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第三届中国国际毛纺织会议

作者： Liu Hongling Yu Weidong College of Textiles Donghua University Shanghai 200051 China Zhang Yuting College of Material Science & Engineering Donghua University Shanghai 200051 China

＜正＞The stretching slenderization theory of wool fiber is based on the microstructure of wool fibers. Based on the stress-strain curves,it is probable to study the transformation of wool microstructure,including the breaking of disulphide bonds,the slippage between the molecules chains and the α→β*** addition, the concept of critical strain and its meaning are also presented.

关键词： stress-strain curves wool fibre microstructure slenderization critical strain yield point

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Predicting the Mechanical Properties of Polyurethane Elastomers Using Machine Learning

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Chinese Journal of Polymer Science 2023年第3期41卷 422-431,I0009页

作者： Fang Ding Lun-Yang Liu Ting-Li Liu Yun-Qi Li Jun-Peng Li Zhao-Yan Sun State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China School of Applied Chemistry and Engineering University of Science and Technology of ChinaHefei 230026China Department of Polymer Materials and Engineering College of Materials and MetallurgyGuizhou UniversityGuiyang 550025China State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals Sino-Platinum Metals Co.Ltd.Ltdunming 650106China

Bridging the gap between the computation of mechanical properties and the chemical structure of elastomers is a long-standing *** fill the gap,we create a raw dataset and build predictive models for Young’s modulus,tensile strength,and elongation at break of polyurethane elastomers(PUEs).We then construct a benchmark dataset with 50.4%samples remained from the raw dataset which suffers from the intrinsic diversity problem,through a newly proposed recursive data elimination *** coefficients of determination(R^(2)s)from predictions are improved from 0.73-0.78 to 0.85-0.91 based on the raw and the benchmark *** fitting of stress-strain curves using the machine learning model shows a slightly better performance than that for one of the well-performed constitutive models(e.g.,the Khiêm-Itskov model).It confirmed that the black-box machine learning models are feasible to bridge the gap between the mechanical properties of PUEs and multiple factors for their chemical structures,composition,processing,and measurement *** accurate prediction for these curves is still a *** release the raw dataset and the most representative benchmark dataset so far to call for more attention to tackle the longstanding gap problem.

关键词： Mechanical properties stress-strain curves Polyurethane elastomers Machine learning Benchmark dataset

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Effect of strain rate on the compressive deformation behaviors of lotus-type porous copper

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International Journal of Minerals,Metallurgy and Materials 2014年第7期21卷 687-695页

作者： Xin-hua Liu Hai-you Huang Jian-xin Xie Institute for advanced Materials and Technology University of Science and Technology Beijing Key Laboratory for Advanced Materials Processing(MOE) University of Science and Technology Beijing

Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10-3-2400 s-1 with the compressive direction parallel to the pores. A GLEEBLE-1500 thermal-mechanical simulation system and a split Hopkinson pressure bar （SHPB） were used to investigate the effect of strain rate on the compressive deforma-tion behaviors of lotus-type porous copper. The influence mechanism of strain rate was also analyzed by the strain-controlling method and by high-speed photography. The results indicated that the stress-strain curves of lotus-typed porous copper consist of a linear elastic stage, a plateau stage, and a densification stage at various strain rates. At low strain rate （〈1.0 s^-1）, the strain rate had little influence on the stress-strain curves; but when the strain rate exceeded 1.0 s^-1, it was observed to strongly affect the plateau stage, showing obvious strain-rate-hardening characteristics. strain rate also influenced the densification initial strain. The densification initial strain at high strain rate was less than that at low strain rate. No visible inhomogeneous deformation caused by shockwaves was observed in lotus-type porous copper during high-strain-rate deformation. However, at high strain rate, the bending deformation characteristics of the pore walls obviously differed from those at low strain rate, which was the main mechanism by which the plateau stress exhibited strain-rate sensitivity when the strain rate exceeded a certain value and exhibited less densification initial strain at high strain rate.

关键词： porous materials copper directional solidification strain rate sensitivity deformation modes stress-strain curves

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Intermediate HSS bracing members during seismic excitations： modeling, design, and behavior

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Frontiers of Structural and Civil Engineering 2018年第1期12卷 148-162页

作者： Madhar HADDAD Department of Architectural Engineering United Arab Emirates University P. O. Box 15551 AI Ain UAE

Concentric hollow structural section （HSS） bracing members are used frequently in steel framed structural systems to resist seismic excitations. Finite element modeling of the HSS braces that utilizes the true stress- strain curves produces hysteresis responses that are reasonable matches to the experimental response. True stress-strain curves are obtained from coupon tests or stub-column tests while utilizing an exponential function or strain hardening role with a trial and error procedure to obtain the hysteresis behavior. In the current study, the true stress-strain curves are directly obtained from tests on stub-columns extracted from the full scale HSS bracing members away from the mid- length plastic hinge after cyclic testing. Two experimental tests （Shaback 2001 and Haddad 2004） were used to validate the model. Results indicate that the stress-strain curves for these braces are not unique. A refined damage accumulation model for ultra-low-cycle fatigue is implemented to predict fracture of the brace tests. The refined damage model is then used in the finite element modeling to predict fracture of braces in a chevron braced frame of an eight-storey building subjected to selected ground motions analyzed using OpenSees program. Results indicate that all braces could sustain the selected earthquake records without fracture.

关键词： HSS FEM stress-strain curves damage model

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Fatigue Induced Alteration of the Superficial Strength Properties of 2024 Aluminum Alloy

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Journal of Materials Science & Technology 2011年第9期27卷 776-784页

作者： K.-D. Bouzakis I. Mirisidis Sp.G. Pantelakis A.N. Chamos Laboratory for Machine Tools and Manufacturing Engineering Mechanical Engineering Department Aristotle Uni-versity of Thessaloniki Laboratory of Technology and Strength of Materials Department of Mechanical Engineering & Aeronautics Univer-sity of Patras

aluminum alloy 2024 T3 specimens have been subjected to constant amplitude fatigue loading at R=0.1. During fatigue, an appreciable increase of the surface hardness of the material at the meso-scale can be observed and captured by means of nanoindentations. Surface hardness increases with increasing fatigue stress amplitude and advancing number of applied fatigue cycles. Observed increase of specimen surface hardening degree during fatigue causes an evolution of superficial mechanical strength properties of the alloy. stress-strain curves associated with the evoluting superficial mechanical properties are derived, employing a developed finite element method （FEM）-supported evaluation procedure of nanoindentation experimental results.

关键词： 2024 aluminum alloy Nanoindentations Fatigue loading stress-strain curves

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Application of the Mechanical Threshold stress Model to Large strain Processing

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Materials Sciences and Applications 2022年第5期13卷 300-316页

作者： Paul S. Follansbee Professor Emeritus Saint Vincent College Latrobe PA USA

Large-strain deformations introduce several confounding factors that affect the application of the Mechanical Threshold stress model. These include the decrease with the increasing stress of the normalized activation energy characterizing deformation kinetics, the tendency toward Stage IV hardening at high strains, and the influence of crystallographic texture. Minor additions to the Mechanical Threshold stress model are introduced to account for variations of the activation energy and the addition of Stage IV hardening. Crystallographic texture cannot be modeled using an isotropic formulation, but some common trends when analyzing predominantly shear deformation followed by uniaxial deformation are described. Comparisons of model predictions with measurements in copper processed using Equal Channel Angular Pressing are described.

关键词： Mechanical Threshold stress Model Large-strain Deformations ECAP stress-strain curves Shear Deformations Activation Energy strain-Hardening

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