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dynamic resistance and Energy Absorption of Sandwich Beam via a Micro-Topology Optimization

Chinese Journal of Mechanical Engineering 2024年第4期37卷 146-162页

作者： Shiqiang Li Yuwei Li Xiaomin Ma Jianguang Fang Zhifang Liu Zhihua Wang Institute of Applied Mechanics Taiyuan University of TechnologyTaiyuan 030024China Shanxi Key Laboratory of Material Strength and Structural Impact Taiyuan University of TechnologyTaiyuan 030024China School of Civil and Environmental Engineering University of Technology SydneySydneyNSW 2007Australia

The current research of sandwich structures under dynamic loading mainly focus on the response characteristic of *** micro-topology of core layers would sufficiently influence the property of sandwich ***,the micro deformation and topology mechanism of structural deformation and energy absorption are *** this paper,based on the bi-directional evolutionary structural optimization method and periodic base cell(PBC)technology,a topology optimization frame work is proposed to optimize the core layer of sandwich *** objective of the present optimization problem is to maximize shear stiffness of PBC with a volume *** effects of the volume fraction,filter radius,and initial PBC aspect ratio on the micro-topology of the core were *** dynamic response process,core compression,and energy absorption capacity of the sandwich beams under blast impact loading were analyzed by the finite element *** results demonstrated that the overpressure action stage was coupled with the core compression *** the same loading and mass per unit area,the sandwich beam with a 20%volume fraction core layer had the best blast *** filter radius has a slight effect on the shear stiffness and blast resistances of the sandwich *** increasing the filter radius could slightly improve the bending *** changing the initial PBC aspect ratio,there are three ways for PBC evolution:The first is to change the angle between the adjacent bars,the second is to further form holes in the bars,and the third is to combine the first two ***,not all three ways can improve the energy absorption capacity of the *** the aspect ratio of the PBC arbitrarily may lead to worse *** studies are necessary for further detailed *** research proposes a new topology sandwich beam structure by micro-topology optimization,which has sufficient shear *** micro mechanism of structural

关键词： Topology optimization Sandwich beam Impact loading dynamic resistance Energy absorption Micro mechanism

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Time-dependent development of dynamic resistance voltage of superconducting tape considering heat accumulation

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Superconductivity 2023年第4期8卷 43-52页

作者： Chao Li Yuying Xing Ying Xin Bin Li Francesco Grilli Tianjin University School of Electrical and Information EngineeringTianjinChina State Grid Tianjin Electric Power Company Chengnan Power Supply Branch TianjinChina Karlsruhe Institute of Technology Institute for Technical PhysicsKarlsruheGermany

In flux pumps,motors and superconducting magnets,the high temperature superconductor(HTS)coated conductor frequently carries a DC transport current when an oscillating magnetic field is present in the *** this circumstance,the interesting effect of dynamic resistance takes place,which can affect the operating performance of superconducting devices:heat accumulation can contribute to the rising temperature of the HTS tape and the dynamic resistance voltage can change *** article explores the time‐dependent development of the dynamic resistance voltage using a numerical modeling considering the thermal *** a validation against experimental results,this work investigates the effects of several factors on the structure of the HTS tape on the time‐dependent development of the dynamic resistance,thus providing insights toward a better understanding of the time‐dependent behavior of HTS tapes under external magnetic fields.

关键词： dynamic resistance High temperature superconductor Electromagnetic‐thermal coupling Finite element method REBCO coated conductors

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Measurement of dynamic resistance in resistance spot welding

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China Welding 2007年第4期16卷 42-46页

作者：武佩吕佳珩 Wenqi Zhang Niels Bay School of Mechanical and Electrical Engineering Inner Mongolia Agricultural University Huhhot 010018 SWANTEC Software and Engineering ApS Hoersholm DK-2970 Denmark Department of Manufacturing Engineering and Management Technical University of Denmark Lyngby Dk-2800 Denmark.

The conventional methods of determining the dynamic resistance were mostly done by measuring the voltage and current at secondary side of transformer in resistance welding machines, in which the measuring set-up normally interferes with the movement of electrode, and the measuring precision is influenced by inductive noise caused by the high welding current. In this study, the dynamic resistance is determined by measuring the voltage at primary side and current at secondary side. This increases the accuracy of measurement because of higher signal-noise ratio, and allows to apply to in-process system without any wires connected to electrodes.

关键词： resistance spot welding dynamic resistance contact resistance circuit analysis

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An analysis of the dynamic resistance and the instantaneous energy of the CO_2 arc welding process

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China Welding 2007年第1期16卷 77-82页

作者：王振民薛家祥董飞杨国华陆晓明 School of Mechanical Engineering South China University of TechnologyGuangzhou 510640

A self-developed welding dynamic arc wavelet analyzer was adopted to analyze and assess the welding process of two CO2 arc welding machines. The experimental results indicate that the instantaneous energy can reflect the influence of the welding current and voltage on dynamic arc characteristic synthetically. Through calculating and analyzing the instantaneous energy, the energy during arc ignition and short circuit in CO2 welding process can be confirmed rationally, thus the foundation for the accurate design and control of the welding current and voltage can be provided. By reducing the ripple disturbance of the dynamic resistance, avoiding peak current and voltage waveform , and enhancing the transition frequency of short circuit suitably, the stability of the welding arc and the weld appearance can be improved.

关键词： instantaneous energy dynamic resistance arc stability repeatability of waveform

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Effect of the dynamic resistance on the Maximum Output Power in dynamic Modelling of Photovoltaic Solar Cells

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Open Journal of Modelling and Simulation 2022年第1期10卷 48-57页

作者： Siaka Touré Solar Energy Laboratory Félix Houphou&#235t-Boigny University of Abidjan Cocody Abidjan C&#244te d’Ivoire

Several studies on PV solar cells are found in the literature which use static models. Those models are mainly one-diode, two-diode or three-diode models. In the dynamic modelling, a variable parallel capacitance is incorporated. Unlike the previous studies which do not clearly establish a relationship between the capacitance and the voltage, in the present paper, the link between the capacitance and the voltage is investigated and established. In dynamic modelling investigated in this paper, the dynamic resistance is introduced in the modelling of the solar cell. It is introduced in the current-voltage characteristic. The value of the dynamic resistance is evaluated at the maximum power point and its effect on the maximum power is investigated. The study shows for the first time, that the dynamic resistance must be introduced in the current-voltage characteristic, because it has an influence on the PV cell output.

关键词： Photovoltaic Solar Cells dynamic Modelling dynamic resistance Diffusion Capacitance Transition Capacitance

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Analysis of the Correlation between the Level of Contact Degradation and the dynamic resistance Curve in Circuit Breakers

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Journal of Energy and Power Engineering 2014年第6期8卷 1104-1111页

作者： Ronimack Trajano de Souza Edson Guedes da Costa Department of Electrical Engineering Campina Grande Federal University Campina Grande 58429-900 Brazil

The DRM （dynamic contact resistance measurement） in high voltage circuit breakers is a manner of evaluating the internal ageing condition of the chamber. DRM is similar to static contact resistance measurement testing, but instead of measuring a single value when the breaker contacts are closed （static value）, the ohmic resistance is measured at various contact positions, from the beginning of the contact opening until a complete separation of the contacts. The relationship between the contact resistances of the new circuit breaker and the ageing circuit breaker in operation provides subsidy for the evaluation of both the main and arcing contact conditions. This research aims to analyze the correlation between the various levels of degradation of the contacts and the configuration of the DRM curve. This work considers curve samples from new acceleration tests. breaker chamber contacts and different levels of degradation by

关键词： DRM (dynamic contact resistance measurement) circuit breaker dynamic resistance contact resistance resistance curve.

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Multi-field dynamic modeling and numerical simulation of aluminum alloy resistance spot welding

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Transactions of Nonferrous Metals Society of China 2012年第12期22卷 3066-3072页

作者：陶建峰贡亮刘成良赵阳上海交通大学机械与动力工程学院机电控制研究所上海200240 上海信聚科技有限公司上海201030

In order to explore the influence of welding parameters and to investigate the Al alloy (AA) nugget formation process, a comprehensive model involving electrical-thermal-mechanical and metallurgical analysis was established to numerically display the resistance spot welding (RSW) process within multiple fields and understand the AA-RSW physics. A multi-disciplinary finite element method (FEM) framework and a empirical sub-model were built to analyze the affecting factors on weld nugget and the underlying nature of welding physics with dynamic simulation procedure. Specifically, a counter-intuitive phenomenon of the resistance time-variation caused by the transient inverse virtual variation (TIVV) effect was highlighted and analyzed on the basis of welding current and temperature distribution simulation. The empirical model describing the TIVV phenomenon was used for modifying the dynamic resistance simulation during the AA spot welding process. The numerical and experimental results show that the proposed multi-field FEM model agrees with the measured AA welding feature, and the modified dynamic resistance model captures the physics of nugget growth and the electrical-thermal behavior under varying welding current and fluctuating heat input.

关键词： resistance spot welding aluminum alloy multi-field modeling simulation finite element method dynamic resistance transient inverse virtual variation effect

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Mechanism of Wireless Power Transfer System Waveform Distortion Caused by Nonideal Gallium Nitride Transistor Characteristics

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Chinese Journal of Electrical Engineering 2021年第2期7卷 61-69页

作者： Shaoyu Sun Jianshan Zhang Wengang Wu Ling Xia Yufeng Jin Shenzhen Graduate School Peking UniversityShenzhen 518055China Institute of Microelectronics Peking UniversityBeijing 100871China Shenzhen Hai Li Tech. Inc.Shenzhen 518129China

Gallium nitride(GaN)field-effect transistors have low ON resistance and switching losses in high-frequency(>MHz)resonant wireless power transfer ***,their performance in the system is determined by their characteristics and operation mode.A particular operating mode in a 6.78-MHz magnetic resonant wireless transfer system that employs class-D GaN power amplifiers in the zero-voltage switching mode is *** operation modes,the forward mode and the reverse mode,are *** nonideal effect under the device-level dynamic resistance and thermal effect are also *** dynamic resistance under different operation modes is demonstrated to have different generation ***,the device characteristics with system operating conditions are combined,and the effects of temperature and dynamic resistance under different operating conditions are evaluated.

关键词： GaN wireless power transfer dynamic resistance thermal effect

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Numerical simulation of dynamic loss and total loss in the REBCO tapes under perpendicular AC magnetic fields up to 8 T at 20 K and 50 K

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Superconductivity 2024年第3期11卷 80-92页

作者： Yuhui Zhang Yueming Sun Nicholas M Strickland Zhenan Jiang Robinson Research Institute Victoria University of WellingtonLower Hutt 5010New Zealand

REBCO tapes carry DC current under AC magnetic fields in proposed HTS fusion applications. AC loss will be generated in the process and it is important to understand the AC loss behaviour for safe operation of the fusion magnets. In this work, magnetisation loss (Qm), dynamic resistance (Rdyn), and total loss (Qtotal) in four different REBCO tapes are numerically studied, using the measured and , for the magnetic field amplitude applied perpendicularly up to 8 T at 20 K and 50 K, where represents the magnetic field and field angle () dependent critical current density. The peak of Theva data is different from that of other tapes. We artificially shifted the ab-plane peak of Theva to the left by 25° to match the peak value. The newly shifted data is named as Theva-shift, which was also investigated to study the influence of the Theva peak shift on AC loss. The normalised DC transport current level (i = It/Ic0) ranges from 0.05 to 0.9, where the DC current amplitude and the self-critical current of the tape are represented by It and Ic0, respectively. The simulation results show that the AC losses deviate significantly from the Brandt-Indenbom (BI) equation at high magnetic fields. Jc and instantaneous loss curves for different tapes show correlation at high magnetic fields. The simulation results also show how different characteristics for different tapes influence AC losses. When AC loss values are scaled by the self-field critical current, Qm without current and Qtotal with current in the different tapes show a good agreement. It implies that the temperature dependence of the two types of loss can be calculated from a known loss at one temperature and the self-field critical current.

关键词： REBCO tapes Magnetisation loss dynamic resistance Total loss Scaling law

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A Study of Spot Welding of Advanced High Strength Steels for Automotive Applications

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Journal of Iron and Steel Research International 2011年第S1期18卷 724-729页

作者： Bhole S.D Khan M.S Department of Mechanical and Industrial Engineering Ryerson University350 Victoria StreetTorontoONM5B 2K3Canada

The application of advanced high strength steels in automotive industry has highlighted the need for research into spot weldability of these *** weld lobe diagrams,the spot weldability of DP600 steel was found to be poor with conventional weld *** enhanced weld schedule consisting of two pulses with reduced current on the second pulse gave a substantial increase in the lobe width;the first pulse removed the zinc coating and the second pulse controlled the nugget growth.A data acquisition system was designed to monitor weld expulsion during the weld *** the three possible control strategies proposed,especially with AC welding equipment,the dynamic resistance signal is easily obtained and the least *** phenomena,microstructural characterization and mechanical properties of spot-welded hot dipped galvanized DP600 steel and interstitial free steel were *** work on dissimilar welds in DP 600 and HSLA 350 was also conducted with emphasis on tensile and fatigue properties and fracture *** performance of dissimilar spot welds was different from that of the similar spot welds in each of the HSLA350 and DP600 *** DP600 weld properties played a dominating role in the hardness and tensile properties of the dissimilar spot ***,the fatigue performance of the dissimilar welds was similar to that of the HSLA *** will be presented at the conference.

关键词： resistance spot welding dynamic resistance nugget diameter and hardness dissimilar materials microstructure mechanical properties fatigue fracture mode

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