An imaging accuracy improving method is established, within which a distance coefficient including location information between sparse array configuration and the location of defect is proposed to select higher signal...An imaging accuracy improving method is established, within which a distance coefficient including location information between sparse array configuration and the location of defect is proposed to select higher signal- to-noise ratio data from all experimental data and then to use these selected data for elliptical imaging. Tile relationships among imaging accuracy, distance coefficient and residual direct wave are investigated, and then the residual direct wave is introduced to make the engineering application more convenient. The effectiveness of the proposed method is evaluated experimentally by sparse transducer array of a rectangle, and the results reveal that selecting experimental data of smaller distance coefficient can effectively improve imaging accuracy. Moreover, the direct wave difference increases with the decrease of the distance coefficient, which implies that the imaging accuracy can be effectively improved by using the experimental data of the larger direct wave difference.展开更多
有限元法(finite element method,FEM)具有几何适应性强但随分析频率增加计算时间成本迅速增加的特性,而波函数法(wave based method,WBM)拥有收敛性好但几何适应性差的特性。为减小离散单元带来的误差和提高分析频率,采用基于声压和法...有限元法(finite element method,FEM)具有几何适应性强但随分析频率增加计算时间成本迅速增加的特性,而波函数法(wave based method,WBM)拥有收敛性好但几何适应性差的特性。为减小离散单元带来的误差和提高分析频率,采用基于声压和法向速度连续性条件实现有限元法和波函数法混合建模的混合(finite elementwave based method,FE-WBM)。以车内声腔为例,建立了车内声腔的二维FE-WBM模型,实现了车内声学响应预测。FE-WBM模型与参考有限元模型的声压云图和响应点声压频响曲线对比的结果表明,FE-WBM模型与参考有限元模型的计算结果很好吻合,验证了混合FE-WBM的有效性。分别以模型自由度和CPU运行时间为自变量,以响应点相对误差为因变量,比较两种方法的收敛特性。结果表明,在相同误差水平下,FE-WBM模型在模型自由度和CPU运行时间方面较传统有限元都有明显的优势。展开更多
基于Kirchhoff薄板弯曲振动理论和波函数法Wave Based Method（WBM）理论,推导了运用WBM将附加弹簧阻尼结构转化为点激励的方法,构建了基于WBM计算含弹簧阻尼支承薄板振动响应的系统矩阵,得到了含弹簧阻尼支承的薄板弯曲振动响应。以四...基于Kirchhoff薄板弯曲振动理论和波函数法Wave Based Method（WBM）理论,推导了运用WBM将附加弹簧阻尼结构转化为点激励的方法,构建了基于WBM计算含弹簧阻尼支承薄板振动响应的系统矩阵,得到了含弹簧阻尼支承的薄板弯曲振动响应。以四边简支矩形板为例,计算了50~600 Hz频段内参考点的振动响应,并与解析法和有限元法的计算结果进行了对比。运用该方法对比计算了添加不同弹簧阻尼结构数与无弹簧阻尼结构时薄板在120 Hz的弯曲振动响应。结果表明：通过将弹簧阻尼结构转换成点激励的方法,能有效的将WBM应用于附加弹簧阻尼支承薄板弯曲振动响应的仿真计算,与有限元法相比,有着更高精度和收敛速度。展开更多
文摘An imaging accuracy improving method is established, within which a distance coefficient including location information between sparse array configuration and the location of defect is proposed to select higher signal- to-noise ratio data from all experimental data and then to use these selected data for elliptical imaging. Tile relationships among imaging accuracy, distance coefficient and residual direct wave are investigated, and then the residual direct wave is introduced to make the engineering application more convenient. The effectiveness of the proposed method is evaluated experimentally by sparse transducer array of a rectangle, and the results reveal that selecting experimental data of smaller distance coefficient can effectively improve imaging accuracy. Moreover, the direct wave difference increases with the decrease of the distance coefficient, which implies that the imaging accuracy can be effectively improved by using the experimental data of the larger direct wave difference.
基金Supported by the National Basic Research Program of China under Grant No. 2003 CB 716300the National Natural Science Foundation of China under Grant No. 10575140+2 种基金CAEP Foundation under Grant No. 2008T0401 and 2008T0402Chongqing University Postgraduates Science and Innovation Fund, Project No. 200811B1A0100299Chinese State Scholarship Fund
文摘有限元法(finite element method,FEM)具有几何适应性强但随分析频率增加计算时间成本迅速增加的特性,而波函数法(wave based method,WBM)拥有收敛性好但几何适应性差的特性。为减小离散单元带来的误差和提高分析频率,采用基于声压和法向速度连续性条件实现有限元法和波函数法混合建模的混合(finite elementwave based method,FE-WBM)。以车内声腔为例,建立了车内声腔的二维FE-WBM模型,实现了车内声学响应预测。FE-WBM模型与参考有限元模型的声压云图和响应点声压频响曲线对比的结果表明,FE-WBM模型与参考有限元模型的计算结果很好吻合,验证了混合FE-WBM的有效性。分别以模型自由度和CPU运行时间为自变量,以响应点相对误差为因变量,比较两种方法的收敛特性。结果表明,在相同误差水平下,FE-WBM模型在模型自由度和CPU运行时间方面较传统有限元都有明显的优势。
文摘基于Kirchhoff薄板弯曲振动理论和波函数法Wave Based Method（WBM）理论,推导了运用WBM将附加弹簧阻尼结构转化为点激励的方法,构建了基于WBM计算含弹簧阻尼支承薄板振动响应的系统矩阵,得到了含弹簧阻尼支承的薄板弯曲振动响应。以四边简支矩形板为例,计算了50~600 Hz频段内参考点的振动响应,并与解析法和有限元法的计算结果进行了对比。运用该方法对比计算了添加不同弹簧阻尼结构数与无弹簧阻尼结构时薄板在120 Hz的弯曲振动响应。结果表明：通过将弹簧阻尼结构转换成点激励的方法,能有效的将WBM应用于附加弹簧阻尼支承薄板弯曲振动响应的仿真计算,与有限元法相比,有着更高精度和收敛速度。
