名誉博士授予仪式及学术报告（1）
时间：2011年9月7号下午1:30pm-3:30pm
地点：569vip威尼斯游戏紫金港校区蒙民伟楼138
报告题目：Riding the Waves
报告人：美国西北大学Jan D Achenbach教授
主持人：569vip威尼斯游戏副校长来茂德教授
学术报告（2）
时间：2011年9月8号上午10:00am-11:30am
地点：569vip威尼斯游戏玉泉校区教12-118
报告题目：Surface Waves on a Solid Body with Depth-Dependent Properties
报告人：美国西北大学Jan D Achenbach教授
主持人：陈伟球教授
报告人简介
Jan D. Achenbach，美国西北大学土木与机械工程系Walter P. Murphy和McCormick杰出学院教授，他在固体力学和无损检测领域作出了杰出的贡献，特别是力学扰动的传播、定量无损检测、复合材料损伤机理、复杂结构振动等问题，并获得了代表美国技术和科学领域创新最高荣誉的国家技术奖（2003）和国家科学奖（2005）。他分别于1982、1992和1994年入选美国工程院、科学院和艺术与科学院院士，并在1999年入选荷兰皇家科学院。他是美国机械工程师学会的荣誉会员，是ASME、ASA、SES、AMA和AAAS的Fellow。Achenbach教授多次获得科技领域的著名奖项，包括Timoshenko奖、William Prager奖和Theodore von Karman奖。他培养了一批杰出的力学家和工程师。
Riding the Waves
Jan D. Achenbach
McCormick School of Engineering and Applied Science
Northwestern University
Evanston, IL 60208, U.S.A.
Many natural phenomena involve mechanical wave motion. Conversely, artificially generated mechanical wave motion is employed extensively in the laboratory and in the field, primarily for diagnostic purposes. In this lecture, I will discuss some aspects of waves in solids I have worked on using analytical, numerical, and experimental methods, over a period of more than forty years. The first part of the lecture does, however, briefly discuss, how, as a member of the Sputnik generation, I became involved in interdisciplinary activities on waves in solids. In the last part of the lecture, titled “Theoretical and Applied Mechanics, the Crown Jewel of Engineering Analysis,” I will discuss briefly the past, present, and future of the field of mechanics.
Surface Waves on a Solid Body with Depth-Dependent Properties
Jan D. Achenbach
Northwestern University
Surface waves have probably been studied more thoroughly than any other kind of wave motion in solid materials. In a two-dimensional configuration, surface waves on an elastic body can be distinguished into in-plane and anti-plane surface waves. They occur at the surface of the earth, induced by earthquakes, and they are frequently generated for applications in science and technology, such as for testing procedures in non-destructive evaluation of materials and structures.
Many materials are not homogeneous. For an important class of materials the elastic moduli may vary only with distance from a free surface. Surface waves on such an elastic body with depth-dependent properties are of interest in seismology, but also for engineered functionally graded materials. In this talk we consider both anti-plane and in-plane surface waves on a half-space of an isotropic material whose elastic moduli λ and μ, and mass density, ρ, depend on the depth coordinate z.
A new potential for guided waves is introduced which breaks guided waves up in a carrier wave along the guiding surface(s) and a depth distribution. It is also shown that the reciprocity theorem, when formulated as relating body forces, surface tractions and displacements of the guided wave motion generated by an external excitation to the corresponding quantities of a “virtual” guided wave, provides an efficient method for determining the amplitudes of an externally generated wave motion.
The condition that the surface tractions vanish at the free surface yields the dispersion equation which relates the surface wave velocity to the wavenumber. For a class of examples that this equation yields a real valued surface wave velocity, conditions have been derived for the displacement amplitudes to decay exponentially with depth. Analytical results for the surface wave velocity as a function of the wavenumber have been compared with numerical results which were obtained when the continuous inhomogeneity with depth is replaced by an equivalent layering. For some typical cases of increasing and decreasing inhomogeneity with depth, excellent agreement has been obtained between analytical and numerical results.
