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.

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.

Low-Cycle Fatigue Behaviour of Gas Turbine Alloys

1974 ◽  
Vol 188 (1) ◽  
pp. 321-328 ◽  
Author(s):  
W. J. Evans ◽  
G. P. Tilly
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
High Stress ◽  
Cyclic Creep ◽  
Fatigue Curve ◽  
Fatigue Behaviour ◽  
Material Surface ◽  
Tension Stress ◽  
Cycle Fatigue ◽  
Stress Tests

The low-cycle fatigue characteristics of an 11 per cent chromium steel, two nickel alloys and two titanium alloys have been studied in the range 20° to 500°C. For repeated-tension stress tests on all the materials, there was a sharp break in the stress-endurance curve between 103 and 104 cycles. The high stress failures were attributed to cyclic creep contributing to the development of internal cavities. At lower stresses, failures occurred through the growth of fatigue cracks initiated at the material surface. The whole fatigue curve could be represented by an expression developed from linear damage assumptions. Data for different temperatures and types of stress concentration were correlated by expressing stress as a fraction of the static strength. Repeated-tensile strain cycling data were represented on a stress-endurance diagram and it was shown that they correlated with push-pull stress cycles at high stresses and repeated-tension at low stresses. In general, the compressive phase tended to accentuate cyclic creep so that ductile failures occurred at proportionally lower stresses. Changes in frequency from 1 to 100 cycle/min were shown to have no significant effect on low-cycle fatigue behaviour.

Numerical Study on Longitudinal Distance Effect on Failure Stress of Non-Aligned Twin Cracked Pipe

2018 ◽  
Author(s):  
Thanh-Long Nguyen ◽  
Myeong-Woo Lee ◽  
Kunio Hasegawa ◽  
Yun-Jae Kim
Keyword(s):  
Fracture Strain ◽  
Numerical Study ◽  
Distance Effect ◽  
Failure Stress ◽  
Axial Distance ◽  
Damage Analysis ◽  
Asme Code ◽  
Bending Stresses ◽  
Strain Model ◽  
Longitudinal Distance

In this study, the effect of longitudinal distance H between non-aligned twin cracks is investigated using finite element damage analysis. The FE damage analysis based on the stress-modified fracture strain model is used to calculate the failure stress of non-aligned twin cracked pipe. Parametric study on the axial distance H between non-aligned twin cracks with various crack depths and lengths were conducted and compared with predictions using the alignment rules and the net-section collapse load approach for single crack provided in ASME Code. It is shown that the trend of the predicted collapse bending stresses for the non-aligned twin cracked pipes using FE damage analysis are different from the ones using the alignment rule.

High-Temperature Low-Cycle Fatigue Behavior of MarBN at 600 °C

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Richard A. Barrett ◽  
Eimear M. O'Hara ◽  
Padraic E. O'Donoghue ◽  
Sean B. Leen
Keyword(s):  
High Temperature ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Material Model ◽  
Cyclic Softening ◽  
Cyclic Strength ◽  
Cycle Fatigue ◽  
Viscoplastic Material

This paper presents the high-temperature low-cycle fatigue (HTLCF) behavior of a precipitate strengthened 9Cr martensitic steel, MarBN, designed to provide enhanced creep strength and precipitate stability at high temperature. The strain-controlled test program addresses the cyclic effects of strain-rate and strain-range at 600 °C, as well as tensile stress-relaxation response. A recently developed unified cyclic viscoplastic material model is implemented to characterize the complex cyclic and relaxation plasticity response, including cyclic softening and kinematic hardening effects. The measured response is compared to that of P91 steel, a current power plant material, and shows enhanced cyclic strength relative to P91.

The RCC-M Code 2007 Edition: Emphasis on New Technical and Regulatory Aspects

2008 ◽  
Author(s):  
Jean-Marie Grandemange
Keyword(s):  
General Rule ◽  
New Order ◽  
Trade Barriers ◽  
The European Union ◽  
Safety Requirements ◽  
Regulatory Aspects ◽  
Asme Code ◽  
High Level ◽  
Radioactive Release ◽  
Very High

In the context of the issuing of the European Pressure Equipment Directive (PED) the objective of which is to suppress trade barriers within the European Union, a new regulation has been issued in France for nuclear pressure equipment. This text makes reference to the Decree transposing the PED, while completing these provisions by supplementary requirements having the objective to provide a very high level of integrity guarantee for equipments which are the most important for safety, and to cover the prevention of radioactive release risks. Referencing the PED, and including specific provisions, the Ministerial Order implies that Codes and specifications should be updated in the following two domains: • that of the conformity of Codes and Standards used, generally inspired from the ASME Code Section III, with the essential safety requirements of the PED, • that of the respect of the complementary provisions brought by the new Order applying to nuclear pressure equipments (ESPN). This paper presents the more significant conclusions of this work and the resulting amendments of the RCC-M Code, introduced by the 2007 edition to that Code. It also presents the main evolutions integrated in the 2007 edition of the RCC-M to cover projects needs and integrate the consequences of the evolutions of standards to which the code refers. As a general rule, the RCC-M makes the largest use of European and ISO standards in order to facilitate its application in various industrial and regulatory contexts.

Development of fundamental and applied researches in the field of machine sciences using strength, safe life, survivability and safety criteria

2018 ◽  
Vol 84 (10) ◽  
pp. 41-52 ◽  
Author(s):  
N. A. Makhutov ◽  
M. M. Gadenin
Keyword(s):  
Equations Of State ◽  
Low Cycle Fatigue ◽  
Basic Research ◽  
Scientific Basis ◽  
Cyclic Strength ◽  
Physical Models ◽  
Safe Operation ◽  
Stress Strain ◽  
Engineering Research ◽  
Operation Conditions

The stages and results of fundamental and applied research regarding the problems of strength, resource, survivability and technogenic safety carried out at the A. A. Blagonravov Mechanical Engineering Research Institute of the Russian Academy of Sciences throughout a 80-year history are considered. Equations of state and criterion expressions regarding static and dynamic loading, high-cycle and a low-cycle fatigue resistance, high-temperature and low-temperature static and cyclic strength, stress-strain states analysis upon elastic and elastoplastic strain, problems of linear and nonlinear fracture mechanics are derived. The last decades have been marked by the development of basic research on the mechanics of catastrophes, survivability and man-made safety of machines and structures, including the results of complex developments in all the listed areas of strength and resource. The results of studying strength, resource and survivability are the basic components for the mechanics of catastrophes and risks in the technogenic sphere, as well as the new principles and technologies for technogenic objects ensuring their safe operation and prevention on a reasonable scientific basis emergency and catastrophic situations and°r minimize possible damages attributed to them. Diagnostics of the current parameters of the material state and determination of the characteristics of stress-strain states in the most loaded zones of the analyzed technical system is thus a tool for ensuring safe operation conditions. The solution to the problem of assessing the strength and resource in such conditions includes creation of generalized mathematical and physical models of complicated technological, operation and emergency processes in technical systems to analyze conditions of their transition from normal state to emergency or catastrophic states. It is shown that as the analyzed structure passes through admissible to limiting states thus causing the occurrence of failures and subsequent emergency and catastrophic situations, it is necessary to introduce into the regulatory calculations of such states an additional set of defining equations and their parameters characterizing these limiting states. Those calculations are based on the systems of criterion equations, including the parameters of risk, safety and security of the technosphere objects.

Failure Mode and Failure Strengths for Wall Thinning Straight Pipes and Elbows Subjected to Seismic Loading

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Kunio Hasegawa ◽  
Katsumasa Miyazaki ◽  
Izumi Nakamura
Keyword(s):  
Cyclic Loading ◽  
Crack Initiation ◽  
Failure Mode ◽  
Seismic Event ◽  
Low Cycle Fatigue ◽  
Seismic Loading ◽  
Fatigue Curve ◽  
Wall Thinning ◽  
Piping Systems ◽  
Asme Code

It is important to assess the failure strengths for pipes with wall thinning to maintain the integrity of the piping systems and to make codification of allowable wall thinning. Full-scale fracture experiments on cyclic loading under constant internal pressure were performed for 4in. diameter straight pipes and 8in. diameter elbow pipes at ambient temperature. The experiments were low cycle fatigue under displacement controlled conditions. It is shown that a dominant failure mode under cyclic loading for straight pipes and elbows is crack initiation∕growth accompanying swelling by ratchet or buckling with crack initiation. When the thinning depth is deep, the failure mode is burst and crack growth with ratchet swelling. In addition, failure strengths were compared with the design fatigue curve of the ASME Code Sec. III. It is shown that pipes with wall thinning less than 50% of wall thickness have sufficient margins against a seismic event of the safety shutdown earthquake.

Techniques for Modeling Thermal and Mechanical Stresses Generated in Catalytic Cracker and Coke Drum Hot Boxes

2005 ◽  
Author(s):  
Chris Alexander ◽  
Richard Boswell
Keyword(s):  
Heat Transfer ◽  
Thermal Stresses ◽  
Low Cycle Fatigue ◽  
Radiation Heat Transfer ◽  
Field Measurements ◽  
Sensitivity Analyses ◽  
Finite Element Models ◽  
Air Space ◽  
Bending Stresses ◽  
Transient And Steady State

Consideration of heat transfer loading between surfaces during transient and steady state conditions is required when analyzing vessels that involve secondary stresses and low cycle fatigue. Some of the higher stresses occur in enclosed, non-insulated air space regions, referred to as a hot box, between a supporting skirt (or shell) and a vessel. Hot boxes are critical parts of vessel designs in catalytic crackers and delayed coke drums. In coke drum cycles, the sudden heating of the vessel generates significant bending stresses in the skirt, and radiation heat transfer causes a greater area of skirt to be heated when compared to conduction alone. This heat must be removed during the cooling transient or the hot expanded skirt will be pulled by the contracting vessel, resulting in large bending stresses. It is the experiences of the authors that failures to calculate the transient temperatures in the components often underestimate fatigue stresses. Some of the important elements associated with modeling thermal stresses in hot boxes include using appropriate boundary conditions, radiation and convection conditions, pressure end loads, and conductivities for the insulation materials. This paper emphasizes the importance of performing detailed sensitivity analyses when unknown thermal or mechanical loading conditions exist. Examples include the effects of convection properties within the hotbox and conditions associated with transient loads. Discussions are also provided on the potential geometric issues associated with the use of axisymmetric finite element models. Additionally, this paper discusses the importance of making field measurements to enhance modeling assumptions. Discussions will be provided on the best methods for acquiring field data and the techniques employed.

Evaluation of Alternate Interpretations Regarding the Conditions for Exclusion of Thermal Bending Stresses in Simplified Elastic-Plastic Stress Analyses

2006 ◽  
Author(s):  
Robert B. Keating ◽  
Richard O. Vollmer
Keyword(s):  
Finite Element Analyses ◽  
Sample Problem ◽  
Secondary Stress ◽  
Elastic Plastic ◽  
Thermal Ratcheting ◽  
Plastic Analysis ◽  
Thermal Bending ◽  
Asme Code ◽  
Bending Stresses ◽  
Simplified Analysis

The ASME Code permits the range of primary plus secondary stress to exceed the stress limit of 3Sm, provided that several key conditions are satisfied. These conditions are provided in Paragraph NB-3228.5, “Simplified Elastic-Plastic Analysis”. The first condition is that the range of primary plus secondary stress intensity, excluding thermal bending stresses, shall be less than 3Sm. The term “thermal bending” is not clearly defined in the Code and at least two Code Interpretations have been issued with differing viewpoints. The first interpretation is that only those stresses due to the radial through-wall temperature distribution may be excluded; the second is that all thermal bending stresses, including thermal discontinuity stresses, may be excluded. In order to investigate the suitability of these two interpretations, elastic-plastic analyses are conducted of a highly restrained sample geometry. First, the sample problem is evaluated using the ASME Code rules for simplified elastic-plastic analysis for thermal ratcheting and fatigue, as required by NB-3228.5. Subsequently, cyclic elastic-plastic finite element analyses are conducted to determine if the simplified analysis rules provide adequate protection with regard to thermal ratcheting and fatigue. These analyses are performed using both interpretations to determine if adequate designs can be achieved for the sample problem selected.

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