Dynamic analysis of floating offshore wind turbine with SPAR and TLP platforms

Xiangqian Zhu,Kun-Woo Kim,Jeong-Hyun Sohn,Wan-suk Yoo 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.4

Dynamic Analysis of a Cable Considering the Impact of Seabed

Xiangqian Zhu,Min Hyung Cho,Wan Suk Yoo 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

The lumped-mass modelling is adopted in this paper for the dynamic analysis of a mooring cable. Since the condition of the seabed affects the motion of cable, the impact of seabed is divided into vertical and horizontal components in this paper. The seabed is simplified as plane and treated as spring modelling in vertical direction; meanwhile, the friction is applied on the cable resting on seabed in horizontal direction. Considering the environments, this paper also includes the tension and damping of cable, the hydrodynamic drag forces and the effect of added-mass during building the formulation of cable modelling. Finally, this numerical modelling is verified with commercial simulation code ProteusDS.

Singularities of the Frenet Frame during Dynamic Analyzing Mooring Cables Based on Lumped Mass Modeling

Xiangqian Zhu,Wan-Suk Yoo 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.춘계 No.-

Lumped mass modeling of cable is widely used for dynamic analyzing mooring cables in ocean. Both motions of cables and loads acting on cables are expressed with respect to the element frames. Generally, Frenet frame, which is suitable for continuous and differentiable space curves, is widely used for the lumped mass modeling in former researches. The rotational transformation matrix is based on Euler angles of which the rotation angles are carried out by inverse kinematics. However, singularities exist in the combination of the Frenet frame and Euler angles. This paper puts forward a new element frame which is created based on vectors of element orientation and relative velocity. Comparisons with the results by the Frenet frame show this new element frame is stable and overcomes singularities well.

Flexible dynamic analysis of an offshore wind turbine installed on a floating spar platform

Zhu, Xiangqian,Yoo, Wan-Suk SAGE Publications 2016 Advances in mechanical engineering Vol.8 No.6

Analysis of notch depth and loading rate effects on crack growth in concrete by FE and DIC

Xiangyi Zhu,Xudong Chen,Jun Lu,Xiangqian Fan 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.6

In this paper, the fracture characteristics of concrete specimens with different notch depths under three-point flexural loads are studied by finite element and fracture mechanics methods. Firstly, the concrete beams (the size is 700×100×150 mm) with different notch depths (a=30 mm, 45 mm, 60 mm and 75 mm respectively) are tested to study the influence of notch depths on the mechanical properties of concrete. Subsequently, the concrete beams with notch depth of 60 mm are loaded at different loading rates to study the influence of loading rates on the fracture characteristics, and digital image correlation (DIC) is used to monitor the strain nephogram at different loading rates. The test results show that the flexural characteristics of the beams are influenced by notch depths, and the bearing capacity and ductility of the concrete decrease with the increase of notch depths. Moreover, the peak load of concrete beam gradually increases with the increase of loading rate. Then, the fracture energy of the beams is accurately calculated by tail-modeling method and the bilinear softening constitutive model of fracture behavior is determined by using the modified fracture energy. Finally, the bilinear softening constitutive function is embedded into the finite element (FE) model for numerical simulation. Through the comparison of the test results and finite element analysis, the bilinear softening model determined by the tail-modeling method can be used to predict the fracture behavior of concrete beams under different notch depths and loading rates.

Mechanical properties of pervious concrete with recycled aggregate

Xiangyi Zhu,Xudong Chen,Nan Shen,Huaxuan Tian,Xiangqian Fan,Jun Lu 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.6

In order to research the influence of different recycled aggregate contents on the mechanical properties of pervious concrete, the experimental study and numerical simulation analysis of the mechanical properties of pervious concrete with five kinds of recycled aggregates contents (0%, 25%, 50%, 75% and 100%) are carried out in this paper. The experimental test were first performed on concrete specimens of different sizes in order to determine the influence of recycled aggregate on the compressive strength and splitting tensile strength, direct tension strength and bending strength. Then, the development of the internal cracks of pervious concrete under different working conditions is studied more intuitively by PFC3D. The experimental results show that the concrete compressive strength, tensile strength and bending strength decrease with the increase of the recycled aggregate contents. This trend of reduction is not only related to the brittleness of recycled aggregate concrete, but also to the weak viscosity of recycled aggregate and cement paste. It is found that the fracture surface of pervious concrete with recycled aggregate is smoother than that of natural aggregate pervious concrete by PFC3D, which means that the bridging effect is weakened in the stress transfer between the left and right sides of the crack. Through the analysis of the development of the internal cracks, the recycled aggregate concrete generated more cracks than the natural aggregate concrete, which means that the recycled aggregate concrete is easier to form a coalescence fracture surface and eventually break.

Lightweight Design of an Electric Tricycle Frame Considering Dynamic Stress in Driving Conditions

Pan Longye,Zhu Xiangqian,Li Yang,Guan Tingcheng 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.4

Since most tricycles are driven on rough roads, a static analysis of the frame with a constant load and a specific boundary condition is insufficient to assess whether the lightweight design satisfies the strength requirements. A flexible multibody dynamics approach is used to assess the dynamic stress of a tricycle frame in five driving conditions to determine the positions where material can be removed. The five driving conditions, including high-speed driving, turning, climbing, braking and driving on a bumpy road, are established according to two national standards. An electric tricycle prototype is modeled using the rigid-flexible coupling method, and experiments are conducted to adjust the center of mass and stiffness of the suspension. The frame stress results obtained from the simulation are in good agreement with the loading test results. Subsequently, the dynamic stress of the frame is analyzed, and a steel plate with a suitable thickness is selected according to the stress distribution and the allowable stress. The modified frame is about 19.1 % lighter, and the maximum stress is only 2.8 % larger than that of the prototype. The results demonstrate that the proposed method is suitable for the lightweight design of one component in a system operating under various working conditions.

Enhanced electrochemical performance of Ca-doped NdBa_1-xCa_xCoCuO_5+δ as cathode material for intermediate-temperature solid oxide fuel cells

Pang, Shengli,Su, Yanjing,Yang, Gongmei,Shen, Xiangqian,Zhu, Meng,Wu, Xiao,Li, Songwei,Yang, Xiaofen,Xi, Xiaoming Elsevier 2018 Ceramics international Vol.44 No.17

<P><B>Abstract</B></P> <P>Exploring advanced cathode materials that have high electrochemical activity and superior thermal compatibility with other components is of great importance for the application of intermediate-temperature solid oxide fuel cells. In the present study, influences of Ca doping on electrochemical and physicochemical properties of NdBa<SUB>1-x</SUB>Ca<SUB>x</SUB>CoCuO<SUB>5+δ</SUB> were studied systematically. A relatively low thermal expansion coefficient (16.8 × 10<SUP>−6</SUP> °C<SUP>−1</SUP>) was obtained for the Ca-doped sample over the temperature range of 25–800 °C. Moreover, Ca doping significantly enhanced the electrochemical performance of NdBa<SUB>1-x</SUB>Ca<SUB>x</SUB>CoCuO<SUB>5+δ</SUB>. The highest densities of power for NdBa<SUB>1-x</SUB>Ca<SUB>x</SUB>CoCuO<SUB>5+δ</SUB>-based single cells at the temperatures of 800 °C increased from 1.42 W cm<SUP>−2</SUP> for x = 0.0 to 1.84 W cm<SUP>−2</SUP> for x = 0.3. This increase in electrochemical performance of NdBa<SUB>1-x</SUB>Ca<SUB>x</SUB>CoCuO<SUB>5+δ</SUB> cathode with Ca doping can be ascribed to enhanced concentrations of oxygen vacancies and higher electrical conductivity.</P>

Ultra-Precision Diamond Turning Error Compensation via Iterative Learning from On-machine Measured Data

ZaoZao Chen,WeiWei Huang,ZhiWei Zhu,XinQuan Zhang,LiMin Zhu,XiangQian Jiang 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.12

In ultra-precision diamond turning, the reduction of machining form errors can generally be achieved through on-machine measurement and compensation. However, the efficiency of conventional compensation methods is often insufficient, particularly when high form accuracy is required or when intricate surface topography and microstructures need to be machined. Consequently, this research proposes a novel machining error compensation method based on iterative learning from on-machine measured data to enhance the machining accuracy and compensation efficiency. The on-machine measurement system and cutting path generation algorithm are introduced first. Then, the compensation method via iterative learning is presented theoretically, demonstrating a higher convergence order compared to the conventional method. Finally, machining experiments involving the cutting of cosine surfaces are conducted, followed by measurements of the processed workpieces. The experimental results indicate that after four rounds of compensation using the conventional method, the peak-to-valley (PV) value of the form error is reduced to 0.1134 μm. In contrast, employing the proposed method, a similar value of 0.1156 μmis achieved after only two rounds of compensation. This highlights the significant reduction in compensation time facilitated by the proposed method. Furthermore, the measurement results verify that the proposed compensation method maintains excellent surface quality.