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Microstructural evolution and restoration of creep property for a damaged K403 alloy after rejuvenation heat treatments

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Rare Metals 2021年第7期40卷 1865-1871页

作者： Liang Wang Xiao-Guang Yang Hong-Yu qi duo-qi shi Shao-Lin Li School of Energy and Power Engineering Beihang UniversityBeijing 100191China Beijing Key Laboratory of Aero-Engine Structure and Strength Beijing 100191China

Rejuvenation heat treatments can restore the microstructures and mechanical properties of the degraded turbine blades in gas turbine *** we analyze the effects of rejuvenation heat treatments on the microstructural characteristics and mechanical properties of damaged and undamaged specimens of a Ni-based superalloy,*** damaged specimens were found to have degraded microstructures and shorter creep lifetime than the undamaged *** rejuvenation heat treatment proved beneficial,especially for specimens exposed to damage for 50 *** addition,the microstructure recovery and creep life were found to depend on the predamage durations of the specimens.A y’-precipitate-based creep lifetime model was established to predict the residual lifetime based on the microstructural information.

关键词： Microstructural evolution Creep property Restoration Rejuvenation heat treatments

Low-cycle fatigue behavior of DZ125 superalloy under prior exposure conditions

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Rare Metals 2023年第6期42卷 2028-2036页

作者： Hong-Yu qi Xiao-Lei Zheng Li-qiang Ma Shao-Lin Li Xiao-Guang Yang duo-qi shi School of Energy and Power Engineering Beihang UniversityBeijing100191China Collaborative Innovation Center of Advanced Aero-Engine Beijing100191China Shenyang Engine Design and Research Institute Aviation Industry Corporation of ChinaShenyang110015China

Low-cycle fatigue(LCF) behavior of the directionally solidified(DS) nickel-based DZ125 superalloy was studied at elevated temperature(980 ℃).Specimens were,respectively,exposed for 0,2,25,50,and 100 h in *** fatigue life of pre-exposed specimens is lower than that of unexposed *** result is closely associated with fatigue crack initiation and propagation due to oxygen embrittlement and cycle *** fractographic evaluations indicate the fatigue life is closely related to the surface microstructural *** resulting changes in microstructure cause the decrease in the effective area and the increase in actual stress.A methodology based on the continuum damage mechanics is developed to describe the correlation between the residual LCF life and pre-exposed time.

关键词： Nickel-based superalloy Oxidation Prior exposure Low-cycle fatigue Continuum damage mechanics

Constitutive modeling of a directionally solidified nickel-based superalloy DZ125 subjected to thermal mechanical creep fatigue loadings

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Rare Metals 2019年第10期38卷 922-936页

作者： Xiao-An Hu Xiao-Guang Yang duo-qi shi Hui-Chen Yu Ting-Ting Ren School of Energy and Power Engineering Beihang UniversityBeijing 100191China Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical MaterialsBeijing 100095China Air Force Armament Department China Aviation MuseumBeijing 102211China

A transversely isotropic continuum elasto-viscoplasticity model,which was developed from Chaboche’s unified constitutive model,was formulated to capture the thermal mechanical creep fatigue deformation behavior of a directionally solidified nickel-based superalloy.A fourthorder tensor was introduced to model material *** order to model the tertiary creep behavior,the Kachanov damage evolution equation was coupled into the stress *** on the test results of uniaxial tensile,fatigue,and creep loadings at isothermal temperature conditions,the material parameters are *** mechanical fatigue(TMF) and creep-fatigue interaction test results were used to verify the robustness of the ***,strain-temperature-dependent stress-strain responses under TMF loadings were analyzed using the present *** strain-controlled conditions,both of the stress ranges and mean stresses are strongly influenced by the strain-temperature phases,a key parameter for TMF tests.

关键词： Constitutive Thermal mechanical fatigue Creep Viscoplastic Superalloy

Fatigue response,fracture characteristic and life modeling of a near-alpha titanium alloy under typical cyclic loadings in service

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Rare Metals 2016年第9期35卷 676-685页

作者： Jia Huang Yin-Yin Luo Peng-Tao Zhao duo-qi shi Xiao-Guang Yang Hui-Chen Yu School of Energy and Power Engineering Beihang UniversityBeijing 100191China Shanghai Electric Power Equipment Co. Ltd.Shanghai Steam Turbine FactoryShanghai 200240China Beijing Institute of Aeronautical Materials Beijing 100095China

Experimental investigations on the fatigue behavior of a near-alpha titanium alloy under typical cyclic loadings were carried out to simulate the service loading states applied on the engine *** axial stress-controlled tension–tension low-cycle fatigue（LCF） tests were carried out over a range of maximum stresses and stress *** rotary bending tests were conducted using a step-loading procedure to reveal the high-cycle fatigue（HCF） limit *** cyclic softening effect is observed in this material,and the strain ratcheting occurs obviously at the maximum LCF loading of 900 *** LCF resistance is found to be dependent on both the maximum loading and the stress *** HCF limit stresses for 1 9 107 and 1 9 106 cycles are determined as405.7 and 457.6 MPa,*** macroscopic fatigue fracture mode and the failure features on fracture surfaces were analyzed by scanning electron microscope（SEM）.

关键词： Titanium alloy High-cycle fatigue Lowcycle fatigue Fracture analysis Ratcheting

Natural product-induced oxidative stress-synergistic anti-tumor effects of chemotherapeutic agents

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Traditional Medicine Research 2024年第3期9卷 10-23页

作者： Shu-Fan Wang shi-qi Dong Quan Dong Wen-Xin Lin Mei Dong duo Liu Department of Pharmacy Harbin Medical University Cancer HospitalHarbin 150086China

Reactive oxygen species are closely related to tumor *** recent years,reactive oxygen species has become a hot spot in tumor therapy,and many natural substances in nature contain compound components with anti-tumor ***,there is a lack of discussion on the synergistic anti-tumor effects of natural products in combination with chemotherapeutic drugs through reactive oxygen *** terms“natural products”,“reactive oxygen species”,“anti-tumor”,and“chemotherapy”were used to identify the synergistic effects of natural *** conducted a systematic literature search in PubMed and Web of Science databases for relevant research articles and reviews published in recent *** systematically summarized the studies related to anti-tumor active ingredients in natural compounds in the field of reactive oxygen species in recent years.A total of 77 relevant literatures were *** them,45 literatures containing various natural products such as terpenoids,flavonoids,alkaloids,*** anti-tumor effects by regulating reactive oxygen species levels,and 32 literatures regarding adjunctive role of natural products in anti-tumor *** this study,we found that natural products exert anti-tumor effects by elevating reactive oxygen species *** provides strong theoretical support for future clinical studies.

关键词： nature products tumor reactive oxygen species combination chemotherapy oxidative stress

Buckling optimization of curvilinear fiber-reinforced composite structures using a parametric level set method

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Frontiers of Mechanical Engineering 2024年第1期19卷 149-160页

作者： Ye TIAN Tielin shi qi XIA State Key Laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China

Owing to their excellent performance and large design space,curvilinear fiber-reinforced composite structures have gained considerable attention in engineering fields such as aerospace and *** addition to the stiffness and strength of such structures,their stability also needs to be taken into account in the *** study proposes a level-set-based optimization framework for maximizing the buckling load of curvilinear fiber-reinforced composite *** the proposed method,the contours of the level set function are used to represent fiber *** a composite laminate with a certain number of layers,one level set function is defined by radial basis functions and expansion coefficients for each ***,the fiber angle at an arbitrary point is the tangent orientation of the contour through this *** the finite element of buckling,the stiffness and geometry matrices of an element are related to the fiber angle at the element *** study considers the parallelism constraint for fiber *** the sensitivity calculation of the objective and constraint functions,the method of moving asymptotes is utilized to iteratively update all the expansion coefficients regarded as design *** numerical examples under different boundary conditions are given to validate the proposed *** show that the optimized curved fiber paths tend to be parallel and equidistant regardless of whether the composite laminates contain holes or ***,the buckling resistance of the final design is significantly improved.

关键词： buckling optimization curvilinear fiber composite structure level set method manufacturing constraint

An M-VCUT level set-based data-driven model of microstructures and optimization of two-scale structures

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Frontiers of Mechanical Engineering 2024年第4期19卷 73-86页

作者： Minjie SHAO Tielin shi qi XIA State Key Laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China

The optimization of two-scale structures can adapt to the different needs of materials in various regions by reasonably arranging different microstructures at the macro scale,thereby considerably improving structural ***,a multiple variable cutting(M-VCUT)level set-based data-driven model of microstructures is presented,and a method based on this model is proposed for the optimal design of two-scale *** geometry of the microstructure is described using the M-VCUT level set method,and the effective mechanical properties of microstructures are computed by the homogenization ***,a database of microstructures containing their geometric and mechanical parameters is *** two sets of parameters are adopted as input and output datasets,and a mapping relationship between the two datasets is established to build the data-driven model of *** the optimization of two-scale structures,the data-driven model is used for macroscale finite element and sensitivity *** efficiency of the analysis and optimization of two-scale structures is improved because the computational costs of invoking such a data-driven model are much smaller than those of homogenization.

关键词： two-scale structure structural optimization M-VCUT level set homogenization radial basis function data-driven

Coupled effects of climate change and human activities on vegetation dynamics in the Southwestern Alpine Canyon Region of China

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Journal of Mountain Science 2024年第10期21卷 3234-3248页

作者： LAI Jinlin qi shi School of Soil and Water Conservation Beijing Forestry UniversityBeijing 100083China

The driving effects of climate change and human activities on vegetation change have always been a focal point of ***,the coupling mechanisms of these driving factors across different temporal and spatial scales remain *** Southwestern Alpine Canyon Region of China(SACR),as an ecologically fragile area,is highly sensitive to the impacts of climate change and human *** study constructed a vegetation cover dataset for the SACR based on the Enhanced Vegetation Index(EVI)from 2000 to *** autocorrelation,Theil-Sen trend,and Mann-Kendall tests were used to analyze the spatiotemporal characteristics of vegetation cover *** main drivers of spatial heterogeneity in vegetation cover were identified using the optimal parameter geographic detector,and an improved residual analysis model was employed to quantify the relative contributions of climate change and human activities to interannual vegetation cover *** main findings are as follows:Spatially,vegetation cover exceeds 60%in most areas,especially in the southern part of the study ***,the border area between Linzhi and Changdu exhibits lower vegetation *** factors are the primary drivers of spatial heterogeneity in vegetation cover,with temperature having the most significant influence,as indicated by its q-value,which far exceeds that of other ***,the interaction q-value between the two factors significantly increases,showing a relationship of bivariate enhancement and nonlinear *** terms of temporal changes,vegetation cover shows an overall improving trend from 2000 to 2020,with significant increases observed in 68.93%of the study *** these,human activities are the main factors driving vegetation cover change,with a relative contribution rate of 41.31%,while climate change and residual factors contribute 35.66%and 23.53%,*** thoroughly exploring the coupled mechanisms of vegetation change,this

关键词： Enhanced vegetation index Climate change Human activities Spatial heterogeneity Coupled mechanisms

Novel milestones for early esophageal carcinoma:From bench to bed

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World Journal of Gastrointestinal Oncology 2024年第4期16卷 1104-1118页

作者： Ji-Han qi shi-Ling Huang shi-Zhu Jin Department of Gastroenterology and Hepatology The Second Affiliated Hospital of Harbin Medical UniversityHarbin 150086Heilongjiang ProvinceChina

Esophageal cancer(EC)is the seventh most common cancer worldwide,and esophageal squamous cell carcinoma(ESCC)accounts for the majority of cases of *** effectively diagnose and treat ESCC and improve patient prognosis,timely diagnosis in the initial phase of the illness is *** article offers a detailed summary of the latest advancements and emerging technologies in the timely identification of *** biology and epigenetics approaches involve the use of molecular mechanisms combined with fluorescence quanti-tative polymerase chain reaction(qPCR),high-throughput sequencing technology(next-generation sequencing),and digital PCR technology to study endogenous or exogenous biomolecular changes in the human body and provide a decision-making basis for the diagnosis,treatment,and prognosis of *** invest-igation of the microbiome is a swiftly progressing area in human cancer research,and microorganisms with complex functions are potential components of the tumor *** intratumoral microbiota was also found to be connected to tumor *** application of endoscopy as a crucial technique for the early identification of ESCC has been essential,and with ongoing advancements in technology,endoscopy has continuously *** the advancement of artificial intelligence(AI)technology,the utilization of AI in the detection of gastrointestinal tumors has become increasingly *** implementation of AI can effectively resolve the discrepancies among observers,improve the detection rate,assist in predicting the depth of invasion and differentiation status,guide the pericancerous margins,and aid in a more accurate diagnosis of ESCC.

关键词： Early esophageal squamous cell carcinoma Epidemiology and risk factors Molecular biology Epigenetic Microbiology Endoscopy and artificial intelligence