名譽(yù)博士授予儀式及學(xué)術(shù)報(bào)告（1）
時(shí)間：2011年9月7號下午1:30pm-3:30pm
地點(diǎn)：浙江大學(xué)紫金港校區(qū)蒙民偉樓138
報(bào)告題目：Riding the Waves
報(bào)告人：美國西北大學(xué)Jan D Achenbach教授
主持人：浙江大學(xué)副校長來茂德教授
學(xué)術(shù)報(bào)告（2）
時(shí)間：2011年9月8號上午10:00am-11:30am
地點(diǎn)：浙江大學(xué)玉泉校區(qū)教12-118
報(bào)告題目：Surface Waves on a Solid Body with Depth-Dependent Properties
報(bào)告人：美國西北大學(xué)Jan D Achenbach教授
主持人：陳偉球教授
報(bào)告人簡介
Jan D. Achenbach，美國西北大學(xué)土木與機(jī)械工程系Walter P. Murphy和McCormick杰出學(xué)院教授，他在固體力學(xué)和無損檢測領(lǐng)域作出了杰出的貢獻(xiàn)，特別是力學(xué)擾動的傳播、定量無損檢測、復(fù)合材料損傷機(jī)理、復(fù)雜結(jié)構(gòu)振動等問題，并獲得了代表美國技術(shù)和科學(xué)領(lǐng)域創(chuàng)新最高榮譽(yù)的國家技術(shù)獎(jiǎng)（2003）和國家科學(xué)獎(jiǎng)（2005）。他分別于1982、1992和1994年入選美國工程院、科學(xué)院和藝術(shù)與科學(xué)院院士，并在1999年入選荷蘭皇家科學(xué)院。他是美國機(jī)械工程師學(xué)會的榮譽(yù)會員，是ASME、ASA、SES、AMA和AAAS的Fellow。Achenbach教授多次獲得科技領(lǐng)域的著名獎(jiǎng)項(xiàng)，包括Timoshenko獎(jiǎng)、William Prager獎(jiǎng)和Theodore von Karman獎(jiǎng)。他培養(yǎng)了一批杰出的力學(xué)家和工程師。
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.
