A path-dependent fatigue crack propagation model under non-proportional modes I and III loading conditions

Mei, J.,Dong, P.,Kalnaus, S.,Jiang, Y.,Wei, Z. Pergamon Press 2017 Engineering fracture mechanics Vol.182 No.-

<P><B>Abstract</B></P> <P>It has been well established that fatigue damage process is load-path dependent under non-proportional multi-axial loading conditions. Most of studies to date have been focusing on interpretation of S-N based test data by constructing a path-dependent fatigue damage model. This paper presents a two-parameter mixed-mode fatigue crack growth model which takes into account of crack growth dependency on both load path traversed and a maximum effective stress intensity attained in a stress intensity factor plane ( e . g . , <SUB> K I </SUB> - <SUB> K III </SUB> plane). By taking advantage of a path-dependent maximum range (PDMR) cycle definition (Dong et al., 2010; Wei and Dong, 2010), the two parameters are formulated by introducing a moment of load path (MLP) based equivalent stress intensity factor range ( Δ <SUB> K NP </SUB> ) and a maximum effective stress intensity parameter <SUB> K Max </SUB> incorporating an interaction term <SUB> K I </SUB> · <SUB> K III </SUB> . To examine the effectiveness of the proposed model, two sets of crack growth rate test data are considered. The first set is obtained as a part of this study using 304 stainless steel disk specimens subjected to three combined non-proportional modes I and III loading conditions (i.e., with a phase angle of 0°, 90°, and 180°). The second set was obtained by Feng et al. (2007) using 1070 steel disk specimens subjected to similar types of non-proportional mixed-mode conditions. Once the proposed two-parameter non-proportional mixed-mode crack growth model is used, it is shown that a good correlation can be achieved for both sets of the crack growth rate test data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Presented a two-parameter mixed-mode fatigue crack growth model. </LI> <LI> Both load path dependency and mean stress effect are considered. </LI> <LI> Validated by non-proportional mixed mode I and III crack growth tests on 304 steel. </LI> <LI> Good correlations are achieved both for test data obtained in this study and from others. </LI> </UL> </P>

Structural health monitoring-based dynamic behavior evaluation of a long-span high-speed railway bridge

Mei, D.P. Techno-Press 2017 Smart Structures and Systems, An International Jou Vol.20 No.2

The dynamic performance of railway bridges under high-speed trains draws the attention of bridge engineers. The vibration issue for long-span bridges under high-speed trains is still not well understood due to lack of validations through structural health monitoring (SHM) data. This paper investigates the correlation between bridge acceleration and train speed based on structural dynamics theory and SHM system from three foci. Firstly, the calculated formula of acceleration response under a series of moving load is deduced for the situation that train length is near the length of the bridge span, the correlation between train speed and acceleration amplitude is analyzed. Secondly, the correlation scatterplots of the speed-acceleration is presented and discussed based on the transverse and vertical acceleration response data of Dashengguan Yangtze River Bridge SHM system. Thirdly, the warning indexes of the bridge performance for correlation scatterplots of speed-acceleration are established. The main conclusions are: (1) The resonance between trains and the bridge is unlikely to happen for long-span bridge, but a multimodal correlation curve between train speed and acceleration amplitude exists after the resonance speed; (2) Based on SHM data, multimodal correlation scatterplots of speed-acceleration exist and they have similar trends with the calculated formula; (3) An envelope line of polylines can be used as early warning indicators of the changes of bridge performance due to the changes of slope of envelope line and peak speed of amplitude. This work also gives several suggestions which lay a foundation for the better design, maintenance and long-term monitoring of a long-span high-speed bridge.

Occurrence of Diadegma semiclausum, a parasitoid of diamondback moth in lowlands of Syria

P. Kadirvel,R. Srinivasan,Lin Mei-ying,Ebraheem Al-Jouri,M. Walid Idraw,R.C. de la Peña 한국응용곤충학회 2011 Journal of Asia-Pacific Entomology Vol.14 No.1

The parasitoid, Diadegma semiclausum (Hymenoptera: Ichneumonidae) is one of the most effective parasitoids of diamondback moth (DBM) in the highlands (N1600 mabove sea level) of Asia. A Diadegma population from the lowland areas of Homs, Syria (about 203–487 m above sea level) was examined to determine if it differs at the species-level from the D. semiclausum and other Diadegma populations present in different countries using molecular diagnostic tools. Phylogenetic analysis based on the neighbor-joining method using the mitochondrial cytochrome oxidase I (COI) and the nuclear internal transcribed spacer 2 (ITS2) sequences grouped the Homs (Syria) Diadegma population with D. semiclausum populations from other countries. The results suggest that D. semiclausum occurs in the lowland conditions in Homs (Syria), where the temperature is higher. The Homs (Syria) strain did not show any variations in the parasitism when the parasitized host (DBM)larvae were exposed to varying temperatures for 24 h. It could not survive when the parasitized DBM larvae were continuously reared at 35 °C; however it inflicted significantly higher parasitism when the parasitized DBM larvae were reared at day and night temperatures of 35 °C and 20 °C, respectively. Preliminary results indicate that the D. semiclausum strain from Homs (Syria) possesses some level of heat tolerance, which could be exploited for successful management of DBM in the tropical lowlands.

Participation of GATA-3 in regulation of bone healing through transcriptional upregulation of bcl-xL expression

Mei-Hsiu Liao,Pei-I Lin,Wei-Pin Ho,Wing P Chan,Ta-Liang Chen,Ruei-Ming Chen 생화학분자생물학회 2017 Experimental and molecular medicine Vol.49 No.-

We have previously demonstrated the expression of GATA-DNA-binding protein (GATA)-3, a transcription factor, in osteoblasts and have verified its function in transducing cell survival signaling. This translational study was further designed to evaluate the roles of GATA-3 in regulating bone healing and to explore its possible mechanisms. A metaphyseal bone defect was created in the left femurs of male ICR mice. Analysis by micro-computed topography showed that the bone volume, trabecular bone number and trabecular thickness were augmented and that the trabecular pattern factor decreased. Interestingly, immunohistological analyses showed specific expression of GATA-3 in the defect area. In addition, colocalized expression of GATA-3 and alkaline phosphatase was observed at the wound site. As the fracture healed, the amounts of phosphorylated and non-phosphorylated GATA-3 concurrently increased. Separately, GATA-3 mRNA was induced during bone healing, and, levels of Runx2 mRNA and protein were also increased. The results of confocal microscopy and co-immunoprecipitation showed an association between nuclear GATA-3 and Runx2 in the area of insult. In parallel with fracture healing, Bcl-XL mRNA was significantly triggered. A bioinformatic search revealed the existence of a GATA-3-specific DNA-binding element in the promoter region of the bcl-xL gene. Analysis by chromatin immunoprecipitation assays further demonstrated transactivation activity by which GATA-3 regulated bcl-xL gene expression. Therefore, this study shows that GATA-3 participates in the healing of bone fractures via regulating bcl-xL gene expression, owing to its association with Runx2. In the clinic, GATA-3 may be used as a biomarker for diagnoses/prognoses or as a therapeutic target for bone diseases, such as bone fractures.

An equivalent stress parameter for multi-axial fatigue evaluation of welded components including non-proportional loading effects

Mei, J.,Dong, P. IPC Science and Technology Press ; Elsevier Scienc 2017 International journal of fatigue Vol.101 No.2

This paper presents a comprehensive investigation into non-proportional multi-axial fatigue of welded components by introducing an equivalent structural stress parameter that takes into account of load-path non-proportionality in addition to plate thickness and stress state effects. This is accomplished by formulating a ''moment of load path'' or ''MLP'' based fatigue damage parameter that provides a consistent treatment of load-path non-proportionality under arbitrary multi-axial loading conditions for which cycle counting can be consistently performed by means of a previously developed path-dependent maximum range (PDMR) cycle counting procedure. To examine its broad applicability and effectiveness, non-proportional multi-axial test data obtained using different components, joint types, and loading conditions from various sources are analyzed using the newly developed equivalent stress parameter. The results show that the new equivalent stress parameter enables not only an effective consolidation of all multi-axial test data (up to about 300 tests) analyzed in this paper into a narrow band, but also the demonstrated transferability between the master S-N curve (dominated by test data under uniaxial cyclic loading conditions) adopted by the 2007 ASME Div 2 and API 579 RP/ASME FFS-1 Codes and the consolidated S-N curve dominated by severe non-proportional multi-axial cyclic loading conditions. As a result of the present development, a unified fatigue evaluation procedure based on the newly proposed effective stress parameter and a single master S-N curve can be implemented for arbitrary cyclic loading conditions regardless of stress multi-axiality or load path proportionality.

Application of Slow-Freezing Cryopreservation Method for the Conservation of Diverse Potato (Solanum tuberosum L.) Genotypes

Zhao Mei-Ai,Dhital Shambhu P.,Fang Yi-Lan,Khu Dong-Man,Song Ye-Su,Park Eung-Jun,Kang Chang-Won,Lim Hak-Tae The Korean Society of Plant Biotechnology 2005 Plant molecular biology and biotechnology research Vol.7 No.3

Cryopreservation has been recognized as a practical and efficient tool for the long-term storage of vegetatively propagated plants. This study was conducted to investigate the effects of slow-freezing techniques on the cryopreservation of potato. In vitro plantlets of the potato genotypes of 'Atlantic', 'Superior’, 'Namseo', 'J138', and 'CTO5-5' were cold acclimated, and the excised axillary buds were precultured, osmoprotected, exposed to plant vitrification solution, frozen slowly to $-40^{\circ}C$ and then rapidly plunged into liquid nitrogen, thawed and finally plated on the regeneration medium. It was found that the higher the sucrose concentrations in the subculture medium of donor plantlets, the higher the survival rates of shoot tips after cryopreservation, and the highest survival (20%) was observed in the medium added with 0.25 M sucrose. As for the effect of cooling, $0.3^{\circ}C/min$ cooling speed showed the highest survival (25%). Different varieties showed different responses over different cryopreservation treatments. Survival rate was increased by slow-freezing technique method as compared with that of the basic cryopreservation method of vitrification alone in the diverse potato genotypes. Leaf and tuber morphologies of potatoes regenerated after cryopreservation using slow freezing technique were similar to those derived from the in vitro stock plantlets.

Lattices with internal resonator defects

Hauver, S.,He, X.,Mei, D.,Charalampidis, E. G.,Kevrekidis, P. G.,Kim, E.,Yang, J.,Vainchtein, A. American Physical Society 2018 Physical Review E Vol.98 No.3

Fire performance of edge and interior circular steel-reinforced concrete-filled steel tubular stub columns

Fan-Qin Meng,Mei-Chun Zhu,G. Charles Clifton,Kingsley U. Ukanwa,James B.P. Lim 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.1

The steel-reinforced concrete-filled steel tubular column (SRCFT) is a new form of composite columns. Before widely accepted in engineering practice, its fire behaviour shall be fully understood. Four representative circular SRCFT stub columns were built and tested to failure under ISO fire herein. The tests explored the effect of reinforced steel, the internal or external heating condition and load ratios. The experimental results indicated that the inserted section steel significantly improved the fire resistance of circular SRCFT columns. The non-uniform fire condition did not produce a detrimental effect on the fire response of the specimen. The numerical model was developed and validated against the experimental results. Then a parametric study was present to evaluate the effect of load level, eccentricity and heating conditions. A comparison was made to check the accuracy of a widely accepted design method. The comparison indicated the design method was generally 36% conservative for axially loaded condition and 25% un-conservative for eccentrically loaded condition.

Preclinical Study of Novel Curcumin Analogue SSC-5 Using Orthotopic Tumor Xenograft Model for Esophageal Squamous Cell Carcinoma

Lai Nar Tung,Senchuan Song,Kin Tak Chan,Mei Yuk Choi,Ho Yu Lam,Chung Man Chan,Zhiyong Chen,Hector K. Wang,Hoi Ting Leung,Simon Law,Yanmin Huang,Huacan Song,Nikki P. Lee 대한암학회 2018 Cancer Research and Treatment Vol.50 No.4

Purpose Tumor xenograft model is an indispensable animal cancer model. In esophageal squamous cell carcinoma (ESCC) research, orthotopic tumor xenograft model establishes tumor xenograft in the animal esophagus, which allows the study of tumorigenesis in its native microenvironment. Materials and Methods In this study, we described two simple and reproducible methods to develop tumor xenograft at the cervical or the abdominal esophagus in nude mice by direct injection of ESCC cells in the esophageal wall. Results In comparing these two methods, the cervical one presented with more clinically relevant features, i.e., esophageal stricture, body weight loss and poor survival. In addition, the derived tumor xenografts accompanied a rapid growth rate and a high tendency to invade into the surrounding structures. This model was subsequently used to study the anti-tumor effect of curcumin, which is known for its potential therapeutic effects in various diseases including cancers, and its analogue SSC-5. SSC-5 was selected among the eight newly synthesized curcumin analogues based on its superior anti-tumor effect demonstrated in an MTT cell proliferation assay and its effects on apoptosis induction and cell cycle arrest in cultured ESCC cells. Treatment of orthotopic tumor-bearing mice with SSC-5 resulted in an inhibition in tumor growth and invasion. Conclusion Taken together, we have established a clinically relevant orthotopic tumor xenograft model that can serve as a preclinical tool for screening new anti-tumor compounds, e.g., SSC-5, in ESCC.

Tailoring the Impact Toughness of Sintered NdFeB Magnets via Surface Coating

X. G. Cui,J. X. Pan,C. Y. Cui,P. Mei,X. H. Wang,C. Fang,T. Y. Ma,C. Wang,X. C. Peng 한국자기학회 2018 Journal of Magnetics Vol.23 No.1

Metallic coating by electroplating is commonly attractive for improving the corrosion resistance of sintered NdFeB magnets. However, its tailoring of mechanical characteristics for sintered NdFeB magnets has been seldom concerned. Herein, the impact toughnesses of sintered NdFeB magnets with various metallic coatings (Ni or Ni/Sn) were comparatively investigated. The results indicate that the impact toughnesses of sintered NdFeB magnets are both improved by Ni coating and Ni/Sn bilayer coating. And Ni/Sn bilayer coating exhibits more enhancement of the impact toughness, increased by 41.6% compared with the original magnet. Moreover, the microstructural observations of the metallic coatings and the fracture were conducted, and the enhanced mechanism of impact toughness for the magnet is analyzed. These findings may provide a reference for toughening the brittle materials.