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Optimum rolling speed and relevant temperature-and reduction-dependent interfacial friction behavior during the break-down rolling of AZ31B alloy

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Journal of Materials Science & Technology 2018年第11期34卷 2051-2062页

作者： Weitao Jia Yan Tang Fangkun Ning Qichi Le Lei Bao Key Laboratory of Electromagnetic Processing of Materials Ministry of EducationNortheastern UniversityShenyang 110819China Key Laboratory of Superlight Materials&Surface Technology Ministry of EducationHarbin Engineering UniversityHarbin 150001China

The present study aimed to determine the optimum rolling speed for break-down rolling of as-cast AZ31 B alloy and investigated the friction behavior associated with temperature-and reduction-sensitivity at the roll/plate contact interface. Tensile testing, formability evaluation and microstructural studies relevant to different rolling speeds were performed and finally the optimum operating rolling speed（50.0 ± 0.8 m/min） was obtained. Further, the effects of rolling reduction and initial temperature were assessed on the temperature variation, lateral spread and interfacial friction behavior at optimum rolling speed. The results showed that lower rolling speed（18.0 ± 0.8 m/min） resulted in an incompletely recrystallized structure where twins occupied relatively high volume fraction. Twinning dominated the deformation at rolling speed exceeding the optimum, resulting in the local recrystallization with shear bands and coarse grains. Rolling at 50.0 ± 0.8 m/min could get the best overall tensile properties and rolling formability due to the relatively high recrystallization degree and microstructure uniformity. An inverse method has been developed to determine the interfacial friction coefficient during interaction of AZ31 B alloy with roll surfaces. When rolling at the optimum speed, the interfacial friction coefficient ranged from 0.16 to 0.58, which was strongly positively correlated with the reduction but slightly positively correlated with the initial temperature. Depended on the rolling characteristics, external friction effect coefficient ranged from 1.25 to 2.35 and it exhibited positive correlation with both the initial rolling temperature and rolling reduction.

关键词： AZ31B alloy Rolling speed lateral spread Friction coefficient External friction effect coefficient

Numerical analyses of pile performance in laterally spreading frozen ground crust overlying liquefiable soils

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Earthquake Engineering and Engineering Vibration 2018年第3期17卷 491-499页

作者： Xiaoyu Ryan Zhang Zhaohui Joey Yang Mueser Rutledge Consulting Engineers New YorkNY 10122USA College of Engineering University of AlaskaAnchorageAK 99508USA

lateral spread of frozen ground crust over liquefied soil has caused extensive bridge foundation damage in the past winter earthquakes.A shake table experiment was conducted to investigate the performance of a model pile in this scenario and revealed unique pile failure *** modelling results provided valuable data for validating numerical *** paper presents analyses and results of this experiment using two numerical modeling approaches： solid-fluid coupled finite element（FE） modeling and the beam-on-nonlinear-Winkler-foundation（BNWF） method.A FE model was constructed based on the experiment configuration and subjected to earthquake *** and pile response results were presented and compared with experimental results to validate this *** BNWF method was used to predict the pile response and failure mechanism.A p-y curve was presented for modelling the frozen ground crust with the free-field displacement from the experiment as *** responses were presented and compared with those of the experiment and FE *** was concluded that the coupled FE model was effective in predicting formation of three plastic hinges at ground surface,ground crust-liquefiable soil interface and within the medium dense sand layer,while the BNWF method was only able to predict the latter two.

关键词： frozen ground crust lateral spread Finite Element (FE) modeling BNWF method

Estimation of residual shear strength ratios of liquefied soil deposits from shear wave velocity

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Earthquake Engineering and Engineering Vibration 2012年第4期11卷 461-484页

作者： Pelinzener Yildiz Technical University Davutpasa CampusDepartment of Civil Engineering

For sites susceptible to liquefaction induced lateral spreading during a probable earthquake, geotechnical engineers often need to know the undrained residual shear strength of the liquefied soil deposit to estimate lateral spreading displacements, and the forces acting on the piles from the liquefied soils in order to perform post liquefaction stability analyses. The most commonly used methods to estimate the undrained residual shear strength （Su~） of liquefied sand deposits are based on the correlations determined from liquefaction induced flow failures with SPT and CPT data. In this study, 44 lateral spread case histories are analyzed and a new relationship based on only lateral spread case histories is recommended, which estimates the residual shear strength ratio of the liquefiable soil layer from normalized shear wave velocity. The new proposed method is also utilized to estimate the residual lateral displacement of an example bridge problem in an area susceptible to lateral spreading in order to provide insight into how the proposed relationship can be used in geotechnical engineering practice.

关键词： liquefaction lateral spread undrained residual shear strength undrained residual shear strength ratio shearwave velocity

Simple Traits among Diaspore Weight/Number,Plant Height and Ability of Vegetative Propagation

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Journal of Integrative Plant Biology 2008年第12期50卷 1563-1569页

作者： Bozena erá Institute of Systems Biology and Ecology Academy of Sciences of the Czech Republiceské Budějovice 37005

Several expected correlations among followed internal plant traits were confirmed using the dataset of 492 herbaceous species from the temporal zone of Central Europe. Average diaspore weight （seed mass）, reproductive capacity of population （number of produced diaspores）, species height, and ability of lateral spread were the plant traits considered. The evident correlations were confirmed among all investigated traits：（i） The reproductive capacity of population negatively correlated with diaspore weight, plant height, and vegetative propagation. The diaspore weight and their number are closely correlated and co-adapted. （ii） Bigger plant species produce bigger diaspores. These trends are obvious at the inter- and intra-family levels. （iii） Larger plant species showed higher ability to vegetative propagation.

关键词： comparison lateral spread reproduction seed production seed weight strategy trade-off.