Optimal design of micro-nano displacement driving mechanism for obtaining mechanical properties of micro structure

Biao Wang,Yan Huang,Yonghong Wang,Peizheng Yan,Qiaosheng Pan 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

The mechanical structures of micro-electro-mechanical systems (MEMS) are composed of different types of microstructures, and their mechanical properties are very important for the realisation and reliability of the system performance. One of the key problems in measuring the mechanical properties is the design and implementation of micro-nano displacement driving mechanisms. This paper describes a mechanism that adopts a two-level loading strategy, fast approach, and precise bending displacement loading structures, and has a theoretical analysis and optimal design based on optimal targets of resistance and displacement. The results show that the relative error is 6.98 % for the fast-approaching structure experiment and its optimal simulation and 4.26 % for the precise bending displacement loading structure (PBLS) experiment and its optimal simulation. The optimised micro-nano displacement loading mechanism can achieve optimal output performance under existing constraints.

Axial load behavior and stability strength of circular tubed steel reinforced concrete (SRC) columns

Biao Yan,Jiepeng Liu,Xuhong Zhou 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.25 No.5

The tubed steel reinforced concrete (SRC) column is a composite column in which the outer steel tube is mainly used to provide confinement on the core concrete. This paper presents experimental and analytical studies on the behavior of circular tubed SRC (TSRC) columns subjected to axial compression. Eight circular TSRC columns were tested to investigate the effects of length-to-diameter ratio (L/D) of the specimens, diameter-to-thickness ratio (D/t) of the steel tubes, and use of stud shear connectors on the steel sections. Elastic-plastic analysis on the steel tubes was used to investigate the mechanism of confinement on the core concrete. The test results indicated that the tube confinement increased the strength and deformation capacity for both short and slender columns, and the effects on strength were more pronounced for short columns. A nonlinear finite element (FE) model was developed using ABAQUS, in which the nonlinear material behavior and initial geometric imperfection were included. Good agreement was achieved between the predicted results using the FE model and the test results. The test and FE results were compared with the predicted strengths calculated by Eurocode 4 and the AISC Standard. Based on the analytical results, a new design method for this composite column was proposed.

Influence of slenderness on axially loaded square tubed steel-reinforced concrete columns

Biao Yan,Dan Gan,Xuhong Zhou,Weiqing Zhu 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.3

This paper aims to investigate the axial load behavior and stability strength of square tubed steel-reinforced concrete (TSRC) columns. Unlike concrete filled steel tubular (CFST) column, the outer steel tube of a TSRC column is mainly used to provide confinement to the core concrete. Ten specimens were tested under axial compression, and the main test variables included length-to-width ratio (<i>L/B</i>) of the specimens, width-to-thickness ratio (<i>B/t</i>) of the steel tubes, and with or without stud shear connectors on the steel sections. The failure mode, ultimate strength and load-tube stress response of each specimen were summarized and analyzed. The test results indicated that the axial load carried by square tube due to friction and bond of the interface increased with the increase of <i>L/B</i> ratio, while the confinement effect of tube was just the opposite. Parametric studies were performed through ABAQUS based on the test results, and the feasibility of current design codes has also been examined. Finally, a method for calculating the ultimate strength of this composite column was proposed, in which the slenderness effect on the tube confinement was considered.

Adaptive Approaches to Identify the Interface in Low Frequency Vibration-Assisted Drilling of CFRP/Ti6Al4V Stacks

Chaoren Yan,Yan Chen,Ning Qian,Nan Guo,Yongqing Wang,Haojun Yang,Biao Zhao 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.8

Low frequency vibration-assisted drilling (LFVAD) of CFRP/Ti stacks is a promising method of one-shot drilling to increase efficiency and extend tool life while adaptive approaches are applied to adjust the cutting parameters in each layer. Thus, the interfacial recognition method is significant to automatically change the cutting parameters. In this paper, two recognition methods are proposed based on the analysis of the features of cutting forces under the LFVAD process in both time and frequency domains. With the recorded thrust force signals at different wear stages, both the proposed methods identify the transition point when the drill bit starts to contact the Ti layer within allowable time delay. Compared with the traditional threshold method, the time domain method and the frequency domain method respectively increase the identifying speed by 19.8% and 46.7%, besides the reduction of implementation cost. In contrast, the time domain method reduces the programming and calculation time, while the frequency domain method improves the average recognition speed. Furthermore, an adaptive drilling system embedded with the established time-domain method is designed and the accuracy of the method is proved of 100% in a drilling test of all 20 CFRP/Ti stack holes. Moreover, the effect of the adaptive LFVAD process in improving tool wear and increasing machining efficiency is verified by reducing the force growth rate by 11.7% and time decrease of 37% in a hole-making cycle compared with the traditional LFVAD process.

Behaviors of UHPC-filled Q960 high strength steel tubes under lowtemperature compression

Jia-Bao Yan,Shunnian Hu,Yan-Li Luo,Xuchuan Lin,Yun-Biao Luo,Lingxin Zhang 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.2

This paper firstly proposed high performance composite columns for cold-region infrastructures using ultra-high performance concrete (UHPC) and ultra-high strength steel (UHSS) Q960E. Then, 24 square UHPC-filled UHSS tubes (UHSTCs) at low temperatures of -80, -60, -30, and 30℃ were performed under axial loads. The key influencing parameters on axial compression performance of UHSS were studied, i.e., temperature level and UHSS-tube wall thickness (t). In addition, mechanical properties of Q960E at low temperatures were also studied. Test results revealed low temperatures improved the yield/ultimate strength of Q960E. Axial compression tests on UHSTCs revealed that the dropping environmental temperature increased the compression strength and stiffness, but compromised the ductility of UHSTCs; increasing t significantly increased the strength, stiffness, and ductility of UHSTCs. This study developed numerical and theoretical models to reproduce axial compression performances of UHSTCs at low temperatures. Validations against 24 tests proved that both two methods provided reasonable simulations on axial compression performance of UHSTCs. Finally, simplified theoretical models (STMs) and modified prediction equations in AISC 360, ACI 318, and Eurocode 4 were developed to estimate the axial load capacity of UHSTCs at low temperatures.

3D quasi-transient thermo-mechanical analysis for vehicle brake disc

Biao Hu,Xingyan Zhang,Yang Liu,Junjie Yan,Xiaobing Liu,Xin Wang,Richard Sun 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2

An alternative numerical method is developed to predict the thermo-mechanical behavior of brake disc during braking. Steady-state aerodynamic simulation for entire vehicle with variant speeds are conducted to analyze the convective heat transfer characteristic of the disc surface. Then the transient heat transfer boundary of the disc is obtained by interpolating the steady-state simulation results. Based on that, the transient thermo-mechanical coupled simulation for brake disc is performed via finite element method. With those work, the characteristics of transient temperature field and stress field of the brake disc are analyzed. Meanwhile, the characteristic of contact pressure distribution on friction interface is also obtained. The results show that during the braking process, for any node in the friction areas of the brake disc surface, its temperature rise curve fluctuates like a sawtooth. The temperature field has a significant effect on the stress field of the brake disc, both in distribution and variation. To verify the numerical method and validate the simulation results, a full-scale vehicle brake-thermalperformance test is carried out. By comparison, the simulation results show good agreement with the experimental results. The proposed numerical method enables an efficient and economical way to predict and evaluate the thermo-mechanical behavior of the brake disc in early phase of vehicle development.

WEIGHTED EVIDENTIAL FUSION METHOD FOR FAULT DIAGNOSIS OF MECHANICAL TRANSMISSION BASED ON OIL ANALYSIS DATA

Yan Shu-fa,Ma Biao,Zheng Chang-song,Chen Man 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.5

Condition monitoring (CM) and fault diagnosis are critical for the stable and reliable operation of mechanical transmissions. Mechanical transmission wear, which leads to changes in the physicochemical properties of the lubrication oil and thus severe wear, is a slow degradation process that can be monitored by oil analysis, but the actual degradation degree is difficult to evaluate. To solve this problem, we propose a new weighted evidential data fusion method to better characterize the degradation degree of the mechanical transmission through the fusion of multiple CM datasets from oil analysis. This method includes weight allocation and data fusion steps that lead to a more accurate data-based fault diagnostic result for CM. First, the weight of each evidence is modeled with a weighted average function by measuring the relative scale of the permutation entropy from each CM dataset. Then, the multiple CM datasets are fused by the Dempster combination rule. Compared with other evidential data fusion methods, the proposed method using the new weight allocation function seems more reasonable. The rationality and superiority of the proposed method were evaluated through a case study involving an oilbased CM dataset from a power-shift steering transmission.

Active Earth Pressure of Narrow Backfill against Inverted T-Type Retaining Walls Rotating about the Heel

Yan-Bin Zhang,Fu-Quan Chen,Yu-Jian Lin,Hao-Biao Chen 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.4

Inverted T-type retaining walls are commonly used in subgrade or slope support engineering, which inevitably satisfies a narrow backfill. Using the classical earth pressure calculation method in a narrow-backfill case causes an inevitable error. The current narrow-backfill earth pressure theory does not apply to inverted T-type retaining walls. In this study, the failure mechanism in a narrow backfill when the inverted T-type retaining wall rotates about the heel is investigated using adaptive finite element analysis method. Numerical analysis reveals multiple sliding surfaces. A theoretical model for calculating earth pressure using difference and limit equilibrium methods is proposed. The proposed model is suitable for more complex conditions, including narrow backfill, irregular ground, and non-uniform overload, than previous models. Parameter analysis reveals that the cross-sectional area of the plastic zone and active earth pressure have a positive correlation. Further, the interface friction influences the decrease in active earth pressure. Fitting formulas for assessing the cases of long and short heel and the critical size of backfill width are presented to facilitate practitioners to evaluate the backfill.

Facile Synthesis of Ag/AgCl Grafted AgBi(MoO4)2 with Enhanced Photocatalytic Performance Under Visible Light

Xu Yan,Ziyang Wu,Yong Zhao,Biao Liu,Yong Zhao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.08

Silver nanoparticles (NPs) and related semiconductors are a family of very important and widely applied photocatalysts. However, the preparation of high stability and activity of this photocatalyst is still a challenge. In this work, we report a stable Ag/AgCl/AgBi(MoO4)2 heterojunction photocatalyst fabricated via a simple in situ anion-exchange reaction followed by the photoreduction treatment. In the treatment of tetracycline (TC) wastewater under visible light, the AC-0.4 sample (prepared with 0.4 mmol KCl) exhibits the significantly improved activity (degradation ratio, DR of 71.3%) compared with the pristine AgBi(MoO4)2 (30% DR) and Ag/AgCl sample (synthesized by the photoreduction of AgCl) (37% DR) under identical experimental conditions. This activity promotion is from the fast interfacial electron transfer between the heterojunction phases of AgCl/AgBi(MoO4)2 and the SPR effect of Ag NPs. After five successive recycles, the AC-0.4 sample still maintains good stability and activity for TC degradation, which shows a great potential to be used in practical application. Through the ESR and controlled scavenged experiments, we found the · OH and · O- 2 are the major reactive intermediate species in the TC photodegradation reaction. Our work provides a new insight into the synthesis of stable and high efficient Ag-based heterojunction photocatalysts for the application of wastewater treatment.

Restrained Shrinkage Mechanism of Ultra High Performance Concrete

Jun-Yan Wang,Chen Bian,Ru-Cheng Xiao,Biao Ma 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.10

The understanding and controlling of the restrained shrinkage is critical for the application of ultra high performance concrete(UHPC). This study made an analysis of restrained shrinkage mechanism of four kinds of UHPCs based on the direct tensile test accompanied with acoustic emission (AE) source location, free shrinkage test and restrained shrinkage test. The effects of UHPC tensile properties (strain softening or strain hardening) and high performance calcium sulphoaluminate (HCSA, a new kind of expansion agent) dosages (0%, 3% and 6% by mass of total binder) were investigated. The restrained shrinkage cracking mechanism of strain hardening UHPC and strain softening UHPC was analyzed based on AE analysis method under direct tensile loading. The results indicates that strain hardening UHPC shows multiple micro-defects to relax the restrained tensile stress marginally while strain softening UHPC shows several hairline cracks to relax the restrained tensile stress evidently. In ASTM C1581-04 ring test, the restrained shrinkage of strain hardening UHPC with HCSA dosage of 0%, 3% and 6% at 80d is 141 με, 96 με and 16 με, respectively. The HCSA expansion agent can effectively reduce the restrained shrinkage of UHPC and the influence on the structure.