检索结果-南通市图书馆

Bi-variable damage model for fatigue life prediction of metal components

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2011年第3期27卷 416-425页

作者： Miao Zhang Qing-Chun Meng Xing Zhang Wei-ping hu Division 508 School of Aeronautic Science and Engineering Beihang University 100191 Beijing China

Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and damage evolution criteria. Furthermore,damage evolution equations of time rate are established by the generalized Drucker＇s postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations,and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise,for notched specimens under the repeated loading with constant strain amplitude,the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus,the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1,2 and 3.

关键词： Bi-variable damage model - Damage evolution equation . Life prediction - Fatigue . Damage mechanics

A new integration algorithm for finite deformation of thermo-elasto-viscoplastic single crystals

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2013年第5期29卷 709-717页

作者： Dan Zhao Yi-Guo Zhu ping hu Wan-Xi Zhang State Key Laboratory of Structural Analysis for Industrial Equipment Faculty of Vehicle Engineering and MechanicsDalian University of Technology

An algorithm for integrating the constitutive equations in thermal framework is presented, in which the plastic deformation gradient is chosen as the integration variable. Compared with the classic algorithm, a key feature of this new approach is that it can describe the finite deformation of crystals under thermal conditions. The obtained plastic deformation gradient contains not only plastic defor- mation but also thermal effects. The governing equation for the plastic deformation gradient is obtained based on ther- mal multiplicative decomposition of the total deformation gradient. An implicit method is used to integrate this evo- lution equation to ensure stability. Single crystal 1 100 aluminum is investigated to demonstrate practical applications of the model. The effects of anisotropic properties, time step, strain rate and temperature are calculated using this integration model.

关键词： Integration algorithm - Thermal effect Anisotropic elasticity Single crystal Finite deformation

Influences of fractional separation on the structure and reactivity of wheat straw cellulose for producing 5-hydroxymethylfurfural

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2024年第9期73卷 154-162页

作者： Di Wu ping hu hui Li Zhidan Xue Hang Lv Yimeng Guo Changwei hu Liangfang Zhu Key Laboratory of Green Chemistry and Technology Ministry of EducationCollege of ChemistrySichuan UniversityChengduSichuan 610064China

High-efficient production of 5-hydroxymethylfurfural(HMF),a“sleeping giant”in sustainable chemistry,from cellulose depends significantly on the effective separation of cellulose from lignocellulosic ***,we report the fractional separation of wheat straw cellulose(WSC)from wheat straw under solvothermal conditions using a mixed solvent of γ-valerolactone(GVL)and H_(2)O as the separating solvent,wherein the impacts of fractional separation parameters(solvent composition,temperature,and time)on removals of lignin and hemicellulose as well as purity and recovery of cellulose were studied by a Box-Behnken Design of response surface *** optimization of the solvothermal parameters enabled an optimal fractional separation condition(V_(GVL):~60.0%,T:205℃,t:~1.7 h)that led to a higher purity(89.4%)and recovery(86.7%)of cellulose in WSC.A further correlation of the removals of lignin and hemicellulose as well as purity and recovery of cellulose with the yield of HMF excluded an independent influence of the above ***,a comprehensive contribution of high fractional separation efficiency(defined as the product of cellulose purity and recovery)and low crystallinity of WSC was found to improve the HMF ***,the heat-and freeze-dryings of WSC after the solvothermal separation were found to lower the HMF molar yield because it re-improved the crystallinity of WSC.A high HMF molar yield of 58.6%was achieved after reacting wet-WSC in a mixed solvent of 1,4-dioxane and H_(2)O at 180℃for 20 min,which was 1.5 fold higher than that from microcrystalline *** work highlights the importance of enhancing the fractional separation efficiency of cellulose from lignocellulosic biomass while avoiding the drying process for future HMF biorefinery.

关键词： Biomass Separation Drying Crystallinity Wheat straw cellulose 5-Hydroxymethylfurfural

Synthesis of novel chiral phosphine-triazine ligand derived fromα-phenylethylamine for Pd-catalyzed asymmetric allylic alkylation

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2008年第3期19卷 261-263页

作者： Jia Di huang Xiang ping hu Zhuo Zheng Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 PR China Graduate School of Chinese Academy of Sciences Beijing 100039 PR China

A novel chiral phosphine-triazine ligand was synthesized from chiral α-phenylethylamine through a three-step procedure. In a model reaction of Pd-catalyzed allylic alkylation of rac-1,3-diphenylprop-2-en-1-y1 pivalat... 详细信息

关键词： Synthesis α-Phenylethylamine Phosphine-triazine ligand Pd-catalyzed allylic alkylation

Model Detection and Variable Selection for Varying Coefficient Models with Longitudinal Data

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2016年第3期32卷 331-350页

作者： San Ying FENG Yu ping hu Liu Gen XUE School of Mathematics and Statistics Zhengzhou University College of Applied Sciences Beijing University of Technology

In this puper, we consider the problem of variabie selection and model detection in varying coefficient models with longitudinM data. We propose a combined penalization procedure to select the significant variables, detect the true structure of the model and estimate the unknown regression coefficients simultaneously. With appropriate selection of the tuning parameters, we show that the proposed procedure is consistent in both variable selection and the separation of varying and constant coefficients, and the penalized estimators have the oracle property. Finite sample performances of the proposed method are illustrated by some simulation studies and the real data analysis.

关键词： Combined penalization longitudinal data model detection variable selection oracle property varying coefficient model

Tests for p-regression Coefficients in Linear Panel Model When p is Divergent

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2020年第3期36卷 566-580页

作者： Jing ZHAO Mi-xia WU Wei-hu CHENG Yao-hua RONG Yu-ping hu China National Institute of Standardization Beijing 100191China College of Applied Sciences Beijing University of TechnologyBeijing100124China School of Mathematics and Statistics Zhengzhou UniversityZhengzhou 450001China

This paper evaluates the performance of the FW-test for testing part of p-regression coefficients in linear panel data model when p is *** asymptotic power of the F_W-statistic is obtained under some regular *** theoretical development are challenging since the number of covariates increases as the sample size *** is worth noting that the inference approach does not require any specification of the error *** simulation comparisons are conducted and show that the simulated power coincide with theoretical power *** method is also illustrated using a renal cancer data example.

关键词： regression coefficient F_W-statistic Panel data

Effect of deep cryogenic treatment on mechanical behavior of a Cu-Cr-Zr alloy for electrodes of spot welding

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2005年第4期24卷 392-396页

作者： WANG Xiaofeng SHAN ping hu Shengsun WU Zhisheng WANG Xibao School of Material Science and Engineering Tianjin University Tianjin 300072 China

The effects of deep cryogenic treatment on mechanical behavior of a Cu-Cr-Zr alloy for electrodes of spot welding were investigated employing Brinell-hardness testing unit, abrasion examination machine, electronic almighty testing machine and X-ray stress analyzer. Tensile fracture surfaces of the alloy were characterized by scanning electronic microscope （SEM） with energy dispersive X-ray spectroscopy （EDS）. The results showed that, after deep cryogenic treatment, σb and σ0.2 increased 23 MPa and 21 MPa respectively, the wear rate of the alloy exhibited the trend of decrease with the decreasing temperature and increasing time of deep cryogenic treatment, and the surface residual stress of the alloy was partially eliminated by deep cryogenic treatment.

关键词： Cu-Cr-Zr alloy deep cryogenic treatment mechanical properties spot welding electrode

Application of grey relational analysis in sheet metal forming for multi-response quality characteristics

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第5期8卷 805-811页

作者： XIE Yan-min YU hu-ping CHEN Jun RUAN Xue-yu National Die ＆ Mold CAD Engineering Research Center Shanghai Jiao Tong University Shanghai 200030 China

The theory of grey systems is a new technique for performing prediction, relational analysis and decision making in many areas. In this paper, the use of grey relational analysis for optimizing the square hole flanging process parameters with considerations of the multiple response (the average flanging height, regular flanging and maximum strain) is introduced. Various flanging parameters, such as the blank inner radius rb, blank inner width B0, are considered. An orthogonal array is used for the experimental design. Multiple response values are obtained using finite element analysis (FEA). Optimal process parameters are determined by the grey relational grade obtained from the grey relational analysis for multi-performance characteristics (flanging height, regular flanging and maximum strain). Analysis of variance (ANOVA) for the grey relational grade is implemented. The results showed good agreement with the experiment result. Grey relational analysis can be applied in multiple response optimi-zation designs.

关键词： Grey relational analysis Flanging Multiple response Optimization design

High laser damage threshold coatings and damage testing technology

在线全文

学校读者我要写书评

暂无评论

光学精密工程 2005年第4期13卷 500-504页

作者： MA ping hu Jian-ping CHEN Song-lin TANG Ming WANG Zhen LI Wei XU Qiao Chengdu Fine Optical Engineering Research Center Chengdu 610041China

The laser-induced damage threshold(LIDT) of optical coating is a limited factor for development of a high peak power laser. The automatic damage testing facility was built to determine the LIDT of optics at 1 064 nm and 355 nm.. The cleanning and processing procedure of the substrate and coating technique were improved, and the damage resistance of high-reflective coating at 1 064 nm was increased.

关键词：激光涂覆技术 LIDT 自动机械光学仪器激光仪器