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Microstructure and thermal properties of dissimilar M300–CuCr1Zr alloys by multi-material laser-based powder bed fusion 被引量:1
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作者 Xiaoshuang Li Dmitry Sukhomlinov Zaiqing Que 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CSCD 2024年第1期118-128,共11页
Multi-material laser-based powder bed fusion (PBF-LB) allows manufacturing of parts with 3-dimensional gradient and additional functionality in a single step. This research focuses on the combination of thermally-cond... Multi-material laser-based powder bed fusion (PBF-LB) allows manufacturing of parts with 3-dimensional gradient and additional functionality in a single step. This research focuses on the combination of thermally-conductive CuCr1Zr with hard M300 tool steel.Two interface configurations of M300 on CuCr1Zr and CuCr1Zr on M300 were investigated. Ultra-fine grains form at the interface due to the low mutual solubility of Cu and steel. The material mixing zone size is dependent on the configurations and tunable in the range of0.1–0.3 mm by introducing a separate set of parameters for the interface layers. Microcracks and pores mainly occur in the transition zone.Regardless of these defects, the thermal diffusivity of bimetallic parts with 50vol% of CuCr1Zr significantly increases by 70%–150%compared to pure M300. The thermal diffusivity of CuCr1Zr and the hardness of M300 steel can be enhanced simultaneously by applying the aging heat treatment. 展开更多
关键词 multi-material additive manufacturing laser-based powder bed fusion thermal diffusivity dissimilar metals copper alloy
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Probabilistic-Ellipsoid Hybrid Reliability Multi-Material Topology Optimization Method Based on Stress Constraint
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作者 Zibin Mao Qinghai Zhao Liang Zhang 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第7期757-792,共36页
This paper proposes a multi-material topology optimization method based on the hybrid reliability of the probability-ellipsoid model with stress constraint for the stochastic uncertainty and epistemic uncertainty of m... This paper proposes a multi-material topology optimization method based on the hybrid reliability of the probability-ellipsoid model with stress constraint for the stochastic uncertainty and epistemic uncertainty of mechanical loads in optimization design.The probabilistic model is combined with the ellipsoidal model to describe the uncertainty of mechanical loads.The topology optimization formula is combined with the ordered solid isotropic material with penalization(ordered-SIMP)multi-material interpolation model.The stresses of all elements are integrated into a global stress measurement that approximates the maximum stress using the normalized p-norm function.Furthermore,the sequential optimization and reliability assessment(SORA)is applied to transform the original uncertainty optimization problem into an equivalent deterministic topology optimization(DTO)problem.Stochastic response surface and sparse grid technique are combined with SORA to get accurate information on the most probable failure point(MPP).In each cycle,the equivalent topology optimization formula is updated according to the MPP information obtained in the previous cycle.The adjoint variable method is used for deriving the sensitivity of the stress constraint and the moving asymptote method(MMA)is used to update design variables.Finally,the validity and feasibility of the method are verified by the numerical example of L-shape beam design,T-shape structure design,steering knuckle,and 3D T-shaped beam. 展开更多
关键词 Stress constraint probabilistic-ellipsoid hybrid topology optimization reliability analysis multi-material design
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Multi-Material Topology Optimization of 2D Structures Using Convolutional Neural Networks
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作者 Jiaxiang Luo Weien Zhou +2 位作者 Bingxiao Du Daokui Li Wen Yao 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第8期1919-1947,共29页
In recent years,there has been significant research on the application of deep learning(DL)in topology optimization(TO)to accelerate structural design.However,these methods have primarily focused on solving binary TO ... In recent years,there has been significant research on the application of deep learning(DL)in topology optimization(TO)to accelerate structural design.However,these methods have primarily focused on solving binary TO problems,and effective solutions for multi-material topology optimization(MMTO)which requires a lot of computing resources are still lacking.Therefore,this paper proposes the framework of multiphase topology optimization using deep learning to accelerate MMTO design.The framework employs convolutional neural network(CNN)to construct a surrogate model for solving MMTO,and the obtained surrogate model can rapidly generate multi-material structure topologies in negligible time without any iterations.The performance evaluation results show that the proposed method not only outputs multi-material topologies with clear material boundary but also reduces the calculation cost with high prediction accuracy.Additionally,in order to find a more reasonable modeling method for MMTO,this paper studies the characteristics of surrogate modeling as regression task and classification task.Through the training of 297 models,our findings show that the regression task yields slightly better results than the classification task in most cases.Furthermore,The results indicate that the prediction accuracy is primarily influenced by factors such as the TO problem,material category,and data scale.Conversely,factors such as the domain size and the material property have minimal impact on the accuracy. 展开更多
关键词 multi-material topology optimization convolutional neural networks deep learning finite element analysis
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MGMT activated by Wnt pathway promotes cisplatin tolerance through inducing slow-cycling cells and nonhomologous end joining in colorectal cancer
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作者 Haowei Zhang Qixin Li +9 位作者 Xiaolong Guo Hong Wu Chenhao Hu Gaixia Liu Tianyu Yu Xiake Hu Quanpeng Qiu Gang Guo Junjun She Yinnan Chen 《Journal of Pharmaceutical Analysis》 SCIE CAS CSCD 2024年第6期863-877,共15页
Chemotherapy resistance plays a pivotal role in the prognosis and therapeutic failure of patients with colorectal cancer(CRC).Cisplatin(DDP)-resistant cells exhibit an inherent ability to evade the toxic chemotherapeu... Chemotherapy resistance plays a pivotal role in the prognosis and therapeutic failure of patients with colorectal cancer(CRC).Cisplatin(DDP)-resistant cells exhibit an inherent ability to evade the toxic chemotherapeutic drug effects which are characterized by the activation of slow-cycle programs and DNA repair.Among the elements that lead to DDP resistance,O^(6)-methylguanine(O^(6)-MG)-DNA-methyltransferase(MGMT),a DNA-repair enzyme,performs a quintessential role.In this study,we clarify the significant involvement of MGMT in conferring DDP resistance in CRC,elucidating the underlying mechanism of the regulatory actions of MGMT.A notable upregulation of MGMT in DDP-resistant cancer cells was found in our study,and MGMT repression amplifies the sensitivity of these cells to DDP treatment in vitro and in vivo.Conversely,in cancer cells,MGMT overexpression abolishes their sensitivity to DDP treatment.Mechanistically,the interaction between MGMT and cyclin dependent kinase 1(CDK1)inducing slow-cycling cells is attainted via the promotion of ubiquitination degradation of CDK1.Meanwhile,to achieve nonhomologous end joining,MGMT interacts with XRCC6 to resist chemotherapy drugs.Our transcriptome data from samples of 88 patients with CRC suggest that MGMT expression is co-related with the Wnt signaling pathway activation,and several Wnt inhibitors can repress drug-resistant cells.In summary,our results point out that MGMT is a potential therapeutic target and predictive marker of chemoresistance in CRC. 展开更多
关键词 Colorectal cancer MGMT Chemotherapy resistance Slow-cycling cells Nonhomologous end joining Wnt pathway
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Effect of hydrogen fluoride and magnesium oxide on AZ31 Mg alloy/carbon fiber-reinforced plastic composite by thermal laser joining technique
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作者 Andrews Nsiah Ashong Barton Mensah Arkhurst +2 位作者 Youn Seoung Lee Mok-Young Lee Jeoung Han Kim 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2024年第7期2874-2889,共16页
Although hydrofluoric acid(HF)surface treatment is known to enhance the joining of metals with polymers,there is limited information on its effect on the joining of AZ31 alloy and carbon-fiber-reinforced plastics(CFRP... Although hydrofluoric acid(HF)surface treatment is known to enhance the joining of metals with polymers,there is limited information on its effect on the joining of AZ31 alloy and carbon-fiber-reinforced plastics(CFRPs)through laser-assisted metal and plastic direct joining(LAMP).This study uses the LAMP technique to produce AZ31-CFRP joints.The joining process involves as-received AZ31,HFpretreated AZ31,and thermally oxidized HF-pretreated AZ31 alloy sheets.Furthermore,the bonding strength of joints prepared with thermally oxidized AZ31 alloy sheets is examined to ascertain the combined effect of HF treatment and thermal oxidation on bonding strength.The microstructures,surface chemical interactions,and mechanical performances of joints are investigated under tensile shear loading.Various factors,such as bubble formation,CFRP resin decomposition,and mechanical interlocking considerably affect joint strength.Additionally,surface chemical interactions between the active species on metal parts and the polar amide along with carbonyl groups of polymer play a significant role in improving joint strength.Joints prepared with surface-pretreated AZ31 alloy sheets show significant improvements in bonding strength. 展开更多
关键词 Thermal laser joining Thermal oxidation Hydrofluoric acid pretreatment Mechanical interlocking Covalent bonds Chemical interactions
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Study on Key Joining Technology and Test Method of Steel/Al Hybrid Structure Body-in-White
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作者 Lijun Han Fuyang Liu Changhua Liu 《Journal of Materials Science and Chemical Engineering》 2024年第4期104-118,共15页
Green and low carbon promote the application and development of light-weight materials in body-in-white. Large-scale die-casting Al alloy (DCAA) and high-strength thermo-formed steel sheet (TFSS) have put forward high... Green and low carbon promote the application and development of light-weight materials in body-in-white. Large-scale die-casting Al alloy (DCAA) and high-strength thermo-formed steel sheet (TFSS) have put forward higher requirements for the application of joining technology of high-strength steel/Al dissimilar materials. Taking the new die-casting Al alloy body as an example, this paper systematically studies the progress of the latest joining methods of steel/Al dissimilar material with combination of two-layer plate and three-layer plate. By analyzing the joining technologies such as FSPR, RES, FDS and SPR, the technology and process characteristics of steel/Al dissimilar material joining are studied, and the joining technical feasibility and realization means of different material combination of the body are analyzed. The conditions of material combination, material thickness, material strength, flange height, preformed holes and joint spacing for achieving high-quality joining are given. The FSPR joining technology is developed and tested in order to meet with the joining of parts with DCAA and TFSS, especially for the joining of three-layer plates with them. It finds the method and technical basis for the realization of high quality joining of dissimilar materials, provides the early conditions for the application of large DCAA and TFSS parts in body-in-white, and meets the design requirements of new energy body. . 展开更多
关键词 BODY-IN-WHITE LIGHTWEIGHT Die-Casting Al Alloy Thermo-Formed Steel joining
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Challenge to Welding and Joining Technology for Applying Multi-material in Electric Vehicle Production
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作者 Tomoyuki Ueyama Shinichi Hasegawa +2 位作者 Takaaki Miyauchi Testuo Era Hidetoshi Fujii 《材料科学与工程(中英文A版)》 2022年第4期107-114,共8页
Advanced high strength steel,aluminum alloy and plastic materials are used in the right places for the purpose of reducing the weight of EV(electric vehicle)bodies and in-vehicle parts,and multi-material structures ar... Advanced high strength steel,aluminum alloy and plastic materials are used in the right places for the purpose of reducing the weight of EV(electric vehicle)bodies and in-vehicle parts,and multi-material structures are advancing.Therefore,it is difficult to handle the welding and joining processes of automobile structures by the conventional arc welding and resistance spot welding,which have been applied to steel joining,and various joining processes are being applied depending on the material.Under above mentioned background,the authors have developed some unique joining processes for multi-materials that are used in the right place.This paper introduces the dissimilar metal joining between the galvanized steel and aluminum alloy by laser arc hybrid process,the metal/thermoplastic dissimilar material joining using laser process and the solid-state resistance spot joining process of advanced high strength steel for EV body structural parts.Moreover,the authors describe the high-speed plasma jet GTA(Gas Tungusten Arc)welding process of copper applied to electrical components such as motors. 展开更多
关键词 Arc welding laser arc hybrid dissimilar joining spot joining electric vehicle.
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Simultaneous multi-material embedded printing for 3D heterogeneous structures 被引量:4
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作者 Ziqi Gao Jun Yin +4 位作者 Peng Liu Qi Li Runan Zhang Huayong Yang Hongzhao Zhou 《International Journal of Extreme Manufacturing》 SCIE EI CAS CSCD 2023年第3期485-498,共14页
In order to mimic the natural heterogeneity of native tissue and provide a better microenvironment for cell culturing,multi-material bioprinting has become a common solution to construct tissue models in vitro.With th... In order to mimic the natural heterogeneity of native tissue and provide a better microenvironment for cell culturing,multi-material bioprinting has become a common solution to construct tissue models in vitro.With the embedded printing method,complex 3D structure can be printed using soft biomaterials with reasonable shape fidelity.However,the current sequential multi-material embedded printing method faces a major challenge,which is the inevitable trade-off between the printed structural integrity and printing precision.Here,we propose a simultaneous multi-material embedded printing method.With this method,we can easily print firmly attached and high-precision multilayer structures.With multiple individually controlled nozzles,different biomaterials can be precisely deposited into a single crevasse,minimizing uncontrolled squeezing and guarantees no contamination of embedding medium within the structure.We analyse the dynamics of the extruded bioink in the embedding medium both analytically and experimentally,and quantitatively evaluate the effects of printing parameters including printing speed and rheology of embedding medium,on the 3D morphology of the printed filament.We demonstrate the printing of double-layer thin-walled structures,each layer less than 200μm,as well as intestine and liver models with 5%gelatin methacryloyl that are crosslinked and extracted from the embedding medium without significant impairment or delamination.The peeling test further proves that the proposed method offers better structural integrity than conventional sequential printing methods.The proposed simultaneous multi-material embedded printing method can serve as a powerful tool to support the complex heterogeneous structure fabrication and open unique prospects for personalized medicine. 展开更多
关键词 embedded printing multi-material printing PRINTABILITY soft materials heterogeneous structures
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Evaluation of different crosslinking methods in altering the properties of extrusion-printed chitosan-basedmulti-material hydrogel composites 被引量:2
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作者 Suihong Liu Haiguang Zhang +4 位作者 Tilman Ahlfeld David Kilian Yakui Liu Michael Gelinsky Qingxi Hu 《Bio-Design and Manufacturing》 SCIE EI CAS CSCD 2023年第2期150-173,共24页
Three-dimensional printing technologies exhibit tremendous potential in the advancing fields of tissue engineering and regenerative medicine due to the precise spatial control over depositing the biomaterial.Despite t... Three-dimensional printing technologies exhibit tremendous potential in the advancing fields of tissue engineering and regenerative medicine due to the precise spatial control over depositing the biomaterial.Despite their widespread utilization and numerous advantages,the development of suitable novel biomaterials for extrusion-based 3D printing of scaffolds that support cell attachment,proliferation,and vascularization remains a challenge.Multi-material composite hydrogels present incredible potential in this field.Thus,in this work,a multi-material composite hydrogel with a promising formulation of chitosan/gelatin functionalized with egg white was developed,which provides good printability and shape fidelity.In addition,a series of comparative analyses of different crosslinking agents and processes based on tripolyphosphate(TPP),genipin(GP),and glutaraldehyde(GTA)were investigated and compared to select the ideal crosslinking strategy to enhance the physicochemical and biological properties of the fabricated scaffolds.All of the results indicate that the composite hydrogel and the resulting scaffolds utilizing TPP crosslinking have great potential in tissue engineering,especially for supporting neo-vessel growth into the scaffold and promoting angiogenesis within engineered tissues. 展开更多
关键词 multi-material composite hydrogel Crosslinking mechanism CHITOSAN GELATIN Egg white 3D printing
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AN URGENT JOINT CAUSE
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《China Today》 2024年第12期24-25,共2页
COP29-the 29th session of the Conference of the Parties to the United Nations Framework Convention on Climate Change-has accentuated the urgency of jointly addressing climate change,our common global threat,by pushing... COP29-the 29th session of the Conference of the Parties to the United Nations Framework Convention on Climate Change-has accentuated the urgency of jointly addressing climate change,our common global threat,by pushing for a fair and ambitious new climate financing target.It has also brought into the global spotlight China’s progress in green transition and carbon emission reduction and its commitment to international cooperation. 展开更多
关键词 join jointly GLOBAL
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Progress in Joining Ceramics to Metals 被引量:16
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作者 ZHANG Yong FENG Di HE Zhi-yong CHEN Xi-chun 《Journal of Iron and Steel Research International》 SCIE EI CAS CSCD 2006年第2期1-5,共5页
The research and development of joining methods of ceramics to metals, especially brazing, diffusion bonding and partial transition liquid phase bonding, were introduced. Some opinions were put forward. For new compos... The research and development of joining methods of ceramics to metals, especially brazing, diffusion bonding and partial transition liquid phase bonding, were introduced. Some opinions were put forward. For new composites emerging, it is necessary to develop new joining methods, particularly in the field of high temperature technique for joining ceramics to superalloys. 展开更多
关键词 CERAMIC METAL joining PROGRESS
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Joining Performance and Microstructure of the 2024/7075 Aluminium Alloys Welded Joints by Vaporizing Foil Actuator Welding 被引量:5
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作者 孟正华 WANG Xu +4 位作者 GUO Wei HU Zhili Anupam Vivek HUA Lin Glenn S DAEHN 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2019年第2期368-372,共5页
Vaporizing foil actuator welding(VFAW) was used for joining 2024-T3 and 7075-T6 aluminum alloy sheets, and the resulting joint microstructure was analyzed. 2024/7075 aluminum alloy pairs with suitable processing param... Vaporizing foil actuator welding(VFAW) was used for joining 2024-T3 and 7075-T6 aluminum alloy sheets, and the resulting joint microstructure was analyzed. 2024/7075 aluminum alloy pairs with suitable processing parameters can be prepared by using VFAW. Dynamic preform addresses the poor formability problem of target material and advantage of VFAW on dissimilar materials in some conditions. But with standoff sheet inserting in the flyer and target, 2024/7075 welded pairs gets the better weld strength, compared with flyer preformed method. The microstructure of the circular weld area of the welded joint showed a wave interface, in which a thin melt layer formed at the center and edge parts. The crystal grains near the bonding interface were remarkably elongated and refined. Therefore, the joining of the 2024/7075 pairs was facilitated through plastic forming and melting. 展开更多
关键词 impact WELDING dissimilar materials vaporizing FOIL ACTUATOR joining INTERFACE
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Kinematics Analysis and Optimization of the Fast Shearing-extrusion Joining Mechanism for Solid-state Metal 被引量:5
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作者 ZHANG Shuangjie YAO Yunfeng +3 位作者 LI Lingchong WANG Lijuan LI Junxia LI Qiang 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2015年第6期1123-1131,共9页
Dynamical Joining of the solid-state metal is the key technology to realize endless hot rolling. The heating and laser welding method both require long joining time. Based on super deformation method, a 7-bar and 2-sl... Dynamical Joining of the solid-state metal is the key technology to realize endless hot rolling. The heating and laser welding method both require long joining time. Based on super deformation method, a 7-bar and 2-slider mechanism was developed in Japan, and the joining time is less than 0.5 s, however the length of each bar are not reported and this mechanism is complex. A relatively simple 6-bar and 1-slider mechanism is put forward, which can realize the shearing and extrusion motion of the top and bottom blades with a speed approximately equal to the speed of the metal plates. In order to study the kinematics property of the double blades, based on complex vector method, the multi-rigid-body model is built, and the displacement and speed functions of the double blades, the joining time and joining thickness are deduced, the kinematics analysis shows that the initial parameters can't satisfy the joining process. Hence, optimization of this mechanism is employed using genetic algorithm(GA) and the optimization parameters of this mechanism are obtained, the kinematics analysis show that the joining time is less than 0.1 s, the joining thickness is more than 80% of the thickness of the solid-state metal, and the horizontal speeds of the blades are improved. A new mechanism is provided for the joining of the solid-state metal and a foundation is laid for the design of the device. 展开更多
关键词 endless rolling solid-state metal dynamical joining mechanism KINEMATIC optimization genetic algorithm
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Study of joining mechanism of ABS polymer and steel/aluminum by resistance spot welding 被引量:9
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作者 Zhang Changqing Lu Guangming +2 位作者 Jin Xin Wang Weijie Jin Shaolong 《China Welding》 EI CAS 2018年第2期57-62,共6页
The joining of metal and polymer is an increasingly important method to get lightweight components in the development of manufacturing industry- nowadays. In this artiele, metal and polymer lap joint was achieved by m... The joining of metal and polymer is an increasingly important method to get lightweight components in the development of manufacturing industry- nowadays. In this artiele, metal and polymer lap joint was achieved by means of resistance spot welding (RSW) and ultrasonic assistance welding (UAW). The joining mechanism of lap joint was analyzed by OM, TEM on microstructure at the interface of lap joints and XPS and IR spectra was discussed based on the following different ones: mechanical-interlocking, diffusion bond and coordination bond. The results showed that it was the combined action that played an important role in the effective joining work. Besides, ultrasonic assistance was used in the study to aid welding process based on its high-frequency ultrasonic vibration, which made joints shaping better and improved tensile strength visibly contrast to joints with the same lower heat input parameters. 展开更多
关键词 lap joints resistance spot welding joining mechanism ultrasonic assistance welding
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MICROWAVE JOINING OF ALUMINA CERAMIC AND HYDROXYLAPATITE BIOCERAMIC 被引量:4
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作者 Zhou, Jian Zhang, Qiaoxin +1 位作者 Mei, Bingchu Yan, Yuhua 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 1999年第2期46-49,共4页
Microwave joining is a rapid developmental new technique in recent years. This paper introduces a new microwave joining equipment which was made by our lab, succeeds in alumina ceramic - hydroxylapatite bioceramic jo... Microwave joining is a rapid developmental new technique in recent years. This paper introduces a new microwave joining equipment which was made by our lab, succeeds in alumina ceramic - hydroxylapatite bioceramic join in the equipment, and analyzes the join situation of join boundary by using scanning electron microscope (SEM), this paper analyzes the mechanism of microwave joining also. (Author abstract) 4 Refs. 展开更多
关键词 Al2O3 ceramic hydroxylapatite bioceramic microwave joining
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Climatological Characteristics of the Moisture Budget and Their Anomalies over the Joining Area of Asia and the Indian-Pacific Ocean 被引量:5
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作者 柳艳菊 丁一汇 +1 位作者 宋亚芳 张锦 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2009年第4期642-655,共14页
The climatological characteristics of the moisture budget over the joining area of Asia and the IndianPacific Ocean (AIPO) and its adjacent regions as well as their anomalies have been estimated in this study. The m... The climatological characteristics of the moisture budget over the joining area of Asia and the IndianPacific Ocean (AIPO) and its adjacent regions as well as their anomalies have been estimated in this study. The main results are as follows. In the winter, the northeasterly moisture transport covers the extensive areas at the lower latitudes of the AIPO. The westerly and northerly moisture transport is the major source and the South Indian Ocean (SIO) is the moisture sink. In the summer, influenced by the southwesterly monsoonal wind, the crossequatorial southwesterly moisture transport across Somali originating from the SIO is transported through the Arabian Sea (AS), the Bay of Bengal (BOB), and the South China Sea (SCS) to eastern China. The AIPO is controlled by the southwesterly moisture transport. The net moisture influx over the AIPO has obvious interannual and interdecadal variations. From the mid- or late 1970s, the influxes over the SIO, the AS, the northern part of the western North Pacific (NWNP), and North China (NC) as well as South China (SC) begin to decrease abruptly, while those over Northeast China (NEC) and the Yangtze River-Huaihe River basins (YHRB) have increased remarkably. As a whole, the net moisture influxes over the BOB and the southern part of the western North Pacific (SWNP) in the recent 50 years take on a linear increasing trend. However, the transition timing for these two regions is different with the former being at the mid- or late 1980s and the latter occurring earlier, approximately at the early stage of the 1970s. The anomalous moisture source associated with the precipitation anomalies is different from the normal conditions of the summer precipitation. For the drought or flood years or the years of E1 Nifio and its following years, the anomalous moisture transport originating from the western North Pacific (WNP) is the vital source of the anomalous precipitation over eastern China, which is greatly related with the variation of the subtropical Pacific high. 展开更多
关键词 the joining area of Asia and the Indian-Pacific Ocean moisture transport and budget climatological characteristics ANOMALIES
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A LEVEL SET METHOD FOR STRUCTURAL TOPOLOGY OPTIMIZATION WITH MULTI-CONSTRAINTS AND MULTI-MATERIALS 被引量:9
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作者 梅玉林 王晓明 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2004年第5期507-518,共12页
Combining the vector level set model,the shape sensitivity analysis theory with the gradient projection technique,a level set method for topology optimization with multi-constraints and multi-materials is presented in... Combining the vector level set model,the shape sensitivity analysis theory with the gradient projection technique,a level set method for topology optimization with multi-constraints and multi-materials is presented in this paper.The method implicitly describes structural material in- terfaces by the vector level set and achieves the optimal shape and topology through the continuous evolution of the material interfaces in the structure.In order to increase computational efficiency for a fast convergence,an appropriate nonlinear speed mapping is established in the tangential space of the active constraints.Meanwhile,in order to overcome the numerical instability of general topology opti- mization problems,the regularization with the mean curvature flow is utilized to maintain the interface smoothness during the optimization process.The numerical examples demonstrate that the approach possesses a good flexibility in handling topological changes and gives an interface representation in a high fidelity,compared with other methods based on explicit boundary variations in the literature. 展开更多
关键词 level set method topology optimization MULTI-CONSTRAINTS multi-materials mean curvature flow
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JOINING OF TiAl BASEDALLOYS BY HOT PRESSING 被引量:2
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作者 B. Y. Huang, Y. H. He, B. Wang and Y. Liu National Key Laboratory for Powder Metallurgy, Central South University of Technology, Changsha 410083, China 《中国有色金属学会会刊:英文版》 CSCD 1999年第S1期30-33,共4页
By hot pressing in an inert atmosphere, the joining interface between coarse lamellar structures and that between a coarse lamellar structure and a fine duplex structure of a Ti 33Al 3Cr(%, mass fraction) alloy, and t... By hot pressing in an inert atmosphere, the joining interface between coarse lamellar structures and that between a coarse lamellar structure and a fine duplex structure of a Ti 33Al 3Cr(%, mass fraction) alloy, and the effect of heat treatment on the microstructure at the interfaces have been studied. The results showed that the microstructure at the interface between two coarse lamellar structures depends on the orientations of lamellae. And microcavities are found at such interfaces. After heat treatment at 1 250 ℃, the recrystallization structure widened. As to the interface between a coarse lamellar structure and a fine duplex structure, a new duplex structure formed within the original duplex structure at the interface and further widened after subsequent heat treatment at 1 250 ℃ for 4 h. Microcavities are rare at such interfaces, and the joining appears better than that between two coarse lamellar structures. 展开更多
关键词 TIAL BASED ALLOY HOT PRESSING joining
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Green State Joining of ZrO_2(8YSZ)-Al_2O_3 Ceramics Using Slurry Containing PLS Nanocomposites 被引量:2
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作者 魏艳秋 刘家臣 +1 位作者 彭珍珍 赵玉红 《Journal of Rare Earths》 SCIE EI CAS CSCD 2003年第S1期102-104,共3页
Joining of ZrO_2 (containing 8% (mol fraction) Y_2O_3,as the composition used in oxygen sensors) to 95Al_2O_3 (widely used at elevated temperature) in green state was described using polymer/layered silicate (PLS) nan... Joining of ZrO_2 (containing 8% (mol fraction) Y_2O_3,as the composition used in oxygen sensors) to 95Al_2O_3 (widely used at elevated temperature) in green state was described using polymer/layered silicate (PLS) nanocomposites contained slurry,without applied pressure. Microstructure of the joined section was investigated. The effects of interlayer and PLS on joining qualities were analysed. The results show that interface cracks are easily produced because of mismatch of both thermal expansion and/or sintering shrinkage between joined samples. With an optimized condition of joining layer composition and solid contents,a fine joint could be obtained without obvious cracks,pores and other defects. This process is suitable for joining of various kinds of advanced ceramics. 展开更多
关键词 green state joining PLS nanocomposites advanced ceramic interface rare earths
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Thermal fatigue behaviors of SiC power module by Ag sinter joining under harsh thermal shock test 被引量:4
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作者 Chen Chuantong Zhang Hao +2 位作者 Jiu Jinting Long Xu Suganuma Katsuaki 《China Welding》 CAS 2022年第1期15-21,共7页
The excellent properties of SiC bring new challenges for the device packaging.In this study,the bonding strength,fracture behaviors and microstructural evolution of micron-porous Ag joint were elevated during thermal ... The excellent properties of SiC bring new challenges for the device packaging.In this study,the bonding strength,fracture behaviors and microstructural evolution of micron-porous Ag joint were elevated during thermal cycling(–50 ℃–250 ℃) in SiC/DBC(direct bonding copper) die attachment structure for different time.During harsh thermal shock test,the strength of sintered joint deceased gradually with the increase of cycling number,and the value just was half of the value of as-sintered after 1 000 cycles.Coarsening of Ag grains was observed in micron-porous joint with the structure inhomogeneity and defects increasing,which were the reasons of the strength decease.In addition,it was also found that the fracture behavior of sintered joints was changed from ductile deformation of Ag grain to brittle fracture of crack propagation after 1 000 cycles.This study will add the understanding in the mechanical properties of Ag sinter joining and its applications at high temperature. 展开更多
关键词 power module high-temperature reliability Ag sinter joining low stress structure thermal shock test
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