检索结果-南通市图书馆

An investigation on prevalent strategies for XFEM-based numerical modeling of crack growth in porous media

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2021年第4期15卷 914-936页

作者： Mohammad REZANEZHAD Seyed Ahmad LAJEVARDI Sadegh KARIMPOULI Mining Engineering Group Faculty of EngineeringUniversity of ZanjanZanjan45371-38791Iran Materials Engineering Group Faculty of EngineeringUniversity of ZanjanZanjan45371-38791Iran

crack growth modeling has always been one of the major challenges in fracture *** all numerical methods,the extended finite element method(XFEM)has recently attracted much attention due to its ability to estimate the discontinuous deformation ***,XFEM modeling does not directly lead to reliable results,and choosing a strategy of implementation is inevitable,especially in porous *** this study,two prevalent XFEM strategies are evaluated:a)applying reduced Young’s modulus to pores and b)using different partitions to the model and enriching each part *** mention the advantages and limitations of each strategy via both analytical and experimental ***,the crack growth is modeled in a natural porous media(Fontainebleau sandstone).Our investigations proved that although both strategies can identically predict the stress distribution in the sample,the first strategy simulates only the initial crack propagation,while the second strategy could model multiple cracks *** strategies are reliable and highly accurate in calculating the stress intensity factor,but the second strategy can compute a more reliable reaction *** tests showed that the second strategy is a more accurate strategy in predicting the preferred crack growth path and determining the maximum strength of the sample.

关键词： numerical modeling extended finite element method porous media crack growth stress intensity factor

Prediction of Cold Dwell-Fatigue crack growth of Titanium Alloys

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2015年第5期28卷 619-627页

作者： Ke Wang Fang Wang Wei-Cheng Cui A.-Li Tian School of Naval Architecture and Ocean Engineering Shanghai Jiao Tong University Hadal Science and Technology Research Center (Shanghai Engineering Research Center of Hadal Science and Technology) Shanghai Ocean University School of Naval Architecture and Ocean Engineering Jiangsu University of Science and Technology

The dwell effect of the material can reduce the fatigue lives of titanium alloys at room temperature. A unified fatigue life prediction method developed by the authors＇ group is modified in this paper to predict dwell-fatigue crack growth taking into account the effects of dwell time and maximum stress. The modified model can be successfully used to predict the crack growth rate and calculate the fatigue life of different titanium alloys under pure fatigue and dwell-fatigue conditions. It is validated by comparing prediction results with the experimental data of several titanium alloys with different microstructures, dwell time, hydrogen contents, stress ratios and stress levels.

关键词： Titanium alloy Dwell-fatigue Fatigue crack growth

Stress Corrosion crack growth Behavior of Titanium Alloy/Bioactive Glasses Sandwiches in Simulated Human Physiological Environment

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2002年第5期18卷 387-391页

作者： DaCHEN J.M.McNaney E.Saiz A.P.Tomsia R.O.Ritchie Dept. of Mat. Sci. Shanghai Jiaotong Univ. Shanghai 200030 China Dept. of Mat. Sci. and Eng. Univ. of California Berkeley CA 94720 United States Mat. Sci. Div. Lawrence Berkeley Natl. Lab. Berkeley CA 94720 United States

Based on a series of newly developed bioactive glasses having suitable thermo-mechanical properties to allow application as fixation agents between bone and titanium alloy biomedical implants, the stress corrosion crack growth (SCCG) behavior of their interfaces with Ti6AI4V was investigated in simulated body fluid (SBF) with the objective of discerning the salient mechanisms of crack advance and to assess the reliability of the bonds. Results indicated that crack growth rates in Ti6AI4V/glass/Ti6AI4V sandwich specimens were nearly the same as or slightly lower than those in the bulk glasses at comparable stress intensities; indeed, cracks would prefer to propagate off the interface, suggesting that the Ti6AI4V/glass interface has relatively good crack-growth resistance. Mechanistically, interfacial crack growth appears to be controlled by the classic stress corrosion mechanisms for silicate glasses, with no discernible effect of bioactivity on the SCCG behavior being observed.

关键词： Stress corrosion Titanium alloy Bioactive glass crack growth

Characteristics of crack growth in High Performance Concrete Subjected to Fire

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2005年第1期21卷 118-122页

作者： GaifeiPENG SammyYinNinCHAN JianhuaYAN YefengLIU QuanxinYI FacultyofCivilEngineering&Architecture BeijingJiaoTongUniversityBeijing100044China Wong&ChengConsultingEngineersLtd. HongKongChina BeijingUniversityofTechnology Beijing100022China

An experimental investigation was conducted to identify the characteristics of crack growth in high performance concrete (HPC) subjected to fire, including two parts of work, i.e. crack growth resistance determinations and cracking observations, using concrete of three strength grades 40 MPa, 70 MPa, and 110 MPa. The crack growth resistance curves (R-curves ) of HPC subjected to high temperatures were determined using notched three-point bend beam specimens of 100 mm×100 mm×300mm. The R-curve (crack growth resistance curve) flattening shows that the crack growth resistance has been significantly reduced by elevated temperature. Concrete with a higher strength grade has a steeper R-curve, with a higher fracture toughness but a shorter critical crack growth. The shorter critical crack growth means that concrete of a higher strength grade has a more brittle behavior. The concrete cracking observations reveal that the consequences of rapid heating are quite different from those of slow heating. For slow heating at a rate of 0.5℃/min, HPC suffered no obvious cracking below 600℃ even if it had a high moisture content. Explosive spalling is an extreme case of the internal cracking driven mainly by vapor pressure. All these results confirmed the vapor pressure mechanism for spading behavior which should be more significant for denser concrete. The crack growth ranges obtained from the R-curve determination results are in good agreement with those measured in the concrete cracking observations.

关键词： High performance concrete Fire resistance Explosive spoiling crack growth Vapor pressure

A NEW APPROACH TO PREDICTING INTERFACIAL crack growth

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 1997年第1期18卷 37-44页

作者：胡互让吴承平 Department of Mechanical Aerospace and Manufacturing Engineering Syracuse University Syracuse U.S.A. Chongqing Jiaotong Institute Chongqing P.R. China

A new approach, called β=0 approach is presented for use in the prediction ofinlerfocial crack growth. This approach is a kind of transformation. It transforms anoscillatory stress field to a nonoscillatory case by adjusting the elastic constants of thematerials involved. The interface toughness locus is also changed according to the newmaterial properties. It is shown that this approach will predict the exact same criticalload as interfacial fracture mechanics does. Finally several examples are presented toshow how to enforce β=0 while keeping the energy release rate unchanged.

关键词： interfacial crack crack growth β=0 approach critical load

Thermal shock resistance and crack growth behavior of Aurivillius phase Bi4Ti3O12-based ferroelectric ceramics

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2021年第2期31卷 248-254页

作者： Qian Xu Shaoxiong Xie Yu Chen Qingyuan Wang MOE Key Laboratory of Deep Earth Science and Engineering College of Architecture and Environment Sichuan University School of Mechanical Engineering Chengdu University College of Materials Science and Engineering Sichuan University

A type of W/Cr co-doped Bi4Ti3O12(ab. BTWC) ceramics were synthesized utilizing the traditional solid-state reaction process, and its thermal shock resistance(TSR) as well as the crack growth behavior was systematically investigated by water quenching technology. It can be found by the succeeded fractographic analysis that many edge thermal cracks began to appear in the samples subjected to thermal shock with ΔT=400°C. According to an integrated TSR model, the critical thermal-shock temperature difference ΔTCwas calculated to be 356°C. Moreover, it can be noticed that the indenter induced crack growth behaviors under thermal shock loads presented three stages, i.e. no growth, large growth, and moderate growth, along with ΔT increasing from 0°C to 700°C. Finally, the asymmetry of P-E hysteresis loops was observed and understood by the orientated polarization of defect dipoles after the sample was thermally shocked, while the water-quenching process above the Curie temperature of the ceramics could lead to a random orientation of the defect dipoles. This research can not only evaluate the service conditions of Bi4Ti3O12high-temperature piezoceramics, but also understand the failure mechanism of bismuth layer structured ferroelectric ceramics in the case of thermal shock.

关键词： Bi 4 Ti 3 O 12 ceramics TSR crack growth Temperature difference

NUMERICAL SIMULATION OF crack growth IN BRITTLE MATRIX OF PARTICLE REINFORCED COMPOSITES USING THE XFEM TECHNIQUE

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2012年第1期25卷 9-21页

作者： Zhiyong Wang Li Ma Linzhi Wu Hongjun Yu Center for Composite Materials Harbin Institute of TechnologyHarbin 150001China

crack growth in particle reinforced composites is significantly influenced by the character of the reinforcement *** accurately deal with such problems,the extended finite element method （XFEM） was employed and *** simulations are accomplished by using a new domain expression of an interaction integral for evaluating stress intensity factors （SIFs）,and by adopting the maximum hoop stress criterion for crack-growth direction *** deflection/attraction mechanisms and their associated energy release rate variations are *** is shown that the applied numerical method allows a considerable flexibility and can be used in more general *** crack-tip shielding and amplifying behaviors are clearly observed.

关键词： crack growth energy release rate crack-tip shielding and amplifying extended finite element method

EFFECT OF GRAIN BOUNDARY CARBIDE ON CREEP crack growth IN Fe-Cr15-Ni25 ALLOY

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 1992年第1期5卷 48-51页

作者： Wang Fugang Zhu Suming Zhu Shijie Ren Xiaomin Tan Yi Zhang Junshan Dalian Univ of Technology Dalian China

Creep crack growth behavior of Fe-Cr15-Ni25 alloys with different grain boundary features has been *** nucleate at triple junctions of grain boundaries for the single phase alloy and at grain boundary carbide for the alloy with grain boundary *** bounda- ry carbide particles are obstacles to cavity growth and coalescence,and therefore increase the creep crack growth resistance greatly.

关键词： creep crack growth grain boundary carbide cavity Fe-Cr15-Ni25 alloy

EFFECTS OF STRESS RATIO AND FREQUENCY ON CORROSION FATIGUE crack growth MECHANISM IN LOW ALLOY STEELS

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 1993年第6期6卷 373-378页

作者： HAN Enhou HAN KYumei ZHENG Yuli KE Wei Corrosion Science Laboratory,Institute of Corrosion and Protection of Metals,Academia Sinica,Shenyang,China postdoctoral,Institute of Corrosion and Protection of Metals,Academia Sinica,Shenyang 110015,China Inst of Corrosion and Protection of Metals Shenyang China

Based on theoretical analysis about local strain,strain rate and dissolving rate at crack tip, the corrosion fatigue crack growth rate of steels ZG20SiMn and SM50B-Zc in fresh water and 3.5% NaCl solution were measured experimentally,and the PH and electrode potential within crack were also measured continuously along with crack *** showed that the increase of crack growth rate,caused by both decreasing frequency and raising stress ratio,was mainly accelerated by hydrogen embrittlement.

关键词： corrosion fatigue stress ratio crack growth electrode potential steel ZG20SiMn steel SM50B-Zc