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Structural Stress-Fatigue Life Curve Improvement of Spot Welding Based on Quasi‑Newton Method

Chinese Journal of Mechanical Engineering 2020年第2期33卷 140-151页

作者： Yahang Qin Shoune Xiao Liantao Lu Bing Yang Xiangjie Li Guangwu Yang State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

ΔF-N curves are usually used to predict the fatigue life of spot welding in engineering,but they are time-consuming and laborious and not *** the purpose of predicting the fatigue life of spot welding accurately and efficiently,tensile-shear fatigue tests were conducted to obtain the fatigue life of spot-welded specimens with different sheet thicknesses *** specimens were simulated by using the finite element method,and the structural stress was theoretically *** the double logarithmic coordinate system,the structural stress-fatigue life(S-N)curve of spot welding was fitted by the least-squares method,based on the quasi-Newton *** square of the correlation coefficient of the S-N curve was taken as the optimization objective,with the correction coefficients of force,bending moment,spot welding diameter,and sheet thickness as the *** the optimization process,three different ways were utilized to get three optimized spot welding S-N curves,which are suitable for different *** results show that the fitting effect of the S-N curve is improved,the data points are more compact,and the optimization effect is *** S-N curves can be used to predict the fatigue life,which provide the basis for practical engineering application.

关键词： Spot welding Structural stress S-N curve Quasi-Newton method correction coefficient

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维普期刊数据库

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Shear strength of frozen clay under freezing-thawing cycles using triaxial tests

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Earthquake Engineering and Engineering Vibration 2018年第4期17卷 761-769页

作者： Wang Miao Meng Shangjiu Sun Yiqiang Fu Haiqing Institute of Engineering Mechanics China Earthquake Administration Harbin 150080 China Key Laboratory of Earthquake Engineering and Engineering Vibration China Earthquake Administration College of Civil Engineering andArchitecture Harbin University of Science and Technology Harbin 150080 China Shandong Earthquake Administration Jinan 250014 China

Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycles on clay static strength, cohesion and internal friction angles is proposed, and the change patterns, correction curves and regressive formulae of clay static strength, cohesion and internal friction angles under freezing-thawing cycles are given. The test results indicate that with increasing numbers of freezing-thawing cycles, the clay static strength and cohesion decrease exponentially but the internal friction angle increases exponentially. The performance of static strength, cohesion and internal friction angles are different with increasing numbers of freezing-thawing cycles, i.e., the static strength decreases constantly until about 30% of the initial static strength prior to the freezing-thawing cycling and then stays basically stable. After 5-7 freezing-thawing cycles, the cohesion decreases gradually to about 70% of the initial cohesion. The internal friction angle increases about 20% after the first freezing-thawing cycle, then increases gradually close to a stable value which is an increase of about 40% of the internal friction angle. The freezing-thawing process can increase the variation of the density of the soil samples; therefore, strict density discreteness standards of frozen soil sample preparation should be established to ensure the reliability of the test results.

关键词： seasonally frozen soil freezing-thawing cycles cohesion internal friction angle correction coefficient

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维普期刊数据库

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Irreversible demagnetization mechanism of permanent magnets during electromagnetic buffering

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Defence Technology（防务技术） 2021年第3期17卷 763-774页

作者： Zi-xuan Li Guo-lai Yang Yu-meng Fan Jia-hao Li School of Mechanical Engineering Nanjing University of Science and TechnologyNanjingPR China

The permanent magnets will be irreversibly demagnetized under high temperature and high velocity during the electromagnetic *** this study,the magnetic field induced by eddy currents and the self-demagnetizing field of permanent magnet are taken into consideration together for demagnetization *** magnetic Reynolds number is used to express the eddy currents *** correction coefficient being expressed as the index of the air-gap width,the inner cylinder thickness,iron pole axial length and the permanent magnet demagnetization coefficient is introduced by magnetic path analysis to represent the self-demagnetization effect and the demagnetization *** electromagnetic buffer(EMB)prototype is tested under intensive impact loads of different strengths at room *** accuracy of the nonlinear irreversible demagnetization finite element model is verified by demagnetization on damping force,velocity and ***,high-velocity demagnetization and high-temperature demagnetization are analysed in order to obtain the distribution law of irreversible demagnetization.

关键词： EMB Irreversibly demagnetization Magnetic Reynolds number correction coefficient

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维普期刊数据库

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Research on Measuring Method of Dynamic Collapse Velocity of Steering Column in Vehicle Collision Test

Research on Measuring Method of Dynamic Collapse Velocity of...

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2019中国汽车工程学会年会

作者： Li Jiayao Yin Changqing Xu Ai Li Xiaolei Cui Taisong Zhao Hui Chongqing Changan Automobile Co. Ltd. State Key Laboratory of Vehicle NVH and Safety Technology

The low-cost and easy-to-operate method for measuring the dynamic collapse velocity of steering column is realized,and the problem that the dynamic collapse displacement of steering column can not be measured in the vehicle crash test is *** other words,an acceleration steensor is installead on the colupper and lower cylinder of the steering column to measure the collapse acceleration of the steering column when the dummy impacts the steering *** modifying the measured acceleration and integrating the acceleration,the collapse velocity and the collapse time of steering column are ***,the measurement results are validated by the sled test and high-speed video *** is confirmed that this method can be used to measure the collapse parameters of steering column in the vehicle collision test.

关键词： steering column dynamic collapse velocity correction coefficient collapse time collision test

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Research on Calculating Formula of Self-Weight of Column-Supported Space Truss

Research on Calculating Formula of Self-Weight of Column-Sup...

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作者： Bin Xu Yong Wang Yijing Zhu Hao Huang Xuzhou College of Industrial Technology

With the rapid development of steel structure engineering in China,grid structure has been widely *** the self-weight of space truss,the current regulations give the corresponding calculation formula,but in practical engineering applications,it is found that the calculation formula for column-supported space truss has poor ***,in this paper,the adaptability of the formula is analyzed according to the current self-weight calculation formula for cylindrical point supported space truss,and the self-weight estimation of the space truss is revised on the basis of statistics and regression *** formula modification can improve the applicability of the grid estimation formula,and also provide some reference for the revision of relevant codes and regulations.

关键词： Column support deadweight calculation correction coefficient

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