The piezoelectric effect is used in sensing applications such as in force and displacement sensors.However,the brittleness and low performance of piezoceramic lead zirconate titanate(PZT) often impede its applicabilit...The piezoelectric effect is used in sensing applications such as in force and displacement sensors.However,the brittleness and low performance of piezoceramic lead zirconate titanate(PZT) often impede its applicability in civil structures which are subjected to large loads.The concept of a piezocomposite electricity generating element(PCGE) has been proposed for improving the electricity generation performance and overcoming the brittleness of piezoceramic wafers.The post-curing residual stress in the PZT layer constitutes a main reason for the PCGE's enhanced performance,and the outer epoxy-based composites protect the brittle PZT layer.A d33-mode PCGE designed for bridge monitoring application was inserted in a bridge bearing to provide a permanent and simple weigh-in-motion system.The designed PCGEs were tested through a series of tests including fatigue and dynamic tests to verify their applicability for monitoring purposes in a bridge structure.A simple beam example was presented to show the applicability of the proposed bridge bearing equipped with the PCGE for adequately measuring the traffic loads.展开更多
End windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windin...End windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements. Due to the complex structure and unknown boundary conditions, the conventionally calculation of stator end windings has been very difficult and time consuming up to now. This paper describes the development of a full parameterized modeling tool, which allows a quick calculation of natural frequencies during the design phase of the generator. To keep the computing time low, it is important to find a way to get exact calculation results without detailed modeling of all pans. Additionally, special attention was paid to the active part, which has been replaced by spring-damper elements, and the determination of their stiffness via experimental modal analysis combined with finite element calculations.展开更多
The end windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage （especially in case of resonance） and noise. To avoid this, it is important to predict the natural...The end windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage （especially in case of resonance） and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements during the design process. Hence, a material model of the complete stator bar is necessary. This paper shows the development of such a material model. The composite structure of a stator bar is quite complex and makes it impossible to provide a quick calculation of the eigenvalues. That is the reason for using a suitable, homogeneously, geometry based solid model. Special attention was paid to the experimental determination of the material characteristics of the orthotropic composite space brackets. The numerical results have been evaluated against measurements. Eigenvalues, Young＇s modulus, and shear modulus have been experimentally investigated.展开更多
In this study, a circular plate that is installing a piezoelectric element at its center is adopted as energy-harvesting system and is subjected to a harmonic point force. Because this system cannot avoid the influenc...In this study, a circular plate that is installing a piezoelectric element at its center is adopted as energy-harvesting system and is subjected to a harmonic point force. Because this system cannot avoid the influence of its acoustic radiation, the influence is considered theoretically using the equation of plate motion taking into account its radiation impedance and is estimated by the electricity generation efficiency, which is derived from the ratio of the electric power in the electricity generation and the mechanical power supplied to the plate. As a result, the efficiency is suppressed by the acoustic radiation from the plate, so that the efficiencies are so different in whether to take into consideration the radiation impedance or not. Because those results are verified by the electricity generation experiment and radiation acoustic energy has a hopeful prospect for improving the performance of this system, mechanical-acoustic coupling is used to make the most of the acoustic energy. Therefore, a cylinder that has the above plates at both ends is also adopted as the electricity generation system and mechanical-acoustic coupling is caused between the plate vibrations and an internal sound field into the cylindrical enclosure by subjecting one side of each plate to a harmonic point force. Then, the effect of coupling is evaluated by comparing with the efficiencies in the electricity generation system of only plate. Specifically, because the radiation impedance increases with the plate thickness, i.e., with the natural frequency of the plate, it is demonstrated that the effect of coupling becomes remarkable with increasing the thickness on the electricity generation efficiency.展开更多
特高压直流输电系统阀厅内部结构复杂,采用有限元(FEM)法模拟计算其内部电场时剖分困难。为此,结合某±800 k V特高压换流站阀厅的3维全模型,基于模块化与独立化的思想,提出了实体模型区域化网格剖分方法。该方法克服了复杂模型下...特高压直流输电系统阀厅内部结构复杂,采用有限元(FEM)法模拟计算其内部电场时剖分困难。为此,结合某±800 k V特高压换流站阀厅的3维全模型,基于模块化与独立化的思想,提出了实体模型区域化网格剖分方法。该方法克服了复杂模型下网格剖分困难、对计算机硬件要求高的问题,剖分后可获得质量较高的网格。针对模型单元数较多的情况,选用不完全Cholesky分解预处理共轭梯度法(ICCG)求解复杂模型的有限元方程组。最后结合区域网格剖分与子模型技术,实现了阀厅内局部区域电场强度的准确计算。结果表明:将求解域尺寸设置为内部模型尺寸的1.3倍以上时,所得到的切割边界符合子模型计算要求,此时边界上的最大计算误差≤2%,子模型电场计算精度满足要求。展开更多
有限元法是电场数值计算中普遍采用的一种方法,当求解域内实体较多且结构复杂时,整体模型的区域离散往往难度较大。为此,基于模型的基本几何形态,提出一种针对复杂模型电场数值分析的快速建模剖分方法。以简单2维模型为例,介绍外包区域...有限元法是电场数值计算中普遍采用的一种方法,当求解域内实体较多且结构复杂时,整体模型的区域离散往往难度较大。为此,基于模型的基本几何形态,提出一种针对复杂模型电场数值分析的快速建模剖分方法。以简单2维模型为例,介绍外包区域实体生成及相互位置关系判断算法,结合有限元电场计算时的网格剖分策略,参数化实现模型表面多层网格加密,剖分的效率及质量较高。将该方法应用于特高压直流(ultra high voltage direct current,UHVDC)阀厅设备表面电场计算中,计算结果表明:该方法较子模型法计算所得结果最大误差仅为3.80%,计算效率较子模型法大幅提高。该方法实现了大型复杂模型表面网格精细化控制,对大规模有限元电场计算的快速、准确建模具有一定指导意义。展开更多
基金Project supported by Konkuk University,Korea,in 2014
文摘The piezoelectric effect is used in sensing applications such as in force and displacement sensors.However,the brittleness and low performance of piezoceramic lead zirconate titanate(PZT) often impede its applicability in civil structures which are subjected to large loads.The concept of a piezocomposite electricity generating element(PCGE) has been proposed for improving the electricity generation performance and overcoming the brittleness of piezoceramic wafers.The post-curing residual stress in the PZT layer constitutes a main reason for the PCGE's enhanced performance,and the outer epoxy-based composites protect the brittle PZT layer.A d33-mode PCGE designed for bridge monitoring application was inserted in a bridge bearing to provide a permanent and simple weigh-in-motion system.The designed PCGEs were tested through a series of tests including fatigue and dynamic tests to verify their applicability for monitoring purposes in a bridge structure.A simple beam example was presented to show the applicability of the proposed bridge bearing equipped with the PCGE for adequately measuring the traffic loads.
文摘End windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements. Due to the complex structure and unknown boundary conditions, the conventionally calculation of stator end windings has been very difficult and time consuming up to now. This paper describes the development of a full parameterized modeling tool, which allows a quick calculation of natural frequencies during the design phase of the generator. To keep the computing time low, it is important to find a way to get exact calculation results without detailed modeling of all pans. Additionally, special attention was paid to the active part, which has been replaced by spring-damper elements, and the determination of their stiffness via experimental modal analysis combined with finite element calculations.
文摘The end windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage （especially in case of resonance） and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements during the design process. Hence, a material model of the complete stator bar is necessary. This paper shows the development of such a material model. The composite structure of a stator bar is quite complex and makes it impossible to provide a quick calculation of the eigenvalues. That is the reason for using a suitable, homogeneously, geometry based solid model. Special attention was paid to the experimental determination of the material characteristics of the orthotropic composite space brackets. The numerical results have been evaluated against measurements. Eigenvalues, Young＇s modulus, and shear modulus have been experimentally investigated.
文摘In this study, a circular plate that is installing a piezoelectric element at its center is adopted as energy-harvesting system and is subjected to a harmonic point force. Because this system cannot avoid the influence of its acoustic radiation, the influence is considered theoretically using the equation of plate motion taking into account its radiation impedance and is estimated by the electricity generation efficiency, which is derived from the ratio of the electric power in the electricity generation and the mechanical power supplied to the plate. As a result, the efficiency is suppressed by the acoustic radiation from the plate, so that the efficiencies are so different in whether to take into consideration the radiation impedance or not. Because those results are verified by the electricity generation experiment and radiation acoustic energy has a hopeful prospect for improving the performance of this system, mechanical-acoustic coupling is used to make the most of the acoustic energy. Therefore, a cylinder that has the above plates at both ends is also adopted as the electricity generation system and mechanical-acoustic coupling is caused between the plate vibrations and an internal sound field into the cylindrical enclosure by subjecting one side of each plate to a harmonic point force. Then, the effect of coupling is evaluated by comparing with the efficiencies in the electricity generation system of only plate. Specifically, because the radiation impedance increases with the plate thickness, i.e., with the natural frequency of the plate, it is demonstrated that the effect of coupling becomes remarkable with increasing the thickness on the electricity generation efficiency.
文摘特高压直流输电系统阀厅内部结构复杂,采用有限元(FEM)法模拟计算其内部电场时剖分困难。为此,结合某±800 k V特高压换流站阀厅的3维全模型,基于模块化与独立化的思想,提出了实体模型区域化网格剖分方法。该方法克服了复杂模型下网格剖分困难、对计算机硬件要求高的问题,剖分后可获得质量较高的网格。针对模型单元数较多的情况,选用不完全Cholesky分解预处理共轭梯度法(ICCG)求解复杂模型的有限元方程组。最后结合区域网格剖分与子模型技术,实现了阀厅内局部区域电场强度的准确计算。结果表明:将求解域尺寸设置为内部模型尺寸的1.3倍以上时,所得到的切割边界符合子模型计算要求,此时边界上的最大计算误差≤2%,子模型电场计算精度满足要求。
文摘有限元法是电场数值计算中普遍采用的一种方法,当求解域内实体较多且结构复杂时,整体模型的区域离散往往难度较大。为此,基于模型的基本几何形态,提出一种针对复杂模型电场数值分析的快速建模剖分方法。以简单2维模型为例,介绍外包区域实体生成及相互位置关系判断算法,结合有限元电场计算时的网格剖分策略,参数化实现模型表面多层网格加密,剖分的效率及质量较高。将该方法应用于特高压直流(ultra high voltage direct current,UHVDC)阀厅设备表面电场计算中,计算结果表明:该方法较子模型法计算所得结果最大误差仅为3.80%,计算效率较子模型法大幅提高。该方法实现了大型复杂模型表面网格精细化控制,对大规模有限元电场计算的快速、准确建模具有一定指导意义。
