材料科学 Material Science
1. 你在“工程力学”这门课中都学习了哪些知识？ What did you learn in the course
“Engineering Mechanics”?
Mechanics can be divided into statics, kinematics and dynamics. The mechanics branch related with my profession is material mechanics. And statics is the foundation of material mechanics. So during this course we learn about Static mechanics first then learn about Materials mechanics.
2. 关于静力学，你都学习了哪些知识？ What knowledge have you learned about
Static mechanics?
Firstly, we learned some basic concept of Engineering Mechanics. Components are constituent parts of the machine and structure.
When a force is applied to an object, it may change the size and direction of the object's velocity, which is called the motion effect (external effect). On another hand, it may also change the shape of an object, which is called the deformation effect (internal effect). In the statics, we only consider the deformation effect of force.
Under the action of external force, the size and shape of the components have a change, and that change calls deformation. Deformation of components can be divided into two kinds. When the force is removed, some deformation disappear, components can recover its size and shape, those deformation calls elastic deformation. When the force is removed, some deformation remain, components can not recover its size and shape, those deformation calls plastic deformation.
The larger external force is, the larger deformation happen. When the external force get too big, it may cause the huge plastic deformation even fracture of the component. Obviously, this make machine and structure can't work. The ability of component to resist damage (huge plastic deformation and fracture) under external forces is called strength.
If notable elastic deformation occurs, although it can be restored, but before it be restored, they also cause machine can't work. The ability of component to resist deformation under external forces is called rigidity.
Although no notable deformation occurs, sometimes only the original balance between the components is broken, the machine can not work properly too. The ability of components to keep their original balance under external forces is called stability.
We suppose that there is a kind of material, it never change its shape under external force, this material calls rigid body. Rigid body is not exist in the real world.
The condition can limit the displacement of the object, is called the constraint. Common constraints are flexible cable, support surface, hinge, etc..
Two forces with equal size and opposite direction are not in the same line, are called force couple.
Then we learned how to analyze the force on an object, we learned many methods to analyze force, such as force translation, force decomposition, force synthesis.
3. 关于材料力学，你都学习了哪些知识？ What knowledge have you learned about
Materials mechanics?
When a external force is applied to an object, object produce a corresponding internal force to against it. The density of internal force is called stress, it is used to describe the size of internal force on unit area. The corresponding deformation caused by external force is called strain. When materials in elastic region, the stress and strain are in direct proportion (linear relationship) (Hooke's law), and the ratio of stress and strain is call Elastic modulus.
If the direction of stress and strain are same with external force, they call direct stress(σ) and direct strain(ε). If the direction of stress and strain are vertical with external force, they call tangential stress(τ) and tangential strain(γ).
We learn the internal force, stress and strain of the material under different forces,
such as stretching, compressing, shearing, torsion, bending.
Then we learned a little about Stress analysis, Breaking strength theory, Yield strength theory.
4. 你在“高分子材料研究方法”这门课中都学习了哪些知识？ What did you learn in the
course “Research Methods of Polymeric Materials”?
This curriculum explains several methods for researching polymer’s structure, morphology, properties and molecular motion. Researching methods of polymer can be divided into three types, they are spectral analysis, thermal analysis and microscopic analysis.
5. 关于波谱分析，你都学习了哪些知识？ What knowledge have you learned about
spectral analysis?
We learn two important and commonly used spectral analysis, they are infrared spectroscopy, nuclear magnetic resonance spectroscopy.
When the temperature is above absolute zero, molecules are in continuous motion, motion can be divided into translation, rotation and vibration. The vibrations of molecules need to absorb infrared have the same frequency with the frequency of vibration to obtain energy. Different groups, have different vibration frequencies, also absorb infrared in different frequencies. Using infrared irradiation material, it can be found that there are some infrared in certain frequency have been absorbed by the material. In that way, we can get what groups are there in that material.
In a strong magnetic field, the atomic nucleus of a hydrogen atom nuclear will occur a transition. The transition need to absorb a electromagnetic wave (Hertz wave) in certain frequency to obtain energy. The hydrogen atom in different chemical environment absorb electromagnetic wave in different frequency. Through the measurement of the frequency and number of the electromagnetic wave is absorbed by hydrogen atom, We can know how many different kinds of hydrogen atoms are
there in the molecule of that material, and the proportion of them.
6. 关于热分析，你都学习了哪些知识？ What knowledge have you learned about
thermal analysis?
The most common method of thermal analysis is thermal gravimetric analysis (TG). TG is to put the material on the scale that has the heating function, measure the weight of the material at different temperatures. Through TG we can get the heat resistance of materials.
Another important method of thermal analysis is differential thermal analysis (DTA). DTA can measure material is absorbing heat or releasing heat under a certain temperature. Through that information, we can analyze the state and behavior of material under that temperature.
7. 关于显微分析，你都学习了哪些知识？ What knowledge have you learned about
microscopic analysis?
Teacher mainly introduce us two kinds commonly used microscopic analysis, they are transmission electron microscopy (TEM) and scanning electron microscopy (SEM).
8. 你在“材料工程与工程基础”这门课中都学习了哪些知识？ What did you learn in the
course “Fundamentals of Materials Science and Engineering”?
Materials can be divided into four kinds, they are Metallic materials, Inorganic non-metallic materials, Polymer materials, Composite materials. Materials' development and progress of human civilization are closely linked. \science\concept is proposed in the beginning of the 1960s when the United States developed the satellites and missiles.
One of the core of materials science and engineering is researching the
relationship between materials organization, structure and performance. On the other hand, materials science and engineering also is a practical subject serving the economic construction. Materials Science and Engineering is connected with physics, chemistry, metallurgy, computational mathematics and other subjects. Materials scientists believe that materials science and engineering has five elements, they are composition, structure, preparation, property and using performance.
Properties of materials can be divided into two categories, they are processing performance and using performance. This course introduces some main performances include mechanical properties like: elasticity, plasticity, strength, hardness, toughness, wear resistance, etc; and others like: electrical properties, magnetic properties, thermal properties, corrosion resistance, etc. Different materials have different atomic structure and different bonds between atoms, which is why they have different properties. This course introduces the five major aspects(composition, structure, preparation, property and using performance) of the four categories materials(Metallic materials, Inorganic non-metallic materials, Polymer materials, Composite materials), focus on high-molecular materials. At last, the teacher describes some research of new materials.
9. 你在“特种及功能高分子”这门课中都学习了哪些知识？ What did you learn in the
course “Special and Functional Polymer”?
It introduced several kinds of polymer who have Special functions. In the class teacher did not teach by the text book, because the text book was written years ago, but in this curriculum we should learn something new. The teacher divided us into groups, and gave each group a paper. We work on this paper and make lecture about it in front of all students.
The title of the paper of my group is “A Novel Superhydrophilic and Underwater Superoleophobic Hydrogel-Coated Mesh for Oil/Water Separation” it is written by Tsinghua University and Chinese Academy of Sciences. They use polyacrylamide hydrogel covered a Stainless Steel Wire Mesh, make it only allow
water get through it. I believe This will be widely applied in After-treatment of petroleum leaking out Accident.
APS考试复习资料：材料科学
