1. Introduction To improve students English proficiency, Chinese education authorities and universities encourage instructors to teach bilingually. In bilingual teaching, students are required to read textbooks in English, and instructors should write blackboard in English and lecture in English and Chinese, in variable proportion. Thus, the precondition of bilingual teaching is the access to textbooks in English. For the course on statics and dynamics, thank to the publishers effort, a few popular western textbooks have been legally distributed in China . Nevertheless, not all western textbooks are usable in Chinese universities. For an extreme example, all textbooks depending on national codes and standards are generally not codes and regulations. Obviously, statics and dynamics do not belong to that category. However, since the differences in teaching contents and the diversity in textbook usages, the suitability of western textbooks is still a problem even for a course line statics and dynamics. This problem will be treated here. At first, the course on statics and dynamics taught in Chinese universities is described. Then the differences in the contents are highlighted. Finally the appropriateness of the western textbooks used in Chinese universities is discussed and a suggestion is proposed. 2. Course designed in Chinese Universities In Chinese universities, statics and dynamics, or engineering mechanics as referred in the north America, are called theoretical mechanics, which is a usage adopted from former Soviet Union. It is taught for students majoring in mechanical, civil, aeronautical, and astronautical engineering as well as engineering mechanics. Engineering mechanics students will take two more courses in the direction, namely, advanced dynamics and vibrations. For most other engineering students, there are no further courses on dynamics, while a few of them may take an optional course on vibrations. The theoretical mechanics course is covered in 60 to 80 hours, depending on the major and the university. The course is usually taught in 20 weeks, a semester or two trimesters. In addition to an introduction to describe the subject and the course, theoretical mechanics typically consists of three parts, statics, kinematics, and dynamics . Usually, less than a third lecturing time is devoted to statics, about a fourth to kinematics, and the others to dynamics. Although there are certain differences among the Chinese textbooks, they have a common core material, which is specified by a document titled The Essential Requirement of Teaching Theoretical Mechanics issued by the Guidance Committee of Mechanics Teaching, Ministry of Education, PRC. Statics covers equivalence, reduction, and equilibrium. It begins with basic concepts such as forces, moments, couples, constraints, and a basic approach, free-body diagram. Concurrent forces, couples, and general force systems, are treated to reduce equivalently, and centers of gravity are introduced as an example of the system of parallel forces. Equations of equilibrium is derived and applied to a rigid body or a system with a few rigid bodies. The equations are also applied to equilibrium problems involving friction and analysis of trusses. Kinematics begins with motion of a point, translation of a rigid body, and rotation of a rigid body about a fixed axis. Then composite motion of a point is presented. Velocities and accelerations are analyzed for motion of a point relative to a translating reference frame and a rotating reference frame. Kinematics closes with the discussions on rigid bodies, with the emphasis on general plane motions. Dynamics contains both vector dynamics and introductory analytical mechanics. It begins with dynamics of a particle, including Newton s law and its application in relative motion. Dynamics of a system of particles focuses on theorem of momentum, theorem of angular momentum, and theorem of kinetic energy. Rigid bodies are treated as a special system of particles, with the emphasis on plane motions. Here also introduces some specific topics such as propulsion with variable mass, steady fluid streams, impact, gyroscopic effects, and vibrations. Vector dynamics ends with the method of kineto-statics that is a practical approach to transform dynamics to statics by adding necessary imaginary inertial forces. Analytical mechanics begins with principle of virtual work. Then Lagranges equations are derived form the DAlembert-Lagrange principle, and its applications, including the generalized energy and momentum integrals are discussed. Sometimes advanced topics such as Hamilton s equations and Hamilton s principle are referred. 3. Contrasts with Western Textbooks Compared with typical contents presented in western textbooks on engineering mechanics , there are some significant differences in statics, kinematics, and dynamics. In statics, theoretical mechanics does cover structural analysis, internal forces, and moments of inertia, which all appear in engineering mechanics. Besides, distributed forces are not treated so detailed. These contents are taught in another course, mechanics of materials. Method of virtual work is usually presented in dynamics, although recently some instructors prefer to follow the western practices. However, they found it difficult for students to establish the relations between the virtual displacements, as they do not have necessary background in kinematics. The contents in kinematics are essentially the same, while kinematics in engineering mechanics is not a separate part, and scatters in dynamics instead. Both practices have their own advantages, which will not be reviewed here. In addition, theoretical mechanics stresses more on composite motion of a point and usually does not deal with 3-dimensional motion of rigid bodies in details. In dynamics, theoretical mechanics devotes a chapter to the method of kineto-statics, which is only very briefly referred as DAlemberts principle in engineering mechanics. Perhaps only an exception, applies the principle to dynamic balance of rigid rotors, which is a standard subjects in theoretical mechanics. What is more, another chapter in theoretical mechanics, Lagranges Equations, is not contained in engineering mechanics. In the western, the topic is treated in intermediate (or advanced) dynamics . 4. Discussions The teaching contents in Chinese universities will not substantially change because of the requirements of the education authorities and the transition of the instructors. If the western textbooks are used, to cover most of teaching contents, the students will need textbooks on engineering mechanics and intermediate dynamics. In such a way, about half of statics, some of dynamics, and most of intermediate dynamics will not be used. Besides, so far there have no western textbooks on intermediate dynamics distributed in China . It should be remarked that all second hand textbooks are not used in Chinese universities. As a result, instructors usually lecture most material of the textbooks that he requires or suggests his students to buy. Therefore, it seems feasible to use the western textbooks on engineering mechanics as textbooks of theoretical mechanics. On the other hand, bilingual teaching of theoretical mechanics needs extraordinary textbooks written in standard English. The styles of western textbooks on engineering mechanics are also especially attractive to both Chinese instructors and students. It is a dilemma. Collaboration of Chinese and western instructors on textbooks is a possible way to break away from the dilemma. Those books for Chinese students should be characterized by the following. They should cover all required material in theoretical mechanics textbooks in Chinese. If possible, the presentation should generally follow the Chinese way so that the instructors are easy to prepare their lectures; for example, kinematics should be a separate part. Some traits of the western counterpart should be preserved, such as in-chapter photographs, multicolor artwork, engineering-related examples and problems, necessary computerize exercises, and historical notes. Last but not least, they should be written in standard modern English. References A. Pytel J Kiusalaas, Engineering Mechanics: Statics and Dynamics (2nd ed.), Tsinghua University Press, 2001. F.P.Beer E.R. Johnston, Vector Mechanics for Engineers: Statics and Dynamics (3rd SI Ed.), Tsinghua University Press, 2003. R.C. Hibbeler, Engineering Mechanics: Statics and Dynamics (10th ed.), Higher Education Press, 2004. Q.S. Fan, K.Z. Xue, B.R. Cheng, Theoretical Mechanics, Higher Education Press, 2000 Y.Z. Liu, H. X. Yang, B. H. Zhu, Theoretical Mechanics (2nd ed.), Higher Education Press, 2001. L.Q. Chen, X.S. Ge, K. Y. Xu, Y. Xue, Theoretical Mechanics. Tsinghua University Press, 2006. S. Timoshenko D. H. Young, Engineering Mechanics (4th ed.), McGraw-Hill, 1985. J.H. Ginsberg, Advanced Engineering Dynamics (2nd ed.). Cambridge University Press, 1998. in Proceedings of 21 st Canadian Congress of Applied Mechanics ( Toronto , June 3-7, 2007) (Kawall G, Yu S, and Naylor D eds., 2007): 117-118
标签: 理论力学
