtained when the ratio of bending and tension stress caused by eccentrically applied tension force was from 0 to 1.5. If stresses caused by bending account for 0.25 σ y of tension stresses, the strength to low-cycle fatigue somewhat increases. When σ m = 1.5σ n , the decrease in longevity is observed. The results obtained, however, differ insignificantly from the longevity of threaded joints under cyclic tension as long as bending stresses do not exceed 0.5. σ y . A comprehensive experimental study of these problems and the analysis are presented in the works of the present authors. One of the main factors determining the cyclic strength of the system “bolt-nut” is the distribution of internal resultants. The distribution of internal resultants after the threaded joint has been tightened up to σ t = 0.6σ y corresponds to the general rule which is characteristic of joints under tension. During the first stress cycle due to bending deformations in the cavity of turns of the threads also correspond to the general rule of internal resultant distribution of joints under tension in the layers under tension. In layers under compression, the general effect of tightening and the nut distort the generally accepted laws. The analysis of the formation of the crack and its propagation showed there can be either a single or double crack. When the crack reaches the critical size, the remaining part fractures mostly on account of the deformation energy which was accumulated when stretching the stud, whereas the cyclic propagation of the crack takes place due to bending deformations. Under fluctuating loads threaded joints loosen. Therefore tightness of a vessel subject to high pressure may be lost or the maintenance regime of some device may be disturbed. Due to crushing of contacting surfaces of transmission parts and the thread, spontaneous turn of the nut, plastic deformations in the thread and transmission parts, tightening of the bolt and tightness of transmissions parts may decrease. Studs of demountable joints of energy devices are calculated in accordance with the norms of the Russian Federation and the ASME code. The calculation methods coincide in essence, they are based on similar marginal states. Nevertheless, there exist some differences. The article gives a comparison of some calculating rules for low cycle fracture resistance of the threaded joints.

Nuclear Power Equipment (Design)

2014 ◽  
Vol 83 (4) ◽  
pp. 270-274 ◽  
Author(s):  
Masashi KAMEYAMA
Keyword(s):  
Nuclear Power ◽  
Equipment Design ◽  
Power Equipment

Chinese Public and Nuclear Experts May Have Different Perceptions Of Severe Nuclear Accidents

2021 ◽  
Author(s):  
Hsingtzu Wu ◽  
Leyao Huang
Keyword(s):  
Nuclear Power ◽  
Nuclear Accident ◽  
Severe Accident ◽  
The Public ◽  
Severe Accidents ◽  
White Collar Workers ◽  
Questionnaire Surveys ◽  
Definition Of ◽  
Chinese Public ◽  
Severe Nuclear Accident

Abstract Nuclear power has been a controversial social issue, and societal acceptance is critical to its development and future. In addition, risk informed rules and regulations rely on the public’s understanding. However, there seems a communication gap about nuclear safety between nuclear experts and the public in China, and three questionnaire surveys were conducted to better understand Chinese public’s perceptions of a severe nuclear accident. The sample sizes were 117, 280 and 1071. Most of the respondents were students or white-collar workers born after 1990. In these three surveys, we found that more than 85% of respondents consider a less severe accident as a severe nuclear accident, and most respondents considered an incident to constitute a severe nuclear accident. The results demonstrate that nuclear experts and Chinese public may have different definitions of a severe nuclear accident. Therefore, we suggest that the definition of severe accidents should be better explained to the public to benefit the communication about risk informed rules and regulations. In addition, our three different surveys yielded a similar result, and we anticipate that a questionnaire survey with a larger sample size would do the same.

Development of a Fatigue Design Curve for Austenitic Stainless Steels in LWR Environments: A Review

2002 ◽  
Author(s):  
Omesh K. Chopra
Keyword(s):  
Stainless Steels ◽  
Pressure Vessel ◽  
Type Strain ◽  
Nuclear Power ◽  
Austenitic Stainless Steels ◽  
Environmental Parameters ◽  
Light Water Reactor ◽  
Code Design ◽  
Fatigue Design ◽  
Asme Code

The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components and specifies fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Existing fatigue strain–vs.–life (ε–N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. This paper reviews the existing fatigue ε–N data for austenitic stainless steels in LWR coolant environments. The effects of key material, loading, and environmental parameters, such as steel type, strain amplitude, strain rate, temperature, dissolved oxygen level in water, and flow rate, on the fatigue lives of these steels are summarized. Statistical models are presented for estimating the fatigue ε–N curves for austenitic stainless steels as a function of the material, loading, and environmental parameters. Two methods for incorporating environmental effects into the ASME Code fatigue evaluations are presented. Data available in the literature have been reviewed to evaluate the conservatism in the existing ASME Code fatigue design curves.

Suggested Improvements to Appendix G of ASME Section XI Code

2008 ◽  
Author(s):  
Hardayal S. Mehta ◽  
Timothy J. Griesbach ◽  
Gary L. Stevens
Keyword(s):  
Thermal Gradient ◽  
Research Council ◽  
Ductile Failure ◽  
Calculation Methods ◽  
Technical Literature ◽  
Corner Crack ◽  
The Past ◽  
Asme Code ◽  
Reactor Pressure ◽  
Calculation Procedures

This paper reviews some of the original basis documents for ASME Section XI Nonmandatory Appendix G for calculating pressure-temperature (P-T) limits and recommends areas for improvement. The original Appendix G in Section XI of ASME Code was mainly based on Welding Research Council (WRC) Bulletin 175 (WRC-175). Changes have been made to Appendix G over the past 20 years such as the use of the KIC reference toughness curve instead of KIR. However, aspects of the Appendix G method still refer back to WRC Bulletin 175. The published technical literature since the development of WRC 175 could be used to enhance the Appendix in a number of areas. One such area is stress intensity factor (K) calculation procedures for thermal gradient loading at a nozzle corner. This paper will review and evaluate the available K calculation methods for a nozzle corner crack, and develop closed-form expressions for incorporation into Appendix G. Also, the following areas will be reviewed: (1) treatment of operating stresses exceeding the material yield stress, and (2) fracture toughness criteria typically used for other than reactor pressure vessel (RPV) and piping for protection against non-ductile failure. This paper will also identify areas for future improvements in Appendix G.

scholarly journals Reply to Nicholson's comment on "Consistent calculation of aquatic gross production from oxygen triple isotope measurements" by Kaiser (2011)

2012 ◽  
Vol 9 (8) ◽  
pp. 2921-2933 ◽  
Author(s):  
J. Kaiser ◽  
O. Abe
Keyword(s):  
Isotope Fractionation ◽  
Direct Calculation ◽  
Original Data ◽  
Delta Method ◽  
Base Case ◽  
Calculation Methods ◽  
Input Parameters ◽  
Net To Gross ◽  
Number Of Publications ◽  
Definition Of

Abstract. The comment by Nicholson (2011a) questions the "consistency" of the "definition" of the "biological end-member" used by Kaiser (2011a) in the calculation of oxygen gross production. "Biological end-member" refers to the relative oxygen isotope ratio difference between photosynthetic oxygen and Air-O2 (abbreviated 17δP and 18δP for 17O/16O and 18O/16O, respectively). The comment claims that this leads to an overestimate of the discrepancy between previous studies and that the resulting gross production rates are "30% too high". Nicholson recognises the improved accuracy of Kaiser's direct calculation ("dual-delta") method compared to previous approximate approaches based on 17O excess (17Δ) and its simplicity compared to previous iterative calculation methods. Although he correctly points out that differences in the normalised gross production rate (g) are largely due to different input parameters used in Kaiser's "base case" and previous studies, he does not acknowledge Kaiser's observation that iterative and dual-delta calculation methods give exactly the same g for the same input parameters (disregarding kinetic isotope fractionation during air-sea exchange). The comment is based on misunderstandings with respect to the "base case" 17δP and 18δP values. Since direct measurements of 17δP and 18δPdo not exist or have been lost, Kaiser constructed the "base case" in a way that was consistent and compatible with literature data. Nicholson showed that an alternative reconstruction of 17δP gives g values closer to previous studies. However, unlike Nicholson, we refrain from interpreting either reconstruction as a benchmark for the accuracy of g. A number of publications over the last 12 months have tried to establish which of these two reconstructions is more accurate. Nicholson draws on recently revised measurements of the relative 17O/16O difference between VSMOW and Air-O2 (17δVSMOW; Barkan and Luz, 2011), together with new measurements of photosynthetic isotope fractionation, to support his comment. However, our own measurements disagree with these revised 17δVSMOW values. If scaled for differences in 18δVSMOW, they are actually in good agreement with the original data (Barkan and Luz, 2005) and support Kaiser's "base case" g values. The statement that Kaiser's g values are "30% too high" can therefore not be accepted, pending future work to reconcile different 17δVSMOW measurements. Nicholson also suggests that approximated calculations of gross production should be performed with a triple isotope excess defined as 17Δ#≡ ln (1+17δ)–λ ln(1+18δ), with λ = θR = ln(1+17ϵR ) / ln(1+18ϵR). However, this only improves the approximation for certain 17δP and 18δP values, for certain net to gross production ratios (f) and for certain ratios of gross production to gross Air-O2 invasion (g). In other cases, the approximated calculation based on 17Δ† ≡17δ – κ 18δ with κ = γR = 17ϵR/18ϵR (Kaiser, 2011a) gives more accurate results.

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