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25. Numerical simulation and analysis of microfracture mechanism of magnesium alloy materials

Author

Yang Yongxin, Wei Baoli, Liu Huazhou, Yang Shaolong, Li Jiang, Qu Chenming, and Feng Yashan

Subjects
ebsd, fracture properties, microcracking, az31b magnesium alloy, strain amplitude, 97p20, Mathematics, QA1-939
Abstract

This paper takes the typical AZ31B magnesium alloy, which is increasingly widely used in engineering, as the research object and aims to study the fracture properties of magnesium alloys and their damage mechanisms under different loading strain rates and loading modes. EBSD, trace method, and other techniques are applied to study the fracture modes at a low strain amplitude of 0.42% and high strain amplitude of 1.746%, to explore and compare the type and number of microcracks at these two strain amplitudes, and to analyze the reasons for the formation of different types of microcracks. The results show that the experimental 0pass and 4pass start to fracture when they are numerically simulated impact loaded at impact velocities of 225m/s and 260m/s, and the larger the value of impact loading, the more complete the fracture occurs. The fatigue fracture occurred at TBs, GBs, and PSBs with a strain amplitude of 1.746% and 0.42%, respectively. The SF of PSBs was mainly distributed in the range of 0.8-1.0, while that of TBs was most distributed in the interval of 0-0.2 and 0.6-0.9. The larger the SF, the more prone to sprouting of microcracks. The smaller the value of m′, the larger the value of Φ, the more likely to promote microcracks sprouting at the grain boundaries.

Published
2024
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26. Topological characterization of the microstructure of magnesium alloy materials based on complex networks

Author

Yang Yongxin, Shi Yanhong, Feng Yashan, Li Jiang, Yang Shaolong, Liu Huazhou, Qu Chenming, and Wei Baoli

Subjects
microstructure, martensitic phase transition topology, complex network, macroscopic characterization, mechanical properties, magnesium alloy materials, 68t05, Mathematics, QA1-939
Abstract

Magnesium alloys, as the lightest commercial metal engineering structural materials, have good application prospects in the automotive, communication equipment, aerospace, and military industries because of their light specific gravity, high strength properties such as specific strength and stiffness, shielding from electromagnetic radiation, and easy recycling. In this paper, starting from the density and microstructure of magnesium alloy, the mechanical properties and corrosion resistance of magnesium alloy are proposed to measure the indexes, and the corresponding prediction model is constructed. Then, fine-crystal magnesium alloys are prepared sequentially by ingot casting and isometric channel extrusion, and then the microstructure of magnesium alloys is observed by scanning electron microscope and transmission electron microscope to extract the micro-parameters of magnesium alloys. A martensitic phase transition topology model was introduced to determine the macroscopic shape strain of magnesium alloy crystals. Complex network analysis is used to quantify the topological structure parameters of a magnesium alloy network in terms of degree, clustering coefficient, and average path length. Finally, the correlation between the macroscopic features and microstructure of magnesium alloy is explored with the obtained data, and the mechanical and corrosion resistance properties of magnesium alloy are analyzed through simulation experiments by combining them with the constructed prediction model. The microstructural topological characteristic parameters of magnesium alloys show that when the pressure is 50 kPa, the average path length after weighting decreases from 36.012 × 10−3 to 34.015 × 10–3, and the force transfer efficiency is gradually increasing. The AZ31 alloy samples obtained from casting in this paper have a capacitive arc diameter of about 1600 Ω-cm² and the best corrosion resistance among the tested samples.

Published
2024
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43. DrABC: deep learning accurately predicts germline pathogenic mutation status in breast cancer patients based on phenotype data

Author

Liu, Jiaqi, Zhao, Hengqiang, Zheng, Yu, Dong, Lin, Zhao, Sen, Huang, Yukuan, Huang, Shengkai, Qian, Tianyi, Zou, Jiali, Liu, Shu, Li, Jun, Yan, Zihui, Li, Yalun, Zhang, Shuo, Huang, Xin, Wang, Wenyan, Li, Yiqun, Wang, Jie, Ming, Yue, Li, Xiaoxin, Xing, Zeyu, Qin, Ling, Zhao, Zhengye, Jia, Ziqi, Li, Jiaxin, Liu, Gang, Zhang, Menglu, Feng, Kexin, Wu, Jiang, Zhang, Jianguo, Yang, Yongxin, Wu, Zhihong, Liu, Zhihua, Ying, Jianming, Wang, Xin, Su, Jianzhong, Wang, Xiang, and Wu, Nan

Published
2022
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45. Flutter Suppression Effects of Movable Vertical Stabilizers on Suspension Bridges With Steel Box Girders.

Author

Zhou, Rui, Xiao, Dong, Fang, Genshen, Yang, Yongxin, Ge, Yaojun, Xu, Haojun, Wu, Yufei, and Chang, Chia-Ming

Subjects
STEEL girders, BOX girder bridges, BOX beams, SUSPENSION bridges, WIND speed
Abstract

As the combination of springs and vertical stabilizers, the movable downward vertical central stabilizer (MDVCS) is proposed to further control the nonlinear flutter of super long‐span suspension bridges in this paper. A series of flutter suppression tests of closed‐box girders and twin‐box steel girders with various MDVCSs are conducted. Based on the coupled flutter theoretical method, the sensitivity analysis of two important parameters including the height and stiffness of MDVCS are carried out to compare their nonlinear flutter control mechanism. The results show that the flutter critical wind speed (Ucr) of the closed‐box girder continued to increase with the decrease of the height of the DVCS and the increase of spring stiffness, whereas the Ucr of the twin‐box girder increased at first and then decreased. The cubic polynomial function and quadratic Holliday function are suitable to modify the correction coefficients of Ucr for the closed‐box girder with various stiffnesses and heights of MDVCS, while the Lorentz peak‐value function and cubic polynomial function are suitable to modify the Ucr of the twin‐box girder. Furthermore, the MDVCS significantly changes the rules of two positive and negative aerodynamic damping ratios for the closed‐box girder and two negative aerodynamic damping ratios for the twin‐box girder. Besides, the peak vertical displacement amplitudes of the box girder are about half of the MDVCS, since both the height and stiffness of MDVCS alter the elliptical radius of vertical phase planes to affect the limit cycle oscillation of soft flutter, especially for the leeward MDVCS for the twin‐box girder. [ABSTRACT FROM AUTHOR]

Published
2024
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50. Knowledge sharing : from atomic to parametrised context and shallow to deep models

Author

Yang, Yongxin

Subjects
006.3, Electronic Engineering and Computer Science, Machine learning, knowledge sharing
Abstract

Key to achieving more effective machine intelligence is the capability to generalise knowledge across different contexts. In this thesis, we develop a new and very general perspective on knowledge sharing that unifi es and generalises many existing methodologies, while being practically effective, simple to implement, and opening up new problem settings. Knowledge sharing across tasks and domains has conventionally been studied disparately. We fi rst introduce the concept of a semantic descriptor and a flexible neural network approach to knowledge sharing that together unify multi-task/multi-domain learning, and encompass various classic and recent multi-domain learning (MDL) and multi-task learning (MTL) algorithms as special cases. We next generalise this framework from single-output to multi-output problems and from shallow to deep models. To achieve this, we establish the equivalence between classic tensor decomposition methods, and specifi c neural network architectures. This makes it possible to implement our framework within modern deep learning stacks. We present both explicit low-rank, and trace norm regularisation solutions. From a practical perspective, we also explore a new problem setting of zero-shot domain adaptation (ZSDA) where a model can be calibrated solely based on some abstract information of a new domain, e.g., some metadata like the capture device of photos, without collecting or labelling the data.

Published
2017

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