Serrated flow and failure behaviors of a Hadfield steel at various strain rates under extensometer-measured strain control tensile load
作者：
Zhang, Liqiang;Guo, Pengcheng* ;Wang, Guan;Liu, Shuai
期刊：
Journal of Materials Research and Technology ,2020年9(2):1500-1508 ISSN：2238-7854
通讯作者：
Guo, Pengcheng
作者机构：
[Guo, Pengcheng; Zhang, Liqiang] Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Peoples R China.;[Wang, Guan] Ningxia Univ, Coll Mech Engn, Yinchuan 750021, Ningxia, Peoples R China.;[Liu, Shuai] North China Univ Sci & Technol, Coll Met & Energy, Tangshan, Peoples R China.
通讯机构：
[Guo, Pengcheng] C;Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Peoples R China.
关键词：
Dilatometers;Displacement control;Manganese steel;Strain control;Deformation band;Dynamic strain ageing;Failure behaviors;High strain rates;Low strain rates;Serrated flow;Strain levels;Tensile loads;Strain rate
摘要：
A Hadfield steel has been investigated to clarify the serrated flow and to explore the failure behavior at room temperature. The tensile experiments were performed under extensometer-measured strain control, rather than under conventional cross-head displacement control, at strain rates ranging from 6»×»10-3 s-1 to 6»×»10-6 s-1. Three types of serrations, including type A, B and C ones, are observed. The occurrence of different types of serrations depends on both strain rate and strain level. The type C serration is identified in Hadfield steels at room temperature for the first time. At high strain rates, there is substantially higher serration density and reduction in stress compared with that observed at low strain rates. Furthermore, two different initiation modes of deformation bands are revealed. The fracture crack nucleates at a position with dense twins, and propagates primarily in the direction perpendicular to the tensile axis and deflects frequently due to the interaction with the boundary of grains and twins. © 2019 The Authors.
语种：
英文
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Temperature's Effect on Color Change and Mechanical Properties of Poplar Powder Compact Formed by Warm Compaction
作者：
Zhang, Liqiang* ;Long, Zhizhong;Tan, Zhili;Wu, Qingding
期刊：
BIORESOURCES ,2020年15(3):7009-7017 ISSN：1930-2126
通讯作者：
Zhang, Liqiang
作者机构：
[Zhang, Liqiang; Tan, Zhili; Long, Zhizhong; Wu, Qingding] Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Zhang, Liqiang] C;Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.
关键词：
Mechanical properties;Poplar powder;Surface color;Warm compaction
摘要：
Warm compaction technology is an eco-friendly method to improve the added value of poplar. In this work, the wood powder was compacted in the mold between 120 °C to 200 °C, at 80 MPa for 30 min. The color change, chemical properties, and mechanical properties were evaluated. The color of the formed compaction darkened uniformly. The CIE lightness color coordinate (L*) and chroma coordinates a* and b* decreased with the increase of forming temperature. Fourier infrared spectral analysis showed degradation of carbohydrates, along with the formation of a new chemical structure of darker color. Mechanical properties including modulus of rupture (MOR) and modulus of elasticity (MOE) of compacted wood increased initially and then decreased. These results provide a reference for the surface color control of thermally forming materials. © 2020
语种：
英文
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前置导叶对混流泵性能的影响及研究
作者：
马庆勇;邹智雄;张奇志;张林
期刊：
水泵技术 ,2018年(2):9-11,48 ISSN：1002-7424
作者机构：
中南林业科技大学机电工程学院;[邹智雄] 湖南耐普泵业股份有限公司;[张林; 马庆勇; 张奇志] 中南林业科技大学
关键词：
混流泵;前置导叶;效率;节能
摘要：
提高泵的运行效率对于节能减排有重要意义。本文提出一种新的节能装置——前置导叶,来提高泵站多年来由于淤积和水位变化引起的效率降低。本文通过试验验证安装前置导叶对泵性能的影响、不同预旋角度对泵性能的影响,并分析实际效果,说明利用前置导叶提高泵工况的运行效率是一种可行的方法。
语种：
中文
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Determination of the heat transfer coefficient at the metal–sand mold interface of lost foam casting process
作者：
Zhang, Liqiang* ;Tan, Wenfang;Hu, Hao
期刊：
Heat and Mass Transfer ,2016年52(6):1131-1138 ISSN：0947-7411
通讯作者：
Zhang, Liqiang
作者机构：
[Tan, Wenfang; Hu, Hao; Zhang, Liqiang] Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.;[Zhang, Liqiang] Hunan Univ, State Key Lab Adv Design & Mfg Vehicle Body, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Zhang, Liqiang] C;[Zhang, Liqiang] H;Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.;Hunan Univ, State Key Lab Adv Design & Mfg Vehicle Body, Changsha 410082, Hunan, Peoples R China.
关键词：
Computer software;Heat conduction;Heat flux;Heat transfer coefficients;Molds;Analytic solution;Commercial software;Heat conduction models;Interfacial heat transfer coefficients;Inverse conduction models;Lost foam casting process;Lost foam castings;Solidification process;Heat transfer
摘要：
For modeling solidification process of casting accurately, a reliable heat transfer boundary condition data is required. In this paper, an inverse conduction model was established to determine the heat flux and heat transfer coefficient at the metal–sand mold interface for cylindrical casting in the lost foam process. The numerically calculated temperature was compared with analytic solution and simulation solution obtained by commercial software ProCAST to investigate the accuracy of heat conduction model. The instantaneous cast and sand mold temperatures were measured experimentally and these values were used to determine the interfacial heat transfer coefficient (IHTC). The IHTC values during lost foam casting were shown to vary from 20 to 800Wm−2K−1. Additionally, the characteristics of the time-varying IHTC have also been discussed in this study. © 2015, Springer-Verlag Berlin Heidelberg.
语种：
英文
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Influence of pressure and surface roughness on the heat transfer efficiency during water spray quenching of 6082 aluminum alloy
作者：
Xu, Rong;Li, Luoxing* ;Zhang, Liqiang;Zhu, Biwu;Liu, Xiao;...
期刊：
Journal of Materials Processing Technology ,2014年214(12):2877-2883 ISSN：0924-0136
通讯作者：
Li, Luoxing
作者机构：
[Bu, Xiaobing; Xu, Rong; Zhang, Liqiang; Zhu, Biwu; Liu, Xiao; Li, Luoxing] Hunan Univ, State Key Lab Adv Design & Mfg Vehicle Body, Changsha 410082, Hunan, Peoples R China.;[Bu, Xiaobing; Xu, Rong; Li, Luoxing] Hunan Univ, Coll Mech & Vehicle Engn, Changsha 410082, Hunan, Peoples R China.;[Zhang, Liqiang] Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.;[Zhu, Biwu; Liu, Xiao] Hunan Univ Sci & Technol, Coll Electromech Engn, Xiangtan 411002, Hunan, Peoples R China.
通讯机构：
[Li, Luoxing] H;Hunan Univ, State Key Lab Adv Design & Mfg Vehicle Body, Changsha 410082, Hunan, Peoples R China.
关键词：
Atmospheric temperature;Crystallization;Heat conduction;Heat flux;Heat transfer coefficients;Inverse problems;Nucleation;Quenching;Surface properties;Surface roughness;Heat transfer efficiency;Interfacial heat transfer;Inverse heat conduction methods;Maximum heat transfer;Nucleation site density;Spray pressure;Spray quenching;Water spray quenching;Aluminum alloys
摘要：
The heat flux (q) and heat transfer coefficient (h) at the interface between hot aluminum surface and spray water were determined by using an inverse heat conduction method. Good agreements between numerically calculated temperatures with the inverse identified h and experimentally measurements demonstrate that the method is valid for solving the q and h of spray quenching process. The estimated heat flux consists of three main stages of transition boiling, nucleate boiling and single-phase cooling. The results show that both the heat flux and heat transfer coefficient increase with the increasing of spray pressure. When the surface temperature is lower than 170 °C, the q, h and the maximum heat transfer coefficient (hmax) decrease and then increase as surface roughness increases. However, when the surface temperature is higher than 170 °C, the influence of surface is insignificant. This phenomenon may be attributed to the variation of nucleation site density with surface roughness. © 2014 Elsevier B.V.
语种：
英文
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小型潜水电泵欠压运行试验研究
作者：
张林;吴闽添;初海波;马庆勇
期刊：
农业工程与装备 ,2014年(3):107-108 ISSN：2096-8736
作者机构：
中南林业科技大学机电工程学院,湖南 长沙,410004;东北林业大学机电工程学院,黑龙江 哈尔滨,150000;[初海波; 张林; 马庆勇] 中南林业科技大学;[吴闽添] 东北林业大学
关键词：
小型潜水电泵;欠压运行;性能参数与试验;适用性
摘要：
以QDX3-18-0.55小型潜水电泵作为试验对象，通过单相潜水电泵试验台调节电压，进行电泵的欠压运行试验研究。结果表明：当小型潜水电泵欠压运行时，电机输出功率明显降低，在同等流量情况下，泵的扬程有小幅下降，但机组效率有所提升。
语种：
中文
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用CFD模拟分析单层、双层搅拌桨叶对搅拌效果的影响
作者：
马庆勇;张奇志;张林
期刊：
湖南农机：学术版 ,2014年(4):38-41 ISSN：1007-8320
作者机构：
中南林业科技大学 机电工程学院,湖南 长沙,410004;[张林; 马庆勇; 张奇志] 中南林业科技大学
关键词：
搅拌器;数值模拟CFD搅拌流场
摘要：
搅拌器被广泛应用于许多工业工程中,文章应用商业计算流体软件Fluent对搅拌槽内的混合过程进行三维数值模拟,采用多重参考系法（MRF）及标准模型。通过对搅拌流场、固液浓度比以及功率因数等方面的分析,来判断安装单层、双层搅拌桨叶对搅拌混合的影响。
语种：
中文
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叶轮式搅拌器的理论设计及数值模拟
作者：
马庆勇;张奇志;张林
期刊：
农业工程与装备 ,2014年(7):62-64+66 ISSN：2096-8736
作者机构：
中南林业科技大学 机电工程学院,湖南 长沙,410004;[张林; 马庆勇; 张奇志] 中南林业科技大学
关键词：
搅拌器;数值模拟;搅拌叶轮
摘要：
通过分析升力线理论、机翼理论及船用螺旋桨理论,来得到轴流式搅拌桨叶的设计方法。并把设计出的搅拌桨叶进行模拟分析,运用计算流体力学软件FLUENT,采用模型,利用多重参考系法,对搅拌槽的搅拌流场、固体颗粒浓度分布,临界转速以及功率因数进行分析。
语种：
中文
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An intelligent system for low-pressure die-cast process parameters optimization
作者：
Zhang, Liqiang;Wang, Rongji*
期刊：
International Journal of Advanced Manufacturing Technology ,2013年65(1-4):517-524 ISSN：0268-3768
通讯作者：
Wang, Rongji
作者机构：
[Zhang, Liqiang; Wang, Rongji] Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.;[Zhang, Liqiang] Hunan Univ, State Key Lab Adv Design & Mfg Vehicle Body, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Wang, Rongji] C;Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.
关键词：
LPDC;Process parameters;Artificial neural network;Genetic algorithm;Numerical simulation
摘要：
Low-pressure die-cast (LPDC) is widely used in manufacturing thin-walled aluminum alloy products. Since the quality of LPDC parts are mostly influenced by process conditions, how to determine the optimum process conditions becomes the key to improve the part quality. In this paper, a combining artificial neural network and genetic algorithm (ANN/GA) method is proposed to optimize the LPDC process. In this method, considering the more complicated preparation process of thin-walled casting, an ANN model combining learning vector quantization and back-propagation (BP) algorithm is proposed to map the complex relationship between process conditions and quality indexes of LPDC. Meanwhile, the orthogonal array design and numerical simulation is applied to obtain the training samples instead of carrying out a real experiment for the sake of cost saving. The genetic algorithm is employed to optimize the process parameters with the fitness function based on the trained ANN model. Then, by applying the optimized parameters, a thin-walled component of 300 mm in length, 100 mm in width, and 1.5 mm in thickness is successfully prepared. The results indicate that the proposed intelligent system is an effective tool for the process optimization of LPDC.
语种：
英文
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Effect of particles size on the magnetocaloric properties in Gd 5Si2Ge2
作者：
Zhang, Liqiang;Zeng, Hong
期刊：
International Journal of Microstructure and Materials Properties ,2013年8(4-5):325-332 ISSN：1741-8410
通讯作者：
Zeng, H.(zonghong78@live.cn)
作者机构：
[Zhang, Liqiang] College of Mechanical and Electrical Engineering, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China;[Zeng, Hong] Advance Technology and Materials Co., Ltd., China Iron and Steel Research Institute Group, Beijing 100081, China
通讯机构：
Advance Technology and Materials Co., Ltd., China Iron and Steel Research Institute Group, China
关键词：
Cooling;Gadolinium alloys;Magnetic bubbles;Materials properties;Meteorology;Particle size;Powders;Refrigerants;Silicon alloys;As cast alloy;Caloric effects;Magnetic entropy change;Magnetic refrigerant materials;Magnetocaloric properties;Particles sizes;Processing condition;Relative cooling power;Magnetocaloric effects
摘要：
In this study, the effect of particle size on the magneto-thermal properties of Gd5Si2Ge2 alloys was investigated. It is found that the alloy powders obtained via the milled processing conditions possess distinctly Magnetocaloric Effects (MCEs). The magnetic entropy change (ΔSM) of the milled Gd 5Si2Ge2 alloy powders for the 38.5-50 um arrives the maximum value of -ΔSM = 9.06 J·kg -1·K-1 for magnetic field change under 2.0 Tesla. The estimated Relative Cooling Power (RCP) for the 50-74 um powders is around 155.94 J kg-1, which increases 28% comparing with that of the as-cast alloy (121.67 J kg-1). These results indicate that the particle size in the micrometre range can remarkably affect the MCE in the alloys, and consequently, strong influence on the conversion performance. Therefore, care should be taken to choose the appropriate particle size for the magnetic refrigerant materials. Copyright © 2013 Inderscience Enterprises Ltd.
语种：
英文
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Determination of heat transfer coefficients at metal/chill interface in the casting solidification process
作者：
Zhang, Liqiang* ;Li, Luoxing
期刊：
Heat and Mass Transfer ,2013年49(8):1071-1080 ISSN：0947-7411
通讯作者：
Zhang, Liqiang
作者机构：
[Zhang, Liqiang] Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.;[Zhang, Liqiang; Li, Luoxing] Hunan Univ, State Key Lab Adv Design & Mfg Vehicle Body, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Zhang, Liqiang] C;Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.
关键词：
Heat flux;Testing;Calculation parameters;Casting solidification;Casting solidification process;Heat conduction models;Interfacial heat transfer coefficients;Inverse algorithm;Least-squares techniques;Sequential function specification methods;Solidification
摘要：
The present work focuses on the determination of interfacial heat transfer coefficients (IHTCs) between the casting and metal chill during casting solidification. The proposed method is established based on the leastsquares technique and sequential function specification method and can be applied to calculate heat fluxes and IHTCs for other alloys. The accuracy and stability of the method has been investigated by using a typical profile of heat fluxes simulating the practical conditions of casting solidification. In the test process, the effects of various calculation parameters in the inverse algorithm are also analyzed. Moreover, numerically calculated and experimental results are compared by applying the determined IHTCs into the forward heat conduction model with the same boundary conditions. The results show that the numerically calculated temperatures are in good agreement with those measured experimentally. This confirms that the proposed method is a feasible and effective tool for determination of the casting-mold IHTCs. © Springer-Verlag Berlin Heidelberg 2013.
语种：
英文
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