Effect of the Boundary Orientation of Melt Pool on Mechanical Property and Fracture Path in Selective-Laser-Melted AlSi10Mg Alloy

Zihao Jiang,Yayun Li,Hang Luo,Baogang Zhou,Yilong Liang,Yu Liang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.12

The present work investigated the effect of the boundary orientation of melt pool on the mechanical properties and fracturepath in selective-laser-melted AlSi10Mg alloy. The acquired data are beneficial for understanding the influence of themicrostructure on mechanical properties. During the alloy’s selective laser melting (SLM), the melt pool boundary wasalmost parallel with the scanning direction, and the grains grew along the building direction. When the load-bearing facewas perpendicular to the melt pool boundary, the crack propagation path deflected towards coarse melt pool of the melt poolboundary, reducing the probability of directly crossing the fine melt pool. Otherwise, the cracks would mainly propagatealong the melt pool boundary. In the tensile deformation process, coarse melt pool (CMP) was subjected to higher localstrain than fine melt pool (FMP) and heat-affected zone (HAZ), and the crack propagated or deflected along the CMP inthe melt pool boundary. Therefore, the anisotropy of mechanical properties in SLM AlSi10Mg was mainly ascribed to theCMP density on the load-bearing face. As a weak area, the high proportion of CMP significantly reduced the strength andplasticity of the alloy.

Theoretical and practical models for shear strength of corroded reinforced concrete columns

Bo Yu,Zihao Ding,Shengbin Liu,Bing Li 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.5

In order to predict the shear strength of corroded reinforced concrete column (CRCC) accurately and efficiently, both theoretical and practical models for shear strength of the CRCC were established through theoretical derivation and experimental validation. The deterioration mechanism for shear strength of the CRCC due to the steel reinforcement corrosion was explored first based on the shear mechanism analysis of the truss-arch model. Then a theoretical model for shear strength of the CRCC was developed by taking into account the influences of steel reinforcement corrosion on the effective yield strength of transverse reinforcement, the effective cross-sectional area of both corroded transverse and longitudinal reinforcements as well as the effective concrete shear area. Meanwhile, three practical models to evaluate the shear strength of the CRCC were proposed based on 54 sets of experimental data by determining the approximate values of three important parameters, including the contribution coefficient of shear strength for concrete, the ratio of shear stiffness between the truss model and the arch model, as well as the tangent value of the critical crack angle. Finally, the accuracy and applicability of both theoretical and practical models for shear strength of the CRCC were validated by comparing with five existing empirical shear strength models.

Theoretical modelling and simulation analysis of the thermal performance of a steel-basalt fiber polymer concrete machine tool joint surface

Jiaxing Shen,Zihao Pan,Ping Xu,Yinghua Yu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.7

The thermal performance of a steel-basalt fiber polymer concrete machine tool joint surface has a key influence on a machine tool. Based on virtual material theory, the equivalent thermal model was established and the thermal performance parameters of virtual materials were deduced by theoretical calculation. The calculation method of actual contact area ratio of steel - basalt fiber polymer concrete joint surface was established based on discrete principle and its accuracy was verified. To determine the influence of preload pressure on the actual contact area ratio, a prediction model was established. The thermal conductivity of the material was measured by the quasi-steady state method. A new systematic simulation analysis method that synthesizes virtual material theory and finite element simulation analysis was proposed, and its accuracy was verified. The results show that the relative error is only 5.01 %, which proves the method’s effectiveness.

Flexible multimode pressure sensor based on liquid metal

Xiao-Ping Zhou,Zihao Yu 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.6

In this paper, a novel multimode liquid metal-based pressure sensor is developed. The main body of the sensor is composed of polydimethylsiloxane (PDMS) elastomer. The structure of the sensor looks like a sandwich, in which the upper structure contains a cylindrical cavity, and the bottom structure contains a spiral microchannel, and the middle partition layer separates the upper and the bottom structures. Then, the liquid metal is injected into the top cavity and the bottom microchannel. Based on linear elastic fracture mechanics, the deformation of the microchannel cross-section is theoretically analyzed. The changes of resistance, capacitance, and inductance of the microchannel under pressure are deduced, and the corresponding theoretical models are established. The theoretical values of the pressure sensor are in good agreement with experimental data, implying that the developed theoretical model can explain the performance of the sensor well.

A new reconfigurable liquid-metal-antenna-based sensor

Xiao-Ping Zhou,Yihui Fu,Hantao Zhu,Zihao Yu,Shanyong Wang 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.30 No.4

In this paper, a new sensor chip with frequency reconstruction range of 2.252 GHz ~ 2.450 GHz is designed and fabricated. On this basis, a self-designed "T-shaped" shell is added to overcome the disadvantage of uneven deformation of the traditional steel shell, and the range of the sensor chip is expanded to 0 kN ~ 96 kN. The liquid metal antenna is used to carry out a step-by-step loading test, and the relationship between the antenna resonance frequency and the pressure load is analyzed. The results show that there is a good linear relationship between the pressure load and the resonant frequency. Therefore, the liquid metal antenna can be regarded as a pressure sensor. The cyclic loading and unloading experiments of the sensor are carried out, and different loading rates are used to explore the influence on the performance of the sensor. The loading and unloading characteristic curves and the influence characteristic curves of loading rate are plotted. The experimental results show that the sensor has no residual deformation during the cycle of loading and unloading. Moreover, the influence of temperature on the performance of the sensor is studied, and the temperature correction formula is derived.

Numerical investigation of the critical heat fl ux in a 5 × 5 rod bundle with multi-grid

Wei Liu,Zemin Shang,Shihao Yang,Lixin Yang,Zihao Tian,Yu Liu,Xi Chen,Qian Peng 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.5

To improve the heat transfer efficiency of the reactor fuel assembly, it is necessary to accurately calculatethe two-phase flow boiling characteristics and the critical heat flux (CHF) in the fuel assembly. In thispaper, a Eulerian two-fluid model combined with the extended wall boiling model was used tonumerically simulate the 5 5 fuel rod bundle with spacer grids (four sets of mixing vane grids and foursets of simple support grids without mixing vanes). We calculated and analyzed 11 experimental conditions under different pressure, inlet temperature, and mass flux. After comparing the CHF and thelocation of departure from the nucleate boiling obtained by the numerical simulation with the experimental results, we confirmed the reliability of computational fluid dynamic analysis for the prediction ofthe CHF of the rod bundle and the boiling characteristics of the two-phase flow. Subsequently, weanalyzed the influence of the spacer grid and mixing vanes on the void fraction, liquid temperature, andsecondary flow distribution. The research in this article provides theoretical support for the design of fuelassemblies