Effect of local wall thinning on ratcheting behavior of pressurized 90° elbow pipe under reversed bending using finite element analysis

Xiaohui Chen,Xu Chen 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.4

Ratcheting deformation of pressurized Z2CND18.12N stainless steel 90° elbow pipe with local wall thinning subjected to constant internal pressure and reversed bending was studied using finite element analysis. Chen-Jiao-Kim (CJK) kinematic hardening model, which was used to simulate ratcheting behavior of pressurized 90° elbow pipe with local wall thinning at extrados, flanks and intrados, was implemented into finite element software ANSYS. The local wall thinning was located at extrados, flanks and intrados of 90° elbow pipe, whose geometry was rectangular cross-section. The effect of depth, axial length and circumferential angle of local wall thinning at extrados, flanks and intrados on the ratcheting behaviors of 90° elbow pipe were studied in this paper. Threedimensional elastic-plastic analysis with Chen-Jiao-Kim (CJK) kinematic hardening model was carried out to evaluate structural ratcheting behaviors. The results indicated that ratcheting strain was generated mainly along the hoop direction, while axial ratcheting strain was relatively small.

Influence of stress level on uniaxial ratcheting effect and ratcheting strain rate in austenitic stainless steel Z2CND18.12N

Xiaohui Chen,Xu Chen,Haofeng Chen 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.1

Uniaxial ratcheting behavior of Z2CND18.12N austenitic stainless steel used nuclear power plant piping material was studied. The results indicated that ratcheting strain increased with increasing of stress amplitude under the same mean stress and different stress amplitude, ratcheting strain increased with increasing of mean stress under the same stress amplitude and different mean stress. Based on least square method, a suitable method to arrest ratcheting by loading the materials was proposed, namely determined method of zero ratcheting strain rate. Zero ratcheting strain rate occur under specified mean stress and stress amplitudes. Moreover, three dimensional ratcheting boundary surface graph was established with stress amplitude, mean stress and ratcheting strain rate. This represents a graphical surface zone to study the ratcheting strain rates for various mean stress and stress amplitude combinations. The graph showed the ratcheting behavior under various combinations of mean and amplitude stresses. The graph was also expressed with the help of experimental results of certain sets of mean and stress amplitude conditions. Further, experimentation cost and time can be saved.

Limit load, shakedown and ratchet analysis of pressurized lateral nozzle

Xiaohui Chen,Kunmin Zhuang,Xuanchen Zhu,Haofeng Chen 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.3

This paper evaluates the limit load, shakedown limit and ratchet limit of the oblique nozzle based on the linear matching method (LMM). In order to study the influencing factors of the limit load, shakedown limit and ratchet limit of the oblique nozzle, oblique nozzle models with different dip angles, diameter-to-thickness ratios of the oblique nozzle and diameterto- thickness ratios of the main pipe are established, respectively. Firstly, the limit load, shakedown limit and ratchet limit of the oblique nozzle are studied. At the same time, the influence of the loading mode on the shakedown limit and ratchet limit is also studied. Secondly, oblique nozzles with different defect lengths, widths and depths are established, respectively. The influence of loading paths on shakedown limit and ratchet limit of oblique nozzles with defects are also studied. Finally, shakedown limit and ratchet limit diagrams are obtained based on linear matching method. The correctness of shakedown limit and ratchet limit diagrams is validated by ABAQUS incremental elastic-plastic analysis.

Ratcheting boundary of pressurized pipe under reversed bending

Xiaohui Chen,Xu Chen,Zifeng Li 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.3

Ratcheting boundary is firstly determined by experiment, elastic-plastic finite element analysis combined with C-TDF and linear matching method, which is compared with ASME/KTA and RCC-MR. Moreover, based on elastic modulus adjustment procedure, a novel method is proposed to predict the ratcheting boundary for a pressurized pipe subjected to constant internal pressure and cyclic bending loading. Comparison of ratcheting boundary of elbow pipe determined by the proposed method, elastic-plastic finite element analysis combined with C-TDF and linear matching method, which indicates that the predicted results of the proposed method are in well agreement with those of linear matching method.

Ratcheting assessment of austenitic steel samples at room and elevated temperatures through use of Ahmadzadeh-Varvani Hardening rule

Xiaohui Chen,Lang Lang,Hongru Liu 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.87 No.6

In this study, the uniaxial ratcheting effect of Z2CND18.12N austenitic stainless steel at room and elevated temperatures is firstly simulated based on the Ahmadzadeh-Varvani hardening rule (A-V model), which is embedded into the finite element software ABAQUS by writing the user material subroutine UMAT. The results show that the predicted results of A-V model are lower than the experimental data, and the A-V model is difficult to control ratcheting strain rate. In order to improve the predictive ability of the A-V model, the parameter γ2 of the A-V model is modified using the isotropic hardening criterion, and the extended A-V model is proposed. Comparing the predicted results of the above two models with the experimental data, it is shown that the prediction results of the extended A-V model are in good agreement with the experimental data.

Evaluation of limit load analysis for pressure vessels ‒ Part I: Linear and nonlinear methods

Xiaohui Chen,Bingjun Gao,Xingang Wang 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.6

Limit load of pressure bearing structures was reviewed in this article. By means of the finite element analysis, limit load of pressurized cylinder with nozzle was taken as an example. Stress classification method and Elastic-plastic finite element analysis combining with limit load determination methods were used to determine limit load of cylinder with nozzle. Comparison of limit load determined by different methods, the results indicated that limit load determined by linearization method was the smallest. Limit load determined by twice elastic slope criterion was the nearest than experimental results. Elastic-plastic finite element analysis had comparably computational precision, but required time consuming. And then the requirements of computer processing and storage capacity by power system became higher and higher. Most of criteria for limit load estimation included any human factors based on a certain substantive characteristics of experimental results. The reasonable criterion should be objective and operational.

Evaluation of limit load analysis for pressure vessels — Part II: Robust methods

Xiaohui Chen,Bingjun Gao,Xingang Wang 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.1

Determining limit load for a pressure bearing structure using elastic-plastic finite element analysis was computationally very expensive. A series of robust methods using elastic modulus adjustment techniques (EMAP) to identify the limit load directly were proposed. The numerical implementation of the robust method had the potential to be an attractive alternative to elastic-plastic finite element analysis since it was simple, and required less computational effort and computer storage space. Another attractive feature was that the method provided a go/no go criterion for the limit load, whereas the results of an elastic-plastic analysis were often difficult to interpret near the limit load since it came from human sources. To explore the performance of the method further, it was applied to a number of configurations that include two-dimensional and threedimensional effects. In this study, limit load of cylinder with nozzle was determined by the robust methods.

Evaluation of AF type cyclic plasticity models in ratcheting simulation of pressurized elbow pipes under reversed bending

Xiaohui Chen,Bingjun Gao,Xu Chen 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.4

The ratcheting behavior was studied experimentally for Z2CND18.12N elbow piping under cyclic bending and steady internal pressure. Dozens of cyclic plasticity models for structural ratcheting responses simulations were used in the paper. The four models, namely, Bilinear (BKH), Multilinear (MKIN/KINH), Chaboche (CH3), were already available in the ANSYS finite element package. Advanced cyclic plasticity models, such as, modified Chaboche (CH4), Ohno-Wang, modified Ohno-Wang, Abdel Karim-Ohno and modified Abdel Karim-Ohno, were implemented into ANSYS for simulating the experimental responses. Results from the experimental and simulation studies were presented in order to demonstrate the state of structural ratcheting response simulation by these models. None of the models evaluated perform satisfactorily in simulating circumferential strain ratcheting response. Further, improvement in cyclic plasticity modeling and incorporation of material and structural features, like time-dependent, temperature-dependent, non-proportional, dynamic strain aging, residual stresses and anisotropy of materials in the analysis would be essential for advancement of low-cycle fatigue simulations of structures.

Bone Homeostasis and Gut Microbial-Dependent Signaling Pathways

( Xiaohui Zhong ),( Feng Zhang ),( Xinyao Yin ),( Hong Cao ),( Xuesong Wang ),( Dongsong Liu ),( Jing Chen ),( Xue Chen ) 한국미생물생명공학회(구 한국산업미생물학회) 2021 Journal of microbiology and biotechnology Vol.31 No.6

Although research on the osteal signaling pathway has progressed, understanding of gut microbialdependent signaling pathways for metabolic and immune bone homeostasis remains elusive. In recent years, the study of gut microbiota has shed light on our understanding of bone homeostasis. Here, we review microbiota-mediated gut-bone crosstalk via bone morphogenetic protein/SMADs, Wnt and OPG/receptor activator of nuclear factor-kappa B ligand signaling pathways in direct (translocation) and indirect (metabolite) manners. The mechanisms underlying gut microbiota involvement in these signaling pathways are relevant in immune responses, secretion of hormones, fate of osteoblasts and osteoclasts and absorption of calcium. Collectively, we propose a signaling network for maintaining a dynamic homeostasis between the skeletal system and the gut ecosystem. Additionally, the role of gut microbial improvement by dietary intervention in osteal signaling pathways has also been elucidated. This review provides unique resources from the gut microbial perspective for the discovery of new strategies for further improving treatment of bone diseases by increasing the abundance of targeted gut microbiota.

Effects of temperature on the ratcheting behavior of pressurized 90 elbow pipe under force controlled cyclic loading

Xiaohui Chen,Xingang Wang,Xu Chen 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.5

Ratcheting behavior of 90 elbow piping subject to internal pressure 20 MPa and reversed bending 20 kN was investigated using experimental method. The maximum ratcheting strain was found in the circumferential direction of intrados. Ratcheting strain at flanks was also very large. Moreover, the effect of temperature on ratcheting strain of 90 elbow piping was studied through finite element analysis, and the results were compared with room condition (25). The results revealed that ratcheting strain of 90 elbow piping increased with increasing temperature. Ratcheting boundary of 90 elbow piping was determined by Chaboche model combined with C-TDF method. The results revealed that there was no relationship between the dimensionless form of ratcheting boundary and temperature.