Jerry L. Ericksen接受1979年Timoshenko奖章的演讲

1979年12月6日，纽约。首先，我对能与季莫申科这个骄傲的名字联系在一起感到荣幸和高兴。这些年来，我对他的尊敬与日俱增，因为我越来越欣赏他为提升力学和工程教育所做的贡献。他帮助开创的潮流一直延续到今天，以至于他的作品看起来相当天真和单纯。在某种程度上，这与该主题的发展自然有关。这也可能反映出他的一些良好判断。一些相当保守的专业人士会接受的改变是有限度的。如果它们想要避免过时，就需要一些鞭策。总的来说，我们这些人代表了一种我们称之为应用力学的活动。就像社交俱乐部一样，它有一种正式的组织结构，否则我们今晚就不会在这里了。 At least some like to think of it as more than a club, a profession or something like it. As a profession, it has some responsibility to pinpoint or generate the interesting and important problems, and to find ways to bring to bear the best talent to solve these. Where it fails, the profession will lose ground to another which is more effective. Times have become harder, so we can ill-afford to lose ground, and we should be more aggressive in finding new turf. I would like to reminisce about personal experiences, to illustrate these points.

特别是，我记得罗纳德·里夫林以前两次介绍我的时候。一次是我在亚特兰大ASME会议上的演讲。后来，他认为如果我下次表演以哑剧的形式出现会是个好主意。今晚，我将无视你的忠告，闭上我的嘴。另一件事要追溯到许多年前，当时我在印第安纳大学读数学研究生。那么，涉及到的不是他个人，而是他的研究。我对数学本身不是很感兴趣，而是对能用数学做些什么感兴趣。我对连续介质力学的课程更感兴趣，但不太符合要求。在我的最后一年，Clifford Truesdell加入了教员，并开设了一门关于一般连续介质力学的课程，涵盖了他后来发表的著名文章，“弹性和流体动力学的力学基础”。里夫林关于橡胶弹性和非牛顿流体的富有想象力的工作让我兴奋不已，我迷上了这个主题。 I then moved to the Naval Research Laboratory which was, for a time, a center of the activity. It is still pleasant to remember the heated but friendly arguments concerning the foundations of continuum physics, with Rivlin and Richard Toupin, particularly. Imaginative work can induce young people to enter into a field, if they learn of it. Rivlin's work got me involved but, except for Truesdell, I might not have encountered it.

当时，应用力学界太保守了，对三维非线性弹性理论和粘弹性理论这样深奥的东西不感兴趣，所以我们在其他地方接触了。

当时，对这些课题的实际兴趣主要与高聚物生产和使用中出现的问题有关。经典流体理论无法描述在用于旋转合成纤维的熔体或溶液中观察到的行为。在橡胶状固体中，我们感兴趣的变形太大了，不能用应用力学中常用的无穷小变形理论来描述。在早些时候，“化学让生活更美好”这句著名的口号应用得相当好。大多数研究都是由化学家或化学工程师完成的，几乎没有受过力学方面的训练。他们遇到了真正的问题，在力学上有复杂的性质，字面意义上的应用力学。应用力学专业的人可能已经为这个机构创造了一套新的工作;如果他们更有侵略性。相反，那些主要参与的人与我们合作。我帮助他们中的一些人学习力学，他们与我分享他们的知识。 As a visiting professor of chemical engineering at Delaware, I gave one of the first courses on general continuum mechanics, for this profession. However, most of the mutual education was accomplished by much less formal means. There were groups outside universities which played an important role in fostering such cooperation, like the Mellon Institute and the Rheology Section at the National Bureau of Standards. Gradually, various universities evolved more formal training programs, helping to bridge the gaps. It has been years since I worked on viscoelasticity theory, but I still communicate with those in polymer rheology, for example. Gradually, such theory has become more accepted in Applied Mechanics, but it would not be fair to say that the center of activity is now here.

我并没有失去对非线性弹性理论和热弹性理论的热爱。我很喜欢他们提出的那些数学问题，所以看到它们的新用途我很高兴。长期以来，人们已经认识到它们对橡胶和典型屈曲现象的分析是有用的。我对一个不同的应用领域更感兴趣，这有助于阐明对这种理论的一些误解。我指的是固体中的相变。一种现象是在你可能使用过的材料中遇到的，或者在广告中看到的，热收缩绝缘材料。温度升高到一定程度，它就会收缩。类似的事情发生在各种聚合物中，也发生在所谓的记忆合金中，比如镍钛合金。通常情况下，晶体的对称性会随着温度的变化而变化。目前，我们还不知道如何正确地分析这种影响。 When I first began to think about them, I thought that, surely, the answers were to be found in works on classical physics. I soon found that they are not, and that parts of the theory are in a controversial state. Somehow, existing concepts are not quite right, and we need to find proper modifications. I rather like to try my hand at this kind of activity.

现在，我们都熟悉一些使用液晶的设备。还有手表或小型计算器上的数字显示。有一些杯垫，当冷饮放在上面时，会进化出漂亮的颜色图案，类似的事情有时会在用于人体和无生命物体无损测试的设备中遇到。乍一看，这似乎是光学或电子所涉及的，而不是力学。实际上，光学行为等的变化与取向的变化有关。反过来，这些是由夫妻产生的。非常粗略地说，它类似于通过施加偶来弯曲金属丝。

至少在某种程度上，我因为对这些理论的贡献而感到荣幸。因此，我将请您允许我叙述一些更个人的历史。来到霍普金斯大学后不久，我就开始研究液晶，那时我还不知道液晶的存在。对基础的研究表明，流体力学文献中关于各向异性流体的评论是基于错误的概念。我当时在教一门连续介质力学的课程，我认为提出一个简单的各向异性流体理论，符合基本原理，会很有指导意义，所以我就这么做了。这是一种结构化的连续性理论，让人想起我在Cosserats和其他人的著作中读到的旧理论。我认为发展这样的理论是值得的，对于一些真实的材料。化学家很可能知道好的前景，所以我在ACS会议上寻求建议。有人告诉我，我的想法意味着液晶;我现在知道了他们的存在。 I soon became fascinated with their beauty and unusual behavior, soon realized that familiar theories of fluids would not work. Gradually, I plugged away at the theory, to understand how it operated and to make the modifications which seemed to be needed. Almost a decade later, Frank Leslie came to work with me, putting together the final version. Almost immediately, the theory passed its first real test, correctly describing the unusual scaling behavior in Poiseuille flow observed by Fisher and Frederickson. For a long time, this has been an activity in pure science, largely chemistry, but the scene was beginning to change. I had encountered and had fruitful exchanges of ideas with one physicist interested in developing practical devices, James Fergason, then at Westinghouse. Rather suddenly, interest in possible applications perked up, and we began to see more such people. An influential theoretical physicist, Pierre de Gennes, became interested, and formed a very active group at Orsay. We corresponded a bit, about adaptation of theory to cover light scattering. Soon, they were using this to measure viscosities, branching out to cover the other aspects of basic physics, and interesting other physicists. From a selfish point of view, such efforts did much to speed up testing of the continuum theory, which is now well accepted. My original goal was attained, so my interest shifted to other questions. When I began, the basic concept of structured continua, Cosserat continua, or whatever you like to call it, was essentially unused, in Applied Mechanics. In the meantime, a number of others have tried out variations of the idea, on different areas of application, some with success. In liquid crystal research, there is room for those who like the kinds of problems which are encountered in ordinary viscous fluids, to analyze hydrodynamic instabilities, for example. Some such work has been done, mainly by physicists. There are numerous instabilities which occur at very low Reynold numbers, having no counterpart in ordinary fluids. Some have been analyzed fairly well. There are very detailed measurements, motion pictures, etc. of others, not yet analyzed. Liquid crystal research is beginning to overlap polymer research, in an important way. Highly oriented polymer fibers, of exceptionally high strength, are now being made and used commercially. These are spun from a liquid, a polymer solution. The trick is to prepare this so it is already well oriented. Qualitatively, this is, in effect, a liquid crystal. Some of the available data indicates that the theory will have to be modified somewhat, to cover these newer fluids, but we can make good use of some of the experience acquired, and the polymer workers are pursuing this.

我的经验告诉我，应用力学有两种完全不同的含义。首先，它作为一种具有相当狭窄和固定范围的职业的名称。粘弹性流体不属于流体力学。作为一个年轻人，我觉得这种态度对我来说太古板了，现在我仍然这样认为。其次，我们遇到了许多力学在实际问题中的应用。如果这个行业太不愿意在这些方面提供专家帮助，它就不配这个名字;这实际上是一个私人俱乐部。在经济景气的时候，这个行业或许还能生存下来，但最近几年就不那么容易了，一些领域已经被其他行业抢走了。如果你愿意，你可以把这些捕食者称为秃鹫，但你要问秃鹫是否更喜欢攻击健康、有活力的猎物。

在《力学》中，场景正在以其他方式发生变化，至少部分是因为经济压力。一些人看到了整个主题的转变，变得更加关注眼前的应用。我认为它可能会同时变得更多和更少的应用，这是我所希望的。随着数学家或其他纯科学家的转变，他可能会从最不实用的一端进入，我看到这种情况正在发生。我在液晶研究和聚合物力学方面的经验表明，当有着不同背景的人在对某个问题的共同兴趣的刺激下交流，才能取得更实际的进展。最近的邻居往往想法相似，陷入现在可能很舒服，但正走向流沙的窠臼。作为一个群体，我们在力学似乎有一个名声，即不能容忍那些与我们意见不一致的人。被这刺痛的人会高兴地看到我们消失在泥潭里。也许这是一厢情愿的想法，但我相信，总的来说，我们正在向更好的方向发展。

我看到更多的专业人士在栅栏之外冒险，发现经验是有益的，并在与我所提到的完全不同的领域做出贡献。我们仍然需要做更多的工作来帮助最优秀的人才解决最好的问题。领域开始变化是因为有人得到了一个新颖的想法或技术，而其他人看到了看起来有吸引力的分支。我个人的观点是，尽我们所能促进最好的研究最符合我们自己的利益。我不知道该做些什么来制造更多的火花塞，但我们可以警惕地寻找方法来帮助那些正在燃烧的火花塞。评估一些聪明的年轻人的才能，帮助他们找到合适的机会，这是相当可行的。这需要我们和他们有一些接触，如果有更多这样的接触我会更开心。和你们中的一些人一样，我一直在思考和尝试改善这些情况的方法。也许，现在是评估这些努力的价值的时候，但不是地点。

有时候，演讲者对演讲的热情必须让位于对听众疲惫的身体的关心。谢谢你听我絮絮叨叨。