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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 1115-1125页

作者： Binghui Hu Yu Lei Hang Li Ziyi Wang Chao Yu Guozheng Kang Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Aerospace EngineeringSouthwest Jiaotong UniversityChengdu 610031China

The nonproportional multiaxial ratchetting of cast AZ91 magnesium (Mg) alloy was examined by performing a sequence of axial-torsional cyclic tests controlled by stress with various loading paths at room temperature (RT).The evolutionary characteristics and path dependence of multiaxial ratchetting were discussed.Results illustrate that the cast AZ91 Mg alloy exhibits considerable nonproportional additional softening during cyclic loading with multiple nonproportional multiaxial loading paths;multiaxial ratchetting presents strong path dependence,and axial ratchetting strains are larger under nonproportional loading paths than under uniaxial and proportional45°linear loading paths;multiaxial ratchetting becomes increasingly pronounced as the applied stress amplitude and axial mean stress increase.Moreover,stress-strain curves show a convex and symmetrical shape in axial/torsional directions.Multiaxial ratchetting exhibits quasi-shakedown after certain loading cycles.The abundant experimental data obtained in this work can be used to develop a cyclic plasticity model of cast Mg alloys.

关键词： cast magnesium alloy ratchetting multiaxial loading loading path stress level

Preliminary analysis on the tectonic stress level in the source region of Tangshan earthquake

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Acta Seismologica Sinica(English Edition) 2002年第3期15卷 285-293页

作者：赵建涛崔效锋谢富仁 Institute of Crustal Dynamics China Seismological Bureau Beijing China

The abundant data of focal mechanism solutions in Tangshan region, China, are inverted for the tectonic stress field. Combined with tectonophysical consideration, the magnitude of the three principal stresses, as well as their vertical variation under the average crustal rock property, in the source region of the 1976 Tangshan earthquake is estimated. The relationship between crustal stress and friction mc, pore pressure P0 and stress shape factor F is studied. The paper draws the conclusion that the vertical increasing rate of the maximum principal stress s is directly proportional to friction, and inversely to pore pressure P0 and stress shape factor F ; while the vertical increasing rate of the minimum principal tress s is directly proportional to pore pressure P0, inversely to friction mc and stress shape factor F. This study is a try to invert the data of focal mechanism solutions for the complete stress tensor.

关键词： tectonic stress field focal mechanism solution stress level inversion

Study on determination of stress level by seismic stress drops and the stress axis de-flections before and after large earthquakes

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Acta Seismologica Sinica(English Edition) 2006年第5期19卷 507-513页

作者：万永革 Institute of Geophysics China Earthquake Administration Institute of Disaster Prevention Science and Technology Hebei 065201China

To obtain the stress level at the earthquake source, this paper sets forth the solution of the stress magnitude at the earthquake source by seismic stress drop and the stress axis deflections before and after large earthquakes. The pre-seismic and post-seismic stress direction can be statistically determined by a large collection of foreshock and aftershock focal mechanism data while the stress drop can be determined through the source fracture inversion from seismic wave data or crust deformation data. The paper attempts to make a fundamental contribution to seismic dynamics.

关键词： stress level seismic stress drop stress axis deflection

Experimental investigation on uniaxial cyclic plasticity of cast AZ91 magnesium alloy

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Journal of Magnesium and Alloys 2023年第9期11卷 3255-3271页

作者： Yu Lei Ziyi Wang Guozheng Kang Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Aerospace EngineeringSouthwest Jiaotong UniversityChengdu 610031China

The uniaxial cyclic plasticity of cast AZ91 magnesium(Mg) alloy was investigated by conducting a series of cyclic straining and stressing tests at room temperature, and a unique cyclic plasticity(especially for ratchetting) and its physical nature were revealed. The experimental results demonstrate that the cast AZ91 Mg alloy behaviors tension-compression symmetry, because the dislocation slipping and twinning occur during both the tensile and compressive deformations;although the cast AZ91 alloy presents a certain pseudo-elastic behavior during unloading due to the detwinning, there is no obvious S-shaped asymmetric hysteresis loop like that of wrought Mg alloy in the cyclic tensile-compressive tests, and an obvious cyclic hardening is observed;moreover, the ratchetting of the cast AZ91 alloy presented in the cyclic stressing tests depends remarkably on the prescribed mean stress and stress amplitude, but slightly changes with the stress rate, and the evolution of responding peak/valley strain greatly differs from that of wrought Mg alloys and stainless steels. This work provides rich experimental data for establishing the constitutive model of cast Mg alloys.

关键词： Cast magnesium alloy Ratchetting Twinning/detwinning stress level stress rate

Effect of Fatigue Loading on the Mechanical Properties and Resistance of High-strength Straight-hole Recycled Pervious Concrete to Rainstorm-based Waterlogging

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Journal of Wuhan University of Technology(Materials Science) 2023年第1期38卷 141-148页

作者：朱平华 FAN Haifeng YAN Xiancui LIU Hui WANG Xinjie CHEN Chunhong Department of Civil Engineering Changzhou UniversityChangzhou 213164China

A novel high-strength straight-hole recycled pervious concrete(HSRPC)for the secondary highway pavement was prepared in this paper.This study aimed to investigate the effect of porosity(0.126%,0.502%,and 1.13%),vehicle loading stress level(0.5 and 0.8)and service life on the resistance to rainstormbased waterlogging of HSRPC under fatigue loading.The mechanical properties of HSRPC in terms of flexural strength and dynamic elastic modulus were studied.The waterlogging resistance of HSRPC was described by surface water depth and drainage time.The microstructure of HSRPC were observed with scanning electron microscopy(SEM).Results showed that although the dynamic elastic modulus and flexural strength of HSRPC decreased with the increasing number of fatigue loading,the flexural strength of HSRPC was still greater than5 MPa after design service life of 20 years.After 2.5×10^(5)times of fatigue loading,the permeability coefficient of HSRPC with a porosity of 0.502%and 1.13%increased by 18.4%and 22.9%,respectively;while the permeability coefficient of HSRPC with 0.126%porosity dropped to 0.35 mm/s.The maximum surface water depth of HSRPC with a porosity of 0.126%,0.502%,and 1.13%were 8,5 and 4 mm,respectively.SEM results showed that fatigue loading expanded the number and width of cracks around the tiny pores in HSRPC.

关键词： recycled pervious concrete porosity fatigue loading service life stress level rainstorm and waterlogging

Chloride diffusion in concrete with carbonated recycled coarse aggregates under biaxial compression

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Frontiers of Structural and Civil Engineering 2023年第4期17卷 637-648页

作者： Jingwei YING Weibeng WANG Jianzhuang XIAO Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education Guangxi UniversityNanning 530004China College of Civil Engineering and Architecture Guangxi UniversityNanning 530004China Guangxi Key Laboratory of Disaster Prevention and Engineering Safety Guangxi UniversityNanning 530004China Department of Structural Engineering College of Civil EngineeringTongji UniversityShanghai 200092China

Chloride attack on concrete structures is affected by the complex stress state inside concrete,and the effect of recycled aggregates renders this process more complex.Enhancing the chloride resistance of recycled concrete in a complex environment via carbonization facilitates the popularization and application of recycled concrete and alleviates the greenhouse effect.In this study,the chloride ion diffusion and deformation properties of recycled concrete after carbonization are investigated using a chloride salt load-coupling device.The results obtained demonstrate that the chloride ion diffusivity of recycled concrete first decreases and then increases as the compressive load increases,which is consistent with the behavior of concrete,in that it first undergoes compressive deformation,followed by crack propagation.Carbonation enhances the performance of the recycled aggregates and reduces their porosity,thereby reducing the chloride diffusion coefficient of the recycled concrete under different compressive load combinations.The variation in the chloride ion diffusivity of the carbonized recycled aggregate concrete with the load is consistent with a theoretical formula.

关键词： recycled concrete carbonated recycled coarse aggregate biaxial compression chloride diffusion stress level

Process Evaluation, Tensile Properties and Fatigue Resistance of Chopped and Continuous Fiber Reinforced Thermoplastic Composites by 3D Printing

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Journal of Renewable Materials 2022年第2期10卷 329-358页

作者： Wei Chen Qiuju Zhang Han Cao Ye Yuan School of Mechanical Engineering Jiangnan UniversityWuxi214122China Jiangsu Province Key Laboratory of Advanced Food Manufacturing Equipment and Technology Jiangnan UniversityWuxi214122China

The aim of this article was to comprehensively evaluate the manufacturing process,tensile properties and fatigue resistance of the chopped and continuous fiber reinforced thermoplastic composites(CFRTPCs)by 3D printing.The main results included:the common defects of the printed CFRTPCs contained redundant and accumulation defects,scratch and warping defects;the continuous fiber contributed to the dimensional stability and accuracy of width and thickness;associations between mass percentage of fiber reinforcement and the averages of elastic mod-ulus,strain at break and ultimate tensile strength were approximately linear based on tensile test results;the fati-gue resistance improved with the increasing fiber reinforcement based on fatigue test results.As for specimens with four fiber rings,there was a good linear relationship between the stress level and logarithm value of cycles during the whole life while those of pure matrix and specimens with one and two fiber rings were piecewise linear,taking about 10,000 cycles as boundary.The micro morphology showed that the fatigue failure behaved as matrix fracture,large and small fiber bundles and single fibers extracted from matrix.Under the tension-tension fatigue load,the deformations where easily concentrating stress behaved as sunken surfaces along thickness and width directions,and the deformation along width direction was greater than that along thickness direction.

关键词： CFRTPCs 3D printing tensile test fatigue behavior stress level micro morphology

Experimental Investigation of the Creep Behaviour of Glulam Compression-Bending Members

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Journal of Renewable Materials 2022年第6期10卷 1517-1535页

作者： Yifei Yin Lirong Qu Weidong Lu Chengshuai Li College of Civil Engineering Nanjing Tech UniversityNanjing211816China

Creep test results of glulam members under compression and bending were studied in this paper.The creep tests were conducted to investigate the influence of the stress level and relative eccentricity on the creep deformation of glulam members.The test results showed that the creep deformation trends of glulam members under long-term compression and bending loading were similar;the creep deformation increased with increases in both the stress level and relative eccentricity.However,the relative creep deformation decreased with the increase in both the stress level and relative eccentricity under long-term loading,and a five-parameter creep model was proposed to analyse the creep mechanism of glulam members under compression and bending.The good fitness of the test results indicated that the five-parameter model was able to accurately simulate the creep deformation of glulam compression-bending members.Moreover,a numerical model was developed using the creep equation,which was related to the parameter a and b.The simulation results were in good agreement with the test results,and the parameters a and b were correlated to the relative eccentricity and stress level,respectively.Based on the corrected parameters a and b,the relative creep deformation of glulam compression-bending members was predicted over 50 years.

关键词： Glulam compression-bending members creep stress level relative eccentricity

Normalized fatigue properties of asphalt mixture at various temperatures

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Journal of Road Engineering 2023年第3期3卷 279-287页

作者： Dongdong Ge Zihao Ju Defeng Duan Songtao Lyu Weiwei Lu Chaochao Liu Key Laboratory of Special Environment Road Engineering of Hunan Province Changsha University of Science and TechnologyChangsha 410114China National Engineering Research Center of Highway Maintenance Technology Changsha University of Science and TechnologyChangsha 410114China CCCC-SHB Fourth Engineering Co. Ltd.Luoyang 471000China

This study normalized the mixture's fatigue behavior at various temperatures,and the strength and fatigue tests of the mixture were conducted.The stress state of the asphalt mixture includes direct tensile,uniaxial compression,and indirect tensile.The Desai yield surface and fatigue path were proposed.And a normalized fatigue characteristics model of the mixture was established.The following conclusions were obtained.With the increases in the loading rate,the strength of the asphalt mixture increased.As the temperature increases,the strength of the mixture is reduced.At various temperatures and rates,the strength forms a closed curved surface.The Desai strength yield surface was established,which forms a closed curved surface.When the loading rate and temperature are below a certain critical line,the asphalt mixture will not undergo strength damage.At a fixed stress state,the fatigue damage path of the mixture was determined.The stress ratio was determined considering the influence of the loading rate.In this way,a normalized model can be described to express the asphalt mixture fatigue properties at various temperatures and stress levels.For the asphalt mixture in an indirect tensile state,the normalized fatigue equation parameter is 4.09.This model is more suitable for reflecting the viscous-elastic behavior of the mixtures than the fatigue equation determined by the notional stress ratio.

关键词： Asphalt mixture Normalization equation Load rates Test temperature stress level Desai yield surface

Estimation of the stress levels in the focal region before and after the 2001 M=8.1 Western Kunlun Mountain Pass earth-quake

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Acta Seismologica Sinica(English Edition) 2005年第6期18卷 651-655页

作者：陈学忠 Institute of Geophysics China Earthquake Administration Beijing 100081 China

A method estimating the stress level in the focal region of an earthquake is proposed here. Taking the 2001 M=8.1 Western Kunlun Mountain Pass earthquake as an example, we estimate its stress level in the focal region before and after it by this method. The results show that the stress level in the focal region just prior to the initiation of this event is approximately 6.3-8 MPa, and about 5-6.7 MPa remained in the focal region after its occurrence. The stress in the focal region decreased by roughly twenty percent after this event.

关键词： Western Kunlun Mountain Pass earthquake focal region stress level