Low Cycle Fatigue Design Research Articles

Low-cycle fatigue design for reinforced high-strength concrete under high compressive stress

As engineering endeavors push the boundaries of material and design capabilities, the significance of understanding and mitigating fatigue in construction materials becomes paramount. This study specifically investigates the low-cycle fatigue performance of reinforced high-strength concrete (RHSC). Using rigorous data collection, we established a clear link between interpretable machine learning analysis and the fatigue properties of RHSC. A trained model was developed, yielding a straightforward formula tailored to low-cycle fatigue design considerations for RHSC. This model stands as a testament to the potential for marrying traditional engineering practices with advanced statistical techniques. Our results emphasize that, when appropriately applied, regression analysis can be instrumental in enhancing the durability and longevity of RHSC structures exposed to dynamic loadings. This research not only underscores the pivotal role of statistical methods in fatigue design but also champions the broader adoption of such techniques in evolving engineering landscapes.

Low-cycle fatigue design of welded offshore pipe components: A modern view on ASME B31 code

The welded pipe components are prone to low-cycle fatigue (LCF) at welds, especially under extreme loadings. ASME B31.8 specifies the fatigue design rules of the welded pipelines. In this work, the LCF fatigue analysis approach stipulated in the ASME B31 code is revisited to figure out its underlying mechanism, limitations, and scope, by analyzing two sets of LCF fatigue data of piping structures using different strain information. A structural strain method is proposed to generalize the pseudo-stress idea implied in the ASME code, which correlates large amounts of high- and low-cycle fatigue data of weldments into the master E-N curve.

Generation of Low Cycle Fatigue Design Data for Nitrogen Enhanced 316LN SS as per RCC-MR Code

Generation of Low Cycle Fatigue Design Data for Nitrogen Enhanced 316LN SS as per RCC-MR Code

Taking residual stresses into account in low-cycle fatigue design using the adjustable localisation operator method

This paper assesses the ability of the Adjustable Localisation Operator (ALO) method to predict the influence of residual stresses on the fatigue behaviour of notched components. Different initial residual stress states are introduced into notched specimens, which are then tested under cyclic loadings in a fatigue range of 103 to 105 cycles. Experimental comparisons with initially stress-free specimens have shown how tensile residual stresses reduce fatigue life under repeated compressive loading while compressive residual stresses increase fatigue life under repeated tensile loading.Finite Element Analysis (FEA) and ALO method predictions of changes in residual stress are compared to experimental measurements beforehand to assess fatigue life predictions. A modified version of Morrow’s criterion is used to account for the mean stress effect. Results have shown that the ALO method can predict the influence of residual stresses on low-cycle fatigue with the same accuracy as finite element analysis and with a significant reduction in computation time.

Effect of Cryogenic Temperature on Low-Cycle Fatigue Behavior of AISI 304L Welded Joint

The aim of this study is to investigate the low-cycle fatigue (LCF) properties of an AISI 304L welded joint based on experimental data. The influential parameters on the LCF such as the specimen thickness, strain ratio and cryogenic temperature were considered in this experimental study. In order to investigate the thickness effect on the LCF behavior, two types of specimens with thicknesses of 5 mm and 10 mm were used in an LCF test. In addition, the fatigue tests were conducted under strain control with three different strain ratios of R = −1, 0, and 0.5 at room and cryogenic temperatures. Based on the results obtained by this experimental study, no significant effect involved with the thickness and the strain ratio were observed. However, it was clearly observed that LCF performance at room temperature is lower than that at cryogenic temperature. Finally, an LCF design curve that can be used in design of the liquefied natural gas (LNG) applications is suggested.

Investigation of the probabilistic low cycle fatigue design curves at stress cycling

This paper presents the investigation of probabilistic calculation of low cycle fatigue curves. The experiment of low cycle fatigue was made and cyclic constants were defined. Based on data obtained, design curves of equal fracture probability 15Cr2MoVA and 45 at low cycle stress limited loading were drawn. The design curves were compared with experimental data and the conclusions were made. Low cycle stress limited calculation for anisotropic materials showed a satisfactory agreement with experimental data and can be used in lifetime assessment of various power plant facilities. DOI: http://dx.doi.org/10.5755/j01.mech.23.2.14358

304L 스테인리스 강 용접부의 저주기 피로 성능 평가

Recently, the market of liquefied natural gas is growing in accordance with shale gas development and environmentally friendly policies. Also, LNG is in the spotlight as an alternative fuel to previously used fossil fuel and the fuel for the ship to meet emission standards which takes effected by IMO (International Maritime Organization). According to growth of LNG, LNG carriers needs are also expected to increase significantly. This study investigates low cycle fatigue (LCF) performance of 304L stainless steel weldments to investigate fatigue performance in plastic strain region. 304L stainless steel is known to have improved fatigue performance at cryogenic conditions. LCF behavior are investigated by a strain-controlled condition up to 1% strain range and conducted with three different thickness (3mm, 5mm, 10mm). Also, test were performed with three different strain ratio R such as R = -1, -0, 0.5, Finally, the fatigue design curve for 304L stainless steel weldments at room temperature are proposed. Considering all test conditions, it is shown that LCF performance have similar tendency regardless of thickness and strain ratio. LCF design curve of 304L stainless steel weldments are lower than 304L stainless steel base metal. Key words: Low cycle fatigue, 304L Stainless steel, Strain-controlled, Fatigue design curve

Low cycle fatigue design data for India-specific reduced activation ferritic-martensitic (IN-RAFM) steel

The objective of the present paper is to provide first hand experimental data and analysis on the low cycle fatigue (LCF) performance of a commercial heat of Indian reduced activation ferritic-martensitic (IN-RAFM) steel. Since this material is not yet codified in RCC-MR, cyclic properties were generated for the design of the structural material of the Test Blanket Modules (TBM) made of RAFM steel. Hence, as a part of the material development program, LCF experiments were conducted on IN-RAFM steel obtained in the normalized and tempered condition. Total axial strain controlled experiments were performed in air by employing strain amplitudes ranging from ±0.25 to ±1.0% and at temperatures of 300, 673, 723, 823, and 873K and a nominal strain rate, 3×10−3s−1. In the present work, various cyclic parameters that are useful for the design oriented fatigue analysis are derived as per the systematic procedure given in the RCC-MR design code. The physical significance of each design parameter such as elasto-plastic corrections based on Neuber analysis has been explained and correlated with the material behavior such as the cyclic softening nature of the RAFM steel.

PS06 小標本数試験データおよび実機検査記録を用いた信頼性設計手法の開発

Probabilistic safety assessment is an effective method to improve the conservative safety factors on low cycle fatigue life of turbine blades used in jet engines. This paper focuses on uncertainties of low cycle fatigue design life result from small samples and surface finishes. Improvement of uncertainty of design fatigue life, reflected from small sample tests, by use of inspection data is verified through Bayesian update and virtual inspection data. Furthermore, tension-compression low cycle fatigue tests on Inconel 718 were conducted with the specimens, of which surfaces were finished Ra 0.8, Ra 6.3, and Ra 12.5. The results indicates strain-amplitude dependence of the influence of surface finishes on low cycle fatigue life. In order to investigate the effect of surface finishing on low cycle fatigue life, local misorientations of surface layer of specimens are measured by EBSD.

A Low-Cycle Fatigue Design Combined Finite Element Analysis about Pressure Vessels

The study of Low-Cycle fatigue showed that strain is more important parameter than stress for describing fatigue property of materials .Exactly obtaining regional strain of the structure by analysis is key in fatigue design of complex structure .Therefore, the analysis and solution by finite element is very necessary. The maximum elastic and plastic strain at the nozzle junction of a pressure vessel under several loadings are calculated by using ANSYS software .Then crack forming life is calculated by using the N.E.Dowling formula .

A Reliability-Based Expression of ASME B&PV Code Equation (11) for Class 2 and 3 Nuclear Pipes

Previous research provided a reliability-based approach for the low-cycle fatigue design of Class 2 and 3 nuclear pipes. Reliability-based equations incorporate a threshold for the piping reliability and yield a safe and uniform design that moreover can be associated with the design risk. This brief discusses a direct reliability method to be used for Eq. (11) in Subparagraphs NC and ND-3653.2 of the ASME B&PV Code for Class 2 and 3 pipes, respectively. A computational example illustrates the developed methodology.

A Reliability-Based Approach for Low-Cycle Fatigue Design of Class 2 and 3 Nuclear Piping

This paper presents a reliability-based low-cycle fatigue design approach for class 2 and 3 nuclear pipes. Initially, the methodology and background for the design of the pipes according to the ASME Boiler and Pressure Vessel (B&PV) Code is presented. Then a probabilistic design methodology based on the ASME B&PV Code and focused on straight pipes with butt-welds is presented. The method ensures an acceptable reliability level for piping by keeping the failure probability within some upper threshold and accounting for the uncertainties of the design variables. In opposition, the current design may result in diverse and often unknown probabilities of failure for piping. A computational example illustrates the developed method.

Impact of plastic softening of over-aged CuCrZr alloy heat sink tube on the structural reliability of a plasma-facing component

Precipitation-hardened CuCrZr alloy is used in fusion experiments as heat sink material for water-cooled plasma-facing components. When exposed to long-term high-heat-flux (HHF) plasma operation, CuCrZr will undergo over-ageing and thus plastic softening. In this situation, the softened CuCrZr heat sink tube will suffer from substantial plastic straining and thus fatigue damage in the course of the cyclic HHF loads. In this paper, a computational case study is presented regarding the cyclic plasticity behaviour of the over-aged CuCrZr cooling tube in a water-cooled tungsten mono-block divertor component. Finite element analysis was performed assuming ten typical HHF load cycles and using the Frederick–Armstrong constitutive equation together with corresponding material parameters. It was shown that plastic shakedown and low cycle fatigue (LCF) would be caused in the heat sink tube when softening of CuCrZr should occur. On the other hand, neither elastic shakedown nor cumulative plastic strain (ratchetting) was found. LCF design life of the CuCrZr tube was estimated based on the ITER materials handbook considering both hardened and softened states of CuCrZr. Substantial impact of softening of the CuCrZr alloy on the LCF lifetime of the heat sink tube was demonstrated.

AN ANALYSIS OF MEAN STRESS IN MULTIAXIAL RANDOM FATIGUE

Abstract— Generally engineering components are subjected to multiaxial variable amplitude loading, which may be non‐proportional. One of the best known low cycle fatigue design codes that addresses non‐proportional loading problems is the ASME Boiler and Pressure Vessel Code, but this does not include a cycle counting method and it does not allow for the presence of a mean stress. Traditional rainflow methods, incorporating a strain range and a mean stress, are applicable only where there is a single load varying with respect to time, or possibly where multiaxial loads are proportional. So a multiaxial non‐proportional cycle counting method and a fatigue damage calculation procedure are proposed here, based on plastic deformation response and a critical plane hypothesis that incorporates the effect of mean stress. A cyclic deformation model, based on the Ramberg‐Osgood equation and a multiaxial memory rule, is used to calculate the mean stress response under variable amplitude loading.The proposed procedure is assessed with combined tension/torsion tests on En15R steel under variable amplitude loading. Fatigue life predictions are compared for analysis with and without mean stress corrections, to assess the sensitivity to mean stresses of non‐proportional fatigue endurance in the low cycle regime.

Elastic-plastic finite element analysis of hollow tubes with axially loaded axisymmetric internal projections

The finite element method is used to study the monotonic and cyclic elastic-plastic stress and strain characteristics of hollow tubes with axisymmetric internal projections subjected to monotonic and repeated axial loading. Two geometries having low and high elastic stress concentration factors are considered in this investigation, and the results are complementary to previously published data. For cyclic loading, three simple material behaviour models, e.g., elastic-perfectly-plastic, isotropic hardening, and kinematic hardening are assumed. All results have been normalized with respect to material properties so that they can be applied to all geometrically similar components from other materials which may be represented by the same material models. Finally, normalized maximum monotonic strain and steady state strain range, predicted in the present investigation and from previously published data, are plotted as a function of the nominal load for different material hardening assumptions and different elastic stress concentration factors. These plots can be used in the low cycle fatigue design of such geometrically similar components.

Reliability-Based Consideration of ASME's Scatter Factor Used in Low-Cycle Fatigue Design Based on Geometrically Similar Model Tests

In the low-cycle fatigue design based on testing of geometrically similar models, the scatter of fatigue life is taken into account using the factor for the statistical variation in test results, Kss = 1.470 - 0.044γ, the formula given by the ASME Boiler and Pressure Vessel Code, where γ is the umber of replicate tests. In the present paper, this formula has been examined by calculating the upper confidence limit of the probability of failure PfU for the design service cycles as determined using the above formula. It was found that PfU varied with η and γ, where ηwas the coefficient of variation of the fatigue life. An alternative formula was proposed which made PfU independent of η and γ.

Reliability-based consideration of ASME's scatter factor used in low-cycle fatigue design based on geometrically similar model tests.

In the low-cycle fatigue design based on testing of geometrically similar models, the scatter of fatigue life is taken into account using the factor for the statistical variation in test results, Kss = 1.470 - 0.044γ, the formula given by the ASME Boiler and Pressure Vessel Code, where γ is the umber of replicate tests. In the present paper, this formula has been examined by calculating the upper confidence limit of the probability of failure PfU for the design service cycles as determined using the above formula. It was found that PfU varied with η and γ, where ηwas the coefficient of variation of the fatigue life. An alternative formula was proposed which made PfU independent of η and γ.

Fatigue Design Basis for Zircaloy Components

General methods have recently been developed for low-cycle fatigue design. The required basic strain-controlled data for both unirradiated and irradiated Zircaloy–2, −3, and −4 were obtained for te...