高广健舞台美术作品赏析

点评高广健在歌剧《山村女教师》、《赵氏孤儿》,京剧《天下归心》、《赤壁》四部剧目中舞台美术的设计。

高广健：空间诠释者

大概是从事舞美设计专业的缘故。我始终认为不同的空间能够培养出气质截然不同的人。如同撰写这个人物。所花费的时间主要不是写的过程。而是整理他所累积的“素材”。铺排他所处的不同“空间”。完成我所能够勾勒出的“轮廓”。于是，高广值就这样进入了我脑海中的四个空间……

管间界面特性对周向超声导波传播特性的影响

采用界面弹簧模型对圆管结构的管间界面特性进行描述,推导出含弱界面的圆管结构中声波沿周向传播时的位移场及应力场的数学表达式.在此基础上采用导波的模式展开分析方法,给出了与管间界面特性及激励源密切相关的周向超声导波模式展开系数的解析表达式.数值分析了管间界面特性的变化对周向超声导波的频散和声场产生的影响.理论与数值分析结果表明,通过选择适当的驱动频率及周向导波模式,可使周向超声导波的相速度及圆管外表面的位移场随管间界面特性的变化表现出非常敏感且单调的性质.这一结果有助于采用周向超声导波方法准确定征圆管结构的管间界面特性.

圆管结构中周向导波非线性效应的模式展开分析

在二阶微扰近似条件下,采用导波模式展开分析方法研究了圆管结构中周向导波的非线性效应.伴随基频周向导波传播所发生的二次谐波,可视为由一系列二倍频周向导波模式叠加而成.从动量定理出发,结合柱坐标系下非线性应力张量及其散度的数学表达式,针对圆管中某一基频周向导波模式,推导出相应的二倍频应力张量及二倍频彻体驱动力的数学表达式,建立了确定二倍频周向导波模式展开系数的控制方程,得到了伴随基频周向导波传播所发生的二次谐波声场的形式解.理论分析和数值计算表明,当构成二次谐波声场的某一二倍频周向导波模式与基频周向导波的相速度匹配时,该二倍频周向导波模式的位移振幅表现出随传播周向角积累增长的性质;当两者的相速度失配时,二倍频周向导波的振幅随传播周向角表现出"拍"效应.

用于储罐底板缺陷检测的超声兰姆波模式研究

从超声兰姆波的声场方程出发,得到板材表面离面位移(法向位移)为零的条件,即当超声兰姆波的相速度等于板材介质的纵波声速时,在板材表面的离面位移为零。在给定适当频厚积的条件下,分别数值模拟了仅有切向位移而无离面位移的A1、S1、A2和S2兰姆波模式在有液体负载的单层钢板中的传播情形。结果表明:离面位移为零的S2模式频散较小且对板中缺陷更为敏感。

超声兰姆波在储罐底部传播的数值模拟研究

选择仅有切向位移分量的S2超声兰姆波模式,分别对其在自由单层钢板、有罐壁但无液体负载的单层钢板和有罐壁且有液体负载的单层钢板中的传播规律进行了数值模拟研究。计算结果表明,尽管罐壁和液体负载对超声兰姆波的传播行为产生了一定程度的影响,但仍可保证S2超声兰姆波模式的时域脉冲信号传播较远的距离。研究结果为采用超声兰姆波检测储罐的底部性质提供了理论依据。

超声兰姆波检测有液体负载钢板中缺陷的实验研究

0前言超声兰姆波因其在固体板中传播时声场可遍及整个板厚范围、多模特性及传播距离较远等特点,使其广泛应用于固体板状材料的无损检测[1]。众所周知,不同的兰姆波模式在固体板中具有不同的声场分布规律。迄今为止,所开展的工作大多是在频厚积取较小值的条件下,选择用于板材检测的低阶兰姆波模式(S0或A0模式)[2-4];然而。

电磁超声换能器激发超声兰姆波的模式展开分析

提出一种用于研究电磁超声换能器(EM.AT)激发超声兰姆波的模式展开分析方法。从EMAT曲折线圈的电流分布出发,推导出铝板表面洛伦兹切向应力的形式解;对其进行空间傅里叶变换,得到激发超声兰姆波的表面驱动应力之波数谱密度。在此基础上采用导波激发的模式展开分析方法,推导出与EMAT线圈的几何参数密切相关的兰姆波模式展开系数的数学表达式,为严格分析EMAT的兰姆波激发问题奠定了理论基础。数值分析结果表明,通过改变EMAT线圈的几何参数,可对兰姆波的模式展开系数进行适当调整,从而实现有效抑制不需要兰姆波模式的目的,这一结果为采用EMAT激发纯度高的单一兰姆波模式提供了理论依据。

EMAT激发超声兰姆波的模式展开分析

0前言因超声兰姆波的多模和频散特性,使其在激励、接收和模式识别等方面存在较大的复杂性[1]。本文提出一种研究电磁超声换能器(EMAT)激发超声兰姆波的模式展开分析方法。从EMAT曲折线圈的电流分布出发,推导出铝板表面洛伦兹切向应力的形式解;对其进行空间傅立叶变换,得到激发超声兰姆波的表面应力之波数谱密度。在此基础上采用导波的模式展开分析方法。

复合圆管界面特性对周向超声导波二次谐波发生效应的影响分析

研究了复合圆管的管间界面特性对周向超声导波二次谐波发生效应所产生的影响.在二阶微扰近似条件下,将周向超声导波传播过程中的非线性效应视为其线性波动响应的一个二阶微扰.采用界面弹簧模型对复合圆管的管间界面特性进行描述.根据导波的模式展开分析方法,伴随基频周向超声导波传播所发生的二次谐波可视为由一系列二倍频周向导波模式叠加而成.管间界面特性的变化可从多个方面对二倍频周向导波模式的展开系数及声场产生影响,尤其是界面特性的变化所引起的周向超声导波相速度的改变,将显著地影响到二次谐波随传播周向角的积累增长程度.理论及数值分析结果表明,周向超声导波的二次谐波发生效应随管间界面特性的改变而发生非常敏感的变化,可将其用于准确定征复合圆管的管间界面性质.

圆管结构中的非线性周向导波

采用将二阶微扰近似与模式展开分析相结合的方法,可从理论上有效求解圆管结构中的非线性周向导波问题。通过数值计算和有限元仿真发现,基频与二倍频周向导波模式的相速度匹配程度,可显著影响二倍频周向导波模式随传播周向角的积累增长程度。针对基频与二倍频周向导波模式的相速度和群速度均相匹配的情形,通过实验研究发现,周向导波确可存在强烈的非线性效应,且周向导波的二次谐波发生效应可对圆管早期损伤状态做出敏感的响应。文中给出的有关结果,可为进一步开展非线性周向导波的研究工作奠定理论和实验基础。

焊接薄板中S_0兰姆波对槽型缺陷响应特性的数值研究

采用数值仿真方法,就焊接薄板中S_0兰姆波对槽型缺陷的响应特性以及焊缝对S_0兰姆波槽型缺陷检测灵敏度的影响开展了数值研究。数值仿真结果表明,S_0_R信号(经槽型缺陷反射的S_0兰姆波回波信号)的反射比率随槽型缺陷深度的增大而单调增加;S_0_R信号的反射比率随槽型缺陷宽度的变化呈非单调变化关系,可将S_0_R信号的反射比率及其持续时间一并加以考虑,以评价槽型缺陷宽度的变化。随着焊缝余高的增加,S_0兰姆波对槽型缺陷的检测灵敏度将降低;随着焊缝宽度的增加,S_0兰姆波对槽型缺陷检测灵敏度的影响并不明显;相比之下,焊缝余高是影响S_0兰姆波槽型缺陷检测灵敏度的主要因素。研究结果表明,将S_0兰姆波用于检测隐藏于焊缝背后的槽型缺陷,是具有可行性的。所得结果对于发展焊接薄板的超声兰姆波无损检测技术,具有一定的理论指导意义和实际参考价值。

Numerical Perspective of Second-Harmonic Generation of Circumferential Guided Wave Propagation in a Circular Tube

The effect of second-harmonic generation （SHG） by primary （fundamental） circumferential guided wave （CGW） propagation is investigated from a numerical standpoint. To enable that the second harmonic of the primary CGW mode can accumulate along the circumferential direction, an appropriate mode pair of primary and double frequency CGWs is chosen. Finite element simulations and evaluations of nonlinear CGW propagation are analyzed for the selected CGW mode pair. The numerical simulations performed directly demonstrate that the response of SHG is completely generated by the desired primary CGW mode that satisfies the condition of phase velocity matching at a specific driving frequency, and that the second harmonic of the primary CGW mode does have a cumulative effect with circumferential angles. The numerical perspective obtained yields an insight into the complicated physical process of SHG of primary CGW propagation unavailable previously.

界面特性对兰姆波混频效应的影响

为有效定征层状复合材料的界面特性,对具有局部积累增长的兰姆波混频效应进行了建模及仿真,定位并评价了局部的界面特性退化。根据二阶微扰理论和模式展开方法,位于兰姆波混叠区中的混频谐波可视为一系列混频导波模式的叠加,局部界面特性的变化将显著影响混频谐波局部积累的增长程度。首先采用界面弹簧模型对层状板的界面特性进行描述,计算频散曲线;之后结合混频匹配条件,遴选出兰姆波模式组合。在此基础上,对该兰姆波模式组合在层状板中产生的混频谐波传播的物理过程进行有限元仿真,通过调整传播参数开展扫查分析,以定位并评价局部界面特性退化。仿真结果表明:混频谐波发生效应可较为敏感地反映界面特性局部微小变化,在层状板的界面特性无损检测方面有很大的潜力。

Enhancement effect of cumulative second-harmonic generation by closed propagation feature of circumferential guided waves

On the basis of second-order perturbation approximate and modal expansion approach,we investigate the enhancement effect of cumulative second-harmonic generation(SHG)of circumferential guided waves(CGWs)in a circular tube,which is inherently induced by the closed propagation feature of CGWs.An appropriate mode pair of primary-and double-frequency CGWs satisfying the phase velocity matching and nonzero energy flux is selected to ensure that the second harmonic generated by primary CGW propagation can accumulate along the circumference.Using a coherent superposition of multi-waves,a model of unidirectional CGW propagation is established for analyzing the enhancement effect of cumulative SHG of primary CGW mode selected.The theoretical analyses and numerical simulations performed directly demonstrate that the second harmonic generated does have a cumulative effect along the circumferential direction and the closed propagation feature of CGWs does enhance the magnitude of cumulative second harmonic generated.Potential applications of the enhancement effect of cumulative SHG of CGWs are considered and discussed.The theoretical analysis and numerical simulation perspective presented here yield an insight previously unavailable into the physical mechanism of the enhancement effect of cumulative SHG by closed propagation feature of CGWs in a circular tube.

Experimental Observation of Cumulative Second-Harmonic Generation of Circumferential Guided Wave Propagation in a Circular Tube

The experimental observation of cumulative second-harmonic generation of the primary circumferential guided wave propagation is reported. A pair of wedge transducers is used to generate the primary circumferential guided wave desired and to detect its fundamental-frequency and second-harmonic amplitudes on the outside surface of the circular tube. The amplitudes of the fundamental waves and the second harmonics of the circumferential guided wave propagation are measured for different separations between the two wedge transducers. At the driving frequency where the primary and the double-frequency circumferential guided waves have the same linear phase velocities, the clear second-harmonic signals can be observed. The quantitative relationships between the second-harmonic amplitudes and circumferential angle are analyzed. It is experimentally verified that the second harmonics of primary circumferential guided waves do have a cumulative growth effect with the circumferential angle.

Analysis of Second-Harmonic Generation of Low-Frequency Dilatational Lamb Waves in a Two-Layered Composite Plate

We analyze the effect of second-harmonic generation（SHG） of primary Lamb wave propagation in a two-layered composite plate, and then investigate the influence of interfacial properties on the said effect at low frequency. It is found that changes in the interfacial properties essentially affect the dispersion relation and then the maximum cumulative distance of the double-frequency Lamb wave generated. This will remarkably influence the efficiency of SHG. To overcome the complications arising from the inherent dispersion and multimode natures in analyzing the SHG effect of Lamb waves, the present work focuses on the analysis of the SHG effect of low-frequency dilatational Lamb wave propagation. Both the numerical analysis and finite element simulation indicate that the SHG effect of low-frequency dilatational Lamb wave propagation is found to be much more sensitive to changes in the interfacial properties than primary Lamb waves. The potential of using the SHG effect of low-frequency dilatational Lamb waves to characterize a minor change in the interfacial properties is analyzed.

Selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers

In this paper, we describe a modal expansion approach for the analysis of the selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers （EMATs）. With the modal expansion approach for waveguide excitation, an analytical expression of the Lamb wave＇s mode expansion coefficient is deduced, which is related to the driving frequency and the geometrical parameters of the EMAT＇s meander coil, and lays a theoretical foundation for exactly analyzing the selective generation of Larnb waves with EMATs. The influences of the driving frequency on the mode expansion coefficient of ultrasonic Lamb waves are analyzed when the EMAT＇s geometrical parameters are given. The numerical simulations and experimental examinations show that the ultrasonic Lamb wave modes can be effectively regulated （strengthened or restrained） by choosing an appropriate driving frequency of EMAT, with the geometrical parameters given. This result provides a theoretical and experimental basis for selectively generating a single and pure Lamb wave mode with EMATs.

一种新型的超声兰姆波换能器

针对固体板无损检测过程中超声兰姆波的多模态特性问题,设计并制作了一种可激发和接收单一超声兰姆波模式的新型超声兰姆波换能器。它由铜质叉指电极、导线、绝缘薄膜和YZ铌酸锂晶体等装配而成。采用矢量叠加法计算了叉指电极、YZ铌酸锂晶体相关参数,并将设计的叉指换能器应用于铝板的超声兰姆波检测实验中。实验结果表明,利用所设计的叉指超声兰姆波换能器,可有效克服兰姆波频散和多模式的特性、实现特定频率下单一模态超声兰姆波信号的激发与接收。

Response features of nonlinear circumferential guided wave on early damage in inner layer of a composite circular tube

A theoretical model to analyze the nonlinear circumferential guided wave(CGW) propagation in a composite circular tube(CCT) is established. The response features of nonlinear CGWs to early damage [denoted by variations in third-order elastic constants(TOECs)] in an inner layer of CCT are investigated. On the basis of the modal expansion approach, the second-harmonic field of primary CGW propagation can be assumed to be a linear sum of a series of double-frequency CGW(DFCGW) modes. The quantitative relationship of DFCGW mode versus the relative changes in the inner layer TOECs is then investigated. It is found that the changes in the inner layer TOECs of CCT will obviously affect the driving source of DFCGW mode and its modal expansion coefficient, which is intrinsically able to influence the efficiency of cumulative second-harmonic generation(SHG) by primary CGW propagation. Theoretical analyses and numerical simulations demonstrate that the second harmonic of primary CGW is monotonic and very sensitive to the changes in the inner layer TOECs of CCT, while the linear properties of primary CGW propagation almost remain unchanged. Our results provide a potential application for accurately characterizing the level of early damage in the inner layer of CCT through the efficiency of cumulative SHG by primary CGW propagation.