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Microstructure refinement and improvement of mechanical properties of Ti46Al8Nb0.9B alloys by electromagnetic cold crucible continuous solidification

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INTERMETALLICS 2022年 140卷 107391-107391页

作者： Wang, Yongzhe Li, Wei Yuan, Hong Ding, Hongsheng Chen, Ruirun Guo, Jingjie Fu, Hengzhi Jinan Univ Inst Adv Wear & Corros Resistance & Funct Mat Guangzhou 510632 Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Harbin Inst Technol Sch Mat Sci & Engn Harbin 150001 Peoples R China

Microalloying with boron is effective and economical for refining microstructures of as-cast TiAl alloy. However, microstructural refinement is easily affected by the alloy composition and cooling rate, leading to inhomogeneous grain size in different areas of the ingot. In this study, the Ti46Al8Nb0.9B alloys are continuously solidified by the electromagnetic cold crucible, aiming to obtain homogeneous and fine microstructure. After electromagnetic cold crucible continuous solidification (EMCS), the obtained ingot shows finer and more homogeneous microstructure with lamellar colony size of about 50 mu m. The results of tensile test show that the EMCS ingot exhibited improved properties with yield strength (00.2) of 548 MPa and plastic elongation of 0.6%.

关键词： TiAl alloy Microstructure refinement Solidification Mechanical properties

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Wave Soldering Coupled Thermal-mechanical Simulation of Multi-layer Ceramic Capacitors

Wave Soldering Coupled Thermal-mechanical Simulation of Mult...

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Asia Conference on Geological Research and Environmental Technology (GRET)

作者： Su, Wei Luo, Wenhao Li, Junkui Liu, Renhuai MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China China Elect Prod Reliabil & Environm Testing Res Sci & Technol Reliabil Phys & Applicat Technol El Guangzhou 510610 Peoples R China Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China

In this paper, the thermal-mechanical coupling finite element analysis of MLCC wave soldering with heat conduction and heat convection is calculated, and the steady-state temperature field and transient temperature field as well as the stress distribution of MLCC are obtained. Using the finite element analysis method of indirect thermal-mechanical coupling, the stress analysis is carried out with the temperature field as the boundary condition, and the thermal-structural coupling model is established. By analyzing the thermal stress of MLCC, the weak parts sensitive to thermal stress are determined, which provides a useful reference for solving the reliability problem of MLCC wave soldering.

关键词： Wave Soldering Thermal-mechanical Coupling Thermal Stress Weak Parts

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Experimental study on damping characteristics of elevator traction system

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ADVANCES IN MECHANICAL engineering 2022年第3期14卷

作者： Xu, Peng Peng, Qifeng Jin, Fusong Xia, Fei Xue, Jianghong Yuan, Hong Li, Shanqing Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn 601 Huang Pu Da Dao Guangzhou 51063 Peoples R China China Univ Petr Huadong Coll Pipeline & Civil Engn Qingdao Peoples R China

An elevator traction system is simplified as a damped vibration system. In order to study the damping characteristics of an elevator traction system, this paper tests the vibration characteristics of a car frame on an in-service elevator with a traction ratio of 2:1. The results show that the natural frequency and stiffness of the system decrease with the increase of the elevator load;the attenuation coefficient and damping increase with the increase of the elevator load;Furthermore, the damping of the traction system is related to the initial running direction. Under the same load, the damping value of downward is greater than that of upward. This research establishes the relationship between vibration parameters, load and elevator running direction and provides an approach to solve the problem of quantitative measurement of damping in the process of elevator operation. Results from this study can provide reference for elevator vibration analysis.

关键词： Elevator car frame free vibration damping attenuation coefficient test method

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Method of analyzing coating structure under conical concave contact

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MEASUREMENT 2023年 206卷

作者： Huang, Shi-Qing Tang, Pan-Jun Hou, Peng-Fei Zhang, Wen-Hua Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Chinese Acad Sci GBA Branch Aerosp Informat Res Inst Guangzhou 510700 Peoples R China Hunan Univ State Key Lab Adv Design & Mfg Vehicle Body Changsha 410082 Peoples R China Hunan Univ Dept Engn Mech Changsha 410082 Peoples R China

The evaluation of mechanical performance for a coating structure is important in the fields of mechanics and materials. The exact solutions of the contact mechanics for transversely isotropic elasticity coating structures under conical concave contact are presented in this paper. Based on the Green's function of semi-infinite bodies, the Green's function of coating structure is obtained with mirror image method. The exact solutions obtained indicates the displacement and stress at any position of the coating, substrate, and interface, which provide the code basis for the analysis of interface failure and determination of material parameters in numerical analysis software. This paper presents exact solutions in the elastic stage, and there are stress singularities in the contact center and contact boundary, which provide a reference for future research on the relationships between stress singularities and plastic mechanical behavior.

关键词： Exact solution Contact mechanics Coating structure Conical concave Finite element method

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Double-Level Energy Absorption of 3D Printed TPMS Cellular Structures via Wall Thickness Gradient Design

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MATERIALS 2021年第21期14卷 6262-6262页

作者： Zhong, Minting Zhou, Wei Xi, Huifeng Liang, Yingjing Wu, Zhigang Guangzhou Univ Sch Civil Engn Guangzhou 510006 Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

This paper investigates the deformation mechanism and energy absorption behaviour of 316 L triply periodic minimal surface (TPMS) structures with uniform and graded wall thicknesses fabricated by the selective laser melting technique. The uniform P-surface TPMS structure presents a single-level stress plateau for energy absorption and a localized diagonal shear cell failure. A graded strategy was employed to break such localized geometrical deformation to improve the overall energy absorption and to provide a double-level function. Two segments with different wall thicknesses separated by a barrier layer were designed along the compression direction while keeping the same relative density as the uniform structure. The results show that the crushing of the cells of the graded P-surface TPMS structure occurs first within the thin segment and then propagates to the thick segment. The stress-strain response shows apparent double stress plateaus. The stress level and length of each plateau can be adjusted by changing the wall thickness and position of the barrier layer between the two segments. The total energy absorption of the gradient TPMS structure was also found slightly higher than that of the uniform TPMS counterparts. The gradient design of TPMS structures may find applications where the energy absorption requires a double-level feature or a warning function.

关键词： triply periodic minimal surface selective laser melting 316 L stainless steel energy absorption deformation mechanism

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Deformable micro-continua in which quantum mysteries reside

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Applied Mathematics and Mechanics(English Edition) 2019年第12期40卷 1805-1830页

作者： Heng XIAO Shanghai Institute of Applied Mathematics & Mechanics College of Mechanics and Engineering Science Shanghai University College of Mechanics and Construction Engineering MOE Lab of Disaster Forecast and Control in Engineering Jinan University

Deformable micro-continua of highly localized nature are found to exactly exhibit all quantum effects commonly known for quantum entities at microscopic *** every instant,the spatial configuration of each such micro-continuum is prescribed by four spatial distributions of the mass,the velocity,the internal stress,and the intrinsic angular *** deformability features of such micro-continua in response to all configuration changes are identified with a constitutive equation that specifies how the internal stress responds to the mass density *** is shown that these microcontinua are endowed with the following unique response features:(i)the coupled system of the nonlinear field equations governing their dynamic responses to any given force and torque fields is exactly reducible to a linear dynamic equation governing a complex field variable;(ii)this fundamental dynamic equation and this complex field variable are just the Schrodinger equation and the complex wave function in quantum theory;and,accordingly,(iii)the latter two and all quantum effects known for quantum entities are in a natural and unified manner incorporated as the inherent response features of the micro-continua discovered,thus following objective and deterministic response patterns for quantum entities,in which the physical origins and meanings of the wave function and the Schrodinger equation become self-evident and,in particular,any probabilistic indeterminacy becomes irrelevant.

关键词： quantum entity micro-continuum Hencky strain-energy density nonlinear dynamic equation exact linearization Schrodinger equation deterministic pattern

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In-plane elasticity of the re-entrant auxetic hexagonal honeycomb with hollow-circle joint

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AEROSPACE SCIENCE AND TECHNOLOGY 2022年第0期123卷 107432-107432页

作者： Chen, Yu Wang, Zhi-Wei Jinan Univ Packaging Engn Inst Coll Packaging Engn Zhuhai 519070 Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Jinan Univ Key Lab Prod Packaging & Logist Guangdong Higher Zhuhai 519070 Peoples R China Jinan Univ Zhuhai Key Lab Prod Packaging & Logist Zhuhai 519070 Peoples R China

This work proposed an improved modification on the common re-entrant hexagonal honeycomb (RHH) by replacing the solid junction of the cell walls with a small hollow circle, and thus achieving a novel kind of honeycomb. A simple energy-based approach was adopted to develop theoretical models for predicting the in-plane equivalent elastic moduli of the new honeycomb. Finite element analysis was employed to verify the theoretical models and then the effects of the micro geometrical parameters on the in plane elastic behaviors were further discussed. The results showed that the new honeycomb possesses an obvious negative Poisson's ratio effect, meanwhile, can achieve higher specific Young's modulus and shear modulus than the RHH. Moreover, the new honeycomb was found to exhibit a more tailored anisotropy than the RHH from the off-axial properties analysis. As a result, the new honeycomb may be an effective substitute for the RHH in application and the new layout can be a good guide for the improved design of auxetic honeycombs. (c) 2022 Elsevier Masson SAS. All rights reserved.

关键词： negative Poisson's ratio Re-entrant hexagonal honeycomb (RHH) Hollow-circle joint In-plane Equivalent elastic moduli

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A magnetic Bi-stable nonlinear energy sink for structural seismic control

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JOURNAL OF SOUND AND VIBRATION 2020年第0期473卷 115233-000页

作者： Chen, Yang-Yang Qian, Zhi-Chao Zhao, Wei Chang, Chia-Ming Guangzhou Univ Earthquake Engn Res & Test Ctr MOE Key Lab Earthquake Resistance Earthquake Miti Guangzhou 510405 Peoples R China Guangzhou Univ Guangdong Prov Key Lab Earthquake Engn & Appl Tec Guangzhou 510405 Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Taiwan Natl Univ Dept Civil Engn Taipei 10617 Taiwan

In this paper, a magnetic bi-stable NES (MNES) is proposed for structural seismic control. Permanent magnets are configured to generate noncontact and smooth bi-stable restoring force for the present MNES device, by which the transient internal resonance between the primary structure and the attached MNES can be rapidly enhanced under seismic excitation. The governing equation of the present MNES is derived, and the numerical parameter optimization is carried out for its implementation in seismic control for a shear frame model. Seismic performance of this frame structure attached with the proposed MNES is evaluated, and compared to those of cubic NES and linear tuned mass damper (TMD) systems. As shown in the results, the proposed MNES is found to be robustly capable of protecting the shear frame under seismic excitations. Immediate cascade of broadband transient internal resonance captures under seismic excitations are found as the essential cause of the high efficiency of the present MNES system. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Nonlinear energy sink Magnetic force Transient internal resonance Targeted energy transfer Seismic control

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Powder bed fusion manufacturing of beta-type titanium alloys for biomedical implant applications: A review

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JOURNAL OF ALLOYS AND COMPOUNDS 2023年 936卷

作者： Zhang, Lai-Chang Chen, Liang-Yu Zhou, Shengfeng Luo, Zhen Edith Cowan Univ Sch Engn 270 Joondalup Dr Perth WA 6027 Australia Jiangsu Univ Sci & Technol Sch Mat Sci & Technol Zhenjiang 212003 Jiangsu Peoples R China Jinan Univ Inst Adv Wear & Corros Resistant & Funct Mat MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China Univ Technol Sydney Sch Mech & Mechatron Engn Ultimo NSW 2007 Australia

Thanks to many fascinating properties, such as high mechanical properties, good corrosion resistance, and excellent biocompatibility, beta-type Ti alloys are frequently employed as biomedical implants. In recent decades, rapidly developed powder bed fusion (PBF) technologies have become new methods for fabricating beta-type Ti alloys. This article reviews the recent advances and insightful perspectives on the feedstock powder characteristics (e.g., pre-alloyed powder and elemental powder mixtures), microstructure, me-chanical properties, and corrosion behavior of PBF-produced beta-type Ti alloys in the forms of bulk solid parts and lattice structures. As reviewed, PBF-produced bulk beta-type Ti alloys exhibit higher strength than their conventional counterparts, accompanying with slight decrease in the maximum deformation strain. The corrosion behavior of PBF-produced bulk beta-type Ti alloys with the identical corresponding chemical compositions is related to their phase constituents in microstructure, which results from the fabrication methods or processing procedures. Additionally, PBF-produced bulk beta-type Ti alloys still have higher elastic moduli than the human bones. Hence, with the assistance of PBF technologies, lattice structures of beta-type Ti alloys with lower and controllable moduli are developed to obtain reduced their elastic moduli. For biomedical implant applications, PBF-produced lattice structures of beta-type Ti alloys with multi-functional coatings may become promising materials in the future. Nevertheless, the investigations on the PBF-produced beta-type Ti alloys for biomedical implant applications are hitherto still in the initial stage. (c) 2022 Elsevier B.V. All rights reserved.

关键词： Powder bed fusion Additive manufacturing Beta-type Ti alloy Biomedical materials Properties

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Interfacial shear stress analysis in single-lap adhesive joints with similar and dissimilar adherends under dynamic loading

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INTERNATIONAL JOURNAL OF ADHESION AND ADHESIVES 2021年 111卷 102953-102953页

作者： Ma, Guoliang Wu, Jiayu Yuan, Hong Jinan Univ Inst Appl Mech MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Southern Univ Sci & Technol Dept Ocean Sci & Engn Shenzhen 518055 Peoples R China

Single-lap joints (SLJs) with similar and dissimilar adherends are extensively used in industrial applications. This paper aims to investigate the interfacial mechanical behavior of SLJs subjected to dynamic loading. The shear-lag model is employed to predict the mechanical behavior of SLJs. The analytical expressions of the interfacial slip, normal stress in the adherends and interfacial shear stress are derived for the SLJs with similar adherends by using the method of separation of variables. The Laplace transform method is applied to numerically simulate the dynamic response of SLJs with dissimilar adherends. Results obtained from the finite element simulation are consistent well with the predictive model. It is found that the more unbalanced the SLJ is, the more non-uniform distribution of interfacial stress is, thus reducing the load-bearing capacity of the SLJ. This inspires us to rationally design a balanced joint to improve the load-bearing capacity. While the emphasis of the present study is on the mechanical behavior of SLJs, the analytical model is equally applicable to the interface analysis of other structures (e.g. concrete-steel bar, fiber-matrix in the composites, etc.). Furthermore, this theoretical method can be also simplified to explain the stress transfer subjected to the (quasi-)static loading with approximately zero density or zero loading speed in the governing equation.

关键词： Adhesively bonded joint Single-lap joint (SLJ) Shear-lag model Dynamic response Stress transfer

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